Abstract
We studied the thalamic afferents to cortical areas in the precuneus using injections of retrograde fluorescent neuronal tracers in four male macaques (Macaca fascicularis). Six injections were within the limits of cytoarchitectural area PGm, one in area 31 and one in area PEci. Precuneate areas shared strong input from the posterior thalamus (lateral posterior nucleus and pulvinar complex) and moderate input from the medial, lateral, and intralaminar thalamic regions. Area PGm received strong connections from the subdivisions of the pulvinar linked to association and visual function (the medial and lateral nuclei), whereas areas 31 and PEci received afferents from the oral division of the pulvinar. All three cytoarchitectural areas also received input from subdivisions of the lateral thalamus linked to motor function (ventral lateral and ventral anterior nuclei), with area PEci receiving additional input from a subdivision linked to somatosensory function (ventral posterior lateral nucleus). Finally, only PGm received substantial limbic association afferents, mainly via the lateral dorsal nucleus. These results indicate that area PGm integrates information from visual association, motor and limbic regions of the thalamus, in line with a hypothesized role in spatial cognition, including navigation. By comparison, dorsal precuneate areas (31 and PEci) are more involved in sensorimotor functions, being akin to adjacent areas of the dorsal parietal cortex.
Highlights
The term precuneate gyrus refers to the region of cortex located on the medial surface of the parietal lobe, which is anatomically circumscribed by the parieto-occipital, suprasplenial and cingulate sulci
The number of labelled neurons in the cortex and thalamus varied between cases (Table 1), likely reflecting both differences in tracer sensitivity and in the extent of injections (Fig. 1); in particular, our analysis showed that the number of observed labelled cells is related to the size of the injection site (Fig. 1, inset c; Pearson’s r = 0.757, p
Observe variability in some of the thalamic projections to PGm; for example, projections from the limbic lateral dorsal nucleus, the ventral lateral nucleus and the lateral pulvinar targeted strongly specific parts of PGm (Table 3), hinting at a complex pattern of organization that cannot be fully captured by traditional notions of homogeneous cortical and thalamic connections throughout the borders of this architectural field (Passarelli et al 2018)
Summary
The term precuneate gyrus (or precuneus) refers to the region of cortex located on the medial surface of the parietal lobe, which is anatomically circumscribed by the parieto-occipital, suprasplenial and cingulate sulci. There is evidence showing that, in monkeys, the precuneus forms extensive connections with superior and inferior parietal, cingulate and retrosplenial areas of the cortex, whereas connections with the frontal lobe are somewhat deemphasized when compared to adjacent superior parietal areas (Pandya and Seltzer 1982; Cavada and Goldman‐Rakic 1989a, b; Leichnetz 2001; Parvizi et al 2006; Passarelli et al 2018) In this aspect, the precuneus appears to be a node, or intermediary structure, in the parieto-medial temporal pathway with access to the hippocampal and parahippocampal formations, suggesting a role in whole-body movements and spatial memory (Kravitz et al 2011). These data add to a recent body of quantitative descriptions of the subcortical input to the caudomedial lobe (Buckwalter et al 2008; Gamberini et al 2016; Impieri et al 2018) and allow us to look for specific functional trends within this large cortical region
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
