Abstract
The macaque monkey superior parietal lobule (SPL) is part of a neuronal network involved in the integration of information from visual and somatosensory cortical areas for execution of reaching and grasping movements. We applied quantitative in vitro receptor autoradiography to analyse the distribution patterns of 15 different receptors for glutamate, GABA, acetylcholine, serotonin, dopamine, and adenosine in the SPL of three adult male Macaca fascicularis monkeys. For each area, mean (averaged over all cortical layers) receptor densities were visualized as a receptor fingerprint of that area. Multivariate analyses were conducted to detect clusters of areas according to the degree of (dis)similarity of their receptor organization. Differences in regional and laminar receptor distributions confirm the location and extent of areas V6, V6Av, V6Ad, PEc, PEci, and PGm as found in cytoarchitectonic and functional studies, but also enable the definition of three subdivisions within area PE. Receptor densities are higher in supra- than in infragranular layers, with the exception of kainate, M2, and adenosine receptors. Glutamate and GABAergic receptors are the most expressed in all areas analysed. Hierarchical cluster analyses demonstrate that SPL areas are organized in two groups, an organization that corresponds to the visual or sensory-motor characteristics of those areas. Finally, based on present results and in the framework of our current understanding of the structural and functional organization of the primate SPL, we propose a novel pattern of homologies between human and macaque SPL areas.
Highlights
The movement of the limbs necessary to reach or grasp objects requires the integration in the cerebral cortex of motor signals with visual and somatosensory stimuli
The superior parietal lobule (SPL) of the macaque monkey is recognized as an associative cortex, as it is part of a neuronal network involved in the association of information coming from frontal and visual cortices useful to plan and control the execution of reaching and grasping movements (Galletti and Fattori 2018; Galletti et al 2003; Goodale and Milner 1992; Rizzolatti and Matelli 2003)
The congruity between the curve representing the mean Grey Level Index (GLI) and those indicating the s.d. values highlights the ideal plane of sectioning of the site selected for GLI measurement
Summary
The movement of the limbs necessary to reach or grasp objects requires the integration in the cerebral cortex of motor signals with visual and somatosensory stimuli. The superior parietal lobule (SPL) of the macaque monkey is recognized as an associative cortex, as it is part of a neuronal network involved in the association of information coming from frontal and visual cortices useful to plan and control the execution of reaching and grasping movements (Galletti and Fattori 2018; Galletti et al 2003; Goodale and Milner 1992; Rizzolatti and Matelli 2003). This brain region hosts several cyto- and myelo-architectonically defined areas. Other areas seem to have a corollary role in this sensory-motor network, as area PGm is mainly involved in oculomotor activity, spatial navigation (Leichnetz 2001; Olson et al 1996; Passarelli et al 2018; Thier and Andersen 1998), and visually guided limb movements (Ferraina et al 1997; Passarelli et al 2018), and area
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