On the planum temporale lateralization in suprasegmental speech perception: evidence from a study investigating...

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Neuroscience

Background:

• The asymmetric sampling in time (AST) hypothesis proposes distinct roles for left and right auditory cortex in speech processing.
• Understanding the neural basis of speech comprehension, particularly hemispheric specialization, is crucial.

Purpose of the Study:

• To test the AST hypothesis using functional and structural magnetic resonance imaging (fMRI).
• To investigate the representation of speech in primary and nonprimary auditory cortex.
• To explore the relationship between auditory cortex structure and speech processing ability.

Main Methods:

• A parametric clustered-sparse fMRI study involving 23 volunteers.
• Systematic reduction of acoustic cues in spoken sentences using local time-reversion.
• Measurement of functional lateralization in Heschl's gyrus, planum temporale, and posterior superior temporal gyrus.
• Automated measurement of planum temporale cortical thickness.

Main Results:

• Functional lateralization in Heschl's gyrus was not observed.
• Lateralization in the planum temporale and posterior superior temporal gyrus shifted to the right hemisphere as temporal integrity decreased.
• Greater left than right cortical thickness in the planum temporale correlated with better performance on an auditory pattern-matching task.

Conclusions:

• Findings support the AST hypothesis regarding the division of labor between left and right nonprimary auditory cortex.
• Novel insights into hemispheric specialization during spoken utterance comprehension.
• Evidence for a structural-behavioral relationship in the nonprimary auditory cortex.