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  • Title: A control system approach for evaluating somatosensory activation by laser-Doppler flowmetry in the rat cortex.
    Author: Rosengarten B, Lutz H, Hossmann KA.
    Journal: J Neurosci Methods; 2003 Nov 30; 130(1):75-81. PubMed ID: 14583406.
    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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