title: Glutamatergic correlates of gamma-band oscillatory activity during cognition: a concurrent ER-MRS and EEG study.
abstract: Frequency specific synchronisation of neuronal firing within the gamma-band (30-70 Hz) appears to be a fundamental correlate of both basic sensory and higher cognitive processing. In-vitro studies suggest that the neurochemical basis of gamma-band oscillatory activity is based on interactions between excitatory (i.e. glutamate) and inhibitory (i.e. GABA) neurotransmitter concentrations. However, the nature of the relationship between excitatory neurotransmitter concentration and changes in gamma band activity in humans remains undetermined. Here, we examine the links between dynamic glutamate concentration and the formation of functional gamma-band oscillatory networks. Using concurrently acquired event-related magnetic resonance spectroscopy and electroencephalography, during a repetition-priming paradigm, we demonstrate an interaction between stimulus type (object vs. abstract pictures) and repetition in evoked gamma-band oscillatory activity, and find that glutamate levels within the lateral occipital cortex, differ in response to these distinct stimulus categories. Importantly, we show that dynamic glutamate levels are related to the amplitude of stimulus evoked gamma-band (but not to beta, alpha or theta or ERP) activity. These results highlight the specific connection between excitatory neurotransmitter concentration and amplitude of oscillatory response, providing a novel insight into the relationship between the neurochemical and neurophysiological processes underlying cognition.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, UK; School of Psychology, Bangor University, Bangor, UK.
authors.forename: Níall
authors.initials: N
authors.lastname: Lally
authors.forename: Paul G
authors.initials: PG
authors.lastname: Mullins
authors.forename: Mark V
authors.initials: MV
authors.lastname: Roberts
authors.forename: Darren
authors.initials: D
authors.lastname: Price
authors.forename: Thomas
authors.initials: T
authors.lastname: Gruber
authors.forename: Corinna
authors.initials: C
authors.lastname: Haenschel
mesh_terms: D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D005260:Female; D018698:Glutamic Acid / Q000032:analysis*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010775:Photic Stimulation; D011522:Protons; D060865:Repetition Priming / Q000502:physiology; D014793:Visual Cortex / Q000737:chemistry*; D055815:Young Adult
chemical_list: D011522:Protons; D018698:Glutamic Acid
keywords: (1)H-MRS; AMPA; EEG; ER-MRS; Event-related magnetic resonance spectroscopy; Evoked gamma-band oscillatory activity; FID; Free induction decay; Functional MRS; Functional magnetic resonance spectroscopy; GABA; Glutamate; LOC; Lateral occipital cortex; N-methyl-d-aspartate; NMDA; Proton magnetic resonance spectroscopy; Repetition suppression; Repetition-enhancement; Repetition-priming; electroencephalography; fMRS; gamma-aminobutyric acid; α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid