Drf. Irvine et R. Rajan, INJURY-RELATED AND USE-RELATED PLASTICITY IN THE PRIMARY SENSORY CORTEX OF ADULT MAMMALS - POSSIBLE RELATIONSHIP TO PERCEPTUAL-LEARNING, Clinical and experimental pharmacology and physiology, 23(10-11), 1996, pp. 939-947
1. Restricted cochlear lesions in adult animals result in a reorganiza
tion of auditory cortex such that the cortical region deprived of its
normal input by the lesion is occupied by expanded representations of
adjacent cochlear loci (and thus of the frequencies represented at tho
se loci), Analogous injury-induced reorganization is seen in somatosen
sory, visual and motor cortices of adult animals after restricted peri
pheral lesions. 2. Rather than constituting a central compensation for
the peripheral loss, such reorganization appears to be an extreme for
m of changes in cortical organization that occur as a consequence of a
ltered patterns of input such as arise from differential use of restri
cted regions of receptor surfaces ('use-related' reorganization). Thus
, the frequency organization of auditory cortex is modified in animals
trained to perform a frequency discrimination task and analogous chan
ges in the frequency selectivity of cortical neurons are produced by c
lassical conditioning procedures. 3. Recent evidence from the visual s
ystem suggests that changes similar to those involved in injury- and u
se-related cortical reorganization may underlie some forms of what has
been called 'perceptual learning', the improvement in sensory/ percep
tual discriminative performance with practice, Some forms of such lear
ning are highly specific to the particular stimuli used in training (i
.e. do not generalize to other stimuli), suggesting that the improved
performance reflects a change in neural circuitry at a relatively earl
y level of sensory processing, The limited available evidence supports
the occurrence of such learning in the auditory system. 4. Recent stu
dies using functional imaging and related techniques indicate that inj
ury- and use-related reorganization occurs in human sensory and motor
cortex.