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PubMed2004

Auditory-visual speech perception in an adult with aphasia.

The evaluation of auditory-visual speech perception is not typically undertaken in the assessment of aphasia; however, treatment approaches utilise bimodal presentations. Research demonstrates that auditory and visual information are integrated for speech perception. The strongest evidence of this cross-modal integration is the McGurk effect. This indirect measure of integration shows that presentation of conflicting tokens may change perception (e.g. auditory /bi/ + visual /gi/ = /di/). The purpose of this study was to investigate the ability of a person with mild aphasia to identify tokens presented in auditory-only, visual-only and auditory-visual conditions. It was hypothesized that performance would be best in the bimodal condition and that presence of the McGurk effect would demonstrate integration of speech information. Findings did not support the hypotheses. It is suspected that successful integration of AV speech information was limited by a perseverative response pattern. This case study suggests the use of bisensory speech information may be impaired in adults with aphasia.

Acoustic Stimulation↗
PubMed2001

Perceptual skills of children with developmental coordination disorder.

The aim of this study was to investigate whether children with a Developmental Coordination Disorder (DCD) experience problems in the processing of visual, proprioceptive or tactile information. Different aspects of visual perception were tested with the Developmental Test of Visual Perception (DTVP-2), tactile perception was assessed with the Tactual Performance Test (TPT), and a manual pointing task was employed to measure the ability to use visual and proprioceptive information in goal-directed movements. Nineteen children with DCD and nineteen age and sex-matched controls participated in this study. Differences between groups were most pronounced in the subtests measuring visual-motor integration of the DTVP-2, and in two subtests measuring visual perception (visual closure and position in space). On average the children with DCD performed slightly below the norm for tactile perception, with only three children failing the norm. On the manual pointing task, children with DCD made inconsistent responses towards the targets in all three conditions (visual, visual-proprioceptive and proprioceptive condition). No significant differences between groups were found for absolute error. Inspection of the individual data revealed that only two children failed on the majority of perceptual tasks in the three modalities. Across tasks, no consistent pattern of deficits appeared, illustrating the heterogeneity of the problems of children with DCD.

Child↗
PubMed1979

Longitudinal study of cognitive abilities and academic achievement.

Assessment was made of the effectiveness of a battery of cognitive tests administered in kindergarten in the prediction of sixth grade achievement in reading comprehension, spelling, language usage, and arithmetic. Cognitive abilities included several factors of intelligence, visual perception and visual sequential memory, visual-motor integration, and auditory perception and auditory sequential memory. Measures of prior learning were also included. Subjects were 58 children in a suburban public school district. A criterion for predictive utility for correlation coefficients was established, and simple correlation coefficients for various kindergarten measures and sixth grade achievement ranged from the criterion of .35 to .69. In partial correlations with the effects of ability to understand ideas expressed in words removed, correlation coefficients for various cognitive measures and achievement tests ranged from the criterion of .35 to .63. Combinations of kindergarten measures having optimal multiple correlations with later school achievement generally approached or exceeded .70. These findings are discussed and suggestions are made for further research.

Achievement↗
PubMed1998

Cortical regions involved in visual texture perception: a fMRI study.

To determine visual areas of the human brain involved in elementary form processing, functional magnetic resonance imaging (fMRI) was used to measure regional responses to two types of achromatic textures. Healthy young adults were presented with 'random' textures which lacked spatial organization of the black and white pixels that make up the image, and 'correlated' textures in which the pixels were ordered to produce extended contours and rectangular blocks at multiple spatial scales. Relative to a fixation condition, random texture stimulation resulted in increased signal intensity primarily in the striate cortex, with slight involvement of the cuneus and middle occipital, lingual and fusiform gyri. Correlated texture stimulation also resulted in activation of these areas, yet the regional extent of this activation was significantly greater than that produced by random textures. Unlike random stimulation, correlated stimulation additionally resulted in middle temporal activation. Direct comparison of the two stimulation conditions revealed significant differences most consistently in the anterior fusiform gyrus, but also in striate, middle occipital, lingual and posterior temporal regions in subjects with robust activation patterns. While both random and correlated stimulation produced activation in similar areas of the occipital lobe, the increase in regional activation during the correlated condition suggests increased recruitment of neuronal populations occurs in response to textures containing visually salient features. This increased recruitment occurs within striate, extrastriate and temporal regions of the brain, also suggesting the presence of receptive field mechanisms in the ventral visual pathway that are sensitive to features produced by higher-order spatial correlations.

Adult↗
PubMedDate not supplied

[Perception in space. Visual aspects of space perception].

The ability to apprehend and appropriate space is based on a series of perceptive and cognitive processes, in which vision plays a leading part. Preliminary, elementary operations first allow a subject to achieve the elaboration of a visually structured percept. Both experiences on healthy subjects, and pathological data have provided evidence for a right hemisphere superiority in tasks such as localization of stimuli and discrimination of line orientation. Depth perception rests both on indirect cues (e.g. relative size of objects, perspective and movement parallax) and on two types of specific stereoscopic processes: the so-called local and global stereoscopies, which depend respectively on the integrity of visual cortices and of inferior occipito-temporal areas (with a right-hemisphere dominance). Movement perception is integrated at the level of area V5, at the lateral occipito-temporal junction on both sides. The accuracy of reaching movements and displacements within space require the elaboration of a system of coordinates in which the position of the egocentric reference will then be taken into account. This is achieved by successive coding of eye and head position relative to the body axis, and by building the body reference from proprioceptive and vestibular afferences to the parietal cortex. Finally, attention must be both diffusely scattered throughout the whole space and voluntarily allocated as needed on a given object. Simultanagnosia and unilateral spatial neglect (USN) are examples of disruption of these attentional processes. Simultanagnosia illustrates the loss of the ability to shift attention from one point to another, but both shrinking of the attentional field and poorly sustained fixation are also possible mechanisms of this syndrome. USN probably has several components. Unilateral brain damage causes interhemispheric attentional imbalance that explains the attentional preference for the ipsilesional side of space. The predominance of neglect following right-sided lesions might be the consequence of hemispheric specialization regarding directed attention, with the left hemisphere preferentially allocating attention to objects and the right one being able to attend to the whole space. The anatomical basis of such a functional differentiation is still unclear.

Animals↗
PubMed2003

Mental extrapolation of target position is strongest with weak motion signals and motor responses.

Some accounts hold that the position of moving objects is extrapolated either in visual perception or visual short-term memory ("representational momentum"). However, some studies did not find forward displacement of the final position when smooth motion was used, whereas reliable displacement was observed with implied motion. To resolve this conflict, the frequency of position changes was varied to sample motion types between the extreme cases of implied and smooth motion. A continuous function relating frequency of target change and displacement was found: Displacement increased when the frequency of position changes was reduced. Further, the response mode was varied. Probe judgments produced less forward displacement than motor judgments such as mouse or natural pointing movements. Also, localization judgments were susceptible to motion context, but not to variations of probe shape or expectancy about trajectory length. It is suggested that forward displacement results from the extrapolation of the next step in the observed motion sequence.

Analysis of Variance↗
PubMed2001

Visual-auditory events: cross-modal perceptual priming and recognition memory.

Modality specificity in priming is taken as evidence for independent perceptual systems. However, Easton, Greene, and Srinivas (1997) showed that visual and haptic cross-modal priming is comparable in magnitude to within-modal priming. Where appropriate, perceptual systems might share like information. To test this, we assessed priming and recognition for visual and auditory events, within- and across- modalities. On the visual test, auditory study resulted in no priming. On the auditory priming test, visual study resulted in priming that was only marginally less than within-modal priming. The priming results show that visual study facilitates identification on both visual and auditory tests, but auditory study only facilitates performance on the auditory test. For both recognition tests, within-modal recognition exceeded cross-modal recognition. The results have two novel implications for the understanding of perceptual priming: First, we introduce visual and auditory priming for spatio-temporal events as a new priming paradigm chosen for its ecological validity and potential for information exchange. Second, we propose that the asymmetry of the cross-modal priming observed here may reflect the capacity of these perceptual modalities to provide cross-modal constraints on ambiguity. We argue that visual perception might inform and constrain auditory processing, while auditory perception corresponds to too many potential visual events to usefully inform and constrain visual perception.

Auditory Perception↗
PubMedDate not supplied

Visual performance and recovery in recently detoxified alcoholics.

In order to assess the impact of chronic alcohol misuse on basic visual functions, we investigated motion perception, visual short-term memory, and visual divided attention in recently detoxified patients and matched controls by means of visual psychophysical tasks. Subjects were tested twice within the first 3 weeks of detoxification in order to assess the potential recovery of visual performance. Patients demonstrated significant impairments in visual perception of coherent motion for slow, but not faster, speeds, and in speed discrimination as assessed by random dot kinematograms. Visual short-term memory tested with a delayed vernier discrimination task, on the other hand, was not significantly affected in patients. When processing hierarchical letters, a divided attention task, detoxified patients showed neither impairments in overall attentional capacity nor attentional allocation, but slightly enhanced interference of global information on local target processing. The results of the visual divided attention task contradict the predictions of the 'right hemisphere' hypothesis of alcoholism: global target information - mediated by the right hemisphere - was not only accessible to detoxified patients, but seemed to exert an even greater influence on local processing during early detoxification, than in matched controls. Limited recovery within the first 3 weeks was seen only in visual speed discrimination. Recently detoxified patients revealed deficits similar to intoxicated social drinkers in identical tests of visual perception of motion, but not visual short-term memory.

Adult↗
PubMed2006

Visual phonemic ambiguity and speechreading.

PURPOSE: To study the role of visual perception of phonemes in visual perception of sentences and words among normal-hearing individuals. METHOD: Twenty-four normal-hearing adults identified consonants, words, and sentences, spoken by either a human or a synthetic talker. The synthetic talker was programmed with identical parameters within phoneme groups, hypothetically resulting in simplified articulation. Proportions of correctly identified phonemes per participant, condition, and task, as well as sensitivity to single consonants and clusters of consonants, were measured. Groups of mutually exclusive consonants were used for sensitivity analyses and hierarchical cluster analyses. RESULTS: Consonant identification performance did not differ as a function of talker, nor did average sensitivity to single consonants. The bilabial and labiodental clusters were most readily identified and cohesive for both talkers. Word and sentence identification was better for the human talker than the synthetic talker. The participants were more sensitive to the clusters of the least visible consonants with the human talker than with the synthetic talker. CONCLUSIONS: It is suggested that ability to distinguish between clusters of the least visually distinct phonemes is important in speechreading. Specifically, it reduces the number of candidates, and thereby facilitates lexical identification.

Acoustic Stimulation↗
PubMed2005

Hand movement observation by individuals born without hands: phantom limb experience constrains visual limb perception.

Increasing evidence suggests that the visual analysis of other people's actions depends upon the observer's own body representation or schema. This raises the question of how differences in observers' body structure and schema impact their perception of human movement. We investigated the visual experiences of two persons born without arms, one with and the other without phantom sensations. These participants, plus six normally-limbed control observers, viewed depictions of upper limb movement under conditions of apparent motion. Consistent with previous results (Shiffrar M, Freyd JJ (1990) Psychol Sci 1:257), normally-limbed observers perceived rate-dependent paths of apparent human movement. Specifically, biologically impossible motion trajectories were reported at rapid display rates while biologically possible trajectories were reported at slow display rates. The aplasic individual with phantom experiences showed the same perceptual pattern as control participants, while the aplasic individual without phantom sensations did not. These preliminary results suggest that phantom experiences may constrain the visual analysis of the human body. These results further suggest that it may be time to move beyond the question of whether aplasic phantoms exist and instead focus on the question of why some people with limb aplasia experience phantom sensations while others do not. In this light, the current results suggest that somesthetic representations are not sufficient to define body schema. Instead, neural systems matching action observation, action execution and motor imagery likely contribute to the definition of body schema in profound ways. Additional research with aplasic individuals, having and lacking phantom sensations, is needed to resolve this issue.

Amputees↗
PubMed2006

Increased inattentional blindness in severe traumatic brain injury: evidence for reduced distractibility?

PRIMARY OBJECTIVE: To examine the role of selective attention and visual perception in medicating inattentional blindness in a severe traumatic brain injured sample. RESEARCH DESIGN: Cross-sectional design with age and education matched control sample. METHODS AND PROCEDURES: Twenty participants with severe traumatic brain injury (n = 10) and matched controls (n = 10) completed a series of tests of focused attention (Stroop test), divided attention (Trail Making Test), visual perception (Visual Object and Space Perception Battery) and two tasks of inattentional blindness. MAIN OUTCOMES AND RESULTS: The group with severe TBI were significantly slower on the Stroop test and TMT and displayed significantly elevated Stroop interference and TMT ratio scores. On the inattentional blindness tasks, fewer TBI participants identified a distracting stimulus. CONCLUSION: The results indicate severe TBI is associated with deficits to focused and divided attention with the finding of a potentially more debilitating impairment arising from reduced distractibility following severe TBI.

Adult↗
PubMed2004

The reliability and clinical correlates of figure-ground perception in schizophrenia.

Schizophrenia subjects are impaired in a number of visual attention paradigms. However, their performance on tests of figure-ground visual perception (FGP), which requires subjects to visually discriminate figures embedded in a rival background, is relatively unstudied. We examined FGP in 63 schizophrenia patients and 27 control subjects and found that the patients performed the FGP test reliably and had significantly lower FGP scores than the control subjects. Figure-ground visual perception was significantly correlated with other neuropsychological test scores and was inversely related to negative symptoms. It was unrelated to antipsychotic medication treatment. Figure-ground visual perception depends on "top down" processing of visual stimuli, and thus this data suggests that dysfunction in the higher-level pathways that modulate visual perceptual processes may also be related to a core defect in schizophrenia.

Adult↗
PubMed2002

Visual speech perception without primary auditory cortex activation.

Speech perception is conventionally thought to be an auditory function, but humans often use their eyes to perceive speech. We investigated whether visual speech perception depends on processing by the primary auditory cortex in hearing adults. In a functional magnetic resonance imaging experiment, a pulse-tone was presented contrasted with gradient noise. During the same session, a silent video of a talker saying isolated words was presented contrasted with a still face. Visual speech activated the superior temporal gyrus anterior, posterior, and lateral to the primary auditory cortex, but not the region of the primary auditory cortex. These results suggest that visual speech perception is not critically dependent on the region of primary auditory cortex.

Acoustic Stimulation↗
PubMed1996

What young chimpanzees know about seeing.

Previous experimental research has suggested that chimpanzees may understand some of the epistemological aspects of visual perception, such as how the perceptual act of seeing can have internal mental consequences for an individual's state of knowledge. Other research suggests that chimpanzees and other nonhuman primates may understand visual perception at a simpler level; that is, they may at least understand seeing as a mental event that subjectively anchors organisms to the external world. However, these results are ambiguous and are open to several interpretations. In this Monograph, we report the results of 15 studies that we conducted with chimpanzees and preschool children to explore their knowledge about visual perception. The central goal of these studies was to determine whether young chimpanzees appreciate that visual perception subjectively links organisms to the external world. In order to achieve this goal, our research incorporated three methodological objectives. First, we sought to overcome limitations of previous comparative theory of mind research by using a fairly large sample of well-trained chimpanzees (six to seven animals in all studies) who were all within 8 months of age of each other. In contrast, previous research has typically relied on the results of one to four animals ranging widely in age. Second, we designed our studies in order to allow for a very sensitive diagnosis of whether the animals possessed immediate dispositions to act in a fashion predicted by a theory of mind view of their psychology or whether their successful performances could be better explained by learning theory. Finally, using fairly well-established transitions in preschool children's understanding of visual perception, we sought to establish the validity of our nonverbal methods by testing predictions about how children of various ages ought to perform. Collectively, our findings provide little evidence that young chimpanzees understand seeing as a mental event. Although our results establish that young chimpanzees both (a) develop algorithms for tracking the visual gaze of other organisms and (b) quickly learn rules about the configurations of faces and eyes, on the one hand, and subsequent events, on the other, they provide no clear evidence that these algorithms and rules are grounded in a matrix of intentionality. Particularly striking, our results demonstrate that, even though young chimpanzee subjects spontaneously attend to and follow the visual gaze of others, they simultaneously appear oblivious to the attentional significance of that gaze. Thus, young chimpanzees possess and learn rules about visual perception, but these rules do not necessarily incorporate the notion that seeing is "about" something. The general pattern of our results is consistent with three different possibilities. First, the potential existence of a general developmental delay in psychological development in chimpanzees (or, more likely, an acceleration in humans) leaves open the possibility that older chimpanzees may display evidence of a mentalistic appreciation of seeing. Second, chimpanzees may possess a different (but nonetheless mentalistic) theory of attention in which organisms are subjectively connected to the world not through any particular sensory modality such as vision but rather through other (as-of-yet unspecified) behavioral indicators. Finally, a subjective understanding of visual perception (and perhaps behavior in general) may be a uniquely evolved feature of the human lineage.

Animals↗
PubMed1987

Evaluating the visual-perceptual skills of children with cerebral palsy.

The Test of Visual-Perceptual Skills (TVPS) was used to determine if children with cerebral palsy demonstrated problems in visual perception on a motor-free visual perception test. Twenty-four children with cerebral palsy and 24 normal children, all of normal intelligence, were given the TVPS. Results showed that children with cerebral palsy attained significantly lower mean perceptual quotients than did the normal children. The TVPS appears to be a useful tool for the occupational therapist in evaluating visual perception in children with cerebral palsy.

Attention↗