Post-operative telephone notification: a theatre nurse's role?
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Coronary Artery Bypass↗
Biomedical subjects
J Driver
Publications and source records attributed to J Driver.
Enhancement of selective listening by illusory mislocation of speech sounds due to lip-reading.
Mechanisms of human attention allow selective processing of just the relevant events among the many stimuli bombarding our senses. Most laboratory studies examine attention within just a single sense, but in the real world many important events are specified multimodally, as in verbal communication. Speech comprises visual lip movements as well as sounds, and lip-reading contributes to speech perception, even for listeners with good hearing, by a process of audiovisual integration. Such examples raise the problem of how we coordinate our spatial attention across the sensory modalities, to select sights and sounds from a common source for further processing. Here we show that this problem is alleviated by allowing some cross-modal matching before attentional selection is completed. Cross-modal matching can lead to an illusion, whereby sounds are mislocated at their apparent visual source; this crossmodal illusion can enhance selective spatial attention to speech sounds.
Attention↗
Edge-assignment and figure-ground segmentation in short-term visual matching.
Eight experiments examined the role of edge-assignment in a contour matching task. Subjects judged whether the jagged vertical edge of a probe shape matched the jagged edge that divided two adjoining shapes in an immediately preceding figure-ground display. Segmentation factors biased assignment of this dividing edge toward a figural shape on just one of its sides. Subjects were faster and more accurate at matching when the probe edge had a corresponding assignment. The rapid emergence of this effect provides an on-line analog of the long-term memory advantage for figures over grounds which Rubin (1915/1958) reported. The present on-line advantage was found when figures were defined by relative contrast and size, or by symmetry, and could not be explained solely by the automatic drawing of attention toward the location of the figural region. However, deliberate attention to one region of an otherwise ambiguous figure-ground display did produce the advantage. We propose that one-sided assignment of dividing edges may be obligatory in vision.
Analysis of Variance↗
Audiovisual links in endogenous covert spatial attention.
In 7 experiments we investigated cross-modal links for endogenous covert spatial orienting in hearing and vision. Participants judged the elevation (up vs. down) of auditory or visual targets regardless of their laterality or modality. When participants were informed that targets were more likely on 1 side, elevation judgments were faster on that side, even if the modality of the target was uncertain. When participants expected a target on a particular side in just 1 modality, corresponding shifts of covert attention also took place in the other modality, as evidenced by faster elevation judgments on that side. However, it was possible to "split" auditory and visual attention when targets in the 2 modalities were expected on constant but opposite sides throughout a block, although covert orienting effects were larger when targets were expected on the same side in both modalities. These results show that although endogenous covert attention does not operate exclusively within a supramodal system, there are strong spatial links between auditory and visual attention.
Adolescent↗
On the spatial extent of attention in object-based visual selection.
A new test was devised to avoid previous confounds in measures of object-based limits on divided visual attention. The distinction between objects was manipulated across a wide spatial extent. Target elements appeared on the same object only when far apart, and appeared close only when on different objects, so that object effects could not be reduced to spatial effects, nor vice versa. Subjects judged whether two odd elements within a display of two dashed lines were the same or different. They performed better when the target elements were far apart on a common line rather than on two distinct lines even though the latter arrangement was more likely. Thus, nonstrategic object-based limits on divided attention can arise even across large distances. However, when subjects were precued to expect targets in a narrow region of the display, the object effect was eliminated, implying that object-based selection may only operate within spatially attended regions.
Adolescent↗
Spatial repetition blindness is modulated by selective attention to color or shape.
Subjects reported either the colors or shapes of two simultaneous masked letters. Our first study found that they were less accurate when the reported features were identical ("repetition blindness," or RB), while repetition along the unreported dimension had no effect. Three follow-up studies confirmed that when the same dimension was judged (overtly or covertly) for both stimuli, performance was only affected by repetition along that dimension. However, when different dimensions were judged for the two stimuli, performance was affected by repetition on both dimensions. These findings support new conclusions about both RB and visual attention. First, RB depends critically on visual attention, rather than simply on the stimulus presented or the overt response required. Second, while attention can be restricted to a single visual dimension, this is efficient only when the same dimension is selected for both objects. Selecting the color of one object and the shape of another simultaneous object results in both dimensions being accessed for both objects.
Adult↗
Object segmentation and visual neglect.
A major development in recent research on human visual attention has been the increasing interplay between research on normal attentional mechanisms, and accounts of unilateral neglect and extinction after brain-damage in terms of damage to these mechanisms. Although there are potential pitfalls in this approach, it has already proved useful. This is illustrated for the debate over whether segmentation processes precede spatial attention in vision. This debate began in the normal literature, but has since motivated several studies of visual neglect and extinction. These reveal that various segmentation processes can influence which region of a scene will be neglected or extinguished, implying that grouping may precede the abnormal bias in spatial attention, and showing that considerable residual processing can take place in the neglected or extinguished visual field. The extent of this residual processing is tentatively related to emerging anatomical data.
Attention↗
Selective attention in humans: normality and pathology.
Human attention is now studied with a variety of methods, ranging from neuroimaging to behavioural studies of normals and brain-damaged patients. Recent results obtained using these methods converge on several conclusions. First, attention can affect early stages of perception. Second, in low-load conditions, unattended stimuli can be processed to high levels, albeit in a tacit manner. Third, the distribution of attention depends on an interplay between reflexive and voluntary factors. Finally, there are strong attentional links between the sensory modalities, and between perception and action. These links might be exploited to remediate attentional deficits after brain injury.
Animals↗
Tilted letters and tilted words: a possible role for principal axes in visual word recognition.
Subjects made lexical decisions to columnar letter strings in which every letter was either upright or tilted 90 degrees clockwise as if the whole letter string had been rotated from the horizontal. Lexical decisions were faster in the latter case. The advantage for the tilted format was also found when all strings were presented in aLtErNaTiNg CaSe or in uppercase, so this advantage cannot be due to preservation of the tilted words' global shape. The cost for the upright-letter format increased with the number of letters in the columnar strings. These data suggest that words recognition may involve shape description or position coding relative to a reference frame based on the principal axis of the letter string.
Adult↗
Parallel detection of Kanizsa subjective figures in the human visual system.
Subjective figures, seen in the absence of luminance gradients (Fig. 1), provide a phenomenal illusion that can be related to the properties of single cells in the visual cortex, offering a rare bridge between brain function and visual awareness. It remains controversial whether subjective figures arise from intelligent cognitive mechanisms, or from lower-level processes in early vision. The cognitive account implies that the perception of subjective figures may require serial attentive processing, whereas on the low-level account they should arise in parallel at earlier visual stages. Physiological evidence apparently fits a low-level account and indicates that some types of subjective contour may be detected earlier than the conventional Kanizsa type. Here we report that even Kanizsa subjective figures can be detected without focal attention at parallel stages of the human visual system.
Humans↗
Axis-based neglect of visual shapes.
A new test of "object-centered" visual neglect uses equilateral triangles, with ambiguous principal axes that can be manipulated by context. Three left neglect patients detected gaps in such triangles. The location of the gap relative to the biased principal axis was varied, while maintaining the same egocentric locus. More gaps were missed on the left of the axis. This supports Driver and Halligan's (Cognit. Neuropsychol. 8, 475-496, 1991) claim that neglect can apply to the contralesional side of a shape's principal axis, while avoiding serious flaws in their method. The relation between axis-based neglect and other cases of object-centred neglect is discussed.
Attention↗
Reading of letters and words in a patient with Balint's syndrome.
A patient with bilateral parietal damage, and Balint's syndrome, named visual letters. These were presented individually or within four-letter strings. Solitary letters were identified very accurately. In the case of strings, more letters were correctly reported for words than for nonwords, and more for pronounceable than for unpronounceable nonwords. When required to read words as a whole, performance was better than predicted by letter-reports. These results extend the object-based limitation apparent in Balint's syndrome to the case of reading. The component letters of a string benefit when they form a familiar global object, rather than requiring representation as multiple separate objects. The patient occasionally made homophonic errors when listing the letters in a visual word. This suggests an attempt to bypass visual simultanagnosia by treating the string as a single object, deriving a holistic phonological code for it, and then decomposing this into component letters via spelling rules.
Agnosia↗
Shifting visual attention between objects and locations: evidence from normal and parietal lesion subjects.
Space- and object-based attention components were examined in neurologically normal and parietal-lesion subjects, who detected a luminance change at 1 of 4 ends of 2 outline rectangles. One rectangle end was precued (75% valid); on invalid-cue trials, the target appeared at the other end of the cued rectangle or at 1 end of the uncued rectangle. For normals, the cost for invalid cues was greater for targets in the uncued rectangle, indicating an object-based component. Both right- and left-hemisphere patients showed costs that were greater for contralesional targets. For right-hemisphere patients, the object cost was equivalent for contralesional and ipsilesional targets, indicating a spatial deficit, whereas the object cost for left-hemisphere patients was larger for contralesional targets, indicating an object deficit.
Adult↗
Visual attention and objects: evidence for hierarchical coding of location.
In 5 experiments, it was found that judging the relative location of 2 contours was more difficult when they belonged to 2 objects rather than 1. This was observed even when the 1- and 2-object displays were physically identical, with perceptual set determining how many objects they were seen to contain. Such a 2-object cost is consistent with object-based views of attention and with a hierarchical scheme for position coding, whereby object parts are located relative to the position of their parent object. In further experiments, it was shown that in accord with this hierarchical scheme, the relative location of objects could disrupt judgments of the relative location of object parts, but the reverse did not occur. This was found even when the relative position of the parts could be judged more quickly than that of the objects.
Adult↗
Preserved figure-ground segregation and symmetry perception in visual neglect.
A central controversy in current research on visual attention is whether figures are segregated from their background preattentively, or whether attention is first directed to unstructured regions of the image. Here we present neurological evidence for the former view from studies of a brain-injured patient with visual neglect. His attentional impairment arises after normal segmentation of the image into figures and background has taken place. Our results indicate that information which is neglected and unavailable to higher levels of visual processing can nevertheless be processed by earlier stages in the visual system concerned with segmentation.
Aged↗
Levels of processing for visual stimuli in an "extinguished" field.
Volpe et al. (Nature 282, 722, 1979 [19]) described an experimental study of four patients with parietal tumours who were able to judge whether two simultaneous stimuli were identical or different, even when they were unable to name the stimulus contralateral to their brain injury. We report the case of another patient, E.M., in whom we have investigated this phenomenon further. E.M. had undergone a right temporal lobectomy to prevent recurrent seizures. She could correctly name photographs of objects presented in isolation to either the left or right visual field, at 150 msec exposure (although she was impaired for single objects on the left at 10 msec exposures). She was able to judge correctly whether two simultaneous objects on the left and right had the same or different names, even though she was often unable to name the object on the left. These judgements remained above chance when same-name pairs of stimuli showed the same object but seen from two different viewpoints, or even when they showed visually dissimilar exemplars of the same name category. This implies that the patient based her same-different judgements on categorical information about the pair of objects, even though she was often unable to name the contralateral object.
Adult↗
The neurobiology of selective attention.
Research in the field of selective visual attention has recently seen substantial progress in several areas. Neuroimaging and electrical recording results have indicated that selective attention amplifies neural activity in prestriate areas concerned with basic visual processing. Imaging and cellular studies are delineating the networks of anatomical areas that serve as the source of attentional modulation and have suggested that these networks are anatomically distinct from the sites of the resulting amplifications. Cognitive studies of visual search have explored the role of these amplified computations in the integration of visual features into objects. Attentional effects in normal subjects, and their disruption following brain injury, have revealed the mental representations upon which attention operates.
Animals↗
Movement and proximity constrain miscombinations of colour and form.
A relatively frequent error when reporting brief visual displays is to combine presented features incorrectly. It has been proposed that Gestalt grouping constrains such errors so that miscombined features tend to come from the same perceptual group. In three experiments it was examined whether this principle applies to grouping by motion, and to grouping by proximity. Miscombinations of colour and form were more likely to consist of a colour and form that had moved in the same direction than features which had moved in opposite directions. Miscombinations were also more likely for adjacent items. The implications of these results for the mechanisms of feature integration are discussed.
Adult↗