Biomedical subjects

Jason B Mattingley

Publications and source records attributed to Jason B Mattingley.

42 records · Page 3Linked to original sources

PubMed2003

Trunk- and head-centred spatial coordinates do not affect free-viewing perceptual asymmetries.

Turning the trunk or head to the left can reduce the severity of leftward neglect. This study sought to determine whether turning the trunk or head to the right would reduce pseudoneglect: A phenomenon where normal participants underestimate the rightward features of a stimulus. Participants made luminance judgements of two mirror-reversed greyscales stimuli. A preference for selecting the stimulus dark on the left was found. The effect of trunk-centred coordinates was examined in Expt. 1 by facing the head toward the display and turning the trunk to the left, right or toward the display. Head-centred coordinates were examined in Expt. 2 by directing the eyes toward the display and then turning the head and trunk. No effect of rotation was observed. It was concluded that the leftward bias for the greyscales task could be based on an object-centred attentional bias or left-to-right eye scanning habits.

Adolescent↗

PubMed2002

Visuomotor adaptation to optical prisms: a new cure for spatial neglect?

In this issue, McIntosh and colleagues show that visual and haptic deficits in spatial neglect can be improved following a brief period of visuomotor adaptation to rightward displacing optical prisms. Their paper is the latest in a series of recent studies that have demonstrated the utility of prismatic adaptation in reducing the clinical symptoms of unilateral spatial neglect (Pisella et al., 2002; Rode et al., 1999; Rossetti et al., 1998; Rossetti et al., 1999). The technique has great promise as a rehabilitative tool, and may provide unique insights into the underlying mechanisms of spatial perception and action in normality and pathology. In this article I provide an introduction to the neuropsychological syndrome of spatial neglect, highlighting the significant rehabilitative challenges it poses for clinicians. I then outline the prism adaptation procedure, and consider the possible reasons for its beneficial effects in patients with spatial neglect. I conclude with some open questions and suggestions for future research.

Adaptation, Psychological↗

PubMed2002

Local-global processing in Alzheimer's disease: an examination of interference, inhibition and priming.

Impairments of memory, praxis, gnosis, language and executive functioning are well documented in Alzheimer's disease (AD). Functions, such as attention, however, have only recently been systematically investigated. We used Navon-type stimuli (large "global" digits composed of smaller "local" digits) to assess 12 AD participants' plus age-matched controls' ability to focus and alter the scale of their spatial attention. In the first experiment, participants responded to either the global or local characters within a block, ignoring characters at the other spatial scale. Healthy young adults (n=12) demonstrated the normal 'global precedence' effect on this task. In contrast, participants with AD and their age-matched controls were significantly faster on the local task than on the global task, suggesting in these groups a 'local precedence' effect. This consisted of both a local advantage and a local-on-global interference effect. In a second experiment, participants searched for designated targets which occurred unpredictably at either the local or global spatial scale. Participants with AD were significantly slower and more error-prone than older controls. In addition, participants with AD showed a greater cost in reaction time (RT) when required to switch spatial scales on consecutive trials, compared to no switch responses at the same spatial scale on consecutive trials. Thus, AD may impair the ability to process global figures, due perhaps to involvement of posterior parietal areas. Further, participants with AD were poor at inhibiting irrelevant stimuli and at inhibiting attentional allocation to an irrelevant spatial scale, which may relate to prefrontal pathology.

Adult↗

PubMed2002

The octave illusion revisited: suppression or fusion between ears?

The octave illusion occurs when each ear receives a sequence of tones alternating by 1 octave but with the high and low tones in different ears. Most listeners perceive these stimuli as a high pitch in one ear alternating with a low pitch in the other ear. D. Deutsch and P. L. Roll (1976) interpreted this phenomenon as evidence for a what-where division of auditory processing caused by sequential interactions between the tones. They argued that the pitch follows the frequency presented to the dominant ear but is lateralized toward the higher frequency component. This model was examined in 4 experiments. Results indicate that the perceived pitch approximates the fundamental frequency and that the illusion does not depend on sequential interactions. The octave illusion may arise from an interaction between dichotic fusion and binaural diplacusis rather than from suppression as proposed by Deutsch.

Adolescent↗

PubMed2002

Anomalous perception in synaesthesia: a cognitive neuroscience perspective.

An enduring question in cognitive neuroscience is how the physical properties of the world are represented in the brain to yield conscious perception. In most people, a particular physical stimulus gives rise to a unitary, unimodal perceptual experience. So, light energy leads to the sensation of seeing, whereas sound waves produce the experience of hearing. However, for individuals with the rare phenomenon of synaesthesia, specific physical stimuli consistently induce more than one perceptual experience. For example, hearing particular sounds might induce vivid experiences of colour, taste or odour, as might the sight of visual symbols, such as letters or digits. Here we review the latest findings on synaesthesia, and consider its possible genetic, neural and cognitive bases. We also propose a neurocognitive framework for understanding such anomalous perceptual experiences.

Auditory Perception↗

PubMedDate not supplied

Prism adaptation and spatial attention: a study of visual search in normals and patients with unilateral neglect.

Visuomotor adaptation to a prism-induced lateral displacement of the visual field induces mild perceptual biases in healthy individuals and improves symptoms of unilateral neglect. The present study employed a speeded visual search task to test the hypothesis that prism adaptation induces an adaptive redistribution of selective spatial attention. In Experiment 1, 32 neurologically healthy, right-handed participants were adapted to a 150 prism-induced lateral (left or right) displacement of the visual field. Spatial attention was measured by search time and error-rate in unique-feature ("preattentive") and feature-absent ("serial") visual search tasks, before and after prism adaptation. The single target appeared at different locations within arrays of 12, 24 or 48 items. Contrary to the attentional hypothesis, the pattern of search performance across the display remained unchanged following prism adaptation. In Experiment 2, we tested four patients with unilateral right hemisphere damage on the visual search tasks, before and after adaptation to 15 degrees rightward-displacing prisms. All four patients showed a pathological gradient of spatial attention toward the ipsilesional side prior to adaptation. Consistent with the results from Experiment 1, the gradient in search performance shown by the patients did not change following prism adaptation. Taken together, these findings suggest that the perceptual aftereffects in normals and amelioration of unilateral neglect following prism adaptation are not mediated by an adaptive redistribution of spatial attention.

Adaptation, Psychological↗