id_739. BRAIN MECHANISMS UNDERLYING IMPULSIVE RESPONSES DRIVEN BY TEMPORAL PREDICTABILITY: AN FMRI–EMG STUDY
Inga Korolczuk1,2, Marion Royer D’Halluin2,3,4, Bruno Nazarian5, Boris Burle2, Franck Vidal2, Jennifer T Coull2
1 Department of Psychology, Medical University of Lublin, Lublin, Poland
2 Centre for Research in Psychology and Neuroscience (UMR7077), Aix-Marseille University & CNRS, Marseille, France
3 CHU Sainte-Justine Research Center, Montréal, Québec, Canada
4 Department of Neurosciences, Université de Montréal, Montréal, Québec, Canada
5 Aix-Marseille Université, UMR 7289 CNRS, Institut de Neurosciences de la Timone, Marseille, Provence-Alpes-Côte d'Azur, 13005, France
INTRODUCTION: Previous work shows that temporal predictability speeds responding but increases impulsive errors during conflict tasks.
AIM(S): Here, we combined fMRI and EMG to identify the neural mechanisms underlying this effect.
METHOD(S): Twenty-four healthy adults performed a temporally cued Simon task. Visual pre-cues either predicted target onset (temporal cue) or provided no timing information (neutral cue). Participants responded to target shape (+/x) with left- or right-hand presses, while target location was either compatible or incompatible with the required response, inducing response conflict.
RESULTS: Behavioural results replicated earlier findings: temporal cues selectively increased fast impulsive errors on incompatible trials. fMRI analyses showed that temporal predictability recruited the left inferior parietal cortex (IPC) and left premotor cortex, regardless of response hand or compatibility. In contrast, response incompatibility activated the right putamen and right premotor cortex, independently of cueing. Critically, the interaction reflecting enhanced impulsivity for temporally predictable targets was associated with increased activity in left IPC.
CONCLUSIONS: This region, implicated in temporal attention and sensorimotor integration, may accelerate motor preparation based on temporal expectations, amplifying both correct and incorrect response tendencies. Importantly, overt errors capture only part of impulsive processing. EMG revealed that 16% of correct incompatible responses were preceded by subthreshold EMG activity in the incorrect hand (“partial errors”), which were rapidly suppressed. Temporal predictability significantly increased the frequency of these covert activations. Ongoing analyses aim to identify the neural substrates of partial errors to clarify how temporal predictability shapes the control of covert impulsive actions.
FINANCIAL SUPPORT: This work was supported by the National Science Centre of Poland grant (Sonatina 8, 2024/52/C/HS6/00009) awarded to Inga Korolczuk.