Cortical and thalamic projections to cytoarchitectural areas 6Va and 8C of the marmoset monkey: Connectionally distinct subdivisions of the lateral premotor cortex

Abstract

We studied the afferent connections of two cytoarchitectural subdivisions of the caudolateral frontal cortex, areas 6Va and 8C, in marmoset monkeys. These areas received connections from the same set of thalamic nuclei, including main inputs from the ventral lateral and ventral anterior complexes, but differed in their patterns of corticocortical connections. Areas 8C and 6Va had reciprocal interconnections, and received similar proportions of afferents from premotor areas 6M and 6DC, and from the prefrontal cortex. However, area 8C received stronger inputs from frontal areas that have been implicated in oculomotor functions, whereas area 6Va received stronger projections from the primary motor area. Somatosensory projections to area 6Va were generally stronger than those to area 8C, and originated from several areas; in contrast, only the second somatosensory area (S2) sent major inputs to area 8C. Finally, although both 6Va and 8C received major inputs from the rostral posterior parietal cortex (putative homologs of areas PE, PF, and PFG), area 8C also received a variety of smaller connections from posterior midline, caudal posterior parietal, and extrastriate areas. Statistical analyses revealed that the pattern of connections of area 8C is more akin to that characterizing a premotor area, rather than a prefrontal area. We conclude that cytoarchitectural area 6Va in the marmoset is similar to ventral premotor areas identified in other simian primates, and that area 8C corresponds to a specialized subdivision of the caudal premotor complex where visual information for the guidance of movements is likely to be emphasized.

Distinct Neural Activities in Premotor Cortex during Natural Vocal Behaviors in a New World Primate, the Common Marmoset (Callithrix jacchus)

“…4B), future experiments are needed to determine how these categories vary between the premotor and primary motor cortices. Conversely, within motor cortices, somatotopic representations of orofacial regions are located in the ventral area (Burish et al, 2008;Burman et al, 2008Burman et al, , 2015. Our observations of vocal-only and vocal-orofacial neurons in dorsal premotor cortex suggest that vocalization related motor control may not be limited to the orofacial regions identified by electrical stimulation in anesthetized marmosets (Burish et al, 2008;Burman et al, 2008).…”

The cortical motor system of the marmoset monkey (Callithrix jacchus)

“…To some extent, variations in the exact composition of inputs to different parts of M1 also reflect its topographic organization, with specific emphases on connections to the regions of head, forelimb and trunk/hindlimb musculature representations (Burman et al, 2014a). For instance, dense connections between lateral M1 and ventral premotor area 6Va in the marmoset might reflect components of a cortical circuit related to orofacial and head movements (Burman et al, 2008(Burman et al, , 2014c, as suggested previously in macaques (Matelli et al, 1986;Tokuno et al, 1997). Caudal areas 6DC and 6Va (Fig.…”

“…The same somatosensory areas target ventral premotor area 6Va, although emphasis is markedly shifted toward S2 (Burman et al, 2014c; Table 1 and Fig. 2, right).…”

Towards a comprehensive atlas of cortical connections in a primate brain: Mapping tracer injection studies of the common marmoset into a reference digital template

“…Another way of visualizing the results is by generating flattened, mid-thickness representations of the cortex, as commonly used to report results of the tracer injection studies (e.g. Rosa et al, 2009 ;Bakola et al, 2010Bakola et al, , 2013Passarelli et al, 2011 ;Burman et al, 2014Burman et al, , 2015. With this representation one can summarize, for example, the distribution of the cells across the cortex (Fig.…”

“…Fluorescence microscopy photomicrographs of the types of injection sites and quality of the cell filling obtained with these methods are shown in recent publications from our laboratory (e.g. Palmer and Rosa, 2006 ;Burman et al, 2011Burman et al, , 2015Reser et al, 2013 ). Estimates of injection extent for each case, drawn under microscopic examination, are available through the project's web site.…”