Accelerated forgetting in patients with epilepsy: evidence for an impairment in memory consolidation.

Patients with epilepsy frequently complain of memory difficulties yet perform normally on standard neuropsychological tests of memory. It has been suggested that this may be due to an impairment of very long-term memory consolidation processes, beyond those normally assessed in the neuropsychological clinic. We carried out a prospective study of verbal memory over a long-term retention interval of 8 weeks in patients with epilepsy and in controls. Results were compared with performance on conventional tests of memory. Despite normal learning and retention over 30 min, patients with epileptic foci in the left temporal lobe performed disproportionately poorly on the long-term test compared with both patients with epileptic foci in the right temporal lobe and controls. Our findings provide evidence for an extended period of memory consolidation and point to the critical region for this process, at least for verbal material, in the left temporal lobe. The implications of our findings for clinical assessment and therapeutic management of patients with epilepsy are discussed.

[1]  R. Corcoran,et al.  Memory failure in epilepsy: retrospective reports and prospective recordings , 1992, Seizure.

[2]  R. Snaith,et al.  The Hospital Anxiety and Depression Scale , 1983 .

[3]  R Philip Snaith.  The Hospital Anxiety And Depression Scale , 1986, British medical journal.

[4]  E. Lugaresi,et al.  Epilepsy Presenting as Memory Disturbances , 1988, Epilepsia.

[5]  S. Baxendale.  The hippocampus: Functional and structural correlations , 1995, Seizure.

[6]  N. Kapur,et al.  Very Long-Term Amnesia in Association with Temporal Lobe Epilepsy: Evidence for Multiple-Stage Consolidation Processes , 1997, Brain and Cognition.

[7]  M. Mesulam,et al.  Accelerated Forgetting in Association with Temporal Lobe Epilepsy and Paraneoplastic Encephalitis , 1997, Brain and Cognition.

[8]  H. Nelson.  A Modified Card Sorting Test Sensitive to Frontal Lobe Defects , 1976, Cortex.

[9]  Herbert Weingartner,et al.  Memory consolidation : psychobiology of cognition , 1984 .

[10]  D. Benson,et al.  Interictal memory and language impairment in temporal lobe epilepsy , 1980, Neurology.

[11]  S. Shorvon,et al.  The effect of seizures on memory for recently learned material , 1995, Neurology.

[12]  C. Reynolds,et al.  Wechsler memory scale-revised , 1988 .

[13]  F. Huppert,et al.  Normal and Abnormal Forgetting in Organic Amnesia: Effect of Locus of Lesion , 1979, Cortex.

[14]  J. Hodges,et al.  Transient epileptic amnesia: a description of the clinical and neuropsychological features in 10 cases and a review of the literature , 1998, Journal of neurology, neurosurgery, and psychiatry.

[15]  Gregory P. Lee,et al.  Impaired Long-Term Retention Despite Normal Verbal Learning in Patients With Temporal Lobe Dysfunction , 1991 .

[16]  A. Aldenkamp,et al.  Memory complaints in epilepsy: correlations with cognitive performance and neuroticism , 1993, Epilepsy Research.

[17]  A. Wyler,et al.  Adequacy of Language Function and Verbal Memory Performance in Unilateral Temporal Lobe Epilepsy , 1992, Cortex.

[18]  L. Cermak.  Human memory and amnesia , 1982 .

[19]  L. Squire,et al.  Retrograde amnesia and memory consolidation: a neurobiological perspective , 1995, Current Opinion in Neurobiology.

[20]  A. Connelly,et al.  The Relationship Between Quantitative MRI and Neuropsychological Functioning in Temporal Lobe Epilepsy , 1998, Epilepsia.

[21]  R. Corcoran,et al.  Everyday Memory Failures in People with Epilepsy , 1992, Epilepsia.