PubMed Health⌕ Search

Biomedical subjects

M Jane Riddoch

Publications and source records attributed to M Jane Riddoch.

7 recordsLinked to original sources
PubMed2003

Visual agnosia.

As was originally proposed by Lissauer, visual recognition may break down either at an apperceptive or at an associative level. At an apperceptive level, finer grain distinctions may be made; the authors distinguished here between disorders of shape recognition and perceptual integration. It is not the case, however, that all patients with visual recognition deficits have impaired perception: poor recognition and naming may also result from damage to stored perceptual knowledge (e.g., structural descriptions), from problems in accessing semantic knowledge, from perceptual knowledge, or from impairments to semantic knowledge itself. These represent different types of associative deficit. In some cases, mild damage to stored perceptual knowledge also generates problems that are more severe on naming than on recognition and more severe for some categories of objects than others.

Adult↗
PubMed2003

Seeing the action: neuropsychological evidence for action-based effects on object selection.

Previous studies have shown that selection for perceptual report is often limited to one object at a time, with elements being selected together if they belong to part of the same perceptual group. Here we used the neuropsychological phenomenon of extinction in human patients with parietal lesions to show that selection is influenced also by action relations between objects. Performance was better for objects that were positioned spatially so that they could be used together, relative to objects that were positioned inappropriately for their combined use. The action relation was critical, as performance for pictures did not improve if the items were only verbally associated. We found the opposite result with words. Effects of action relations emerged even on trials where only one object could be reported, showing implicit coding of 'action' units for selection. The effects of verbal associations may instead reflect priming between lexical entries.

Aged↗
PubMed2003

From what to where: neuropsychological evidence for implicit interactions between object- and space- based attention.

Three experiments examined nonspatial extinction in G.K., a patient with bilateral parietal damage. Experiment 1 demonstrated nonspatial extinction (poor detection of a weak relative to a stronger perceptual group), even when the stronger group was less complex than the weaker group. Experiment 2 showed improved report of a letter falling at the location of the stronger group, but explicit judgments of the location of the letter were at chance. Experiment 3 replicated the object-cuing benefit, though G.K. could not discriminate whether a letter fell at the same location as the stronger perceptual group. The data indicate coupling between object- and space-based attention, so that spatial attention is drawn to the location occupied by the winner of object-based competition for selection. In this case, what cues where. This coupling operates implicitly, even when explicit location judgments are impaired.

Agnosia↗
PubMed2002

Widening the sphere of influence: using a tool to extend extrapersonal visual space in a patient with severe neglect.

We report evidence that visual representations of space close to the body can be extended when a patient uses a tool to explore the environment. HB had severe neglect of left and far spatial regions which was determined more by how locations were visually perceived than by how they were represented tactilely or through proprioception. His ability to detect visual targets in left and far space was improved, however, when he held a tool. He also had limited tactile/proprioceptive knowledge about the location of his hand. These data suggest that by holding a tool, HB's more intact representation of near, visual space could be extended to include stimuli presented at a distance from his body. This extension of space improved his detection of visual stimuli. We discuss the implications of the results for the nature of our internal representation of space.

Cognition Disorders↗
PubMed2002

Dissociations between object knowledge and everyday action.

We report the case of a patient, MC, with Alzheimer's disease, who showed poor ability to name visually presented objects and poor visual access to the concepts of objects relative to a group of control patients (also with dementia). She performed well when words instead of objects were used in the various tasks. The data suggest that she has impaired access to semantic knowledge from vision. Surprisingly, she performed well when asked to perform everyday tasks with the same objects that had proved problematic in tests of visual naming and semantics. MC's pattern of performance is consistent with there being a direct route from vision to action and with the proposal that chaining between actions allows the development of action schemas which may operate even when there is impaired access to semantic knowledge.

Activities of Daily Living↗
PubMed2002

Treatment of visual neglect in elderly patients with stroke: a single-subject series using either a scanning and cueing strategy or a left-limb activation strategy.

BACKGROUND AND PURPOSE: The presence of unilateral visual neglect (UVN) may adversely affect functional recovery, and rehabilitation strategies that are practical for use in clinical settings are needed. The purpose of this study was to evaluate the use of 2 approaches to reduce UVN in people who have had strokes. SUBJECTS: Seven elderly patients with stroke and severe left UVN, aged 60 to 85 years, were recruited from a stroke rehabilitation unit. METHODS: A nonconcurrent, multiple-baselines-across-subjects approach, with an A-B-A treatment-withdrawal single-subject experimental design, was used. Five subjects received a scanning and cueing approach, and 2 subjects received a contralesional limb activation approach, for 10 one-hour sessions. In the former approach, active scanning to the left was encouraged by the therapist, using visual and verbal cues and a mental imagery technique, during reading and copying tasks and simple board games. In the latter approach, functional and goal-oriented left upper-limb activities in neglected hemispace were encouraged. Unilateral visual neglect was examined by a masked (blinded) examiner throughout all phases using the Star Cancellation Test, the Line Bisection Test, and the Baking Tray Task. Data were analyzed using visual and inferential statistical techniques. RESULTS: Both subjects who received limb activation and 3 of the 5 subjects who received scanning and cueing showed a reduction in UVN in one or more tests. This improvement was maintained during the withdrawal phase. DISCUSSION AND CONCLUSION: Both approaches had a positive effect of reducing aspects of UVN in some subjects relative to no-treatment baselines. However, causality cannot be assured in the absence of controls. The approaches are practical for use in rehabilitation settings. These procedures warrant further replication across subjects, settings, and therapists.

Aged↗