Dopaminergic effects on electrophysiological and functional MRI measures of human cortical stimulus-response power laws.
Power laws have been widely used to formulate relationships between objective intensity of stimulation and subjective intensity of sensation. We investigated the effects of dopaminergic drug treatment (sulpiride) on the relationship between somatosensory stimulus intensity and cortical response measured electrophysiologically by somatosensory-evoked potentials (SEP) and functional magnetic resonance imaging (fMRI). The intensity of stimulation was related by a simple power law to both electrophysiological and fMRI measures of cortical response, with overlapping confidence intervals for both power law exponents. Sulpiride did not modulate the power law exponent, but significantly attenuated the "gain" of both stimulus-response functions. Using path analysis we decomposed dopaminergic effects on fMRI data into an indirect component (16%), predictable by drug effects on SEP, and a direct component (84%), not explained electrophysiologically. Results indicate that sulpiride has comparable effects on power law parameters estimated from SEP and fMRI, but fMRI has superior sensitivity to detect drug effects on somatosensory cortical recruitment by graded stimulation.
Wolfson Brain Imaging Centre, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 2QQ, UK.
O J
OJ
Arthurs
C M E
CM
Stephenson
K
K
Rice
V C
VC
Lupson
D J
DJ
Spiegelhalter
S J
SJ
Boniface
E T
ET
Bullmore
D000328:Adult; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D001931:Brain Mapping; D016001:Confidence Intervals; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects* / Q000706:statistics & numerical data; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008432:Mathematical Computing; D008475:Median Nerve / Q000187:drug effects / Q000502:physiology; D008875:Middle Aged; D011999:Recruitment, Neurophysiological / Q000187:drug effects / Q000528:radiation effects; D012684:Sensory Thresholds / Q000187:drug effects / Q000502:physiology; D013003:Somatosensory Cortex / Q000187:drug effects* / Q000502:physiology; D013469:Sulpiride / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D018492:Dopamine Antagonists; D013469:Sulpiride