The nature of anterograde and retrograde memory impairment after damage to the medial temporal lobe

• Published in: Neuropsychologia 2013-11, Vol.51 (13), p.2709-2714
• Main Authors: Smith, Christine N., Frascino, Jennifer C., Hopkins, Ramona O., Squire, Larry R.
• Format: Article
• Language: English
• Subjects: Adult; Adult and adolescent clinical studies; Aged; Amnesia, Anterograde - etiology; Amnesia, Retrograde - etiology; Anterograde amnesia; Association Learning - physiology; Biological and medical sciences; Brain Injuries - complications; Disorders of higher nervous function. Focal brain diseases. Central vestibular syndrome and deafness. Brain stem syndromes; Female; Humans; Male; Medial temporal lobe; Medical sciences; Memory; Mental Recall - physiology; Middle Aged; Nervous system (semeiology, syndromes); Neurology; Neuropsychological Tests; Organic mental disorders. Neuropsychology; Psychiatric Status Rating Scales; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Retrograde amnesia; Severity of Illness Index; Temporal Lobe - pathology; Time Factors; Verbal Learning
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2013.09.015

The study of anterograde and retrograde amnesia (AA and RA) in the laboratory and the clinic has provided important information about the structure and organization of memory. The severity of AA is usually correlated with the severity of RA. Nevertheless, variations in the expression of AA and RA have been reported, which presumably reflect variation in the locus and extent of brain damage. The relationship between AA and RA has rarely been described quantitatively in groups of patients where detailed anatomical information is available. We have quantified the severity of AA and RA for factual information in 11 memory-impaired patients with bilateral medial temporal lobe lesions, including 5 for whom detailed post-mortem neurohistological information was available. The findings describe an orderly relationship between AA and RA, such that patients with more severe AA also had more extensive RA. In addition, RA was measurable only after AA reached a substantial level of severity. This relationship between AA and RA in patients with identified medial temporal lobe lesions appears to describe a general principle, which applies to a range of etiologies, including traumatic amnesia, where the locus and extent of brain damage is less well understood. Whenever patients deviate substantially from the relationship described here, one should be alert to the likelihood that significant damage has occurred outside or in addition to the structures in the medial temporal lobe. •Orderly relationship between the severity of anterograde (AA) and retrograde amnesia (RA).•Easier to disrupt new learning ability; harder to disrupt information already acquired.•RA measurable only after AA reaches a substantial level of severity.•Severity of AA and RA related to severity of medial temporal lobe damage (MTL).•Deviations from the AA–RA relationship described here suggest damage outside of the MTL.