Emotional and Cognitive Performance of Left and Right Mesial Temporal Lobes in Epileptic Patients Without Brain Abnormalities

Introduction: Patients with temporal lobe epilepsy (TLE) often experience cognitive and emotional impairments even when brain imaging shows no detectable abnormalities. The precise roles of the left and right mesial temporal lobes—specifically the hippocampus and amygdala—in these deficits are not well understood.To evaluate the emotional and cognitive performance associated with the left and right hippocampus and amygdala in epilepsy patients without brain abnormalities, utilizing intracranial electroencephalography (iEEG) to identify functional differences.

Methods: Six patients with pharmacoresistant complex partial seizures but normal MRI scans underwent invasive iEEG monitoring. Participants performed two conflict-based tasks: the Multi-Source Interference Task (MSIT) to assess cognitive processing and the Emotional Conflict Resolution (ECR) task to evaluate emotional processing. Neural activity in the hippocampus and amygdala was recorded and analyzed using event-related potentials (ERPs), time-frequency analysis, and phase slope index (PSI) connectivity.

Results: Reaction times were significantly longer during MSIT conditions compared to ECR conditions (P < 0.0001), and longer in incongruent conditions than in congruent ones for both tasks. ERPs revealed distinct activation patterns in the left and right hippocampus and amygdala. Incongruent conditions elicited significant late activations, particularly in the left hippocampus and right amygdala. Time-frequency analysis showed notable differences in gamma-band activity between conditions, with higher gamma activity in the amygdala during the MSIT incongruent condition and in the hippocampus during the ECR incongruent and MSIT congruent conditions (P < 0.05). PSI analysis demonstrated stronger connectivity in the temporal lobes during the MSIT task compared to the ECR task (P < 0.05), suggesting greater neural coordination required for resolving cognitive interference.

Conclusion : Tasks involving cognitive and emotional conflict, especially incongruent conditions, lead to increased activation and connectivity in the mesial temporal lobes, notably the hippocampus and amygdala. These findings indicate differential engagement of temporal lobe regions depending on task demands and hemispheric specialization. Understanding these neural dynamics may inform targeted interventions to alleviate cognitive and emotional impairments in TLE patients without detectable brain abnormalities.