Connectivity measures in the Poffenberger paradigm indicate hemispheric asymmetries

Abstract

The Poffenberger paradigm is a well-known measure of interhemispheric transfer delays, calculated on the basis of the crossed vs uncrossed reaction time difference (CUD). However, the proper interpretation of CUD is extensively debated in the literature. In this study we used connectivity measures in an attempt to interpret CUD from the perspective of functional connectivity. Accordingly, we tried to define functional couplings in the Poffenberger paradigm; we used a simple choice version of the paradigm, and included a stimulation only (SO) condition for comparison. As an index of functional coupling we employed partial directed coherence, exploiting bilateral grouping of the electrodes to compute intra-and interhemispheric connection weight ratios (CWRs). Our findings indicated modulations in functional weights in relation to the SO condition, rather than the crossed and uncrossed conditions, such that the response executed by the right hemisphere yielded a decrease in intra-, yet an increase in interhemispheric CWRs, whereas the left hemisphere interactions showed connectivity patterns similar to the SO condition irrespective of the side of movement. Overall, our results suggest modulation of connectivity in the same/similar system, which was found to be optimized, in terms of hemispheric asymmetries, to different tasks.