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PubMed2000

Face and mouth inversion effects on visual and audiovisual speech perception.

Three experiments examined whether image manipulations known to disrupt face perception also disrupt visual speech perception. Research has shown that an upright face with an inverted mouth looks strikingly grotesque whereas an inverted face and an inverted face containing an upright mouth look relatively normal. The current study examined whether a similar sensitivity to upright facial context plays a role in visual speech perception. Visual and audiovisual syllable identification tasks were tested under 4 presentation conditions: upright face-upright mouth, inverted face-inverted mouth, inverted face-upright mouth, and upright face-inverted mouth. Results revealed that for some visual syllables only the upright face-inverted mouth image disrupted identification. These results suggest that upright facial context can play a role in visual speech perception. A follow-up experiment testing isolated mouths supported this conclusion.

Adult↗
PubMed1980

Influence of vertical and vertical-horizontal background patterns on perception of visual direction of a moving object.

30 boys and 30 girls, 6 yr. old, participated in a study assessing the influence of vertical and vertical-horizontal background patterns on the prediction of an object's directionality. An experimental apparatus was designed to permit modified spherical objects with interchangeable covers and backgrounds to move in three-dimensional space in three directions at selected speeds. The subject's task was to predict one of three possible directions of the object: the object moved toward the subject's midline or toward a point 18 in. to the left or right of the midline. The movement of all objects started at the same place which was 19.5 ft. in front of the subject. Prediction time was recorded for each of 10 trials. Analysis of variance indicated that vertical and vertical-horizontal patterns of the background behind the moving object did influence the prediction of an object's directionality by the girls.

Child↗
PubMed1996

Plasticity in the adult visual cortex: implications for the diagnosis of visual field defects and visual rehabilitation.

It has recently been shown that, contrary to long-held beliefs, sensory and motor maps are not stable in the adult cerebral cortex. Alteration of input from the periphery results in changes in topography in the cortex, including the primary visual cortex. Mechanisms involved consist mainly of reshaping the receptive field of cortical cells and increasing the sensitivity of deprived cells in the visual cortex. Cortical plasticity allows the brain to adapt to background modifications or to damage of the nervous system. It also underlies learning and attention processes. Cortical changes occurring after focal visual differentiation modify visual perception by filling in visual field defects with information from the area surrounding the scotoma. This modification causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. Although the effects of cortical plasticity are prominent in neuro-ophthalmological daily practice, they are usually unrecognized or greatly underestimated. These effects cause delay in recognizing visual field defects, and hence in receiving therapy, while affecting the results of some procedures for testing the visual field. Affected individuals who are unaware of their defects may have increased difficulty in coping with activities in everyday life. Up to now, phenomena related to plasticity in the visual system have been investigated mainly by psychophysicists and neurophysiologists. It is essential to start considering the various effects of cortical reorganization in clinical practice. It is especially important to introduce into clinics the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process, and the need to measure it. This dissociation should also be demonstrated to the affected subjects.

Adult↗
PubMed1997

[Scotomas: assessment by the patient and by the physician. There's nothing to see].

Contrary to long-held beliefs, plasticity occurs in the adult cerebral cortex, and allows the brain to adapt to background modifications or to damage of the nervous system. Cortical changes occurring following focal visual deafferentation modify visual perception, by filling in visual field defects with information from the area surrounding the scotoma. This causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. In ophthalmological daily practice, the effects of cortical plasticity are prominent, but are usually unrecognized. They result in unawareness of field defects following retinal photocoagulation, and cause delay in recognizing visual field defects, they e.g., in early stages of simple chronic glaucoma. In addition affect the results of some procedures for testing the visual field, and increase patients' difficulty in coping with activities in everyday life. It is important to introduce into clinical practice the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process. It can be demonstrated using a "double Amsler grid test".

Adult↗
PubMedDate not supplied

[Levels of plasmatic lead in children 8-10 years of age and its relation to changes in visual-motor system and balance].

OBJECTIVE: To assess the association between blood lead concentrations and visual-motor coordination and equilibrium in school age children. MATERIAL AND METHODS: In November-December 1998, a cross-sectional study was conducted among 255 children aged 8-10, who attended public schools in Sector 1 of the Oaxaca State Public Education Institute. Data were collected using the Frostig Evaluation of Visual Perception test and the equilibrium subscale of the Frostig Movement Skills Test Battery. A blood sample was taken to measure lead levels by atomic absorption spectrometry. Socioeconomic data and health histories were collected for use as control variables. Statistical analysis consisted of multiple regression models to test the relationship between blood lead level and the visual-motor and equilibrium tests. We assessed the effect of lead within the model using 1,000 Montecarlo simulations. RESULTS: The geometric mean of blood lead concentrations was 11.5 micrograms/dl (geometric standard deviation +6.3, -5.2). After adjusting for control variables, the visual-motor integration subscale was significantly related to blood lead concentration (p > 0.042). The visual-motor integration value decreased 1.78 (95% CI -3.51, -0.06) points for each 10 micrograms/dl increase in blood lead concentration. Among the four sub-tests comprising the visual-motor integration subscale, only eye-hand coordination (p = 0.045) and spatial relations (p = 0.039) were significantly related to blood lead. The visual-motor integration subscale was also significantly related to family income; greater income was related to greater testing scores. Only 3.1% of the children had clinically abnormal testing scores. No statistically significant association was found between blood lead levels and the Frostig subscale Index of Reduced Motor Response, the General Visual Perception Index, or any other equilibrium tests. CONCLUSIONS: The inverse relationship between blood lead concentration and visual-motor skill is consistent with results from studies in other countries. Blood lead levels common among children of Oaxaca are sufficient to produce subtle visual-motor impairments. These findings point out the need to strengthen the initiative to reduce child exposure to known lead sources, particularly lead-glazed ceramics, and thus lower the blood lead levels of the population.

Child↗
PubMed2004

Evidence of early neurobiological alternations in adolescents with posttraumatic stress disorder: a functional MRI study.

Neuroimaging studies of patients with posttraumatic stress disorder (PTSD) have largely been performed in adult populations. The purpose of the current study was to investigate neural correlates of PTSD in adolescents. Specifically, this study investigates whether a differential brain response was present during the visual perception and imaginary recollection of traumatic reminders in adolescents who developed PTSD versus those who did not after experiencing earthquake. Eleven Taiwanese adolescents (age range: 12-14 years) with traumatic experience of earthquake were enrolled. Five subjects fulfilled PTSD criteria, while the other six served as non-PTSD controls. Brain activation was measured by functional magnetic resonance image (fMRI) during visual perception and imagery recall of earthquake and neutral pictures at 14 months after earthquake. During earthquake imagery (as compared with neutral imagery), PTSD group demonstrated activation in the bilateral visual cortex, bilateral cerebellum and left parahippocampal gyrus, while control group did not. During earthquake perception (as compared with neutral perception), the control group showed activation over anterior cingulate, but the PTSD group did not. Intergroup comparison confirmed above discrepancies was significant. We concluded that neurobiological alternation of PTSD in adolescent was similar to those in adult and might have developed within 14 months after trauma exposure.

Adolescent↗
PubMed1984

Stability of whole vs part perceptions of visual stimuli.

In two experiments, college undergraduates (ns = 29, 30) were asked to describe in writing two different abstract line drawings. Responses were classified by over-all orientation to the whole or the individual parts of each drawing. Although findings of the two experiments were very similar, analysis indicated that no strong reliability of orientation existed across the two drawings.

Adult↗
PubMed1986

The nature of the abnormal perceptual experiences at the onset of schizophrenia.

Sixty schizophrenics and 40 depressives in remission from the floridly psychotic phase were given a semi-structured interview concerning their abnormal perceptual experiences at the onset of their illness. About 50% of each set of subjects had experienced an alteration in the quality of their perception. However, there was a fairly characteristic pattern in each case: emotional tainting of the world around, a sense of unreality and noise sensitivity in depression; and an indefinable, qualitative change in visual perception, particularly affecting the way colours, people, space and facial expression were viewed, in schizophrenia. Of the various theories which have been put forward to explain perceptual change in schizophrenia, a breakdown in gestalt appeared to explain these findings best.

Auditory Perceptual Disorders↗
PubMed2004

Colour through the thalamus.

Visual perception in humans and other primates depends on the retino-thalamo-cortical pathway. This pathway begins with retinal ganglion cells, which have axonal terminations in the lateral geniculate nucleus (LGN) of the thalamus. Each ganglion cell axon provides input to one or more LGN relay neurones and, in turn, nearly all the LGN relay neurones project to the primary visual cortex. Thus, this pathway forms the dominant functional input to cortical mechanisms for colour vision, as well as for other aspects of conscious visual perception. In this review, recent progress in understanding the transmission of signals for colour vision through the LGN is summarised, with emphasis on studies which provide links between function and structure.

Animals↗
PubMed1991

Perceptual fade-out occurs in the binocularly viewed Ganzfeld.

The conviction that time-varying signals are essential for normal visual perception was recently challenged by Bolanowski and Doty who observed that no 'blankouts' occurred in the binocularly viewed Ganzfeld. They suggested that monocularly perceived fading is caused by the eye in darkness suppressing the non-Ganzfeld-viewing eye. In the present paper, fade-out perception under monocular and binocular Ganzfeld viewing is compared, and the effect of the free eye on the Ganzfeld-viewing eye is tested directly. Results show that fading takes place under both monocular and binocular viewing. The data reenforce the view that transient inputs are necessary for maintaining visual perception. It is also shown that there are two Ganzfeld-related phenomena--fade-out and blackout. Fade-out, a slow gradual loss of brightness and of saturation perception, is observed by all subjects under both monocular and binocular viewing, and is affected by the light intensity and wavelength. It is probably retinal in origin. Blackout, a brief intermittent loss of all visual sensation, is experienced by some subjects in the monocular Ganzfeld only and is not appreciably affected by the light intensity or wavelength. It may be caused by a central blocking of all input to the perceiving stage.

Attention↗
PubMed1992

[Orthoptic treatment of dyslexia].

It is assumed that dyslexia is due to a brain-organic syndrome, either congenital or acquired in infancy, with specific gnostic deficiencies and faulty controlled binocular vision. The latter is expressed by an intermittent alternating central scotoma which is thought to be responsible for impaired visual perception during reading. The aim of the orthoptic treatment of dyslexia must therefore be to eliminate the alternating central scotoma by stabilizing the binocular vision, and thus to improve reading ability by achieving unimpaired visual perception.

Child↗
PubMed2005

Auditory attention to frequency and time: an analogy to visual local-global stimuli.

Two priming experiments demonstrated exogenous attentional persistence to the fundamental auditory dimensions of frequency (Experiment 1) and time (Experiment 2). In a divided-attention task, participants responded to an independent dimension, the identification of three-tone sequence patterns, for both prime and probe stimuli. The stimuli were specifically designed to parallel the local-global hierarchical letter stimuli of [Navon D. (1977). Forest before trees: The precedence of global features in visual perception. Cognitive Psychology, 9, 353-383] and the task was designed to parallel subsequent work in visual attention using Navon stimuli [Robertson, L. C. (1996). Attentional persistence for features of hierarchical patterns. Journal of Experimental Psychology: General, 125, 227-249; Ward, L. M. (1982). Determinants of attention to local and global features of visual forms. Journal of Experimental Psychology: Human Perception and Performance, 8, 562-581]. The results are discussed in terms of previous work in auditory attention and previous approaches to auditory local-global processing.

Adult↗
PubMed1990

Sparing of visual field perception in neonatal but not adult cerebral hemispherectomized cats. Relationship with oxidative metabolism of the superior colliculus.

Following cerebral hemispherectomy and using a lick-suppression test, adult-lesioned cats showed a complete contralateral hemianopsia, while neonatal-lesioned animals reliably responded to stimuli presented out to 45 degrees in the visual field contralateral to the lesion. In adult-lesioned cats oxidative metabolism of the superior colliculus ipsilateral to the hemispherectomy was markedly depressed as compared to the contralateral colliculus. In contrast, in the neonatal-lesioned cats this metabolic imbalance was mild. We propose that this ipsilateral depression of oxidative metabolism reflects the loss of excitatory corticotectal input which has been postulated as being partly responsible for the hemianopsia following a unilateral visual cortex ablation. Here we demonstrate, in addition, that this phenomenon is affected by developmental factors and suggest that differential age-at-lesion anatomical effects may also be involved.

Aging↗
PubMed1977

Laboratory apparatus for studying visual space perception of the pilot in simulated night approaches to landing.

The device provides a relatively inexpensive means of assessing a number of perceptual and human factors parameters in the night approach to landing situation. A technique for modeling airport runway lighting is described along with electromechanical and optical systems for precise control of simulated approach speed, model slant, and direction in the visual field of the simulated radial approach axis. The realism of this display is enhanced by preservation of the natural relations of size and brightness of simulated runway lights to distance.

Aerospace Medicine↗
PubMed2003

The neuropsychological effects of obstructive sleep apnea: a meta-analysis of norm-referenced and case-controlled data.

STUDY OBJECTIVES: The research literature on the neuropsychological effects of obstructive sleep apnea (OSA) has yielded seemingly contradictory findings, and narrative reviews of this literature are prone to interpretive errors. We used sophisticated meta-analytic models to minimize such errors, with the goal of clarifying the effect of OSA on neuropsychological functioning. DESIGN: Meta-analytic review of research through 2001. PARTICIPANTS: We reviewed studies of neuropsychological functioning among adults with untreated OSA. Twenty-five studies met review criteria, representing 1092 patients with OSA and 899 healthy controls. MEASUREMENTS AND RESULTS: Two sets of effect sizes were generated. One compared OSA group means against those of healthy controls in case-controlled studies. The other compared all OSA group means against published normative data. Within each data set, 10 neuropsychological outcome domains were coded. In both data sets, untreated OSA was found to have a negligible impact on intellectual and verbal functioning but a substantial impact upon vigilance and executive functioning. Data were mixed with regard to visual and motor functioning; posthoc inspection of the data suggested that tests of fine-motor coordination or drawing were more sensitive to OSA than were tests of fine-motor speed or visual perception. Data were also mixed with regard to memory functioning, probably related to methodologic differences across studies. CONCLUSIONS: Etiologic models should emphasize mechanisms known to affect vigilance, executive functioning, and motor coordination but not intelligence, verbal functioning, or visual perception. Clinicians should be alert to OSA symptoms in patients with declines in vigilance, executive functioning, or coordination.

Arousal↗
PubMed2004

Activation of the amygdala and anterior cingulate during nonconscious processing of sad versus happy faces.

Previous functional neuroimaging studies have demonstrated that the amygdala activates in response to fearful faces presented below the threshold of conscious visual perception. Using a backward masking procedure similar to that of previous studies, we used functional magnetic resonance imaging (fMRI) to study the amygdala and anterior cingulate gyrus during preattentive presentations of sad and happy facial affect. Twelve healthy adult females underwent blood oxygen level dependent (BOLD) fMRI while viewing sad and happy faces, each presented for 20 ms and "masked" immediately by a neutral face for 100 ms. Masked happy faces were associated with significant bilateral activation within the anterior cingulate gyrus and amygdala, whereas masked sadness yielded only limited activation within the left anterior cingulate gyrus. In a direct comparison, masked happy faces yielded significantly greater activation in the anterior cingulate and amygdala relative to identically masked sad faces. Conjunction analysis showed that masked affect perception, regardless of emotional valence, was associated with greater activation within the left amygdala and left anterior cingulate. Findings suggest that the amygdala and anterior cingulate are important components of a network involved in detecting and discriminating affective information presented below the normal threshold of conscious visual perception.

Adult↗
PubMed1978

Influence of set on perception.

To examine the role which preparatory set plays in visual perception three groups of undergraduates were presented 10 items displayed tachistoscopically in .125-sec exposures. The two experimental groups were each given a different preparatory set relevant to the content of the items. The third group, the control group, was given no preparatory set. Six of the 10 items displayed were ambiguous items which might be seen as belonging to either set. Although the two experimental groups perceived more items correctly than did the control group, an analysis of the responses indicated that preparatory set did influence perception. Each experimental group perceived three times as many items as belonging to its set as did the other group.

Female↗