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A control system approach for evaluating somatosensory activation by laser-Doppler flowmetry in the rat cortex

Journal of Neuroscience Methods
Publication Date
DOI: 10.1016/s0165-0270(03)00209-7
  • Laser-Doppler Flow
  • Somatosensory Stimulation
  • Activity-Flow Coupling
  • Functional Activation
  • Cerebral Blood Flow
  • Metabolism
  • Biology
  • Mathematics


Abstract 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.

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