Laird S. Cermak

The encoding capacity of a patient with amnesia due to encephalitis

Abstract A patient with amnesia due to encephalitis was examined in an effort to identify the factors that might contribute to his memory disturbances. It was discovered that this patient had the ability to analyze incoming verbal information on a level comparable to that achieved by normals. Furthermore, this ability enabled him to retain a limited amount of information for a brief interval, but, as soon as further information was introduced, it appeared to displace completely the older information in his working memory. As a consequence, information never seemed to be consolidated into permanent, long-term, memory. Several attempts to increase the amount of information that could be consolidated (e.g. through use of visual imagery, verbal mediation, etc.) were attempted with promising, yet limited, results.

Some analyses of the verbal encoding deficit of alcoholic Korsakoff patients

Abstract Two experiments were designed to assess Korsakoff patients ability to encode verbal information on the basis of its physical, nominal and semantic properties. The first investigation employed Wickens release from proactive interference (PI) technique; a procedure that allows an assessment of a subjects ability to encode verbal information on the basis of its semantic properties. It was discovered that on tasks involving only a rudimentary verbal analysis, such as the ability to discriminate letters from numbers, the Korsakoff patients demonstrated a normal release from PI. However, on tasks that required a more sophisticated level of semantic encoding, such as those based on taxonomic class inclusion, the patients failed to show release from PI. The second investigation employed Posners reaction time technique which assesses a subjects ability to encode the physical and nominal properties of simple verbal materials (letters). The results of this study showed that Korsakoff patients are impaired on even these rudimentary encoding tasks, which led to the proposal that Korsakoff patients semantic encoding deficit might stem from an initial impairment in the speed at which physical and nominal properties of verbal information are analyzed.

The extent of the verbal encoding ability of Korsakoff patients

Abstract Four experiments were designed to determine the extent of Korsakoff patients ability to encode semantically meaningful verbal material. The first experiment demonstrated that these patients are aided by category cues following a one min retention interval. The remaining experiments, which also employed cueing techniques demonstrated that Korsakoff patients, with instructions, can encode on acoustic, associative, and semantic levels. When left to their own preferences, however, the Korsakoff patients rely upon acoustic and associative encoding. This failure to employ semantic encoding strategies spontaneously may underlie their overall inability to retain verbal material.

Imagery as an Aid to Retrieval for Korsakoff Patients

Six Korsakoff patients and six alcoholic controls learned a five item P-A task under each of the following three learning conditions; Rote, Imagery, and Cued learning. Under all conditions the Korsakoff patients took more trials to learn than did the control patients. However, both imagery learning and cued learning were easier than rote learning for the Korsakoff patients when recall was used as the learning index. When a recognition measure was used instead of the recall, imagery learning proved easiest with no difference existing between cued and rote learning. In a second experiment, the patients were given the cue (a mediating link) during presentation, but not during retrieval. Under this condition the Korsakoff patients learned no more rapidly than they did by rote regardless which response measure was required. It was concluded that imagery can aid both storage and retrieval of verbal information for Korsakoff patients, while cuing aids only the retrieval process.

Verbal retention deficits in aphasic and amnesic patients

Abstract Five different groups of patients (aphasics, alcoholic Korsakoffs, nondominant hemisphere patients, alcoholics, and control patients) were asked to detect either repeated letters, repeated words, rhyming words, or words from the same category during the reading of a list. It was discovered that the number of intervening words had a greater effect on the aphasics for all conditions than it did for the other groups. However, when the rate of presentation was slowed, the aphasics showed considerable improvement while the other groups maintained their same level of performance. The Korsakoff patients were impaired only on the semantic task (same category inclusion) and did not improve at the slower presentation rate. An interpretation based on speed and level of information processing abilities is given.

Rehearsal strategies of alcoholic Korsakoff patients.

Abstract An overt rehearsal procedure was used to monitor the rehearsal strategies that Alcoholic Korsakoff, Chronic Alcoholic, and Normal Control patients used when learning a 20-item list. It was found that Korsakoff patients spontaneously rehearse only one word at a time, that word being the one currently presented, regardless of the organizational salience of the list of words. Alcholics and Control patients, on the other hand, tended to rehearse several words in addition to the one being currently presented, and they demonstrated increasing ability to rehearse semantically related words together as the organizational salience of the list increased. This ability to rehearse in an enriched manner placed the two control groups at a distinct advantage over the Korsakoff patients at the time of recalling the list.

Material-specific memory deficits in alcoholic Korsakoff patients

Abstract The short-term memory disorders of alcoholic Korsakoff patients were examined for material- and modality-specific deficits. Verbal and non-verbal memory tasks employing the visual, auditory, and tactile modalities were administered to Korsakoff patients and to alcoholic and non-alcoholic control subjects. In all three modalities the Korsakoff patients demonstrated normal short-term retention of non-verbal materials but severe memory deficits for verbal materials. These findings are consistent with the hypothesis that failures in verbal encoding underlie these patients memory difficulties.

Repetition effects in a lexical decision task: The role of episodic memory in the performance of alcoholic Korsakoff patients

To examine the contribution of episodic memory to the successful verbal priming performance of Korsakoff patients, we adapted a lexical decision task which holds constant the processing demands during study and testing. Words and nonwords were repeated at a lag of 0, 1, 3, 8 and 15 items and the decrease in response latency was taken as a measure of priming. In Experiment 1, Korsakoff patients showed repetition priming of a magnitude similar to that obtained by alcoholic controls, even at a lag of 15 intervening items. Experiment 2 explored the effect of word frequency on repetition priming. Korsakoff patients again showed normal priming up to lags of 15, and, as expected, these repetition effects were larger for low frequency than for high frequency words. This outcome was felt to be more consistent with an episodically based familiarity account than with a semantic activation account. Finally, Korsakoff patients were found to be impaired in their ability to use episodic memory in an explicit memory task that used the same material under comparable presentation conditions (Experiment 3). Contemporary processing models of episodic memory are discussed as possible explanations for the successful implicit memory performance by amnesic patients on this task.

Korsakoff patients' nonverbal vs verbal memory: Effects of interference and mediation on rate of information loss

Abstract Two experiments were performed to assess the roles of interference and mediation on Korsakoff patients rate of nonverbal information loss. In the first, which contrasted the rate of nonverbal information loss following nonverbal distraction with the rate of verbal information loss following verbal distraction, it was discovered that nonverbal information was forgotten more rapidly than verbal information. Furthermore, nonverbal material was forgotten across unfilled retention intervals, while verbal material remained intact. In a second experiment, the patients were given verbal labels to aid their retention of nonverbal information. Since these labels improved nonverbal retention, it was concluded that they had provided the Korsakoff patient with a means for rehearsing the nonverbal information.

Episodic Effects on Picture Identification for Alcoholic Korsakoff Patients

Experience with degraded pictures produces better subsequent identification of these pictures in amnesic patients. To examine the contribution of episodic memory to this facilitation, we compared identification of pictures that were identical to a studied picture, pictures that shared the same name with a studied picture, and new, unstudied pictures. In an initial phase of the experiment, patients clarified each picture until they could name it. During a second phase, they again clarified each picture and judged whether it was identical, similar (same-name), or different from pictures identified in the first phase. Korsakoff patients, as well as alcoholic controls, identified identical pictures faster than same-name pictures, and these in turn were identified faster than new pictures. The Korsakoff patients did show less facilitation than the alcoholic controls, but this difference was eliminated by testing the alcoholics after a week delay. The smaller facilitation in performance shown by amnesics and by alcoholics tested after a delay was accompanied by impaired recognition memory as well as by qualitative differences in recognition performance. The Korsakoff patients tended to label same-name pictures as different while alcoholic controls tested immediately called them identical, a tendency which disappeared when alcoholics were tested after a delay. These findings suggest that Korsakoff patients are influenced by specific episodic information even more than are alcoholic controls.