Temporal expectation based on the duration variability modulates alpha oscillations during working memory retention.

While maintaining information over a delay of time, working memory (WM) also allows individuals to prepare the mnemonic contents for prospective utilisation. However, it remains unclear whether the expectation of the time of WM test could modulate neural responses during the retention interval of WM and subsequent performance. Here, we investigated whether temporal expectations based on the variability of delay duration can modulate 9-13 Hz alpha oscillations during WM retention and whether the expectation-induced alpha activity was associated with WM performance. Participants performed a retro-cueing WM task with magnetoencephalography (MEG) (Experiment 1) and a standard WM task with electroencephalography (EEG) (Experiment 2). The expectation of the timing of the WM test was manipulated by the temporal structure of the tasks with small or large variability in the delay durations. We showed that alpha oscillations during retention interval and WM performance varied with duration variability in both of the MEG and EEG experiments. The novel finding was greater alpha-power attenuation over the left frontal and parietal regions during WM retention when the duration variability was small and the test onset was predictable, compared to when the duration variability was large and the test onset was less predictable. Importantly, we observed a positive relationship in variability difference between the response benefit and alpha-power attenuation in the left posterior parietal regions at both MEG-source and EEG-electrode levels. Finally, we confirmed the behavioural benefit when a condition with a fixed delay-duration was included in a behavioural experiment (Experiment 3). When conjoined, the delay duration enables individuals to anticipate when the relevant information would be put to work, and alpha oscillations track the anticipatory states during WM maintenance.

Temporal profiles of cortical oscillations in novice performers for goal-directed aiming in a shooting task.

Goal-directed aiming relies on the ability to control attention and visuomotor movements while preparing for motor execution. Research in precision sports has investigated cortical oscillations for supporting expert performance. However, the results may be influenced by adaptive and strategic behaviors after intensive training. Whether and at what time points distinctive oscillations support goal-directed aiming without such training remains elusive. In this electroencephalographic (EEG) study, we investigated how the theta, alpha and beta oscillations change to support accurate aiming before novices took an action. We first conducted a model-based analysis to examine the correlation of cortical oscillations with accurate shooting on a trial-by-trial basis in a within-individual manner. The results showed that alpha and beta oscillations at different time points during the aiming period were better predictors of aiming accuracy. We then compared the oscillatory power for good versus poor performance. The results showed decreases in the alpha and beta power across distributed cortical areas and an increase in the frontal theta power successively before shot release. Moreover, greater intertrial phase coherence was observed for good performance than for poor performance in posterior alpha activity and anterior beta activity during the aiming period. In conclusion, these results advance our understanding of the temporal dynamics of theta, alpha and beta oscillations in orchestrating goal setting, motor preparation and focused attention to monitoring both external and internal states for accurate aiming. Among the three, alpha and beta oscillations are critical for predicting aiming performance and theta oscillations reflect effortful cognitive control.