Neuroanatomical correlates of memory and emotional functioning in temporal lobe epilepsy

Abstract

The present study examined the relationships between quantitative volume estimates of mesial temporal lobe structures based on structural magnetic resonance imaging (MRI) and the memory and emotional functioning of individuals with temporal lobe epilepsy (TLE). Twenty individuals identified as having TLE and 24 control participants were administered a test battery that included an experimental recognition memory test incorporating both verbal and nonverbal stimuli, an experimental test of emotional functioning that measured both subjective report and skin conductance response (SCR) to emotionally salient stimuli, and a battery of standardized tests and questionnaires assessing attention, personality, and emotion perception. Patients also completed standardized measures assessing intellectual function, memory, and quality of life. The patient group demonstrated deficits on tests of memory, attention, and emotion perception. Patients also demonstrated reduced SCR, however this result was found in response to both emotional and nonemotional stimuli and so is not necessarily indicative of deficits in emotional arousal. Inconsistent with expectations, patients reported normal experiential states of arousal in response to emotionally salient stimuli. MRI data were used to measure left- and right-hemisphere volumes of the hippocampus and amygdala in the patient group, and these volumes were used as predictors of performance on behavioral measures in multiple regression analyses. Consistent with predictions, reduced amygdala volume predicted lower arousal ratings to positive emotional stimuli. However, a similar relationship was not found for arousal ratings of negative stimuli. Other predicted relationships were not demonstrated. Amygdala volume did not show a relationship with SCR, and hippocampal volume did not show a relationship with memory performance. Additional hypotheses regarding the lateralization of hippocampal and amygdala function were not supported. Results of standardized tests suggested some potential relationships between hippocampal volume and attention, and between amygdala volume and psychological characteristics, although further research would be needed to establish the degree to which these results could be generalized to a larger population. Study findings support the continued development of NM morphometric techniques to predict patterns of strengths and weaknesses demonstrated by individuals with TLE.