Episodic and Semantic Memory: A Comparison of Amnesic and Demented Patients

Abstract

Episodic (recall of passages) and semantic (letter and category fluency) memory tasks were administered to Alzheimer's Disease (early stages), Huntington's Disease (HD), and alcoholic Korsakoff patients matched for overall severity of dementia. Although all three patient groups were severely (and equally) impaired on memory for passages, only the Alzheimer and Korsakoff patients emitted numerous intrusion errors. On the fluency tasks, the performance of the mild Alzheimer patients was distinguishable from that of the other two patient groups. On both fluency tasks, the HD and Korsakoff patients demonstrated severe and moderate deficits, respectively, whereas the mild Alzheimer patients were impaired only on the category fluency task. As with the episodic memory test, the Alzheimer and Korsakoff patients made more perseverative errors than did the HD patients on letter fluency. These findings suggest that Alzheimer and HD patients' impairments on episodic and semantic memory tasks reflect different underlying processes. The performance of Alzheimer patients is affected by their language dysfunction and an increased sensitivity to proactive interference; the deficits of the HD patients appear due to a general retrieval problem. Similarities in the error patterns (i.e., perseveration errors) of Alzheimer and Korsakoff patients are discussed with regard to recent neuropathological findings.

Verbal fluency in Huntington’s disease: a longitudinal analysis of phonemic and semantic clustering and switching

“…Firstly, the letter fluency task where they were required to orally generate as many words (excluding proper nouns and variants of the same root word) which began with the letters 'f', 'a' and 's' for 60 s each [4]. Secondly, for the category fluency task, patients were required to name as many animals as they could within a 60 s duration [7]. All responses were recorded verbatim.…”

“…exemplars which belong to a specified semantic category, such as 'animal'). The measure of performance most commonly used is the number of correctly generated words within 60 s. This measure is believed to tap frontal [9,10] and temporal [8,11,24] lobe function and is generally decreased in Huntington's disease (HD) patients relative to controls [5][6][7]36]. Indeed, there is some evidence for a decline in performance over time for letter [17] and category fluency in HD [2], despite the lack of cross-sectional difference for both letter and category fluency when comparing early versus late HD [5,6].…”

Inhibitory Control during Sentence Comprehension in Individuals with Dementia of the Alzheimer Type

“…For example, most researchers have found substantial increases in perseverative errors in DAT individuals (e.g., Butters et al 1987;Fuld, Katzman, Davies, & Terry, 1982;Helkala et al, 1989;Jacobs, Troster, Butters, Salmon, & Cermak, 1990;Loewenstein, D'Elia, Guterman, Eisdorfer, Wilkie, LaRue, Mintzer, & Duara, 1991;Shindler et al, 1984;Troster, Salmon, McCullough, & Butters, 1989). Fuld et al (1982) administered a wide range of neuropsychological tests to a variety of patients and found that prior-item intrusions (i.e., a delayed repetition of the appropriate response to a previous item) were more prominent in DAT than in other dementias (e.g., Multiple Cerebral Infarct, Korsakoff).…”

“…In fact, Shindler et al (1984) suggest that intrusion errors "... arise when subjects are unable to access correct responses from long-term memory and instead substitute erroneous responses selected from short-term memory." Butters et al (1987) also reported that when asked to listen to and recall short stories, individuals with DAT were more likely than controls, or even equivalently demented individuals with Huntington's disease, to produce prior-story intrusions (i.e., ideas from a previously presented story). Sandson and Albert (1987) reviewed the literature on perseverative errors and have proposed that the prominent increases in these errors in DAT are due to an inability to inhibit information inappropriate to the task at hand.…”

“…Studies of intrusion and perseverative errors (e.g., Butters, Granholm, Salmon, Grant, & Wolfe, 1987;Shindler, Caplan, & Hier, 1984), of selective attention (e.g., Spieler, Balota, & Faust, 1994;Sullivan, Faust, & Balota, 1994), and of word reading (e.g., Balota & Duchek, 1991;Balota & Ferraro, 1993;Patterson, Grahm, & Hodges, 1994) have demonstrated that DAT individuals not only suffer from breakdowns in inhibitory processes responsible for deactivating partially active task irrelevant information, as assessed by correct response latencies, but that they also suffer from a marked increase in the likelihood that task irrelevant information will interfere with information processing to the point that it is allowed to actually drive a response (i.e., an intrusion error). It is unclear at this point if this increased tendency to produce intrusion errors reflects breakdowns in inhibitory control among DAT individuals that is different in kind from the breakdowns indicated by analyses of correct response latencies, or simply reflects breakdowns that differ in their extent.…”