Hippocampal glutamate concentration predicts cerebral theta oscillations during cognitive processing.
BACKGROUND
Brain waves reflect collective behavior of neurons and provide insight into distributed network processing. Frontal and hippocampal theta oscillations (4-7 Hz) were linked to cognitive tasks and animal studies have suggested an involvement of glutamatergic neurotransmission in integrative frontal-hippocampal processing. Human evidence for such relationships is lacking.


METHODS
Here, we studied the associations between glutamate concentrations in the hippocampal region, measured by a 3-T proton magnetic resonance spectroscopy (1H-MRS), and EEG theta activity during an auditory target detection paradigm.


RESULTS
A robust relationship between hippocampal glutamate and frontal theta activity during stimulus processing was found. Moreover, frontal theta oscillations were related to response speed.


CONCLUSIONS
The results suggest a functional coupling between the frontal cortex and hippocampal region during stimulus processing and support the idea of the hippocampus as a neural rhythm generator driven by glutamatergic neurotransmission. These preliminary data show, for the first time, a relationship between in vivo measured glutamate and basic cerebral information processing in humans.
Gallinat
J
J
Clinic for Psychiatry and Psychotherapy (PUK im SHK), Charité-University Medicine Berlin, Campus Mitte, St. Hedwig Krankenhaus, Turmstrasse 21, 10559 Berlin, Germany. juergen.gallinat@charite.de
Kunz
D
D
Senkowski
D
D
Kienast
T
T
Seifert
F
F
Schubert
F
F
Heinz
A
A
D000328:Adult; D003071:Cognition / Q000502:physiology*; D005260:Female; D018698:Glutamic Acid / Q000032:analysis / Q000502:physiology*; D006624:Hippocampus / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D011930:Reaction Time; D013826:Theta Rhythm
D018698:Glutamic Acid