Acquisition and long-term retention of a gross motor skill in Alzheimer's disease patients under constant and varied practice conditions.

This study examined the acquisition and long-term retention of a gross motor skill, namely, tossing, in 23 moderately to severely demented Alzheimer's disease (AD) patients and 22 health older adults. To identify optimal learning strategies, subjects received 10 weeks of training under either constant or variable practice conditions. Accuracy at the tossing task was assessed immediately, one week, and one month following training. AD patients given constant practice were able to learn and retain the tossing task as well as healthy adults. Although controls performed equally well in both conditions, AD patients showed significantly less improvement when practiced at various distances from the target. By the one-month post-test, these patients had lost any minimal gains achieved through practice. In comparison, AD patients receiving constant practice showed essentially no forgetting across post-tests. The inability to benefit from varied practice suggests that AD patients may have difficulty accessing and/or forming motor schemas.

Vision in dementia: contrast effects.

Contrast sensitivity has been shown to be affected in Alzheimer's disease (Ad). We investigated low contrast acuity and contrast sensitivity using clinical test charts in this patient population. Additionally, we tested patients with vascular dementia (vd) and mixed dementia (md), (Alzheimer' with vascular dementia). Contrast sensitivity was assessed using the Vistech VCTS 6500 test chart. Low contrast acuity was measured using the Regan charts at four contrast levels (96%, 50%, 25% and 11%). The patient population consisted of 19 Ad patients, 9 vd patients and 10 md patients. Reduction in acuity was found with contrast level in all cases. Regression lines were fit to the data and statistical analysis was performed. We did not find a statistically significant difference between the Ad and vd or md groups. We did, however, find a difference between the vd and md groups. We did find reduction in contrast sensitivity at all spatial frequencies when compared to the elderly normal. Correspondingly, we found a significant difference in acuity when compared with normal data at the four contrast levels tested. Acuity is reduced with contrast in all patient groups. Our contrast sensitivity results are similar to those reported in the literature. This study points out the importance of using simple clinical test charts and further underscores the idea that there is a primary visual deficit in Ad.

The elusive character of agrammatism.

Traditionally, agrammatism was viewed as a restricted disorder of speech production which was associated with Broca's aphasia. This view has been replaced by a more complex picture which involves a range of linguistic impairments in both language production and comprehension. These disorders have been variously characterized as deficits, in the representation of linguistic structures and deficits in the on-line computation of sentence structures and their interpretations. A variety of analyses of production and comprehension in agrammatism, invoking both representational and computational analyses, are reviewed. Each has inadequacies, but, at the same time, it is argued that each also advances the understanding of agrammatism.

Postaccess processes in the open vs. closed class distinction.

We present the results of two auditory lexical decision experiments in which we attempted to replicate findings originally presented in Bradley (1978, Computational distinctions of vocabulary type, Ph.D. dissertation, MIT). The results obtained by Bradley were used as evidence for a processing distinction between the open and the closed class vocabularies; this distinction then used as part of an explanation for agrammatism in the comprehension and production of Broca's aphasics. In our first experiment we failed to replicate Bradley's result of frequency insensitivity in the closed class. Our second experiment, however, replicates Bradley's finding that closed class based nonwords (e.g., thanage) fail to induce interference effects in nonword decisions. We argue that our results, together with the various other reported failures to replicate Bradley's frequency insensitivity result, indicate that the open and closed classes may play distinct roles in postaccess phenomena involving the processing of morphological information but that such studies cannot address the question of whether the open vs. closed class distinction plays a role in syntactic processing.

Memory for action events in Alzheimer-type dementia: further evidence of an encoding failure.

The purpose of the present research was to examine the nature of the encoding problem in patients with dementia of the Alzheimer type (DAT) using a nonstrategic memory task, namely the recall of action events or subject-performed tasks (SPTs). The first experiment investigated the retention of SPTs and the verbal descriptions of action events in patients with mild-to-moderate DAT, young, and old adults. While the healthy older adults showed significantly higher recall for SPTs than for verbal descriptions, the DAT patients failed to exhibit this effect. A follow-up study replicated this same pattern using SPTs and tasks performed by the experimenter. As the multimodal and contextually rich encoding environment present in SPTs had no effect on the patients' retention, this suggests that manipulations designed to enhance encoding in this population will be unsuccessful. The relevance of the results to (1) memory compensation in the aged, and (2) the development of mnemonic training programs for the elderly are discussed.

Memory for internally generated words in Alzheimer-type dementia: breakdown in encoding and semantic memory.

The "generation effect" is a phenomenon in which words that are generated by the subject are remembered better than words which are read. The present experiments examined this effect in patients with mild-to-moderate dementia of the Alzheimer type (DAT), healthy elderly adults, and young adults under a variety of different encoding and retrieval conditions. Experiment 1 employed an intentional learning task with multiple study/test trials using the same list of words. While both the young and elderly adults exhibited higher recall for internally generated words than read words, the DAT patients failed to demonstrate the effect even after repeated exposures to the same stimulus list. Experiment 2 replicated this same pattern of results using an incidental learning paradigm with both recall and recognition tests. Various explanations as to why the DAT patients failed to show the generation effect were discussed with particular emphasis placed on the role of semantic memory and encoding failure.

The preselection effect on the recall facilitation of motor movements in Alzheimer-type dementia.

Two experiments examined the coding and retention of psychomotor information in patients with mild to moderate dementia of the Alzheimer-type (DAT), healthy elderly controls, and young adults. Experiment 1 compared recall accuracy for preselected (subject-defined) and constrained (experimenter-defined) movements under three different retention conditions. Not surprisingly, the DAT patients showed significantly larger reproduction errors than did the controls. In all three groups, however, preselected movements were recalled more accurately than constrained movements. This preselection advantage was replicated in Experiment 2 using a new group of DAT patients with recall being performed under both same- and switch-limb conditions. While the results suggested that DAT patients suffer from both an encoding deficiency and a rapid loss of information from short-term memory, they also indicate that patients are capable of coding meaningful aspects of motor movements. Most importantly, the results suggest that in the motor domain, efforts to enhance encoding can facilitate the recall of DAT patients.

The question of linguistic anomaly in developmental dyslexia.

Recent research findings pointing to an anatomical anomaly in the left hemisphere of dyslexics supports the conjecture that dyslexia involves a central anomaly in structural linguistic capacity. Two preliminary studies were carried out to test this conjecture. One study employed the techniques of grammatical research and the other was a reaction time study. Each study provided distinct evidence of a linguistic anomaly. The grammatical study suggested an anomaly when the assignment of referential relations among nominal elements is restricted on the basis of sentence structure, and the reaction time study provided evidence of an anomaly in the exploitation of grammatical markers.