Background Schizophrenia is associated with perceptual organization deficits and abnormal neuronal connectivity has been described in early visual areas. The purpose of this study was to investigate the functional integrity of lateral connections in early visual areas of patients with schizophrenia and type I bipolar disorder with a history of psychosis. Method Twenty-four out-patients with schizophrenia, 22 out-patients with bipolar disorder, and 20 healthy control subjects participated in the study. Using a computer-assisted psychophysical test, contrast thresholds were measured for centrally presented target stimuli (Gabor patches), which were surrounded by two collinear flankers. Target-to-flanker distances were 0, 1, 2, 3, 4, 6, 9 and 122. Psychophysical measures were contrast threshold changes at each target-to-flanker distance compared with baseline thresholds determined for isolated targets with no flankers. Clinical measures included IQ, positive, negative, and depressive symptoms. Results. In patients with schizophrenia, flankers did not facilitate contrast detection for target stimuli at 2-6 lambda distances compared to controls [effect size (Cohen's d): 1.25-1.42]. The inhibitory effect of flankers (0 and 1lambda) and contrast thresholds in the absence of flankers were spared. Patients with bipolar disorder did not differ from the controls. Medicated and non-medicated patients displayed similar performances. Positive and negative symptoms and depression did not correlate with contrast threshold values. Conclusions Excitatory lateral connections in early visual cortex are specifically impaired in patients with schizophrenia, which may contribute to perceptual disorders such as unclear seeing, partial or skewed sight, disrupted rectilinearity, and abnormal figure-ground segregation.

Lateral interactions in the visual cortex of patients with schizophrenia and bipolar disorder.

The ability to integrate sensation with action is considered an important factor underlying the development of upright stance and locomotion. While many have studied sensory influences on posture, the nature of these influences and how they change with development have yet to be thoroughly characterized in infancy. Six infants were examined from 1 month prior to walk onset until 9 months of independent walking experience while standing quietly and touching either a static or a dynamic surface. Five adults were examined performing an analogous task. An event-related, time-frequency analysis was used to assess the relationship between postural sway and the motion of the somatosensory stimulus. Phase consistency between sway and stimulus was observed for both adults and infants, and with walking experience the infants increased their phase consistency rather than changing aspects of response amplitude. It is concluded that walking experience provides opportunities for an active tuning of sensorimotor relations for adequate estimation of body position in space and thus facilitates refined control over temporal aspects of postural sway.

Development of somatosensory-motor integration: an event-related analysis of infant posture in the first year of independent walking.

Psychophysical thresholds and neuronal responses for isolated stimuli are strongly modified by nearby stimuli in the visual field We studied the orientation and position specificity of these contextual interactions using a dual-frequency visual-evoked potential technique in developing human infants and adults One set of small, oriented stimulus elements (targets) was tagged with a temporal frequency f 1 of 452 Hz The addition of an abutting second set of similar patches (flankers) tagged at f 2 = 258 Hz had three effects: (1) The flankers reduced the second and fourth harmonic responses to the targets This reduction was independent of flanker orientation or position and age (2) The response to the combination of targets and flankers also contained nonlinear interaction terms (1 f 1 ± 1 f 2 ) that were tuned for flanker orientation and position in adults, but only for flanker orientation in infants 8-31 weeks of age (3) Nonlinear interaction terms recorded at 2 f 1 ± 2 f 2 were large and untuned for flanker orientation and position in adults but were nearly absent in the youngest infants The three forms of nonlinear interaction, thus, have differences in sensitivity to flanker orientation and position and differential growth trends, indicating that they are generated by different mechanisms These three forms of interaction could serve different functional roles The first process provides a nonselective gain control that is fully functional in early infancy The second process, which develops slowly, is selective for the specific form of the stimuli The third process, which is also immature, pools across orientation

https://www.jneurosci.org/content/jneuro/23/25/8630.full.pdf

Development of the Spatial Organization and Dynamics of Lateral Interactions in the Human Visual System

It has been known for more than a century that even slight hypoxemia reduces dark adaptation. We studied dark adaptation in symptomatic carotid artery disease. Twenty-one consecutive patients scheduled for first-time carotid endarterectomy and 31 age-matched control subjects with normal carotid arteries were examined by dark adaptometry monocularly and were tested repeatedly on consecutive days. The average degree of internal carotid stenosis on the symptomatic side was much greater than that on the contralateral side. Dark adaptation was markedly impaired in the patients as compared with the control subjects. In the patients there was no difference in dark adaptation between the symptomatic and nonsymptomatic sides. The existence of carotid stenosis correlated to the level of dark adaptation. Pupillary size and age correlated to the dark adaptational level but did not affect the effect of carotid stenosis on dark adaptation. The decreased dark adaptation may be due to insufficient blood supply or repeated subclinical microembolization to the retinae, the brain, or both.

I. Impaired dark adaptation in symptomatic carotid artery disease

Spatial-frequency-tuned channels in early infancy: VEP evidence

The development of lateral inhibitory interactions in the infant visual system, as reflected by the visual-evoked potential (VEP), was studied using a radial, asymmetrical windmill-dartboard stimulus. This contrast-reversing stimulus generates VEP responses with a strong fundamental frequency component and an attenuated second harmonic component (relative to that obtained using a symmetrical stimulus). These two harmonic components reflect distinct phenomena, and appear to be the result of short-range (the fundamental) and long-range (attenuated second harmonic) lateral inhibitory interactions elicited by differential luminance-modulation of contiguous spatial regions. We studied the development of the short-and long-range interactions at 100% and 30% contrast in human infants using both VEP amplitude and phase measures. Attenuation of the second harmonic (long-range interactions) was adult-like by 8 weeks of age while the strength of the fundamental (short-range interactions) was adult-like by 20 weeks suggesting a differential development of long-range and short-range interactions. In contrast, corresponding phase data indicated significant immaturities at 20 weeks of age for both the short-and long-range components.

Development of lateral interactions in the infant visual system.

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Development of lateral interactions in the infant visual system.