Neural Correlates of Sublexical Processing in Phonological Working Memory

• Published in: Journal of cognitive neuroscience 2011-04, Vol.23 (4), p.961-977
• Main Authors: McGettigan, Carolyn, Warren, Jane E., Eisner, Frank, Marshall, Chloe R., Shanmugalingam, Pradheep, Scott, Sophie K.
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Adult; Analysis of Variance; Brain; Brain - anatomy & histology; Brain - blood supply; Brain - physiology; Brain Hemisphere Functions; Brain Mapping; Cognition & reasoning; Correlation; Diagnostic Tests; Female; Functional Laterality; Humans; Image Processing, Computer-Assisted - methods; Individual Differences; Language Processing; Linguistics; Magnetic Resonance Imaging - methods; Male; Memory; Memory, Short-Term - physiology; Neurons; Neurosciences; Oxygen - blood; Phonemes; Phonetic Analysis; Phonetics; Phonology; Reaction Time - physiology; Recognition; Short Term Memory; Speech; Young Adult
• ISSN: 0898-929X; 1530-8898
• DOI: 10.1162/jocn.2010.21491

This study investigated links between working memory and speech processing systems. We used delayed pseudoword repetition in fMRI to investigate the neural correlates of sublexical structure in phonological working memory (pWM). We orthogonally varied the number of syllables and consonant clusters in auditory pseudowords and measured the neural responses to these manipulations under conditions of covert rehearsal (Experiment 1). A left-dominant network of temporal and motor cortex showed increased activity for longer items, with motor cortex only showing greater activity concomitant with adding consonant clusters. An individual-differences analysis revealed a significant positive relationship between activity in the angular gyrus and the hippocampus, and accuracy on pseudoword repetition. As models of pWM stipulate that its neural correlates should be activated during both perception and production/rehearsal [Buchsbaum, B. R., & D'Esposito, M. The search for the phonological store: From loop to convolution. 762–778, 2008; Jacquemot, C., & Scott, S. K. What is the relationship between phonological short-term memory and speech processing? 480–486, 2006; Baddeley, A. D., & Hitch, G. Working memory. In G. H. Bower (Ed.), (Vol. 8, pp. 47–89). New York: Academic Press, 1974], we further assessed the effects of the two factors in a separate passive listening experiment (Experiment 2). In this experiment, the effect of the number of syllables was concentrated in posterior–medial regions of the supratemporal plane bilaterally, although there was no evidence of a significant response to added clusters. Taken together, the results identify the planum temporale as a key region in pWM; within this region, representations are likely to take the form of auditory or audiomotor “templates” or “chunks” at the level of the syllable [Papoutsi, M., de Zwart, J. A., Jansma, J. M., Pickering, M. J., Bednar, J. A., & Horwitz, B. From phonemes to articulatory codes: an fMRI study of the role of Broca's area in speech production. 2156–2165, 2009; Warren, J. E., Wise, R. J. S., & Warren, J. D. Sounds do-able: auditory–motor transformations and the posterior temporal plane. 636–643, 2005; Griffiths, T. D., & Warren, J. D. The planum temporale as a computational hub. 348–353, 2002], whereas more lateral structures on the STG may deal with phonetic analysis of the auditory input [Hickok, G. The functional neuroanatomy of language. 121–143, 2009].