The p300 as a marker of waning attention and error propensity

Abstract

Action errors can occur when routine responses are triggered inappropriately by familiar cues. Here, EEG was recorded as volunteers performed a "go/no-go" task of long duration that occasionally and unexpectedly required them to withhold a frequent, routine response. EEG components locked to the onset of relevant go trials were sorted according to whether participants erroneously responded to immediately subsequent no-go trials or correctly withheld their responses. Errors were associated with a significant relative reduction in the amplitude of the preceding P300, that is, a judgement could be made bout whether a response-inhibition error was likely before it had actually occurred. Furthermore, fluctuations in P300 amplitude across the task formed a reliable associate of individual error propensity, supporting its use as a marker of sustained control over action.

Figure 1

Selection of trials for the main comparison. Each figure represents the sequence of events in the SART where go trials are defined by any digit between 1 and 9 (except 3) and the no-go target by the 3. In each sequence, the participant is responding correctly to go trials. In the upper panel, the presentation of the target is followed by a correctly withheld response. In the lower panel, by an error, the correct go trials prior to these no-go signals (highlighted) form the basis of the comparison.

Figure 2

The difference between go trials preceding a correct or erroneous no-go trial. Each figure shows EEG (at Pz), finger muscle activity (extensor/flexor), and eye movements (left and right) averaged across all available relevant trials. The crucial difference between these go trials appears to be in the amplitude of the P300 ERP peak, highlighted in the grey band.

Figure 3

The difference between go trials preceding a correct or erroneous no-go trial. The figure shows a boxplot for the P300 : P200 amplitude ratio for the two “types” of go trial. Each shows the median (heavy line), interquartile range (shaded area), and total range for the 25 volunteers. Prior to a correct no-go trial, the median normalized P300 amplitude exceeds even the interquartile range of that seen in go-trials prior to an no-go error.

Figure 4

Propensity to error is associated with the maintenance of the P300 : P200 ratio across the task. The boxplot shows error frequencies for participants with high or low mean P300 values (defined by a median split of the total participant group), respectively.