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Matthews, J. (1994). Neurobiology of Visual Perception: Some Reflections on Visual Awareness. F. Crick and C. Koch. Cold Spring Harbor Symposium on Quantitative Biology. LV, 1990. Pp. 953-962.. Psychoanal Q., 63:395-396.
Psychoanalytic Electronic Publishing: Neurobiology of Visual Perception: Some Reflections on Visual Awareness. F. Crick and C. Koch. Cold Spring Harbor Symposium on Quantitative Biology. LV, 1990. Pp. 953-962.
As described above, clusters of neurons responding to the same stimulus tend to exhibit phase-locked synchronized oscillatory activity at 40-60 Hz. (Subsequent reports have shown that this effect can occur over large cortical distances, between cortical areas, and even between cerebral hemispheres.) The authors speculate that the synchronization of activity in widely distributed cell assemblies serves to "bind" the perceptual image and create the experience of "vivid visual awareness." In developing this theory, they correlate the neurobiological data to psychophysiological data on visual processing. Visual perception has traditionally been broken into two phases, an initial rapid parallel processing, thought to reflect "hard wired" analysis of simple features and elements, followed by a slower serial phase of analysis. The former process does not elicit "vivid awareness." However, in the latter phase, termed "focal attention," selected aspects of the visual scene are interpreted
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using constraints which are built into the neural system by both genetics and experience. It is proposed that this process of neural "computation" results in the establishment of phase-locked oscillation in a distributed cell assembly.
Since synaptic linkages reflect genetic programming, epigenetic shaping, and experience-based modulations, the probability that a particular functional cell assembly will emerge depends on both the stimulus characteristics and past experience. When the visual scene is ambiguous, rival sets of neurons set up competing oscillations, and the "strongest" (highest amplitude, most coherent) oscillation "wins." Others have previously suggested the existence of a topographic "saliency map" within the visual system which guides attentional focus within the visual field. "Saliency" here is a broad term; a visual stimulus may be salient as a result of lower level features such as motion, or as a reflection of higher level search for more complex features. The presence of salient features may "spotlight" certain aspects of the visual scene by facilitating the formation of coherent oscillation, thus favoring certain perceptions. (Extending this notion of saliency, one might also imagine that the affective valence of certain features could contribute to the establishment of attentional focus, and could either favor or inhibit perception. Such a mechanism would allow for selective perception based on psychodynamic principles.)
Finally, the authors propose that the coherent oscillatory activity activates "working memory," which holds a trace of the perceived image for several seconds after the oscillation (and vivid awareness) has ceased. This working memory may depend on persistent nonoscillatory activity within the subset of distributed neurons, transient synaptic modification, or both. When the distributed oscillation ceases, the core neuronal set will have a decreased threshold for reactivation, facilitating the reestablishment of coherent oscillation and thus the re-emergence of vivid visual awareness. (Although working memory lasts only a few seconds, a similar but more persistent effect could explain the ubiquity of "day residue" in nocturnal dream images.)
These speculations suggest mechanisms for visual selective attention and subjectivity. Some aspects of visual perception are expected to be highly accurate because of the continuous feedback corrections and adaptive pressures. However, more ambiguous situations, such as visual aspects of social cues, are subject to varied interpretations, and the dominantinterpretation depends on individual experience. The perceptual world is internally created through the lens of personal history, as is continuously confirmed in psychoanalytic experience.
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Matthews, J. (1994). Neurobiology of Visual Perception. Psychoanal. Q., 63:395-396