Neuronal oscillatory correlates of stimulus-response (in)congruency

Abstract

Transforming sensory input into motor output is an important function of the brain and involves various brain regions. Stimulus response (SR) congruency tasks can be used to probe these regions. Traditionally, electroencephalography (EEG) has been used to measure sensor level lateralized evoked potentials in the time domain, to study the neural correlates of sensorimotor transformations. We used magnetoencephalography (MEG) in combination with a modified Simon task to explore the oscillatory components related to the processing of SR-(in)congruencies. MEG allows for whole head coverage and source analysis, reducing the need to combine left and right recording sites. Moreover, evidence is increasing that oscillations are crucial for information processing within and between regions. 19 Subjects performed a two choice response task. In a given trial, one out of two lateralized visual stimuli reflected the required response side. Differences in oscillatory activity between SR-congruent and SR-incongruent trials were assessed at the source level using beamformers, and the results for the two response sides were combined. We found SR congruency effects in several brain regions. Specifically, we observed a more profound event related desynchronization (ERD) in visual and parietal regions (α-band) and sensorimotor regions (β-band) contralateral to the response side in the congruent condition, and a less profound ERD in ipsilateral sites. High frequency power was increased in contralateral temporo occipital, parietal and sensorimotor regions in the congruent condition, and decreased in homologous ipsilateral sites. These findings extend earlier reports and show a hemisphere specific increase in activity, not only in visual regions processing the target stimulus, but also in ipsilateral executive regions in the incongruent condition. The latter finding may reflect activity to suppress an automated response to spatially congruent SR-pairs. Event abstract at: Biomag 2010 - 17th International Conference on Biomagnetism Conference, 28 March - 01 April 2010, Dubrovnik, Croatia.