Abstract
The neural correlates of intraindividual response variability were investigated in a serial choice reaction time (CRT) task. Reaction times (RTs) from the faster and slower portions of the RT distribution for the task were separately aggregated and associated P300 event-related potentials computed. Independent behavioral measures of executive function and IQ were also recorded. Across frontal, fronto-central, central, centro-parietal and parietal scalp regions, P300 amplitudes were significantly greater for faster relative to slower behavioral responses. However, P300 peak amplitude latencies did not differ according to the speed of the behavioral RT. Importantly, controlling for select independent measures of executive function attenuated shared variance in P300 amplitude for faster and slower trials. The findings suggest that P300 amplitude rather than latency is associated with the speed of behavioral RTs, and the possibility that fluctuations in executive control underlie variability in speeded responding.
Highlights
The possibility that trial-to-trial reaction time (RT) variability may provide a behavioral marker of central nervous system integrity has generated considerable interest
There is an association between the endogenous P300 ERP component and intraindividual RT variability (IIV) in persons who have experienced head trauma (Segalowitz et al, 1997), and recent work has confirmed a systematic association between that component and the degree of within-person variability (Saville et al, 2011)
The electrophysiological studies investigating IIV have predominately used either a between-participant design, where persons exhibiting high behavioral IIV are contrasted with persons of low variability, or correlational methods where behavioral variability measures are regressed on EEG metrics
Summary
The possibility that trial-to-trial reaction time (RT) variability may provide a behavioral marker of central nervous system integrity has generated considerable interest. Work implicates involvement of striatal dopamine D2 receptor binding (MacDonald et al, 2009), a finding that is consistent with the idea that IIV may reflect neural noise in the brain (Li et al, 2001) These imaging studies clearly suggest brain structures or activity to be associated with IIV, a limitation is that they provide little insight into the temporal synchronicity between brain processes and behavior. Since the early work of Morrell and Morrell (1966) and Donchin and Lindsley (1966), to our knowledge no research has used a within-subject design where ERP components elicited by a visual task have been delineated for behavioral RTs from the faster and slower reaches of the distribution As such an analysis may provide important insights into the cognitive operations that underlie IIV, it is this research shortfall that motivates the first major objective of the present study. It is likely that the factors that drive between-participant differences in variability as reflected by a person’s standard deviation, including noise at perceptual and response stages of processing, lapses of attention, and fluctuations in cognitive load, are likely to be the same as those tapped into by comparing faster with slower latency bins
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