Gianna Cocchini

Concurrent performance of two memory tasks: Evidence for domain-specific working memory systems

Previous studies of dual-task coordination in working memory have shown a lack of dual-task interference when a verbal memory task is combined with concurrent perceptuomotor tracking. Two experiments are reported in which participants were required to perform pairwise combinations of (1) a verbal memory task, a visual memory task, and perceptuomotor tracking (Experiment 1), and (2) pairwise combinations of the two memory tasks and articulatory suppression (Experiment 2). Tracking resulted in no disruption of the verbal memory preload over and above the impact of a delay in recall and showed only minimal disruption of the retention of the visual memory load. Performing an ongoing verbal memory task had virtually no impact on retention of a visual memory preload or vice versa, indicating that performing two demanding memory tasks results in little mutual interference. Experiment 2 also showed minimal disruption when the two memory tasks were combined, although verbal memory (but not visual memory) was clearly disrupted by articulatory suppression interpolated between presentation and recall. These data suggest that a multiple-component working memory model provides a better account for performance in concurrent immediate memory tasks than do theories that assume a single processing and storage system or a limited-capacity attentional system coupled with activated memory traces.

Is There a Specific Executive Capacity for Dual Task Coordination? Evidence From Alzheimer's Disease

Three experiments compared groups of Alzheimers disease (AD) patients and healthy older and younger participants on visuospatial tracking and digit sequence recall, as single tasks and performed concurrently. In Experiment 1, tasks were performed concurrently with very low demand relative to span. Only the AD patients showed a dual task deficit. In Experiment 2, single task demand was manipulated on each task from below span to above span for each individual. All groups showed the same performance reductions with increasing demand. In Experiment 3, demand on 1 task was constant, whereas demand on the concurrent task was varied. AD patients showed a clear dual task deficit but were no more sensitive than control groups to varying demand. Results suggest an identifiable cognitive resource for dual task coordination within a multiple component working memory system.

What the eyes perceive, the brain ignores: A case of pure unilateral representational neglect

Bisiach and Luzzatti (1978) provided evidence that unilateral spatial neglect is not only a disorder of visual perception, but also can affect mental representations such that patients fail to report the left side of scenes or objects in mental imagery. However in case reports of representational neglect generally it is accompanied by perceptual neglect. We report a rare occurrence of a patient (NL) who presents a persistent unilateral neglect which appears to be limited to visual imagery. The deficit appeared in tasks which require the formation and manipulation of new visuo-spatial representations as well as those which require access to information about familiar scenes. The patient, who had a lesion in the right parietal lobe, showed no evidence of perceptual or personal neglect, although there was some evidence of visual extinction. We argue that the concept of visuo-spatial working memory can provide a framework within which to interpret aspects of the representational form of neglect, whether or not it is accompanied by perceptual neglect.

Working memory and vigilance : Evidence from normal aging and Alzheimer's disease

Both single unit recording and neuroradiological studies suggest that frontal and executive processes are necessary for visual maintenance rehearsal. This observation is linked to the classic vigilance literature by the proposal that vigilance decrement is found when the subject is required to maintain a representation over a brief delay. Vigilance performance was therefore studied in a sample of elderly subjects who were tested over a 40-min period involving perceptual or memory-based tasks which were matched for initial level of performance. There was a significant interaction between task and delay, with only the memory-based task showing decrement. A second study used the same two tasks to investigate vigilance performance in patients suffering from probable Alzheimers Disease. Over a 15-min delay period, an equivalent interaction effect occurred, again indicating substantially greater decrement for the memory-based task. The results are interpreted as consistent with a role for the executive processes of working memory in both visual rehearsal and vigilance performance.

A case of simulated, psychogenic or focal pure retrograde amnesia: did an entire life become unconscious?

A case of pure retrograde amnesia following mild head injury is reported. Neuropsychological, psychodynamic and statistical approaches are employed in an attempt to disentangle the clinical picture presented by the patient. Focal retrograde amnesia, psychogenic retrograde amnesia and simulated amnesia are all taken into account. From a public events questionnaire and an inquiry about famous people, consistency analyses showed that the patient was able implicitly to use information she denied having, but at the same time, made us lower the probability of a simulated amnesia. Moreover, psychodynamic analysis showed that the patients personality structure was compatible with hysterical patterns and we suggest that the patients memory defect may be related to her personality. It seems less likely, though still possible, that the case may be explained in terms of deliberate simulation. In this case we conclude that the classification along the conscious/unconscious dimension seems more informative than the contrast between psychogenic and organic genesis.

Anosognosia for Motor Impairment Following Left Brain Damage

Anosognosia for motor impairment has been linked to lesions of the right hemisphere. However, left hemisphere damaged patients have often been excluded from investigation because of their associated language deficits. In this study we assessed anosognosia for motor disorders in a group of left hemisphere damaged patients using 2 tools that assess the presence of unawareness—a structured interview that is a common method of assessment of anosognosia in clinical settings, and a new tool, the Visual-Analogue Test for Anosognosia for Motor Impairment (VATAm; Della Sala, Cocchini, Beschin, & Cameron, in press). The structured interview relies heavily on language and enquires about general motor ability whereas the VATAm is less dependent on language abilities and enquires about specific motor tasks. Results suggest that the frequency of anosognosia in left brain damaged patients may have been underestimated due to methodological reasons, and that anosognosia for motor impairment can also be associated with lesions of the left hemisphere.

Neglect Without Extinction

A patient, AB, is reported who showed clear signs of neglect but no extinction (N+ E-). Several hypotheses proposed to account for this dissociation were put to the test. The postulated association between motor neglect and extinction did not hold good, nor did the possibility that the N+ E- dissociation may be traced back to the difference in test requirements and therefore observed only in patients with object-centred neglect. Likewise, manipulating the physical features of the stimuli (relative size, exposure time, presentation synchrony) did not elicit extinction. However, when the task demands were modified by asking the patient to perform a further spatial analysis of the stimuli, rather than simply detect them, extinction emerged. Since AB performed well on several neglect tasks requiring parallel processing, while failing all tasks calling for serial processing, the hypothesis is put forward that ABs N+ E- dissociation could be interpreted within the parallel/serial distinction framework.

Chronic anosognosia: a case report and theoretical account

Unawareness of motor disorders (anosognosia) has often been reported after brain lesions, and it has been considered a temporary condition common in the acute and post-acute phases. The presence of anosognosia in a chronic phase (i.e. lasting more than few weeks) is a rare occurrence, thought to be the result of reasoning deficits which prevent patients from performing an adequate check of reality. Although this assumption is widely shared amongst researchers, only a few studies have actually addressed this issue. We report on the case of a patient (NS) who was still showing anosognosia for hemiplegia 1 year after a traumatic brain-head injury, while his reasoning abilities were well preserved. By means of a series of tests and experiments, we evaluated the main theoretical approaches. NSs long-lasting anosognosia is discussed in terms of a combination of clinical manifestations, whereby personal neglect and motor-sensory information play a key role in preventing awareness, whereas memory difficulties in updating pre-existing personal schema may be crucial in maintaining NSs anosognosic status.

Dual task effects of walking when talking in Alzheimer's disease

Previous studies with Alzheimer Disease (AD) patients have suggested that speed and accuracy in walking can be dramatically affected by a simultaneous secondary cognitive task, such as holding a conversation. Two experiments examined the impact on AD patients and age matched elderly controls of cognitive demands while walking. In Experiment 1 walking for AD patients was more affected than it was for the normal elderly by a concurrent cognitive demand. Experiment 2 demonstrated that both groups were equally impaired under dual task conditions when the demands of the cognitive tasks were adjusted for individual levels of ability. We conclude that walking may draw on general executive resources, that walking relies more heavily on these executive resources in the elderly, and on a damaged executive system for AD patients.

VATA-m: Visual-Analogue Test assessing Anosognosia for motor impairment.

There has been a growing interest in anosognosia in both clinical and research domains, yet relatively little attention has been paid to methods for evaluating it. Usually, the presence and severity of anosognosia is assessed by means of structured interviews or questionnaires. Both interviews and questionnaires can provide valuable information, but they rely heavily on self-evaluation and language, and are therefore prone to bias and pose more difficulty in the assessment of aphasic patients. The aim of this study was to develop a new tool, the VATAm (Visual-Analogue Test for Anosognosia for motor impairment), to assess explicit anosognosia for motor impairments. The VATAm is a questionnaire that compares a patients self-evaluation with a caregivers’ evaluation of the patients abilities on a series of motor tasks. In addition, the test overcomes some of the limitations of the existing structured interviews and questionnaires, by enhancing reliability, improving data interpretation and diagnosis, and enabling assessment of patients with aphasia.