Biomedical subjects

L J Cudmore

Publications and source records attributed to L J Cudmore.

3 recordsLinked to original sources

PubMed2001

P3 topographical change with task familiarization and task complexity.

The P3 event-related potential (ERP) component is usually reported as having a centro-parietal maximum. However, a more frontal P3 topography is also evident in early-session trials which may be masked by averaging over the entire session, and is also present longer in elderly subjects. This maintenance of hyperfrontal topography is interpreted as a sign of reduced prefrontal adaptive functioning. In the present study, P3 amplitude was examined in young adults to determine: (1) how early in the test session the reduction in hyperfrontality occurs; and (2) the effect of task complexity on the P3 amplitude across electrode sites (Fz, Cz, Pz). ERPs were elicited using a working memory n-back task. Single-trial ERP waveforms were averaged in successive blocks of five trials. There was a greater decrease in P3 amplitude at Fz compared to Cz and Pz sites after the first block, and the decrease reached an asymptote by the third block. The results are interpreted as indicating rapid decrease in initial P3 hyperfrontality for a simple task in young adults, and an increased ratio of P3 amplitude at frontal versus posterior sites in more complex tasks.

Adult↗

PubMedDate not supplied

Task complexity and habituation effects on frontal P300 topography.

The P3(00) event-related potential (ERP) component is usually reported as having a centroparietal maximum. However, the P3 topography is more frontal in early-session trials which may be masked by averaging over the entire session and is evident longer into the test session among elderly subjects. This hyperfrontality is interpreted as a sign of poor prefrontal adaptive functioning. In the present study, P3 amplitude was examined in university students to determine how early a change in amplitude would be evident and the effect of task complexity on the amplitude across electrode sites. ERPs were elicited using a working-memory n-back task where participants pressed a key to target letter presentations in three conditions of increasing complexity. Single-trial ERP waveforms were then averaged in successive sequences of five trials. Results revealed a greater decrease in frontal P3 amplitude compared to the central and parietal P3 after the first block of five target trials until the third block. The results are interpreted as indicating rapid decrease in hyperfrontality with habituation to an easy task. Increases in task complexity (the 2-back paradigm), however, reduced this frontal P3 attenuation. Results support a P3 ERP model of hyperfrontality reflecting short-term adaptive function by the prefrontal cortex.

Adult↗

PubMedDate not supplied

Signal-to-noise ratio sensitivity in ERPs to stimulus and task complexity: different effects for early and late components.

Traditionally, early and late ERP components are evaluated by the latency and amplitude of their components. We investigated their signal-to-noise (S/N) ratio: how well individual ERP trials correlate with their overall averaged ERP. High correlations indicate minimal noise or individual trial variability while low correlations reflect greater trial variability. Continuous EEG activity was recorded from 57 university students during single- and dual-task conditions in a within-subjects paradigm (easy and difficult tone discrimination; with and without verbal working memory task). For early components, the addition of the second task increased the correlations between the individual trials and the averaged ERPs. For the late components, both the addition of the second task and an increase in stimulus difficulty decreased individual trial correlations. Results suggest that the S/N ratio analysis is a useful method for highlighting differences between early and late components associated with stimulus processing manipulations.

Adult↗