Glyn William Humphreys

OBJECTIVES: 1. Assess validity of the Oxford Cognitive Screen (OCS-Plus), a domain-specific cognitive assessment designed for low-literacy settings, especially in low- and middle-income countries (LMIC); 2. Advance theoretical contributions in cognitive neuroscience in domain-specific cognitive function and cognitive reserve, especially related to dementia.

METHOD: In a cross-sectional study of a sample of 1,402 men and women aged 40-79 in the Health and Aging in Africa: A Longitudinal ...

In five experiments, we investigated the power of targets defined by the onset or offset of one of an object’s parts (contour onsets and offsets) either to guide or to capture visual attention. In Experiment 1, search for a single contour onset target was compared with search for a single contour offset target against a static background of distractors; no difference was found between the efficiency with which each could be detected. In Experiment 2, onsets and offsets were compared for ...

A series of experiments are reported in which the comparative constraints on single-feature and conjunction searches were examined. The first three tested the idea that the critical differences between these searches reflect the number of stimulus attributes that subjects must extract to make a response, that is, one in the feature condition, two in the conjunction condition. Targets were defined by possible pairwise combinations of a color, a size, and a shape. In another condition, ...

OBJECTIVE: We report data on the validation and functional correlates of Apples Test, which attempts to differentiate between different forms of unilateral neglect.

METHOD: Study 1 presents data from 25 participants with chronic brain lesions who completed the Apples Test and another standard measure of neglect (Star Cancellation). The patients' performance relative to 86 controls was assessed and their relative performance across the two tests compared. Study 2 recruited 115 acute ...

Prader-Willi syndrome (PWS) and Fragile X syndrome (FraX) are associated with distinctive cognitive and behavioural profiles. We examined whether repetitive behaviours in the two syndromes were associated with deficits in specific executive functions. PWS, FraX, and typically developing (TD) children were assessed for executive functioning using the Test of Everyday Attention for Children and an adapted Simon spatial interference task. Relative to the TD children, children with PWS and ...

Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes ...

BACKGROUND: The behavioural phenotypes of Prader-Willi (PWS) and Fragile-X (FraX) syndromes both comprise repetitive behaviours with differences between the profiles. In this study we investigated the context and antecedents to the repetitive behaviours and the association with other behavioural phenotypic characteristics in order to generate testable hypotheses regarding the cause of the behaviours.

METHOD: The parents or carers of 46 children with PWS (mean age 14.1 years; 20 girls), ...

Attentional biases towards food cues may be linked to the development of obesity. The present study investigated the mechanisms underlying attentional biases to food cues by assessing the role of top down influences, such as working memory (WM). We assessed whether attention in normal-weight, sated participants was drawn to food items specifically when that food item was held in WM. Twenty-three participants (15 f/8 m, age 23.4±5 year, BMI 23.5±4 kg/m(2)) took part in a laboratory based ...

In the Thatcher illusion, a face with inverted eyes and mouth looks abnormal when upright but not when inverted. Behavioral studies have shown that thatcherization of an upright face disrupts perceptual processing of the local configuration. We recorded high-density EEG from normal observers to study ERP correlates of the illusion during the perception of faces and nonface objects, to determine whether inversion and thatcherization affect similar neural mechanisms. Observers viewed faces ...

Insights into the functional nature and neuroanatomy of spatial attention have come from research in neglect patients but to date many conflicting results have been reported. The novelty of the current study is that we used voxel-wise analyses based on information from segmented grey and white matter tissue combined with diffusion tensor imaging to decompose neural substrates of different neglect symptoms. Allocentric neglect was associated with damage to posterior cortical regions ...

The locus of category effects in picture recognition and naming was examined in two experiments with normal subjects. Subjects carried out object decision (deciding whether the stimulus is a “real” object or not) and naming tasks with pictures of clothing, furniture, fruit, and vegetables. These categories are distinguished by containing either relatively many exemplars with similar perceptual structures (fruit and vegetables;structurally similar categories), or relatively few exemplars ...

We report a series of 7 experiments examining the interaction between visual perception and action programming, contrasting 2 neuropsychological cases: a case of visual extinction and a case with extinction and optic ataxia. The patients had to make pointing responses to left and right locations, whilst identifying briefly presented shapes. Different patterns of performance emerged with the two cases. The patient with "pure" extinction (i.e., extinction without optic ataxia) showed ...

Visuospatial attention allows us to select and act upon a subset of behaviorally relevant visual stimuli while ignoring distraction. Bundesen's theory of visual attention (TVA) (Bundesen, 1990) offers a quantitative analysis of the different facets of attention within a unitary model and provides a powerful analytic framework for understanding individual differences in attentional functions. Visuospatial attention is contingent upon large networks, distributed across both hemispheres, ...

We examined whether monitoring asynchronous audiovisual speech induces a general temporal recalibration of auditory and visual sensory processing. Participants monitored a videotape featuring a speaker pronouncing a list of words (Experiments 1 and 3) or a hand playing a musical pattern on a piano (Experiment 2). The auditory and visual channels were either presented in synchrony, or else asynchronously (with the visual signal leading the auditory signal by 300 ms; Experiments 1 and 2). ...

Bauer, Jolicoeur, and Cowan (1996a, 1996b, 1998) have shown that visual search for a target among distractors is apparently serial if the target is nonlinearly separable from the distractors in a particular feature space (e.g., color or size). In contrast, if the target is linearly separable from the distractors, search is relatively easy and seemingly spatially parallel. We examined the contribution of top-down knowledge of the target to the linear separability effect on search. Two ...