Bilateral hand representation in the postcentral somatosensory cortex

Abstract

In accordance with its important role in prehensile activity, a large cortical area is devoted to representation of the digits. Within this large cortical zone in the macaque somatosensory cortex, the complexity of neuronal receptive field characteristics increases from area 3b to areas 1 and 2 (refs 1-7). This increase in complexity continues into the upper bank of the intraparietal sulcus, where the somatosensory cortex adjoins the parietal association cortex. In this bank, callosal connections are much denser than in the more anterior part of this cortical zone. We have now discovered a substantial number of neurons with receptive fields on the bilateral hands. It was previously thought that neuronal receptive fields were restricted to the contralateral side in this cortical zone. Neurons with bilateral receptive fields were not found after lesioning the postcentral gyrus in the contralateral hemisphere. The majority of these neurons had receptive fields of the most complex types, representing multiple digits, indicating that the interhemispheric transfer of information occurs at higher levels of the hierarchical processing in each hemisphere.

Bilateral Integration of Whisker Information in the Primary Somatosensory Cortex of Rats

“…The identification of ipsilaterally and contralaterally evoked interactions, being shown to be dependent on the spatial and temporal inter-relationship of left-and right-side stimuli, strongly supports our notion that the barrel cortices integrate whisker stimuli bilaterally. Furthermore, the demonstration of differences in cortical activity in response to bilaterally heterologous whisker stimuli is a substantial departure from previous works that demonstrate bilateral influence on responses restricted to homotopic receptive fields (Pidoux, Verley, 1979;ArmstrongJames, George, 1988;Calford and Tweedale, 1988;Iwamura et al, 1994;Clarey et al, 1996;Shin et al, 1997).…”

“…Also, there are no reports of either contralaterally evoked whisker responses in trigeminal whisker-related nuclei or ipsilaterally evoked responses in whisker-related thalamic nuclei. In other systems and species, ipsilaterally evoked activity in primary sensory cortices has been widely accounted for by transcallosal pathways (Berlucchi et al, 1967;Swadlow, 1974;Manzoni et al, 1989;Iwamura et al, 1994;Schnitzler et al, 1995;Clarey et al, 1996;Swadlow and Hicks, 1997).…”

Diffuse optical tomography of pain and tactile stimulation: Activation in cortical sensory and emotional systems

“…Interhemispheric connections of the primary somatosensory cortex are reported in rodents and monkeys (Iwamura et al 1994;Krubitzer et al 1998). In support of an interhemispheric transfer of sensory information, neurons with bilateral receptive fields of the hands in monkeys, were not present following contralateral lesioning of the postcentral gyrus (Iwamura et al 1994). In addition to pain, tactile stimulation of the hand results in bilateral SI activation (Hansson and Brismar 1999); this was around 20% less than the contraleral effect, which was similar to that observed in our study for brush stimuli.…”

“…However, other study suggests that nociceptive information reaches distinct thalamic subnuclei eliciting a bilateral cortical response (Tsuji et al 2006). Interhemispheric connections of the primary somatosensory cortex are reported in rodents and monkeys (Iwamura et al 1994;Krubitzer et al 1998). In support of an interhemispheric transfer of sensory information, neurons with bilateral receptive fields of the hands in monkeys, were not present following contralateral lesioning of the postcentral gyrus (Iwamura et al 1994).…”

Intraparietal Bimodal Neurones Delineating Extrinsic Space Through Intrinsic Actions

“…This most likely takes place in the intraparietal cortices where the hierarchically processed somatosensory information (Iwamura, 1998;Iwamura & Tanaka, 1996;Iwamura, Tanaka, & Hikosaka, 1980;Iwamura, Tanaka, & Iriki, 1994;Iwamura, Tanaka, Sakamoto, & Hikosaka, 1993;Taoka, Toda, & Iwamura, 1998;Toda & Taoka, 2002) adjoins the information on spatial vision processed along the dorsal stream (Seltzer & Pandya, 1980;Ungerleider & Mishkin, 1982). Indeed, in human patients, lesions in this brain area are known to cause impairment of the body schema (Head & Holmes, 1911), which makes it difficult for the patient to achieve purposeful hand movements in the dark or without seeing, i.e., without visual guidance.…”