Former Hand Territory Activity Increases After Amputation During Intact Hand Movements, but Is Unaffected by Illusory Visual Feedback

Abstract

Active engagement of the intact hand may be critical for therapies seeking to stimulate the former hand territory.

Primary somatosensory cortex hand representation dynamically modulated by motor output

“…Finally, as mentioned above, a hypothesis used to explain the genesis of phantom sensations is that of cross-activation between neighboring cortical areas. However, it has been questioned whether this fully explains the phenomena, and there is evidence that other factors, such as cross-callosal activity, may also play a role (Bogdanov, Smith, & Frey, 2012;Ramachandran & Hirstein, 1998). Nonetheless, the findings of this study do fit well with the cross-activation hypothesis.…”

Why Brain Science is Essential to the Success of Hand Allotransplantation

“…In addition to these changes occurring within the hemisphere contralateral to the amputation, studies involving animal models [32,33] and human amputees [34] provide evidence for interhemispheric changes following unilateral deafferentation. Specifically, movements of the intact hand by amputees are associated with increased activity within the sensorimotor cortex ipsilateral to the amputation [35] and more precisely within the former M1/S1 hand territory [34].…”

“…Specifically, movements of the intact hand by amputees are associated with increased activity within the sensorimotor cortex ipsilateral to the amputation [35] and more precisely within the former M1/S1 hand territory [34]. These changes appear to be attributable, at least in part, to a reduction in the normal levels of interhemispheric inhibition that exists between cortical hand representations [21], and this is likely the mechanism responsible for the fact that rodents with unilateral deafferentation reveal increased functional connectivity between forepaw representations in the left and right cerebral hemispheres when at rest [33].…”

The Significance of Somatosensory Stimulation to the Hand: Implications for Occupational Therapy Practice

“…Area 3a responds to conscious proprioception (position sense) and area 3b transmits the sensation of textures (Bear et al, 2006;Kaas & Florence, 2001). In the sensorymotor strip or homunculus, the hands, lips, and tongue are overrepresented in terms of cortical real estate relative to their skin area on the body (Bogdanov et al, 2012). This over representation is …”

“…Recently, Bogdanov, Smith, and Frey (2012) used imaging studies to demonstrate that hand amputation induces substantial reorganization of the primary sensory cortex (S1), and the effects of deafferentation increase with time. However, these changes are reversible during representation of an allogeneic transplanted hand and when the fingertips are stimulated to recapture the preamputation S1 hand cortical map territory.…”