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Recovery of tactile function after damage to primary or secondary somatic sensory cortex in infant Macaca mulatta
1Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri 63110.
Abstract:
These studies were designed to determine the basis for recovery of tactile function after the removal of primary (SI) or secondary (SII) cortex in infant Macaca mulatta. From previous studies we know that although removal of SI or SII in the adult macaque produces severe and irreversible impairment on a variety of tactile tasks, normal function can be obtained after partial or total SI lesions in the infant. From the present studies we have found that, as with SI, neither unilateral nor bilateral removals of SII in infants significantly affected the acquisition of or the performance on size tasks, but did cause a temporary delay in acquisition of texture tasks. Performance on texture threshold tasks was normal. The removal of the remaining SI in a juvenile animal that had received a unilateral SI lesion in infancy did not disrupt the recovered function, indicating that recovery is not mediated by the intact SI. However, when SI and SII were removed together from the same hemisphere in an infant, either sequentially or simultaneously, major impairment in the acquisition of texture tasks followed. These results suggest that although SI and SII are necessary for normal tactile function in the adult macaque, they show an equipotentiality for mediating normal tactile function after damage to either area in infants.
Insights
Infant macaques can recover tactile function after primary (SI) or secondary (SII) cortex removal. While SI and SII are crucial in adults, infants show equipotentiality, recovering function even after damage to both areas.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Sensory Systems
Background:
- Adult macaques experience severe tactile deficits after primary (SI) or secondary (SII) cortex removal.
- Infant macaques demonstrate remarkable recovery of tactile function following SI lesions.
Purpose of the Study:
- To investigate the basis of tactile function recovery after SI or SII cortex removal in infant macaques.
- To determine if SII cortex plays a role in tactile function recovery in infants.
Main Methods:
- Unilateral and bilateral removals of SII cortex in infant macaques.
- Sequential or simultaneous removal of SI and SII cortex in infant macaques.
- Assessment of tactile function recovery using size and texture discrimination tasks.
Main Results:
- Infant SII cortex removal caused temporary delays in texture task acquisition but not size tasks.
- Removal of the remaining SI in juvenile macaques with prior SI lesions did not impair recovered function.
- Combined SI and SII cortex removal in infants resulted in significant impairment of texture task acquisition.
Conclusions:
- Infant macaques exhibit equipotentiality between SI and SII cortices for mediating tactile function recovery.
- While both SI and SII are essential for adult tactile function, infants can compensate for damage to either area.
- The findings suggest distinct developmental trajectories for tactile processing in SI and SII cortices.
