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J D Gabrieli

Publications and source records attributed to J D Gabrieli.

At least 109 records · Page 6Linked to original sources
PubMed1995

Semantic encoding and retrieval in the left inferior prefrontal cortex: a functional MRI study of task difficulty and process specificity.

Prefrontal cortical function was examined during semantic encoding and repetition priming using functional magnetic resonance imaging (fMRI), a noninvasive technique for localizing regional changes in blood oxygenation, a correlate of neural activity. Words studied in a semantic (deep) encoding condition were better remembered than words studied in both easier and more difficult nonsemantic (shallow) encoding conditions, with difficulty indexed by response time. The left inferior prefrontal cortex (LIPC) (Brodmann's areas 45, 46, 47) showed increased activation during semantic encoding relative to nonsemantic encoding regardless of the relative difficulty of the nonsemantic encoding task. Therefore, LIPC activation appears to be related to semantic encoding and not task difficulty. Semantic encoding decisions are performed faster the second time words are presented. This represents semantic repetition priming, a facilitation in semantic processing for previously encoded words that is not dependent on intentional recollection. The same LIPC area activated during semantic encoding showed decreased activation during repeated semantic encoding relative to initial semantic encoding of the same words. This decrease in activation during repeated encoding was process specific; it occurred when words were semantically reprocessed but not when words were nonsemantically reprocessed. The results were apparent in both individual and averaged functional maps. These findings suggest that the LIPC is part of a semantic executive system that contributes to the on-line retrieval of semantic information.

Adolescent↗
PubMed1994

Priming in perceptual identification of pseudowords is normal in Alzheimer's disease.

Patients with Alzheimer's disease (AD) have deficits in recall and recognition memory, and show dissociable performance in repetition priming tasks: They exhibit impaired priming in word-completion and word-generation tasks, but normal priming is perceptual identification of words. In order to examine whether AD patients can show normal priming with novel, unfamiliar stimuli, the present study examined their performance in perceptual identification of pseudowords. Despite impaired recognition memory performance, AD patients showed normal priming in perceptual identification of pseudowords. These results extend the boundaries of intact repetition priming in AD, demonstrating that such priming is not limited to stimuli that are pre-morbidly represented in long-term knowledge. Preserved repetition priming in AD may reflect the operation of perceptual processes localized to posterior visual circuits that are relatively spared in AD.

Aged↗
PubMed1994

Dissociations among structural-perceptual, lexical-semantic, and event-fact memory systems in Alzheimer, amnesic, and normal subjects.

Patients with Alzheimer's disease (AD), patients with global amnesia (AMN), and normal control (NC) subjects received tests of recall and recognition, word-completion priming, and incomplete-picture priming. The AD and AMN patients had impaired recall and recognition. The AD patients, but not the AMN patients, had impaired word-completion priming. In contrast, the AD patients had intact incomplete-picture priming, a form of priming shown to be perceptual in normal subjects. These results provide neuropsychological evidence for a dissociation between two components of repetition priming, perceptual priming as measured with identification tasks and nonperceptual priming as measured with generation tasks. Preserved perceptual priming in AD may be mediated by the occipital regions that are relatively spared in AD; compromised nonperceptual priming may be mediated by temporal regions that show dense neuropathological changes early in AD.

Adult↗
PubMed1994

Intact text-specific implicit memory in patients with Alzheimer's disease.

The ability of patients with Alzheimer's disease (AD) to acquire and retain text-specific knowledge was investigated in a re-reading study. Patients and normal control Ss read 2 passages 3 times, each as quickly as possible, and answered recognition memory questions after the 3rd reading of each passage. The AD patients had poor explicit memory as evidenced by impaired recognition memory for the passages. In contrast, normal decreases in the times required for successive readings of each passage for AD patients indicated intact implicit memory for the passages. The absence of facilitation across passages indicated that the re-reading effect was text specific, suggesting that AD patients may retain the ability to form certain kinds of implicit new associations. Alternative accounts of the mechanism underlying text-specific priming, and of the nature of intact and impaired implicit memory in AD, are considered.

Aged↗
PubMed1993

Event-related potential correlates of implicit priming and explicit memory tasks.

The difference between implicit and explicit memory was examined using event-related potentials (ERP). 16 college students read a study list of 100 words (50 high-emotion and 50 low-emotion) from a video monitor. They then performed a perceptual identification (P.I.) task in which they attempted to identify each of a series of 100 words (including 50 from the study list) presented at recognition threshold. Finally, the subjects performed a yes-no recognition task in which they were presented with the other 50 words from the first list and 50 new words (suprathreshold), and they had to identify which ones had been seen in the study list. Subjects were more likely to identify studied than nonstudied words in the perceptual identification task; there was no effect of emotion. In the yes-no recognition task, more high than low-emotion words were responded to correctly for the old words, whereas more low than high-emotion words were responded to correctly for the new words. Data from 11 of the subjects contained enough artifact-free trials for ERP analysis. Analysis revealed that in both the perceptual identification task and the yes-no recognition task, P3 amplitude was larger for old than new words, and emotionality had no effect. Analysis of ERPs in the perceptual identification task averaged according to behavioral response, as well as according to prior study effect showed that P3 amplitude was larger for the studied words than non-studied words, regardless of behavioral response. This effect is electrophysiological evidence that a specific event occurs in the brain in response to the presentation of studied words, whether or not those words are consciously perceived. P3 latency differed as a function of previous study in the yes-no task but not the perceptual identification task.

Adolescent↗
PubMed1993

Intact acquisition and long-term retention of mirror-tracing skill in Alzheimer's disease and in global amnesia.

The ability of patients with Alzheimer's disease (AD) or global amnesia (AMN) to acquire skill for tracing a pattern seen in mirror-reversed view and to retain that skill over 24-h intervals was examined. Both patient groups had poor recall and recognition of their mirror-tracing experience, but they acquired and retained mirror-tracing skill as well as normal control subjects. One AMN patient (H.M.) retained the skill over a year-long interval. Furthermore, the patients transferred their skill normally to an alternate pattern. These results indicate that the memory system underlying mirror-tracing skill learning is separable from medial-temporal structures compromised in AMN and AD and from neocortical areas compromised in AD. Brain regions relatively spared in early AD, such as the basal ganglia or cerebellum, may mediate critical aspects of the learning of novel sensorimotor associations that underlie skilled mirror tracing.

Aged↗
PubMed1993

Disorders of memory in humans.

Memory is composed of dissociable systems that accomplish different forms of learning and that are mediated by distinct neural networks. Knowledge about the psychological nature and neural basis of specific memory systems has come primarily from lesion analysis, but this year functional brain imaging has provided a new source of convergent evidence. Recent findings are reviewed that provide new information about a limbic-diencephalic system critical for learning new declarative information, a temporal lobe system that stores long-term semantic knowledge in a domain-specific fashion, an occipital system that subserves visuoperceptual implicit memory, and a fronto-thalamo-neostriatal system that mediates the executive component of working memory and that plays an important role in some forms of sensorimotor skill learning.

Brain↗
PubMed1992

Neurology of memory.

This review discusses the neurological basis of human memory focusing on brain-behavior relations as revealed in patients with memory disorders due to brain lesions. A few relevant animal studies are also discussed. Recent studies are reviewed that provide new insights into the anatomic, chemical, and psychological organization of memory in health and neurological diseases.

Animals↗
PubMed1991

Evidence for a dissociation between perceptual and conceptual priming in Alzheimer's disease.

The status of perceptual priming and word-completion priming in patients with Alzheimer's disease (AD) was examined. Experiment 1 established the reliability of the perceptual priming measure in normal subjects. In Experiment 2, AD patients showed a normal magnitude of perceptual priming. In Experiment 3, a single group of AD patients showed a normal magnitude of perceptual priming and impaired word-completion priming. Further, word-completion priming, but not perceptual priming, was correlated with verbal fluency performance in AD. These results suggest a dissociation between two components of verbal priming. Perceptual priming may reflect the operation of a structural-perceptual memory system mediated by occipital lobe regions relatively spared in AD. Word-completion priming may reflect the operation of a lexical-semantic memory system mediated by temporoparietal lobe regions compromised in AD.

Adult↗
PubMed1991

Normal McCollough effect in Alzheimer's disease and global amnesia.

The McCollough effect (ME), a long-lasting, pattern-contingent aftereffect in normal human vision, was examined in persons with known deficits in memory. We induced MEs in 11 subjects, 5 patients with various severities of Alzheimer's disease (AD), H.M. (a patient who has global amnesia due to bilateral medial temporal lobectomy and who has been studied for 35 years since his operation), and 5 control subjects. H.M. and the AD patients showed MEs of strength and duration comparable to those of the control subjects. These results demonstrate a dissociation between learning mechanisms that mediate recall and recognition versus mechanisms that mediate the ME. Furthermore, knowledge about the sites of neuropathology in H.M. and in AD are consistent with other sources of evidence implicating early visual areas, especially V1, as a critical locus of the ME.

Aged↗
PubMed1990

Intact priming of patterns despite impaired memory.

The priming of patterns was examined in normal control subjects (NCS) and in the amnesic patient H.M., whose anterograde amnesia followed bilateral medial temporal-lobe excision 33 years earlier. Despite H.M.'s impaired recognition of the patterns, he demonstrated a pattern priming effect equivalent in magnitude to that of the NCS. The results demonstrated that intact priming with novel, nonverbal material can occur despite severe amnesia. Pattern priming may reflect adaptive visual processes involved in learning novel perceptual organizations of known visual codes, such as letters, words, shapes, and objects.

Amnesia↗
PubMed1990

Recency and frequency discrimination in the amnesic patient H.M.

Temporal contextual memory and event memory were compared across retention intervals in the patient H.M. who is amnesic following bilateral medial temporal lobectomy. Memory for temporal context was assessed using verbal and nonverbal recency discrimination tasks and a frequency task in which subjects made discriminations between words repeated 1, 3 or 5 times. The tests evaluated event memory under parallel conditions by two-choice content recognition tasks. In both recency and frequency tests, H.M. showed above-chance and often normal temporal contextual memory under conditions of impaired and even chance-level content recognition. These results show that temporal contextual memory does not require intact content recognition and is independent of medial temporal lobe structures. Furthermore, the amnesia of bilateral medial temporal lobe resection does not manifest primary loss of temporal contextual memory.

Amnesia↗
PubMed1989

Evidence for two types of spatial representations: hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments--on/off, left/right, and above/below--faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance--in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)--faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice.

Adult↗
PubMed1989

Different cognitive profiles on standard behavioral tests in Parkinson's disease and Alzheimer's disease.

Patients with Parkinson's disease (PD) displayed a different pattern of cognitive deficit from patients with dementia resulting from Alzheimer's disease (AD). Specifically, PD patients, whether or not impaired on a mental status examination, had deficient Picture Arrangement but normal Vocabulary test scores whereas AD patients were impaired on both measures. Furthermore, PD patients with impaired mental status examination scores showed a deficit in set formation on Picture Arrangement not seen in the AD patients. Finally, when recent memory performance, as measured by the Wechsler Memory Scale, was predicted from an estimated IQ, 71% of PD patients who had normal mental status examination scores were seen to have at least a mild memory impairment.

Aged↗
PubMed1988

The impaired learning of semantic knowledge following bilateral medial temporal-lobe resection.

The integrity of several aspects of semantic memory (including knowledge of the meaning, lexical status, perception, and pronunciation of words and famous names) was examined in H.M., a patient with anterograde amnesia following bilateral medial temporal-lobe excision. Despite normal memory for such semantic knowledge acquired prior to the onset of his amnesia in 1953, H.M. showed a severe deficit in memory for semantic information encountered subsequently. In combination with the previously reported impairments in new learning shown by H.M., the deficits observed here point to an association between semantic and episodic memory, and do not lend support to a distinction between them. The acquisition of semantic and episodic information, therefore, appears to depend upon a common memory system that requires the intact functioning of medial temporal-lobe structures.

Aged↗
PubMed1988

Temporal ordering and short-term memory deficits in Parkinson's disease.

Previous studies of remote memory function have indicated a dissociability between memory for the content and date of past events and suggested selective deficits of dating capacity in Parkinson's disease (PD). The present study examined the hypothesis that poor dating in PD is linked to a specific deficit in temporal contextual memory which also affects new learning. Patients with PD and patients with Alzheimer's disease (AD) were compared in their ability to perform tasks of content recognition and recency discrimination of words presented sequentially. Compared with AD patients, PD patients were disproportionately impaired in recency discrimination relative to content recognition. When performance was analysed as a function of retention interval, AD patients showed impairment in both tasks at all intervals. PD patients, by contrast, showed deficits in content recognition at the short stimulus-test intervals only, possibly reflecting the clinical phenomenon of bradyphrenia. These results suggest that recency discrimination deficits and impaired short-term memory processing are specific cognitive deficits in PD that may be linked to subcortical deafferentation of the frontal lobes.

Alzheimer Disease↗