Individual Variability in Functional Organization of the Human and Monkey Auditory Cortex

Area of Science:

• Neuroscience
• Comparative Cognition
• Auditory Processing

Background:

• The auditory cortex (AC) is increasingly recognized for complex cognitive roles beyond basic feature segregation.
• Experience-dependent plasticity shapes AC function, leading to significant individual variability.
• Historically, AC variability has been viewed as a methodological challenge rather than a key research area.

Purpose of the Study:

• To investigate individual variability in the human and macaque auditory cortex using intrinsic functional connectivity.
• To explore how variability changes across the auditory processing hierarchy.
• To compare variability patterns between auditory and visual cortices and across hemispheres.

Main Methods:

• Analysis of intrinsic functional connectivity patterns in the auditory cortex of humans and macaques.
• Comparison of variability in primary versus nonprimary AC regions.
• Confirmatory analysis using task-based functional magnetic resonance imaging (fMRI).

Main Results:

• Interindividual variability in the human AC increases significantly from primary to nonprimary areas.
• Auditory cortex exhibits greater variability than comparable visual areas.
• Higher variability was observed in the left than the right hemisphere in humans, a pattern mirrored in macaques.
• Similar modality differences and lateralization of variability were found in both species.

Conclusions:

• Individual variability in the auditory cortex is a significant phenomenon, not merely a methodological artifact.
• The hierarchical and lateralized patterns of AC variability in humans are conserved in macaques, suggesting evolutionary importance.
• Understanding AC variability offers insights into the evolution of complex auditory functions, including language.