Perirhinal Cortex

One view holds that the hippocampus is important for both processes, whereas a different view holds that the hippocampus supports only the recollection process and the perirhinal cortex supports the familiarity process.  

METH exposure resulted in significant enhancements of CB(1) receptor expression across several brain regions, including prefrontal cortex, caudate-putamen, basolateral amygdala, CA1 hippocampal region and perirhinal cortex.  

Examination of critical subreceptors in the seizure controlling perirhinal cortex has revealed that microinfusion of ionotropic glutamatergic antagonists can exert anticonvulsant efficacy against soman-induced seizures. The purpose of the present study was to investigate whether modulators of metabotropic glutamate (mGlu) receptors may ensure anticonvulsant effects when microinfused into the perirhinal cortex. The results suggest that the perirhinal cortex is a likely site of cholinergic recruitment of glutamatergic hyperactivity after exposure to a convulsant dose of soman.  

An active debate in the learning and memory literature centers on the question of whether the perirhinal cortex, part of the medial temporal lobe (MTL), plays its major role in declarative/relational learning and memory or if it also makes an important contribution to high- level perception, similar to the functions of the adjacent visual area TE. Here I consider evidence from neuroanatomical and neurophysiological studies and argue that the perirhinal cortex has distinct and dissociable structure and function from area TE, making its major contribution to declarative/relational learning and memory. I propose additional neurophysiological studies that could help differentiate between these two debated roles of the perirhinal cortex: memory alone or memory plus high- level perception..  

The CA1 to perirhinal cortex projection is one of the multiple hippocampal-neocortical projections considered to be crucially involved in memory consolidation. Following all experiments, tissue samples were taken from area CA1 and perirhinal cortex from both the unstimulated and stimulated hemispheres of each brain and analysed for BDNF. Finally, changes in BDNF were positively correlated with stimulation frequency in the area CA1 but the same pattern was not observed in the perirhinal cortex. These findings suggest that the CA1 to perirhinal cortex projection is electrophysiologically excitatory in nature and that changes in BDNF levels in this projection may not be predictive of changes in synaptic plasticity..  

The current study examined the role of the perirhinal cortex in retrieving familiar object-place paired associates, as well as in acquiring novel ones. Excitotoxic lesions of the perirhinal cortex initially impaired the normal retrieval of object-place paired-associative memories that had been learned presurgically, but the animals relearned gradually to the level of controls. The results suggest that the perirhinal cortex is indispensable to forming discrete representations for object-place paired associates.  

Recent evidence suggests that the perirhinal cortex is involved in perception of complex objects with ambiguous features. Anterior regions of the temporal lobes, including the perirhinal cortex as well as lateral cortex, are also thought to play a critical role in semantic memory. To understand how semantic factors might contribute to perceptual discrimination of complex objects, we studied visual object discrimination in patients with semantic dementia (SD)-a neurodegenerative condition characterized by progressive deterioration of semantic knowledge and atrophy to anterior temporal lobes (including perirhinal cortex). Stimulus meaningfulness, however, differentially influenced performance in SD patients compared with MTL amnesics, suggesting that perceptual representations of complex objects (dependent upon perirhinal cortex) interact with higher-order abstract conceptual representations, even for tasks with no overt semantic component..  

Rats with perirhinal cortex lesions were sequentially trained in a rectangular water tank on a series of 3 visual discriminations, each between mirror-imaged stimuli. There was no evidence that lesions of the perirhinal cortex disrupted the ability to learn the concurrent configural discrimination task, which required the rats to learn the precise combination of stimulus identity with stimulus placement ("structural" learning). The same rats with perirhinal cortex lesions were also unimpaired on a test of spatial working memory (reinforced T maze alternation), although they were markedly impaired on a new test of spontaneous object recognition. On the basis of their differential exploration times, rats with perirhinal cortex lesions showed very poor discrimination of the novel objects, thereby confirming the effectiveness of the surgery. The discovery that bilateral lesions of the perirhinal cortex can leave configural (structural) learning seemingly unaffected points to a need to refine those models of perirhinal cortex function that emphasize its role in representing conjunctions of stimulus features..  

First, research with monkeys and rats reveals that the contributions of medial temporal lobe structures such as the hippocampus and perirhinal cortex to memory processes are dissociable, with particular structures contributing to specific tasks on the basis of the specific type of information that a structure is optimized to process.  

The hippocampus and perirhinal cortex have been linked to both elemental and configural processes. Here, we assessed the role of the rat hippocampus and perirhinal cortex in these distinct ways of processing patterns of sensory stimulation involving auditory, visual context and temporal information. Using selective lesions and inactivation techniques we identified a specific role for the hippocampus in the retrieval of configural memories but not of those that could be encoded elementally; we also identified a role for the rat perirhinal cortex in visual contextual learning.  

We assume that, due to the absence of connections between lateral and medial areas of the entorhinal cortex, object-place associations are mostly formed in the hippocampus, but can also be generated in the perirhinal cortex due to existence of input from the postrhinal cortex.  

The results showed that successful retrieval of a source with high confidence was associated with increased activity in the hippocampus and that correct item recognition with failed source retrieval and low confidence for a source (i.e., item-only hits) was associated with decreased activity in the perirhinal cortex. The results also support existing models suggesting that the hippocampus is associated with recollection-based recognition and the perirhinal cortex with familiarity-based recognition, with the possibility that the hippocampus plays roles in both recognition processes..  

MTA scores were obtained from visual ratings of the hippocampus, entorhinal cortex, and perirhinal cortex on coronal magnetic resonance imaging scans using a magnetization-prepared rapid gradient echo protocol.  

Increased c-Fos activity was found in caudal but not rostral portions of the perirhinal cortex (areas 35/36) and in area Te2 in rats showing object recognition, i.e. Additional analyses of the c-Fos data using structural equation modelling indicated the presence of pathways starting in the caudal perirhinal cortex that display a direction of effects from the entorhinal cortex to the CA1 field (temporo-ammonic) when presented with familiar objects, but switch to the engagement of the direct entorhinal cortex pathway to the dentate gyrus (perforant) with novel object discrimination.  

The role of brain-derived neurotrophic factor (BDNF) in recognition memory was investigated by locally infusing oligodeoxynucleotides (ODNs) into perirhinal cortex, a region of the temporal lobe essential for familiarity discrimination.  

Studies in rats and non-human primates suggest that medial temporal lobe (MTL) structures play a role in perceptual processing, with the hippocampus necessary for spatial discrimination, and the perirhinal cortex for object discrimination.  

In rats examined 28 and 54 weeks after irradiation, L-158,809 treatment did not alter the effects of radiation on the number and activation of microglia in the perirhinal cortex and hippocampus, nor did it prevent the radiation-induced decrease in proliferating cells and immature neurons in the hippocampus.  

Rats that exercised prior to binge alcohol consumption had reduced loss of dentate gyrus granule cells and fewer FluoroJade B positive cells in the dentate gyrus and associated entorhinal-perirhinal cortex compared to nonexercisers.  

We review findings of selective ablation studies which demonstrate that the perirhinal cortex, hippocampus and medial prefrontal cortex are differently involved in recognition memory processes involving these different types of information. This review also presents data from a series of disconnection analyses, which test whether the perirhinal cortex, hippocampus and medial prefrontal cortex form components of an integrated system for these recognition memory processes. These analyses reveal that it is necessary for the perirhinal cortex, medial prefrontal cortex and the hippocampus to interact, forming an integrated network, in recognition memory involving judgment of whether an object has been previously encountered in a particular place (object-in-place recognition memory) and in judging which of two objects was encountered longer ago (temporal order memory).  

In 3 habituation experiments, rats with excitotoxic lesions of the perirhinal cortex were found to be indistinguishable from control rats. Implications for comparator theories of habituation are considered, and it is concluded that others' demonstrations of the sensitivity of object recognition to perirhinal cortex damage is not the result of standard habituation..  

The massive transfer of information from the neocortex to the entorhinal cortex (and vice versa) is hindered by a powerful inhibitory control generated in the perirhinal cortex. The pharmacological inactivation of GABAergic transmission by local application of bicuculline (1 mM) in area 36 of the perirhinal cortex facilitated the longitudinal (rostrocaudal) propagation of activity into the perirhinal/postrhinal cortices but did not cause propagation into the entorhinal cortex.  

The organization of visual object representations: A connectionist model of effects of lesions in perirhinal cortex.  

Activity in perirhinal cortex (PRC) and a hippocampal subfield comprising the dentate gyrus and CA fields 2 and 3 (CA23/DG) reflected successful encoding only when items were recollected consistently across both delays.  

Here we examined the laminar distribution of three CaBPs in rat perirhinal cortex (PR) as a function of aging.  

The activated brain areas of memory retrieval mainly locate in the prefrontal lobe, the temporal lobe, the entorhinal cortex, the perirhinal cortex, the posterior hippocampus, the thalamus, and the basal ganglia.  

In rodents, AC-260584 activated extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation in the hippocampus, prefrontal cortex and perirhinal cortex.  

In the present study, a number of drugs with anticonvulsant potency were microinfused into the perirhinal cortex (PRC) or posterior piriform cortex (PPC) in rats.  

The perirhinal cortex (PRh) has been strongly implicated in object recognition memory and visual stimulus representation.  

Moreover, a region of left hippocampus/perirhinal cortex appeared to be driven by event vividness.  

Functional magnetic resonance imaging revealed significant delay period activity in anterior hippocampus, entorhinal cortex, and perirhinal cortex over the 30 s retention interval, with the magnitude of activity being significantly higher on subsequently correct compared with subsequently incorrect trials.  

The performance of rats in a preferential object recognition test was examined after local infusion of the CAMKII inhibitors KN-62 or autocamtide-2-related inhibitory peptide (AIP) into the perirhinal cortex. At 70 min, processing novel images resulted in more phospho-CAMKII(Thre286)alpha-stained neurons in the perirhinal cortex than did the processing of familiar images, consistent with the viewing of novel images increasing the activity of CAMKII at this time.  

For instance, one view is that perirhinal cortex (PRc) processes item information, parahippocampal cortex (PHc) processes context information, and the hippocampus binds item and context.  

They did not occur in layers 1-3, perirhinal cortex, subiculum or dentate gyrus during this period.  

CONCLUSIONS: Volatile agent preconditioning partially protects perirhinal cortex and striatal dependent functions against moderate to severe neonatal hypoxia-ischemia..  

GSK189254 (0.3 mg/kg) was without effect on polysialylated cell frequency in the entorhinal and perirhinal cortex, but significantly increased the diffuse PSA staining observed in the anterior, ventromedial, and dorsomedial aspects of the hypothalamus.  

The perirhinal cortex of the temporal lobe is essential for the familiarity discrimination component of recognition memory. Single doses of three different types of L-type VDCC antagonists, verapamil, diltiazem, and nifedipine, administered systemically, or verapamil administered locally into the perirhinal cortex, impaired acquisition of long-term (24 h) but not shorter-term (20 min) recognition memory. L-type VDCC antagonism by verapamil in perirhinal cortex during memory acquisition disrupted the normal pattern of differential Fos expression, so paralleling the antagonist-induced memory impairment. In slices of perirhinal cortex maintained in vitro, verapamil was without effect on baseline excitability or LTP but blocked LTD and depotentiation.  

After chronic ECS, upregulation of both NGF and TrkA was found in perirhinal cortex, thalamus, and amygdala.  

Recent evidence challenges this position, suggesting that perirhinal cortex (PRc) in the MTL may also play a role in perceptual discriminations of stimuli with substantial visual feature overlap.  

A previous study from this laboratory showed that this movement-related firing property is disrupted by lesions of the perirhinal cortex (PrhC).  

Aged heterozygous Rolling Nagoya mice carrying Cav2.1alpha1 mutation show deficits with regard to spatial short-term memory using hippocampus-related object location test, but not with regard to nonspatial memory using perirhinal cortex-related object recognition test. In perirhinal cortex, there were no significantly different expressions.  

Each monkey received either selective cholinergic depletion of inferotemporal cortex (including the entorhinal cortex and perirhinal cortex) with injections of the immunotoxin ME20.4-saporin or saline injections as a control and was postoperatively retested.  

These behavioral changes were accompanied by increased expression of BDNF protein in the dentate gyrus, hippocampus, and perirhinal cortex.  

Concurrently, old words elicited less neural activity in bilateral perirhinal cortex. These findings have implications for considering how perirhinal cortex may contribute to different neurocognitive functions, possibly including both implicit memory and familiarity-based recognition. This study documents the first evidence linking behavioral measures of priming to information processing in perirhinal cortex..  

By virtue of its widespread afferent projections, perirhinal cortex is thought to bind polymodal information into abstract object-level representations. Our results demonstrate that the human perirhinal cortex is involved in cross-modal, visual-tactile, integration and, thus, indicate a functional homology between human and monkey perirhinal cortices..  

The trace group also exhibited more increases lateralized to the right hemisphere, opposite to the side of US delivery, in various areas including: CA1, subiculum, presubiculum, perirhinal cortex, ventral and dorsal MGN, and the basolateral and central amygdala.  

In particular, studies have suggested that the perirhinal cortex is more involved in object processing than spatial processing, while other regions such as the parahippocampal cortex have been implicated in spatial processing. A region of interest analysis showed that object encoding evoked stronger activation than position encoding in bilateral perirhinal cortex, temporopolar cortex, parahippocampal cortex, hippocampus and amygdala.  

According to one hypothesis, this transient CS representation is supported by endogenous activity in "persistent-firing" neurons of perirhinal cortex (PR).  

It is argued here that the perirhinal cortex is a key node in a more extensive network mediating protosemantic associative memory.  

The CA1 to perirhinal cortex projection is one of multiple hippocampal-neocortical projections considered to be involved in memory consolidation. A stimulating electrode was inserted into the area CA1 and a recording electrode was inserted into the perirhinal cortex of urethane-anaesthetised Wistar rats. CA1 and perirhinal cortex tissue samples were taken from the stimulated and unstimulated hemispheres of each rat brain and analysed using a brain-derived neurotrophic factor (BDNF) ELISA. This molecular and electrophysiological data suggests that LTP in the CA1-perirhinal cortex projection may require activation of postsynaptic AMPA/kainate receptors in order to sustain LTP..  

However, similar percentages of voxels were sensitive to novel faces and scenes in perirhinal cortex, entorhinal cortex, and a combined region comprising the dentate gyrus, CA(2), and CA(3), whereas parahippocampal cortex, CA(1), and subiculum demonstrated greater sensitivity to novel scene stimuli. Paralleling these findings, subsequent memory effects in perirhinal cortex were observed for both faces and scenes, with the magnitude of encoding activation being related to later memory strength, as indexed by a graded response tracking recognition confidence, whereas subsequent memory effects were scene-selective in parahippocampal cortex.  

How does the brain bind together the different sensory features of objects to form meaningful, multimodal object representations? Human functional imaging findings implicate the left posterior superior temporal sulcus/middle temporal gyrus (pSTS/MTG) in crossmodal integration, while animal ablation findings support a hierarchical object processing model in which outputs from each sensory stream are integrated in perirhinal cortex (PRc) of the anteromedial temporal lobe.  

Because volumetric MRI requires rigorous standards for image acquisition and analysis and is not suitable for routine clinical use, we have used calibrated visual rating to measure atrophy in the ERC, HPC, and perirhinal cortex (PRC) and evaluated its utility in the diagnosis of very early AD.  

Damage to rat perirhinal cortex (PR) profoundly impairs fear conditioning to 22kHz ultrasonic vocalizations (USVs), but has no effect on fear conditioning to continuous tones.  

Last, activity in a different group of regions (perirhinal cortex, parahippocampal cortex, and inferior temporal gyrus) was associated with how well the test questions were subsequently remembered.  

The present study examines 2 factors that might moderate the object-recognition deficit seen after perirhinal cortex damage. In contrast, rats with perirhinal cortex lesions failed to benefit from increased close exploration and did not discriminate the novel object after even the longest sample period. The second factor was extent of perirhinal cortex damage. A significant correlation was found between total perirhinal cortex loss and degree of recognition impairment. Within the perirhinal cortex, only damage to the caudal perirhinal cortex correlated significantly with recognition memory deficits. This study highlights the critical importance of the perirhinal cortex within the temporal lobe for recognition memory and shows that the lesion-induced deficit occurs despite seemingly normal levels of close object exploration..  

Electrophysiological work has dissociated match and mismatch signals in the monkey perirhinal cortex, where match signals were selective for matches to goal states, whereas mismatch signals were not modulated by intention (Miller and Desimone, 1994).  

In synapses in the perirhinal cortex, we have directly compared the Ca(2+) signaling mechanisms involved in NMDAR-LTD and mGluR-LTD.  

Environmental novelty, but not environmental complexity, led to a selective increase of Fos induction in the final "output" subregion of the dorsal hippocampal trisynaptic circuit (CA1) and a primary projection site (layer five of the lateral entorhinal cortex, ERC), as well as in the perirhinal cortex. Whether novelty-dependent Fos induction in perirhinal cortex depends on this hippocampal output or reflects an independent process remains to be determined..  

It has been suggested that the MTLC contains functionally distinct regions, with perirhinal cortex (PRc) preferentially supporting object processing and posterior parahippocampal cortex (PHc) preferentially supporting encoding of spatial information.  

The present study was designed to determine the degree of functional dissociation between the rat perirhinal cortex and hippocampus for reference memory performance on object and place discrimination tasks. Rats with a perirhinal cortex lesion needed significantly more days to attain the criterion in the relearning of a pre-operatively acquired object discrimination task than the control rats and rats with a hippocampal lesion. Rats with a perirhinal cortex lesion, on the other hand, showed mild relearning impairment. These results suggest that there is a functionally single dissociation between the perirhinal cortex and hippocampus for reference memory performance on object and place discrimination tasks. They also suggest the possible involvement of the perirhinal cortex in spatial reference memory performance..  

In the present report, we assessed the participation of perirhinal cortex (Ph), dorsal hippocampus (Hipp), basolateral (BLA) and central nuclei of the amygdala (CeA) in safe and aversive taste memories by means of local infusions of the protein synthesis inhibitor anisomycin in the rat.  

There was increased acetylcholinesterase activity in hippocampus and perirhinal cortex of the deprived animals.  

In contrast to the previously reported effects of lesions of neighboring perirhinal cortex, however, there was no effect of postrhinal lesions on the location stability of the fields over time or in the response of these cells to the animal's movement.  

Strong evidence suggests that the macaque monkey perirhinal cortex is involved in both the initial formation as well as the long-term storage of associative memory. We also compared the associative learning signals in the perirhinal cortex to our previous findings in the hippocampus. Taken together, these findings emphasize the important role of the perirhinal cortex in new associative learning and suggest that the perirhinal cortex together with the hippocampus contribute importantly to conditional-motor associative memory formation..  

DMI challenge in chronic DMI-treated neuropathic rats produced significantly greater activation of the deep mesencephalic nucleus, primary somatosensory cortex, insular cortex, medial globus pallidus, inferior colliculus, perirhinal cortex and cerebellum compared to sham-operated rats and saline controls.  

Functional magnetic resonance imaging studies of recognition memory have often been interpreted to mean that the hippocampus supports recollection and that the adjacent perirhinal cortex supports familiarity. First, we identified regions in both hippocampus and perirhinal cortex in which activity varied as a function of subsequent item memory strength while source memory strength was held constant at chance levels.  

The present study examined the role of the rostral perirhinal cortex (rPRh) in behavioral changes following electrical foot shock-induced stress.  

Although a manipulation of visual feature similarity did not influence naming latencies, we observed perfusion increases in the perirhinal cortex for naming objects with similar visual features that interacted with the semantic context in which objects were named.  

In the perirhinal cortex, increased activity predicts subsequent recognition, whether based on weak or strong memory, whereas during retrieval activity decreases below the level for misses in association with both weak and strong memory.  

Results from imaging and lesion studies of item recognition memory have suggested that the hippocampus supports memory for the arbitrary associations that form the basis of episodic recollection, whereas the perirhinal cortex (PRc) supports familiarity for individual items.  

In contrast, activity in both hippocampus and perirhinal cortex positively correlated with the subsequent memory strength of remembered items.  

METHODS: 23 patients with (AD and 23 sex, age, and educational background-matched normal controls (NC group) underwent three-dimensional MRI to measure the hippocampus, amygdala, entorhinal cortex (EC), perirhinal cortex (PC), cornu temporale, and uncus distance in the baseline survey. RESULTS: The baseline survey showed that the levels of uncus distance and total temporal horn volume of the ADS patients were 11 +/- 4 and 1.21 +/- 1.00 respectively, both significantly higher than those of the NC group (7 +/- 3 and 0.59 +/- 0.54 respectively, P < 0.01, P < 0.05), and the levels of total entorhinal cortex volume, total perirhinal cortex volume, and total hippocampus volume were 2.52 +/- 0.86, 2.19 +/- 0.62, and 3.23 +/- 0.75 respectively, all significantly lower than those of the BC group (3.67 +/- 0.54, 3.39 +/- 0.51, and 3.98 0.38, all P < 0.01). The levels of uncus distance and total temporal horn volume of the AD patients during the follow-up survey were 11 +/- 4 and 1.21 +/- 1.00 respectively, both significantly higher than those of the NC group (7 +/- 3 and 0.59 +/- 0.54 respectively, both P < 0.05); and the total entorhinal cortex volume, total perirhinal cortex volume, and total hippocampus volume of the AD patients during the followup survey were. CONCLUSION: The AD patients have more remarkable atrophy of entorhinal cortex, perirhinal cortex, and have obvious extension of cornu temporale and uncus distance in comparison with the normal controls.  

Anisomycin, a protein synthesis inhibitor, was infused into the hippocampus, perirhinal cortex, insular cortex, or basolateral amygdala of rats immediately after the sample phase of object or object-in-context recognition memory training. Anisomycin infused into the hippocampus blocked long-term, but not short-term object-in-context recognition memory, whereas infusions administered into the perirhinal cortex, insular cortex, or amygdala did not affect object-in-context recognition memory.  

The anterior MTL including the perirhinal cortex was only engaged during item memory retrieval by an activity decrease. The anterior MTL including perirhinal cortex seems to be particularly engaged in familiarity-based item recognition.  

Here, using a reference spatial memory task in the radial maze, we show that neurotoxic perirhinal cortex lesions produce a profound retrograde amnesia when learning-surgery intervals of 1 or 50 d are used (Experiment 1). These findings demonstrate the differential contribution of various regions of the medial temporal lobe to memory, suggesting that the perirhinal cortex plays a key role in the retrieval of spatial information for a long period of time..  

The hippocampus is well-known to be critical for trace fear conditioning, but nothing is known about the importance of perirhinal cortex (PR), which has reciprocal connections with hippocampus.  

The LCBF increase in the somatosensory cortex, ventrobasal and anterior thalamic nuclei, hypothalamus, subthalamic nucleus, piriform, entorhinal and perirhinal cortex, amygdala, CA2 region of hippocampus, and substantia nigra was statistically significantly larger in stimulated GAERS compared to stimulated NEC rats.  

We have exploited the involvement of the perirhinal cortex in two different forms of learning to compare simultaneously, within the same brain region, their effects on LTD and depotentiation. Multiple-exposure learning but not single-exposure learning in vivo prevented, in a muscarinic receptor-dependent manner, subsequent induction of LTD and depotentiation, but not LTP, in perirhinal cortex in vitro.  

The spermine level was significantly decreased in the perirhinal cortex and increased in the postrhinal cortex with age.  

Data from recognition memory studies have provided evidence that the hippocampus supports relational encoding important for later episodic recollection, whereas the perirhinal cortex has been linked with encoding that supports later item familiarity. However, extant data also strongly implicate the perirhinal cortex in object processing and encoding, suggesting that perirhinal processes may contribute to later episodic recollection of object source details. In contrast to studies reporting a link between perirhinal cortex and item familiarity, it was found that encoding activation in the right perirhinal cortex correlates with successful recollection of the paired object.  

However, recent neuroimaging results have suggested that the perirhinal cortex, a region thought to support familiarity-based item recognition, may support source attributions if source information is encoded as a feature of the relevant item (i.e., "unitized").  

Familiarity is mediated by the mediodorsal (MD) thalamic nucleus and the entorhinal/perirhinal cortex.  

In the present study, anticonvulsant efficacy against soman intoxication (1.3 x LD50) was examined in rats with either lesion of the perirhinal cortex, posterior piriform cortex, entorhinal cortex, hippocampal region, or amygdala.  

Compared to the sham and control cage groups, rats exposed to a GSM signal at 6 W/Kg showed decreased CO activity in some areas of the prefrontal and frontal cortex (infralimbic cortex, prelimbic cortex, primary motor cortex, secondary motor cortex, anterior cingulate cortex areas 1 and 2 (Cg1 and Cg2)), the septum (dorsal and ventral parts of the lateral septal nucleus), the hippocampus (dorsal field CA1, CA2 and CA3 of the hippocampus and dental gyrus) and the posterior cortex (retrosplenial agranular cortex, primary and secondary visual cortex, perirhinal cortex and lateral entorhinal cortex).  

The present review considers some of this recent research, with an emphasis on studies addressing the neural bases of perirhinal cortex-dependent object recognition memory processes. The results of these studies overwhelmingly favor the view that perirhinal cortex (PRh) is a critical region for object recognition memory.  

It has also been suggested that the perirhinal cortex plays an essential role in visual recognition memory. In the MTL region, we observed monotonic decreases in activity across trials in the parahippocampal cortex as well as the anterior perirhinal cortex. We also observed monotonic increases in activity in the posterior perirhinal cortex with increasing memory strength.  

We measured cortical thickness and volume in MTL subregions (hippocampal CA fields 1, 2 and 3; dentate gyrus; entorhinal cortex; subiculum; perirhinal cortex; parahippocampal cortex; and fusiform gyrus) using a high-resolution in-plane (0.4x0.4 mm) MRI sequence in 30 cognitively normal volunteers (14 APOE-4 carriers, 16 non-carriers, mean age 57 years). APOE-4 carriers had reduced cortical thickness compared with non-carriers in entorhinal cortex (ERC) and the subiculum (Sub), but not in the main hippocampal body or perirhinal cortex.  

Here, we look for a possible mechanism by contrasting memory effects in two architectonically different parts of ITC: area TE and the perirhinal cortex. Neurons in perirhinal cortex did not show this correlation.  

RESULTS: Atrophy in the anterior hippocampus, the ento- and perirhinal cortex as well as the parahippocampal gyrus, middle temporal gyrus and anterior cingulate cortex correlated closely with episodic memory performance.  

In contrast, neither the hippocampus nor perirhinal cortex (PRc) were found to be selective for category information.  

Number of hippocampal pyramidal cells and the trkB-mRNA expressions in the amygdala, perirhinal cortex, thalamus, and the hippocampal CA1, CA3, and CA4 areas, were evaluated using molecular biological techniques.  

In perirhinal cortex, a lasting decrement in neuronal responsiveness is associated with visual familiarity discrimination, leading to the hypothesis that long-term depression (LTD)-like synaptic plasticity may underlie recognition memory. We demonstrate that a peptide that blocks interactions between GluR2 and AP2 blocks LTD in perirhinal cortex in vitro. Viral transduction of this peptide in perirhinal cortex produced striking deficits in visual recognition memory. Furthermore, there was a deficit of LTD in perirhinal cortex slices from virally transduced, recognition memory-deficient animals. These results suggest that internalization of AMPA receptors, a process critical for the expression of LTD in perirhinal cortex, underlies visual recognition memory..  

Our ability to recognize that something is familiar, often referred to as visual recognition memory, has been correlated with a reduction in neural activity in the perirhinal cortex.  

The perirhinal cortex (area 35) is well-known locus for neurofibrillary tangles (NFT) in initial Alzheimer's disease (AD) and fully developed AD and may contain tau alterations in non-demented elderly. Ventromedial temporal pathology as revealed by AT8 suggests the presence of a relatively large lesion early in AD involving all of the perirhinal cortex and other non-isocortical areas.  

In trauma subjects, listening to trauma scripts versus neutral scripts resulted in decreased flow in the right amygdala and left amygdala/perirhinal cortex, and symptom scores correlated negatively with right hippocampal flow changes. Symptom improvement at 3 months correlated negatively with rCBF changes in right perirhinal cortex and hippocampus during the trauma versus neutral script contrast. CONCLUSIONS: In recently traumatized subjects functional interactions between the amygdala, perirhinal cortex and ACC/mPFC that occur during exposure to traumatic reminders may underlie adaptive/recuperative processes..  

The perirhinal cortex is involved not only in object recognition and novelty detection but also in multimodal integration, reward association, and visual working memory. We propose a computational model that focuses on the role of the perirhinal cortex in working memory, particularly with respect to sustained activities and memory retrieval. Dopamine leads to sustained activities after stimulus disappearance that form the basis of the involvement of the perirhinal cortex in visual working memory processes. Thus, we suggest that areas involved in planning and memory coordination encode a pointer to access the detailed information encoded in the associative cortex such as the perirhinal cortex..  

In the rat, a number of sensory modalities converge in the perirhinal cortex (PC). The neural pathway from the perirhinal cortex to the entorhinal cortex (EC) is considered one of the main routes into the entorhinal-hippocampal network.  

The representation of simultaneously presented configural stimuli depends on the perirhinal cortex.  

Paired helical filament 1-immunoreactive pretangles and tangles were observed as early as the third decade prior to their appearance in entorhinal/perirhinal cortex; they were increased in mild and severe AD.  

There was no effect on 5-HT or DA in the entorhinal and perirhinal cortex.  

In summary, whole-brain regional evaluation in SD, in comparison with normal controls and FTD-MND, found anterior temporal atrophy encompassing the perirhinal cortex with relative sparing of adjacent posterior temporal regions..  

The perirhinal cortex (PER) is part of both the medial temporal lobe memory system (MTL) and the ventral visual stream (VVS).  

In the present experiments, the effects of amygdaloid kindling were assessed on a battery of behavioral tests we used previously to assess the effects of kindling in dorsal hippocampus or perirhinal cortex.  

While 50-kHz playback induced sparse fos-like immunoreactivity in frontal association cortex, nucleus accumbens, thalamic parafascicular and paraventricular nuclei, 22-kHz playback elicited c-fos expression in the perirhinal cortex, amygdalar nuclei and the periaqueductal gray.  

These data support the hypothesis of a specific role of the hippocampus in recollection processes and suggest that other components of the MTL (e.g., perirhinal cortex) may be more involved in the process of familiarity..  

The perirhinal cortex (PrC) has been hypothesized to support nonassociative item encoding that contributes to later familiarity, whereas the hippocampus supports associative encoding that selectively contributes to later recollection.  

However, activation in other brain regions, including the precuneus, lateral prefrontal cortex, parietal cortex, lateral temporal lobe, and perirhinal cortex increased after multiple retrievals, but was not influenced by the passage of time.  

In this study, seizure activity associated with the four-vessel occlusion model of cerebral ischemia was monitored using chronically implanted electrodes in the CA1/subicular region, the perirhinal cortex, and the prefrontal cortex of the rat.  

Afferents from the perirhinal cortex (PRh) form a major input to the hippocampal formation, which is known to be involved in sexual behavior in rodents.  

Monkeys with aspiration lesions of the perirhinal cortex were also included in this study as an operated control group. CONCLUSIONS: These findings dissociate the hippocampus and perirhinal cortex in fear expression and specifically implicate the hippocampal formation in generating responses to stimuli that are potentially threatening..  

The human perirhinal cortex is thought to be critically involved in non-relational memory, but another view postulates hippocampal involvement in both relational and non-relational memory.  

Encoding phase activation in anterior and posterior regions of the left hippocampus, and in bilateral perirhinal cortex, predicted subsequent accuracy on the short-term memory decision, as did bilateral posterior hippocampal activity after the test stimulus.  

The perirhinal cortex (PRh) has a well-established role in object recognition memory.  

The orbital network is also connected with taste and olfactory cortical areas and the perirhinal cortex and appears to be involved in assessment of sensory objects, especially food.  

Continuous arterial spin labeling MRI measuring blood perfusion (as an indirect measure of activity) reveals that aripiprazole dose-dependently decreased brain activity in the entorhinal piriform cortex, perirhinal cortex, nucleus accumbens shell, and basolateral amygdala.  

Although item memory was not associated with unique MTL activity at our original threshold, a region-of-interest (ROI) analysis revealed item-memory-related activity in the perirhinal cortex.  

Consistent with previous findings for neutral words, hippocampal activation predicted later relational memory, whereas activation in the perirhinal cortex predicted successful item recognition.  

Pretraining lesions of rat perirhinal cortex (PR) severely impair pavlovian fear conditioning to a 22 kHz ultrasonic vocalization (USV) cue.  

Of the cell bodies in the cortical areas, about 4.4% were located in the orbital, 11.1% in the infralimbic medial prefrontal (areas DPC, IL), 18.2% in the cingulate (3.2% in CG1, 2.9% in CG2, 12.1% in CG3), 9.5% in the frontal association (area Fr2), 12.0% in the insular (areas AI, DI), 10.8% in the retrosplenial, and 34.0% in the perirhinal cortex.  

Recognition memory is widely viewed as consisting of two components, recollection and familiarity, which have been proposed to be dependent on the hippocampus and the adjacent perirhinal cortex, respectively. A review of work with humans, monkeys and rodents finds evidence for familiarity signals (as well as recollection signals) in the hippocampus and recollection signals (as well as familiarity signals) in the perirhinal cortex.  

Slices from control rats (n=8) displayed SLEs in the entorhinal and perirhinal cortex upon application of 50 or 100 microM 4-AP. Real-time PCR revealed no significant downregulation of Kv1.4, Kv1.5, Kv3.1 or Kv3.2 in the subiculum, entorhinal and perirhinal cortex from chronic epileptic rats compared to controls.  

In addition, a decrease of signal changes in the perirhinal cortex was observed for the familiarity versus correct rejection contrasts. They also indicate a lasting hippocampal involvement in the recollection component of recognition memory and a decrease of perirhinal cortex activation associated with familiarity for time periods up to 6 weeks after new learning..  

Golgi-impregnated neurons from rat perirhinal cortex (PR) were classified into one of 15 distinct morphological categories (N = 6,891).  

To clarify the specific contribution of the medial temporal lobe structures in spatial memory, we tested monkeys (Macaca mulatta) with sham operations and with lesions of either the hippocampal formation, areas TH/TF or perirhinal cortex on two versions of the visual-paired comparison task, measuring Spatial Location, and Object-in-Place associations. The data showed that the hippocampal formation, areas TH/TF, and perirhinal cortex appear to contribute interactively to object and spatial memory processes..  

At present, it remains controversial whether lower structures in this hierarchy, such as perirhinal cortex, support memory functions that are distinct from those of higher structures, in particular the hippocampus. perirhinal cortex has been proposed to play a specific role in the assessment of familiarity during recognition, which can be distinguished from the selective contributions of the hippocampus to the recollection of episodic detail. Her resection included a large portion of perirhinal cortex but spared the hippocampus.  

Consistent with previous findings on item memory, perirhinal cortex activated most strongly during landmark retrieval compared with spatial or temporal source information retrieval.  

The orbitofrontal cortex is strongly connected with limbic areas of the medial temporal lobe that are critically involved in the establishment of declarative memories (entorhinal and perirhinal cortex and the hippocampal region) as well as the amygdala and the hypothalamus that are involved in emotional and motivational states.  

In a previous study, we reported apparently paradoxical facilitation of object recognition memory following infusions of the cholinergic muscarinic receptor antagonist scopolamine into the perirhinal cortex (PRh) of rats.  

Damage to the perirhinal cortex (PRh) in rats impairs anterograde object-recognition memory after retention intervals of up to several hours, but there is little direct evidence to link PRh function to object-recognition abilities after substantially longer intervals that span several days or weeks.  

perirhinal cortex (anterior MTL) and parahippocampal cortex (posterior MTL) have distinct connectivity patterns with sensory neocortex, suggesting a possible modality-dependent organization of memory processes.  

Medial temporal lobe (MTL) structures including the hippocampus, entorhinal cortex, and perirhinal cortex are thought to be part of a unitary system dedicated to memory [ 1, 2], although recent studies suggest that at least one component-perirhinal cortex-might also contribute to perceptual processing [ 3, 4, 5, 6]. The results demonstrate a specific role for the perirhinal cortex in visual perception and establish a functional homology for perirhinal cortex between species, although we propose that in humans, the region contributes to a wider behavioral repertoire including mnemonic, perceptual, and linguistic processes..  

The relative decrease in grey matter was most prominent in the left perirhinal cortex. Thus, in homosexual women, the perirhinal cortex grey matter displayed a more male-like structural pattern.  

By contrast, perirhinal cortex (located in the anterior parahippocampal gyrus) supports familiarity by encoding and retrieving specific item information.  

The ventral cochlear nucleus, medial geniculate, CA1 hippocampus, and perirhinal cortex showed modified metabolic capacity due to latent inhibition. There was also a reduced influence on the accumbens from the perirhinal cortex in both latent inhibition and extinction. The results suggest a specific network with a neural mechanism of latent inhibition that appears to involve sensory gating, as evidenced by modifications in metabolic capacity and effective connectivity between auditory regions and reduced perirhinal cortex influence on the accumbens..  

The orbital network receives several sensory inputs, from olfactory cortex, taste cortex, somatic sensory association cortex, and visual association cortex, and is connected with multisensory areas in the ventrolateral prefrontal cortex and perirhinal cortex.  

Within the MTL, both perirhinal cortex and the hippocampus have been implicated. Images of objects with a large degree of feature overlap served as stimuli; they were selected to ensure an involvement of perirhinal cortex in the present recognition task, based on evidence from past lesion-based research. We found that both perirhinal cortex and occipito-temporal cortex showed a differential old-new response that reflected a repetition-related decrease in activity (i.e., new > old). Whereas in perirhinal cortex this decrease was observed with respect to whether subjects reported objects to be old or new, irrespective of the true item status, in occipito-temporal cortex it occurred in relation to whether objects were truly old or new, irrespective of the participants' conscious reports. Hippocampal responses differed in their exact pattern from those of perirhinal cortex, but were also related to the conscious recognition reports.  

There has been considerable debate as to whether structures in the medial temporal lobe (MTL) support both memory and perception, in particular whether the perirhinal cortex may be involved in the perceptual discrimination of complex objects with a large number of overlapping features. To address this issue, a series of trial-unique object "oddity" tasks, in which subjects selected the odd stimulus from a visual array, were administered to amnesic patients with either selective bilateral damage to the hippocampus or more extensive damage to MTL regions, including the perirhinal cortex. These results are consistent with a theoretical view which holds that rostral inferotemporal cortical regions, including perirhinal cortex, represent the complex conjunctions of stimulus features necessary for both perception and memory of objects..  

The perirhinal cortex (PRC) is a supra-modal cortical area that collects and integrates information originating from uni- and multi-modal neocortical regions, transmits it to the hippocampus, and receives a feedback from the hippocampus itself.  

An ED mAMPH regimen attenuated the acute hyperthermic response to the subsequent mAMPH binge and prevented the OR impairments and reductions in [ 125 I]RTI-55 binding to monoamine transporters in striatum, hippocampus (HC), and perirhinal cortex (pRh) that otherwise occur 1 week after the mAMPH binge.  

Specifically, we examined pyramidal neurons of perirhinal cortex areas 36 and 35 (layers II and V); neurons of superficial and deep layers of medial entorhinal cortex (mEC); dentate gyrus (DG) granule cells; and pyramidal cells of the CA3 and CA1 hippocampal fields.  

Impairments in visual discrimination beyond long-term declarative memory have been found in amnesic individuals, with hippocampal lesions resulting in deficits in scene discrimination and perirhinal cortex damage affecting object discrimination. This change was significant in all areas, with the exception of the perirhinal cortex, right anterior hippocampus, and to a lesser extent the left anterior hippocampus during face oddity judgment. Thus, the perirhinal cortex, and possibly anterior hippocampus, may play a more generic role in the discrimination and processing of objects..  

As has been previously described, the cortical afferents of the rodent postrhinal cortex are dominated by structures known to be involved in the processing of visual and spatial information, whereas the cortical afferents of the perirhinal cortex result in remarkable convergence of polymodal sensory information. The perirhinal cortex projects more strongly to piriform, frontal, and insular regions, whereas the postrhinal cortex projects preferentially to visual and visuospatial regions. For example, the perirhinal cortex has strong reciprocal connections with the amygdala, which suggest involvement in processing affective stimuli.  

Furthermore, exploratory whole-brain analyses revealed that a parahippocampal region, most likely corresponding to perirhinal cortex, showed subsequent memory effects for faces.  

The possible influence of activity in neighboring brain regions such as the perirhinal cortex, and pre- and para-subiculum on the construction of the hippocampal spatial representation is then discussed..  

Empirical evidence and computational work have provided biologically plausible models of the neural substrate and mechanisms underlying the coding of stimulus novelty in the perirhinal cortex.  

Some projections terminate throughout the entorhinal cortex (afferents from medial area 13 and posterior parahippocampal cortex), while others have more limited termination, with emphasis either rostrally (lateral orbitofrontal cortex, agranular insular cortex, anterior cingulate cortex, perirhinal cortex, unimodal visual association cortex), intermediate (upper bank of the superior temporal sulcus, unimodal auditory association cortex) or caudally (parietal and retrosplenial cortices).  

These regions, incorporating bilateral anterior ventral rhinal cortices, perirhinal cortex and left anterior hippocampus are regions previously implicated in high-level visual perception.  

Here, we performed electron microscopic immunocytochemistry with the nondiffusible gold label to explore the relationship among levels of drebrin A, the NR2A subunit of N-methyl-D-aspartate receptors, and the size of spines in the perirhinal cortex of adult mouse brains.  

The perirhinal cortex (PRC) is a supra-modal cortical area that collects and integrates information originating from uni- and multi-modal neocortical regions and directed to the hippocampus.  

The relative contributions of the hippocampus and the perirhinal cortex to recognition memory are currently the subject of intense debate. Whereas some authors propose that both structures play a similar role in recognition memory, others suggest that the hippocampus might mediate recollective and/or associative aspects of recognition memory, whereas the perirhinal cortex may mediate item memory. Using a novel recognition memory test for faces and scenes, participants with broad damage to MTL structures, which included the hippocampus and the perirhinal cortex, were impaired on both face and scene memory.  

In both schizophrenia and bipolar disorder, NTNG2 mRNA was reduced in CA3, with reductions also found in CA4 and perirhinal cortex in bipolar disorder.  

In slices devoid of physiological or pharmacological manipulations, spontaneous multi-neuronal bursts recorded extracellularly at the perirhinal cortex precede bursts simultaneously recorded at the ACx, suggesting their caudorostral propagation. Population imaging from P2-5 slices with fura-2 AM revealed endogenously generated waves that spread from the perirhinal cortex toward the thalamorecipient ACx.  

Since AD neurofibrillary pathology begins more laterally in the transentorhinal region (TR) of the perirhinal cortex, volumetric measures of this structure might provide more sensitive preclinical markers of AD, provided its anatomic location is known.  

The findings are in good agreement with the view of dissociable memory processing by the perirhinal cortex (anterior MTL) and parahippocampal cortex (posterior MTL), depending upon the neocortical input that these regions receive..  

MATERIALS AND METHODS: We conducted in vivo microdialysis experiments in behaving rats measuring DA and 5-HT in the perirhinal cortex (PRC), entorhinal cortex (EC), and PFC, after application of cocaine (0, 5, 10, 20 mg/kg; i.p.) or d-amphetamine (0, 0.5, 1.0, 2.5 mg/kg; i.p.).  

The cerebellum, amygdala and perirhinal cortex are involved in fear learning but the different roles that these three structures play in aversive learning are not well defined. Finally, the inactivation of the perirhinal cortex never alters retrieved fear traces, showing important differences between the amygdala, cerebellum and perirhinal cortex in emotional memories..  

Regions most significantly affected include prelimbic, anterior cingulate, orbital frontal and perirhinal cortex.  

Lesion studies have shown that rat perirhinal cortex (PR), a polymodal sensory region that is reciprocally connected with the amygdala, is critical for normal fear conditioning to so-called "22 kHz USVs".  

The perirhinal cortex plays a critical role in memory formation, in part because it forms reciprocal connections with the neocortex and entorhinal cortex and is thus in a position to integrate and transfer higher-order information to and from the hippocampus. Using patch recordings in vitro and tract-tracing combined with GAD-67 immunohistochemistry, we show that the perirhinal cortex contains GABAergic neurons with long-range projections to superficial entorhinal cells.  

The parahippocampal cortex also contributes to recollection, possibly via the representation and retrieval of contextual (especially spatial) information, whereas perirhinal cortex contributes to and is necessary for familiarity-based recognition.  

First, studies in rodents, nonhuman primates, and humans suggest that the perirhinal cortex represents information about objects for both mnemonic and perceptual purposes. Whereas the perirhinal cortex plays an essential role in familiarity-based object recognition, the hippocampus contributes little, if at all, to this function. In both primates and rodents, the hippocampus contributes to the memory and perception of places and paths, whereas the perirhinal cortex does so for objects and the contents of scenes..  

Single neurons in perirhinal cortex are sensitive to associations between the cues and the reward schedules. The responses of the entorhinal cortex neurons are similar to responses of perirhinal cortex neurons in that they are selective for the associative relationships between cues and reward schedules. However, they are particularly selective for the first trial of a new schedule, in contrast to perirhinal cortex where responsivity to all schedule states is seen. These results indicate that the entorhinal signals carry associative relationships between the visual cues and reward schedules, and between rewards and reward schedules that are not simply derived from perirhinal cortex by feed-forward serial processing..  

The hippocampal formation, including the subiculum and presubiculum, together with the entorhinal cortex (EC) and perirhinal cortex (area 35) contribute numerous axons to the fornix in a topographical manner. In contrast, the lateral perirhinal cortex (area 36) and parahippocampal cortical areas TF and TH only contained a handful of cells labeled via the fornix. The medial fornix originates from cells in the caudal half of the subiculum, the lamina principalis interna of the caudal half of the presubiculum, and from the perirhinal cortex (area 35). The intermediate portion of the fornix (i.e., that part midway between the midline and most lateral parts of the fornix) originates from cells in the rostral half of the subiculum and prosubiculum, the anterior presubiculum (only from the lamina principalis externa), the caudal presubiculum (primarily from lamina principalis interna), the rostral half of CA3, the EC (primarily 28I and 28M), and the perirhinal cortex (area 35).  

Our results suggest that general and verbal memory impairments in patients with left MTLE are associated with atrophy of the hippocampus, the entorhinal, and the perirhinal cortex.  

Two major pathways have been identified in the rat; one projection targets the hippocampus via perirhinal cortex and lateral entorhinal cortex (LEC) while another targets the hippocampus via postrhinal cortex and medial entorhinal cortex (MEC).  

The present study examined the role of the medial prefrontal cortex (mPFC) and perirhinal cortex (PRH) in these distinct recognition memory processes using a series of behavioral tests: a novel object preference task, an object-in-place task, and a temporal order memory task.  

The perirhinal cortex is believed to process aspects of recognition memory. We have used the R6/1 mouse model of HD to assess synaptic plasticity in the perirhinal cortex.  

The perirhinal cortex (PRh) is widely accepted as having an important role in object recognition memory in humans and animals.  

The persistent activity can also be initiated and terminated by synchronized synaptic stimuli of layer II/III of the perirhinal cortex.  

In the perirhinal cortex we detected decreased expression of GluR5 in all three diagnoses, of GluR1, GluR3, NR2B in both BD and MDD, and decreased NR1 and NR2A in BD and MDD, respectively.  

In addition, perirhinal cortex, anterior lateral hypothalamus and ventrolateral periaqueductal gray showed conditioned response renewal effects. It is suggested that context-dependent fear renewal is associated with (1) tone-evoked activation of the excitatory conditioned stimulus representation in the auditory system, (2) associative activation of the unconditioned stimulus representation in somatic and visceral sensory nuclei in the absence of the unconditioned stimulus, and (3) neural activation of the perirhinal cortex, hypothalamus and periaqueductal gray.  

In particular, we did not extend the perirhinal cortex into the temporal pole, and the lateral boundaries of areas 36 and TF with area TE were placed more medially than in other studies.  

Rats were chronically implanted with an electrode into the basolateral amygdala, perirhinal cortex, or ventral hippocampus and stimulated twice daily until 3 fully generalized, class 5 seizures were elicited. Kindling of basolateral amygdala, but not perirhinal cortex or ventral hippocampus, disrupted PPI when testing began 2min, but not 48h, following the elicitation of the third class 5 seizure.  

Studies of object recognition memory have helped elucidate the anatomical structures involved in declarative memory, indicating a critical role for perirhinal cortex. We offer a mechanistic account of the effects of perirhinal cortex damage on object recognition memory, based on the assumption that perirhinal cortex stores representations of the conjunctions of visual features possessed by complex objects. Such representations are proposed to play an important role in memory when it is difficult to solve a task using representations of only individual visual features of stimuli, thought to be stored in regions of the ventral visual stream caudal to perirhinal cortex. We present simulations addressing the following empirical findings: (1) that impairments after damage to perirhinal cortex (modeled by removing the "perirhinal cortex" layer of the network) are exacerbated by lengthening the delay between presentation of to-be-remembered items and test, (2) that such impairments are also exacerbated by lengthening the list of to-be-remembered items, and (3) that impairments are revealed only when stimuli are trial unique rather than repeatedly presented. This study shows that it may be possible to account for object recognition impairments after damage to perirhinal cortex within a hierarchical, representational framework, in which complex conjunctive representations in perirhinal cortex play a critical role..  

We compared single-cell activities in perirhinal cortex (PRh) as well as adjacent visual cortex (area TE) across two tasks.  

The hippocampal c-fos findings produced a dissociation with the perirhinal cortex, where no change was observed.  

Specifically, emerging findings demonstrate that the level of engagement of perirhinal cortex predicts later memory for individual items, whereas the level of hippocampal processing correlates with later relational memory, or recovery of additional episodic details.  

It has been argued that damage to the perirhinal cortex should impair visual discriminations when the stimuli have overlapping features. In Experiment 1, rats with perirhinal cortex lesions were trained on a series of visual discriminations in a water tank, culminating in a biconditional discrimination. Taken together, the study failed to find evidence that the rat perirhinal cortex is necessary for configural visual discriminations and so revealed that some ambiguous visual discriminations can be learnt when this area is removed.  

By contrast, during processing of negatively valenced words versus non-words, relatively greater activation was seen in the left perirhinal cortex and hippocampus for women versus men, and in the right supramarginal gyrus for men versus women.  

However, a larger commissural projection pathway originates in the paralimbic medial temporal lobe and electrical stimulation of the anterior perirhinal cortex can induce contralateral epileptic discharges with delays as short as 100 ms (Adam et al., 2004).  

Consistent with this new concept and with a large volume of experimental data, I propose that awareness of intraoral food is related to the concomitant reverberant self-sustained activation of a coalition of neuronal subsets in agranular insula and orbitofrontal cortex (affect, hedonics) and agranular insula and perirhinal cortex (food identity), as well as the amygdala (affect and identity) in humans.  

In particular, the effects in entorhinal and perirhinal cortex and hippocampus might be important for encoding new episodic memories..  

In each of 11 subjects, we found that the perirhinal cortex was active during both spatial and object memory encoding, while the anterior parahippocampal cortex was active only during spatial encoding.  

In the present study, we investigated the role of cortical acetylcholine in a rodent model of declarative memory by infusing the cholinergic muscarinic receptor antagonist scopolamine into the rat perirhinal cortex during different stages (encoding, storage/consolidation, and retrieval) of the spontaneous object recognition task. Rather, the cholinergic input to the perirhinal cortex may facilitate acquisition by enhancing the cortical processing of incoming stimulus information..  

Finally, activation in the perirhinal cortex correlated with successful associative binding regardless of the form of later memory, i.e., recognition or free recall, providing novel evidence for the role of the perirhinal cortex in episodic intra-item encoding..  

Previous fMRI studies have demonstrated preferential involvement of the perirhinal cortex and hippocampus in tasks of object and spatial memory, respectively. It was found that the detection of an object identity change was associated with significant right perirhinal cortex activity.  

We show a drug modulation in left prefrontal and perirhinal cortex during recollection. We discuss the findings in terms of acetylcholine mediation of the familiarity/novelty signal through perirhinal cortex and the control of the relative signal strength through prefrontal cortex..  

The perirhinal cortex processes aspects of recognition memory and the underlying mechanism is believed to be long-term depression (LTD) of excitatory neurotransmission, the converse of long-term potentiation (LTP). We have used the R6/1 mouse model of HD to assess synaptic plasticity in the perirhinal cortex. Layer II/III neurones gradually lose their ability to support LTD, show early nuclear localization of mutant huntingtin and display a progressive loss of membrane integrity (depolarization and loss of cell capacitance) accompanied by a reduction in the expression of D1 and D2 dopamine receptors visualized in layer I of the perirhinal cortex.  

The role of the perirhinal cortex in discriminative eyeblink conditioning was examined by means of feature-positive discrimination procedures with simultaneous (A-/XA+) and serial (A-/X-->A+) stimulus compounds. Lesions of the perirhinal cortex severely impaired acquisition of simultaneous feature-positive discrimination but produced no impairment in serial feature-positive discrimination. The results suggest that the perirhinal cortex plays a role in discriminative eyeblink conditioning by resolving ambiguity in discriminations with overlapping stimulus elements..  

No significant variation of Fos expression was measured in the perirhinal cortex.  

By this view, a fundamental function of the mammalian hippocampus is to combine incoming information about spatial context from the postrhinal (parahippocampal in primates) cortex and medial entorhinal area with incoming information about nonspatial items from the perirhinal cortex and lateral entorhinal area.  

In particular, the hippocampus has been implicated in spatial memory, whereas perirhinal cortex seems critical for object memory.  

To study the roles of the perirhinal cortex (PRh) and temporal cortex (area TE) in stimulus-reward associations, we recorded spike activities of cells from PRh and TE in two monkeys performing a visually cued go/no-go task.  

The laterodorsal subdivision is located along the rhinal sulcus and borders area 35 of the perirhinal cortex.  

Recent research has indicated that anteromedial temporal cortex (including the perirhinal cortex) may function as the endpoint of a hierarchically organized visual object-processing network providing the basis for fine-grained discrimination among objects.  

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