Korsakoff amnesic syndrome: The result of simultaneous deficits in several independent processes?

Alcoholic Korsakoff patients were presented six verbal list learning tasks (two denotatively and three connotatively organized, and one high-imagery word list). Twelve recall trials and three recognition probes were obtained per list. Results indicate that for Korsakoff patients, (1) recall varied with list organization, (2) recognition memory although poor was further disrupted by proactive inhibition only on denotatively categorized lists, and (3) conceptual deficits disrupted ability to appreciate simple dichotomies in denotatively categorized lists. It is hypothesized that the joint presence of deficts in specific conceptual and semantic processes in necessary although perhaps not sufficient to produce a Korsakoff amnesia.     

The development of organized rehearsal

The purpose of this research was to evaluate the development or organization strategies in rehearsal processes. First-grade (age 7 years), third-grade (age 9 years), and fifth-grade (age 11 years) children were exposed to a memory task which involved multiple overt rehearsal and recall phases. The children were either free to rehearse any words from a taxonomically structured list or they were taught to rehearse in categories. The recall phase was either free or categorically cued. The number of repetitions in rehearsal increased only as a function of age. All of the independent variables facilitated the amount of organized rehearsal and the amount of retention. Children at all ages were able to maximize the relative amount of organized rehearsal when rehearsal was cued. The correlational analysis of the dependent variables indicated that for young children the quantity of rehearsal was linked to retention, but for older children the quality of rehearsal was related to retention. The results were interpreted as demonstrating the bases for production inefficiencies.     

Recall failure following successful generation and recognition of responses by alcoholic Korsakoff patients

Amnesic Korsakoff patients and controls were presented with twelve words, each shown individually in the presence of a weak associate. They were then asked to freely associate to 12 other words that were strong associates of the to-be-remembered (TBR) words. The Korsakoff patients generated, and were able to recognize, as many of the TBR words as the controls. Yet, in spite of this recognition ability, these same patients were subsequently unable to recall the critical TBR words when the weak cues were again presented. A follow-up study found that the same recognition results could be obtained with Korsakoffs months after initial presentation suggesting that the patients might initially have “recognized” the most highly associated words simply because they represented the most probable choices. Intermediate association prompts failed to generate correct responses. It was hypothesized that the Korsakoff patients cannot restructure their semantic associative hierarchy during input in such a way as to become sensitized to other than the strongest associates as prompts during recall.     

The effect of associations and expectations on lexical decision making in normals, alcoholics, and alcoholic Korsakoff patients

This study examined whether patients with Korsakoff's disease suffer from increased PI during encoding. The ability of the name of one category, e.g., BIRD, to prime the processing of members of another category, e.g., BODY PARTS, in a lexical decision task was used to assess the amount of PI during encoding. This task required a subject to inhibit the normal associations to BIRD. Young normals (25 years), older normals (48 years), alcoholics (45 years), and alcoholic Korsakoff patients (59 years) performed two lexical decision tasks. In the first experiment, the appearance of the neutral prime XXX 750 msec before the probe signaled that if the probe was a word, there was a 75% chance that it was from a particular category (e.g., BODY PARTS). The prime facilitated reaction time for words from the expected category for all four groups. The prime slowed reaction time for words that were not from the expected category for the young normals but did not influence reaction time for unexpected words for the three older groups. The second experiment was identical to the first except that a category word was used as the prime. The category word used as the prime was unrelated to the category of the words that were likely to follow it. For example, BIRD might be used to signal the likelihood that the word would be from the category, BODY PARTS. Again, young normals were slower to respond to unexpected probe words, but the three older groups were not. Again, the prime facilitated reaction time for expected words for the young normals, older normals, and alcoholics. However, the word prime did not facilitate reaction time for expected words for the alcoholic Korsakoff patients. That the word prime did not facilitate reaction time for the Korsakoff patients was viewed as evidence that they were unable to inhibit its normal associations and were more sensitive to PI from these associations than the other subjects.     

Cued recall in anterograde amnesia

After a single presentation of a word list, normal subjects exhibited better retention when prompted with semantic cues than with rhyme or letter cues. Alcoholic Korsakoff patients, patients receiving electroconvulsive therapy (ECT), and the patient N.A. exhibited impaired retention and, unlike control subjects, did not exhibit an advantage of semantic cues over letter and rhyme cues. Two experimental manipulations designed to equate the level of performance of amnesics and controls indicated that these amnesias could be understood as a reflection of weak memory strength that results from deficiencies in initial learning and retention. In addition, alcoholic Korsakoff patients appeared to have greater difficulty utilizing semantic cues than patients receiving ECT or patient N.A.     

Pictorial rehearsal

Subjects were presented with a sequence of picture-word items. The pictures were line drawings of common objects, and the words were the names of the objects. Half of the items were followed quickly by the next item, and the other half by a 15-sec “rehearsal interval.” The subjects were told to use these intervals to rehearse the item just presented, either by saying the word over and over to themselves or by maintaining the picture before the mind’s eye. There followed a test in which each item from the study list was cued with a fragment of either the picture or the name. Consistent with previous findings, identification was more probable for fragments of items that had been followed by a rehearsal interval. In addition, this advantage was found to be greater when the type of cue matched the mode of rehearsal that the subject had been instructed to adopt; there was in fact little, if any, advantage of rehearsal when cue and mode of rehearsal mismatched. This pattern of results suggests functionally distinct pictorial and verbal modes of rehearsal that serve not only to maintain information in conscious mind but also to build up memory proper.     

Encoding specificity in the alcoholic Korsakoff patient

A previous attempt to improve amnesic Korsakoff patients' retention of individual words resulted in only moderate improvement and, then, only under restricted conditions. It appeared that this occurred because the patients “forget” the instructed analysis of the word as well as the word itself. Consequently, the two experiments reported here sought to provide feature (Experiment 1) or associated (Experiment 2) cues at both input and output. In this manner relatively good performance was obtained, but only when semantic cues were “strongly” associated to the target words. Implications for an encoding specificity interpretation are drawn from these results.     

Verbal retention deficits in aphasic and amnesic patients.

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.     

Recall of short word lists presented visually at fast rates: Effects of phonological similarity and word length

Phonological similarity of visually presented list items impairs short-term serial recall. Lists of long words are also recalled less accurately than are lists of short words. These results have been attributed to phonological recoding and rehearsal. If subjects articulate irrelevant words during list presentation, both phonological similarity and word length effects are abolished. Experiments 1 and 2 examined effects of phonological similarity and recall instructions on recall of lists shown at fast rates (from one item per 0.114-0.50 sec), which might not permit phonological encoding and rehearsal. In Experiment 3, recall instructions and word length were manipulated using fast presentation rates. Both phonological similarity and word length effects were observed, and they were not dependent on recall instructions. Experiments 4 and 5 investigated the effects of irrelevant concurrent articulation on lists shown at fast rates. Both phonological similarity and word length effects were removed by concurrent articulation, as they were with slow presentation rates.     

Effects of encoding instructions and retrieval cuing on recall in Korsakoff patients

The relationship between the depth of encoding a word and its subsequent recall, either cued or noncued, was investigated in this study. In Experiment 1, Korsakoff subjects and alcoholic controls were shown a categorized word list under one of three different encoding instructions: (1) nonsemantic, that is, detecting the presence or absence of the letter “e” in each word, (2)semantic, that is, assigning words to their correct taxonomic category, and (3) no encoding instructions. Semantic encoding instructions resulted in higher recall for both diagnostic groups than the other instructions. In Experiment 2, subjects were again assigned to one of the three encoding instructions as in Experiment 1, but all groups received cues (category labels) at the time of recall. Cuing increased recall for all but the group receiving instructions to encode nonsemantically. Experiment 3 was a replication of the previous experiments. The results indicated that Korsakoff subjects were capable of encoding semantically without specific instructions to do so but were impaired in the ability to generate retrieval cues at the time of recall.     

Is spoken duration a sufficient explanation of the word length effect?

The word length effect is one of the cornerstones of trace decay plus rehearsal models (TDR) of memory. Words of long spoken duration take longer to rehearse than words of short spoken duration and as such suffer more decay and are thus less well recalled. The current experiment manipulates both syllable length and spoken duration within words of fixed syllable length in an aim to test the assumptions of the TDR model. Our procedures produced robust effects of both syllable length and spoken duration in four measures of the time it takes to pronounce the different types of words. Serial recall for the same materials produced robust syllable effects, but no duration effects.     

Is spoken duration a sufficient explanation of the word length effect?

The word length effect is one of the cornerstones of trace decay plus rehearsal models (TDR) of memory. Words of long spoken duration take longer to rehearse than words of short spoken duration and as such suffer more decay and are thus less well recalled. The current experiment manipulates both syllable length and spoken duration within words of fixed syllable length in an aim to test the assumptions of the TDR model. Our procedures produced robust effects of both syllable length and spoken duration in four measures of the time it takes to pronounce the different types of words. Serial recall for the same materials produced robust syllable effects, but no duration effects.     

工作记忆中汉语反词长效应机制

工作记忆中的反词长效应(reverse word-length effect)指在对长词和短词混合的词表进行即时序列回忆时, 独立长词回忆成绩优于独立短词的现象。以汉字词语为材料通过3个实验探讨反词长效应的机制。实验1采用纯粹词表和长短词混合词表, 既得到纯粹词词长效应, 也得到独立词反词长效应。实验2削弱了长短词之间的词长差异, 结果独立词反词长效应消失, 且独立词回忆成绩优于纯粹词。实验3设计了视觉延迟条件, 得到与实验1类似的结果, 只是独立词反词长效应有所削弱。三个实验的结果并不一致, 无法用现有的语音回路理论或SIMPLE理论进行很好地解释, 理论的整合与创新显得非常重要。因此, 提出多重编码以既相互竞争又相互补充方式进行平行加工的观点进行更完整地解释。     

Item identification time and rehearsal rate as predictors of memory span in children

According to the working memory model of Baddeley and Hitch (1974), the sensitivity of memory span to word length arises from the time taken to rehearse items in a speech-based “articulatory loop”. Alternatively, it has been suggested that the word-length effect may result from differences in the speed of perceptual processes of item identification. Changes in the speed of rehearsal and of item identification have also been claimed to contribute to the growth of memory span that is seen in development. In order to compare these two variables directly, groups of children aged 8 and 11 were assessed on memory span for words of one, two, and three syllables; span under articulatory suppression; rehearsal rate; and item identification time. Span was found to be a linear function of rehearsal rate across differences in both word length and age. The word-length effect was unrelated to item identification time and was diminished by articulatory suppression. These results show that the word-length effect reflects rehearsal and not item identification processes. However, the results also suggest that changes in item identification time contribute to developmental differences in span when articulation is suppressed. A distinction between item identification and rehearsal effects can be readily interpreted in terms of the working memory model if it is assumed that they indicate the efficiency of different subsystems involved in span.     

Some analyses of the verbal encoding deficit of alcoholic Korsakoff patients

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 subject's 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 Posner's reaction time technique which assesses a subject's 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.     

Effects of talker variability on recall of spoken word lists

Three experiments were conducted to investigate recall of lists of words containing items spoken by either a single talker or by different talkers. In each experiment, recall of early list items was better for lists spoken by a single talker than for lists of the same words spoken by different talkers. The use of a memory preload procedure demonstrated that recall of visually presented preload digits was superior when the words in a subsequent list were spoken by a single talker than by different talkers. In addition, a retroactive interference task demonstrated that the effects of talker variability on the recall of early list items were not due to use of talker-specific acoustic cues in working memory at the time of recall. Taken together, the results suggest that word lists produced by different talkers require more processing resources in working memory than do lists produced by a single talker. The findings are discussed in terms of the role that active rehearsal plays in the transfer of spoken items into long-term memory and the factors that may affect the efficiency of rehearsal.     

Is perceptual salience needed in explanations of the isolation effect?

The isolation effect is a well-known phenomenon that has a well-accepted explanation: An item that is isolated on a list becomes perceptually salient, which leads to extra rehearsal that enhances memory for the isolate. To evaluate this hypothesis, the authors isolated an item near the beginning of a list. Immediately after each item was presented for study, participants judged the likelihood of recalling the item. Although the isolation effect occurred, participants did not judge the isolate as being more memorable than the preceding item, suggesting that the isolate was not salient. In a second experiment, participants rehearsed items aloud. Isolation at the beginning of the list did not produce extra rehearsal. By contrast, isolation in the middle of the list produced extra rehearsal; however, even when the isolate did not receive extra rehearsal, an isolation effect was evident. Thus, salience and extra rehearsal are not necessary for producing an isolation effect.     

Depth of processing and retention of words by alcoholic Korsakoff patients

The relationship between the depth to which a word is initially processed and its eventual probability of being recognized was investigated with amnesic (alcoholic Korsakoff) patients. Several variations of Craik and Tulving's paradigm designed to asses this relationship were used. basically, this procedure insures analysis of particular features of a word by the nature of the question the subject must answer about the word during its initial presentation. Decision-time measures demonstrated that Korsakoff patients could answer the query nearly as rapidly as normals, but the patients failed to demonstrate a normal increase in recognition as a function of the depth of analysis demanded by the query (Experiments 1--2). However, when the test procedure was extremely simplified (Experiment 3) by presenting only a small number of to-be-recognized words, the Korsakoff patients did demonstrate the normal "pattern" of recognition. It was concluded that under the appropriate circumstances, Korsakoff patients' recognition memory can be improved by instructions to analyze the more sophisticated (semantic) features of verbal information.     

Developmental changes in the lag effect: An encoding hypothesis for repeated word recall

A differential encoding hypothesis for the lag effect in free recall was tested developmentally. Fourth- and eighth-grade children and college adults were shown a list of words, with some repeated at various lag intervals. Lag functions in repeated word recall were found to vary with age. An encoding hypothesis, modified to provide specificity for the time at which differential encoding takes place, was used to account for the results. Finally, it was suggested that the lag paradigm could be utilized to assess developmental differences in processing strategies, as perhaps a more sensitive, and general, alternative to the overt rehearsal technique.     

Reconstructive retrieval deficits in Broca's aphasia

Anterior aphasic patients' ability to utilize the phonemic and/or semantic features of verbal material for retention purposes was investigated. In the first experiment, patients were asked to either detect word repetitions, phoneme repetitions, or rhymes in a list of items. The aphasics performed well on word and phoneme repetition detection but below both normals and amnesic Korsakoffs on rhyme detection. In the second experiment the patients were instructed to analyze either the physical, phonemic, or semantic features of words they were later asked to recognize. Aphasics were differentially affected (as were normals) by these instructions: semantic feature analysis resulted in the best performance, followed by phonemic feature analysis. It was concluded that anterior aphasics can analyze, recirculate, and even store the phonemic features of words, but find difficulty in reconstructing the originally presented item from these features.