Word length modulates neural activity in auditory cortex during covert object naming

• Published in: Neuroreport Vol. 14; no. 18; pp. 2323 - 2326
• Main Authors: Okada, Kayoko, Smith, Kevin R, Humphries, Colin, Hickok, Gregory
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins, Inc 19-12-2003; Lippincott Williams and Wilkins
• Subjects: Auditory Cortex - physiology; Biological and medical sciences; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Eye and associated structures. Visual pathways and centers. Vision; Female; Fundamental and applied biological sciences. Psychology; Humans; Magnetic Resonance Imaging - methods; Male; Photic Stimulation - methods; Reaction Time - physiology; Reading; Speech - physiology; Vertebrates: nervous system and sense organs; Human; Visual cortex; Motor pathway; Central nervous system; Temporal cortex; Auditory cortex; Encephalon; Visual pathway; Occipital cortex; Speech; Auditory pathway; Premotor cortex; Behavior
• ISSN: 0959-4965; 1473-558X
• DOI: 10.1097/00001756-200312190-00007

Several lines of evidence show that posterior portions of left auditory cortex participate in aspects of speech production. A current hypothesis is that these regions play a specific role in processing phonological codes. We used event-related fMRI to test this hypothesis. Subjects covertly named objects that had names varying in length from one to four syllables. Behavioral data, both in previous work and in the present study, show an increase in naming reaction time as words get longer, reflecting the increase in phonological load. If left posterior auditory areas participate in phonological aspects of production, word length should modulate neural activity in this region. Object naming activated the left planum temporale in each subject, confirming previous findings of auditory cortex involvement in speech production. The timecourse of activation in this region showed a length effect, consistent with its hypothesized role in phonological processing. Similar effects were also observed in premotor cortex, but not in occipital–temporal cortex, which presumably supports visual processing of the pictures to be named.