S. Della Sala

Dementia and working memory

This study explored the hypothesis that patients suffering from dementia of the Alzheimer type (DAT) are particularly impaired in the functioning of the Central Executive component of working memory, and that this will be reflected in the capacity of patients to perform simultaneously two concurrent tasks. DAT patients, age-matched controls and young controls were required to combine performance on a tracking task with each of three concurrent tasks, articulatory suppression, simple reaction time to a tone and auditory digit span. The difficulty of the tracking task and length of digit sequence were both adjusted so as to equate performance across the three groups when the tasks were performed alone. When digit span or concurrent RT were combined with tracking, the deterioration in performance shown by the DAT patients was particularly marked.

A neuropsychological instrument adding to the description of patients with suspected cortical dementia: the Milan overall dementia assessment.

A new, short, neuropsychologically oriented test for dementia assessment--the Milan Overall Dementia Assessment (MODA)--is described. Age and education adjusted norms based on 217 healthy controls are given. A validation study on 312 outpatients suspected of dementia (121 with probable Alzheimers disease) showed that the MODA differentiated patients with cognitive impairment from normal subjects more effectively than did the DSM III-R. The correlation between the MODA and the mini mental state examination was 0.63 in controls and 0.84 in patients with Alzheimers dementia. The MODA test-retest reliability was 0.83. The test proved to be well suited to longitudinal studies.

Impaired contrast sensitivity in diabetic patients with and without retinopathy: a new technique for rapid assessment.

A simple technique is described for assessing the sensitivity of the human visual system to gratings at threshold contrast. The technique has advantages for clinical use in that it is (1) inexpensive, (2) quick to administer, (3) portable, and (4) relatively free from bias. Forty-two diabetic patients and 84 normal controls have been tested. Fifteen diabetic patients (6/20 with retinopathy and 9/22 without) had test scores more than two standard deviations below the norm for age-matched controls.

Dementia, ageing, and the structure of human memory

Abstract The memory performance of patients suffering from senile dementia of the Alzheimer type (SDAT) (N = 29), normal subjects of equivalent age and education (N = 58), and young normal controls (N = 42) was tested using free recall and verbal and nonverbal span. Three measures were derived from the free recall task: primacy based on the first item, secondary memory based on the middle serial positions, and primary memory based on recency and the Waugh-Norman correction factor. The SDAT patients differed from the normal elderly on all free recall and span measures except for primary memory. The elderly were clearly inferior to the young on secondary memory, and were marginally poorer on primary memory and the two span measures. Three possible explanations of this pattern of results are considered, based on the dichotomous modal model of memory, levels of processing, and working memory. It is suggested that the assumption that SDAT patients suffer from a deficit in the central executive component of wor...

Ideomotor apraxia without aphasia and aphasia without apraxia: the anatomical support for a double dissociation.

This study aimed to verify the existence of a double aphasia/apraxia dissociation. Apraxic patients without aphasia and aphasic patients without apraxia were included in a consecutive series of patients with cortical or subcortical CT documented vascular lesions in the left hemisphere. Of 699 patients, 10 were found to be apraxic but not aphasic and 149 aphasic but not apraxic. These findings indicate an aphasia/apraxia double dissociation. This suggests that praxis and language make use of two different, partly overlapping networks.

Spared and impaired cognitive abilities after bilateral frontal damage

We report on a patient (PG) with a severe behavioural disorder following massive bilateral prefrontal damage due to herpetic encephalitis. The lesion involves also the mesial and polar regions of the temporal lobes; the frontal dorso-lateral cortices were relatively spared. The patients inattentiveness and alternating impulsive and apathetic behaviour led to her social alienation. The only self-motivated activities we observed were those initiated to satisfy her enhanced urge to eat and play games. She did not react to surprise stimuli that consistently elicit a reaction of surprise in healthy people. She also presented adynamic aphasia associated with anomia and episodic amnesia. A striking feature of the syndrome was the patients consistent utilization behaviour. Her motor behaviour was marked by constant akathisia. She performed surprisingly well on intelligence, frontal, and visuo-spatial tests. This non-demented patient exhibited a clear dissociation between her relatively spared cognitive abilities and grossly impaired behaviour. In the discussion we explore the extent to which a defect of the supervisory control may be held responsible for the inconsistencies in the patients coping skill performances.

Agnosia for object orientation: implications for theories of object recognition.

Instances in which objects are copied accurately, but are dramatically rotated relative to the original, have been interpreted as evidence for viewpoint-independent accounts of the object recognition process. In two case reports, we demonstrate that patients who show rotation in copying also show difficulties in informing the examiner of the canonical orientation of known objects. In copying rotated versions of familiar objects, one subject showed a tendency to copy them in their canonical upright orientation, and both subjects copied non-representational line drawings with their principal axis vertically aligned, and with the irregular end pointing upwards.

Gait apraxia after bilateral supplementary motor area lesion

Objectives: The study aimed at addressing the issue of the precise nature of gait apraxia and the cerebral dysfunction responsible for it. Methods: The case of a patient, affected by a bilateral infarction limited to a portion of the anterior cerebral artery territory is reported. The patients ability to walk was formally assessed by means of a new standardised test. Results: Due to an anomaly within the anterior cerebral artery system, the patients lesion was centred on the supplementary motor regions of both hemispheres. He presented with clear signs of gait apraxia that could not be accounted for by paresis or other neurological deficits. No signs of any other form of apraxia were detected. Conclusions: The clinical profile of the patient and the analysis of 49 cases from previous literature suggest that gait apraxia should be considered a clinical entity in its own right and lesions to the supplementary motor areas are responsible for it.

The role of clinical neuropsychology in the neurological diagnosis of Alzheimer's disease

SummaryThis survey on the early diagnosis of Alzheimers disease (AD) reinstates the role of clinical neuropsychology in describing the cognitive status of AD and its evolution. The role of clinical neuropsychology is restricted to the clinical diagnosis of organic mental deterioration and its contribution to the diagnosis of AD is separate from that of neurology and neuroradiology. The frequency of a single neuropsychological disturbance in early AD patients is illustrated by our own observations.

Pantomimes are special gestures which rely on working memory

The case of a patient is reported who presented consistently with overt deficits in producing pantomimes in the absence of any other deficits in producing meaningful gestures. This pattern of spared and impaired abilities is difficult to reconcile with the current layout of cognitive models for praxis. This patient also showed clear impairment in a dual-task paradigm, a test taxing the co-ordination aspect of working memory, though performed normally in a series of other neuropsychological measures assessing language, visuo-spatial functions, reasoning function, and executive function. A specific working memory impairment associated with a deficit of pantomiming in the absence of any other disorders in the production of meaningful gestures suggested a way to modify the model to account for the data. Pantomimes are a particular category of gestures, meaningful, yet novel. We posit that by their very nature they call for the intervention of a mechanism to integrate and synthesise perceptual inputs together with information made available from the action semantics (knowledge about objects and functions) and the output lexicon (stored procedural programmes). This processing stage conceived as a temporary workspace where gesture information is actively manipulated, would generate new motor programmes to carry out pantomimes. The model of gesture production is refined to include this workspace.