The search for cerebral dominance in monkeys

Area of Science:

• Neuroscience
• Primate Behavior
• Cognitive Science

Background:

• Handedness and manual preferences are observed in rhesus monkeys.
• Cerebral dominance for cognitive tasks is well-established in humans.
• The extent of hemispheric specialization in non-human primates remains an area of investigation.

Purpose of the Study:

• To investigate cerebral dominance for problem-solving and handedness in rhesus monkeys.
• To determine if unilateral ablations in specific cortical areas affect cognitive performance.
• To compare handedness and cognitive behavior between monkeys and humans.

Main Methods:

• Unilateral ablations were performed on the association cortex of twelve monkeys.
• Lesions were targeted in the foveal prestriate cortex or dorsolateral frontal cortex.
• Subjects were tested on handedness and visual pattern discrimination tasks.

Main Results:

• Monkeys with unilateral posterior lesions performed significantly worse on visual discrimination tasks compared to controls.
• No significant differences were observed based on the hemisphere (dominant vs. nondominant) of the lesion.
• Evidence suggests a lack of cerebral dominance for problem-solving in monkeys.

Conclusions:

• Rhesus monkeys appear to lack cerebral dominance for both handedness and cognitive behaviors.
• Handedness in monkeys is superficially similar to humans but lacks underlying hemispheric specialization.
• These findings challenge the direct extrapolation of human brain lateralization models to non-human primates.