The knowledge used in vision and where it comes from

Barlow, H. B.

doi:10.1098/rstb.1997.0097

Cited by 47 publications

(44 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although most studies implicate atypicalities in early visual function as the source of these differences, some authors argue that certain illusions rely on some form of top-down processing (40,41), a claim that has been contested (42,43). Critically, however, most researchers agree that these visual illusions can be explained by processes within the visual system, rather than by influences on visual function from higherlevel knowledge areas outside the visual system.…”

Section: Discussionmentioning

confidence: 86%

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

Teufel

Subramaniam

Dobler

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

236

240

View full text Add to dashboard Cite

Many neuropsychiatric illnesses are associated with psychosis, i.e., hallucinations (perceptions in the absence of causative stimuli) and delusions (irrational, often bizarre beliefs). Current models of brain function view perception as a combination of two distinct sources of information: bottom-up sensory input and top-down influences from prior knowledge. This framework may explain hallucinations and delusions. Here, we characterized the balance between visual bottom-up and top-down processing in people with early psychosis (study 1) and in psychosis-prone, healthy individuals (study 2) to elucidate the mechanisms that might contribute to the emergence of psychotic experiences. Through a specialized mental-health service, we identified unmedicated individuals who experience early psychotic symptoms but fall below the threshold for a categorical diagnosis. We observed that, in early psychosis, there was a shift in information processing favoring prior knowledge over incoming sensory evidence. In the complementary study, we capitalized on subtle variations in perception and belief in the general population that exhibit graded similarity with psychotic experiences (schizotypy). We observed that the degree of psychosis proneness in healthy individuals, and, specifically, the presence of subtle perceptual alterations, is also associated with stronger reliance on prior knowledge. Although, in the current experimental studies, this shift conferred a performance benefit, under most natural viewing situations, it may provoke anomalous perceptual experiences. Overall, we show that early psychosis and psychosis proneness both entail a basic shift in visual information processing, favoring prior knowledge over incoming sensory evidence. The studies provide complementary insights to a mechanism by which psychotic symptoms may emerge.visual perception | psychosis | top-down processing | predictive coding | schizophrenia

show abstract

Section: Discussionmentioning

confidence: 86%

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

Teufel

Subramaniam

Dobler

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

236

240

View full text Add to dashboard Cite

show abstract

“…(Barlow (1997) takes a more`reductionist' view, preferring to think of this in terms of redundancies of bottom-up signals from the eyes. I would limit this to very general features, such as properties of edge-signalling giving contrast e¡ects, rather than phenomena attached to particular objects or particular classes of objects, such as faces.)…”

Section: T H E Hol Low Fac Ementioning

confidence: 99%

Knowledge in perception and illusion

Gregory

1997

Phil. Trans. R. Soc. Lond. B

420

259

View full text Add to dashboard Cite

Following Hermann von Helmholtz, who described visual perceptions as unconscious inferences from sensory data and knowledge derived from the past, perceptions are regarded as similar to predictive hypotheses of science, but are psychologically projected into external space and accepted as our most immediate reality. There are increasing discrepancies between perceptions and conceptions with science's advances, which makes it hard to define ‘illusion’. Visual illusions can provide evidence of object knowledge and working rules for vision, but only when the phenomena are explained and classified. A tentative classification is presented, in terms of appearances and kinds of causes. The large contribution of knowledge from the past for vision raises the issue: how do we recognize the present, without confusion from the past. This danger is generally avoided as the present is signalled by real–time sensory inputs— perhaps flagged by qualia of consciousness.

show abstract

“…green (Barlow & Fo« ldia¨k 1989). In principle, this mechanism of adaptation to contingencies could explain a wide variety of perceptual phenomena (Barlow 1997).…”

Section: Introductionmentioning

confidence: 99%

Adaptation to contingencies in macaque primary visual cortex

Carandini

Barlow

O’Keefe

et al. 1997

Phil. Trans. R. Soc. Lond. B

Self Cite

View full text Add to dashboard Cite

We tested the hypothesis that neurons in the primary visual cortex (V1) adapt selectively to contingencies in the attributes of visual stimuli. We recorded from single neurons in macaque V1 and measured the e¡ects of adaptation either to the sum of two gratings (compound stimulus) or to the individual gratings. According to our hypothesis, there would be a component of adaptation that is speci¢c to the compound stimulus. In a ¢rst series of experiments, the two gratings di¡ered in orientation. One grating had optimal orientation and the other was orthogonal to it, and therefore did not activate the neuron under study. These experiments provided evidence in favour of our hypothesis. In most cells adaptation to the compound stimulus reduced responses to the compound stimulus more than it reduced responses to the optimal grating, and the responses to the compound stimulus were reduced more by adaptation to the compound stimulus than by adaptation to the individual gratings. This suggests that a component of adaptation was speci¢c to (and caused by) the simultaneous presence of the two orientations in the compound stimulus. To test whether V1 neurons could adapt to other contingencies in the stimulus attributes, we performed a second series of experiments, in which the component gratings were parallel but di¡ered in spatial frequency, and were both e¡ective in activating the neuron under study. These experiments failed to reveal convincing contingent e¡ects of adaptation, suggesting that neurons cannot adapt equally well to all types of contingency.

show abstract

The knowledge used in vision and where it comes from

Cited by 47 publications

References 28 publications

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

Knowledge in perception and illusion

Adaptation to contingencies in macaque primary visual cortex

Contact Info

Product

Resources

About