Neurochemical responses to chromatic and achromatic stimuli in the human visual cortex

Bednařík, Petr; Tkáč, Ivan; Giove, Federico; Eberly, Lynn E.; Deelchand, Dinesh K.; Barreto, Felipe Rodrigues; Mangia, Silvia

doi:10.1177/0271678x17695291

Cited by 45 publications

(73 citation statements)

References 44 publications

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“…Lac was precisely quantified in this study with an average CRLB of 8% (based on spectra with 60 averages). This is at the lower end of the range of previously reported values from 7 T fMRS studies using short TE sequences, which generally yield spectra with higher SNR (average CRLBs from 6% to 18%). We attribute this low error to the improved fit arising from the clean baseline achieved around the Lac resonance at longer TE and the inclusion of individual MM components in the basis set.…”

Section: Discussionmentioning

confidence: 99%

“…Although the results of the initial studies were contradictory, consistent changes in Lac concentration upon visual stimulation have been reported at 7 T, benefitting from the increase in SNR and spectral resolution at ultra‐high field. The average rise in Lac level during visual stimulation was found to be in the range of 7% to 37%, maintained until the end of the stimulus in most studies. However, these 7 T studies were generally designed to follow the time courses of all neurometabolites detectable by 1 H MRS and were not specifically optimized for measurement of Lac.…”

Section: Introductionmentioning

confidence: 91%

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Measurement of brain lactate during visual stimulation using a long TE semi‐LASER sequence at 7 T

et al. 2020

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Estimation of metabolic changes during neuronal activation represents a challenge for in vivo MRS, especially for metabolites with low concentration and signal overlap, such as lactate. In this work, we aimed to evaluate the feasibility of detecting lactate during brain activation using a long TE (144 ms) semi‐LASER sequence at 7 T. 1normalH spectra were acquired on healthy volunteers ( N=6) during a paradigm with 15 min of visual stimulation. Outer‐volume signals were further attenuated by the use of saturation slabs, and macromolecular signals in the vicinity of the inverted lactate peak were individually fitted with simulated Lorentzian peaks. All spectra were free of artefacts and highly reproducible across subjects. Lactate was accurately quantified with an average Cramér‐Rao lower bound of 8%. Statistically significant ( P<0.05, one‐tailed t‐test) increases in lactate ( ∼10%) and glutamate ( ∼3%) levels during stimulation were detected in the visual cortex. Lactate and glutamate changes were consistent with previous measurements. We demonstrated that quantification of a clear and non‐contaminated lactate peak obtained with a long TE sequence has the potential of improving the accuracy of functional MRS studies targeting non‐oxidative reaction pathways.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Measurement of brain lactate during visual stimulation using a long TE semi‐LASER sequence at 7 T

et al. 2020

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“…The quality of results strongly depended on experimental conditions, in particular the anesthesia, the number of animals, the size of the voxel of interest (VOI), and the quality of shimming (Just and Sonnay, ; Sonnay et al ; Sonnay et al ). In the human brain, large VOIs imply averaging over different cell types that cannot be easily resolved (Bednařík et al ). In the rodent brain, optogenetic approaches may overcome this problem.…”

mentioning

confidence: 99%

Probing activation‐induced neurochemical changes using optogenetics combined with functional magnetic resonance spectroscopy: a feasibility study in the rat primary somatosensory cortex

Just

Faber

2019

Journal of Neurochemistry

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Knowledge about biochemical processes is a prerequisite for a better understanding of mechanisms underlying brain activity. 1H functional magnetic resonance spectroscopy (1H‐fMRS) at high magnetic fields allows for the non‐invasive measurement of metabolic changes during brain activation. Optogenetics, on the other hand, has revolutionized the field of neuroscience. It was previously coupled with functional magnetic resonance imaging (fMRI) techniques in rodents enabling population‐specific targeting of cells, investigating brain networks with unprecedented in vivo precision. The coupling of optogenetics and 1H‐fMRS is expected to enhance the specificity of metabolic readouts to validate neuro‐energetic theories underlying brain activity. To date, the feasibility of combining optogenetic stimulation with fMRS has not been explored. We used green laser stimulation delivered through an optical fiber implanted superficially above the primary somatosensory forelimb cortex (S1FL) of rats expressing the C1V1 opsin in excitatory neurons. A protocol for the acquisition of functional 1H MR spectra upon optogenetic stimulation without craniotomy‐induced artefacts was established. Quantification of metabolite concentrations in S1FL upon optogenetic and electrical forepaw stimulation demonstrated significantly increased glutamate levels (+8.8% and +9.9%, p < 0.05 respectively), which were compensated by decreased glutamine levels (−17% and −18%, p < 0.05 respectively). Our results demonstrate for the first time the feasibility of combining optogenetic control and functional MR spectroscopy (o‐fMRS) in the rat somatosensory cortex, opening new possibilities for monitoring the energetic demands of specific cell populations and for exploring the underpinnings of energy metabolism during brain activity. Open Science Badges This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

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“…Previous work using MRS to understand the role of different neurotransmitters in normal brain function has focused on neurometabolite activity in visual cortex; in particular, the function of g -aminobutyric acid (GABA) and glutamate (Glu), the primary inhibitory and excitatory neurotransmitters in the central nervous system, respectively. A consistent finding from these studies is that Glu increases in visual cortex in response to visual stimulation, which has been interpreted as increased involvement of this neurotransmitter during the processing of visual stimuli (Mangia et al, 2007;Lin et al, 2012;Schaller et al, 2013;Bednarõík et al, 2015Bednarõík et al, , 2018Ip et al, 2017;Kurcyus et al, 2018). The findings relating to GABA have been less consistent.…”

Section: Introductionmentioning

confidence: 90%

“…The findings relating to GABA have been less consistent. One study found less GABA in visual cortex during visual stimulation compared with baseline ( Mekle et al, 2017 ), while other studies have not replicated this result ( Mangia et al, 2007 ; Schaller et al, 2013 ; Bednařík et al, 2015 , 2018 ; Kurcyus et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Temporal Dynamics of GABA and Glx in the Visual Cortex

Rideaux

2020

eNeuro

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Magnetic resonance spectroscopy (MRS) can be used in vivo to quantify neurometabolite concentration and provide evidence for the involvement of different neurotransmitter systems (e.g., inhibitory and excitatory) in sensory and cognitive processes. The relatively low signal-to-noise ratio of MRS measurements has shaped the types of questions that it has been used to address. In particular, temporal resolution is often sacrificed in MRS studies to achieve a signal sufficient to produce a reliable estimate of neurometabolite concentration. Here we apply novel analyses with large datasets from human participants (both sexes) to reveal the dynamics of GABA 1 and Glx in visual cortex while participants are at rest (with eyes closed) and compare this with changes in posterior cingulate cortex from a previously collected dataset (under different conditions). We find that the dynamic concentration of GABA 1 and Glx in visual cortex drifts in opposite directions; that is, GABA 1 decreases while Glx increases over time. Further, we find that in visual, but not posterior cingulate cortex, the concentration of GABA 1 predicts that of Glx 120 s later, such that a change in GABA 1 is correlated with a subsequent opposite change in Glx. Together, these results expose novel temporal trends and interdependencies of primary neurotransmitters in visual cortex. More broadly, we demonstrate the feasibility of using MRS to investigate in vivo dynamic changes of neurometabolites.

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Neurochemical responses to chromatic and achromatic stimuli in the human visual cortex

Cited by 45 publications

References 44 publications

Measurement of brain lactate during visual stimulation using a long TE semi‐LASER sequence at 7 T

Measurement of brain lactate during visual stimulation using a long TE semi‐LASER sequence at 7 T

Probing activation‐induced neurochemical changes using optogenetics combined with functional magnetic resonance spectroscopy: a feasibility study in the rat primary somatosensory cortex

Temporal Dynamics of GABA and Glx in the Visual Cortex

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