Stereopsis and magnocellular sensitivity in schizophrenia

Skottun, Bernt C.; Skoyles, John R.

doi:10.1080/15622970701849945

Cited by 10 publications

(4 citation statements)

References 57 publications

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“…However, these methods have problems associated with them. [4][5][6] Recently, Green et al 7 have argued for the use of steady-state visually evoked potentials (ssVEPs) to magnocellular-and parvocellular-biased stimuli to investigate the sensitivity of magnocellular and parvocellular systems in schizophrenic subjects. We here comment on the main assumptions behind this proposal.…”

Section: Introductionmentioning

confidence: 99%

On Identifying Magnocellular and Parvocellular Responses on the Basis of Contrast-Response Functions

Skottun¹,

Skoyles

2010

Schizophrenia Bulletin

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It has been proposed that magnocellular and parvocellular sensitivity in schizophrenic individuals can be assessed using steady-state visually evoked potentials (VEPs) to either low-contrast stimuli or stimuli whose contrast is modulated around a high contrast "pedestal" (Green MF, Butler PD, Chen Y, et al. Schizophr Bull. 2009;35:163-181). This suggestion faces 2 difficulties: (1) To use low-contrast stimuli to activate the magnocellular system is inconsistent with lesion studies that have shown that under many conditions, the parvocellular system responds to the lowest contrasts and (2) To rely on contrast-response relationships to identify magnocellular and parvocellular responses is difficult because other neurons exist in the visual system that have contrast-response relationships similar to those of magnocellular and parvocellular cells.

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Section: Introductionmentioning

confidence: 99%

On Identifying Magnocellular and Parvocellular Responses on the Basis of Contrast-Response Functions

Skottun¹,

Skoyles

2010

Schizophrenia Bulletin

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“…The other nine patients all displayed a higher absolute difference between the eyes, making this index potentially useful as a clinical parameter for identifying disturbances in contrast sensitivity and/or binocular interactions that arise from developmental or psychiatric disorders. 64,65 Second, patients and controls differed in their overall pattern shown both in dichoptic ASD and dominant eye DSD values. Despite the group differences, all individuals lay along a continuum on the plane determined by these variables, with only a slight overlap between groups, which was again mostly accounted for by the previous binocular treatment (three of four).…”

Section: Discussionmentioning

confidence: 99%

Dichoptic Spatial Contrast Sensitivity Reflects Binocular Balance in Normal and Stereoanomalous Subjects

Barboni

Maneschg

Németh

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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To study binocular balance by comparing dichoptic and standard monocular contrast sensitivity function (CSF) in stereonormal and stereoanomalous/stereoblind amblyopic subjects. METHODS. Sixteen amblyopes and 17 controls participated. Using the capability of the passive three-dimensional display, we measured their CSF both monocularly and dichoptically at spatial frequencies 0.5, 1, 2, 4, and 8 cpds using achromatic Gabor patches on a luminance noise background. During monocular stimulation, the untested eye was covered, while for the dichoptic stimulation the untested eye viewed background noise. Dichoptic CSF of both eyes was acquired within one block. RESULTS. In patients with central fixation, dichoptic viewing had a large negative impact on the CSF of the amblyopic eye, although it hardly affected that of the dominant eye. In contrast, dichoptic viewing had a small but significant effect on both eyes for controls. In addition, all participants lay along a continuum in terms of how much their two eyes were affected by dichoptic stimulation: by using two predefined contrast sensitivity ratios, namely, amblyopic sensitivity decrement and dichoptic sensitivity decrement, not only did we find a significant correlation between these variables among all participants, but also the two groups were identified with minimum error using a cluster analysis. CONCLUSIONS. Dichoptic CSF may be considered to measure visual performance in patients with altered binocular vision, because it better reflects the visual capacity of the amblyopic eye than the standard monocular examinations. It may also be a more reliable parameter to assess the efficacy of modern approaches to treat amblyopia.

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“…In addition, many of the tests used to assess magnocellular sensitivity in schizophrenia are not well suited to this task. This applies, for instance, to stereoacuity (Schechter et al 2006) which appears to be more closely linked to the parvocellular than the magnocellular system (Skottun and Skoyles 2009b). Also, to take deficiencies in motion perception as evidence for a magnocellular deficit, as does Javitt (2009), is problematic since discrimination of direction and speed can be carried out entirely on the basis of input from the parvocellular system (Merigan et al 1991).…”

Section: Discussionmentioning

confidence: 99%

Are masking abnormalities in schizophrenia specific to type-B masking?

Skottun¹,

Skoyles

2009

The World Journal of Biological Psychiatry

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The abnormal visual masking in those with schizophrenia, it has been proposed, arises from a deficiency in their magnocellular system. Two kinds of masking exist: Type-A and Type-B. Type-A masking is characterized by the masking being strongest when target and mask are presented simultaneously. Type-B masking is characterized by a non-monotonic masking curve, i.e. the masking is largest when the mask is presented at some time after the target. The proposed link between masking and magnocellular activity applies mainly to Type-B masking. Thus, a magnocellular deficiency, if it exists, should effect Type-B masking more prominently than Type-A masking. Here we review the relevant literature. The majority of studies of masking in those with schizophrenia, it is found, have examined only Type-A masking. These find substantial evidence for abnormal masking. Where Type-B masking has been obtained, evidence also exists for abnormalities. However, the abnormal masking in these cases is largely unrelated to the defining characteristic of Type-B masking (i.e. to the non-monotonic masking function). It is concluded that the evidence for linking masking abnormalities in schizophrenia specifically to Type-B masking is weak. This undermines the proposal that masking abnormalities in schizophrenia have a magnocellular origin.

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Stereopsis and magnocellular sensitivity in schizophrenia

Cited by 10 publications

References 57 publications

On Identifying Magnocellular and Parvocellular Responses on the Basis of Contrast-Response Functions

On Identifying Magnocellular and Parvocellular Responses on the Basis of Contrast-Response Functions

Dichoptic Spatial Contrast Sensitivity Reflects Binocular Balance in Normal and Stereoanomalous Subjects

Are masking abnormalities in schizophrenia specific to type-B masking?

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