Attenuating the Magnocellular Pathway Inhibits the Right Hemishere Functions: Evidence from Behavioral and Imaging Experiments

Abstract:
It has been suggested that (1) imposing a red background on the stimulus display attenuates the human Magnocellular pathway functions: (2) the Magnocellular pathway is responsible for the processing of low spatial frequencies: (3) A right hemisphere (RH) advantage is observed for the processing of low spatial frequencies. Based on these, we conducted a reaction time experiment and a fMRI experiment to observe the hemispheric effects of imposing red background on the processing of hierarchically organized stimuli(Global/Local patterns). For processing of the Global configuration of the patterns, the reaction time results showed that the red condition relative to the green (control) condition produced a larger local-to-global interference in the RH. The fMRI results indicated that the red condition relative to the green condition predominantly inhibited the activation of the right frontal areas and the right angular gyrus. These results suggest that some aspects of functional hemispheric asymmetries, such as the RH advantage for the processing of low spatial frequencies, are mediated by low-level visual mechanisms such as the Magnocellular pathway.