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At least 793 records · Page 44Linked to original sources
PubMed1988

Effects of lateral displacement of the visual field on the development of visual-motor abilities in cats.

In this study, we test the flexibility of the cat's visual system by examining the visual-motor effects of both moderate and extreme lateral displacement of the visual field. While being reared with masks that provided either 0, 15, or 30 diopters lateral displacement of the visual field, 23 kittens received 3 tests of visual-motor abilities: a visual cliff task, a visual guiding task, and a five-alley choice task. No significant differences were found among the 0, 15, or 30 diopter displacement groups for any of the 3 tasks for either the total number of days to reach criterion performance, for the development of performance over time during the early days of testing, or for the development over time to criterion performance. After reaching criterion, kittens readapted to transposed conditions of displacement. The group changed 30 diopters did significantly worse than the group changed 15 diopters, both in error scores and in time to criterion performance. The present results with kittens are compared to those of other investigators and suggestions are made for future research.

Aging↗
PubMed2006

Mirror exposure for the treatment of body image disturbance.

OBJECTIVE: Body image disturbance is a risk factor for the development and persistence of eating disorders. Limitations of current treatments for body image disturbance prompted the development of a mirror exposure (ME) treatment. METHOD: ME involves deliberate, planned, and systematic exposure to body image. The approach is nonjudgmental, holistic in focus, and mindful of present emotional experience. Complementary behavioral assignments aim to reduce avoidance and excessive checking. The current study evaluated the effectiveness of ME therapy (in a three-session format) compared with a nondirective (ND) therapy for 45 women with extreme weight and shape concerns. RESULTS: ME resulted in significant improvements at termination and follow-up in body checking and avoidance, weight and shape concerns, body dissatisfaction, dieting, depression, and self-esteem. As hypothesized, ME was significantly better than ND on many of the outcome measures. CONCLUSION: ME is an effective treatment for body image disturbance and should be evaluated in the context of treatments for eating disorders.

Adolescent↗
PubMed2003

An artist's view of drug-induced hallucinosis.

The occurrence of hallucinations in patients with Parkinson's disease is often related to antiparkinsonian therapy, but other factors such as cognitive decline and sleep-cycle disturbances are thought to contribute. We describe an artist who depicted her visual hallucinations experienced in the course of Parkinson's disease.

Amantadine↗
PubMed2004

Impaired modulation of the vestibulo-ocular reflex in Huntington's disease.

The vestibulo-ocular reflex (VOR) stabilizes gaze during movement, in conjunction with other afferent information: visual, proprioceptive, and somaesthetic. The reflex can either be augmented or suppressed, depending on visual requirements, and undergoes long-term adaptation to compensate for physical changes in the subject. Importantly, over relatively short periods of time, the VOR should function consistently under the same circumstances. This study examines VOR function in patients with Huntington's disease (HD), with a view to investigating cortical influences on the reflex. Horizontal eye movements were recorded in 9 patients with HD and 7 normal subjects, using the scleral search coil technique, in response to high frequency, unpredictable head rotations imposed manually. To establish base VOR function, recordings were made in darkness, without instruction, before and after wearing x2 magnifying lenses for a period of 2 hours to adapt the reflex. Recordings were also made before adaptation, while fixating a stationary visual target (VOR augmentation), and while fixating a target moving with the head (VOR suppression). Although results suggest that the VOR is preserved in HD, with relatively normal gain values and appropriate augmentation and suppression of the reflex with visual input, patients were unable to adapt the VOR to altered visual conditions. This represents a novel finding in HD and suggests that cortical structures compromised in HD exert influences on the long-term adaptation of the VOR.

Adult↗
PubMed1997

Perception of spatial orientation in spasmodic torticollis. Part 2: The visual vertical.

Twenty-nine patients with idiopathic spasmodic torticollis (ST) and matched normal control subjects were asked to align a target line to perceived earth vertical [visual vertical (VV)]. Settings were made against a whole-field random-dot background that was either stationary or rotating around the line of sight, and subjects performed the task upright and lying horizontally on their sides. Normal subjects were tested both head upright and after assuming a voluntary head tilt. Patients with ST set the VV close to true upright with a minimal deviation toward tilt of the head in contrast to normal subjects assuming a head tilt who set the VV in the opposite direction to the head tilt (Müller "E" effect). Settings against the spinning disk were biased in the direction of rotation similarly for both subject groups. Settings made against static or spinning disk performed when subjects lay horizontally were tilted in the direction of recumbence (Aubert "A" effect) similarly for both subject groups. When attempting to set the target line parallel to the long axis of the face, patients with head tilt set the line to upright, whereas normal subjects correctly estimated their tilts. One hypothesis offered to explain these results is that the patients referenced only their upright trunk for vertical and did not make use of neck proprioceptive or vestibular signals of head tilt so that all settings were made as if the trunk and head were upright. Alternatively, patients may have used only otolith signals as the reference for upright, and these are recalibrated in ST patients with head tilt. The pathological deviation becomes accepted as upright posture, and VVs and facial orientation are estimated as if the head were upright. In either case the findings indicate abnormal processing of the perception of visual verticality in ST patients.

Adult↗
PubMed1988

Dynamic stereoacuity: a comparison of electrophysiological and psychophysical responses in normal and stereoblind observers.

We compared stereoscopic thresholds determined psychophysically and by using visually evoked potentials in normal adult and stereoblind subjects. For normal observers there was a strong linear relationship between visual evoked potential amplitude and disparity (r = 0.86 on average). However, stereoblind observers' responses showed no relationship to disparity (r = 0.18 on average). For normal observers, log visual evoked potential stereo thresholds determined by an extrapolation procedure were on average within 0.17 octaves of the psychophysically determined log thresholds. They did not differ significantly from psychophysical thresholds, and they correlated significantly with behavioral thresholds (r = 0.86).

Adult↗
PubMed1993

Correction processes in early reaching: reaches by infants to prismatically displaced targets.

A comparison was made between trajectories of reaches to visual targets by 6-months-old infants, with and without lateral prismatic displacement. In the No Prism condition, the major element of the movement veered towards the target, confirming the results of Mathew and Cook (1990). In the Prism condition, the prism did not affect hand position or movement direction at the beginning of the major element, but a lateral displacement was evident by the end of the element. This is taken as evidence that shifts in trajectory during the element were not due to visual guidance. It is suggested instead that these shifts may reflect correction based upon somatic feedback about position in relation to the visually specified goal of the movement. Evidence that the hand approached the virtual target supports the suggestion that any visual guidance was confined to the approach phase of the reach. Nevertheless, it appears that visual guidance was operating at this stage, since movement direction was displaced away from the virtual target and towards the real target.

Attention↗
PubMed1992

Apparent distance reduction with moving stimuli (Tandem Effect): evidence for an attention-shifting model.

When two vertical rods move through a horizontal window in close succession, the Tandem Effect can be observed. It consists of a spatial illusion (distance between the rods looking smaller than it actually is) and a temporal illusion (under certain conditions both rods are seen simultaneously in the window, though the first rod has left the window before the second rod enters it). We report six experiments that explored the distance-reduction illusion and tested an attentional model of the effect. It assumes that attention is initially focused on the first rod and then shifted to the second, when it enters the window. The percept of the pair of rods is integrated from the first rod's position at the beginning, and the second rod's position at the end, of the focus shift. Consequently their subjective distance will be smaller than their physical distance by the distance that they travel during the focus shift. Experiments 1 and 2 established the Tandem Effect as an empirical phenomenon and showed that its size depends on stimulus parameters such as window size and movement speed. Experiments 3-5 tested specific predictions from the attentional model. Experiment 6 examined a further illusion, the Fröhlich Effect, and showed that it can be subsumed under the model. The experiments produced some unexpected effects and some predictions from the model were only partly confirmed. It is shown that the main findings can be combined into two quantitative functions that describe the course of focusing. One implication is that visual attention does not "move" from one object to another; rather all attention shifts originate in the fovea. We discuss several alternative interpretations of our data and show that they are less satisfactory than the attentional model.

Adult↗
PubMed1975

Multiple response to sound in dysfunctional children.

Methods and findings derived from over a decade of linguistic-kinesic microanalysis of sound films of human behavior were appled to the analysis of sound films of 25 dysfunctional children. Of the children, 17 were markedly dysfunctional (autistic-like) while 8 had milder reading problems. All of these children appeared to respond to sound more than once: when it actually occurred and again after a delay ranging from a fraction of a second up to a full second, depending on the child. Most of the children did not seem to actually hear the sound more than once; however, there is some indication that a few children may have done so. Evidence was also found suggesting a continuum from the longer delay of autistic-like children to the briefer delay of children with reading problems.

Auditory Perception↗