Data-driven recognition memory: a new technique and some data on age differences

In this study, we investigate the effect on recognition memory of having target and distractor stimuli consisting of different combinations of low-level elements (letters), relative to when targets and distractors consist of combinations of the same elements (nonoverlap and overlap conditions, respectively). It was found that recognition memory was enhanced in the nonoverlap condition, even though subjects reported being unaware of this experimental manipulation. This confirms the importance of perceptually driven processing in the implicit memory component of recognition memory. The extent to which this effect occurs is found to be age dependent, with elderly subjects benefiting more from having targets and distractors consisting of nonoverlapping elements. This is consistent with the notion that elderly subjects show less reliance on item-specific/contextual detail to support recognition memory.

Source monitoring and false memories in children: relation to certainty and executive functioning

We presented children aged 6, 8, and 10 years with a video and then an audio tape about a dog named Mick. Some information was repeated in the two sources and some was unique to one source. We examined: (a) children's hit rate for remembering whether events occurred and their tendency to make false alarms, (b) their memory for the context in which events occurred (source monitoring), (c) their certainty about hits, false alarms, and source, and (d) whether working memory and inhibition were related to hits, false alarms, and source monitoring. The certainty ratings revealed deficits in children's understanding of when they had erred on source questions and of when they had made false alarms. In addition, inhibitory ability accounted for unique variance in the ability to avoid false alarms and in some kinds of source monitoring but not hits. In contrast, working memory tended to correlate with all forms of memory including hits.

The role of semantics in reading and spelling: evidence for the 'summation hypothesis'

This study documents a patient, SA, with an impairment of semantic memory arising as a result of Semantic Dementia (Pick's disease). The patient is impaired at deriving semantic knowledge from both words and pictures. However, his ability to derive semantic knowledge of countries is relatively spared compared to concrete nouns and famous people. The presence of a semantic deficit was used to investigate the role of semantics in reading and spelling. Several novel cueing/priming paradigms are reported which suggest that SA is able to use partial semantic knowledge to constrain his reading and spelling. These results are broadly consistent with the 'summation hypothesis' [27] and suggest that normal reading and spelling may take place by integrating both semantic information and knowledge of direct orthography-phonology correspondences.

British memory research: a journey through the 20th century

A century of research in memory has generated a wealth of knowledge encompassing theoretical developments within a number of distinct domains of memory. The aim of this article is to explore the progress made in memory research during the 20th century, to indicate critical influences on the direction of research, and to illustrate the important contribution made by British researchers. This article is confined to human memory research, and reviews research findings from the various psychological disciplines studied over the past 100 years.

Reversed negative priming following frontal lobe lesions

The present study investigated whether lesions to the prefrontal cortex would lead to impaired inhibitory control in selective attention. Patients with uni- and bilateral frontal lobe damage and age-matched control participants were compared in an identity negative priming task involving letter naming. Whereas all control groups revealed robust negative priming and distractor interference, the majority of patients showed positive instead of negative priming and not all of them were more susceptible to interference. These results suggest that frontal lobe lesions disrupt distractor inhibition and cannot be explained in terms of a retrieval deficit. However, the level of interference may not only be determined by inhibition but also by excitation of the target stimulus.

Levels of processing and single word priming in amnesic and control subjects

This paper describes an experiment which examined how levels of processing (LOP) affected word fragment completion in a group of Wernicke-Korsakoff patients, a group of patients with closed head injury, and matched controls. The data showed that both the memory-impaired groups and the controls showed a LOP effect but that the effect was larger in controls. Data from other studies are reviewed and, in conjunction with the present findings, it is concluded that LOP effects obtained when memory-impaired individuals are tested using implicit memory tasks arise mainly from the contribution of lexical processing of targets and from contamination by explicit recollection.

The central executive does not exist

In this article I critically review the concept of the central executive. I argue that the experimental evidence for a central executive lacks rigor to the point where it is an unfalsifiable construct. I examine the neuropsychological and neuroradiological evidence and demonstrate that there is no localization evidence for a central executive. What emerges instead is a pattern of extensive heterogeneity with different executive tasks associated with different neural substrates. In sum it is argued that the idea of a central executive should be abandoned, and, from a neuropsychological perspective, tests that purport to measure executive function should do so in a qualitative way rather than assume that a range of tests load on a unitary dimension of performance.

Consequences of violating the assumption of independence in the process dissociation procedure: a word fragment completion study

In three experiments that used levels of processing and study time manipulations as independent variables in a word fragment completion task, the validity of the assumption of independence between recollection and automatic influences of memory was assessed. This assumption underlies the use of the process dissociation procedure (Jacoby, 1991), a tool suggested for distinguishing the different contributions of recollection and automatic influences of memory. Overall, it appeared that semantic processing, as compared with physical processing at study, positively affected recollection but negatively affected automatic influences of memory in word fragment completion. This negative effect on the automatic influences was reduced when the available study time decreased. The incompatibility of these results with the assumption of independence between recollection and automatic influences of memory and their impact on the applicability of the process dissociation procedure are discussed.

Revising current two-process accounts of spacing effects in memory

Memory for repeated items improves when presentations are spaced during study. In Experiment 1A, words were repeated either immediately or after 6 intervening items. Intentional learning occurred under either focused or divided attention. Retention was tested by either free recall or yes-no recognition. Divided attention did not affect the influence of spacing in free recall, whereas it removed the spacing effect in recognition. In Experiment 1B, recognition memory was tested after incidental semantic study of words performed under either focused or divided attention. An equivalent spacing effect occurred in both attentional conditions. In Experiments 2 and 3, recognition memory for unfamiliar faces was assessed. A reliable spacing effect was found under both intentional learning and incidental structural study. These data are, collectively, incompatible with current theories of spacing effects. A theoretical proposal to account for these new findings is outlined.

Revising current two-process accounts of spacing effects in memory

Memory for repeated items improves when presentations are spaced during study. In Experiment 1A, words were repeated either immediately or after 6 intervening items. Intentional learning occurred under either focused or divided attention. Retention was tested by either free recall or yes-no recognition. Divided attention did not affect the influence of spacing in free recall, whereas it removed the spacing effect in recognition. In Experiment 1B, recognition memory was tested after incidental semantic study of words performed under either focused or divided attention. An equivalent spacing effect occurred in both attentional conditions. In Experiments 2 and 3, recognition memory for unfamiliar faces was assessed. A reliable spacing effect was found under both intentional learning and incidental structural study. These data are, collectively, incompatible with current theories of spacing effects. A theoretical proposal to account for these new findings is outlined.

Are the benefits of errorless learning dependent on implicit memory?

The effectiveness of errorless and errorful learning methods was compared in two experiments in which a group of memory-impaired individuals learned lists of single words. In both experiments, error prevention during learning resulted in higher levels of cued recall performance than trial-and-error learning. Experiment 1 showed that the beneficial effects of the errorless learning method extended over a delay of up to 48 hr and were also observed in free recall. The hypothesis that the benefits of errorless learning rely upon implicit memory was tested in Experiment 2. No evidence was found to support the hypothesis. Implicit memory was observed following both errorless and errorful learning, but there was no indication that enhanced performance in the errorless condition could be accounted for by implicit memory. There was no correlation between performance on a direct test (cued recall) and performance on an indirect test (fragment completion) for the same materials. Furthermore, the extent of priming was no greater for recalled items than non-recalled items in the cued recall test. It is proposed that the benefits of errorless learning in this paradigm stem from the effects of error prevention on residual explicit memory.

Human memory: novelty, association and the brain

The hippocampus has been clearly implicated in memory, but its precise role is unclear. Recent imaging studies suggest that the hippocampus is particularly concerned with the detection of novelty, as opposed to the prefrontal cortex, which seems more concerned with encoding associations.

Errorless learning of novel associations in amnesia

In two experiments involving verbal association learning by people with memory impairments, the effectiveness of errorless learning (EL) was compared with errorful learning (EF). Experiment 1 examined the effectiveness of both methods in learning remotely linked word pairs. There was an advantage for items learned by EL at immediate test which was not sustained over a delay of 1 hr. Learning appeared to be stable over this delay in the EF condition. Analysis of responses at delayed cued recall showed more evidence of spontaneous recovery in EF than in EL. Elimination of these items from analysis resulted in a similar pattern of forgetting in both methods. Experiment 2 examined the effectiveness of EL and EF in teaching novel associations, and showed an advantage for EL at immediate and delayed test. Forgetting was apparently observed following EL, but not EF. As in Experiment 1, this discrepancy was attributed to recovered responses at delayed test in EF. Eliminating these responses showed a similar pattern of forgetting in both methods for items correctly recalled at immediate test. The study shows an advantage for EL techniques in learning novel associations. The two methods also differ in that learning via EF is associated with more spontaneous recovery.

Human memory: the hippocampus is the key

A recent study of brain-damaged patients with various degrees of amnesia provides compelling new evidence that the hippocampus plays a vital role in the laying down of new memories. Why existing memories are also affected by hippocampal damage is particularly puzzling.

Things that go bump in your life: explaining the reminiscence bump in autobiographical memory

Two experiments explore the reminiscence bump (RB)--the disproportionately higher recall of early-life memories--by older adults. In Experiment 1, participants in the age ranges of 36-40, 46-50, and 56-60 recalled events freely or under instructions to avoid recent memories. Constraint did not affect older participants but resulted in the appearance of an RB in younger participants. In Experiment 2, recall was constrained to particular life periods. Memories from these periods were compared for ease of retrieval and along subjective dimensions (e.g. vividness). Memories from early life were more easily retrieved, but this was not due to differences in subjective qualities. A higher proportion of memories for first-time events were identified from early life, and these memories were more easily retrievable. The results are discussed in relation to an existing model of autobiographical memory, and a revised model is put forward.

Pathological false alarm rates following damage to the left frontal cortex

In this study we present further data on case JB who developed memory impairment following a ruptured aneurysm of the anterior communicating artery which resulted in damage centered on the frontal cortex. The data reveal the JB's memory impairment is characterized by a recall impairment in which intrusion rates are abnormally high and a recognition deficit characterized by an exceptionally high false alarm rates. A comparison is made between this case and other recent cases involving impairments with a similar etiology. Theoretical interpretations of JB's deficit are also considered.

Things that go bump in your life: explaining the reminiscence bump in autobiographical memory

Two experiments explore the reminiscence bump (RB)--the disproportionately higher recall of early-life memories--by older adults. In Experiment 1, participants in the age ranges of 36-40, 46-50, and 56-60 recalled events freely or under instructions to avoid recent memories. Constraint did not affect older participants but resulted in the appearance of an RB in younger participants. In Experiment 2, recall was constrained to particular life periods. Memories from these periods were compared for ease of retrieval and along subjective dimensions (e.g. vividness). Memories from early life were more easily retrieved, but this was not due to differences in subjective qualities. A higher proportion of memories for first-time events were identified from early life, and these memories were more easily retrievable. The results are discussed in relation to an existing model of autobiographical memory, and a revised model is put forward.

Focal retrograde amnesia: a multi-faceted disorder?

In this paper I review the recently introduced syndrome of focal retrograde amnesia-a disproportionate impairment of remote memory in the presence of normal or near normal anterograde memory. It is concluded that the modal form of the syndrome has been reliably demonstrated and that the underlying pathology involves damage to the temporal lobes and relative sparing of the hippocampal formation. A variant of the syndrome associated with parietal and occipital lobe damage is also presented. Finally, a third type of focal retrograde amnesia associated with minor brain trauma is considered to be or primarily psychogenic origin.

Functional aspects of recollective experience in face recognition

This article describes two experiments on awareness in recognition memory for novel faces. Two kinds of awareness, recollective experience and feelings of familiarity in the absence of recollective experience, were measured by "remember" and "know" responses. Experiment 1 showed that "remember" but not "know" responses were reduced by divided attention at study. Experiment 2 showed that massed versus spaced repetition of faces in the study list had opposite effects on "remember" and "know" responses. Massed repetition increased "know" responses and reduced "remember" responses. Spaced repetition increased "remember" responses and reduced "know" responses. The results of both experiments replicate previous findings from the verbal domain in the domain of face recognition, and hence they increase the ecological validity of this experimental approach to memory and awareness and the generality of its database. These findings are discussed from a rehearsal perspective on factors influencing the two states of awareness and in relation to the alternative "process dissociation" procedure.

The method of vanishing cues: an evaluation of its effectiveness in teaching memory-impaired individuals

The method of vanishing cues and a standard rote learning method were used to teach a group of memory-impaired individuals a small computer vocabulary. Learning was observed using both teaching methods but no advantage was found for either one. A second experiment was carried out where modifications were made to the vanishing cues procedure in order to facilitate the use of implicit memory. Retention was significantly better following study with rote learning than with the modified vanishing cues procedure. A theoretical interpretation of these results and the reason for the failure to replicate previous findings is given.

The detection of exaggerated or simulated memory disorder by neuropsychological methods

Some neuropsychological tests devised to detect exaggeration and simulation of memory disorder are reviewed with reference to models of memory and our current knowledge of the behaviour of amnesic patients. These tests are based on the assumption that naive simulators or exaggerators do not know either that amnesic patients can perform them normally, or near normally, or that subjects can only fail them by deliberate suppression of the correct response. It is concluded that several such tests show promise and are worthy of further development.

Focal retrograde amnesia following closed head injury: a case study and theoretical account

In this paper we present data from a closed head injury patient who presents a striking example of what Kapur (Cortex 29, 217-234, 1993) has termed " focal retrograde amnesia". The patient, D.H., is unable to recollect any autobiographical incidents from the pre-morbid period, although he is able to provide personal and public information from this period. The data are discussed in relation to other reported instances of focal retrograde amnesia and a preliminary theoretical account is offered.

A dissociation in the relation between memory tasks and frontal lobe tests in the normal elderly

In this study a group of elderly subjects were examined on three tests of frontal lobe function. Two of these tests, FAS word fluency and the Alternate Uses Test, were considered tests of spontaneous flexibility, as defined by Eslinger and Grattan [Neuropsychologia 31, 17-28, 1993]. The third, the modified Wisconsin Card Sorting Test (WCST), is considered a test of reactive flexibility. Performance on two tests of memory, release from proactive interference (PI) and a matched recall and recognition test was also measured. The elderly were shown to be impaired on all tests when compared with young controls. Analysis revealed that release from proactive interference was significantly correlated with performance on alternative uses but not WCST while the size of subjects' discrepancy between recall and recognition correlated strongly with WCST but not with Alternate Uses. In addition there was a strong correlation between the two measures of spontaneous flexibility but these measures did not correlate with WCST. Performance on the two measures of memory was also uncorrelated. The data indicate that the pattern of frontal deterioration in the elderly does not comprise a single deficit and, furthermore, that the relationship between frontal dysfunction and normal age-related memory loss is not unidimensional.

Further characterization of the executive memory impairment following frontal lobe lesions

In this article we describe a 41-year-old man who, following an operation to repair a ruptured anterior communicating artery aneurysm, manifested the "hallmark" features of a dysexecutive memory impairment. Of particular note was the patient's apparently normal level of recognition memory but impaired recall on tasks matched for difficulty in control subjects. However, further testing revealed that the patient's recognition memory was not normal under all circumstances. Implications of these data for the interpretation and further investigation of the dysexecutive deficit are discussed.

Aetiological variation in the amnesic syndrome: comparisons using the list discrimination task

In this study, the performance of amnesic patients with presumed temporal lobe damage was compared with that of patients with presumed diencephalic damage using the temporal list discrimination task. The two patient groups performed similarly on a measure of recognition, but the diencephalic group was impaired relative to the temporal lobe group on a measure of temporal discrimination. Discrimination performance in the temporal lobe group was significantly correlated with recognition memory. The data are interpreted as showing a qualitative difference in the form of amnesia arising from damage centred on the medial temporal lobes compared with that centred on the midline diencephalon.

Bilateral temporal lobe pathology with sparing of medial temporal lobe structures: lesion profile and pattern of memory disorder

The lesion sustained by the amnesic patient H.M. consisted of bilateral ablation of medial temporal lobe structures with relative sparing of more lateral white matter and neocortical structures. We present the first detailed report of a case where the reverse pattern of lesions predominated, namely bilateral pathology of white matter and neocortical temporal lobe structures, with spared medial temporal lobe structures. This damage, which was particularly severe in anterior loci in the temporal lobes, was sustained as a result of radionecrosis. High-resolution magnetic resonance imaging was carried out to document the distinctive anatomical profile of our patient, and this profile was compared to that reported for the patient H.M. At the anatomical level, there was an almost "mirror image" profile, with contrasting involvement of lateral and medial temporal lobe structures. At the neuropsychological level, our patient was not amnesic but showed patchy impairment on traditional tests of anterograde memory functioning, in the context of notable "semantic" memory loss for knowledge acquired before and after the onset of his illness. Our findings demonstrate that bilateral temporal lobe pathology by itself does not lead to a classical amnesic syndrome, but may result in a significant but more subtle "semantic" memory loss. Our data highlight the distinctive and dissociable contribution of lateral and medial temporal lobe structures to human memory processing, and suggest a major role for anterior-inferior neocortical temporal lobe mechanisms in aspects of knowledge acquisition, storage and retrieval.

Impairment of memory following discrete thalamic infarction

This paper presents a case of discrete thalamic infarction which damaged various structures in the region of the left thalamus. Localisation of the lesion was confirmed by MRI scanning. From the localisation of the lesion it was concluded that damage has been inflicted on the hippocampal pathway, the amygdalar pathway, and the pathway from perirhinal cortex to the dorso-medial thalamic nucleus. Neuropsychological evaluation revealed a severe verbal memory deficit on anterograde tests comparable with that shown by alcoholic Wernicke-Korsakoff patients. In contrast performance on non-verbal memory measures was normal. Performance on retrograde amnesia tests indicated near-normal performance. A final finding was that memory for temporal information was impaired for both verbal and non-verbal information but only on anterograde tests. The data provide support for the view that a lesion in the anterior thalamus can produce amnesia if it compromises the hippocampal pathway and either the amygdalar pathway or that arising from the perirhinal cortex and terminating in the dorso-medial nucleus of the thalamus. On the basis of evidence from other studies it is concluded that the most likely interpretation is that the lesion must compromise the hippocampal and perirhinal cortex pathways. The pattern of memory impairment is described in some detail and these provide a basis for discussing the role of diencephalic structures in memory performance.

Recency judgements in Wernicke-Korsakoff and post-encephalitic amnesia: influences of proactive interference and retention interval

This study further examines the performance of diencephalic and temporal lobe amnesics on the recency judgement task (Parkin, Leng and Hunkin, 1990). The two patient groups were represented by patients with Wernicke-Korsakoff syndrome (WKS) and post-Herpes simplex encephalitis (HSE). Experiment 1 demonstrated that poorer recency judgements by WKS patients were not due to a general proactive interference effect, but from an inability to remember which items had been designated targets on a given trial. Experiment 2 demonstrated that the superior performance of the HSE group was not attributable to a putative faster forgetting rate. In addition, the study found no relationship between recency judgements and degree of frontal lobe impairment. It is concluded that diencephalic damage has a particular effect on the ability to make recency judgements and that this represents a fundamental difference between diencephalic and temporal lobe amnesia. Theoretical interpretations of this difference are discussed.

On the origin of functional differences in recollective experience

Subjects studied target words that were repeated either immediately (lag0) or after six intervening items (lag6). At retention testing, subjects were required to discriminate targets from distractors and, contingent on a 'yes' response, to classify each identified item as one that evoked either a 'remember' (R) response or a 'know' (K) response. An R response indicated recognition based on conscious recollection, and K, recognition without conscious recollection. R responses were significantly greater in lag6 than lag0 whereas the reverse was found for K responses. The data are interpreted as showing that R responses depend on the probability of a target stimulus engaging conscious effortful processing, whereas K responses are increased in the absence of conscious involvement at learning.

Impaired temporal context memory on anterograde but not retrograde tests in the absence of frontal pathology

This study examined the memory performance of patient RK who developed substantial memory impairments due to a hypothalamic glioma but in the absence of any evidence of frontal disturbance. RK was evaluated on both tests of anterograde and retrograde memory for temporal context. In the first experiment he exhibited marked deficits on a list discrimination task even when recognition performance was well within control range. Experiment 2 confirmed this disproportionate impairment of temporal order memory and showed that RK's list discrimination deficit was as severe as that found in alcoholic Wernicke-Korsakoff Syndrome patients. Experiment 3 showed that RK's temporal discrimination deficit was not a general deficit in discrimination because he performed normally on a spatial discrimination test of comparable difficulty to the temporal task. Experiment 4 examined RK's memory for deceased famous people and his ability to indicate the half decade in which they died. RK's performance was indistinguishable from controls whereas WKS patients were extremely impaired. This study adds to the view that frontal damage is not a necessary condition for impairment on anterograde measures of temporal context memory. However, further evidence from this study indicates that temporal judgments about pre-existing memories may depend on intact frontal lobe functioning.

Progressive aphasia without dementia--a clinical and cognitive neuropsychological analysis

This article provides a clinical and cognitive neuropsychological analysis of a patient who presented a marked and progressive linguistic disturbance in the absence of any other significant cognitive impairment. A PET scan indicated that this disorder was associated with focal left temporofrontal hypometabolism. The essential characteristics of this disorder were anomia, surface dyslexia, and surface dysgraphia, along with a mild grammatical disturbance and deficits in both visual and auditory word comprehension. The patient's disorder is considered in relation to other similar cases and to modular accounts of acquired linguistic disorders.

Use of temporal context information in Alzheimer's disease

Current theories of memory and memory dysfunction emphasize the importance of the use of contextual information in the storage and retrieval of specific episodes. Patients with lesions primarily in the diencephalon perform poorly on a measure of temporal recency, while those with temporal lobe amnesia are significantly better. The present study evaluated the ability of Probable AD patients to utilize information about temporal recency in the context of a recognition memory task. The performance of the AD patients was significantly impaired and resembled that of patients with Korsakoff's syndrome. The pattern of performance suggested that they were able to recognize which stimuli had been previously presented, but were unable to recall the correct temporal context. Further, there were no significant correlations between measures of temporal recency and those of frontal lobe function. These data suggest that AD patients, like other groups of patients with severe memory defects, are impaired at the use of context information in their attempts to remember recent events.

Age differences in implicit memory: more apparent than real

Elderly subjects and a group of young subjects identified fragmented picture sequences under conditions of focused attention. Two other groups of young subjects carried out this task under divided-attention conditions. Implicit memory, as measured by item-specific savings, was found in all groups, but this effect was smaller in the elderly group. The young subjects, but not elderly subjects, performed better on new items. The divided-attention conditions equated recall and recognition by the young and the elderly, but only the young subjects showed greater savings for recalled items. The elderly subjects' reduced implicit memory therefore stemmed from their inability to facilitate implicit memory with explicit memory. A second experiment, involving only young subjects tested after delay, produced findings similar to those for the young divided-attention subjects. Implicit memory, as measured by savings in picture completion, does not show an age-related change when the role of explicit memory is considered. Age does, however, reduce skill learning.

Neuropsychological sequelae of Wernicke's encephalopathy in a 20-year-old woman: selective impairment of a frontal memory system

This article reports the neuropsychological sequelae of Wernicke's Encephalopathy in a 20-year-old woman. After amelioration of acute symptoms, the patient showed a range of cognitive impairments the most marked of which was a severe impairment on free recall tasks involving both verbal and nonverbal material. In contrast, recognition memory appeared remarkably well preserved. Some evidence of frontal lobe and general intellectual impairment was also noted. The case is discussed in terms of the pathophysiology of Wernicke-Korsakoff Syndrome, criteria for its diagnosis, and the multicomponent nature of memory deficits.

Recollective experience, normal aging, and frontal dysfunction

This study examined the nature of verbal recognition memory in young and old subjects. Following presentation of a word list, subjects undertook a yes-no recognition test and indicated whether their decision was based on explicit recollection or assessment of familiarity. Explicit recollection declined with age, and familiarity-based recognition increased. Furthermore, the extent to which older subjects relied on familiarity-based recognition correlated with neuropsychological indices of frontal lobe dysfunction. A further experiment indicated that the change from explicit recollection to familiarity-based responding was unrelated to changes in older subjects' confidence about their memory. The data indicate the central role of frontal dysfunction in understanding age-related memory loss.

Naming impairments following recovery from herpes simplex encephalitis: category-specific?

An apparently clear case of category-specific naming impairment selectively affecting animals was detected in a patient who had recovered from herpes simplex encephalitis. However, subsequent investigation demonstrated that these category-specific effects could be eliminated by controlling simultaneously for three factors in picture naming: word frequency, concept familiarity, and visual complexity. The results emphasize the importance of controlling for all factors pertinent to picture naming when attempting to demonstrate category specificity in picture naming. Further testing indicated that deficits were also apparent when naming to definition was required, and some impairment in the ability to answer questions about objects and living things was also noted. Theoretical implications of these data are considered.

Recollective experience, normal aging, and frontal dysfunction

This study examined the nature of verbal recognition memory in young and old subjects. Following presentation of a word list, subjects undertook a yes-no recognition test and indicated whether their decision was based on explicit recollection or assessment of familiarity. Explicit recollection declined with age, and familiarity-based recognition increased. Furthermore, the extent to which older subjects relied on familiarity-based recognition correlated with neuropsychological indices of frontal lobe dysfunction. A further experiment indicated that the change from explicit recollection to familiarity-based responding was unrelated to changes in older subjects' confidence about their memory. The data indicate the central role of frontal dysfunction in understanding age-related memory loss.

Memory loss following radiotherapy for nasal pharyngeal carcinoma--an unusual presentation of amnesia

In this article we describe a patient who developed amnesia several years after receiving a second course of radiotherapy treatment for nasopharyngeal cancer (NPC). Detailed assessment of memory indicated a marked anterograde impairment for verbal material with less impaired non-verbal memory. A dense retrograde deficit was also present, reflected in both poor event memory and loss of general knowledge. Performance on other tests indicated a mild intellectual deficit but no other cognitive impairments. The findings indicate a striking memory disorder arising from late temporal lobe necrosis. These findings stress the importance of assessing neuropsychological sequelae when evaluating the long-term outcome of radiotherapy for NPC and other cancers of the head and neck.

Wernicke-Korsakoff syndrome of nonalcoholic origin

We describe a patient who developed a severe loss of memory following intravenous feeding and intestinal surgery. The pattern of both anterograde and retrograde memory impairment and frontal pathology is shown to be comparable with that observed in patients with Wernicke-Korsakoff Syndrome of an alcoholic etiology. The data strengthen the view that the essential characteristics of the Wernicke-Korsakoff Syndrome are not dependent on a prior history of chronic alcoholism. Implications of these data for the interpretation of alcoholic Wernicke-Korsakoff Syndrome are considered.

Alien Hand Sign and Other Cognitive Deficits following Ruptured Aneurysm of the Anterior Communicating Artery

We describe a right-handed patient who suffered a ruptured aneurysm of the anterior communicating artery (ACoA) which was clipped successfully. Computerized tomography indicated a low density area in the genu of the corpus callosum and the infero-lateral aspect of the left frontal lobe. On recovery the patient's most notable deficit was the "alien hand sign" whereby the left hand would frequently interfere with the actions of the right hand. Problems in response initiation were also evident. There was significant memory loss and performance was impaired on some tests of frontal lobe function. Discussion centres on the functional locus of the alien hand sign but other aspects of the patient's deficits are also considered.

Attention and recollective experience in recognition memory

The functional relation between recognition memory and conscious awareness was assessed in an experiment in which undivided attention at study was compared with two divided attention conditions, one more demanding than the other. When recognizing a word from the study list, subjects indicated whether they could consciously recollect its prior occurrence or recognized it on some other basis, in the absence of conscious recollection. Divided attention at study progressively impaired word recognition accompanied by conscious recollection. Recognition in the absence of conscious recollection was not affected by divided attention. These findings are interpreted as providing further support for the idea that recognition memory entails two distinct components, one based on associative and contextual information, the other based on a "traceless" awareness of familiarity.

On the differential nature of implicit and explicit memory

In this article, we report two experiments that provide further evidence concerning the differential nature of implicit and explicit memory. In Experiment 1, subjects first undertook a sentence-verification task. While carrying out this task, half of the subjects were also required to carry out a secondary processing task involving tone monitoring. Twenty-four hours later, the subjects' memory for target items in the sentence-verification task was tested explicitly by means of a recognition task and implicitly by examining the extent to which the items primed fragment completion. Recognition performance was significantly impaired by the imposition of secondary processing demands during the original learning phase. In contrast, fragment completion was completely unaffected by this additional processing, even though substantial priming was observed. In Experiment 2, we examined whether priming in fragment completion is influenced by the nature of repetition during initial learning. Subjects studied a list of target items that were each repeated twice. Half the items were repeated immediately (lag 0) and half were repeated after six intervening items (lag 6). Memory for the items was assessed by recognition and by priming in fragment completion. Recognition was affected by lag, with lag 6 items being recognized better than lag 0 items. However, although significant priming was obtained, the extent of this priming was uninfluenced by lag. These data indicate two additional dimensions along which implicit and explicit memory differ and, furthermore, they support recent conceptualizations of processing differences underlying these two forms of memory.

Differential sensitivity to context in diencephalic and temporal lobe amnesia

This study compares diencephalic and temporal lobe amnesics on a memory task in which the encoding of temporal context is essential for accurate performance. On trial 1 subjects were shown four pictures and asked to discriminate them from distractors one minute later. On the three subsequent trials the same procedure was used except that items previously used as distractors became targets and vice versa. The results showed that both groups performed close to ceiling on trial 1. On trials 2, 3, and 4, however, the diencephalic group showed poorer accuracy than the temporal lobe group. These results indicate that the diencephalic amnesics have greater difficulty encoding distinctive contexts across trials 2, 3, and 4 than do the temporal lobe group. Explanations of this difference are discussed briefly.

Contextual cueing effects in the remote memory of alcoholic Korsakoff patients and normal subjects

This study examines the effects of contextual cueing on the remote memory of alcoholic Korsakoff patients and normal subjects. Naming of personalities who became famous in each of the five decades beginning 1935 was tested under two conditions: "no-context", in which minimal extraneous cues to identification were provided, and "context", where clear extraneous cues were available. Normal subjects performed better than Korsakoff patients, showed no evidence of a temporal gradient, and exhibited a contextual cueing advantage across all decades. In contrast, Korsakoff patients demonstrated a marked temporal gradient, and the contextual cueing advantage declined systematically as more recent decades were sampled. Further analyses demonstrated that the differential pattern of deficits shown by Korsakoffs and controls was not attributable to absolute differences in performance level. Theoretical implications of these data for explanations of Korsakoff retrograde amnesia are discussed.

Aetiological variation in the amnesic syndrome: comparisons using the Brown-Peterson task

This study examined the performance of temporal lobe and Korsakoff amnesic patients on two versions of the Brown-Peterson task. One version involved trials with distractor intervals ranging from three to 60 second. The other investigated the effects of massed versus distributed practice with a constant nine-second retention interval. Korsakoff patients produced significantly poorer performance on both versions of the task. Further analyses indicated that impaired Brown-Peterson performance was correlated with frontal dysfunction but not with the severity of the memory deficit. Previous inconsistencies concerning the performance of amnesic patients on the Brown-Peterson task are considered.

Double dissociation of frontal dysfunction in organic amnesia

Subjects with either diencephalic or bilateral medial temporal lobe amnesia were examined on the Wisconsin Card Sorting Test (WCST) and Cognitive Estimation Test (CET). Alcoholic Korsakoff patients performed more poorly on the WCST but normally on the CET, whereas post-encephalitic patients performed normally on the WCST but poorly on the CET. This double dissociation is interpreted as reflecting different patterns of frontal dysfunction in Korsakoff and post-encephalitic amnesia.