Representation of numerical and sequential patterns in macaque and human brains

Area of Science:

• Neuroscience
• Comparative Cognition
• Psycholinguistics

Background:

• Language acquisition relies on extracting deep structures from auditory sequences.
• Understanding the neural basis of abstract sequence processing is key to language evolution.
• Comparing human and non-human primate brains offers insights into cognitive specializations.

Purpose of the Study:

• To identify brain regions involved in representing abstract properties of auditory sequences.
• To compare the neural representation of sequence properties between humans and macaques.
• To investigate the neural basis for potential human specialization in sequence processing.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used in untrained macaques and humans.
• Participants listened to series of tones with varying numbers and repetition patterns.
• Brain activity was analyzed to identify regions sensitive to 'number of items' and 'repetition pattern'.

Main Results:

• Both species showed sensitivity to the number of tones in intraparietal and dorsal premotor areas.
• Both species represented tone-repetition patterns in ventral prefrontal cortex and basal ganglia.
• Humans, but not macaques, exhibited joint sensitivity to both parameters in inferior frontal and superior temporal regions.

Conclusions:

• Non-human primates can represent some abstract properties of auditory sequences.
• Humans possess a specialized neural circuit, particularly in the left hemisphere, for unified processing of abstract sequence information.
• This human-specific circuit may underpin the unique ability for linguistic and non-linguistic sequence representation essential for language acquisition.