Alva, M. | bioRxiv Science

bioRxiv2026

Abstract Encoding of Sounds in the Frontopolar Cortex

The frontopolar cortex has been linked to higher-order cognition, including analogical reasoning, cost-benefit analysis, and semantic associations, primarily based on neuroimaging studies in humans rather than from direct single-neuron recordings. Notably, sensory input to this region originates from auditory cortical areas. To investigate the role of the frontopolar cortex in auditory perception, we recorded single neurons in nonhuman primates trained to discriminate between various sounds, including monkey calls and human words. We found that individual neurons form abstract, nonlinear representations of learned and novel sounds, collectively encoding all sound categories and generating decision-making signals. Our findings suggest that the frontopolar cortex integrates auditory information into behaviorally relevant signals, thereby providing insights regarding its role in cognition.

neuroscience↗

bioRxiv2024

Invariant crossmodal equivalence between objects in rhesus monkeys

After hearing the words Little Red Riding Hood, many humans instantly visualize a girl wearing a red hood in the woods. However, whether nonhuman primates also evoke such visual imagery from sounds remains an open question. We explored this from direct behavioral measurements from two rhesus macaques trained in a delayed crossmodal equivalence task. In each trial, they listened to a sound, such as a monkey vocalization or a word, and three seconds later, selected a visual equivalent out of a pool of 2 to 4 pictures appearing on a touchscreen. We show that monkeys can be trained to discriminate perceptual objects of numerous properties and furthermore that they perceive as invariant different versions of the learned sounds. We propose two potential mechanisms for the brain to solve this task: acoustic memory or visual imagery. After analyzing the monkeys choice accuracies and reaction times in the task, we find that they experience visual imagery when listening to sounds. Therefore, the ability of rhesus monkeys to perceive crossmodal equivalences between learned categories poses rhesus monkeys as an ideal model organism for studying high-order cognitive processes like semantics and conceptual thinking at the single-neuron level.

animal behavior and cognition↗