Poster A37, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Working memory and speech perception: evidence from transcranial magnetic stimulation and brain morphometry
Isabelle Deschamps1,2, Melody Courson1,2, Pascale Tremblay1,2; 1Faculty of Medicine, Laval University, QC, Canada, 2Centre de Recherche de l’Institut Universitaire en Santé Mentale de Québec, QC, Canada
Many psycholinguistic models posit that during spoken language comprehension, phonological units are processed and kept in verbal working memory (WM) before meaning can be extracted. Verbal WM mechanisms have been associated with the left supramarginal gyrus (SMG) and inferior frontal gyrus (IFG). The SMG is thought to be involved in the maintenance of phonological information (i.e. phonological short-term store) whereas the IFG would refresh the information within the short-term store through articulatory rehearsal mechanisms. However, these two regions have also been implicated during non-verbal auditory WM tasks. It is therefore unclear whether a distinct system exists for verbal WM. The objective of the current study was to determine whether the SMG and the IFG are recruited by auditory verbal and non-verbal working memory processes using single-pulse transcranial magnetic stimulation (TMS) combined to a delayed auditory discrimination task with verbal (i.e. syllables) and non-verbal (bird songs) sequences. 18 healthy right-handed adults participated in the study. TMS was delivered during the delay between the sequences to either the IFG or SMG. For each region, reaction times and accuracy were calculated. The results demonstrate that TMS applied to the IFG and SMG disrupts performance only during the (more difficult) auditory non-verbal discrimination task. The results suggest that auditory verbal and non-verbal WM share domain-general WM mechanisms. To gain further insights into the neurobiological foundation of WM mechanisms, we are currently investigating the relationship between auditory verbal and non-verbal WM and the structure of the SMG and IFG using MRI-based brain morphometry.
Topic Area: EXECUTIVE PROCESSES: Working memory