Area 6 Of Premotor Cortex

Two critical nodes of the dorsomedial visuomotor stream [ V6A (anterior visual area 6) and PMd (dorsal premotor cortex)] increased their activity with increasing object slant, regardless of viewing conditions.  

By contrast, we observed hyperactivation in the right-sided Brodmann's area 6 for the less demanding verb repetition task.  

In addition, the right parietal area and the bilateral premotor area 6 were also involved.  

Recent studies have expanded our knowledge of the dorsal and ventral premotor areas, which occupy the lateral part of area 6 in the frontal cortex.  

Patients with lesions to the superior medial parts of the frontal lobes, in particular to the left superior portion of Brodmann area 6 (which includes the supplementary motor areas and the premotor areas for the right hand) had an increased number of false alarms (incorrect responses to the nogo stimulus). These results indicate that area 6 is specifically involved in the inhibition of response.  

Brodmann's cytoarchitectonic map of the human cortex designates area 4 as cortex in the anterior bank of the precentral sulcus and area 6 as cortex encompassing the precentral gyrus and the posterior portion of the superior frontal gyrus on both the lateral and medial surfaces of the brain. More than 70 years ago, Fulton proposed a functional distinction between these two areas, coining the terms primary motor area for cortex in Brodmann area 4 and premotor area for cortex in Brodmann area 6.  

Conversely, bipolar recordings between neighbouring contacts implanted in the SMA-proper and in the frontal external regions showed inversion recovery at more superficial contacts, implanted in area 6. CONCLUSIONS: Among premotor areas, somatosensory inputs seem to reach pre-SMA and area 6 but not SMA-proper.  

According to Brodmann's cytoarchitectonic map, this region belongs to the dysgranular Brodmann area 6 of the premotor cortex. Here, one human brain has been analyzed to obtain preliminary data about the cytoarchitectonical changes of a part of area 6.  

In addition, we have shown that pyramidal cells in premotor area 6 are larger, more branched, and more spinous than those in the primary motor cortex (MI or area 4) in the macaque monkey, vervet monkey, and baboon. We found, as in monkeys, a progressive increase in the morphological complexity of pyramidal cells through areas 3b, 5, and 7, as well as from area 4 to area 6, suggesting that areal specialization in microcircuitry was likely to be present in a common ancestor of primates.  

For each cortical domain, we show the anatomical position and extent of visuo-oculomotor activity, including evidence that the dorsolateral frontal activation, which includes the frontal eye field (on the anterior bank of the arcuate sulcus), extends anteriorly into posterior principal sulcus (area 46) and posteriorly into part of dorsal premotor cortex (area 6).  

In contrast, the self rotation task activated left supplementary motor area (SMA; area 6).  

The specific areas with an increase in perfusion in the affected hemisphere were in the precentral gyrus, premotor cortex (Brodmann's area 6 (BA6)), frontal cortex, and superior frontal gyrus (BA10).  

However, converging results indicated that this ipsilateral PcG activity was situated in Brodmann's area 6 in both hemispheres.  

The purpose of this study was to ascertain whether activation differences could be identified in stable schizophrenic patients on the basis of BOLD measures in two motor regions, the primary motor cortex, Brodmann area 4 (BA4) and the premotor and supplementary motor area, Brodmann area 6 (BA6).  

The primary motor cortex (area 4) influences kinematic and dynamic parameters of movements, whereas the rostrally adjoining nonprimary motor cortex (area 6) uses external (e.g., sensory) or internal cues to trigger and guide movements. Once thought to be homogeneous, data from nonhuman primates have shown that area 6 is a mosaic of areas, each with distinct structural and functional properties: the supplementary motor areas "SMA proper" and "pre-SMA" on the mesial cortical surface, and the dorso- and ventrolateral premotor cortex on the cortical convexity. The rostral border of area 6 is very important for functional neuroimaging studies in humans since it separates the "motor domain" of the supplementary motor/premotor cortex from the "cognitive domain" of the prefrontal cortex. The brains were serially sectioned at 20 micro M and area 6 was defined by subjective and objective cytoarchitectonic analysis. Each brain's histological volume (with the representation of area 6) was reconstructed in 3-D and spatially normalized to the reference brain of a computerized atlas. The ten normalized volumes were superimposed and a population map was generated that describes, for each voxel, how many brains have a representation of area 6. On the mesial coetical surface, the rostral border of area 6 lies rostral to the anterior commissure-- though the distance varies across different brains. No macroanatomical landmark indicates the border between area 6 and the prefrontal cortex. The question whether a motor task engages only the "motor domain" of the supplementary motor/premotor cortex or in addition the "cognitive domain" of the prefrontal cortex can only be answered by superimposing the functional activation map with the microstructural population map of area 6..  

that imagery of hand movements specifically activates the hand sections of the contralateral primary motor cortex (area 4a) and the contralateral dorsal premotor cortex (area 6) and a hand representation located in the caudal cingulate motor area and the most ventral part of the supplementary motor area; 2). that when imagining making foot movements, the foot zones of the posterior part of the contralateral supplementary motor area (area 6) and the contralateral primary motor cortex (area 4a) are active; and 3).  

They also brought forward evidence that the dorsolateral premotor cortex (Brodmann's areas 6 and 8) serves as the substrate of the 'motor execution' process, and the mesial frontal cortex (Brodmann's area 6) serves as the substrate of the 'motor planning' process.  

We studied potentials that were recorded in a time window in which P300 usually could be recorded on the scalp and that were directly recorded from brain structures involved in motor control: the primary motor cortex (MC, Brodmann's area 4); the lateral and mesial (SMA) premotor cortices (Brodmann's area 6); and the basal ganglia.  

The superior sector of Brodmann area 6 (dorsal premotor cortex, PMd) of the macaque monkey consists of a rostral and a caudal architectonic area referred to as F7 and F2, respectively.  

Activity of the inferior precentral sulcus (area 6/44) showed stimulus-type effect particularly for the imagery mode.  

An occlusion of the middle trunk immediately before its partition gave rise to a symmetrical bilateral parasagittal lesion that damaged the supplementary motor areas (medial part of Brodmann's area 6), sparing the lateral regions including the premotor cortices, the corpus callosum and the gyri cinguli.  

Contralateral inferior area 6 and bilateral parietal area 40 revealed higher cluster volumes.  

The non-primary motor cortex (Brodmann's area 6) lies further rostrally and can be subdivided into three groups of areas: the supplementary motor areas "SMA proper" (area F3) and "pre-SMA" (area F6) on the mesial cortical surface, the dorsolateral premotor cortex (areas F2 and F7) on the dorsolateral convexity, and the ventrolateral premotor cortex (areas F4 and F5) on the ventrolateral convexity.  

By contrast, motor cortex activation in writing tremor also included the contralateral premotor area (area 6) and ipsilateral prefrontal area (inferior frontal gyrus; areas 10, 44, and 47).  

Complex finger opposition localized the ipsilateral premotor cortex (Brodman area 6) robustly and was introduced to preoperative fMRI in hemiparetic patients as functional landmark to identify the precentral gyrus on the tumors side.  

The activation in M1 engaged areas 4a and 4p and expanded into area 6.  

Brain regions where levels of rrCBF correlated with task complexity included lateral premotor cortex (area 6), rostral anterior cingulate cortex (areas 32 and 24), dorsolateral prefrontal cortex (areas 9 and 46) bilaterally, and right dorsal caudate nucleus.  

Among these multiple spatial areas, the ventral intraparietal cortex, the putamen and the ventral aspect of the premotor cortex (area 6) contain a system for representing visual space near the face (peripersonal space).  

Superior area 6 of the macaque monkey frontal cortex is formed by two cytoarchitectonic areas: F2 and F7. It is concluded that at least three separate parietofrontal circuits link the superior parietal lobule with the superior area 6.  

Although undetected in previous imaging-studies using CVS, involvement of these areas could be predicted from anatomic data showing projections from the anterior ventral part of area 6 to the inner vestibular circle and the vestibular nuclei.  

The assessment of the incidence of Tu-SA in area 6 revealed that only 5 of 26 PSP cases lacked Tu-SA in the examined fields.  

In addition, major neuronal loss was confined to the premotor cortex and the anterior half of the precentral gyrus (area 6), which apparently explained the aphemia.  

The frontal lobe accommodates an extension of the primary motor (precentral) cortex, the premotor region and the interhemispherically located supplementary motor region, both of them forming area 6 and its subdivisions.  

The ipsilateral premotor area (Brodmann area 6), bilateral posterior parietal areas (Brodmann area 7) and precuneus showed an increase in rCBF related only to the length of the sequences, without any change from rest to simple repetitive movement.  

The results for comparison '1' indicated activity in the contralateral prefrontal (area 10/46/44), bilateral inferior parietal (area 40) and ipsilateral premotor cortices (area 6), possibly reflecting initial orientation and plans for movement.  

For the nonspatial rule, performance of the evaluation task led to a learning-related increase in rCBF in a caudal and ventral part of the premotor cortex (PMvc, area 6), bilaterally, as well as in the putamen and a cingulate motor area (CM, area 24) of the left hemisphere. Decreases in rCBF were observed in several areas: the left ventro-orbital prefrontal cortex (PFv, area 47/12), the left lateral cerebellar hemisphere, and, in the right hemisphere, a dorsal and rostral aspect of PM (PMdr, area 6), dorsal PF (PFd, area 9), and the posterior parietal cortex (area 39/40). For the spatial rule, no rCBF change reached significance for the evaluation task, but in the conditional motor task, a ventral and rostral premotor region (PMvr, area 6), the dorsolateral prefrontal cortex (PFdl, area 46), and the posterior parietal cortex (area 39/40) showed decreasing rCBF during learning, all in the right hemisphere.  

The primary motor cortex, lateral area 6, cerebellum on both sides, and caudal cingulate motor area, and the putamen and thalamus on the contralateral side were more active during the metronome-paced movements.  

SMI-32 immunoreactivity technique provides 'neurofilament architecture' patterns specific to area 4, caudal area 6 (area 6c) and rostral area 6 (area 6r). Particularly, the distinction between the two subdivisions of area 6, which is difficult to appreciate with the usual cytochemical or enzyme architectonic techniques, appears very apparent with this technique. Hence, it was possible to localize the topographic boundaries of area 6a alpha and 6a beta of the Vogts on the dorso-lateral convexity and the supplementary motor area and the presupplementary motor area on the mexial wall of the hemisphere..  

Specifically, neocortical activations were observed in the right anterior cingulate gyrus (Brodmann area 24), in the intraparietal sulcus of right posterior parietal cortex, and in the mesial and lateral premotor cortices (Brodmann area 6)..  

In these ten years, connections have been described between the insula and the orbital cortex, frontal operculum, lateral premotor cortex, ventral granular cortex, and medial area 6 in the frontal lobe.  

We studied the functional properties of neurons in the caudal part of inferior area 6 (area F4) in awake monkeys.  

The right dorsal premotor cortex (Brodmann area 6) and the right precuneus (Brodmann area 7) showed a linear increase of rCBF as sequence complexity increased.  

We recorded electrical activity from 532 neurons in the rostral part of inferior area 6 (area F5) of two macaque monkeys.  

Our results suggest that ENM is generated by epileptic activity in the premotor area in the middle frontal gyrus corresponding to Brodmann's area 6..  

The OMPFC was also connected to premotor cortex in ventral area 6 (areas 6va and 6vb), in cingulate area 24c, and probably in the supplementary eye field. area 6va projected to area 12m, whereas a region of area 6vb projected to area 13l.  

Since lesions of the superior parietal lobule in humans produce deficits in visual localization of targets as well as in arm-reaching for them, and taking into account that the monkey's area PO (V6) is reported to be connected with the premotor area 6, we suggest that area PO (V6) supplies the premotor cortex with the visuo-spatial information required for the visual control of arm-reaching movements..  

Several other cortical regions known to be involved in visuospatial and visuomotor functions were also activated by the coherent movement, including the frontal eye field (Brodmann area 8) and premotor cortex (Brodmann area 6) in the frontal lobe.  

For example, the premotor area 6 can be distinguished from prefrontal areas by its high concentration of adrenergic alpha 1 receptors as labelled with [ 3H] prazosin, with only the cingulate area 24 showing higher values.  

In contrast to the dorsal premotor area (PMd, dorsolateral area 6), in both the caudate nucleus and putamen a larger proportion of the neuronal sample reflected both movement direction and stimulus attributes.  

The cortical connections of the dorsal (PMd) and ventral (PMv) subdivisions of the premotor area (PM, lateral area 6) were studied in four monkeys (Macaca fascicularis) through the use of retrograde tracers.  

Besides these polysensory vestibular cortical fields, three other circumscribed cortical regions of the macaque brain were also found to project directly to the brainstem vestibular nuclei: a circumscribed part of the postarcuate premotor cortex (area 6pa), part of the agranular and the adjacent dysgranular cortex located around the cingulate sulcus (area 6c/23c), and a predominantly visual (optokinetic) association field located at the fundus of the lateral sulcus (area T3). The ventrolateral nucleus, which sends efferent axons to both the oculomotor and skeletomotor systems of the brainstem and the spinal cord, also receives its main cortical efferents from the somatomotor area 6 and from area 3aV.  

The monkey mesial area 6 comprises two distinct cytoarchitectonic areas: F3 [ supplementary motor area properly defined (SMA-proper)], located caudally, and F6 (pre-SMA), located rostrally.  

Similar distributions of four PKC subspecies were seen in Brodmann's area 6, except that beta I-PKC immunoreactive Betz cells were not present.  

M1 resembles Brodmann's area 4, although the rostral subdivision has probably been considered as part of area 6 by some workers.  

Axons of premotor cortex (dorsolateral and post-arcuate area 6) passed through the capsular genu, and those of supplementary motor area (mesial area 6) through the anterior limb.  

Previous reports have argued that single neurons in the ventral premotor cortex of rhesus monkeys (PMv, the ventrolateral part of Brodmann's area 6) typically show spatial response fields that are independent of gaze angle.  

In addition to the well-known pallido-thalamo-cortical projection to area 6, some thalamic neurons with CN input were found to project to area 6.  

Lesion analysis by means of a neuroanatomic template placed a 2-cm region of encephalomalacia anterior to the left central sulcus in premotor cortex (Brodmann's area 6). Reading epilepsy may be a reflex or action myoclonus syndrome localized to Brodmann's area 6 (Exner's area)..  

Many neurons in inferior area 6, a cortical premotor area, respond to visual stimuli presented in the space around the animal. To this purpose we recorded single neurons from inferior area 6 (F4 sector) in a monkey trained to fixate a light and detect its dimming. The results showed that most inferior area 6 visual neurons code the stimulus position in spatial and not in retinal coordinates.  

Recent cytoarchitectonic, histochemical and physiological studies have shown that the lateral part of area 6 (the premotor cortex) of macaque monkeys can be divided into at least two subregions, each of which is considered to play an important role in motor control. When WGA-HRP was injected into the region immediately lateral to the superior precentral sulcus within the PMd, retrogradely labeled neurons were found in area 6 lying in the mesial wall possibly corresponding to the supplementary motor area (SMA), areas 24 and 23 of the cingulate cortex, rostral region of area 4, and area 5 (area PEa).  

The lateral region of the frontal lobe of the baboon consists of broad areas of motor (area 4), premotor (area 6), and the dorsolateral prefrontal cortex, each of which is further divided into subdivisions with distinct cytoarchitectural features: areas 4a, 4b, 4c; 6 a alpha, 6a beta, 6a gamma, and 6b beta; 8A and 8B; 45; 46 and 46ps; 9; 10; and 12. Although the frontal cortex of the baboon brain exhibits the same basic cytoarchitectural features as the frontal corticies of the cercopithecus (campbelli?) (Vogt and Vogt, '19) or the macaque (Walker, '40; Barbas and Pandya, '87, '89), the baboon frontal cortex is very different from that of the macaque and cercopithecus in terms of cytoarchitecture: (1) the baboon frontal cortex has an additional area, termed here "6a gamma", within area 6, which has cytoarchitectural characteristics that are intermediate between those of areas 6 and 8; (2) the aggregation of giant pyramidal cells (greater than 50 microns in diameter) is found only in area 4a in the baboon, whereas such aggregates are found in areas 4a and 4b and, occasionally, in area 4c in the macaque; and (3) area 46 of the prefrontal cortex of the baboon can be subdivided into the cortex that surrounds the principal sulcus (area 46) and the upper and lower banks of the principal sulcus (area 46ps). The frontal cortico-cortical connections of areas 46, 8, 6, and 4 in the hamadryas baboon were organized as follows: (1) areas 46, 8, and 6 were connected to one another, (2) area 4 was connected only to area 6, and (3) these connections showed a gross ventrodorsal topography: the ventral regions of each of areas 46, 8, and 6 were connected more strongly to the ventral than the dorsal regions of the other areas; the dorsal regions of each of areas 46, 8, and 6 were connected more strongly to the dorsal than the ventral regions of the other areas.(ABSTRACT TRUNCATED AT 400 WORDS).  

The activity of 156 individual arm-related neurons was studied in the premotor cortex (area 6) while monkeys made arm movements of similar directions within different parts of 3-dimensional space.  

The premotor areas are located in parts of cytoarchitectonic area 6 on the lateral surface and medial wall of the hemisphere, as well as in subfields of areas 23 and 24 in the cingulate sulcus.  

The activity of 156 neurons was recorded in the premotor cortex (Weinrich and Wise 1982) and in an adjoining rostral region of area 6 (area 6 DR; Barbas and Pandya 1987) while monkeys made visually-guided arm movements of similar direction within different parts of space.  

In the frontal lobe, Cat-301-positive neurons were intensely immunoreactive and present in large numbers in the motor cortex (area 4), premotor cortex (area 6, excluding its lower ventral part), the supplementary motor area (SMA), and the caudal prefrontal cortex (areas 8a, 8b and 45).  

Projections from area 6 a beta to the centromedian and parafascicular nuclei are slightly more numerous than those arising in 6 a alpha.  

The corticocortical connections between the arcuate area (Walker's areas 8A and 45 or Brodmann's area 8) and the premotor and supplementary motor areas (Vogts' area 6) in the brain of the macaque monkey were studied microscopically with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), which was injected into Brodmann's area 8 primarily to elucidate the projections of area 8 into area 6.  

In both the ipsilateral and contralateral hemispheres, the premotor (lateral area 6) and supplementary motor (medial area 6) areas dominate quantitatively the inputs to the motor cortical representation of the forelimb.  

The premotor cortex (area 6) has several architectonic sectors that can be delineated on the basis of cytoarchitectonic and myeloarchitectonic features. area 6 may be broadly subdivided into a dorsal and a ventral sector at the spur of the arcuate sulcus. Dorsal area 6 is further subdivided into a caudal and a rostral sector on the basis of the presence of large pyramidal cells in the caudal but not in the rostral sector. The rostral sector of area 6 can be subdivided into a medial region distinguished from a more laterally situated area by the presence of more compact and darkly stained cells in layers III and V. Ventral area 6 can be subdivided into an upper and lower division. The efferent and afferent connections of area 6 were studied with anterograde and retrograde tracers. The frontal connections of dorsal area 6 are restricted to neighboring dorsal frontal regions. Only the caudal sector of dorsal area 6 is connected with the motor cortex. In contrast, ventral area 6 is not only connected with the prefrontal cortex, but also directly with the motor cortex, the parainsular gustatory area, and with somatosensory areas in the frontal operculum. The widespread connections of ventral area 6 may be related to the specialization of the head, neck, and face structures that are represented ventrally within the premotor cortex..  

The dorsolateral portion of the VA-VL complex primarily showed reciprocal connections with the medial premotor (area 6) cortex.  

Reciprocal corticocortical connections were observed primarily with the supplementary motor area (SMA) in medial premotor area 6 and dorsal bank of the cingulate sulcus, postarcuate area 6 cortex, dorsal cingulate cortex (area 24), superior parietal lobule (area 5, PE/PEa), and inferior parietal lobule (area 7b, PF/PFop, including the secondary somatosensory SII region). The bilateral connections with premotor frontal area 6 and cingulate cortices were not observed with parietal regions; i.e., only ipsilateral intrahemispheric parietal corticocortical connections were observed.  

A few premotor units (area 6) were also examined; they showed either type III (n = 12) or type IV (n = 2) activity.  

Bilateral cooling of the premotor cortex (the dorsolateral part of presumed area 6) disorganized the well-trained reaction-time movement, in which a lever was lifted within duration of the light stimulus (about 0.5 s) delivered at random time intervals.  

In a subsequent study, bilateral lesions to premotor cortex (area 6) resulted in an impaired ability to follow a route using either proprioceptive or external cues..  

area 6a beta receives fibers from the ventromedial part of the VL, area 6a alpha from the medial part, and area 6iffu from the dorsomedial part. Area 4 receives fibers from the ventrolateral part of the VA, while area 6 receives fibers from its dorsomedial part. area 6 receives a few fibers from the submedial and ventral medial nuclei..  

Most of these neurones were located in cortical area 6, close to the arcuate curvature and its spur, but also more caudally in area 4 and rostrally in area 8.  

We have found that neurones in medial area 6 (SMA) and in lateral area 6 (PMC) may likewise be activated by such kinesthetic stimuli, at latencies which are only slightly longer than in area 4.  

Even small HRP injections into the superficial layers of the superior colliculus yielded labelled cells in the agranular cortex (area 6) of the anterior bank of the arcuate sulcus.  

It is concluded that the frontal cortical organization of externally triggered purposeful movements is made possible by the associative character of Brodmann's area 6 and by its peculiar pattern of intra-areal connectivity..  

Analysis of the thalamus in cases with fluorescent dye injections into the lateral orbital gyrus (Walker's area 11), principal sulcus (area 46), anterior bank of the arcuate gyrus (areas 8 and 45), supplementary motor area (area 6), and motor cortex (area 4) revealed topographic organization of the nigrothalamocortical projection system.  

Single cell recordings were made from the premotor cortex (lateral part of area 6) of a monkey trained to perform either a distal hindlimb or forelimb movement separately.  

Very little or no overlap was found after injections of the premotor cortex (area 6), the visual areas 17, 18 and 19 and the auditory cortex (AI and AII).  

After HRP injections restricted primarily to the superficial layers of the colliculus, labelled cells were found in visual cortex (areas 17, 18, and 19) and both in the frontal eye field (area 8) and the adjacent part of premotor cortex (area 6). When intermediate and deeper layers of the colliculus were injected, labelled cells were found also in posterior parietal cortex (area 7) where they were concentrated mainly on the posterior bank of the intraparietal fissure, in inferotemporal cortex (areas 20 and 21), in auditory cortex (area 22), in the somatosensory representation SII (anterior bank of sylvian fissure, area 2), in upper insular cortex (area 14), in motor cortex (area 4), in premotor cortex (area 6), and in prefrontal cortex (area 9). The size spectrum of corticotectal cells ranged from 14.8 micron (average diameter) in area 17 to 27.8 micron in area 6, comprising cells as small as 8 micron and as large as 45 micron. Those in premotor cortex (area 6) were often large and had a wide range in size distribution.  

Four additional capuchin monkeys, one rhesus (Macaca mulatta), and one cynomolgus (Macaca fascicularis) monkey, received HRP gel implants in premotor (area 6), frontal eye field (FEF, area 8), superior (area 5), and inferior (area 7) parietal lobules to orthogradely label the course and termination of corticopontine projections, and thus to confirm the retrograde studies. Premotor (area 6) frontal cortex and FEF (area 8) were found to be the main sources of cortical inputs to the ipsilateral paramedian basilar pons, whereas FEF, dorsal prefrontal convexity, and dorsal medial prefrontal (granular frontal association) cortex were the main sources of bilateral projections to the paramedian pontine tegmentum.  

Both retrograde and anterograde studies confirmed that the prearcuate cortex in the concavity of the arcuate sulcus, including the frontal eye field, and, to a lesser extent, suprarcuate rostral dorsal area 6 cortex and the dorsomedial convexity (area 9), project to the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) in the dorsal region of the prerubral field, nucleus of Darkschewitsch (ND), medial accessory nucleus of Bechterew (NB) and dorsomedial parvocellular red nucleus (dmPRN). The premotor area 6 and motor area 4 cortex, on the other hand, give rise to projections that target a larger portion of the parvocellular red nucleus, extending rostrally into the ventral region of the prerubral field, and a rather intense projection to the ND.  

In monkeys (Macaca fuscata), horseradish peroxidase (HRP) was injected in the mesial part of area 6a alpha and 6a beta of the Vogts (presumed supplementary motor area). These connections are similar to those of the dorsolateral part of area 6 (premotor area) with some topographical differences..  

The corticomagnocellular (CRm) projection arises principally from cells in sublamina Vb of the precentral arm and leg areas (area 4), and from adjacent parts of posterior area 6, CRm cells are pyramidally shaped, and their size distribution is bimodal, with peaks that correspond, respectively, to the modal diameters of CRp and of corticospinal neurons.  

We have found that the dorsal, magnocellular division of the basal nucleus of the amygdaloid complex gives rise to a projection to the premotor cortex (area 6), which terminates principally in layers I and II, and to a lesser extent in layer VI. The amygdaloid projection to area 6 in the monkey appears to be substantially weaker than other rostrally directed projections from the basal amygdaloid nucleus to orbitofrontal and medial frontal areas, and also relatively weaker than the projection that has been described in the cat..  

No projection has been found from area 6 (premotor) or from area 7 (caudal parietal).  

In the conscious, behaving monkey trained to perform a motor task either self-paced or involving light cues, a restricted area responsive during performance of the task can be found in cytoarchitectonic area 6 at the level of the concavity of the arcuate sulcus.  

Stimulation of the interpositus and dentate nucleus evoked contralaterally surface negative-depth positive potentials (superficial T-C responses) in the intermediate and lateral part of the motor cortex and in the premotor cortex (area 6) with a latency of 3 to 4 ms.  

Stimulation of contra- and ipsilateral parts of precruciate cortex (area 6) evoked selective long-lasting facilitation with aftereffect without involving extrafusal muscle fibres. The independent action of areas 6 and 4 on muscle spindle activity indicates a specific role of area 6 in regulation of segmentary activity of the gamma-system..  

Significant potentials in response to the light stimulus were found first in the frontal and occipital association cortices (area 8-10 and 19), and then in the premotor cortex (area 6) on bilateral sides.  

These results suggest that the premotor cortex (area 6) participates in the more general and associative organization of motor function than the motor cortex (area 4) which represents the specialized role in the motor performance..  

The anterior cerebral artery supplies most of cortical area 6 (premotor cortex), the intrafundal cruciate and medial postcruciate cortex, (hindlimb motor cortex), and the midline and medial portions of the sensory areas 3a-7.  

In the cerebral cortex ipsilateral to the HRP-injected side, labelled cells belonging to the smaller group were distributed mostly in area 6 and occasionally in areas 4 and 5. Labelled cells belonging to the larger group were located exclusively in area 6. In the contralateral cortex, labelled cells were all smaller in size and distributed only in area 6. The results of the present study indicate the existence of a close relationship between area 6 (premotor area) of the cerebral cortex and the caudate nucleus..  

Stimulation of the cerebellar dentate nucleus in monkeys elicited responses in the frontal association cortex (area 9) on the contralateral side to the stimulation, in addition to those in the motor (area 4) and premotor (area 6) cortices which were reported previously. In the rostral part of the premotor cortex (area 6) on the border of area 9, both types of responses were induced and admixed.  

The heaviest contralateral projection was recorded from the medial hemispheric aspects of area 6 (partly identical with the supplementary motor cortex).  

Dentate neurons receive their strongest and most numerous inputs from the premotor and supplementary motor regions of area 6.  

From these findings, it was indicated that the Cd receives collaterals of the cortico-pontine and/or the cortico-olivary axons that originated almost exclusively from the neurones in the medial ASG (area 6).  

The strongest inputs to interpositus neurons are from motor and somatosensory cortex, with weaker inputs from peripheral nerves and cerebral area 6.  

Stimulation of the lateral (dentate) cerebellar nucleus elicited, at a latency of about 3 msec, superficial T-C responses (surface negative-deep positive potentials) predominately in the lateral part of the precentral gyrus (area 4, "motor area for forelimb and face") and in the rostromedial part of the gyrus (area 6, premotor area) on the contralateral side.  

An overlap of responsive zones to stimulation of the dorsal prefrontal convexity and the premotor area (area 6) was found in the dorsolateral part of the rostral caudate, while a zone of overlap of responses to stimulation of the ventral prefrontal convexity and "hand" motor area of the precentral gyrus was found in the ventromedial area of the putamen near the commissural level..  

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