At 6 weeks following forelimb amputation, islands of new input fr

At 6 weeks following forelimb amputation, islands of new input from the shoulder were scattered throughout all of FBS, and the areas of these new representations were significant over post-deafferentation weeks. In contrast, few sites in the central zone in CN became responsive to new shoulder input at 6 weeks post-amputation nor were significant differences in new shoulder input found in any CN zone over post-amputation weeks. In cortex, new input from the shoulder was observed in the wrist and arm representations

in week 2, and by 4 weeks, new shoulder input was recorded in the FBS. In CN control rats, sites responsive to shoulder input were recorded in lateral and medial zones, and at 2–3 weeks post-deafferentation, a transient increase in new shoulder input was found in the central zone that returned to levels similar to control rats in subsequent weeks. In no cases within the central zone were

inputs from the shoulder, or for that matter body/chest and head/neck, significantly different over post-deafferentation weeks, although significant differences in the sizes of head/neck and/or body/chest representations were observed in medial and lateral zones. It is possible that primary axons from the shoulder sprouted into the central zone but were functionally unexpressed. Similar findings of a mismatch between buy Etoposide the appearance of sprouted hindlimb afferents check into CN and their functional expression have been reported (Rhoades et al., 1993); however, even at 30 weeks post-amputation, few neurons in the central zone responded to input from the shoulder and those that did were relegated to the border region. In the present study we reported reorganization in CN beginning within 1 week after forelimb amputation, but the absence of significant new input from the shoulder in any zone

argues against the role of CN as a substrate for cortical reorganization. This failure of cuneothalamic projecting neurons, particularly in the central zone to become responsive to new input from the shoulder following forelimb amputation was not anticipated. If the central zone in CN does not reorganize to permit the expression of new shoulder input onto cuneothalamic relay neurons in the forepaw central zone, how does the new shoulder input gain access to the FBS following forelimb amputation? One possibility is that cuneothalamic projections (Alloway and Aaron, 1996, Kemplay and Webster, 1989, Massopust et al., 1985, Webster and Kemplay, 1987 and Wree et al., 2005) from neurons receiving input from the shoulder in lateral and tail-zones of CN in forelimb-intact rats send wide-spread projections to the somatopically organized VPL (Li et al., 2006).

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