Biomedical subjects

M Verfaellie

Publications and source records attributed to M Verfaellie.

At least 19 recordsLinked to original sources

PubMed2000

Fear recognition deficits after focal brain damage: a cautionary note.

OBJECTIVE: To test the hypothesis that fear recognition deficits in neurologic patients reflect damage to an emotion-specific neural network. BACKGROUND: Previous studies have suggested that the perception of fear in facial expressions is mediated by a specialized neural system that includes the amygdala and certain posterior right-hemisphere cortical regions. However, the neuropsychological findings in patients with amygdala damage are inconclusive, and the contribution of distinct cortical regions to fear perception has only been examined in one study. METHODS: We studied the recognition of six basic facial expressions by asking subjects to match these emotions with the appropriate verbal labels. RESULTS: Both normal control subjects (n = 80) and patients with focal brain damage (n = 63) performed significantly worse in recognizing fear than in recognizing any other facial emotion, with errors consisting primarily of mistaking fear for surprise. Although patients were impaired relative to control subjects in recognizing fear, we could not obtain convincing evidence that left, right, or bilateral lesions were associated with disproportionate impairments of fear perception once we adjusted for differences in overall recognition performance for the other five facial emotion categories. The proposed special role of the amygdala and posterior right-hemisphere cortical regions in fear perception was also not supported. CONCLUSIONS: Fear recognition deficits in neurologic patients may be attributable to task difficulty factors rather than damage to putative neural systems dedicated to fear perception.

Adult↗

PubMed2000

Acquisition of novel semantic information in amnesia: effects of lesion location.

Two patients with severe global amnesia are described who differ in the extent to which they have acquired new semantic information. Patient SS, who has extensive medial temporal lobe damage including the hippocampus as well as surrounding cortical areas, has failed to acquire virtually any new information regarding vocabulary or famous faces that entered the public domain since the onset of his amnesia. In contrast, patient PS, who has a selective lesion of the hippocampus proper, has gained a sense of familiarity of novel vocabulary and famous people, even though her effortful retrieval of this new semantic knowledge remains impaired. These findings extend to amnesia of adult onset, the proposal of Vargha-Khadem and colleagues that in patients with selective hippocampal injury, cortical areas surrounding the hippocampus may play an important role in new semantic learning [Vargha-Khadem, F., Gadian, D.G., Watkins, K. E., Connelly, A., Van Paesschen, W. and Mishkin, M., regarding the importance of the subhippocampal cortices in the mediation of new semantic learning in children with hippocampal lesions, Science, 1997, 277, 376-380].

Amnesia↗

PubMed1999

Perceptual fluency as a cue for recognition judgments in amnesia.

This study investigated the extent to which amnesic patients use fluency of perceptual identification as a cue for recognition. Perceptual fluency was measured by having participants gradually unmask words before making recognition judgments. In Experiment 1, familiarity was the only possible basis for recognition because no words had been presented in the study phase. In Experiment 2, recollection provided an alternative basis for recognition because words had appeared in the study phase. Amnesic patients were as likely as normal controls to use perceptual fluency as a cue for recognition in Experiment 1 but were more likely than controls to do so in Experiment 2. For both groups, perceptual fluency affected judgments for studied and unstudied items to the same extent in Experiment 2. These findings suggest that amnesic patients do use perceptual fluency cues, but reliance on perceptual fluency does not necessarily elevate recognition accuracy.

Amnesia↗

PubMed1998

Font-specific priming following global amnesia and occipital lobe damage.

Font-specificity in visual word-stem completion priming was examined in patients with global amnesia and Patient M.S., who had a right-occipital lobectomy. Word-stems appeared in the same or different font as study words. Amnesic patients showed normal font-specific priming (greater priming for words studied in the same than different font as test), despite impaired word-stem cued recall. Patient M.S. failed to exhibit font-specific priming, despite preserved declarative memory. Therefore, perceptual specificity in visual priming depends on visual processes mediated by the right-occipital lobe rather than medial temporal and diencephalic regions involved in declarative memory.

Adult↗

PubMed1998

When true recognition suppresses false recognition: evidence from amnesic patients.

False recognition occurs when people mistakenly claim that a novel item is familiar. After studying lists of semantically related words, healthy controls show extraordinarily high levels of false recognition to nonstudied lures that are semantic associates of study list words. In previous experiments, we found that both Korsakoff and non-Korsakoff amnesic patients show reduced levels of false recognition to semantic associates, implying that the medial temporal/diencephalic structures that are damaged in amnesic patients are involved in the encoding and/or retrieval of information that underlies false recognition. These data contrast with earlier results indicating greater false recognition in Korsakoff amnesics than in control subjects. The present experiment tests the hypothesis that greater or lesser false recognition of semantic associates in amnesic patients, relative to normal controls, can be demonstrated by creating conditions that are more or less conducive to allowing true recognition to suppress false recognition. With repeated presentation and testing of lists of semantic associates, control subjects and both Korsakoff and non-Korsakoff amnesics showed increasing levels of true recognition across trials. However, control subjects exhibited decreasing levels of false recognition across trials, whereas Korsakoff amnesic patients showed increases across trials and non-Korsakoff amnesics showed a fluctuating pattern. Consideration of signal detection analyses and differences between the two types of amnesic patients provides insight into how mechanisms of veridical episodic memory can be used to suppress false recognition.

Aged↗

PubMed1997

Dissociations between familiarity processes in explicit recognition and implicit perceptual memory.

Dual-process theories of recognition posit that a perceptual familiarity process contributes to both explicit recognition and implicit perceptual memory. This putative single familiarity process has been indexed by inclusion-exclusion, remember-know, and repetition priming measures. The present studies examined whether these measures identify a common familiarity process. Familiarity-based explicit recognition (as indexed by the inclusion-exclusion and the independence remember-know procedures) increased with conceptual processing. In contrast, implicit word-identification priming and familiarity-based word-stem completion (as indexed by inclusion-exclusion) increased with study-test perceptual similarity. These dissociations indicate that familiarity-based explicit recognition may be more sensitive to conceptual than to perceptual processing and is functionally distinct from the perceptual familiarity process mediating implicit perceptual memory.

Adult↗

PubMed1997

Illusory memories in amnesic patients: conceptual and perceptual false recognition.

Little is known about the neuropsychology of false recognition. D.L. Schacter, M. Verfaellie, and D. Pradere (1996) induced false recognition in amnesic patients and normal controls by exposing them to numerous semantic associates of a nonstudied word and found that amnesics showed significantly reduced levels of false recognition. To determine whether this outcome is specific to the semantic domain, the authors examined false recognition after exposure to lists of conceptually and perceptually related words. In the control group, conceptual false recognition was associated with "remember" responses and perceptual false recognition was associated with "know" responses. Amnesic patients showed reduced levels of conceptual and perceptual false recognition that were approximately equally divided between remember and know responses.

Age Factors↗

PubMed1997

The neural basis of aware and unaware forms of memory.

Information regarding the nature of phenomenal awareness in memory comes from a direct comparison of explicit and implicit memory tasks. Explicit memory tasks require conscious awareness of a prior episode, whereas implicit memory tasks do not. This paper reviews evidence regarding the neural basis of aware and unaware forms of memory as obtained from patient studies and functional neuroimaging work. These studies suggest the existence of a memory system centered in the medial temporal and frontal lobes that is dedicated to the storage and retrieval of episodes and several neocortical memory systems that are dedicated to the processing and representation of perceptual and semantic information. Different hypotheses are discussed as to how the phenomenal awareness that accompanies episodic memories may arise within the hippocampal-frontal memory system. These views have in common the notion that various forms of information need to be bound together to be retrievable as an aware memory, and that the hippocampus is critical to this binding function.

Awareness↗

PubMed1997

Repetition priming in an auditory lexical decision task: effects of lexical status.

The effect of lexical status on the time course of repetition priming was examined in an auditory lexical decision task. Words and nonwords were repeated at lags of 0, 1, 4, and 8 items (Experiment 1A) and 0, 2, 4, and 8 items (Experiment 1B). The pattern of repetition effects differed for words and nonwords in that repetition priming for nonwords at lag 0 was significantly greater than for words. The magnitude of this effect decreased when one or more items intervened. A second experiment, replicating Experiment 1A with visual presentation, clarified that the greater magnitude of repetition priming for nonwords at lag 0 is unique to the auditory modality. This finding suggests that in the course of forming a stable perceptual representation, the details of the acoustic/phonological information of an auditory stimulus are more readily available for nonwords than for words. The capacity to carry this phonological information is limited, however, and can only be maintained until another stimulus is encountered.

Adult↗

PubMed1996

Assessment of neglect reveals dissociable behavioral but not neuroanatomical subtypes.

In the current study, we investigated whether standard assessment techniques of visuospatial neglect are sensitive to detecting dissociable subtypes. We administered a battery of tasks commonly used to detect the presence of visuospatial neglect to 120 patients with unilateral right hemisphere infarcts and, in most cases, performed a systematic analysis of their lesions to quantify and localize brain damage. Using a factor analysis, we discovered seven relatively independent constructs, three of which were specifically related to the presence of left hemispatial neglect: Left Attentional Processing, Line Bisection, and Word Reading. Impairments in two of these factors, Left Attentional Processing and Line Bisection, occurred together in most cases but also occurred independently in 38 cases. There were no cases in whom Word Reading was present without concomitant deficits in one or the other two factors. These three factors could not be distinguished neuroanatomically; that is, lesions were equally likely in the temporal/parietal cortex, dorsolateral frontal cortex, or in deep frontal structures. These data confirm the notion that hemispatial neglect is a complex and multifaceted disorder composed of cognitively independent processes. These processes, however, cannot be dissociated neuroanatomically based on currently available assessment techniques.

Adult↗

PubMed1996

Spatial location memory in amnesia: binding item and location information under incidental and intentional encoding conditions.

Items located within an array were presented to alcoholic Korsakoff and nonalcoholic mixed-etiology amnesics and to alcoholic and normal controls. Recognition memory for the locations of items was tested after incidental and intentional encoding. When equated on item recognition, neither Korsakoff amnesics nor alcoholic controls benefited from intentional, relative to incidental, encoding instructions. Furthermore, Korsakoff amnesics showed neither disproportionately impaired incidental nor intentional location recognition memory relative to alcoholic controls. In contrast, mixed-etiology amnesics profited significantly from intentional location acquisition relative to incidental instructions, and were impaired somewhat in incidental, but not intentional, location memory relative to normal controls. We discuss these data in relation to Mayes' (1992) contextual memory deficit hypothesis and Hirst's (1982) automatic encoding deficit account, and propose an alternative framework in which the location memory deficit observed in mixed-etiology amnesics is interpreted as a disruption to the ability to bind item and location information.

Alcohol Amnestic Disorder↗

PubMed1996

Verbal memory function in mild aphasia.

Verbal material may be processed by semantic and phonologic systems. Damage to these language systems may also impair memory. We classified 16 mildly aphasic patients according to phonologic and lexicosemantic abilities, tested them on a variety of short- and long-term memory measures, and correlated behavioral deficits with lesion location. Aphasia impaired both short- and long-term memory. Phonologic impairment affected only digit span performance. Lexicosemantic deficits impaired self-organized encoding of word lists. Memory impairment was not associated with specific lesion locations. Persistent verbal-memory impairments accompanying even mild residual aphasia may be responsible for much of the difficulty mildly aphasic patients experience returning to vocational, academic, and social life. Co-occurrence of these deficits probably reflects their underlying dependence on similar processing systems.

Adult↗

PubMed1995

Knowledge of New English vocabulary in amnesia: an examination of premorbidly acquired semantic memory.

To assess if amnesics have intact remote memory for general semantic information, we examined memory for vocabulary words with known dates of entry into the language between 1955 and 1989. Amnesics of mixed etiology with acute onset performed normally on both a recall and a recognition task. Korsakoff patients, in contrast, were impaired on both tasks and demonstrated a gradient such that their knowledge of words acquired during more recent time periods was worse than that of words acquired during more remote time periods. The improvement in performance associated with recognition testing was larger for Korsakoff patients than for control subjects and correlated significantly with a composite measure of frontal dysfunction. These findings suggest a deficit in the controlled search and retrieval of semantic information in Korsakoff patients. The implications of the differential performance of Korsakoff and mixed etiology amnesics for explanations of temporally graded retrograde amnesia are discussed.

Adult↗

PubMed1995

Comparison of figural intrusion errors in three amnesic subgroups.

To examine the contribution of memory deficits and executive dysfunction to the production of prior-item intrusion errors, Korsakoff, mesial temporal amnesic, and anterior communicating artery aneurysm (ACoA) patients' performance on the Visual Reproduction subtest of the Wechsler Memory Scale-Revised (WMS-R) was assessed. The Korsakoff patients were matched to the mesial temporal group in terms of severity of amnesia, while the ACoA group, which was less severely amnesic, was matched to the Korsakoff group in their performance on executive tests. Results indicated that at immediate recall, Korsakoff patients made significantly more intrusions than mesial temporal and ACoA patients. Conversely, after a delay, ACoA patients tended to make more intrusions than the other groups. Findings suggest that intrusions are due to a combination of deficient memory and executive dysfunction. A further comparison of a subgroup of ACoA patients matched to the Korsakoff patients in terms of severity of amnesia, however, revealed differences in the pattern of intrusions of these two groups, suggesting that different mechanisms may underlie Korsakoff and ACoA patients' susceptibility to interference.

Adult↗

PubMed1995

Amnesia following traumatic bilateral fornix transection.

There is controversy regarding the effect of isolated fornix damage on human memory. We report a patient who suffered a traumatic penetrating head injury that resulted in a significant and persistent anterograde amnesia. CT revealed a lesion that involved the region of the proximal, posterior portion of both fornices without evidence of damage to other hippocampal pathways or to other structures known to be critical for memory, such as the hippocampus, thalamus, or basal forebrain. The unique location of the lesion in this patient provides evidence supporting the role of isolated fornix lesions in amnesia.

Adult↗

PubMed1994

Acquisition of generic memory in amnesia.

Amnesic patients' ability to acquire generic, semantic information was assessed relative to their own level of episodic memory. Patients studied a list of words in which some items were presented twice and others once. Upon each presentation, the words were tagged episodically by presenting them in a unique color. Recall of the colors in which words were presented suggested that individual presentations of repeated items were less likely to be recalled than presentations of nonrepeated items; however, actual recall of repeated items exceeded that of nonrepeated items. This outcome demonstrated that amnesics can recall some items generically without recalling either of their individual presentations. However, amnesics' recall of twice-presented items remained far below that of the control group, even when their recall of once-presented items was matched by testing the control group after a delay. This finding suggests that amnesic patients can acquire new generic knowledge but do so much less efficiently than do normal individuals. Furthermore, this deficit occurs independently of the amnesics' episodic memory impairments, reflecting instead a disruption in semantic learning per se.

Adult↗

PubMed1994

Lateralization of memory for the visual attributes of objects: evidence from the posterior cerebral artery amobarbital test.

We used the posterior cerebral artery amobarbital test to examine how each temporal lobe mediates memory for objects. Temporal lobectomy candidates were presented with four objects while one hemisphere was anesthetized. We assessed recall and recognition following recovery from the drug. Verbal recall was significantly better following object presentation to the left hemisphere when the left hemisphere was not the seizure focus. Recognition memory, tested with two identical objects, two objects that shared the same name but had different physical characteristics, and two foils, was superior following object presentation to the right hemisphere. Only the right hemisphere could discriminate identical objects from same-name foils. These data confirm that the left temporal lobe has an advantage in encoding the verbal representation of an object and suggest that the right temporal lobe is critical for memory of specific visual attributes of objects.

Adult↗

PubMed1993

Episodic effects on picture identification for alcoholic Korsakoff patients.

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

Aged↗