scholarly journals Relating excitatory and inhibitory neurochemicals to visual perception: a magnetic resonance study of occipital cortex between migraine events

2018 ◽  
Author(s):  
Yu Man Chan ◽  
Kabilan Pitchaimuthu ◽  
Qi-Zhu Wu ◽  
Olivia L Carter ◽  
Gary F Egan ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Magnetic Resonance ◽  
Visual Perception ◽  
Binocular Rivalry ◽  
Occipital Cortex ◽  
Individual Variability ◽  
Healthy Individuals ◽  
Magnetic Resonance Study ◽  
Gaba Concentration ◽  
Inhibitory Neurotransmitter

AbstractCertain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

scholarly journals Relating excitatory and inhibitory neurochemicals to visual perception: A magnetic resonance study of occipital cortex between migraine events

PLoS ONE ◽  
2019 ◽  
Vol 14 (7) ◽  
pp. e0208666 ◽  
Author(s):  
Yu Man Chan ◽  
Kabilan Pitchaimuthu ◽  
Qi-Zhu Wu ◽  
Olivia L. Carter ◽  
Gary F. Egan ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Visual Perception ◽  
Occipital Cortex ◽  
Magnetic Resonance Study

scholarly journals Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

2020 ◽  
Author(s):  
Dania Abuleil ◽  
Daphne McCulloch ◽  
Benjamin Thompson
Keyword(s):  
Visual Cortex ◽  
Binocular Rivalry ◽  
Gamma Aminobutyric Acid ◽  
Gaba Concentration ◽  
Excitatory Neurotransmitter ◽  
Inhibitory Neurotransmitter ◽  
Before And After ◽  
Visual Cortices ◽  
Cortical Excitation ◽  
Theta Burst

AbstractNeuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N=15) or cTBS (N=15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS significantly increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.

scholarly journals Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0239349
Author(s):  
Dania Abuleil ◽  
Daphne McCulloch ◽  
Benjamin Thompson
Keyword(s):  
Visual Cortex ◽  
Binocular Rivalry ◽  
Gamma Aminobutyric Acid ◽  
Gaba Concentration ◽  
Excitatory Neurotransmitter ◽  
Inhibitory Neurotransmitter ◽  
Before And After ◽  
Visual Cortices ◽  
Cortical Excitation ◽  
Theta Burst

Neuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine (ACH) increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N = 15) or cTBS (N = 15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.

scholarly journals ABIAKĖ KONKURENCIJA IR NEURONINIŲ PROCESŲ DINAMIKA

Psichologija ◽  
2008 ◽  
Vol 38 ◽  
pp. 7-18
Author(s):  
Randolph Blake ◽  
Sang-Hun Lee ◽  
David Heeger
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Visual Perception ◽  
Functional Magnetic Resonance Imaging ◽  
Binocular Rivalry ◽  
Occipital Cortex ◽  
Subjective Perception ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Spatio Temporal

Tirdami regimąjį suvokimą geštaltpsichologai buvo sužavėti vykstančių procesų kaitos (dinamikos). Jie suformulavo hipotezę, kad procesų kaita atspindi nuolatinį elektrinių signalų sklidimą anatomiškai struktūruotoje elektrai laidžioje smegenų terpėje (lauke). Šia teorija, vadinama dinaminio lauko teorija, vėliau buvo suabejota, nes buvo pastebėta, kad smegenys elektriniu požiūriu nėra homogeniška terpė. Jos susideda iš atskirų diskrečių elementų, atliekančių sudėtingus skaičiavimus, sujungtų tarpusavyje daugybe ryšių ir sudarančių neuronų tinklą. Tačiau šis naujas šiuolaikinis požiūris į smegenų funkcijas susiduria su sunkumais, mėginant paaiškinti suvokimo procesų kitimą erdvėje ir laike. Tirdami suvokimo ir smegenų žievės dinaminius procesus, pagrindinį dėmesį skyrėme dominuojančių procesų (konkurencijos metu) kaitai erdvėje ir laike. Sukūrėme psichofizinių metodų, kuriais būtų galima sukelti ir išmatuoti minėtų procesų kaitą ir taikėme funkcinio magnetinio rezonanso vizualizavimo (fMRI) metodą su šiais procesais susijusiam neuronų aktyvumui išmatuoti. Gauti rezultatai atskleidė pirminės ir antrinės regimosios žievės pakaušio srityje aktyvumo bangų retinotopinį sklidimą, kuris koreliuoja su suvokiamo dominuojančio vaizdo bangos sklidimu abiakės konkurencijos metu. Šiame straipsnyje apžvelgiami minėtų eksperimentų rezultatai. Pagrindiniai žodžiai: abiakė rega, vaizdų konkurencija, regimoji žievė, funkcinis magnetinis rezonansas, neuroninių procesų kaita (dinamika).Binocular Rivalry and Neutral DynamicsRandolph Blake, Sang-Hun Lee, David Heeger SummaryThe Gestalt psychologists were fascinated with dynamics evident in visual perception, and they theorized that these dynamics were attributable to ever-changing electrical potentials within topographically organized brain fields. Dynamic field theory, as it was called, was subsequently discredited on grounds that the brain does not comprise a unitary electrical field but, instead, a richly interconnected network of discrete computing elements. Still, this modern conceptualization of brain function faces thechallenge of explaining the fact that perception is dynamic in space and in time. To pursue the question of visual perception and cortical dynamics, we have focused on spatio-temporal transitions in dominance during binocular rivalry. We have developed techniques for initiating and measuring these transitions psychophysically and for measuring their neural concomitants using functional magnetic resonance imaging (fMRI). Our findings disclose the existence of waves of cortical activity that travel across the retinotopic maps that define primary and secondary visual areas within occipital cortex, in correspondence with the subjective perception of spreading waves of dominance during binocular rivalry. This paper reviews the results from those studies.Key words: binocular vision, binocular rivalry, visual cortex, fMRI (functional magnetic resonance imaging), dynamic of neuronal process.

scholarly journals GABA levels in ventral visual cortex decline with age and are associated with neural distinctiveness

2019 ◽  
Author(s):  
Jordan D. Chamberlain ◽  
Holly Gagnon ◽  
Poortata Lalwani ◽  
Kaitlin E. Cassady ◽  
Molly Simmonite ◽  
...  
Keyword(s):  
Older Adults ◽  
Visual Cortex ◽  
Magnetic Resonance ◽  
Aminobutyric Acid ◽  
Resonance Spectroscopy ◽  
Gamma Aminobutyric Acid ◽  
Younger Adults ◽  
Inhibitory Neurotransmitter ◽  
Neural Representations ◽  
Age Related

AbstractAge-related neural dedifferentiation – reduced distinctiveness of neural representations in the aging brain– has been associated with age-related declines in cognitive abilities. But why does neural distinctiveness decline with age? Based on prior work in non-human primates, we hypothesized that the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) declines with age and is associated with neural dedifferentiation. To test this hypothesis, we used magnetic resonance spectroscopy (MRS) to measure GABA and functional MRI (fMRI) to measure neural distinctiveness in the ventral visual cortex in a set of older and younger participants. Relative to younger adults, older adults exhibited lower GABA levels and less distinct activation patterns for faces and houses in the ventral visual cortex. Furthermore, individual differences in GABA within older adults predicted individual differences in neural distinctiveness even after controlling for gray matter volume and age. These results provide novel support for the view that age-related reductions of GABA contribute to age-related reductions in neural distinctiveness (i.e., neural dedifferentiation) in the human ventral visual cortex.Significance StatementNeural representations in the ventral visual cortex are less distinguishable in older compared to younger humans, and this neural dedifferentiation is associated with age-related cognitive deficits. Animal models suggest that reductions in the inhibitory neurotransmitter gamma aminobutyric acid (GABA) may play a role. To investigate this hypothesis, we combined functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS) in a study of the human ventral visual cortex. We observed reduced distinctiveness of neural patterns and reduced GABA levels in older compared to younger adults. Furthermore, older adults with higher GABA levels tended to have more distinctive neural representations. These findings suggest that reduced GABA levels contribute to age-related declines in neural distinctiveness in the human ventral visual cortex.

scholarly journals Reduction of higher-order occipital GABA and impaired visual perception in acute major depressive disorder

2021 ◽  
Author(s):  
Xue Mei Song ◽  
Xi-Wen Hu ◽  
Zhe Li ◽  
Yuan Gao ◽  
Xuan Ju ◽  
...  
Keyword(s):  
Major Depressive Disorder ◽  
Visual Perception ◽  
Depressive Disorder ◽  
Symptom Severity ◽  
Occipital Cortex ◽  
Higher Order ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Major Depressive ◽  
Psychopathological Symptoms

AbstractMajor depressive disorder (MDD) is a complex state-dependent psychiatric illness for which biomarkers linking psychophysical, biochemical, and psychopathological changes remain yet elusive, though. Earlier studies demonstrate reduced GABA in lower-order occipital cortex in acute MDD leaving open its validity and significance for higher-order visual perception, though. The goal of our study is to fill that gap by combining psychophysical investigation of visual perception with measurement of GABA concentration in middle temporal visual area (hMT+) in acute depressed MDD. Psychophysically, we observe a highly specific deficit in visual surround motion suppression in a large sample of acute MDD subjects which, importantly, correlates with symptom severity. Both visual deficit and its relation to symptom severity are replicated in the smaller MDD sample that received MRS. Using high-field 7T proton Magnetic resonance spectroscopy (1H-MRS), acute MDD subjects exhibit decreased GABA concentration in visual MT+ which, unlike in healthy subjects, no longer correlates with their visual motion performance, i.e., impaired SI. In sum, our combined psychophysical-biochemical study demonstrates an important role of reduced occipital GABA for altered visual perception and psychopathological symptoms in acute MDD. Bridging the gap from the biochemical level of occipital GABA over visual-perceptual changes to psychopathological symptoms, our findings point to the importance of the occipital cortex in acute depressed MDD including its role as candidate biomarker.

scholarly journals Primary visual cortex is necessary for blindsight-like behavior in neurologically healthy individuals: Review of transcranial magnetic stimulation studies

2021 ◽  
Author(s):  
Henry Railo ◽  
Mikko Hurme
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Primary Visual Cortex ◽  
Visual Stimulus ◽  
Magnetic Stimulation ◽  
Neural Mechanisms ◽  
Partial Recovery ◽  
Visually Guided ◽  
Healthy Individuals

The visual pathways that bypass the primary visual cortex (V1) are often assumed to support visually guided behavior in humans in the absence of conscious vision. This conclusion is largely based on findings on patients: V1 lesions cause blindness but sometimes leave some visually guided behaviors intact—this is known as blindsight. With the aim of examining how well the findings on blindsight patients generalize to neurologically healthy individuals, we review studies which have tried to uncover transcranial magnetic stimulation (TMS) induced blindsight. In general, these studies have failed to demonstrate a completely unconscious blindsight-like capacity in neurologically healthy individuals. A possible exception to this is TMS-induced blindsight of stimulus presence or location. Because blindsight in patients is often associated with some form of introspective access to the visual stimulus, and may be associated with neural reorganization, we suggest that rather than revealing a dissociation between neural mechanisms of behavior and conscious seeing, blindsight may reflect preservation or partial recovery of conscious visual perception after the lesion.

scholarly journals Mixed-polarity random-dot stereograms alter GABA and Glx concentration in the early visual cortex

2019 ◽  
Vol 122 (2) ◽  
pp. 888-896 ◽  
Author(s):  
Reuben Rideaux ◽  
Nuno R. Goncalves ◽  
Andrew E. Welchman
Keyword(s):  
Visual Cortex ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Curr Biol ◽  
Random Dot Stereograms ◽  
Mixed Polarity ◽  
Early Visual Cortex

The offset between images projected onto the left and right retina (binocular disparity) provides a powerful cue to the three-dimensional structure of the environment. It was previously shown that depth judgements are better when images comprise both light and dark features, rather than only light or only dark elements. Since Harris and Parker ( Nature 374: 808–811, 1995) discovered the “mixed-polarity benefit,” there has been limited evidence supporting their hypothesis that the benefit is due to separate bright and dark channels. Goncalves and Welchman ( Curr Biol 27: 1403–1412, 2017) observed that single- and mixed-polarity stereograms evoke different levels of positive and negative activity in a deep neural network trained on natural images to make depth judgements, which also showed the mixed-polarity benefit. Motivated by this discovery, we seek to test the potential for changes in the balance of excitation and inhibition that are produced by viewing these stimuli. In particular, we use magnetic resonance spectroscopy to measure Glx and GABA concentrations in the early visual cortex of adult humans during viewing of single- and mixed-polarity random-dot stereograms (RDS). We find that participants’ Glx concentration is significantly higher, whereas GABA concentration is significantly lower, when mixed-polarity RDS are viewed than when single-polarity RDS are viewed. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents, consistent with recent theoretical work (Goncalves NR, Welchman AE. Curr Biol 27: 1403–1412, 2017). NEW & NOTEWORTHY Depth judgements are better when images comprise both light and dark features, rather than only light or only dark elements. Using magnetic resonance spectroscopy, we show that adult human participants’ Glx concentration is significantly higher whereas GABA concentration is significantly lower in the early visual cortex when participants view mixed-polarity random-dot stereograms (RDS) compared with single-polarity RDS. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents.

scholarly journals A common neuronal code for perceptual processes in visual cortex? Comparing choice and attentional correlates in V5/MT

2004 ◽  
Vol 359 (1446) ◽  
pp. 929-941 ◽  
Author(s):  
Kristine Krug
Keyword(s):  
Cerebral Cortex ◽  
Visual Cortex ◽  
Visual Perception ◽  
Neuronal Activity ◽  
Binocular Rivalry ◽  
Single Cells ◽  
Neuronal Mechanism ◽  
The Past ◽  
External Stimuli ◽  
Neuronal Code

In the past two decades, sensory neuroscience has moved from describing response properties to external stimuli in cerebral cortex to establishing connections between neuronal activity and sensory perception. The seminal studies by Newsome, Movshon and colleagues in the awake behaving macaque firmly link single cells in extrastriate area V5/MT and perception of motion. A decade later, extrastriate visual cortex appears awash with neuronal correlates for many different perceptual tasks. Examples are attentional signals, choice signals for ambiguous images, correlates for binocular rivalry, stereo and shape perception, and so on. These diverse paradigms are aimed at elucidating the neuronal code for perceptual processes, but it has been little studied how they directly compare or even interact. In this paper, I explore to what degree the measured neuronal signals in V5/MT for choice and attentional paradigms might reflect a common neuronal mechanism for visual perception.

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