P 116 Methylphendiate effects on the coupling between attentional processes and motor cortex excitability

Abstract

Introduction Event related potentials (ERPs) allow the examination of sensory, attentional and cognitive processes occurring as brain responses to stimuli while the excitability of motor pathways can be evaluated by transcranial magnetic stimulation (TMS). The interplay between both, attentional processes and motor cortex excitability has been rarely reported in the literature. So far, only two studies used ERP and TMS in combination, focused on inhibition processes and reported compensatory cognitive mechanisms in case of measurement of reduced activation of inhibitory intracortical interneurons in the motor cortex ( Heinrich et al., 2014 , Hoegl et al., 2011 ). Methods This study investigated simultaneously the interaction between neural markers of attention and response control (measured by event related potentials (ERP)) and motor cortical excitability (short interval cortical inhibition, intracortical facilitation and long interval cortical inhibition, by using transcranial magnetic stimulation (TMS)) under different requirement conditions (choice reaction test (CRT), attention/go/nogo) and their pharmacological modulation by methylphenidate (MPH) in normal healthy adults ( n = 31). MPH was administered in a dosage of 1 mg/kg body weight, maximum 60 mg. Additionally, serum level and clearance of MPH were controlled. Results MPH had an effect on attention to targets in early attentional processes (increased Go and No/Go N1 but no effect on Cue N1) and on response inhibition (increased NoGo P3). CNV and Go-P3 were not affected. Cue-P3 was correlated with MPH clearance. Regarding the MPH effects on the interplay of attentional processes with motor cortex excitability, we found an association between MPH induced increase of long interval intracortical facilitation and both, suppressed early attention on cue trials (decreased Cue-N1) and with the increase of response execution control (increased Go-P3). Discussion Taken together, MPH seems to enhance in particular early target-related attentional processes. Furthermore, this study revealed a correlation of MPH-induced changes in motor cortex facilitation with cognitive response execution monitoring, whereas a coupling was absent between inhibitory processes of motor pathways and cognitive response control.