ISSN:
1432-1106
Keywords:
Monkey
;
Visual deprivation
;
Blindness
;
Brodmann's area 7
;
Microelectrode recording
;
Plasticity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Clinical experience from humans deprived of vision at an early age indicates that recovery of vision is often rudimentary after late correction of the abnormalities in the eyes. Binocular deprivation in cats does not change the function of the visual cortex equally much as does monocular deprivation. Therefore, the behavioural blindness observed after binocular deprivation is probably caused by changes central to area 17. We studied four monkeys deprived of vision by binocular lid closure from shortly after birth until the ages of 7 to 11 months and three control animals of the same age. After opening, the eyes of the deprived animals were normal, optokinetic nystagmus could be elicited, and microelectrode recordings of multiple unit activity in areas 17 and 19 indicated brisk responses to visual stimulation. Behaviourally, all deprived animals were blind, however. They bumped into obstacles, fell from tables and used their somatic sense for exploration. Only minute recovery of visual orientation was observed during several months after the opening of the eyes. Approximately 400 multiple unit recording penetrations were made in Brodmann's area 7 in the deprived monkeys and a similar number in the control monkeys using the transdural recording technique in conscious, behaving animals. The results indicated a profound decrease in the representation of vision in this area: the representation of visual mechanisms was reduced by 92% and the combined visual and somatic representation was reduced by 97% in the deprived monkeys. On the other hand, the representation of active somatic movement had increased by 117% and that of passive somaesthesia by 53%. Also the proportion of cell groups that could not be activated (only spontaneously active) increased fourfold. These results show that early visual deprivation alters the associative systems of the brain by reducing the efficiency of transmission along pathways that mediate visual influences. Inputs from different sensory systems may compete for influence on the association cortex, disuse in one leading to its functional deterioration. Such changes may explain the lasting behavioural alterations that take place in man and monkeys after prolonged visual deprivation at an early age.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00235723
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