GABA and cortical inhibition in motor and non-motor regions using combined TMS-EEG: a time analysis.
OBJECTIVE
The induction of long interval cortical inhibition (LICI) in motor cortex with paired pulse transcranial magnetic stimulation (ppTMS) is an established paradigm for the assessment of cortical inhibition, proposed to be related to GABA(B) receptor inhibitory neurotransmission. This study aimed to further evaluate recent methods of the assessment of LICI in non motor regions with ppTMS and electroencephalography (EEG).


METHODS
ppTMS was applied using a single coil to the motor and dorsolateral prefrontal cortex (DLPFC) in 14 healthy subjects, and in the parietal lobe in 5 of those subjects.


RESULTS
In the motor cortex, LICI resulted in significant suppression in mean cortical evoked activity on EEG between 75 and 250 ms following delivery of the test stimulus. Maximal inhibition was seen from 50 to 250 ms in DLPFC, and between 50 and 175 ms in the parietal lobe.


CONCLUSIONS
ppTMS may be used to produce LICI in several cortical regions with a time course similar to known GABA(B) activity.


CONCLUSIONS
ppTMS induction of LICI can be recorded by combining TMS with EEG and seems to relate to GABA(B) activity.
Fitzgerald
Paul B
PB
Monash Alfred Psychiatry Research Centre, The Alfred and Monash University School of Psychology, Psychiatry and Psychological Medicine, Melbourne, Vic. 3004, Australia. paul.fitzgerald@med.monash.edu.au
Maller
Jerome J
JJ
Hoy
Kate
K
Farzan
Faranak
F
Daskalakis
Zafiris J
ZJ
D000328:Adult; D018692:Antimanic Agents / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D004569:Electroencephalography / Q000187:drug effects; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects / Q000502:physiology*; D010296:Parietal Lobe / Q000187:drug effects; D017397:Prefrontal Cortex / Q000187:drug effects; D018080:Receptors, GABA-B / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000187:drug effects; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018692:Antimanic Agents; D018080:Receptors, GABA-B; D005680:gamma-Aminobutyric Acid; D018021:Lithium Chloride