Rhinal Sulcus

After crossing the lateral rhinal sulcus, the middle cerebral artery emitted a sequence of rostral and caudal convex hemispheric cortical collateral branches on the convex surface of the cerebral hemisphere to the frontal, parietal, temporal and occipital lobes.  

We used four sulcal patterns classes to categorize the sulcal arrangement in the inferior surface of the temporal lobe in each subject: Type 1, i.e., single-branch, unbroken collateral sulcus (CS) connected with the rhinal sulcus (RS) anteriorly; Type 2, i.e., CS connected with the occipitotemporal sulcus (OTS), but separated from the RS; Type 3, i.e., CS separated from the OTS and RS, which are connected; and Type 4, i.e., CS, OTS and RS separated.  

In horizontal slices located ventrally to the rhinal sulcus, where we stimulated area 35 and the lateral amygdala, both inputs can be independently conveyed to the dentate gyrus.  

It remains to be demonstrated if the right EC rhinal sulcus pattern association with AD reflects genetic or developmental influences.  

Before crossing the lateral rhinal sulcus, the common trunk of the middle cerebral artery frequently bifurcated in a rostral and a caudal branch.  

We observed two distinct pathways that convey neural activation evoked by olfactory nerve stimulation: a medial pathway from the PC to the AC, and a lateral pathway from the PC to the lateral EC along the rhinal sulcus. Lesion experiments revealed that the lateral pathway close to the rhinal sulcus is crucial for neural activation of the EC.  

However, only the rhinal sulcus was always present.  

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

Odor-induced cortical activation, which primarily originated in layer II, appeared in a narrow band beneath the rhinal sulcus over the lateral olfactory tract, corresponding to the dorsal part of the anterior piriform cortex.  

Area 35 is situated along the entire rostro-caudal extent of the fundus of the posterior rhinal sulcus, whereas area 36 occupies its lateral bank. Two fields of the postrhinal cortex were identified in the additional postrhinal gyrus, which is found in the fundus of the most caudal extent of the posterior rhinal sulcus..  

In addition, cells in septal portions of the subiculum project to a lateral band of entorhinal cortex parallel to the rhinal sulcus and to peri- or postrhinal cortices, whereas cells in more temporal portions project to more medial parts of the entorhinal cortex.  

The results demonstrate that the propagation of neuronal activity across the rhinal sulcus in the direction from the PRC to the EC is finely and diffusely distributed.  

On the internal side, this posterior limit corresponds to the rhinal sulcus, an anterior and internal extention of the collateral sulcus.  

Even though the largest associative interactions between superficial layers are restricted within either the m-EC or the l-EC, both rostral and caudal stimuli in the EC region close to the rhinal sulcus induced activity that propagated across the border between l- and m-EC..  

Both neocortical and local stimulation of area 36 determined a brief monosynaptic excitatory potential in layer II-III neurons, followed by a biphasic synaptic inhibitory potential possibly mediated by a feed-forward inhibitory circuit at sites close to the stimulation electrode and a late excitatory postsynaptic potential (EPSP) that propagated at distance within area 36 along the rhinal sulcus.  

Iontophoretic injection of GABA gave an inhibitory effect on MGB neurons similar to that caused by stimulating the amygdala or the auditory cortex behind the rhinal sulcus (ACBRS), and in particular, the GABA induced suppression could be completely antagonized by application of bicuculline.  

The perirhinal cortex (PRC), the region of temporal cortex adjacent to the rhinal sulcus, has been suggested as a critical substrate for the development and expression of generalized motor seizures in the late stages of kindling development.  

Finally, the authors observe that projections from the IPL, except for its anteriormost portion, converge at the perirhinal-entorhinal border around the posterior tip of the rhinal sulcus.  

The rhinal sulcus, which separates parahippocampal and temporal cortices in other species, including the anthropoid apes, is either lacking or rudimentary in the human brain.  

The recordings revealed the presence of at least two systematic representations of the contralateral body surface located in a continuous strip of cortex running from the rhinal sulcus to the medial wall.  

Extracellular synaptic responses were recorded from superficial layers of the perirhinal cortex directly below the rhinal sulcus, in response to electrical stimuli delivered in the superficial or intermediate layers to the entorhinal or temporal cortex sides of the rhinal sulcus.  

One stimulating electrode was placed on the temporal side and the other on the entorhinal side of the rhinal sulcus in either the superficial or intermediate layers (approximately layers II/III).  

The fundus of the rhinal sulcus (area 35) projected to both lateral and medial entorhinal cortices, ventral subiculum, lateral and basolateral nuclei, and amygdalostriatal transition zone. The rat perirhinal cortex is heterogeneous in its efferent connectivity, and distinct projections arise from the dorsal and ventral banks and fundus of the rhinal sulcus.  

The cortical regions dorsally adjacent to the posterior rhinal sulcus in the rat can be divided into a rostral region, the perirhinal cortex, which shares features of the monkey perirhinal cortex, and a caudal region, the postrhinal cortex, which has connectional attributes similar to the monkey parahippocampal cortex.  

We investigated the projection originating in the dorsal part of the entorhinal cortex by injecting Dil along the rhinal sulcus.  

We report that cortical areas, which resemble the insular fields of other mammals, are located in the cat's orbital gyrus and anterior rhinal sulcus. Our data suggest four such areas: (a) a "ventral agranular insular area" in the lower bank of the anterior rhinal sulcus, architectonically transitional between iso- and allocortex and sparsely connected to the thalamus, mainly with midline nuclei; (b) a "dorsal agranular insular area" in the upper bank of the anterior rhinal sulcus, linked to the mediodorsal, ventromedial, parafascicular and midline nuclei; (c) a "dysgranular insular area" in the anteroventral half of the orbital gyrus, characterized by its connections with gustatory and viscerosensory portions of the ventroposterior complex and with the ventrolateral nucleus; and (d) a "granular insular area", dorsocaudal in the orbital gyrus, which is chiefly bound to spinothalamic-recipient thalamic nuclei such as the posterior medial and the ventroposterior inferior.  

The collateral sulcus is a continuation of the rhinal sulcus in 41.9%. The rhinal sulcus represents the anterolateral border of the entorhinal region. By defining four branches of the rhinal sulcus all the possible ramifications occurring in the investigated hemispheres could be described. In 19.0% of the cases, a well developed entorhinal sulcus emerges in the central portions of the entorhinal region. An incipient entorhinal sulcus is evident in 29.6% and the sulcus is absent in 51.4% of the investigated cases.  

One of the tracers was injected into the lateral amygdaloid nucleus and the other into the temporal cortical areas close to the rhinal sulcus.  

Performance of rats in the Morris water maze was measured after small excitotoxic lesions were produced bilaterally in two areas in the insular cortex, 0.3 and 2.3 mm posterior to bregma in the upper bank of the rhinal sulcus.  

Hence, the medial side of the entorhinal region extends up to the uncus and the lateral side into the main branch of the rhinal sulcus.  

According to the histological examination, the lesions covered medial and lateral banks of the rhinal sulcus completely and most the entorhinal and perirhinal cortex.  

The affected region covered the middle one-third portion from the longitudinal fissure to the rhinal sulcus and was predominately seen in layers II-III of the cortex.  

Thalamic lesions were aimed at the lateral internal medullary lamina (L-IML) and cortical lesions at the projection areas of the mediodorsal nucleus along the medial wall (MW) and dorsal to the rhinal sulcus (RS) in frontal cortex.  

We investigated the organization of reciprocal connections revealed by injections of Dil in the entorhinal cortex along the rhinal sulcus.  

Rats were trained on an olfactory continuous delayed nonmatching-to-sample (DNMTS) task and then given 1 of 4 treatments: sham surgery or radio-frequency lesion of the lateral internal medullary lamina of the thalamus or of the frontal cortex along the medial wall or dorsal to the rhinal sulcus.  

Three of the monkeys then had the cortex within and adjacent to the rhinal sulcus removed bilaterally, while the other four served as an unoperated control group.  

In one group of rats the dorsolateral isocortex, from the dorsomedial shoulder to the dorsal lip of the rhinal sulcus was removed bilaterally in a single surgical session.  

The temporal polar cortex is the ventral polar region of the posterior sylvian and posterior ectosylvian gyri, which is located dorsal to the posterior rhinal sulcus and includes the ectorhinal area.  

Three other prominent features of the last quarter of gestation are illustrated: the refinement of the modular neurochemical organization of the lamina principalis externa, the delayed chemoanatomical development of the rhinal sulcus area, and the establishment of a distinct rostrocaudal pattern of neurochemical distribution.  

At E56 the cortical plate of the entorhinal cortex already exhibited a sublamination; at E64 the lamina dissecans was partly formed, allowing the emergence of the lamina principalis externa and interna, and at E83 most of the regional and laminar subdivisions characteristic of the adult cortex could be identified, except for the rhinal sulcus restricted to a small dimple. A faint neurotensin-like immunoreactivity first detected at E64 became prominent at E83 in the entorhinal cortex but stopped abruptly at the anlage of the rhinal sulcus.  

Recent anatomical studies in this laboratory have demonstrated that the proisocortex cortex adjacent and dorsal to the rhinal sulcus is one of the major forebrain afferent inputs to the midbrain periaqueductal gray matter in the rat.  

The effect of stimulation of amygdaloid complex on the click evoked potential of Woolsey's AI, AII and the auditory cortex behind the rhinal sulcus (ACBRS) was examined by single unit analysis.  

Neurones signalling information of use for recognition memory are found in cortex close to the rhinal sulcus where lesions result in major deficits in the performance of recognition memory tasks.  

The effective lesions included parts of the cortex both dorsal and ventral to the rhinal sulcus and extended from approximately 1.8 to 3.8 mm posterior to bregma. Lesions slightly more posterior (2.3-4.8 mm posterior to bregma) or lesions that included only the perirhinal cortex dorsal to the rhinal sulcus had no effect.  

RESULTS: We found that 64 +/- 3% of neocortex above the rhinal sulcus was infarcted; this infarction was evenly distributed through the cerebral hemispheres.  

In the cortex, anterograde and retrograde labeling was found in the presylvian sulcus, cingulate gyrus, cruciate sulcus, medial prefrontal area, lateral suprasylvian cortex, and posterior rhinal sulcus.  

Other cortical regions labelled less consistently included the anterior ectosylvian sulcus itself, the insular cortex of the anterior sylvian gyrus, and the posterior rhinal sulcus.  

The incidence of response-related activity was 57.4% in cortical areas adjacent to the rhinal sulcus plus medial inferotemporal cortex, and 40.2% for the hippocampal formation.  

Similar to paleocortex below the rhinal sulcus, limbic cortex in the rhinal sulcus has a "sandwich" gradient: the older posterior agranular insular area is sandwiched by anterior and posterior younger areas (ventral agranular insular and perirhinal).  

Heaviest cortical labelling was localized in perirhinal cortex, in an extensive band of cells adjoining the rhinal sulcus.  

There were significant decreases in binding in the frontal and cingulate cortices, the rhinal sulcus, the dorsolateral aspect of the caudate-putamen, and in the ventral tegmental area.  

NTH-sites subsisted partly in the Islands of Calleja and no significant alteration was observed in the rhinal sulcus and in the cingulate cortex.  

Injections of retrograde tracers located caudally in the dentate gyrus resulted in a rostrocaudally oriented zone of labeled cells that was situated laterally in the entorhinal cortex adjacent to the rhinal sulcus. The zone of labeled cells was not oriented strictly parallel to the rhinal sulcus since at caudal levels it extended medially to encompass the full transverse extent of the most caudal portion of the entorhinal cortex.  

These areas included the medioventrally located genual, subcallosal and piriform cortices, as well as the cortex of the ventral bank of the anterior rhinal sulcus and the caudal part of the orbital gyrus.  

Furthermore, a group of unimodal, visually responsive cells often was found in the upper bank of the anterior rhinal sulcus.  

The transition from EC to prorhinal cortex occurs along the medial bank of the rhinal sulcus and is characterized by a band of AChE staining, which slopes obliquely away from layer II until it joins an intermediate pyramidal cell layer.  

Moreover, application of 2% procaine to block the auditory cortex behind the rhinal sulcus (ACBRS) could abolish the facilitory effect, with a long latency, of the orbital cortex.  

Area 35 occupies the fundus and part of the lateral aspect of the rhinal sulcus. Area 36 extends from the lateral bank of the rhinal sulcus into the inferior temporal gyrus, where it borders fields TA and TE rostrally, and field TF of the parahippocampal gyrus caudally.  

Outside the prefrontal cortex dopaminergic fibres were observed in adjacent frontal areas, the cortex surrounding the entire rhinal sulcus and the retrosplenial cortex.  

After injection of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) into the VPMpc, both anterogradely labeled axon terminals and retrogradely labeled neuronal cell bodies were found ipsilaterally in three discrete regions of the cerebral cortex, i.e., in the orbital cortex, caudoventral part of the infralimbic cortex, and medial part of the fundus of the posterior rhinal sulcus (perirhinal area); in the subcortical regions, anterogradely labeled axon terminals were seen ipsilaterally in the rostrodorsal part of the lateral amygdaloid nucleus.  

The more lateral parts of the parahippocampal cortex, which surround the posterior rhinal sulcus, project in addition to extensive parts of the paralimbic association cortex that include the proisocortical cingular, prelimbic, orbitofrontal, and agranular and granular insular cortices.  

The connections between AEV and other cortical areas are reciprocal and, at least in part, topographically organized: the rostral AEV is connected with the bottom region of the presylvian sulcus, the lower bank of the cruciate sulcus, the rostral part of the ventral bank of the splenial sulcus, the rostral portion of the lateral suprasylvian visual area (LS) and the lateral bank of the posterior rhinal sulcus; the caudal AEV is connected with the bottom region of the presylvian sulcus, the caudal part of LS, the ventral part of area 20 and the lateral bank of the posterior rhinal sulcus.  

In the sensorimotor regions, the first axons to reach the midline at E18 arise from two separated groups of cells situated medially near the superior sagittal sinus and laterally just above the rhinal sulcus.  

Other cortical areas projecting (in a lower density) to the VMP were the motor cortex, the cortex along the anterior ectosylvian sulcus, the granular insular cortex, the posterior agranular insular area, the prelimbic area, and the cortex along the posterior rhinal sulcus (SRP).  

With HRP injections into the paracentral and centrolateral nuclei, labeled neurons were observed in the gyrus proreus and the cortical areas between the caudal presylvian sulcus and anterior rhinal sulcus ipsilaterally, and in the nuclei interstitialis and Darkschewitsch bilaterally.  

Finally the gustatory cortex, which lies just dorsal to the rhinal sulcus, receives a basolateral projection from neurons in the lateroventral one-half of the basolateral nucleus.  

Only the anterior and most ventral parts of the insular cortex overlying the anterior rhinal sulcus were connected with the mediodorsal nucleus of the thalamus.  

The amygdalopetal cortex on the dorsal and lateral surfaces of the rat brain is limited to a narrow strip of periallocortex that forms the dorsal wall and lip of the rhinal sulcus.  

Fibers forming a lateral pathway travel in the fronto-occipital fasciculus and connect the dorsolateral prefrontal cortex with the fundus of the rhinal sulcus, posterior subdivisions of the parahippocampal gyrus, and the presubiculum.  

As anticipated from the results of the retrograde tracing experiments, injections located laterally, in or close to the posterior rhinal sulcus, produce prominent labeling over the septal pole of the hippocampus, whereas progressively more medially located injections result in progressively more temporally located labeling.  

One pair (anterior pair) covered the medial part of the temporal tip (area TG), starting at the rhinal sulcus and extending 3 mm laterally.  

They were distributed from anterodorsal to posteroventral direction in the insular cortex just dorsal to the rhinal sulcus and ventral to the somatic sensory area I.  

The cerebral cortical taste area is located dorsal to the rhinal sulcus in or near the insular cortex in different species of animals.  

Terminal fields are further segregated within perirhinal cortex to either the dorsal or ventral banks of the rhinal sulcus.  

Mediolaterally the lateral limit of the band was at the dorsal lip of the rhinal sulcus.  

Unilateral injections of horseradish peroxidase (HRP) were made iontophoretically along the rhinal sulcus. We consider the cortex situated posterior to the gustatory cortex in and above the rhinal sulcus as the core region of the rat's (associative) insular cortex, as this cortex receives afferents from the regions of and between the nuclei suprageniculatus and geniculatus medialis, pars magnocellularis. The cortex dorsal and posterior to the insular cortex we consider auditory cortex, as it receives afferents from the principal part of the medial geniculate nucleus, and the cortex ventral to the insular cortex (below the fundus of the rhinal sulcus) we consider to constitute the prepiriform cortex, which is athalamic.  

The results clearly distinguished functional subdivisions of the rodent prefrontal cortex: Rats with lesions of the prefrontal cortex that primarily involve the dorsal bank of the rhinal sulcus were impaired selectively and exhibited increased perseveration of responses in a go, no-go odor discrimination task.  

The responses were obtained only from the dorsal bank of the rhinal sulcus. When the dorsal bank of the rhinal sulcus was stimulated, antidromic responses with a latency of about 4.4 msec were recorded from the superficial and deep soma layers of the piriform cortex. Following injections of horseradish peroxidase into the dorsal bank of the rhinal sulcus, labeled cells were found in the piriform cortex, the lateral, basolateral and central amygdaloid nuclei, and the prelimbic area.  

[ 3H]NT receptors are highly concentrated in the external layer of the olfactory bulb, in the rhinal sulcus, in certain nuclei of the amygdala, in the substantia nigra, zona compacta and in the ventral tegmental area.  

These neocortical cells occupy an extensive field stretching from gyrus proreus to the posterior ectosylvian gyrus and from the rhinal sulcus to the suprasylvian sulcus.  

The sensorimotor and visual cortices provide the bulk of corticofugal fibers, but contributions from the following association areas were noted: frontal cortex, (dependent of the thalamic mediodorsal nucleus), rhinal sulcus region, and cingulate cortex..  

This and a sparse projection from dorsal and posterior "insular" cortex (rhinal sulcus) have not been described in detail in previous studies..  

The results indicate that Sm projects topographically on to layer 3 of a distinct agranular cortical field that occupies the posterolateral gyrus proreus, the adjacent fundus of the rhinal sulcus, and the postero-ventral portion of the medial wall of the presylvian sulcus.  

Based on afferents from the medial, the lateral, and from both parts of the thalamic mediodorsal nucleus, three prefrontal subregions were defined, namely the sulcal (within and above the rhinal sulcus), the medial (anterior and superior to the genu of the corpus callosum), and the fronto-polar subfield.  

ACp was found to project to the contralateral cortex along the rhinal sulcus. There was also a distinct projection to neocortex on the lateral surface above the rhinal sulcus which appears to be analogous to the temporal cortex projection of ACp in other species.  

Auditory responsive regions were found to lie behind the rhinal sulcus, extending from its midpoint to its inferior border.  

It includes a small area within and dorsal to the rhinal sulcus and a comparatively larger region within the medial half of the anterior cortex.  

It was shown that the periamygdaloid cortex immediately below the rhinal sulcus and extending medially to the amygdaloid fissure projects to the lateral nucleus.  

Lesions of the mediodorsal thalamic nucleus or frontal neocortex of the rhinal sulcus did not result in anosmia, but did eliminate or alter odor preferences and resulted in inappropriate, inefficient, precopulatory and copulatory behavior.  

This part of MD projects to the frontal neocortex of the rhinal sulcus (RS), while other parts of the MD project to the anterior medial wall of the neocortex (MW).  

At the level of Forceps Minor, there were elevated levels of receptors in the deeper layers of the cingulate cortex, in the region above the rhinal sulcus and in an area dorsal to the accumbens.  

Following HRP injections confined to the areas of the VTA containing the dopamine cell groups, labelled neurons appeared in prefrontal cortex, dorsal bank of rhinal sulcus, nucleus accumbens, bed nucleus of stria terminalis, amygdala, diagonal band of Broca, substantis innominata, magnocellular preoptic area, medial and lateral preoptic areas, anterior, lateral and postero-dorsal hypothalamus, lateral habenular, nucleus parafascicular nucleus of thalamus, superior colliculus, nucleus raphe dorsalis, nucleus raphe nagnus and pontis, dorsal and ventral parabrachial nuclei, locus coeruleus and deep cerebellar nuclei.  

Intracranial self-stimulation (ICSS) of the prefrontal cortex dorsal to the rhinal sulcus in rats has been abolished by means of injections of 6-hydroxydopamine (6-OHDA) (4 micrograms/2 microliters) into the ascending trajectory of the A10 mesocortical dopaminergic fibers ipsilateral to the stimulation electrodes.  

The prefrontal cortex, dorsal to the rhinal sulcus of the rat (hereinafter termed the agranular insular cortex) has been examined with the use of the retrograde transport of horseradish peroxidase.  

The projection field occupied the entire medial wall rostral to a mid corpus callosal level, wrapped around the frontal pole onto the lateral convexity and tailed off caudally on the dorsal bank of the rhinal sulcus.  

Of particular importance are the veins ending in the basal vein and those cortical ones that run in the rhinal sulcus.  

The medial segment of the nucleus projects to the prelimbic area (32) on the medial surface of the hemisphere, and to the dorsal agranular insular area, dorsal to the rhinal sulcus on the lateral surface. The lateral segment projects to the anterior cingulate area (area 24) and the medial precentral area on the dorsomedial shoulder of the hemisphere, while the central segment projects to the ventral agranular insular area in the dorsal bank of the rhinal sulcus, and to a lateral part of the orbital cortex further rostrally. (The term "orbital" is used to refer to the cortex on the ventral surface of the frontal pole of the hemisphere.) A ventral part of this orbital cortex also receives fibers from the mediodorsal nucleus, possibly its lateral segment, but the medial part of the orbital cortex, and the ventrolateral orbital area in the fundus of the rhinal sulcus receive projections from the paratenial nucleus and the submedial nucleus, respectively.  

Rats that self-stimulated from electrodes implanted in either the substantia nigra pars compacta (SNC) or the dorsal tegmental noradrenergic bundle (DTB) received bilateral electrolytic lesions of the prefrontal cortex dorsal to the rhinal sulcus.  

A deep sulcal field was situated between the dorsal bank of the rhinal sulcus and the lateral cortex above it.  

Lesions in orbital cortex (on the dorsal lip of the rhinal sulcus) or prefrontal cortex (area 10) significantly retarded the rate of amygdaloid kindling; lesions in motor cortex, anterior cingulate cortex, or visual cortex were without effect.  

A previously undescribed projection to the prosubiculum and hippocampus has been found to originate from the prorhinal cortex which forms the medial wall of the rhinal sulcus along the lateral-most portion of the entorhinal cortex in the rhesus monkey.  

Although these connections characterized all areas, with the exception of Walker's area 14 and Bonin and Bailey's area FL, the caudal levels of the orbitofrontal area were found to give rise to an additional projection which terminated in the entorhinal cortex and the transitional cortices bordering the rhinal sulcus.  

It was observed that virtually all ventral temporal neocortical areas contribute some afferents to the transitional zones of periallocortex (perirhinal and prorhinal cortices) forming the walls of the rhinal sulcus.  

[ View All ]