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PubMedDate not supplied

Suppression of visual perception by magnetic coil stimulation of human occipital cortex.

Magnetic coil (MC) stimulation percutaneously of human occipital cortex was tested on perception of 3 briefly presented, randomly generated alphabetical characters. When the visual stimulus-MC pulse interval was less than 40-60 msec, or more than 120-140 msec, letters were correctly reported; at test intervals of 80-100 msec, a blur or nothing was seen. Shifting the MC location in the transverse and rostro-caudal axes had effects consistent with the topographical representation in visual cortex, but incompatible with an effect on attention or suppression from an eyeblink. The MC pulse probably acts by eliciting IPSPs in visual cortex. The neural activity subserving letter recognition is probably transmitted from visual cortex within 140 msec of the visual stimulus.

Humans↗
PubMed2003

Visual perception: shaping what we see.

A new psychophysical study has examined the free flow of perception as observers viewed stimuli with several possible visual interpretations. The results suggest that our subjective impression of such ambiguous patterns may be more closely linked to the brain's encoding of complex shape than previously appreciated.

Form Perception↗
PubMed1989

Neuronal correlates of subjective visual perception.

Neuronal activity in the superior temporal sulcus of monkeys, a cortical region that plays an important role in analyzing visual motion, was related to the subjective perception of movement during a visual task. Single neurons were recorded while monkeys (Macaca mulatta) discriminated the direction of motion of stimuli that could be seen moving in either of two directions during binocular rivalry. The activity of many neurons was dictated by the retinal stimulus. Other neurons, however, reflected the monkeys' reported perception of motion direction, indicating that these neurons in the superior temporal sulcus may mediate the perceptual experience of a moving object.

Action Potentials↗
PubMed2002

Test-retest reliability of the Motor-Free Visual Perception Test Revised (MVPT-R) in children with and without learning disabilities.

The Motor-Free Visual Perceptual Test Revised (MVPT-R) is an updated edition of the original test with the addition of four items and normative data for 9-11-year-old children. Test-retest reliability studies on the MVPT-R are not reported. The purpose of this paper is to report the test-retest reliability of the MVPT-R in children with and without learning disabilities. The MVPT-R was administered to 38 children with identified learning disabilities and 37 control children (aged 7-10 years) on two separate occasions within a 2.5 week window of time. Inter-rater reliability agreement between examiners was 99%. Intra-class correlations for perceptual quotient scores ranged from .63-.79 and perceptual age scores ranged from .69-.86. Pearson product moment correlations for perceptual quotient scores ranged from .70-.80 and perceptual age scores ranged from .77-.87. Results suggest moderate test-retest reliability for the MVPT-R with more stability in visual perceptual scores for children with learning disabilities. This information will be helpful for therapists using the MVPT-R as a descriptive measure for children.

Case-Control Studies↗