Individual differences in GABA content are reliable but are not uniform across the human cortex

Greenhouse, Ian; Noah, Sean; Maddock, Richard J.; Ivry, Richard B.

doi:10.1016/j.neuroimage.2016.06.007

Cited by 69 publications

(60 citation statements)

References 51 publications

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“…decrease in NCE that they had hypothesised. The group postulated that GABA activity may not have increased globally by auricular tVNS but was rather differentially modified in different brain regions, as has been previously reported (Greenhouse et al 2016).…”

Section: Effects Of Auricular Tvns On the Central Nervous System (Cns)mentioning

confidence: 75%

The anatomical basis for transcutaneous auricular vagus nerve stimulation

et al. 2019

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The array of end organ innervations of the vagus nerve, coupled with increased basic science evidence, has led to vagus nerve stimulation (VNS) being explored as a management option in a number of clinical disorders, such as heart failure, migraine and inflammatory bowel disease. Both invasive (surgically implanted) and non‐invasive (transcutaneous) techniques of VNS exist. Transcutaneous VNS (tVNS) delivery systems rely on the cutaneous distribution of vagal afferents, either at the external ear (auricular branch of the vagus nerve) or at the neck (cervical branch of the vagus nerve), thus obviating the need for surgical implantation of a VNS delivery device and facilitating further investigations across a wide range of uses. The concept of electrically stimulating the auricular branch of the vagus nerve (ABVN), which provides somatosensory innervation to several aspects of the external ear, is relatively more recent compared with cervical VNS; thus, there is a relative paucity of literature surrounding its operation and functionality. Despite the increasing body of research exploring the therapeutic uses of auricular transcutaneous VNS (tVNS), a comprehensive review of the cutaneous, intracranial and central distribution of ABVN fibres has not been conducted to date. A review of the literature exploring the neuroanatomical basis of this neuromodulatory therapy is therefore timely. Our review article explores the neuroanatomy of the ABVN with reference to (1) clinical surveys examining Arnold’s reflex, (2) cadaveric studies, (3) fMRI studies, (4) electrophysiological studies, (5) acupuncture studies, (6) retrograde tracing studies and (7) studies measuring changes in autonomic (cardiovascular) parameters in response to auricular tVNS. We also provide an overview of the fibre composition of the ABVN and the effects of auricular tVNS on the central nervous system. Cadaveric studies, of which a limited number exist in the literature, would be the ‘gold‐standard’ approach to studying the cutaneous map of the ABVN; thus, there is a need for more such studies to be conducted. Functional magnetic resonance imaging (fMRI) represents a useful surrogate modality for discerning the auricular sites most likely innervated by the ABVN and the most promising locations for auricular tVNS. However, given the heterogeneity in the results of such investigations and the various limitations of using fMRI, the current literature lacks a clear consensus on the auricular sites that are most densely innervated by the ABVN and whether the brain regions secondarily activated by electrical auricular tVNS depend on specific parameters. At present, it is reasonable to surmise that the concha and inner tragus are suitable locations for vagal modulation. Given the therapeutic potential of auricular tVNS, there remains a need for the cutaneous map of the ABVN to be further refined and the effects of various stimulation parameters and stimulation sites to be determined.

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Section: Effects Of Auricular Tvns On the Central Nervous System (Cns)mentioning

confidence: 75%

The anatomical basis for transcutaneous auricular vagus nerve stimulation

et al. 2019

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“…For example, the Hi-BM group might have relatively more excitatory activity in V2 for example, than the Lo-BM group, leading to greater levels of facilitatory feedback to V1. Of relevance here is recent work by Greenhouse et al (2016) suggesting that there are reliable individual differences in GABA concentration between cortical areas. Furthermore, there is evidence that individual differences in GABA in early visual areas can predict performance in a psychophysical task (Edden et al 2009).…”

Section: Discussionmentioning

confidence: 86%

Individual differences in the dynamics of collinear facilitation?

2017

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Collinear facilitation refers to the increase in sensitivity found for a target when aligned between nearby, brighter flankers. Many studies have explored the spatial and temporal aspects of this arrangement, and there is a consensus that two mechanisms could be responsible for this phenomenon; lateral excitation within V1 and extra-striate feedback to V1. There is some debate as to whether facilitation can still occur if the target is presented before the flankers, a manipulation known as backward masking, which could rely on feedback to V1. We shed light on this debate by using forward, simultaneous and backward masking with a relatively large sample of 26 participants.We used short stimulus presentation times (35 ms) and a range of SOAs (stimulus onset asynchronies) (-70, -35, 0, 35 and 70 ms) in order to isolate any feedback facilitation that may occur.We found that collinear facilitation occurred with forward masking (+ve SOAs) in all participants.However, facilitation with backward masking (-ve SOAs) only occurred in 54% of participants. We present a basic model of facilitation that simulates the results of our experiment and could account for differences between previous studies. The model indicates that facilitation with backward masking arises primarily from feedback excitation. Our findings suggest that both lateral connectivity and extra-striate feedback contribute to target facilitation, but in fundamentally different ways and that feedback may be significantly reduced in some participants.2

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“…We hypothesised a positive relationship between PCu/PCC scene‐related activity and tNAA levels (consistent with Hao et al, ), a positive relationship between PCu/PCC scene‐related activity and Glx, and a negative relationship with GABA+ (consistent with Hu et al, ). Finally, we predicted there would be no relationship between PCu/PCC BOLD for complex scene discrimination and OCC metabolites; a finding that would be supportive of regional specificity of any PCu/PCC BOLD‐MRS relationships (Duncan, Wiebking, Munoz‐Torres, & Northoff, ; Greenhouse, Noah, Maddock, & Ivry, ; Hu et al, ).…”

Section: Introductionmentioning

confidence: 81%

“…Finally, we predicted there would be no relationship between PCu/PCC BOLD for complex scene discrimination and OCC metabolites; a finding that would be supportive of regional specificity of any PCu/PCC BOLD-MRS relationships (Duncan, Wiebking, Munoz-Torres, & Northoff, 2014;Greenhouse, Noah, Maddock, & Ivry, 2016;Hu et al, 2013).…”

mentioning

confidence: 82%

Neurochemical correlates of scene processing in the precuneus/posterior cingulate cortex: A multimodal fMRI and ¹H‐MRS study

Costigan

Umla-Runge

Evans

et al. 2019

Human Brain Mapping

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Precuneus/posterior cingulate cortex (PCu/PCC) are key components of a midline network, activated during rest but also in tasks that involve construction of scene or situation models. Despite growing interest in PCu/PCC functional alterations in disease and disease risk, the underlying neurochemical modulators of PCu/PCC's task‐evoked activity are largely unstudied. Here, a multimodal imaging approach was applied to investigate whether interindividual differences in PCu/PCC fMRI activity, elicited during perceptual discrimination of scene stimuli, were correlated with local brain metabolite levels, measured during resting‐state 1 H‐MRS. Forty healthy young adult participants completed an fMRI perceptual odd‐one‐out task for scenes, objects and faces. 1 H‐MRS metabolites N ‐acetyl‐aspartate (tNAA), glutamate (Glx) and γ‐amino‐butyric acid (GABA+) were quantified via PRESS and MEGA‐PRESS scans in a PCu/PCC voxel and an occipital (OCC) control voxel. Whole brain fMRI revealed a cluster in right dorsal PCu/PCC that showed a greater BOLD response to scenes versus faces and objects. When extracted from an independently defined PCu/PCC region of interest, scene activity (vs. faces and objects and also vs. baseline) was positively correlated with PCu/PCC, but not OCC, tNAA. A voxel‐wise regression analysis restricted to the PCu/PCC 1 H‐MRS voxel area identified a significant PCu/PCC cluster, confirming the positive correlation between scene‐related BOLD activity and PCu/PCC tNAA. There were no correlations between PCu/PCC activity and Glx or GABA+ levels. These results demonstrate, for the first time, that scene activity in PCu/PCC is linked to local tNAA levels, identifying a neurochemical influence on interindividual differences in the task‐driven activity of a key brain hub.

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Individual differences in GABA content are reliable but are not uniform across the human cortex

Cited by 69 publications

References 51 publications

The anatomical basis for transcutaneous auricular vagus nerve stimulation

The anatomical basis for transcutaneous auricular vagus nerve stimulation

Individual differences in the dynamics of collinear facilitation?

Neurochemical correlates of scene processing in the precuneus/posterior cingulate cortex: A multimodal fMRI and ¹H‐MRS study

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Individual differences in GABA content are reliable but are not uniform across the human cortex

Cited by 69 publications

References 51 publications

The anatomical basis for transcutaneous auricular vagus nerve stimulation

The anatomical basis for transcutaneous auricular vagus nerve stimulation

Individual differences in the dynamics of collinear facilitation?

Neurochemical correlates of scene processing in the precuneus/posterior cingulate cortex: A multimodal fMRI and 1H‐MRS study

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Product

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Neurochemical correlates of scene processing in the precuneus/posterior cingulate cortex: A multimodal fMRI and ¹H‐MRS study