Thalamocortical and corticothalamic connections of multiple functional domains in posterior parietal cortex of galagos

Abstract

In prosimian galagos, the posterior parietal cortex (PPC) is subdivided into a number of functional domains where long‐train intracortical microstimulation evoked different types of complex movements. Here, we placed anatomical tracers in multiple locations of PPC to reveal the origins and targets of thalamic connections of four PPC domains for different types of hindlimb, forelimb, or face movements. Thalamic connections of all four domains included nuclei of the motor thalamus, ventral anterior and ventral lateral nuclei, as well as parts of the sensory thalamus, the anterior pulvinar, posterior and ventral posterior superior nuclei, consistent with the sensorimotor functions of PPC domains. PPC domains also projected to the thalamic reticular nucleus in a somatotopic pattern. Quantitative differences in the distributions of labeled neurons in thalamic nuclei suggested that connectional patterns of these domains differed from each other.

Thalamic connections of the caudal part of the posterior parietal cortex differ from the rostral part in galagos (Otolemur garnettii)

“…The current report is a continuation of our previous study on the thalamic connections of PPCr in galagos (Wang et al., 2023). Here, we focused on the thalamic connections of PPCc in galagos and compared them with thalamic connections of PPCr.…”

“…Thalamic connections of different movement domains identified in the rostral portion of PPC of galagos have been published previously (Wang et al., 2023). The present study continues to look into patterns of thalamic connections of PPC in galagos, with a focus on its caudal part that is unresponsive to LT‐ICMS.…”

“…The concept of PPC domains was also corroborated by experiments with cortical deactivation and optical imaging methods (Cooke et al., 2015; Stepniewska et al., 2011, 2014, 2023). We further revealed distinct connectional patterns of different PPC domains by cortical injections of tracers, suggesting an anatomical basis for such functional distinctions in PPC (Gharbawie et al., 2010; Gharbawie, Stepniewska, & Kaas, 2011; Stepniewska, Cerkevich, et al., 2009; Wang et al., 2021, 2023).…”

“…We conducted a collection of studies to elaborate the functional organization of PPC in galagos, a representative of early strepsirrhine primates with many of the proposed cortical areas of other primates (e.g., Kaas, 2013;Wong & Kaas, 2010). Previous studies concerned cortical and thalamic connections of PPCr, as well as cortical connections of PPCc (Stepniewska et al, 2016;Stepniewska, Cerkevich, et al, 2009;Wang et al, 2021Wang et al, , 2023. To further reveal the global connections of PPCc, this follow-up study focused on its thalamic connections, as thalamic inputs provide and modulate information flow in the cortex (Sherman & Guillery, 2002).…”

The dorsal stream of visual processing and action‐specific domains in parietal and frontal cortex in primates

“…However, the activation of combinations of cortical motor primitives (movement domains) could yield a large repertoire of behavioral outcomes (Mussa‐Ivaldi & Bizzi, 2000). Such selection may start in the rostral region of PPC that receives inputs from the visually driven caudal half of PPC (Stepniewska et al., 2009a, 2016), higher order sensory and multisensory areas, as well as sensorimotor thalamus (Gharbawie et al., 2010; Wang et al., 2023; for review see Kaas & Stepniewska, 2016). Sensory stimuli drive one domain sooner, or greater, than the others that are then suppressed.…”