Remote semantic memory in patients with Korsakoff's syndrome and herpes encephalitis.

Abstract

Performance of patients with Korsakoff's syndrome and herpes encephalitis was compared on a retrograde amnesia (RA) test, asking subjects to recall and recognize the definitions of words that had come into the language at different time periods. Performance was also compared on a related test in which participants were asked to produce the words to definitions they were given in free recall and cued recall versions. It was hypothesized that, if the temporal gradient in remote memory results from a shift of information from episodic to semantic memory, then there should be a temporal gradient on these tasks, possibly steeper (i.e., greater relative sparing of early memories) in the patients in the Korsakoff group than in the herpes encephalitis group, who have widespread temporal lobe damage. Furthermore, in comparing semantic and episodic remote memory tests, consolidation theory would predict uniform temporal gradients across such tasks, whereas multiple trace theory would predict a differential pattern. The results showed that patients with Korsakoff's syndrome and patients with herpes encephalitis were significantly impaired across all time periods on the vocabulary tests, with only minimal evidence of temporal gradients, relative to healthy participants, and there was no evidence of a differential pattern of impairment between the two patient groups. Comparison with performance on measures of episodic retrograde amnesia, in which there was a differential pattern of temporal gradient, suggests that the relative preservation of early episodic remote memories in patients with Korsakoff's syndrome does not result from an episodic-to-semantic shift in the quality with which memories are stored. These findings are discussed in relation to existing theories of RA and to the patients' underlying patterns of neuropathology.

Mediodorsal thalamus and cognition in non-human primates

“…Analyses in humans with thalamic damage have implicated the mammillothalamic tract, in particular, in impaired formation of new memories (anterograde amnesia) (Van der Werf et al, 2000, 2003). Individuals with Korsakoff syndrome (and widespread diencephalic degeneration) have extensive impairment in retrieval of memories formed before brain damage was sustained (retrograde amnesia), but retrograde amnesia is not associated with focal lesions of the thalamus (Kopelman et al, 1999, 2009). An initial investigation in monkeys reported no retrograde amnesia after focal neurotoxic lesions of the medial part of MD, but a significant anterograde amnesia (Mitchell and Gaffan, 2008), congruent to some degree with the clinical literature.…”

Applicability of the Rivermead Behavioural Memory Test – Third Edition (RBMT-3) in Korsakoff's syndrome and chronic alcoholics

“…Also, some studies have reported hippocampal atrophy in KS patients 20,21. As a result, long-term storage of new information is hampered by a deficit in consolidation,22 which strongly relies on medialtemporal lobe and diencephalic structures 2. Looking at the type of task that is tested after a delay, recognition tasks such as Face Recognition or Picture Recognition do not improve the memory performance, which also points towards a consolidation deficit rather than impaired retrieval, as in the latter recognition performance is expected to improve substantially 23.…”

“…Finally, it should be noted that not all aspects of memory can be examined using the RBMT-3. That is, the test does not include subtests assessing working memory or semantic memory, which would be relevant as deficits in these memory functions have also been demonstrated in Korsakoff patients 22,33,34…”

Medio-dorsal thalamus and confabulations: Evidence from a clinical case and combined MRI/DTI study

“…From an imaging perspective, patients with KS have been shown to have hyperintensities in diencephalic, mesencephalic (Cerase et al, 2011), hypothalamic (Ptak et al, 2001), encephalic (Kopelman et al, 2009, Victor et al, 1971) and cerebellar (Laureno, 2012) structures.…”