Remembering and knowing in patients with frontal lobe injuries

Two experiments compared the performance of patients with pathology restricted to the prefrontal cortex to healthy controls on recognition tests that were followed by the remember/know procedure. Across both experiments, patients recognized roughly as many target items as control participants. Injuries centered in the frontal poles resulted in deficits that were selective to episodic remembering while apparently sparing semantic knowing. Patients with lesions restricted to dorsolateral prefrontal cortex were not impaired at either remembering or knowing. Results demonstrate a dissociation of cognitive function within the prefrontal cortex, and suggest that episodic remembering may share a family resemblance with other neurocognitive functions dependent upon polar aspects of the frontal lobes, such as self-recognition, anticipation, and planning.     

Autobiographical memory, autonoetic consciousness, and identity in Asperger syndrome

Previous results from research on individuals with Asperger syndrome (AS) suggest a diminished ability for recalling episodic autobiographical memory (AM). The primary aim of this study was to explore autobiographical memory in individuals with Asperger syndrome and specifically to investigate whether memories in those with AS are characterized by fewer episodic ‘remembered’ events (due to a deficit in autonoetic consciousness). A further aim was to examine whether such changes in AM might also be related to changes in identity, due to the close relationship between memory and the self and to the established differences in self-referential processes in AS. Eleven adults with AS and fifteen matched comparison participants were asked to recall autobiographical memories from three lifetime periods and for each memory to give either a remember response (autonoetic consciousness) or a know response (noetic consciousness). The pattern of results shows that AS participants recalled fewer memories and that these memories were more often rated as known, compared to the comparison group. AS participants also showed differences in reported identity, generating fewer social identity statements and more abstract, trait-linked identities. The data support the view that differences in both memory and reported personal identities in AS are characterized by a lack of specificity.     

Deeper processing is beneficial during episodic memory encoding for adults with Williams syndrome

Previous research exploring declarative memory in Williams syndrome (WS) has revealed impairment in the processing of episodic information accompanied by a relative strength in semantic ability. The aim of the current study was to extend this literature by examining how relatively spared semantic memory may support episodic remembering. Using a level of processing paradigm, older adults with WS (aged 35–61 years) were compared to typical adults of the same chronological age and typically developing children matched for verbal ability. In the study phase, pictures were encoded using either a deep (decide if a picture belongs to a particular category) or shallow (perceptual based processing) memory strategy. Behavioural indices (reaction time and accuracy) at retrieval were suggestive of an overall difficulty in episodic memory for WS adults. Interestingly, however, semantic support was evident with a greater recall of items encoded with deep compared to shallow processing, indicative of an ability to employ semantic encoding strategies to maximise the strength of the memory trace created. Unlike individuals with autism who find semantic elaboration strategies problematic, the pattern of findings reported here suggests in those domains that are relatively impaired in WS, support can be recruited from relatively spared cognitive processes.     

How do Korsakoff patients learn new concepts?

The goal of the present investigation was to assess semantic learning in Korsakoff patients (KS), compared with uncomplicated alcoholics (AL) and control subjects (CS), taking the nature of the information to-be-learned and the episodic memory profiles of the three groups into account.Ten new complex concepts, each illustrated by a photo and composed of a label, a category and three features, were taught to 13 KS, 23 AL and 45 CS. When examined independently of the main experimental task, the two patients’ groups presented episodic memory, working memory and executive impairments but episodic memory was more severely impaired in KS.Both AL and KS exhibited label learning deficits but KS were more severely impaired than AL. The episodic memory results were the main factor accounting for label learning performance when the three groups were pooled together. When examined within each group, the correlation was significant in CS and AL but not in KS. Only KS exhibited impaired category and feature learning results. Episodic memory did not account for category and feature learning performance.New label learning may be equivalent to that of proper names, requiring the involvement of episodic memory notably to arbitrarily associate a meaningless word with a specific identity. However, when episodic memory is severely impaired like in KS, an alternative neocortical learning route, bypassing episodic memory, may be invoked. Category and feature seem to be acquired independently of episodic memory. The specific impairment in category and feature learning in KS may therefore reflect a genuine deficit of semantic memory in Korsakoff's syndrome.     

An fMRI study of verbal episodic memory encoding in amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) is a high-risk and often prodromal state for the development of Alzheimer's disease (AD) and is characterised by isolated episodic memory impairment. Functional neuroimaging studies in healthy subjects consistently report left prefrontal cortex (PFC) activation during verbal episodic memory encoding. The PFC activation at encoding is related to semantic processing which enhances memory. The purpose of this study was to ascertain whether impaired verbal episodic memory in aMCI is related to PFC dysfunction. Using functional magnetic resonance imaging (fMRI) we compared 10 aMCI patients with 10 elderly controls during verbal encoding. The encoding task was sensitive to the effects of semantic processing. Subsequent recognition was tested to measure encoding success. Behavioural results revealed impaired recognition and a lower false recognition rate for semantically related distracters (lures) in aMCI, which suggest impaired semantic processing at encoding. Both groups activated left hemispheric PFC, insula, premotor cortex and cerebellum, but group comparisons revealed decreased activation in left ventrolateral PFC in the aMCI group. The magnitude of activation in left ventrolateral PFC during encoding was positively correlated with recognition accuracy in the control group but not in the aMCI group. We propose that verbal episodic memory impairment in aMCI is related to PFC dysfunction which affects semantic processing at encoding.     

I cannot remember,but I know my past events: remembering and knowing in a patient with amnesic syndrome

Case Y.K. has severe anterograde amnesia and a selective loss of specific personal episodes in his remote memories (Hirano & Noguchi, 1998). In this paper, we attempted to analyze remembering (R) and knowing (K) responses, that is, the relationship between autobiographical remembering and remembering accompanied by subjective experience. Although the rate of R responses was significantly higher than that of K responses in control subjects, Y.K.'s R responses were rare in all subtypes of remote memories. Based on these results, we conclude that Y.K.'s memories on autobiographical incident task were not based on episodic memory but rather on semantic memory. Thus, the autobiographical incidents he could recall were not episodic memory, and his semantic memory made him recall information as fact rather than episode.     

Recognition of Facial Expressions and Prosodic Cues with Graded Emotional Intensities in Adults with Asperger Syndrome

This study investigated the ability of adults with Asperger syndrome to recognize emotional categories of facial expressions and emotional prosodies with graded emotional intensities. The individuals with Asperger syndrome showed poorer recognition performance for angry and sad expressions from both facial and vocal information. The group difference in facial expression recognition was prominent for stimuli with low or intermediate emotional intensities. In contrast to this, the individuals with Asperger syndrome exhibited lower recognition accuracy than typically-developed controls mainly for emotional prosody with high emotional intensity. In facial expression recognition, Asperger and control groups showed an inversion effect for all categories. The magnitude of this effect was less in the Asperger group for angry and sad expressions, presumably attributable to reduced recruitment of the configural mode of face processing. The individuals with Asperger syndrome outperformed the control participants in recognizing inverted sad expressions, indicating enhanced processing of local facial information representing sad emotion. These results suggest that the adults with Asperger syndrome rely on modality-specific strategies in emotion recognition from facial expression and prosodic information.     

Episodic and Semantic Autobiographical Memory in Adults with Autism Spectrum Disorders

Episodic and semantic autobiographical memories were examined in a group of adults with autism spectrum disorders (ASD) and a control group matched for age, gender and IQ. Results demonstrated a personal episodic memory deficit in the ASD group in the absence of a personal semantic memory deficit, suggesting a deficit dissociation between these two components of memory in ASD. Further analysis of memories across different lifetime periods revealed the adolescent and early adult lifetime periods to facilitate memory recall in the control group, but not in the ASD group. These findings suggest a distinctive pattern of remembering in ASD.     

Autobiographical Memory and Social Problem-solving in Asperger Syndrome

Difficulties in social interaction are a central feature of Asperger syndrome. Effective social interaction involves the ability to solve interpersonal problems as and when they occur. Here we examined social problem-solving in a group of adults with Asperger syndrome and control group matched for age, gender and IQ. We also assessed autobiographical memory, on a cueing task and during social problem-solving, and examined the relationship between access to specific past experiences and social problem-solving ability. Results demonstrated a social problem-solving impairment in the Asperger group. Their solutions were less detailed, less effective and less extended in time. Autobiographical memory performance was also impaired with significantly longer latencies to retrieve specific memories and fewer specific memories retrieved in comparison to controls.     

Episodic memory,semantic memory,and amnesia

Episodic memory and semantic memory are two types of declarative memory. There have been two principal views about how this distinction might be reflected in the organization of memory functions in the brain. One view, that episodic memory and semantic memory are both dependent on the integrity of medial temporal lobe and midline diencephalic structures, predicts that amnesic patients with medial temporal lobe/diencephalic damage should be proportionately impaired in both episodic and semantic memory. An alternative view is that the capacity for semantic memory is spared, or partially spared, in amnesia relative to episodic memory ability. This article reviews two kinds of relevant data: 1) case studies where amnesia has occurred early in childhood, before much of an individual's semantic knowledge has been acquired, and 2) experimental studies with amnesic patients of fact and event learning, remembering and knowing, and remote memory. The data provide no compelling support for the view that episodic and semantic memory are affected differently in medial temporal lobe/diencephalic amnesia. However, episodic and semantic memory may be dissociable in those amnesic patients who additionally have severe frontal lobe damage. Hippocampus 1998;8:205–211. Published 1998 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

The influence of seizure frequency on anterograde and remote memory in mesial temporal lobe epilepsy

PurposeSeizure frequency, although considered as an important factor in memory impairment in mesial temporal epilepsy (mTLE), is mostly confounded with other clinical variables, making it unclear to what extent recurrent seizures actually interfere with memory. The present study focuses on the influence of seizure frequency, studied as a main variable, on anterograde and remote memory.MethodsSeventy-one patients with unilateral mTLE were divided into two subgroups, as a function of their seizure frequency (monthly versus weekly seizures). Other seizure-related variables were controlled, namely, lateralisation and type of lesion, age at onset, years of ongoing seizures, etiologic factors, and number of AED. A comprehensive neuropsychological examination, including anterograde memory (verbal and non verbal recognition memory and free recall) tasks together with a large range of tests exploring different domains of remote memory, was carried out.ResultsDespite similar results on IQ, executive functions and attention, the low seizure-frequency group performed significantly better than the high seizure-frequency group on anterograde memory tests. Loss of autobiographical episodes and public-events memory, concomitant with spared personal semantic knowledge, was observed in both patient groups compared with healthy subjects. A worsening effect of high seizure frequency was recorded for autobiographical incidents and news-events memory, but unexpectedly, not for memory for famous people.ConclusionThe study of seizure frequency as the main variable leads us to suggest that high seizure frequency, itself, potentiates the effects of mesial temporal lobe damage on episodic memory deficits.     

Episodic memory deficit in elderly adults with suspected delusional disorder

Herlitz A, Forsell Y. Episodic memory deficit in elderly adults with suspected delusional disorder. Acta Psychiatr Scand 1996: 93: 355–361. © Munksgaard 1996. This study examined memory functions in two groups of elderly adults with and without suspected delusional disorder (SDD). The samples consisted of 66 normal elderly subjects and 33 elderly subjects with symptoms, as reported by close informants, of delusional disorder. Subjects were matched with regard to age, gender and education, and there were no differences between the two groups with regard to performance of visuo-spatial and primary memory tasks. Subjects were examined concerning a variety of episodic recall and recognition tasks. The results demonstrated that subjects with SDD performed at a lower level than controls for some episodic memory tasks (i.e. recall tasks). There were no group differences in measures of episodic recognition or in the primary memory tasks. In addition, the group of subjects with SDD was, to the same extent as the control group, able to utilize cognitive support in the form of organization, cues and previous knowledge in order to enhance episodic memory. In summary, it appears that elderly adults with SDD have a mild episodic memory deficit in the absence of other cognitive deficits.     

The production effect in adults with dysarthria: improving long-term verbal memory by vocal production

People show better memory for words read aloud relative to words read silently, the Production Effect (PE). Vocalisation at study makes the produced (aloud) words more distinct than the non-produced (silent) words, hence more memorable. Such encoding distinctiveness is related to the additional processing of aloud words that is later used during retrieval. This study investigated the PE in dysarthric adults, characterised by speech production difficulties. Their memory performance (recognition) was compared to a group of healthy adults. Results showed a PE for both groups. The production benefit was significantly larger for the dysarthric adults, despite their overall memory performance being reduced relative to controls. The results demonstrate long-term verbal memory deficits in dysarthria, and suggest that vocalisation (although impaired) may assist in remembering. Hence, vocalisation may be used in intervention contexts with this population, to compensate for memory decrease.     

Mapping episodic memory

This paper presents an analysis of brain regions generally associated with a frequently used episodic memory task; visual word recognition. The results from five positron emission tomography studies of regional cerebral blood flow, involving a total of nine pairwise comparisons of brain activity related to episodic retrieval and to performance on non-episodic reference tasks, were considered. Across studies, increased activity has been observed in the right anterior and posterior prefrontal, anterior cingulate, bilateral parietal, and cerebellar regions. Decreased activity has been found in bilateral temporal and left midfrontal regions. Comparison of this activation pattern with those of other memory tasks, episodic and semantic, indicate that the right anterior and posterior prefrontal regions guide processes selectively demanded by episodic memory retrieval. There is suggestive evidence from subtraction analyses that these prefrontal regions are activated by different processing components, and analyses of functional connectivity provide further support for functional differentiation. These analyses also point to a critical role of medial-temporal brain regions in episodic retrieval. Taken together, these results show that episodic memory retrieval is mediated by an extensive set of brain regions, some of which seem to be specifically engaged by episodic remembering.     

Examining the neural basis of episodic memory: ERP evidence that faces are recollected differently from names

Episodic memory is supported by recollection, the conscious retrieval of contextual information associated with the encoding of a stimulus. Event-Related Potential (ERP) studies of episodic memory have identified a robust neural correlate of recollection—the left parietal old/new effect—that has been widely observed during recognition memory tests. This left parietal old/new effect is believed to provide an index of generic cognitive operations related to recollection; however, it has recently been suggested that the neural correlate of recollection observed when faces are used as retrieval cues has an anterior scalp distribution, raising the possibility that faces are recollected differently from other types of information. To investigate this possibility, we directly compared neural activity associated with remember responses for correctly recognized face and name retrieval cues. Compound face–name stimuli were studied, and at test either a face or a name was presented alone. Participants discriminated studied from unstudied stimuli, and made a remember/familiar decision for stimuli judged ‘old’. Remembering faces was associated with anterior (500–700 ms) and late right frontal old/new effects (700–900 ms), whereas remembering names elicited mid frontal (300–500 ms) and left parietal (500–700 ms) effects. These findings demonstrate that when directly compared, with reference to common episodes, distinct cognitive operations are associated with remembering faces and names. We discuss whether faces can be remembered in the absence of recollection, or whether there may be more than one way of retrieving episodic context.     

Long-term memory and levels-of-processing in autism

Prior studies reported that long-term memory (LTM) was basically unimpaired in individuals with autism. However, people with autism have been found to perform worse than ability-matched controls when verbal materials to be remembered are semantically related. In normal subjects, semantic processing of verbal materials facilitates LTM better than 'shallow' (phonological or perceptual) processing, which is known as the levels-of-processing effect. In this study, the relationship between LTM and semantic processing was investigated using a levels-of-processing task. In Study 1, a levels-of-processing task was conducted on healthy volunteers, which confirmed the levels-of-processing effect with our task. In study 2, the same task was conducted on autistic subjects with mild or no mental retardation and ability-matched controls. The levels-of-processing effect was confirmed in the control group. Although overall performance in the two groups was comparable, the levels-of-processing effect was not found in the autistic group. LTM resulting from perceptual processing was better in the autistic group than in the control group, indicating superior "rote memory" in individuals with autism. Furthermore, the pattern of correlations between LTM performance and cognitive measures differed greatly between the two groups. The lack of the levels-of-processing effect, which has not been reported in other psychiatric or neuropathological conditions, suggests an abnormal relationship between semantic memory and episodic memory in individuals with autism.     

Infant febrile seizures: Changes in declarative memory as revealed by event-related potentials

Objective

According to a widespread opinion the vast majority of infant febrile seizures (IFS) are harmless. However, IFS are often associated with hippocampal sclerosis, which should lead to deficient episodic memory with spared context-free semantic memories. Although IFS represent the most common convulsive disorder in children, these consequences are rarely examined.

Methods

We measured the hippocampal volume of 17 IFS children (7–9 years old) and an age-matched control group on the basis of MR images. Furthermore, we examined episodic and semantic memory performance with standardized neuropsychological tests. Two processes underlying recognition memory, namely familiarity and recollection, were assessed by means of event-related potentials (ERP).

Results

The IFS children did not show a decreased hippocampus volume. Intelligence, working memory, semantic and episodic memory were intact. However, ERP indices of recognition memory subprocesses revealed deficits in recollection-based remembering that presumably relies on the integrity of the hippocampus, whereas familiarity-based remembering seemed to be intact.

Conclusions

Although hippocampus volume remains unaffected, IFS seems to induce functional changes in the MTL memory network, characterized by a compensation of recollection by familiarity-based remembering.

Significance

This study significantly adds to the debate on the consequences of IFS by differentiating the impact on memory processing.     

Is there evidence for an emotion-related bias in verbal learning or memory in individuals putatively high at risk for mania?

There is broad evidence that individuals with bipolar disorder show deficits in verbal memory and learning. Such deficits seem to be independent of acute mood episodes and to manifest after the onset of the disorder. Less research has been conducted in relation to more specific memory functions, particularly to verbal memory and learning for emotional information. Therefore, the objective of the present study is to investigate if there is evidence for an affective memory bias in at-risk individuals before the onset of affective disorder. We applied the Emotional Auditive Verbal Learning Test to individuals at risk for mania and at risk for depression, as well as to a control group. We hypothesized a mania-related memory bias for individuals at risk of mania. We found no evidence for an overall learning or memory deficit in the high-risk groups. All groups performed better learning and remembering neutral words compared to emotionally valenced words, however, contrary to our hypothesis there was no specific emotion-related learning or memory bias in the two high-risk groups. There was no evidence of impairments in verbal learning and memory overall and for emotional contents before the onset of affective disorders.     

The influence of semantic encoding on recognition memory in Alzheimer''s disease

Within the framework of the distinction between episodic and semantic memory, it has been argued that these two memory systems are organised in a hierarchical way. The hierarchical hypothesis assumes that episodic memory is a specific subsystem of semantic memory and therefore implies that episodic memory cannot exist without semantic memory. If this hypothesis is correct, it should be expected that patients with impaired semantic memory also have impaired episodic memory. In the present study, two experiments investigated the influence of semantic encoding on recognition memory performance in a population of 20 patients with Alzheimer's disease and 18 normal controls. Both experiments assessed recognition memory for semantically-related items. In Experiment 2, but not in Experiment 1, subjects were explicitly instructed to make a semantic association between the items. Alzheimer's disease patients were impaired, compared to the normal controls, on the recognition memory performance of both experiments. The ability to make a semantic association between two items was significantly and positively correlated with the subjects' performance on the recognition tasks. A further analysis showed that patients who were impaired on the semantic association task did significantly worse on the recognition task of Experiment 2 than normal controls and patients who were unimpaired on the semantic association task. These findings are discussed in the context of memory deficits in Alzheimer's disease, and are interpreted as supporting the view that episodic memory for an item is affected by the level of semantic awareness of that same item.