Pupil dilation is a useful, noninvasive technique for measuring the change in cognitive load. Since it is implicit and nonverbal, it is particularly useful with preverbal or nonverbal participants. In cognitive psychology, pupil dilation is most often measured by corneal reflection eyetracking devices. The present study investigates the effect of gaze position on pupil size estimation by three common eyetracking systems. The task consisted of a simple object pursuit situation, as a sphere rotated around the display screen. Systematic errors of pupil size estimation were found with all three systems. Implications for task-elicited pupillometry, especially for gaze-contingent studies such as object tracking or reading, are discussed.

BackgroundThe Error-related negativity (ERN) is a component of the event-related brain potentials elicited by error commission. The ERN is thought to reflect cognitive control processes aiming to improve performance. As previous studies showed a modulation of the ERN amplitude throughout the execution of a learning task, this study aims to follow the ERN amplitude changes from early to late learning blocks in relation with concomitant motor sequence learning using a serial reaction time (SRT) task. Twenty-two healthy participants completed a SRT task during which continuous EEG activity was recorded. The SRT task consists of series of stimulus-response pairs and involves motor learning of a repeating sequence. Learning was computed as the difference in mean response time between the last sequence block and the last random blocks that immediately follows it (sequence-specific learning). Event-related potentials were analysed to measure ERN amplitude elicited by error commission.ResultsMean ERN amplitude difference between the first four learning blocks and the last four learning blocks of the SRT task correlated significantly with motor sequence learning as well as with overall response time improvement, such that those participants whose ERN amplitude most increased through learning blocks were also those who exhibited most SRT task improvements. In contrast, neither sequence-specific learning nor overall response time improvement across learning blocks were found to be related to averaged ERN amplitude from all learning blocks.ConclusionFindings from the present study suggest that the ERN amplitude changes from early to late learning blocks occurring over the course of the SRT task, as opposed to the averaged ERN amplitude from all learning blocks, is more closely associated with learning of a motor sequence. These findings propose an improved electrophysiological marker to index change in cognitive control efficiency during motor sequence learning.

This study extracted the error-related negativity (ERN) waveform component recorded from a visual-spatial attention and a visual short-term memory task to assess rigorously the long-term and cumulative effects of concussions on evaluative processes of cognitive control related to performance monitoring. This study demonstrates that, relative to control athletes, multiply concussed athletes show significant ERN amplitude reduction elicited by error generation. These cumulative effects of concussions on ERN amplitude were found in two distinct experimental paradigms designed to solicit concussion-sensitive cognitive abilities such as attention and short-term memory. This suggests that the mechanisms that contribute to the evaluation of cognitive performance may be significantly affected following multiple concussions even in low-conflict situations.

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These results support a genotypic effect of the BDNF Val66Met polymorphism on long-term olfactory function following a concussion in young female athletes.