| Relationship between physiological measures of excitability and levels of glutamate and GABA in the human motor cortex. | |
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MedLine Citation:
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PMID: 22005678 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Magnetic Resonance Spectroscopy (MRS) allows measurement of neurotransmitter concentrations within a region of interest in the brain. Inter-individual variation in MRS-measured GABA levels have been related to variation in task performance in a number of regions. However, it is not clear how MRS-assessed measures of GABA relate to cortical excitability or GABAergic synaptic activity. We therefore performed two studies investigating the relationship between neurotransmitter levels as assessed by MRS and Transcranial Magnetic Stimulation (TMS) measures of cortical excitability and GABA synaptic activity in the primary motor cortex. We present uncorrected correlations, where the p value should therefore be considered with caution. We demonstrated a correlation between cortical excitability, as assessed by the slope of the TMS input/output curve and MRS-assessed glutamate levels (r=0.803, p=0.015) but no clear relationship between MRS-assessed GABA levels and TMS-assessed synaptic GABAA activity (2.5ms ISI SICI; Exp 1: r = 0.33, p = 0.31; Exp 2: r=-0.23, p=0.46). or GABAB activity (LICI; Exp 1: r = -0.47, p = 0.51; Exp 2: r = 0.23, p = 0.47). We demonstrated a significant correlation between MRS-assessed GABA levels and an inhibitory TMS protocol (1ms ISI SICI) with distinct physiological underpinnings from the 2.5ms ISI SICI (r=-0.79, p=0.018). Interpretation of this finding is challenging as the mechanisms of 1ms ISI SICI are not well understood, but we speculate that our results support the possibility that 1ms ISI SICI reflects a distinct GABAergic inhibitory process, possibly that of extrasynaptic GABA tone. |
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Authors:
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Charlotte J Stagg; Sven Bestmann; Alexandra O Constantinescu; Luis Moreno Moreno; Claire Allman; Ralf Mekle; Mark Woolrich; Jamie Near; Heidi Johansen-Berg; John C Rothwell |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-10-17 |
Journal Detail:
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Title: The Journal of physiology Volume: - ISSN: 1469-7793 ISO Abbreviation: - Publication Date: 2011 Oct |
Date Detail:
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Created Date: 2011-10-18 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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University of Oxford; |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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