Frontal theta predicts specific cognitive control-induced behavioural changes beyond general reaction time slowing

Abstract

Investigations into the neurophysiological underpinnings of control suggest that frontal theta activity is increased with the need for control. However, these studies typically show this link by reporting associations between increased theta and RT slowing - a process that is contemporaneous with cognitive control but does not strictly reflect the specific use of control. In this study, we assessed frontal theta responses that underpinned the switch cost in task switching - a specific index of cognitive control that does not rely exclusively on RT slowing. Here, we utilised a single-trial regression approach to assess 1) how cognitive control demands beyond simple RT slowing were linked to midfrontal theta and 2) whether midfrontal theta effects remained stable over time. In a large cohort that included a longitudinal subsample, we found that midfrontal theta was modulated by switch costs, with enhanced theta power when preparing to switch vs. repeating a task. These effects were reliable after a two-year interval (Cronbach's α.39-0.74). In contrast, we found that trial-by-trial modulations of midfrontal theta power predicted the size of the switch cost - so that switch trials with increased theta produced smaller switch costs. Interestingly, these relationships between theta and behaviour were less stable over time (Cronbach's α 0-0.61), with participants first using both delta and theta bands to influence behaviour whereas after two years only theta associations with behaviour remained. Together, these findings suggest midfrontal theta supports the need for control beyond simple RT slowing and reveal that midfrontal theta effects remain relatively stable over time.

Keywords: Cognitive control; Medial prefrontal cortex; Midfrontal theta; Single trial regression; Task switch; Theta.

Fig. 1.. Task switching paradigm.

A) Trial structure and example S-R mapping. Note, the trial sequence here serves as the previous trial for definitions of cue types in 1B. B) Cue types; whereby informative cues indicate the task to be prepared while noninformative do not. If the same task is presented on successive trials it is deemed a repeat trial (here letter – letter). If a different task is presented on successive trials it is deemed a switch trial (here letter – digit).

Fig. 2.. Behavioural results for Phase 1, Phase 2 and outsample groups.

Top row, RT; bottom row, error rate. Violin plots (created using Gramm; Morel, 2018, March 4) represent the distribution of each data series, with a box plot and whisker drawn over these data (notch centre = median). IR, informative repeat; IS, informative switch; NI, noninformative.

Fig. 3.. Power ANOVA results.

Top row, F-statistic maps for Main Effects Trial Type for Phase 1 and Phase 2. Bottom row, contrast-maps indicating the direction of effect associated with ANOVA results for Switch – Repeat and Informative – Noninformative simple effects. For ANOVAs, white outlines indicate significant pixels associated with permutation testing. For simple effects we present uncorrected p-values from t-tests (white outlines at p < .05) for completeness but restrict interpretation to those time-frequency associated with the main effect of Condition. Cue and target onset are shown with dashed lines at 0 and 1000 ms respectively. The average RT for all conditions ±1 SD is shown to demonstrate peri-response ranges.

Fig. 4.. Conjunction analyses showing common significant time×frequency pixels across Phase 1 and Phase 2.

Yellow patches depict significant time × frequency pixels that were present in both Phase 1 and Phase 2 for A) power and B) regression one-way ANOVA analyses.

Fig. 5.. Single-trial regression ANOVA results.

Top row, F-statistic maps for Main Effects Trial Type for Phase 1 and Phase 2. Bottom row, contrast-maps indicating the direction of effect associated with ANOVA results for Switch – Repeat and Informative – Noninformative simple effects. For ANOVAs, white outlines indicate significant pixels associated with permutation testing. For simple effects we present uncorrected p-values from t-tests (white outlines at p < .05) for completeness but restrict interpretation to those time-frequency associated with the main effect of Condition. Cue and target onset are shown with dashed lines at 0 and 1000 ms respectively. The average RT for all conditions ±1 SD is shown to demonstrate peri-response ranges.

Fig. 6.. Reliability of power and regression values between Phase 1 and Phase 2.

Cronbach’s alpha values for condition-averaged power and regression are depicted as time-frequency maps. 0 ms; cue onset, 1000 ms; target onset. White outlines indicate alpha values > .4; blue outlines indicate alpha values > .6.