Structural neural correlates of individual differences in categorical perception.

Area of Science:

• Neuroscience
• Psycholinguistics
• Speech Perception

Background:

• Listeners perceive speech sounds categorically.
• Individual differences in categorical perception exist in typical adults.
• Neural correlates of this variability are not well understood.

Purpose of the Study:

• Investigate neural sources of individual variability in categorical speech perception.
• Relate brain structure to behavioral measures of categoricity and response consistency.
• Examine the role of frontal and temporal lobe structures.

Main Methods:

• Fifty-seven participants completed behavioral tasks assessing speech sound categorization.
• Phonetic tokens were rated on a visual analogue scale.
• Magnetic Resonance Imaging (MRI) was used to measure brain structure (surface area, gyrification).

Main Results:

• Increased surface area in the right middle frontal gyrus predicted more categorical perception of a fricative continuum.
• Greater gyrification in bilateral transverse temporal gyri predicted less consistent responses.
• These findings link specific brain regions to individual differences in speech perception.

Conclusions:

• Frontal regions are sensitive to phonetic category-level information and predict individual behavior.
• Variations in temporal lobe gyrification may reflect subtle differences in language ability.
• This study provides insights into the neural basis of individual variability in speech perception.