New learning and remote memory in the same and different domains of experience: implications for normal memory and amnesia.

This study investigated the correlation between new and remote memory ability in normal young subjects and evaluated whether using tests that tapped different domains of experience had any effect on the relationship between new and remote memory. Remote memory was assessed using a famous face test and new memory was evaluated using both novel faces and words. The main finding was a significant correlation between New and Remote face familiarity scores. A correlation was obtained when both tests tapped the same domain of memory, whereas when tests tapped different domains, there was no Remote-New correlation. Remote-New correlations may only exist between tests tapping the same domain of memory. This has implications for the interpretation of previous amnesic literature and for future investigations.

Mutual inhibition in collaborative recall: evidence for a retrieval-based account.

In Experiment 1 participants gave 3 successive free recalls of items learned either individually or in pairwise collaboration. The first and third recalls were performed individually, the second alone or in collaboration. Collaborative recall led to an inhibitory effect after individual learning but not after collaborative learning, in which partners had similar retrieval strategies. Consistent with a retrieval locus for collaborative inhibition, non-recalled items reappeared in subsequent individual recall. Experiment 2 showed that collaborative inhibition was eliminated when a separate retrieval cue was given for each item. Experiments 2 and 3 also showed that when participants learned items in the same order, their retrieval strategies were more similar and they showed less collaborative inhibition. It is concluded that mutual interference in collaborative recall is due to the mutual disruption of individual retrieval strategies.

Shattered illusions: the effect of explicit memory mediation on an indirect memory test.

Four experiments were conducted to explore the possible involvement of explicit memory in an indirect memory test in which white noise accompanying old sentences was judged to be quieter than white noise accompanying new sentences (Jacoby, Allan, Collins & Larwill, 1988). Experiment 1 established that this effect lasted up to 1 week. Experiment 2 found that a group of amnesic patients showed a noise effect that was marginally above chance and not significantly less that that of their matched controls after a delay of one day. Effect of time pressure at test (Experiment 3) and divided attention at study (Experiment 4) suggested that the memory processes mediating the noise effect were not automatic, although the possibility that the processes involve enhanced fluency is also discussed.

Do novel associative word stem completion and cued recall share the same memory retrieval processes?

The aim of this study was to determine whether word stem completion for novel associations between cue and target words was mediated by automatic unconscious memory processes or effortful memory processes under conscious control. This was done by applying full and divided attention conditions at test to stem completion, cued recall, and recognition, and by administering a questionnaire that probed the memory strategies used by subjects during the completion test. Divided attention had no effect on stem completion performance, but did reduce associative cued recall. Recognition performance was weakened overall by divided attention, but the associative effect was similar under both attention conditions. This suggested that novel associative word stem completion was mediated by automatic retrieval processes. However, the results of the questionnaire indicated that only subjects who attempted to remember the words from the study phase during the completion task showed any novel associative effect. It is concluded that novel association word stem completion and cued recall share automatic retrieval processes, which nevertheless give rise to the experience of remembering.

Simulating a memory impairment: can amnesics implicitly outperform simulators?

OBJECTIVES: The purpose of this study was to examine the effectiveness of a variety of tests in differentiating simulating test performances from genuine memory-impaired and normal (control) test performances. DESIGN: A simulation design was implemented, based on an analogue design in which normal participants were given experimental instructions to feign a mental impairment and are compared to (a) other normal participants with instructions to perform honestly, and (b) a comparison group, for example, acquired brain-injured persons, with similar instructions. METHOD: Forty individuals comprised the simulating and control group and all participants were randomly assigned to the simulating and control groups. Twenty memory-impaired patients, all of whom had been diagnosed as suffering from a memory impairment following acquired brain damage, participated as the memory-impaired control group. The simulation group was directed to imitate a person with a memory impairment. The primary outcome measure involved identifying those tests, if any, where simulators were significantly different from normal and memory-impaired participants. RESULTS: On 5 of the 15 tasks administered, simulators performed significantly differently from normal and memory-impaired participants. Of these 5 tasks, the coin-in-the-hand, when administered in conjunction with the autobiographical interview, identified 95 per cent of the simulators without misclassifying any of the memory-impaired or normal participants. CONCLUSION: It is suggested that these two tests, when administered jointly, might be of use in clinical settings to assist in the detection of malingerers.

Autonomic and recognition indices of memory in amnesic and healthy control subjects.

Autonomic and recognition indices were examined in six amnesic subjects of mixed aetiology and six control subjects matched with respect to age, education and intelligence. The key objectives of this study were: (a) assess amnesics level of recognition and autonomic discrimination for recently shown words compared with controls; (b) determine if amnesics' level of autonomic discrimination was preserved when compared with the control subjects, level of recognition; and (c) assess confidence in hits and false alarms. The results showed that: (1) despite showing impaired recognition, amnesics displayed significantly better autonomic discrimination; (2) the level of autonomic discrimination displayed by amnesics did not significantly differ from the control subjects' level of recognition; (3) the level of confidence expressed in false alarms and hits did not significantly differ between amnesics and controls, which is in sharp contrast to the significantly greater levels of confidence expressed by healthy subjects in hits versus false alarms. If future work shows that amnesics display preserved autonomic discrimination for novel information, then it may suggest that, at least, some amnesics can store information to an extent that is comparable to that of healthy controls.

Collaboration in recall: do pairs of people cross-cue each other to produce new memories?

When people collaborate over their recall of a shared experience, it might be expected that they could "cross-cue" each other so as to produce new memories not available to either member of the pair on their own. In a previous series of experiments (Meudell et al., 1992), we found that pairs of people always recalled more than one person, but we failed to show that social interaction facilitated performance so as to produce such "emergent" new memories. However, a phenomenon akin to cross-cuing was employed by Tulving and Pearlstone (1966) in their classic study of the availability and accessibility of memories; accordingly, in this study, we repeated Tulving and Pearlstone's work directly in a social context. So as to assess whether new memories emerged in collaborating pairs, a sequential design was employed. People learned categorized lists of words, and then all the subjects recalled the items strictly on their own. Subjects then recalled again in pairs (collaboratively) or once more on their own. The results showed that even when the opportunity for cross-cuing was directly manipulated through the provision of categorized lists, no additional new memories emerged in the collaborating groups. Possible mechanisms for the results are considered.

Long lasting indirect memory performance for abstract shapes in amnesics and matched controls.

The speed with which subjects copied complex geometrical shapes was used as an indirect memory measure in a group of 12 organic amnesics of several aetiologies and their matched controls, tested at two delays. Both subject groups were found to copy previous seen shapes faster than new foil shapes, and the magnitude of the speed up effect did not differ significantly between amnesics and matched controls when tested at two delays of 10 min and 24 hr, respectively. The size of the indirect memory effect did not decline across the delay in either group. In contrast to indirect memory performance, measured by two-choice recognition of the shapes, was impaired in the amnesic group and there was some suggestion that recognition performance declined across the delay in both subject groups.

Two tests for assessing remote public knowledge: a tool for assessing retrograde amnesia.

Guidelines for the construction and development of tests of remote memory are provided. These guidelines follow from methodological considerations and from certain theoretical issues we believe that remote memory tests should address if they are to further our understanding of amnesia. These include: the pattern of temporal gradient; memory for different broad classes of information such as famous names and famous events; and recall and recognition of different types of detail such as contextual and non-contextual information associated with remote memory. With respect to the first of these, we argue that it is impossible to fully evaluate competing hypotheses about temporally graded retrograde amnesia unless items are selected from at least two difficulty levels, and from at least two time periods. The construction of two equivalent tests of remote memory, one for famous people, the other for famous events, is described, and the theoretical issues listed earlier were addressed using these tests in a study comparing the remote memory of 13 organic amnesics and 13 age- and IQ-matched controls. The principal findings were as follows. There was only weak evidence that amnesics' remote memory for famous people and events was temporally graded over a 20 year period, and recognition memory and memory for non-contextual detail were equally impaired. Mayes, Meudell, and Pickering's (1985) context memory deficit hypothesis was supported, however, because amnesics were more impaired in their ability to date recognised items. In addition, although there was little support for a temporally graded retrograde impairment on the recognition question, there was much clearer evidence for the temporal dating question. Also, one patient, SR, showed a selective deficit in dating recognised names and events from the 1980s. Finally, the correlations between measures of anterograde and retrograde amnesia were all non-significant. Suitable items for the construction of remote memory tests probing the four decades 1950s to 1980s are presented. A subset of these, from the 1970s and 1980s, were shown to have satisfactory psychometric qualities, and can therefore be recommended for more widespread clinical use, although more extensive normative data than that provided here will be necessary.

Dual task performance in amnesic and normal people: does resource depletion cause amnesia?

Normal peoples' memory can be seriously disrupted if their cognitive resources are depleted by means of an experimental manipulation (such as distraction at encoding or at retrieval). By analogy, it has also been suggested that amnesia might result directly from pathological loss of cognitive capacity. This hypothesis was examined in 12 mixed amnesics and 12 normal people by means of a 'dual task' study. It was argued that if amnesics have reduced cognitive resources they should be disproportionately impaired in dual task performance relative to single task performance and in comparison to controls. This result was unambiguously demonstrated using a visual (letter detection) task combined with an auditory (semantic decision) task. However, correlations with measures of frontal function and with indicants of severity of amnesia proved insignificant and so the role of resource depletion in amnesia remains, as yet, unproven.

Preserved pattern completion priming for novel, abstract geometric shapes in amnesics of several aetiologies.

Two experiments were conducted using a paradigm developed by Gabrieli et al., Neuropsychologia 28, 417-427, 1990, which assessed both indirect and direct memory performance in a completion task for novel abstract geometric patterns. The preferred method of scoring was the lines method, based on the number of correct and incorrect lines produced for each item. It was chosen because it is both the simplest and the most informative measure. Two methods of scoring were used in previous work, namely, the strict whole figure method and the lenient whole figure method (Gabrielli et al., 1990; Verfaelie et al., Brain Cognit. 18, 34-45, 1992). Therefore to facilitate comparisons between studies and to determine the characteristics of different scoring methods, results with all three measures were included. In Experiment 1, two different encoding strategies of naming and copying were used in order to explore the relationship between indirect and direct memory performance. Indirect memory performance in the naming condition was at baseline whereas in the copying condition it was significantly above baseline. Cued recall did not differ across encoding conditions but recognition was higher in the naming condition than the copying condition. In Experiment 2, an attempt was made to extend the findings of two studies, one with H.M. (Gabrielli et al., 1990) and one with nine Korsakoffs (Verfaelie et al., 1992), to a larger group of 14 amnesics of several aetiologies. Indirect memory performance was found to be equivalent for the amnesics and their matched controls, only when the lenient and the lines methods of scoring were used. Recognition and cued recall performance was impaired for the amnesics compared to the controls.

Short report: is spatial information encoded automatically in memory?

A dual-task paradigm was used to test Hasher and Zacks' (1979) hypothesis that spatial memory is automatic. Subjects saw two sets of 16 words each, the words being presented singly in random corners of a monitor screen. They were asked to remember the words and the corner in which each word was shown. In addition, subjects were given a concurrent task to perform. This task was either "easy" (counting aloud by ones) or "difficult" (counting aloud by sevens). Attention was focused either on the memory task or on the counting task. Word recognition was better when subjects carried out the easier competing counting task and when subjects concentrated mainly upon remembering the words and their positions. Contingent spatial memory was unaffected by either manipulation, supporting the hypothesis that spatial memory is automatic.

Amnesics have a disproportionately severe memory deficit for interactive context.

Two experiments were used to compare the recognition memory of amnesic and normal subjects for intentionally encoded words (targets) and for incidentally encoded words that were meaningfully related to the targets and presented at the same time (interactive context). In both experiments the target recognition of the two groups was matched at a high level by presenting the amnesics with much shorter lists of words to remember. Experiment 1 compared 20 amnesics and their matched controls and showed that whereas the amnesics' recognition of the target words did not benefit significantly when they were presented together with their interactive context words (relative to their recognition when the target words were presented alone), that of the controls did. Experiment 2 compared 14 amnesics and their matched controls and showed that when patients and their controls were matched on their target word recognition in isolation, then the patients still showed worse recognition for the interactive context words. These effects were not found only in Korsakoff patients, and their size did not correlate with behavioural measures of frontal-lobe damage. It is concluded that amnesics may be more impaired at recognizing incidentally encoded interactive context than they are at recognizing target material, and this deficit may be an essential feature of the syndrome.

Priming of face matching in amnesia.

Priming was studied in a task that required a speeded response to photographs of faces. On each trial, subjects viewed two faces and decided if the same person was shown twice or if two different people were shown. Both familiar and unfamiliar (i.e., well-known and unknown) faces were used, and some face pairs were repeated with a mean delay of about 10 min. Repetition was associated with faster reaction times in young subjects (Experiment 1) as well as in amnesic patients and age-matched control subjects (Experiment 2). The patients' reaction times were slower overall, although the magnitude of the priming effect did not differ from that in the control subjects. This preservation of a normal reaction-time facilitation in subjects with impaired recognition memory for faces occurred for both familiar and unfamiliar faces, suggesting that amnesia does not necessarily interfere with the acquisition of new information as indexed by this priming effect.

Irrelevant, incidental and core features in the retrograde amnesia associated with Korsakoff's psychosis: a review.

A brief review of the literature on retrograde amnesia in Korsakoff's syndrome is presented. Various explanations of the phenomenon are discussed including the notions that it results from the effects of "state-dependency", that it occurs as a result of a progressive learning problem and that it arises through a failure in contextual processing. None of these hypotheses can satisfactorily account for the length and temporal gradient of alcoholic amnesics retrograde amnesia. Although some evidence points towards the hypothesis that anterograde and retrograde amnesia might result from separate and independent impairments, this view is presently unproven and leaves open what causes the form and duration of Korsakoffs retrograde amnesia.

Korsakoff amnesics are poor at judging the sequence of two tones.

Alcoholic amnesics were given a test of temporal sequencing ability devised by Efron which has practically no memory component. These amnesics were very impaired on the task. However, the extent of this impairment did not relate to the magnitude of their "target memory" deficit nor did it relate to the ability to make temporal judgements from memory. Two other groups of amnesics (3 post-encephalitis and 4 with ruptured aneurysms of the anterior communicating artery) did not show impairments on the sequencing task. Data from the amnesic patient N.A. (who was unimpaired on the task), three other amnesics (who showed a tendency to be poor at the task) and two frontally damaged patients (one of whom performed especially badly on the sequencing task but had no obvious memory difficulties) were also presented. It is argued that deficits in temporal discrimination may not be found in all amnesics but, when they are observed, are an incidental feature related to additional (possibly cortical damage. Implications of the results for the view that amnesia results from a deficit in the use of contextual information (including temporal information) are considered.

Disproportionate intentional spatial-memory impairments in amnesia.

Twenty-four amnesics, including patients with Korsakoff's disease, post-encephalitic amnesia and amnesia caused by rupture of an anterior communicating artery aneurysm (ACoAA), were compared with 24 matched control subjects on a task in which words were presented in any one of four positions on a computer screen and subjects were instructed to remember both the words and their locations. The patients were tested after more learning opportunity, exposure to shorter lists, and after shorter delays than were their controls in order to match the word recognition performance of the two groups. Under these conditions, the amnesics' ability to locate recognized words was significantly worse than that of their controls. Although there was a tendency for the ACoAA patients to show more severe spatial memory deficits than Korsakoff patients, there was no clear evidence that aetiology of amnesia was a critical determinant of whether spatial memory was more impaired than word recognition. It was concluded that amnesics show a disproportionately severe memory deficit for spatial information that is intentionally encoded as well as for that which is incidentally encoded.

Indirect measures of memory in a duration-judgement task are normal in amnesic patients.

Nine amnesic patients of mixed aetiology were studied in a duration-judgement task that allowed three measures of memory to be obtained. On each trial of the task, subjects attempted to read a briefly flashed word and to estimate the duration of the flash. Both word identification and duration estimation differed as a function of prior study. Words that were previously studied were identified more often and were estimated to have been flashed for a longer duration than were words not previously studied. These priming effects were found in young subjects in Experiment 1 and in amnesic patients and age-matched control subjects in Experiment 2. Priming effects were normal in the amnesic patients, whereas these patients were severely impaired at recognizing the same words. Previous results have also shown that amnesic patients can perform normally on certain memory tests, including priming of word identification. These results show that priming of duration judgements can also be included in the category of indirect measures of memory that are spared in amnesia.

Performance on tests sensitive to frontal lobe lesions by patients with organic amnesia: Leng & Parkin revisited.

Groups of amnesics with aetiologies that included chronic alcoholism, encephalitis and ruptured anterior communicating artery aneurysm (ACoAA) were examined on the Cognitive Estimation Test (CET), FAS Word Fluency Test (FAS) and the full and Nelson (1976) versions of the Wisconsin Card Sorting Test (WCST). The alcoholic amnesics were impaired on all four tests, whereas the post-encephalitic amnesics were impaired on the FAS and CET but performed normally on both versions of the WCST. The ACoAA amnesics were impaired on both the FAS and the CET, and scored at a level in between the other amnesic subgroups on the WCST.

Why are amnesic judgements of recency and frequency made in a qualitatively different way from those of normal people?

The Huppert and Piercy (1978) test of recency and frequency judgements was given to a group of 12 non-Korsakoff amnesics of mixed aetiology and to four non-amnesic patients with selective frontal lobe lesions. The results confirmed that non-Korsakoff amnesics show a significant tendency to base their recency and frequency judgements on memory strength and that amnesics with medial temporal lobe damage show this tendency at least with recency judgements. The patients with frontal lobe lesions performed like normal subjects. Patients who were dysexecutive or impaired in cognitive resources were less likely to base recency judgements on trace strength. Such a recency bias was not however, correlated with measures of amnesic severity. The tendency to base frequency judgements on memory strength was not related to either degree of amnesia or reduction of cognitive resources.