Abstract
The exposed surface of the superior parietal lobule in macaque brain contains two architectonically defined areas named PEc and PE. The aim of the present study is the characterization of thalamic afferents of these two areas. For this purpose, retrograde neuronal tracers were injected, or placed in crystal form, in areas PEc and PE. We found that the two areas show a similar pattern of thalamic inputs, mainly originating from Lateral Posterior (LP), Pulvinar (Pul), Ventral Posterior Lateral (VPL), and Ventral Lateral (VL) nuclei, all structures known to be involved in visual, somatosensory, and/or sensorimotor processing. Minor afferents were observed from the Centromedian/Parafascicular complex (CM/PF), Central Lateral (CL), Ventral Anterior (VA), and Medial Dorsal (MD) nuclei. LP and VL were more strongly connected to PEc than to PE, while the other main thalamic inputs to the two areas showed slight differences in strength. The part of the Pul mostly connected with areas PEc and PE was the Medial Pul. No labeled cells were found in the retinotopically organized Lateral and Inferior Pul. In the somatotopically organized VPL and VL nuclei, labeled neurons were mainly found in regions likely to correspond to the trunk and limb representations (in particular the legs). These findings are in line with the sensory-motor nature of areas PEc and PE, and with their putative functional roles, being them suggested to be involved in the preparation and control of limb interaction with the environment, and in locomotion.
Highlights
In macaques, the exposed surface of the superior parietal lobule contains two cytoarchitectural areas, named PEc and PE (Pandya and Seltzer, 1982), which are functionally distinct
The number of labeled neurons in cortex and thalamus differed between cases likely because of the different type of tracer used, the different uptake of the tracer in different cases, and/or the different cortical layers involved by the injection site
Four parasagittal sections through the thalamus are shown, together with a reconstruction of a medial view of the thalamus, which shows the most densely labeled thalamic nuclei obtained by overlapping outlines deriving from all sections available
Summary
The exposed surface of the superior parietal lobule contains two cytoarchitectural areas, named PEc and PE (Pandya and Seltzer, 1982), which are functionally distinct. Area PEc, which overlaps with the most caudal and medial part of Brodmann’s area 7 (Brodmann, 1909; Luppino et al, 2005; Gamberini et al, 2015), forms an incomplete map of the body, principally focused on the limbs, without any evident sign of topographical organization (Breveglieri et al, 2006, 2008). Area PE, which overlaps with Brodmann’s area 5 (Brodmann, 1909), contains a rough topographical representation of the body, with over-representation of the arms and hands (Taoka et al, 1998, 2000; Padberg et al, 2007; Krubitzer and Disbrow, 2008; Seelke et al, 2012). PE neurons are involved in the preparation and control of limb movements (Burbaud et al, 1991; Ferraina and Bianchi, 1994; Lacquaniti et al, 1995; Kalaska, 1996; Ferraina et al, 2009; Bremner and Andersen, 2012), and become active during skilled actions (Maimon and Assad, 2006; Chen et al, 2009; Shi et al, 2013)
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