Inferior frontal regions underlie the perception of phonetic category invariance.
The problem of mapping differing sensory stimuli onto a common category is fundamental to human cognition. Listeners perceive stable phonetic categories despite many sources of acoustic variability. What are the neural mechanisms that underlie this perceptual stability? In this functional magnetic resonance imaging study, a short-interval habituation paradigm was used to investigate neural sensitivity to acoustic changes within and between phonetic categories. A region in the left inferior frontal sulcus showed a pattern of activation consistent with phonetic invariance: insensitivity to acoustic changes within a phonetic category and sensitivity to changes between phonetic categories. Left superior temporal regions, in contrast, showed graded sensitivity to both within- and between-category changes. These results suggest that perceptual insensitivity to changes within a phonetic category may arise from decision-related mechanisms in the left prefrontal cortex and add to a growing body of literature suggesting that the inferior prefrontal cortex plays a domain-general role in computing category representations.
Myers
Emily B
EB
Department of Cognitive and Linguistic Sciences, Brown University, Box 1978, Providence, RI 02912, USA. emily_b_myers@brown.edu
Blumstein
Sheila E
SE
Walsh
Edward
E
Eliassen
James
J
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000704:Analysis of Variance; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D003657:Decision Making / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010700:Phonetics; D011930:Reaction Time / Q000502:physiology; D013334:Students / Q000523:psychology; D055815:Young Adult