Current Search: Visual perception -- Testing (x)
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- Title
- VISUAL CONCEPTS: PROTOTYPE ABSTRACTION AND SPECIFIC REPRESENTATION.
- Creator
- TROMLEY, CHERYL LYNN., Florida Atlantic University
- Abstract/Description
-
Prototype abstraction and specific representations were examined using two acquisition procedures (paired-associate and concept formation) for concept members generated by applying one of two distortion rules (form preserving and form destroying) to eight-dot base patterns. One distortion rule maximized the configurational similarity between concept members and minimized their elemental similarity (form preserving). The other maximized the elemental similarity between concept members and...
Show morePrototype abstraction and specific representations were examined using two acquisition procedures (paired-associate and concept formation) for concept members generated by applying one of two distortion rules (form preserving and form destroying) to eight-dot base patterns. One distortion rule maximized the configurational similarity between concept members and minimized their elemental similarity (form preserving). The other maximized the elemental similarity between concept members and minimized their configurational similarity (form destroying). Either immediately following acquisition or after a two-week delay, subjects were given a classification test which included the concept members learned during acquisition and novel members of the concepts. Evidence for prototype abstraction was found only for form preserving concepts. This result was interpreted as evidence for the configurational nature of a prototypical representation. Evidence for long-term retention of specific representations was found only for form destroying concepts. This result was explained by a model involving a network of partially overlapping features.
Show less - Date Issued
- 1978
- PURL
- http://purl.flvc.org/fcla/dt/13941
- Subject Headings
- Visual perception--Testing, Concepts, Abstraction
- Format
- Document (PDF)
- Title
- Functional consequences of top-down anticipatory modulation of primary visual cortex.
- Creator
- Richter, Craig G., Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
- Abstract/Description
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It is well established that anticipation of the arrival of an expected stimulus is accompanied by rich ongoing oscillatory neurodynamics, which span and link large areas of cortex. An intriguing possibility is that these dynamic interactions may convey knowledge that is embodied by large-scale neurocognitive networks from higher level regions of multi-model cortex to lower level primary sensory areas. In the current study, using autoregressive spectral analysis, we establish that during the...
Show moreIt is well established that anticipation of the arrival of an expected stimulus is accompanied by rich ongoing oscillatory neurodynamics, which span and link large areas of cortex. An intriguing possibility is that these dynamic interactions may convey knowledge that is embodied by large-scale neurocognitive networks from higher level regions of multi-model cortex to lower level primary sensory areas. In the current study, using autoregressive spectral analysis, we establish that during the anticipatory phase of a visual discrimination task there are rich patterns of coherent interaction between various levels of the ventral visual hierarchy across the frequency spectrum of 8 - 90 Hz. Using spectral Granger causality we determined that a subset of these interactions carry beta frequency (14 - 30 Hz) top-down influences from higher level visual regions V4 and TEO to primary visual cortex. We investigated the functional significance of these top-down interactions by correlating the magnitude of the anticipatory signals with the amplitude of the visual evoked potential that was elicited by stimulus processing. We found that in one third of the extrastriate-striate pairs, tested in three monkeys, the amplitude of the visual evoked response is well predicted by the magnitude of pre-stimulus coherent top-down anticipatory influences. To investigate the dynamics of the coherent and topdown Granger causal interactions, we analyzed the relationship between coherence and top-down Granger causality with stimulus onset asynchrony. This analysis revealed that in an abundance of cases the magnitudes of the coherent interactions and top-down directional influences scaled with the length of time that had elapsed before stimulus onset., Together these results reveal a complex network of coherent and top-down directional interactions that predict the amplitude of early components of the visual evoked potential in primary visual cortex and vary in strength on the basis of the length of the stimulus onset.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/369200
- Subject Headings
- Cognitive neuroscience, Brain mapping, Visual perception, Testing, Intersensory effects
- Format
- Document (PDF)
- Title
- Investigation of human visual spatial attention with fMRI and Granger Causality analysis.
- Creator
- Tang, Wei, Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
- Abstract/Description
-
Contemporary understanding of human visual spatial attention rests on the hypothesis of a top-down control sending from cortical regions carrying higher-level functions to sensory regions. Evidence has been gathered through functional Magnetic Resonance Imaging (fMRI) experiments. The Frontal Eye Field (FEF) and IntraParietal Sulcus (IPS) are candidates proposed to form the frontoparietal attention network for top-down control. In this work we examined the influence patterns between...
Show moreContemporary understanding of human visual spatial attention rests on the hypothesis of a top-down control sending from cortical regions carrying higher-level functions to sensory regions. Evidence has been gathered through functional Magnetic Resonance Imaging (fMRI) experiments. The Frontal Eye Field (FEF) and IntraParietal Sulcus (IPS) are candidates proposed to form the frontoparietal attention network for top-down control. In this work we examined the influence patterns between frontoparietal network and Visual Occipital Cortex (VOC) using a statistical measure, Granger Causality (GC), with fMRI data acquired from subjects participated in a covert attention task. We found a directional asymmetry in GC between FEF/IPS and VOC, and further identified retinotopically specific control patterns in top-down GC. This work may lead to deeper understanding of goal-directed attention, as well as the application of GC to analyzing higher-level cognitive functions in healthy functioning human brain.
Show less - Date Issued
- 2011
- PURL
- http://purl.flvc.org/FAU/3334101
- Subject Headings
- Attention, Physiological aspects, Cognitive neuroscience, Brain, Magnetic resonance imaging, Sensorimotor integration, Movement sequences, Human information processing, Cognitive psychology, Visual perception, Testing
- Format
- Document (PDF)