Electrophysiological responses to digit stimulation in a tactile oddball paradigm

Sensory memory traces are assessed via oddball paradigms in which deviant (infrequent) stimuli are interspersed into a string of standard (frequent) stimuli. Once a memory trace for the standard is established, the deviant spurs a change detection response measured via the resulting event related potential (ERP). Response magnitude is sensitive to the differences in stimuli properties or categories and influenced by individual experience. The goal of the present study was to use ERPs to test the relation between individual digits in the somatosensory cortex and the extent to which digit representations are influenced by individual differences in experience such as independent mobility and playing video games. The present study of 60 undergraduates utilized a passive tactile oddball paradigm, stimulating the thumb, middle, and little fingers. The oddball paradigm was fully matched with each digit serving as the standard and deviant. A temporal principal component analysis (tPCA) identified factors that matched three a priori ERP components: N80, somatosensory mismatch negativity (sMMN), and P300. Analyses confirmed the anticipated differences between standards and deviants and provided some support for prior ERP work suggesting the thumb is in a different functional category than the other digits. Independent control of individual digits (such as the little finger) was positively related to only one aspect of the ERP (P3a) while video game experience was not associated with ERP differences. Cumulatively, these results provide a more nuanced examination of tactile oddball paradigms and how ERP methods can shed light on the relations between different digits.