Abstracts

Rationale: Previous research suggests that patients with temporal lobe epilepsy [TLE] have difficulty recollecting personal life events i.e., autobiographic memories. These studies have largely focused on localizing different components of this deficit to various regions of the left and right temporal lobes, with limited consideration of the effects of seizures. Our aim was to investigate the rôle of epileptological factors in determining the nature of the autobiographic memory impairment commonly seen in people with TLE. Methods: We prospectively assessed 23 patients with medically-refractory TLE, recruited from the Comprehensive Epilepsy Program of Austin Health, Melbourne Australia. Their performances on widely-used measures of autobiographic memory were compared to those of a sociodemographically-matched healthy control sample (n = 37; N = 60). Epilepsy variables of interest included International League Against Epilepsy seizure classification, duration of epilepsy, age at seizure onset, seizure frequency, surgical candidacy, presence of a lesion on neuroimaging, and pharmacotherapy. Participants also completed a screen of psychological functioning, including mood, as part of a larger behavioral study. Controls were significantly older than patients (p = .016), but otherwise did not differ on demographic variables (p > .05). Results: When asked to recall incidences from their life that were precisely located in place and time (episodic autobiographic memory), patients with TLE recollected significantly less than controls (p = .023), and produced more responses that summarized multiple incidences over time (p = .035). Poor episodic autobiographic recall in patients was related to younger age at onset of epilepsy (especially < 20yrs, r = .58; p < .001) and longer duration of epilepsy (r = .38). These two factors were correlated (r = .46; p= .03) and represent the chronicity of illness. There was also a trend for poor episodic recall to relate to stronger endorsement of current mood symptoms (anxiety, r = .38; depression, r = .33). In contrast, impoverished semantic autobiographic recall (knowledge of names and other personally relevant ‘facts') was associated with younger age at testing (r = .46; p < .01). Conclusions: This study provides initial evidence that habitual seizures contribute to the poor recall of autobiographic events in people with TLE, in addition to temporal lobe pathology. Our findings indicate that chronic epilepsy can undermine the episodic element of autobiographic memory recall, but may not effect semantic knowledge associated with personal life events. The results are consistent with psychiatric research suggesting that lowered mood can impair episodic autobiographic memory. We propose that habitual seizures fundamentally disturb the patients' ability to vividly recall personal life events by interrupting the encoding of autobiographic memories, as well as limiting the breadth of coherent life experiences from which autobiographic memories are drawn.