Poster A45, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Left-lateralized reading network illustrated by causal effective connectivity
Chotiga Pattamadilok1, Samuel Planton1, Deirdre Bolger2, Mireille Bonnard3; 1Aix Marseille Université, CNRS, LPL UMR 7309, 13100, Aix-en-Provence, France, 2Labex Brain and Language Research Institute, 3Aix Marseille Université, Institut de Neurosciences des Systèmes, INSERM, UMR 1106, Marseille, France
Left lateralization of the reading network has been explained by the specialization of the left hemisphere for spoken language processing. Findings from connectivity analyses of neuro-imaging data raise the issue of whether the left-lateralization results from reduced activation in the right hemisphere or an increased activation in left hemisphere. Here, we applied a causal intervention approach to examine the effective connectivity between the ventral occipito-temporal cortex (vOT), a key area in the reading network, to other cortical areas when participants processed non-linguistic vs. linguistic stimuli and tasks. Transcranial magnetic stimulation (TMS) was applied to the left-vOT while the participants performed color (non-linguistic stimulus and task), symbol (linguistic stimulus/non-linguistic task) and animal name detection tasks (linguistic stimulus and task). EEG was recorded to track stimulus and task-dependent changes in regional activation (ERP) and in effective connectivity (TMS-induced ERP or TEP). The results showed that, on no-TMS trials, linguistic stimuli led to increased ERP activity in the occipito-temporal regions in both hemispheres around 170ms compared to non-linguistic stimuli. However, TEP showed a different activation pattern, with a stronger propagation of activity to the right occipito-temporal region when participants processed non-linguistic stimuli. When only linguistic materials were involved, performing a linguistic task reduced the TEP in inter-hemispheric regions, suggesting that brain activity is more restricted to the left hemisphere. The causal evidence reported here suggests that reduced effective connectivity between the left-vOT and the right hemisphere during language processing provides an explanation for the left-lateralization of the reading network.
Topic Area: LANGUAGE: Other