Comparison of the distribution of parvalbumin-immunoreactive and other synapses onto the somata of callosal projection neurons in mouse visual and somatosensory cortex

Abstract

The distribution of synapses made by parvalbumin-immunoreactive (pv-ir) and nonimmunoreactive terminals was determined for the cell bodies of callosal projection neurons in the somatosensory and visual areas of mouse cerebral cortex. Callosal neurons were labeled by the retrograde transport of horseradish peroxidase applied to the contralateral hemisphere. The surface areas of somata belonging to callosal cells in somatosensory cortex ranged from 230 to 243 microm2 in size and received roughly one-third of their synapses from pv-ir terminals. Visual cortex, in contrast, contained two populations of callosal cell bodies: relatively large ones ranging in size from 255 to 279 microm2 that received 3-9% of their synapses from pv-ir terminals and smaller cell bodies that both in size (232-237 microm2) and in the proportion of synapses received from pv-ir terminals resemble the callosal cells examined in somatosensory cortex. That different functional areas of the cortex have populations of callosal cells similar in size, and displaying similar patterns of somatic synapses, supports the notion that a common plan of synaptic connectivity characterizes different functional areas. Results in visual cortex indicate that functional areas contain, in addition, area-specific patterns of synapses.

On Synchronizing Coupled Retinogeniculocortical Pathways: A Toy Model

“…For instance, according to Table 1 , the maxima of η 2 1 and η 2 10 occur for m = 27. By taking m = m ′ = m ′′ = 27, then 11% of synapses involving cortical neurons are thalamocortical ones and 5% are callosal ones, which are values compatible with those found in actual nervous systems [ 26 , 27 ]. Notice that the validity of our results relating the amounts of synaptic connections (the parameters m , m ′, and m ′′) to synchronous behaviors classified as η 1 k and η 2 k can be experimentally tested.…”

“…Interestingly, similar values can be found in literature. For instance, in mouse cortex, thalamocortical synapses are about 15% [ 26 ]; callosal synapses, about 5% [ 27 ]. One can conjecture that the values of m , m ′, and m ′′ found in actual visual pathways favor the occurrence of synchronization between LGN and VC, in order that the frequency observed in VC is equal, half, or a third of the one measured in LGN.…”

Development of NMDA NR2 subunits and their roles in critical period maturation of neocortical GABAergic interneurons

“…PV expression occurs at the CP in barrel and visual cortex (Alcantara and Ferrer, 1994; Yan et al, 1996; Czeiger and White, 1997; Maier and McCasland, 1997; Letinic and Kostovic, 1998; Hada et al, 1999; Moon et al, 2002). PV-cell network controls ocular dominance plasticity onset (Hensch, 2005; Sugiyama et al, 2008).…”

Diversity and Function of Somatostatin-Expressing Interneurons in the Cerebral Cortex

“…The axonal projections of basket cells remain largely within a given cortical layer where they can ramify extensively and target the majority of neighboring pyramidal neurons within a 100 µm radius [63]. Their name is derived from their basket-like presynaptic envelopes that they seem to wrap around the cell bodies of postsynaptic pyramidal neurons [64]. In terms of their morphology and size, basket cells are divided into large basket cells, small basket cells and nest basket cells, the specific properties of each of these subclasses not being discussed here.…”