Human cognitive neuroscience seminar

Speaker: Jessica Teed (University of Edinburgh)

Title: A test of the hemispheric dominance of object processing

Abstract: Konen et al., (2011) presented a case of patient SM; a stroke patient with a right lateralised lesion resulting in object agnosia. Reductions in object-selective responses in the intact left hemisphere (LH) revealed by functional MRI (fMRI) could suggest a right hemispheric (RH) dominance for object processing. We aimed to test this claim. It was hypothesised that transcranial magnetic stimulation (TMS) of shape-responsive visual cortex in the right RH would cause a greater reduction in shape discrimination performance than TMS of the homologous LH region or bilateral control sites.

Prior to TMS, neurologically healthy participants completed a psychophysics paradigm to determine participant specific shape discrimination thresholds. Bilateral TMS targets were then functionally localised through fMRI scans and control sites (V5/MT+) were defined using a probabilistic atlas (Wang et al., 2015). Repetitive TMS to the LH or RH target or control site was then used to observe the effect on a same-different shape matching task.

We found no significant differences in reaction time or sensitivity measures between experimental and control conditions across hemispheres or for the RH vs the LH. This pattern of results was not due to differences in stimulation precision across conditions. These results do not provide evidence for a strong right lateralisation of object processing.