Issues Revisited: Shifts in Binocular Balance Depend on the Deprivation Duration in Normal and Amblyopic Adults

Min, Seung Hyun; Chen, Yiya; Jiang, Nan; He, Zhifen; Zhou, Jiawei; Hess, Robert F.

doi:10.1007/s40123-022-00560-5

Cited by 6 publications

(4 citation statements)

References 64 publications

(95 reference statements)

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“…Second, the psychophysical task that is used in the study might not have been sensitive enough to capture the boost in plasticity in amblyopia. In fact, previous studies show that the boost of plasticity from an increased patching duration was only present in one visual task but not another that measures binocular combination (Min et al, 2018(Min et al, , 2022. Lastly, it is well established that plasticity is markedly reduced in adults.…”

Section: Discussionmentioning

confidence: 97%

“…There are several possibilities for why this was. First, the shift in eye balance after monocular deprivation has been shown to be smaller in amblyopes than that in normal observers (Min et al., 2022). To illustrate, 5 h patching induces a larger shift in eye balance in binocular combination than 2 h patching in normal but not in amblyopic observers.…”

Section: Discussionmentioning

confidence: 99%

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Metaplasticity: Dark exposure boosts local excitability and visual plasticity in adult human cortex

Min,

Wang,

Chen

et al. 2023

The Journal of Physiology

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An interlude of dark exposure for about 1 week is known to shift excitatory/inhibitory (E/I) balance of the mammalian visual cortex, promoting plasticity and accelerating visual recovery in animals that have experienced cortical lesions during development. However, the translational impact of our understanding of dark exposure from animal studies to humans remains elusive. Here, we used magnetic resonance spectroscopy as a probe for E/I balance in the primary visual cortex (V1) to determine the effect of 60 min of dark exposure, and measured binocular combination as a behavioural assay to assess visual plasticity in 14 normally sighted human adults. To induce neuroplastic changes in the observers, we introduced 60 min of monocular deprivation, which is known to temporarily shift sensory eye balance in favour of the previously deprived eye. We report that prior dark exposure for 60 min strengthens local excitability in V1 and boosts visual plasticity in normal adults. However, we show that it does not promote plasticity in amblyopic adults. Nevertheless, our findings are surprising, given the fact that the interlude is very brief. Interestingly, we find that the increased concentration of the excitatory neurotransmitter is not strongly correlated with the enhanced functional plasticity. Instead, the absolute degree of change in its concentration is related to the boost, suggesting that the dichotomy of cortical excitation and inhibition might not explain the physiological basis of plasticity in humans. We present the first evidence that an environmental manipulation that shifts cortical E/I balance can also act as a metaplastic facilitator for visual plasticity in humans. imageKey points A brief interlude (60 min) of dark exposure increased the local concentration of glutamine/glutamate but not that of GABA in the visual cortex of adult humans. After dark exposure, the degree of the shift in sensory eye dominance in favour of the previously deprived eye from short‐term monocular deprivation was larger than that from only monocular deprivation. The neurochemical and behavioural measures were associated: the magnitude of the shift in the concentration of glutamine/glutamate was correlated with the boost in perceptual plasticity after dark exposure. Surprisingly, the increase in the concentration of glutamine/glutamate was not correlated with the perceptual boost after dark exposure, suggesting that the physiological mechanism of how E/I balance regulates plasticity is not deterministic. In other words, an increased excitation did not unilaterally promote plasticity.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Metaplasticity: Dark exposure boosts local excitability and visual plasticity in adult human cortex

Min,

Wang,

Chen

et al. 2023

The Journal of Physiology

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“…At the time, these results suggest that there might be long-term changes in the suppressive interactions induced by short-term monocular deprivation in amblyopes, which might result from the larger plasticity in the amblyopic visual system. 59 More recently, the results from Min et al 60 and Zhou et al 44 show the sensory eye dominance returned to baseline in participants with normal vision, while the shifts in sensory eye dominance lasted more than 1 hour after the removal of the patch in amblyopic adults. Indeed, recent studies have observed improvements in both binocular (e.g., ocular dominance and stereopsis) and monocular (e.g., visual acuity) functions in older children and adults after successive daily inverse patching 2 hours/day for 2 months.…”

Section: Discussionmentioning

confidence: 98%

The Suppressive Basis of Ocular Dominance Changes Induced by Short-Term Monocular Deprivation in Normal and Amblyopic Adults

Gong,

Reynaud,

Hess

et al. 2023

Invest. Ophthalmol. Vis. Sci.

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Purpose We aimed to study the effect of short-term monocular deprivation on the suppressive interocular interactions in normals and amblyopes by using a dichoptic masking paradigm. Methods Nine adults with anisometropic or mixed amblyopia and 10 control adults participated in our study. The contrast sensitivity in discriminating a target Gabor dichoptically masked was measured before and after 2 hours of monocular deprivation. The mask consisted of bandpass-filtered noise. Both the target and the mask were horizontally oriented at the spatial frequency of 1.31 cpd. Deprivation was achieved using an opaque patch on the amblyopic eye of amblyopes and the dominant eye of controls. Results Results were similar in both controls and amblyopes. After 2 hours of monocular deprivation, the previously patched eye showed a significant increase in contrast sensitivity under dichoptic masking, which also suggested reduced suppressive effect from the nonpatched eye. Meanwhile, the contrast sensitivity of the nonpatched eye remained almost unchanged under dichoptic masking. Conclusions We demonstrate that the ocular dominance changes induced by short-term monocular deprivation—namely, the strengthening of the deprived eye's contribution—are associated with the unilateral and asymmetric changes in suppressive interaction. The suppression from the nondeprived eye is reduced after short-term monocular deprivation. This provides a better understanding of how inverse patching (patching of the amblyopic eye) could, by reducing the suppressive drive from the normally sighted (nondeprived) eye, form the basis of a new treatment for the binocular deficit in amblyopia.

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“…The changes after contrast deprivation is orientationally tuned ( Zhang et al, 2009 ), while monocular deprivation is not ( Zhou et al, 2014 ; Wang et al, 2017 ). Furthermore, the effect of the duration of adaptation seems to be uniquely different between contrast adaptation and monocular deprivation ( Min et al, 2022 ).…”

Section: Introductionmentioning

confidence: 99%

Short-term monocular pattern deprivation reduces the internal additive noise of the visual system

Li,

Cheng,

et al. 2023

Front. Neurosci.

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Previous studies have shown that short-term monocular pattern deprivation can shift perceptual dominance in favor of the deprived eye. However, little is known about the effect of monocular pattern deprivation on contrast sensitivity (CS) and its corresponding mechanisms. Here, contrast sensitivity function (CSF) in the nondominant eye of normal subjects was evaluated before and after 150 min of monocular pattern deprivation. To obtain a CSF with high precision and efficiency before deprivation effect washout, a quick CSF (qCSF) method was used to assess CS over a wide range of spatial frequencies and at two external noise levels. We found that (1) monocular pattern deprivation effectively improved the CS of the deprived eye with larger effect on high spatial frequencies, (2) CS improvement only occurred when external noise was absent and its amount was spatial frequency dependent, and (3) a perceptual template model (PTM) revealed that decreased internal additive noise accounted for the mechanism of the monocular pattern derivation effect. These findings help us better understand the features of short-term monocular pattern deprivation and shed light on the treatment of amblyopia.

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Issues Revisited: Shifts in Binocular Balance Depend on the Deprivation Duration in Normal and Amblyopic Adults

Cited by 6 publications

References 64 publications

Metaplasticity: Dark exposure boosts local excitability and visual plasticity in adult human cortex

Metaplasticity: Dark exposure boosts local excitability and visual plasticity in adult human cortex

The Suppressive Basis of Ocular Dominance Changes Induced by Short-Term Monocular Deprivation in Normal and Amblyopic Adults

Short-term monocular pattern deprivation reduces the internal additive noise of the visual system

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