A motor signal and ?visual? size perception

Results from the development of a novel sensory and perceptual test to assess the level of altered visual size perception in people with schizophrenia are presented. Here we compare the performances in a visual sensory and perceptual test between a control group and an experimental group of people diagnosed with schizophrenia. We have been using paintings by Salvador Dalí and Rorschach plates to assess images size perception. In this transversal, ex-post-fact and quasi-experimental study we show differences between EG (Experimental Group) and CG (Control Group). Schizophrenics in-patients as compared to controls perceived sizes about 1.3 fold greater than healthy volunteers (p=0.006), thus showing that size perception is altered in schizophrenia. Together with previous results, this particular sensory test for size perception seems to be a useful assessment tool to evaluate the degree and severity of psychotic symptoms in prodromal schizophrenic states, and neuropsychiatric patients in general. It may help prevent acute crisis with proper, and most likely, lower dosages of medication.

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Size Discrimination with Low Spatial Frequencies

Perception ◽

10.1068/p110707 ◽

1982 ◽

Vol 11 (6) ◽

pp. 707-720 ◽

Cited By ~ 3

Author(s):

Robert A Smith

Keyword(s):

Fourier Spectrum ◽

Low Frequency ◽

Current Theory ◽

Size Perception ◽

Size Discrimination ◽

Low Frequencies ◽

Spatial Frequencies ◽

Vertical Bars ◽

The Fourier Transform ◽

Visual Size

The hypothesis that visual size is determined from the low-frequency Fourier spectrum of the image has been tested in a variety of ways. The fact that size discrimination of vertical bars is unimpaired when high spatial frequencies are filtered out of the image by blurring, and the fact that spatial-frequency adaptation alters perceived size, argue in favor of such hypothesis. However, the hypothesis is weakened by the observation that discrimination is also unimpaired by filtering low frequencies out of the image and by the observation that some manipulations which alter the Fourier transform produce no corresponding perceptual change. No current theory of size perception appears to fit all of these data.

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Changes in visual size perception in Schizophrenia and Depression

Revista Psicologia em Pesquisa ◽

10.34019/1982-1247.2020.v14.30411 ◽

2020 ◽

Vol 14 (4) ◽

pp. 140-153

Author(s):

Aline Mendes Lacerda ◽

Maria Lúcia De Bustamante Simas ◽

Geórgia Mônica Marques de Menezes

Keyword(s):

Visual Angle ◽

Size Perception ◽

Control Group ◽

Schizophrenia Group ◽

Depression Group ◽

Visual Size

The objective of this research was to measure possible changes in visual size perception of patients with depression and schizophrenia. Three groups were compared: Control Group (CG), Schizophrenia Group (SchG) and Depression Group (DepG). The diameter of the first figure seen by the participants in each painting was recorded in degrees of visual angle. The SchG perceived images 1.47 larger than CG and the DepG 1.28 larger than CG, whereas SchG selected images 1.15 larger than DepG, F (2, 57) = 17.677, p < .0001. These findings suggest there are changes in visual size perception related to depression and schizophrenia.

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Anodal Occipital Transcranial Direct Current Stimulation Enhances Perceived Visual Size Illusions

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01664 ◽

2020 ◽

pp. 1-8

Author(s):

Anqi Wang ◽

Lihong Chen ◽

Yi Jiang

Keyword(s):

Visual Cortex ◽

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Size Perception ◽

Central Target ◽

Direct Current Stimulation ◽

Visual Areas ◽

Early Visual Cortex ◽

Context Dependent ◽

Visual Size

Human early visual cortex has long been suggested to play a crucial role in context-dependent visual size perception through either lateral interaction or feedback projections from higher to lower visual areas. We investigated the causal contribution of early visual cortex to context-dependent visual size perception using the technique of transcranial direct current stimulation and two well-known size illusions (i.e., the Ebbinghaus and Ponzo illusions) and further elucidated the underlying mechanism that mediates the effect of transcranial direct current stimulation over early visual cortex. The results showed that the magnitudes of both size illusions were significantly increased by anodal stimulation relative to sham stimulation but left unaltered by cathodal stimulation. Moreover, the anodal effect persisted even when the central target and surrounding inducers of the Ebbinghaus configuration were presented to different eyes, with the effect lasting no more than 15 min. These findings provide compelling evidence that anodal occipital stimulation enhances the perceived visual size illusions, which is possibly mediated by weakening the suppressive function of the feedback connections from higher to lower visual areas. Moreover, the current study provides further support for the causal role of early visual cortex in the neural processing of context-dependent visual size perception.

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Front-Presented Looming Sound Selectively Alters the Perceived Size of a Visual Looming Object

Perception ◽

10.1177/0301006618777708 ◽

2018 ◽

Vol 47 (7) ◽

pp. 751-771 ◽

Cited By ~ 1

Author(s):

Daiki Yamasaki ◽

Kiyofumi Miyoshi ◽

Christian F. Altmann ◽

Hiroshi Ashida

Keyword(s):

Visual Stimulus ◽

Spatial Location ◽

The Body ◽

Size Perception ◽

Matching Task ◽

Visual Object ◽

Spatial Consistency ◽

Visual Size ◽

Size Adjustment ◽

Audiovisual Interaction

In spite of accumulating evidence for the spatial rule governing cross-modal interaction according to the spatial consistency of stimuli, it is still unclear whether 3D spatial consistency (i.e., front/rear of the body) of stimuli also regulates audiovisual interaction. We investigated how sounds with increasing/decreasing intensity (looming/receding sound) presented from the front and rear space of the body impact the size perception of a dynamic visual object. Participants performed a size-matching task (Experiments 1 and 2) and a size adjustment task (Experiment 3) of visual stimuli with increasing/decreasing diameter, while being exposed to a front- or rear-presented sound with increasing/decreasing intensity. Throughout these experiments, we demonstrated that only the front-presented looming sound caused overestimation of the spatially consistent looming visual stimulus in size, but not of the spatially inconsistent and the receding visual stimulus. The receding sound had no significant effect on vision. Our results revealed that looming sound alters dynamic visual size perception depending on the consistency in the approaching quality and the front–rear spatial location of audiovisual stimuli, suggesting that the human brain differently processes audiovisual inputs based on their 3D spatial consistency. This selective interaction between looming signals should contribute to faster detection of approaching threats. Our findings extend the spatial rule governing audiovisual interaction into 3D space.

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