A control system approach for evaluating somatosensory activation by laser-Doppler flowmetry in the rat cortex.
Coupling between functional cortical activity and blood flow is a regulatory principle that adjusts the supply of substrates to the metabolic needs of the tissue. The flow response is usually expressed as the maximum increase over baseline; control system analysis allows the description of the entire time course and the main dynamic features of the regulative principle. In chloralose-anesthetized rats, forepaws were stimulated by trains of electric pulses of 0.3 or 5 ms duration. Blood flow was recorded in the contralateral somatosensory cortex by laser-Doppler flowmetry and correlated with the amplitude of primary somatosensory evoked potentials (SEP). Changes were analyzed by a control system approach. Pulses of 0.3 or 5 ms evoked SEPs of similar amplitude, whereas flow responses differed: 0.3 ms pulses led to a peak and plateau characteristic, 5 ms pulses evoked a plateau characteristic. The flow response evoked by 0.3 ms pulses can be modeled mathematically by an initial feedforward regulative principle followed after some delay by feedback controlled flow stabilization, whereas 5 ms pulses lack the feedforward component. The absence of an electrophysiological difference points to a dissociation between electrophysiological and hemodynamic responses and may be of importance for the understanding of flow coupling.
Rosengarten
B
B
Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Gleueler Strasse 50, D-50931 Cologne, Germany.
Lutz
H
H
Hossmann
K-A
KA
D000465:Algorithms; D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005246:Feedback / Q000502:physiology; D005528:Foot / Q000294:innervation / Q000502:physiology; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation*; D015233:Models, Statistical; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000098:blood supply / Q000502:physiology*; D013238:Stereotaxic Techniques