Intraindividual reaction time variability affects P300 amplitude rather than latency.

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.

Behavioral and ERP evidence of greater distractor processing in old age.

The ability to minimize processing for irrelevant information is a central component of goal-directed behavior, which has been suggested to be compromised in old age. In this study, we investigate age differences in distractor rejection by presenting target names alongside to-be-ignored distractor faces. Older adults (mean age 70) showed greater behavioral slowing than young adults (mean age 24) when the distractor face was incompatible with the target name. That this increased interference in the older adults was indeed associated with more distractor processing, was shown by the face-related N170 component of the EEG, which had greater amplitude in older adults when faces were unattended, but not when they were attended. These findings suggest a reduced ability to prevent distractor processing in old age.

Mental health and cognitive function in adults aged 18 to 92 years.

We investigated mental health and cognitive function in 195 community-dwelling adults aged 18 to 92 years (M = 46.64). We assessed several cognitive domains, including psychomotor, executive function, and episodic memory. We found a significant Age x Mental Health interaction in relation to within-person (WP) variability (trial-to-trial variability in reaction time performance) in a four-choice psychomotor task and a Stroop task, but not in relation to mean reaction time measures from those tasks. Poorer mental health was associated with greater WP variability in older adults. We did not find this effect in relation to memory. The findings suggest that measures of WP variability may be sensitive to relatively subtle effects associated with age and poor mental health, and that they provide valuable insights into cognitive function in old age.

Wavelet filtering of the P300 component in event-related potentials.

This paper presents an application of wavelet filtering to single-trial P300 component analysis. The objective of this study is to introduce a new method for analyzing the P300 component, when performing a given cognitive task, in this case, a two-choice reaction time task. The discrete wavelet transform with Daubechies wavelet is employed to detect the presence of P300 in individual trials. Wavelet filtering is applied to remove noise and unwanted frequency components from discrete wavelet transform (DWT) coefficients based on prior knowledge of event-related potentials (ERPs). The filtering mask is computed from the grand-average of wavelet coefficients over all participants. With this filtering, the P300 component is accurately localized in both time and scale. The findings suggest the procedure to have considerable potential for the analysis of time-series data in the behavioral neurosciences.