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Results for “VISUAL PERCEPTION”

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At least 73 records · Page 4Linked to original sources
PubMed1993

Functional cortical interaction patterns in visual perception and visuospatial problem solving.

To explore the integration of functional neuronal interactions in human higher cortical functions, we applied multivariate mathematical techniques to regional cerebral blood flow (rCBF) increases induced by mental activity. rCBF was measured using the intravenous xenon-133 clearance technique with 32 bihemispheric detectors in 84 normal volunteers at rest and during both a visuoperceptual accuracy task and a visuospatial problem solving task. Both paradigms activated rCBF in bilateral premotor, motor and postcentral regions. Bilateral prefrontal activation occurred during problem solving but not during the perceptual accuracy task. Partial correlations coefficients and factor analysis identified significant interactions between numerous cortex regions in both tasks. There were highly ordered and integrated patterns of functional interaction patterns between cortex areas subserving elementary subfunctions of complex behavior. Cortical interaction analysis by such techniques is a useful tool to describe the functional anatomy of large-scale neurocognitive networks in the intact human brain. Imaging functional interactions between active cortex areas are complementary to other experimental neurophysiologic methods to explore brain-behavior relationships in health and disease.

Adolescent↗
PubMed1996

Frontal gamma-band enhancement during multistable visual perception.

The aim of our study was to find out whether an increase in the gamma band may be related to the reversal phase during viewing of an ambiguous pattern. The present study describes the significant gamma band (30-50 Hz) activity increase in EEG during states of perceptual switching (reversal state). In our experiments the multistability was induced with an ambiguous stimulus pattern, known as stroboscopic alternative motion (SAM). The investigations carried out in 11 subjects included a measuring strategy with three different experimental conditions: (1) recording of spontaneous EEG as baseline; (2) recording of the EEG during naive observation of the ambiguous pattern; (3) recording of EEG during active observation of SAM. The results indicate that the multistable perception is one of the multifold cognitive processes giving rise to 40 Hz enhancement in the entire cortex. The most significant 40 Hz enhancements were measured in frontal areas and can reach increases of 40 to 50% in states of naive and active observations of SAM, respectively, in comparison to spontaneous EEG recordings. The results indicate that the increase of frontal gamma band is related to the destabilization of the perceptual system when viewing multistable patterns.

Adolescent↗
PubMed1983

Response tempo and separable--integral responding: evidence for an integral-to-separable processing sequence in visual perception.

Three experiments were conducted to examine the relation between response tempo and separable-integral responding. A restricted classification paradigm, in which similarity-based (integral) and dimensionally based (separable) classifications were pitted against one another, was used with the dimensions of length and density (all experiments) and size and brightness (Experiment 3). The subjects were college students (Experiments 1 and 2) and kindergarten, second-, and fifth-grade children (Experiment 3). In all three experiments, rapid responding was associated with fewer dimensional and more similarity responses than was slow responding. This result held when response tempo was simply measured (Experiments 1 and 3) and when it was manipulated by the experimenter (Experiment 2). The results were interpreted to be consistent with models of dimensional processing in which holistic, integral processing precedes analytic dimensional processing.

Child↗
PubMed2005

Confusion and compensation in visual perception: effects of spatiotemporal proximity and selective attention.

The authors investigated spatial, temporal, and attentional manipulations in a short-term repetition priming paradigm. Brief primes produced a strong preference to choose the primed alternative, whereas long primes had the opposite effect. However, a 2nd brief presentation of a long prime produced a preference for the primed word despite the long total prime duration. These surprising results are explained by a computational model that posits the offsetting components of source confusion (prime features are confused with target features) and discounting (evidence from primed features is discounted). The authors obtained compelling evidence for these components by showing how they can cooperate or compete through different manipulations of prime salience. The model allows for dissociations between prime salience and the magnitude of priming, thereby providing a unified account of "subliminal" and "supraliminal" priming.

Attention↗