AXONAL PROCESSES AND NEURAL PLASTICITY .2. ADULT SOMATOSENSORY MAPS

Following our recent presentation of an axonal process sprouting and r etraction framework for ocular dominance column formation, we now appl y it, unchanged, to address issues of adult somatosensory map plastici ty. Specifically, we model the rearrangement of S-l in adult rodents f ollowing denervation of a row of vibrissae, and the rearrangement of a rea 3b in adult monkeys following hyperstimulation of a digit. While w e do not attempt to capture the rapid changes which occur as the resul t of unmasking or potentiating existing connections, we demonstrate th at axonal process sprouting and retraction is a possible mechanism med iating many of the long-term changes induced by anomalous peripheral a ctivity. A significant feature of our framework demonstrated by this s tudy, is that it can account for plasticity in both developing and mat ure systems, and in different sensory modalities. In contrast synapse specific Hebbian models with synaptic normalization, which employ anat omically fixed connections capable of changes in efficacy, may not be able to account for both developmental and adult plasticity without th e form of the imposed normalization, which enforces competition betwee n afferents, being changed.