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Development and plasticity of the neural circuitry underlying visual recognition memory
M J Webster1, L G Ungerleider, J Bachevalier
1Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, MD 20892, USA.
Canadian Journal of Physiology and Pharmacology
|September 1, 1995
Summary
Infant monkeys with damage to the inferior temporal cortex (area TE) show preserved visual recognition memory. This suggests the neocortex has greater compensatory potential than the medial temporal lobe during early development.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Developmental Neuroscience
Background:
- Visual recognition memory in adult monkeys relies on interactions between the inferior temporal cortex (area TE) and medial temporal lobe structures.
- Monkeys mature in visual recognition memory, measured by the delayed nonmatching to sample (DNMS) task, by two years of age.
- Protracted development is linked to neocortical immaturity rather than medial temporal lobe immaturity.
Purpose of the Study:
- To investigate the developmental trajectory and compensatory mechanisms of visual recognition memory in monkeys.
- To compare the effects of early versus late lesions in area TE and medial temporal lobe structures on visual memory.
- To understand the role of neocortical plasticity in early visual memory development.
Main Methods:
- Lesion studies in infant and adult monkeys, targeting area TE and medial temporal lobe structures.
- Behavioral assessment using the delayed nonmatching to sample (DNMS) task.
- Analysis of neurochemical (opiatergic, cholinergic receptors), metabolic, and connectivity changes.
Main Results:
- Lesions of medial temporal lobe structures in infancy or adulthood cause permanent visual recognition deficits.
- Early lesions of area TE result in significant and lasting visual memory sparing, unlike late lesions.
- Neonatal cortical removals show greater compensatory potential than neonatal medial temporal removals.
- Early area TE damage promotes maintenance of transient projections and reorganization in extra-temporal cortical areas.
- Infancy visual recognition is widespread across visual association areas, localizing to area TE with maturation.
Conclusions:
- The medial temporal lobe is critical for visual memory from early life.
- The neocortex, specifically area TE, exhibits significant plasticity in early development, allowing for functional compensation.
- Early damage to area TE can lead to preserved visual recognition memory through compensatory mechanisms involving widespread cortical reorganization.