Right-hemispheric superiority in split-brain monkeys for learning and remembering facial discriminations

Area of Science:

• Neuroscience
• Comparative Psychology
• Cognitive Science

Background:

• Facial recognition is a complex cognitive function.
• Hemispheric lateralization, the specialization of brain functions, is well-documented in humans.
• Investigating facial processing lateralization in non-human primates offers insights into the evolution of this function.

Purpose of the Study:

• To investigate hemispheric lateralization for facial processing in rhesus monkeys.
• To determine if the right hemisphere shows superiority in learning and remembering facial discriminations.
• To explore potential sex differences and task-specific variations in facial processing lateralization.

Main Methods:

• Twenty-six split-brain rhesus monkeys were trained on go/no-go discrimination tasks involving monkey faces.
• Tasks included discriminating individual identity and facial expression.
• Performance was compared between the left and right cerebral hemispheres.

Main Results:

• Monkeys learned and remembered facial discriminations significantly better with the right hemisphere compared to the left.
• No significant difference in laterality was observed between identity and expression discrimination tasks.
• Female monkeys exhibited greater lateralization for learning facial discriminations than males, a difference not seen in memory.

Conclusions:

• Rhesus monkeys exhibit a right-hemispheric superiority for facial processing, mirroring human capabilities.
• Hemispheric specialization for facial identity and expression discrimination is comparable in this primate model.
• Sex differences in facial processing lateralization warrant further investigation in primate cognition.