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Biomedical subjects

M Moscovitch

Publications and source records attributed to M Moscovitch.

122 records · Page 7Linked to original sources
PubMed1981

The effect of cuing on release from proactive interference in korsakoff amnesic patients.

Korsakoff amnesic and alcoholic control patients were asked to recall successive lists of nine nouns of the same category. The expected progressive decrease in recall was reversed by a category shift on the fifth list for controls but not for amnesics. A context shift on the fifth list (changed color of words and background) led to improved performance by amnesics but not by controls. However, amnesics did show "release from proactive interference" at category shift if it was the second shift in a sequence (on trial nine) or if they were told to expect the shift. These findings relate amnesics' known vulnerability to proactive interference to an impaired use of available cues to segregate new from old material--unless the cues are made additionally salient. This difficulty could operate both during learning and at retrieval.

Alcohol Amnestic Disorder↗
PubMed1980

Material-specific perceptual interference for visual words and faces: implications for models of capacity limitations, attention, and laterality.

Four experiments were conducted to test the hypothesis that perceptual interference effects would be greatest among items that are processed by the same hemisphere than among items processed by different hemispheres. Recognition of two peripheral faces, flanked on either side of a central item that also had to be identified, was worse when the item was a face than when the item was a word. The opposite results were obtained for peripheral word identification by naming (Experiment 1). Identical results were obtained when a nonsense form was substituted for the central face (Experiment 2). Since unfamiliar faces and nonsense forms are processed primarily by the right hemisphere and words are processed by the left, the results are consistent with the hypothesis. The interference effect was the same even when the central nonsense shape was identified by naming, suggesting that the locus of the effect is not at response selection (Experiment 3). Ignoring the central item only reduces the interference effects but does not eliminate it (Experiment 4). Although in general words were perceived better in the right visual field, and faces were perceived better in the left, small fluctuations in the magnitude but not in the direction of perceptual asymmetries were sometimes noted with changes in the central item. The fluctuations were usually opposite to those predicted by attentional models of perceptual asymmetries.

Attention↗
PubMed1979

Differences in neural organization between individuals with inverted and noninverted handwriting postures.

Levy's hypothesis that movements of the distal musculature are controlled by ipsilateral motor projections in subjects with inverted writing posture was tested in a reaction-time experiment with lateralized auditory, tactual, and visual stimulation. Subjects were required to depress a response key with the left or right index finger when they detected a stimulus in either the left or right sensory field. Writers with noninverted posture responded quickest to stimuli on the same side as the responding hand in all modalities tested, whereas inverted writers showed this pattern only in auditory and tactual modalities. In the visual modality, they responded quickest to stimuli on the side opposite the responding hand. Because Levy's hypothesis predicts the latter effect in all modalities for inverted writers, it is challenged by our results, which suggest that inverted writers may be characterized by anomalous visual or visuomotor organization.

Behavior↗
PubMed1976

Early versus late stages of processing and their relation to functional hemispheric asymmetries in face recognition.

To determine whether perceptual asymmetries for faces occur at early or late stages of stimulus analysis, subjects compared the members of a pair of faces which appeared in the right or left visual field, either to each other or to a previously presented sample. The first two experiments established that manual reaction times were consistently shorter to left-field presentation only when test faces were compared for identity to a memorized sample (Experiment 2), but not when they were compared to each other (Experiment 1). By varying the interstimulus interval between the sample and test (Experiment 3), it was found that a consistent left-field superiority was absent for at least the first 50 msec following sample offset, suggesting that during that time both hemispheres have access to a short-lived, visual trace that represents the results of the early, precategorical processing stages. Beyond 100 msec, or earlier if the trace is degraded by a masking field (Experiment 4), a left-field advantage is observed. Experiment 5 showed that higher order comparisons between photographs and caricatures yield a left-field superiority even in a memory-free situation. Together, the results indicate only higher order processes, such as are needed to maintain a relatively permanent memory representation or to compare caricatures with photographs, require the specialized functions peculiar to the right hemisphere. Lower-order, precategorical processes seem to be common to both hemispheres.

Cognition↗
PubMedDate not supplied

Hippocampal contributions to cortical plasticity.

The hippocampal complex and neocortex are both integrally important in memory function, in particular as regards memory for episodes and knowledge about the world that is derived from them. It is traditionally assumed that the role of the hippocampus is time-limited, after which retrieval of episodic memory depends only upon neocortical stores. A number of lines of evidence indicate that this traditional view is incorrect. We propose that the hippocampal complex is always necessary for retrieval of episodes and their contextual frame, and that hippocampal-neocortical interactions contribute instead to the extraction of semantic information to be stored in the neocortex.

Animals↗
PubMedDate not supplied

Functional interactions between the medial temporal lobes and posterior neocortex related to episodic memory retrieval.

We applied structural equation modeling to positron emission tomography data in humans to examine functional interactions between the right medial temporal lobe (MTL) and selected right neocortical regions in relation to visual recognition memory. Using a priori knowledge about anatomical connections between these regions as a guiding constraint, we modeled the pattern of interactions [i.e. covariances in regional cerebral blood flow (rCBF)] associated with episodic memory retrieval of spatial location and compared it with the pattern for retrieval of object identity. We also compared these patterns with those associated with perceptual matching of spatial location and object identity. Although displaying no difference in average rCBF across tasks, the right MTL showed domain-specific qualitative differences in interactions with posterior dorsal (parieto-occipital sulcus, supramarginal gyrus) and ventral regions (fusiform gyrus, superior temporal sulcus) but not with a prefrontal region. MTL interactions involving dorsal regions were positive in the spatial retrieval task but negative for object retrieval. Interactions involving ventral regions showed the reverse pattern. No comparable changes were observed during perceptual matching. Using control models, we demonstrated the neuroanatomical specificity of these results. Our results provide support for the notion that the nature of interactions between the MTL and posterior neocortex depends on the domain of information to-be-recovered.

Brain Mapping↗