Functional imaging analyses reveal prototype and exemplar representations in a perceptual single-category task.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Computational Neuroscience

Background:

• Similarity-based categorization relies on either exemplars or prototypes.
• Previous research located prototype and exemplar representations in distinct brain areas for multi-category tasks.
• Neural basis of single-category similarity-based categorization remains unclear.

Purpose of the Study:

• Investigate the neural implementation of exemplar and prototype representations in single-category perceptual similarity-based categorization.
• Clarify the distinct brain regions involved in these two categorization strategies.

Main Methods:

• Utilized a dot-pattern paradigm-based task.
• Applied model-based univariate and multivariate functional magnetic resonance imaging (fMRI) analyses.
• Employed Bayesian analyses to confirm representation presence or absence.

Main Results:

• Univariate analyses revealed bilateral visual areas for both prototype and exemplar representations.
• Multivariate analyses identified parietal areas for prototype representations and the hippocampus for exemplar representations.
• Bayesian analyses confirmed the absence of prototype representations in the hippocampus and ventromedial prefrontal cortex (vmPFC).

Conclusions:

• Neural implementation of categorization differs between prototype and exemplar strategies within single categories.
• Parietal and visual areas support prototype representations, while the hippocampus and visual areas support exemplar representations.
• Some individuals exhibit simultaneous use of both strategies, suggesting cognitive flexibility in categorization.