EP 123. Impaired conflict processing in patients with hippocampal sclerosis

Abstract

Introduction Hippocampal sclerosis (HS) frequently underlies temporal lobe epilepsy. Patients often suffer from refractory epileptic seizures, but episodic memory deficits, depressive syndromes or impaired special navigation are also common symptoms. Much less is known about the role of the hippocampus for conflict processing. Patients with impaired conflict processing show specific behavioral deficits. They lack goal-directed behavior, are more distractible or have personality characteristics such as unsteadiness, emotional instability, with frequent and rapid mood changes. Early evidence for a hippocampal role in conflict processing comes from Gray’s 1982 model of anxiety, which suggests that the hippocampus supports avoidance behavior during approach-avoidance-conflicts. In addition, the hippocampus is thought to be important for inhibitory learning, a fundamental process that might modulate higher cognitive functions like memory or even conflict processing ( Chan et al., 2001 ). A recent fMRI-EEG study confirmed a role of the human hippocampus for conflict processing by showing hippocampal activity during cognitive conflicts in an auditory stroop task ( Oehrn et al., 2015 ). Here we investigate how hippocampal damage relates to deficits in conflict processing. Methods Patients with temporal lobe epilepsy and HS, patients with TLE and a temporolateral lesion and 27 healthy controls perform the auditory stroop task. Subjects listen to the words “high”, “low” and “good” (semantic aspect) in a low or high pitch (phonetic aspect). Semantic and phonetic aspects either matched (congruent condition) or contradicted (incongruent condition). Results So far, we collected data from two patients with HS and 27 healthy controls. Patients show higher conflict-related slowing of response time (166 ms ± 94) than healthy controls (68 ms ± 53). Patients also show less correct responses during conflict (61% ± 51) compared to non-conflict condition (86% ± 19). However, healthy controls responded correctly in most trials during incongruent (99% ± 1) and congruent condition (95% ± 8). Conclusions The preliminary descriptive data indicate conflict-related slowing of information processing in patients with hippocampal damage. The findings can further our understanding of the role of the hippocampus for conflict processing. It may also help to explain psychiatric comorbidities in patients with temporal lobe epilepsy.