Nicolletta Beschin

Left of what? The role of egocentric coordinates in neglect

OBJECTIVES Egocentric coordinate systems centred on the trunk, head, and gaze have been investigated in a patient who displays severe extrapersonal neglect and in five control subjects. METHODS The subjects were tested with a blind tactile exploration task in five different experimental conditions in which the role of the three distinct frames of reference was individually controlled. RESULTS Only the trunk centred coordinates significantly influenced the performance of the patient, therefore proving of paramount importance in determining the boundaries of the neglected field. Similar results emerged from a single word reading task, in which the patient’s performance improved when the stimuli were presented to the right of his body’s midline. CONCLUSION These findings point to the importance of the body centred coordinate system in determining the area of extrapersonal spatial neglect.

Dissociating mental transformations and visuo‐spatial storage in working memory: Evidence from representational neglect

A study is reported of visuo‐spatial working memory in two individuals suffering from a cognitive deficit known as unilateral spatial neglect, and seven healthy control participants. Both patients have difficulties reporting details on the left side of imaged representations, and one has an additional difficulty with perceptual input to the left of his body midline. All participants were asked to report the location and identity of objects presented in novel 2 × 2 arrays that were either present throughout or were described orally by the experimenter, with no visual input. On half of the trials, the report was to be made from the opposite perspective, requiring 180 degree mental rotation of the mentally represented array. The patients show an impaired ability to report details from the presented or the imagined left, but had no difficulty with mental rotation. Results point to a clear separation between the processes of perception and those of visuo‐spatial working memory. Results also suggest that the patients might be suffering from damage to the system used for holding visuo‐spatial representations rather than a difficulty with attending to elements of that representation.

Agnosia for object orientation: naming and mental rotation evidence.

We have previously reported the performance of a patient (NL) who could recognize objects, but appeared to lack knowledge of their orientation. These results were interpreted as evidence that NL had isolated access to a viewpoint-independent (ventral stream) object recognition system. However, because NL’s responses on naming tasks were not timed, it was not possible to establish whether he showed the same pattern of reaction time performance generally accepted as evidence of a ‘mental rotation’ strategy in neurologically normal subjects. Here we report NL’s performance on two reaction time tasks, testing his ability to transform images when naming, and discriminating between rotated mirror image objects. As predicted, and in contrast to normal volunteers, NL showed no ‘mental rotation’ effect in his naming of misoriented objects. Paradoxically, he performed well on a traditional Shepard and Metzler mental rotation task. He also showed a normal orientation effect when dealing with misoriented faces. These findings offer further support for viewpoint-independent theories of object recognition, and bolster the claim that object orientation knowledge can be regarded as, in some respects, a special class of spatial information.

Anosognosia and neglect respond differently to the same treatments

Different techniques, such as optokinetic stimulation, adaptation to prismatic shift of the visual field to the right, or transcutaneous electrical nerve stimulation (TENS), have been shown to alleviate neglect, at least temporarily. We assessed the effect of these techniques on anosognosia and whether their therapeutic effect, if any, matches that on neglect. The effect of the three types of treatment on anosognosia and neglect was investigated in five patients presenting with both severe anosognosia and neglect. Patient 1 was treatment responsive to anosognosia but not to neglect, whereas patients 4 and 5 showed the reverse pattern, i.e., they were treatment responsive to neglect but not to anosognosia. This “treatment response bias” proved to be a valid means to investigate different effects of treatments in the same patient.

Rotated drawing: a mini mental state examination performance with strong lateralising significance.

which led to her admission to our department two months after the acute event. As well as these anterograde memory problems and a retrograde amnesia for about a week she showed normal behaviour and the neurological examination disclosed normal results. In neuropsychological testing she showed an IQ of 109 (WAIS) that was supposed to be somewhat lower than her premorbid level, although it was in the normal

Distance-mediated spatial neglect

Unilateral spatial neglect (USN) is usually assessed by means of individual stimuli or single arrays of stimuli. Seldom are stimuli presented as multiple objects or in spatially separated blocks, except in some tests for object-based neglect. The distance between individual objects or blocks of stimuli in such stimuli is implicitly considered irrelevant. We report on the case of a patient, EC, who showed severe USN in his everyday behavior, yet performed normally on standard tests for USN. Presented with stimuli in separate blocks, he performed flawlessly with 4 cm gaps between blocks, yet ignored all leftward blocks of stimuli when the gap was larger than this. EC’s dissociation between good performance on standard tasks and severe neglect with separate groups of stimuli, and the distance-mediated nature of his USN are novel observations with relevant theoretical and clinical implications.