Abstract
Interhemispheric transfer (IHT) measured via differences in right- or left-handed motoric responses to lateralized visual stimuli, known as the crossed-uncrossed difference (CUD), is one way of identifying patterns of processing that are vital for understanding the transfer of neural signals. In this paradigm, responses to targets contralateral to hand of response (i.e, crossed conditions) are believed to elicit an interhemispheric transfer, while ipsilateral targets do not (i.e., uncrossed conditions). However, examination of interhemispheric transfer by means of the CUD is not entirely explained by simple measures of response time. Multiple processes contribute to wide variability observed in CUD reaction times, and there is a robust asymmetry where right-handed responses demonstrate faster and sometimes negative CUDs as compared to left-handed responses. Prior research has suggested that intra-hemispheric inhibitory processes may be involved in regulation of speed of transfer. Our study examined electroencephalography (EEG) recordings and time-frequency analysis (TFA) of alpha frequency activity while 18 participants responded to lateralized targets during performance of the classic IHT task, the Poffenberger Paradigm. We found a significant hand x target effect [F (1, 17) = 6.04; p = .025; ηp2 = .26] for time-locked alpha power, such that targets contralateral to hand of response (i.e., crossed conditions) demonstrated larger alpha synchrony, with the biggest difference in alpha activity to targets belonging to right-handed responses. This is notable since the right-hand CUD is often more variable and sometimes demonstrates a paradoxical effect with uncrossed conditions eliciting slower RTs than crossed conditions. Our findings suggest that early motoric inhibitory mechanisms may help explain the wide range of variability typically seen with the CUD.
Meeting abstract presented at VSS 2018