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J D Gabrieli

Publications and source records attributed to J D Gabrieli.

At least 91 records · Page 5Linked to original sources
PubMed1997

Word-stem completion priming for perceptually and conceptually encoded words in patients with Alzheimer's disease.

This study examined whether the frequently reported word-stem completion priming deficit of Alzheimer's disease (AD) patients could be characterized as either a semantic encoding deficit or a conceptual priming deficit. AD patients and normal elderly control subjects studied words in two conditions: (1) reading visually presented words aloud, which maximizes perceptual encoding of seen words, and (2) generating words aloud from definitions, which maximizes conceptual encoding of words not seen but retrieved on the basis of semantic context. Recognition accuracy was greater for words that were generated at study, and word-stem completion priming was greater for words that were read at study. For the AD patients, recognition accuracy was impaired and word-stem completion priming was intact for words encoded in both conditions. The findings are discussed in terms of discrepant results about word-stem completion priming in AD.

Aged↗
PubMed1997

Preserved verb generation priming in global amnesia.

In the verb generation task, participants are presented with nouns and generate for each one an appropriate verb. Raichle et al. (Cerebral Cortex, 1994, 4, 8-26) found that when participants generated verbs to repeated nouns, generation latencies were reduced and different patterns of brain activation were present. In order to examine whether verb generation priming is dependent or independent of declarative memory, verb generation priming was compared between 13 amnesic (seven with alcoholic Korsakoff's syndrome, six with other etiologies) and 19 control participants (10 with a history of alcoholism). Both amnesic and control participants became faster across blocks on repeated nouns and slowed when novel nouns were introduced. Priming was verb specific for both groups: it was equivalent whether generated to a repeated or a novel noun. Verb generation priming, therefore, can occur independently of declarative memory.

Adult↗
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

Evidence for multiple mechanisms of conceptual priming on implicit memory tests.

The authors examined effects of encoding manipulations on 4 conceptual-implicit memory tasks: word-cued association, category-cued association, category verification, and abstract/concrete classification. Study-phase conceptual elaboration enhanced priming for word-cued association with weakly associated words (Experiment 3), and for category-cued association with high- and low-dominance exemplars (Experiments 4 and 5), but did not enhance priming for word-cued association with strongly associated words (Experiments 1 and 2), for category verification with high- and low-dominance exemplars (Experiment 5), or for abstract/concrete classification (Experiment 7). Forms of priming that were unaffected by conceptual elaboration were not mediated by perceptual processes because they were unaffected by study-test modality changes (Experiments 6 and 8). The dissociative effects of conceptual elaboration on conceptual-implicit tasks suggest that at least 2 dissociable mechanisms mediate conceptual priming.

Humans↗
PubMed1997

Impaired trace eyeblink conditioning in bilateral, medial-temporal lobe amnesia.

Trace eyeblink classical conditioning was assessed in patients with bilateral medial-temporal amnesia and matched control participants who had previously shown equivalent delay eyeblink conditioning (J. D. E. Gabrieli et al., 1995). The silent trace interval varied for durations of 500, 750, or 1,000 ms in successive sessions separated by at least 2 weeks; extinction trials followed each session. Patients with amnesia produced significantly fewer conditioned responses (CRs) than did control participants at all trace intervals. Both groups produced fewer CRs as the trace interval lengthened. Thus, the temporal lobe memory system in humans makes an essential contribution to normal acquisition in trace, but not delay, classical eyeblink conditioning.

Adult↗
PubMed1997

Sources of priming in text rereading: intact implicit memory for new associations in older adults and in patients with Alzheimer's disease.

The contributions of text meaning, new between-word associations, and single-word repetition to priming in text rereading in younger and older adults, and in patients with Alzheimer's disease. (AD), were assessed in Experiment 1. Explicit recognition memory for text was also assessed. Equivalent single-word and between-word priming was observed for all groups, even though patients with AD showed impaired explicit memory for individual words in the text. The contribution of generalized reading task skill to priming in meaningless text rereading in younger adults was assessed in Experiment 2. Generalized reading task skill was also found to contribute to priming. These results reveal 3 mechanisms of priming: new between-word associations for meaningful and meaningless text, individual word repetition for meaningless text, and general task or skill factors for meaningless text. All priming mechanisms appear to be intact in older adults and in patients with AD.

Adult↗
PubMed1997

Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks.

Adult↗
PubMed1997

Intact mirror-tracing and impaired rotary-pursuit skill learning in patients with Huntington's disease: evidence for dissociable memory systems in skill learning.

Skill learning in early-stage Huntington's disease (HD) patients was compared with that of normal controls on 2 perceptual-motor tasks, rotary pursuit and mirror tracing. HD patients demonstrated a dissociation between impaired rotary-pursuit and intact mirror-tracing skill learning. These results suggest that different forms of perceptual-motor skill learning are mediated by separable neural circuits. A striatal memory system may be essential for sequence or open-loop skill learning but not for skills that involve the closed-loop learning of novel visual-response mappings. It is hypothesized that working memory deficits in HD resulting from frontostriatal damage may account broadly for intact and impaired long-term learning and memory in HD patients.

Adult↗
PubMed1997

Functional anatomy of long-term memory.

Memory in the brain is organized into multiple memory systems that perform different memory functions and have different neurologic substrates. Declarative memory involves conscious memory for facts and events. The medial temporal lobe and structures in the diencephalon are essential in the establishment of new declarative memories, and these memory traces are finally stored in domain-specific regions of the cerebral cortex. The frontal lobe and basal ganglia are important in some forms of declarative memory that require reasoning about the contents of memory. Nondeclarative forms of memory (including skill learning, repetition priming, and classical conditioning) do not involve conscious recollection and are measured through changes in the way in which tasks are performed. These forms of memory rely upon the cerebral cortex, basal ganglia, and cerebellum.

Amygdala↗
PubMed1996

Memory systems analyses of mnemonic disorders in aging and age-related diseases.

The effects upon memory of normal aging and two age-related neurodegenerative diseases, Alzheimer disease (AD) and Parkinson disease, are analyzed in terms of memory systems, specific neural networks that mediate specific mnemonic processes. An occipital memory system mediating implicit visual-perceptual memory appears to be unaffected by aging or AD. A frontal system that may mediate implicit conceptual memory is affected by AD but not by normal aging. Another frontal system that mediates aspects of working and strategic memory is affected by Parkinson disease and, to a lesser extent, by aging. The aging effect appears to occur during all ages of the adult life-span. Finally, a medial-temporal system that mediates declarative memory is affected by the late onset of AD. Studies of intact and impaired memory in age-related diseases suggest that normal aging has markedly different effects upon different memory systems.

Adult↗
PubMed1996

Functional mapping of human learning: a positron emission tomography activation study of eyeblink conditioning.

Regional cerebral blood flow (rCBF) was measured using positron emission tomography during eyeblink conditioning in young adults. Subjects were scanned in three experimental conditions: delay conditioning, in which binaural tones preceded air puffs to the right eye by 400 msec; pseudoconditioning, in which presentations of tone and air puff stimuli were not correlated in time; and fixation rest, which served as a baseline control. Compared with fixation, pseudoconditioning produced rCBF increases in frontal and temporal cortex, basal ganglia, left hippocampal formation, and pons. Learning-specific activations were observed in conditioning as compared with pseudoconditioning in bilateral frontal cortex, left thalamus, right medial hippocampal formation, left lingual gyrus, pons, and bilateral cerebellum; decreases in rCBF were observed for bilateral temporal cortex, and in the right hemisphere in putamen, cerebellum, and the lateral aspect of hippocampal formation. Blood flow increased as the level of learning increased in the left hemisphere in caudate, hippocampal formation, fusiform gyrus, and cerebellum, and in right temporal cortex and pons. In contrast, activation in left frontal cortex decreased as learning increased. These functional imaging results implicate many of the same structures identified by previous lesion and recording studies of eyeblink conditioning in animals and humans and suggest that the same brain regions in animals and humans mediate multiple forms of associative learning that give meaning to a previously neutral stimulus.

Adult↗
PubMed1995

Normal perceptual priming of orthographically illegal nonwords in amnesia.

This study examined priming in perceptual identification of orthographically illegal nonwords in control subjects and patients with global amnesia. Subjects studied a list of orthographically illegal nonwords and then performed a perceptual identification task in which half of the stimuli were from the prior study list and half were new (unstudied) stimuli. Priming was reflected in enhanced identification accuracy of studied compared to unstudied nonwords. Amnesic patients showed significant and normal priming despite impaired recognition memory performance. Because the experimental stimuli were dissimilar to real words in terms of orthography and phonology, it is unlikely that this priming effect was mediated by activation of pre-existing representations of orthographically or phonologically similar words, morphemes, or syllables. These results demonstrate that intact perceptual priming in amnesia is not limited to stimuli that are premorbidly represented in long-term knowledge, nor to novel stimuli that conform to the rules that characterize familiar items. Further, because the experimental stimuli comprised novel letter assemblies, the results suggest that amnesic patients can show normal priming for new perceptual associations. These findings demonstrate that processes spared in amnesia can support the creation and subsequent retrieval of novel stimulus representations.

Adult↗
PubMed1995

Perceptual and nonperceptual components of implicit memory for pictures.

The transfer appropriate processing (TAP) framework posits that in data-driven tasks, such as picture naming (PN) or picture perceptual identification, repetition priming is greater when perceptual processes engaged at study are recapitulated at test. Thus, priming with pictures is greater after study-phase exposure to pictures than to words (picture names). A. S. Brown, D. R. Neblett, T. C. Jones, and D. B. Mitchell (1991) reported that a pure-list format eliminated perceptual priming: Participants who saw either pictures or words in a study phase showed equal priming in a PN task. In the present study, participants showed greater priming after exposure to pure lists of pictures than to pure lists of words in 3 PN and 1 picture perceptual identification experiments. Thus, perceptual priming occurred in 4 pure-list picture priming tasks, as predicted by the TAP framework. Priming also was found after exposure to words. In PN and picture perceptual identification tasks, implicit memory for pictures includes perceptual and nonperceptual components.

Form Perception↗
PubMed1995

Intact delay-eyeblink classical conditioning in amnesia.

The status of classical conditioning in human amnesia was examined by comparing conditioning of the eyeblink response (the unconditional response) to a tone conditioned stimulus (CS) paired with an airpuff unconditioned stimulus (US) in the delay paradigm between 7 amnesic and 7 age- and education-matched normal control participants. Amnesic patients exhibited normal baseline performance in pseudoconditioning and normal acquisition and extinction of conditioned responses in terms of the number, latency, and magnitude of eyeblinks. These results indicate that in humans, as in rabbits, brain structures critical for declarative memory are not essential for the acquisition of elementary CS-US associations.

Adult↗
PubMed1995

Double dissociation of memory capacities after bilateral occipital-lobe or medial temporal-lobe lesions.

Memory for recently encountered information can be reflected in conscious recall and recognition of that material, or in facilitated reprocessing of that material, an effect known as repetition priming. Repetition priming may be perceptual (form-based) or conceptual (meaning-based). A patient with bilateral occipital-lobe lesions (L.H.) and a patient with bilateral medial-temporal lobe lesions (H.M.) showed a double dissociation between visuoperceptual priming (impaired in L.H. and intact in H.M.) and visual recognition memory (intact in L.H. and impaired in H.M.). L.H. showed intact conceptual priming for visually presented words; his pattern of impaired visuoperceptual priming and intact conceptual priming is the reverse dissociation to that observed in prior studies of patients with Alzheimer's disease, in whom occipital cortices are relatively spared. These double dissociations suggest that a memory system localized to the occipital lobe mediates visuoperceptual priming effects, and that this system is independent of neural circuits mediating conceptual priming effects, and independent of the limbic-diencephalic system supporting conscious recognition of recently encountered information.

Adult↗
PubMed1995

Functional MRI measurement of language lateralization in Wada-tested patients.

In this study the use of functional MRI (fMRI) for measuring language lateralization non-invasively was examined. The subjects were seven patients with histories of temporal lobe epilepsy who had undergone Wada testing for pre-surgical evaluation. Four patients were left-hemisphere-dominant and three were right-hemisphere-dominant for language. They received fMRI scans while they made semantic or perceptual judgments about visually presented words. Regions of the inferior frontal gyrus (pars triangularis and pars orbitalis) and neighbouring orbital cortex, corresponding to portions of Brodmann areas 45, 46 and 47, exhibited significant increases in activation during semantic relative to perceptual judgments. Lateralization of the increases in activation were consistent with the Wada test assessments of hemispheric language dominance in each of the seven patients. These results suggest that, in addition to providing a tool for investigating human cognitive processes, fMRI has significant clinical potential as a non-invasive measure of language lateralization.

Adult↗
PubMed1995

Impaired delay eyeblink conditioning in amnesic Korsakoff's patients and recovered alcoholics.

The performance of amnesic Korsakoff patients in delay eyeblink classical conditioning was compared with that of recovered chronic alcoholic subjects and healthy normal control subjects. Normal control subjects exhibited acquisition of conditioned responses (CRs) to a previously neutral, conditioned tone stimulus (CS) following repeated pairings with an unconditioned air-puff stimulus, and demonstrated extinction of CRs when the CS was subsequently presented alone. Both amnesic Korsakoff patients and recovered chronic alcoholic subjects demonstrated an impairment in their ability to acquire CRs. These results indicate that the preservation of delay eyeblink conditioning in amnesia must depend on the underlying neuropathology of the amnesic syndrome. It is known that patients with amnesia caused by medial temporal lobe pathology have preserved conditioning. We have now demonstrated that patients with amnesia caused by Korsakoff's syndrome, as well as recovered chronic alcoholic subjects, have impaired conditioning. This impairment is most likely caused by cerebellar deterioration resulting from years of alcohol abuse.

Aged↗