The relationship between naming reaction time and functional MRI parameters in Broca's area

We examined the correlation between behavioural reaction time and functional imaging parameters of the blood oxygenated level dependent (BOLD) response in Broca's Area during a word identification task, and whether the correlation [Magnetic Resonance Imaging 22 (2004) 451-455] varies as a function of four stimulus types: regular words (REGs) (e.g., hint), irregular words (IRRs) (e.g., pint), nonwords (NWs) (e.g., bint), and pseudohomophones (PHs) (e.g., pynt). Participants named letter strings aloud during a functional magnetic resonance imaging study. Naming reaction times were recorded during regular gaps in image acquisition, and BOLD parameters were extracted via a Tikhonov regularized BOLD analysis technique. The results revealed that only PH reaction times were correlated with BOLD width, providing evidence that Broca's area supports phonetic decoding accompanied with phonological lexical access. In addition, we advanced the development of equation-based models of cognitive behaviour and neurophysiology, whereby we showed that the relationship of mathematical independence that exists for predicting REG accuracy, given IRR and NW or PH naming accuracy, was present for naming reaction time, BOLD width, BOLD time to peak, and BOLD intensity. Therefore, we provide converging behavioural and neuroanatomical evidence for a mathematically independent relationship between sight vocabulary and phonetic decoding systems, consistent with a dual-route model of reading.