ABSTRACT
An influential theory of long-term memory, in which new episodic learning is dependent upon the integrity of semantic memory, predicts that a double dissociation between episodic and semantic memory is not possible in new learning. Contrary to this view, we found, in two separate experiments, that patients with impaired semantic memory showed relatively preserved performance on tests of recognition memory if the stimuli were perceptually identical between learning and test. A significant effect of semantic memory was only seen when a perceptual manipulation was introduced in the episodic task. To account for these findings, we propose a revision to current models of long-term memory, in which sensory/perceptual information and semantic memory work in concert to support new learning.
Subject(s)
Alzheimer Disease/psychology , Dementia/psychology , Memory/physiology , Aged , Alzheimer Disease/pathology , Brain/anatomy & histology , Cognition/physiology , Dementia/pathology , Female , Humans , Language , Magnetic Resonance Imaging , Male , Memory, Short-Term/physiology , Middle Aged , Neuropsychological Tests , Space Perception/physiology , Verbal Learning/physiologyABSTRACT
Over 15 months of longitudinal assessment, a patient with semantic dementia, D.M., improved on tests of naming and category fluency for a specific set of items (Experiment 1). The authors attribute this to his home drill with the names of these concepts plus pictures and descriptions of them. In Experiment 2, D.M. produced significantly more exemplars on category fluency for semantic categories that he had been practicing at home than for nonpracticed categories, an effect that cannot be attributed to an inherent difference between the 2 sets because the fluency performance of control participants revealed no significant difference between the 2 sets. In Experiment 3, D.M. rehearsed some of his previously nonpracticed categories daily for a period of 2 weeks: His fluency scores on the experimental categories improved substantially, but they declined once he ceased the daily drill. The results are discussed with respect to current views of long-term memory, particularly new word learning and forgetting, and to current techniques for facilitating word finding in aphasia.
