From age-related to inter-individual differences Exploring the diversity of cognitive control phenomena via brain-behaviour correlations Eva Mennigen 1, Thomas Hübner 1, Kathrin U. Müller 1, Stephan Ripke 1, Sarah Rodehacke 1, Dirk Schmidt 1, Hannes Ruge 1, Thomas Goschke 1 & Michael N. Smolka 1 1 Neuroimaging Center, Technische Universität Dresden, Germany Introduction Cognitive control represents the ability to flexibly adapt to environmental challenges. It is a fundamental ability that develops in childhood reaching a mature level not until late adolescence (Luna et al., 2010). It is a common assumption that the anterior cingulate cortex (ACC), the dorsolateral prefrontal cortex (DLPFC), the pre-supplementary motor area (preSMA) and the posterior parietal cortex (PPC) subserve the coordination of these control processes (Kerns et al., 2004; Botvinick et al., 2004; Brass et al., 2005; Liston et al. 2006). Cognitive control processes might be strongly modulated by inter- individual differences as indexed by behavioural performance measures – especially in adolescence, a highly variable proceeding time period. Neural correlates of adolescent cognitive control are still poorly understood and studies show inconsistent findings. Therefore we examined the possible linkage between behavioural indices (i.e. mean reaction times, RT) and mean brain activations of two core cognitive control processes: switch costs and the effect of incongruence. Methods Sample: 185 healthy adolescents (93 females), mean age 14.5 years (SD 0.3), were investigated with BOLD fMRI in a 3T MR scanner during they performed the following task. Task: The present interference switching task design is shown in figure 1. The stimuli can be congruent (i.e. relevant and irrelevant stimulus dimension triggering the same response) or incongruent (i.e. triggering different responses). The two different task rules can be repeated (task repetition trials) or switched (task switch trials). The task was modelled as a 2*2 within-subject design with the factors task transition (task switch trials vs. task repetition trials) and present trial congruence (i.e. congruent trials vs. incongruent trials) resulting in 4 different conditions. Behavioural data analyses: Behavioural data were analysed via a 2*2 repeated measure ANOVA as well as via a correlation analysis regarding the two behavioural indices (effect of incongruence and switch costs). Error rates, mean RT and related standard deviations (SD) were calculated subject-wise for each condition. The calculations were based on the 2*2 design including the factors task transition and present trial congruence. For brain- behaviour correlations we calculated the behavioural indices ‘effect of incongruence’ as difference between mean RT for incongruent trials (I) and mean RT for congruent trials (C) (mean RT I - C) and ‘switch costs’ as difference between mean RT for task switch trials (sw) and task repeat trials (rp) (mean RT sw – rp). Imaging data analyses: First level analysis of pre-processed BOLD data included modelling of all effects of interest based on trial onsets. Single subject regressors were built on a 2*2*2*2 design including the factors task, task transition, previous and present trial congruence. Error trials, post-error trials and missing trials were modelled as separate regressors. As we were especially interested in task main effects we ran a 2*2 full-factorial model including the two behavioural indices (effect of incongruence and switch costs) as covariates for a second level group analysis. SPM5 was used for all imaging data analyses. Discussion The observed behavioural effects speak for a greater demand of cognitive control resource activation in task switch trials as well as in incongruent trials offering an explanation for the increase in RT and ER as well as for the increased BOLD activation effects on imaging level. The analysis of individual performance differences demonstrated that neural activation effects in the incongruent>congruent contrast are correlated with the individual behavioural effect of incongruence: The higher the behavioural index the higher the observed increase in neuronal activity in incongruent trials relative to congruent trials. This suggests that these differences might be a possible cause for inconsistent findings in previous fMRI studies on cognitive control (Braver et al., 2010). Additionally, our findings support the ‘neural efficiency theory’ which states that a proficient behavioural performance is accompanied by less neural activation effects (Haier et al., 1992; Graham et al., 2010). Furthermore we found that adolescents recruit the same cortical and subcortical core areas for the processing of task switching and incongruence, somewhat contradicting the fact that both phenomena did not correlate on the behavioural level. In addition, we did not find a brain-behaviour correlation for the task switch effect, but for the effect of incongruence. Taken together, these findings might suggest that the observed cognitive control phenomena proceed on different difficulty levels: the influence of inter-individual differences is more pronounced in more difficult tasks (i.e. the effect of incongruence). References 1. Botvinick MM, Cohen JD, Carter CS (2004): Conflict monitoring and anterior cingulate cortex: an update. 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Science 303: Liston C, Matalon S, Hare TA, Davidson MC, Casey BJ (2006): Anterior cingulate and posterior parietal cortices are sensitive to dissociable forms of conflict in a task-switching paradigm. Neuron 50: Luna B, Padmanabhan A, O'Hearn K (2010): What has fMRI told us about the development of cognitive control through adolescence? Brain Cogn 72: This research was supported by the Grant# BMBF 01EV0711 contact: Fig. 1: a) The interference switching task b) The 2*2 design with balanced trial count Results – Behavioural Data Behavioural data analysis revealed a significant slowing in reaction time (RT; Fig. 2) and a significant increase of error rate (ER; Fig. 3) for incongruent relative to congruent trials (both p<0.001) and for task switch trials relative to task repetition trials (both p<0.001). Furthermore, these analyses displayed a significant interaction ‘present trial congruence * task transition’ for RT as well as for ER (both p<0.001). Correlation analysis for the behavioural effect of incongruence and switch costs did not reveal a significant correlation (Pearson r =.001). Fig. 2 RT with error bars SEMFig. 3 ER with error bars SEM Task transition Present trial congruence repeatswitch Congruent64 trials Incongruent64 trials Results – Imaging Data The full-factorial design analysis of BOLD data revealed reliable task main effects for the switch>repeat contrast (Fig. 4) and for the incongruent>congruent contrast (Fig. 5). Effects of task transition Effects of present trial congruence Considering the behavioural effect of incongruence as covariate showed a positive correlation between the behavioural parameter and BOLD activation effects in the dACC and DLPFC (Fig. 6) for the incongruent>congruent contrast. Applying the same procedure to the switch>repeat contrast and the behavioural switch costs did not reveal any correlation. The overlap of brain activations of these latter congruency- related activation effects and the switch>repeat activation effects were pronounced in a conjunction analysis (Fig. 7). This analysis revealed overlaps between both effects in the PPC, ACC and preSMA. Effects of inter-individual differences Effects of overlap Fig. 4 The switch>repeat contrast revealed a network comprising the dACC, preSMA, DLPFC and PPC; activation effects were more pronounced in the left hemisphere than in the right one; p<0.05, FWE corrected, 25 adjacent voxel, threshold t = 4.54 Fig. 5 The incongruent>congruent contrast revealed less distinct activation effects in the dACC, preSMA and PPC; p<0.001, uncorrected, 25 adjacent voxel, threshold t = 3.1 Fig. 6 The positive correlation of the behavioural effect of incongruence (mean RT I - C) on the incongruent>congruent contrast showed performance-dependent activation effects in the DLPFC, dACC, preSMA and PPC; p<0.001, uncorrected, 25 adjacent voxel, threshold t = 3.1 Fig. 7 The conjunction analysis exposed an overlapping network serving the task transition process as well as the processing of incongruent trials (dACC, preSMA, PPC); p<0.001, uncorrected, 25 adjacent voxel, threshold t = 3.1 Joystick movable to 4 directions (left, right, up and down) for trial by trial responses to the arrow-direction vs. dot-location Trial n congruent: an oval task-cue, i.e. consider the dot-location - duration of 2100ms Fixation-cross - duration of 1800ms (ITI) Trial n+1 incongruent: a rectangular task- cue, i.e. consider the arrow-direction Ongoing task (256 trials) Task switch RT in msecER in percent