Ipsilateral cortical connections of area 6 in the cat cerebral cortex

Abstract

Many motor areas have been identified within cytoarchitectonic area 6 of the cerebral cortex in primates. To provide a better understanding of the motor functions of area 6 in the cat, the ipsilateral cortical connections of the different cytoarchitectonic subdivisions of area 6 (areas 6a alpha, 6a beta, 6a gamma, and 6iffu) were studied by the use of fluorescent retrograde tracers. Tracer injections, made in the forelimb and face regions of areas 6a alpha and 6a gamma, were guided by data from intracortical microstimulation (ICMS). ICMS did not evoke movements from areas 6a beta and 6iffu. Retrogradely labeled neurons were enumerated in cytoarchitectonically identified areas in the frontal and parietal lobes to show that the subdivisions of area 6 are strongly interconnected except for areas 6a gamma and 6a beta. There are considerable differences in the pattern of connections of the area 6 subdivisions with area 4 and with prefrontal, cingulate, and parietal cortices. Area 4 gamma projects strongly to area 6a gamma but not to the other subdivisions. Areas 4 delta, 4fu, and 4sfu project strongly to 6a alpha and 6iffu but relatively weakly to area 6a beta. Prefrontal areas project strongly to area 6a beta and 6iffu, moderately to 6a alpha, but weakly to area 6a gamma. Cingulate areas project strongly to area 6iffu and moderately to areas 6a alpha and 6a beta but do not project to area 6a gamma. Parietal projections from primary and second somatosensory cortex were directed to area 6a gamma, whereas areas 5, 7, and insula were found to project to all the subdivisions of area 6. These findings support earlier suggestions that secondary motor areas may be located in areas 6a alpha and 6a gamma (Ghosh [1997] J. Comp. Neurol. 380:191-214). Features of the pattern of cortical connections of area 6 common to the cat and primates suggest that their motor areas in the frontal lobe are organized in a similar manner.

Motor cortical regulation of sparse synergies provides a framework for the flexible control of precision walking

“…At the cortical level, there are abundant references to show the richness of the cortico-cortical connections between both adjacent and more distant regions of cortex (Huntley and Jones, 1991; Schneider et al, 2002; Capaday et al, 2009, 2011; Smith and Fetz, 2009). In addition, the motor cortex receives abundant input from premotor cortex and from the posterior parietal cortex (Ghosh, 1997; Andujar and Drew, 2007), which might also serve to coordinate activity between different subpopulations of PTNs.…”

Widespread Distribution of Visual Responsiveness in Frontal, Prefrontal, and Prelimbic Cortical Areas of the Cat: An Electrophysiologic Investigation

“…Each of these thalamic cell groups are visually responsive (Hicks et al, 1984;Hutchins and Updyke, 1989), and all receive ascending tectothalamic projections (Graybiel, 1972;Graham, 1977;Huerta and Harting, 1984;Takada et al, 1985;Hicks et al, 1986). The cortex occupied by the insular visual area has been reported to project to areas 6a␤, 6a␣, 6a␥, and PFdl (Cavada and Reinoso-Suá rez, 1985;Nakai et al, 1987;Olson and Jeffers, 1987;Ghosh, 1997d), less heavily to areas 6if.fu, PFdm, PFr, PFv, 32, and 24 (Cavada and Reinoso-Suá rez, 1985;Guldin et al, 1986;Musil and Olson, 1988a,b;Ghosh, 1997d), and sparsely to areas 4␥ and 4␦ (Ghosh, 1997c).…”

“…It should be noted that interconnections between prefrontal and motor areas have also been reported. Area 32, PFdl, and PFdm project onto area 6a␤ (Room et al, 1985;Nakai et al, 1987;Olson and Jeffers, 1987;Ghosh, 1997d). Areas 6if.fu, 6a␤, and 6a␥ project upon area 6a␣ (Ghosh, 1997d).…”

“…Area 32, PFdl, and PFdm project onto area 6a␤ (Room et al, 1985;Nakai et al, 1987;Olson and Jeffers, 1987;Ghosh, 1997d). Areas 6if.fu, 6a␤, and 6a␥ project upon area 6a␣ (Ghosh, 1997d). Areas 4s.fu, 4fu, 6if.fu, 6a␣, and 6a␥ provide inputs to area 4␦; whereas areas 4␦ and 6a␥ provide inputs to area 4␥ (Ghosh, 1997c).…”

Premotor Cortex Provides a Substrate for the Temporal Transformation of Information During the Planning of Gait Modifications

“…Some of the subregions in area 6 and non-primary regions of area 4 have direct connections to M1 (Ghosh S 1997a(Ghosh S , 1997dAndujar J-E and T Drew 2007) as well as to the pontomedullary reticular formation (Berrevoets CE and HGJM Kuypers 1975;Matsuyama K and T Drew 1997;Rho M-J et al 1997) and some of these regions, including the non-primary motor regions of area 4, have been putatively identified as being analogous to the primate's PMC (Hassler R and K Muhs-Clement 1964;Avendaño C et al 1992;Ghosh S 1997d). Although it is tempting to postulate that these divisions are, indeed, analogous to the premotor areas of primates (Ghosh S 1997d;Nakajima T et al 2015) and that they are involved in planning motor activity, as in primates, there have been no systematic studies of the characteristics of cells in cat PMC during voluntary movements, including locomotion. Such studies are essential to determine whether cells in these different cytoarchitectonic regions discharge in a manner consistent with a contribution to planning movement.…”