Nicoletta Beschin

Auditory sustained attention is a marker of unilateral spatial neglect

The relationships between performance on a non-spatially-lateralized measure of sustained attention and spatial bias on tests sensitive to unilateral neglect were considered in a group of 44 patients with right hemisphere lesions following stroke. As predicted from earlier studies showing a strong association between unilateral spatial neglect and sustained attention, performance on a brief and monotonous tone-counting measure formed a significant predictor of spatial bias across a variety of measures of unilateral visual neglect. This study provides further evidence for a very close link between two attentional systems hitherto regarded as being quite separate, namely a spatial attention system implicated in unilateral neglect and a sustained attention system. A close connection between these two systems was predicted by Posner, who argued that the right hemisphere-dominant sustained attention system provides a strong modulatory influence on the functioning of the lateralized posterior attention system.

Personal versus extrapersonal neglect: a group study of their dissociation using a reliable clinical test.

The validation of a simple quantitative clinical test of personal neglect is described in this study of 17 right brain damaged CVA patients with extrapersonal neglect, 14 without unilateral extrapersonal neglect, 13 left brain damaged CVA patients and 17 age-matched controls. The test had a high reliability and clearly differentiated neglect patients from all other groups. Furthermore the test identified a much higher incidence of personal neglect among extrapersonal neglect patients (59%) than has previously been found. Moreover this study confirms earlier findings by showing a double dissociation between personal and extrapersonal neglect. Seven patients with extrapersonal neglect showed no personal neglect while five patients showing no extrapersonal neglect did show personal neglect on this test.

Attentional competition between modalities: extinction between touch and vision after right hemisphere damage.

The phenomenon of extinction, which occurs frequently after unilateral brain damage, involves a failure to detect the more contralesional of two simultaneously presented stimuli, but with preserved detection of single ipsilesional or contralesional stimuli. Current accounts suggest that the disorder reflects a bias of selective attention, in which ipsilesional stimuli have a competitive advantage. Extinction may be manifested within any one of the major sensory modalities (vision, audition, touch), or it may occur within several modalities in a given individual. Given recent evidence in normals for attentional links between separate sensory modalities, we examined whether extinction can also occur cross-modally, i.e. for double-simultaneous stimuli in separate sensory modalities. We tested whether an ipsilesional event sufficient to extinguish a contralesional stimulus within the same modality may also extinguish a contralesional stimulus in a different modality. Our three patients had right hemisphere damage, and reliable within-modality extinction for visual and tactile stimuli. They also showed significant cross-modal extinction, such that an ipsilesional tactile (or visual) event extinguished awareness of a simultaneous visual (or tactile) event on the contralesional side. These results, which provide the first quantitative evidence for cross-modal extinction, were replicated in a second experiment in which visual and tactile stimuli in the cross-modal conditions were presented at non-homologous elevations within each hemispace. We conclude that after unilateral damage, ipsilesional stimuli have a competitive advantage over contralesional stimuli, and that this affects competition between stimuli from different modalities as well as stimuli within the same modality. These findings are consistent with recent evidence for competitive interactions between tactile and visual events in the control of spatial attention in normals.

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.

Improving the clinical diagnosis of personal neglect: a reformulated comb and razor test.

Beschin and Robertson (1997) devised a simple clinical test of left personal neglect, which characterises personal grooming behaviour according to the proportion of the total activity that is directed to the left side of the body. Although this test proved highly reliable, and more sensitive than prior diagnostic techniques, its formulation may yet be improved. The present paper reports a reanalysis of Beschin and Robertsons (1997) data, using additional control subjects, and a formula which characterises personal neglect as a lateral bias of behaviour rather than as a lateralised deficit. It is shown that this formula greatly enhances the tests sensitivity to the behavioural abnormalities of brain damaged patients, and it is recommended that this modification be adopted for the future diagnosis of personal neglect.

Just lying there, remembering: improving recall of prose in amnesic patients with mild cognitive impairment by minimising interference.

The hallmark of amnesia is poor explicit long‐term memory along with normal short‐term memory. It is often stated that information encountered by amnesic patients is forgotten within 1 minute of presentation. However, previous work has not distinguished between forgetting as a function of time versus the interfering material occupying that time. We show that there is a marked benefit of reduced interference in amnesic patients with mild cognitive impairment (MCI), a condition that is characterised by anterograde amnesia in the absence of other neuropsychological deficits and carries an increased risk for Alzheimers disease. The result suggests that long‐term memory is encoded in these patients to a greater extent than had been realised but that their memory is highly vulnerable to interference.

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.

Perceiving left and imagining right: dissociation in neglect.

Signor Piazza, a patient with a left parieto-occipital haemorrhage and a right thalamic stroke, showed severe right personal neglect (e.g. touching own body parts) and right perceptual neglect in tasks with (e.g. cancelling tasks) or without (e.g. description of a complex picture) motor response. He had also right-sided neglect dyslexia (including single words), without language impairments. However, the patient also presented with a clear left-sided deficit in the representational domain (e.g. imagery tasks). Signor Piazzas pattern of performance suggests dissociation between imagery and perception within the neglect syndrome.