Differential visuomotor and somatosensory claustral inputs to macaque medial posterior parietal cortex

Abstract

The macaque medial posterior parietal cortex (mPPC) is involved in the analysis of sensory signals for the control of movement. Here, we describe the claustral input to the mesial and lateral part of mPPC, specifically areas PGm and MIP, and compare them with those of adjacent areas. Four injections of retrograde neuronal tracers were restricted to PGm and MIP and one injection each to areas V6Ad, 31, PEci, PEip, and LIP, in 10 hemispheres of 10 animals (7 Macaca fascicularis, 2 M. nemestrina, 1 M. mulatta). Injections were placed by direct visualization of regions of interest, and the location of injection sites was reconstructed post mortem on cyto- and myeloarchitectural bases. All examined parietal areas received monosynaptic afferents from the claustrum, predominantly from its posterior half. Injections in PGm, as well as in LIP, revealed a continuous stripe of labelled cells along the rostrocaudal extent of the claustrum: 50% of labelling occupied the postero-ventral part of the claustrum, while the remaining 50% was distributed in the antero-ventral (30%) and antero-dorsal (20%) part. Claustral projections to MIP were less homogeneous: posterior injections showed a similar pattern to PGm, even if anteriorly limited to the dorsal quadrant; rostral injections, likewise in V6Ad, showed projections in the posterior half of the claustrum, mainly within the postero-ventral quadrant. Claustral afferents to areas PEci and PEip were concentrated in the postero-dorsal quadrant, while afferents to area 31 were mainly in the postero-ventral quadrant, in a middle position between PGm and PEci afferents. The origin of claustral projections to posterior parietal areas reveals a functional topography within this structure: the postero-ventral and anterior claustrum are respectively related to visual and motor cognition (see projections to PGm and MIP), whereas the dorsal part of the claustrum is likely involved in somatic processing (projections to PEci and PEip).