GABA, noise and gain in human visual cortex

Hammett, Stephen T.; Cook, Emily K.; Hassan, Omar; Hughes, Ceri-Ann; Rooslien, Hanna; Tizkar, Rana; Larsson, Jonas

doi:10.1016/j.neulet.2020.135294

Cited by 11 publications

(11 citation statements)

References 22 publications

(35 reference statements)

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“…GABAergic inhibition in the visual cortex has been investigated in relation to visual discrimination of orientation (Edden et al 2009;Mikkelsen et al 2018a), motion (Schallmo et al 2018(Schallmo et al , 2019 and visual contrast (Hammett et al 2020). The potential link between GABAergic inhibition and visual discrimination was first pursued by Edden et al (2009), who measured resting GABA + in the early visual cortex of volunteers who performed an orientation discrimination task outside of the scanner.…”

Section: Visual Discriminationmentioning

confidence: 99%

Investigating the neurochemistry of the human visual system using magnetic resonance spectroscopy

Bridge

2021

Brain Struct Funct

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Biochemical processes underpin the structure and function of the visual cortex, yet our understanding of the fundamental neurochemistry of the visual brain is incomplete. Proton magnetic resonance spectroscopy (1H-MRS) is a non-invasive brain imaging tool that allows chemical quantification of living tissue by detecting minute differences in the resonant frequency of molecules. Application of MRS in the human brain in vivo has advanced our understanding of how the visual brain consumes energy to support neural function, how its neural substrates change as a result of disease or dysfunction, and how neural populations signal during perception and plasticity. The aim of this review is to provide an entry point to researchers interested in investigating the neurochemistry of the visual system using in vivo measurements. We provide a basic overview of MRS principles, and then discuss recent findings in four topics of vision science: (i) visual perception, plasticity in the (ii) healthy and (iii) dysfunctional visual system, and (iv) during visual stimulation. Taken together, evidence suggests that the neurochemistry of the visual system provides important novel insights into how we perceive the world.

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Section: Visual Discriminationmentioning

confidence: 99%

Investigating the neurochemistry of the human visual system using magnetic resonance spectroscopy

Bridge

2021

Brain Struct Funct

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“…They could also exhaust their transmitter pool and further contribute to the glutamate pathology. GABA has been shown to be involved in cognitive impairments (Ghosal et al, 2017;Cao et al, 2018) and might be of importance for information filtering in the brain (Hammett et al, 2020), which are symptoms of importance in mental/cognitive fatigue.…”

Section: Astroglial Dysfunction With Impaired Glutamate Uptake and Mental Fatigue-a Hypothesismentioning

confidence: 99%

Long-Lasting Pathological Mental Fatigue After Brain Injury–A Dysfunction in Glutamate Neurotransmission?

Rönnbäck

Johansson

2022

Front. Behav. Neurosci.

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Long-lasting mental or cognitive fatigue may be a disabling symptom after physically recovered skull trauma, stroke, infection, or inflammation in the central nervous system (CNS). It is difficult to go back to work and participate in familiar social activities, as typically the person is only able to remain mentally active for short periods, and if mentally exhausted, the recovery time will be disproportionally long. Mental fatigue after traumatic brain injury correlates with brain information processing speed. Information processing is energy consuming and requires widespread and specific neural signaling. Glutamate signaling is essential for information processing, including learning and memory. Low levels and the fine-tuning of extracellular glutamate are necessary to maintain a high precision in information processing. The astroglial cells are responsible for the fine-tuning of the glutamate transmission, but this capacity is attenuated by substances or conditions associated with neuro-inflammation in brain pathology. In this paper, we extend our previously presented hypothesis on the cellular mechanisms underlying mental fatigue suggesting a dysfunction in the astroglial support of the glutamate transmission. Changes in other neurotransmitters such as dopamine, serotonin, norepinephrine, GABA, and acetylcholine after brain injury are also taken into consideration.

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“…This top-down suppression may be mediated by a stronger effect of internal noise elevation than of external noise admission at the perceptual template level [48], whereas it may occur through a larger effect in the reduction of response gain than of contrast gain on the contrast-response function of V1 neurons [32], and this top-down influence in response gain may relate to alterations in excitatory glutamatergic neurotransmission [103][104][105]. Finally, recent studies suggest that increased GABAergic inhibition may underlie noise filtering in the visual signal perception [106,107]. Taken together, it is possible that the network mechanism of surround suppression in the internal additive noise plus external noise exclusion observed for low-SF neurons in this study may involve a reduction of both excitation and inhibition in the local neural circuit, which chiefly causes a lowered contrast gain for neuronal contrast-response functions, whereas the single mechanism of surround suppression in the internal additive noise observed for high-SF neurons may relate predominantly to a reduction of excitation in the local neural circuit, which mainly results in a decreased response gain.…”

Section: Mechanisms Of Surround Suppressionmentioning

confidence: 99%

Mechanisms of Surround Suppression Effect on the Contrast Sensitivity of V1 Neurons in Cats

et al. 2022

Neural Plasticity

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Surround suppression (SS) is a phenomenon that a neuron’s response to visual stimuli within the classical receptive field (cRF) is suppressed by a concurrent stimulation in the surrounding receptive field (sRF) beyond the cRF. Studies show that SS affects neuronal response contrast sensitivity in the primary visual cortex (V1). However, the underlying mechanisms remain unclear. Here, we examined SS effect on the contrast sensitivity of cats’ V1 neurons with different preferred SFs using external noise-masked visual stimuli and perceptual template model (PTM) analysis at the system level. The contrast sensitivity was evaluated by the inverted threshold contrast of neurons in response to circular gratings of different contrasts in the cRF with or without an annular grating in the sRF. Our results showed that SS significantly reduced the contrast sensitivity of cats’ V1 neurons. The SS-induced reduction of contrast sensitivity was not correlated with SS strength but was dependent on neuron’s preferred SF, with a larger reduction for neurons with low preferred SFs than those with high preferred SFs. PTM analysis of threshold versus external noise contrast (TvC) functions indicated that SS decreased contrast sensitivity by increasing both the internal additive noise and impact of external noise for neurons with low preferred SFs, but improving only internal additive noise for neurons with high preferred SFs. Furthermore, the SS effect on the contrast-response function of low- and high-SF neurons also exhibited different mechanisms in contrast gain and response gain. Collectively, these results suggest that the mechanisms of SS effect on neuronal contrast sensitivity may depend on neuronal populations with different SFs.

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GABA, noise and gain in human visual cortex

Abstract: Highlights Cortical GABA levels correlate with contrast detection thresholds. GABA appears to reduce contrast response gain and intrinsic noise. Changes in contrast discrimination can be characterised by the Wilson-Cowan model.

Cited by 11 publications

References 22 publications

Investigating the neurochemistry of the human visual system using magnetic resonance spectroscopy

Investigating the neurochemistry of the human visual system using magnetic resonance spectroscopy

Long-Lasting Pathological Mental Fatigue After Brain Injury–A Dysfunction in Glutamate Neurotransmission?

Mechanisms of Surround Suppression Effect on the Contrast Sensitivity of V1 Neurons in Cats

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