The effect of attenuating noradrenergic neurotransmission by clonidine on brain activity measures of visuospatial attention.
OBJECTIVE
In the current study, we investigated the role of noradrenaline in directing (bias) and disengagement of visuospatial attention.


METHODS
We assessed the effect of clonidine on event-related brain potential (ERP) reflections of bias and disengagement in a double-blind placebo-controlled crossover design. An initial dose of 200-μg clonidine was replaced by 100 μg because of marked side effects. Twenty-one healthy male participants performed the visual-spatial cueing task while an electroencephalogram (EEG) was recorded. The behavioral output is the validity effect (benefit of cueing in terms of reaction time to targets). ERP indices for bias were the cue-related early directing attention negativity and late directing attention positivity, and the target-elicited P1 and N1 modulations by validity ('validity-effect'). The ERP index for disengagement was the target-elicited 'late positive deflection' modulation by validity. Behavioral analyses were performed on 16 participants, electrophysiological analyses on a subset (n=9).


RESULTS
Clonidine attenuated the N1 effect, albeit in a subsample. Neither cue-elicited ERPs nor the behavioral validity effect were affected. Clonidine-induced blood pressure reduction was correlated with the reduction of the late positive deflection effect under clonidine.


CONCLUSIONS
Clonidine attenuated the result of bias in a subsample and may have a modulating effect on disengagement.
H N Alexander
HN
Logemann
Koen B E
KB
Böcker
Peter K H
PK
Deschamps
Chantal
C
Kemner
J Leon
JL
Kenemans
D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology; D000328:Adult; D001288:Attention / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology*; D018592:Cross-Over Studies; D003463:Cues; D004311:Double-Blind Method; D004569:Electroencephalography; D005071:Evoked Potentials / Q000187:drug effects; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D011597:Psychomotor Performance; D011930:Reaction Time / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects; D055815:Young Adult
D058647:Adrenergic alpha-2 Receptor Agonists; D003000:Clonidine; D009638:Norepinephrine