Publications
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Temporally staggered forelimb stimulation modulates barrel cortex optical intrinsic signal responses to whisker stimulation
Source: Journal of Neurophysiology 2002 Jul;88(1):422-437.
Author: Blood A, Pouratian N, Toga AW.
PubMed ID: 12091565
Abstract:
Characterization of cortical modulation properties and neurovascular relationships is critical to our understanding of brain function. We have previously observed uncoupling of optical intrinsic signal imaging (OIS) and evoked potential (EP) responses in rodent barrel cortex following simultaneous whisker and forelimb stimulation. To test the hypothesis that this uncoupling may have resulted from ‘passive’ overspill of perfusion-related responses between functional regions, we conducted the present study using temporally staggered, rather than simultaneous whisker and forelimb stimulation. This paradigm minimized overlap of neural responses in barrel cortex and forelimb SI, while maintaining overlap of vascular response timecourses between regions. When forelimb stimulation either preceded or followed whisker stimulation, barrel cortex OIS response timecourse broadened and time-to-peak shifted in the temporal direction of the forelimb stimulus. In contrast with OIS and EP magnitude decreases previously observed during simultaneous stimulation, barrel cortex OIS response magnitude during staggered stimulation increased, and no detectable changes in underlying EP activity were observed. Spatial extent of barrel cortex OIS responses also increased during staggered stimulation. These findings provide evidence for ‘passive’ overspill of perfusion-related responses into regions distinct from those which are functionally active, and emphasize the importance of stimulus timing on OIS response modulation. It will be important to consider potential influences of ‘passive’ vascular overspill when designing and interpreting functional imaging studies which use hemodynamic responses to infer underlying neural activity.
Source: Journal of Neurophysiology 2002 Jul;88(1):422-437.
Author: Blood A, Pouratian N, Toga AW.
PubMed ID: 12091565
Abstract:
Characterization of cortical modulation properties and neurovascular relationships is critical to our understanding of brain function. We have previously observed uncoupling of optical intrinsic signal imaging (OIS) and evoked potential (EP) responses in rodent barrel cortex following simultaneous whisker and forelimb stimulation. To test the hypothesis that this uncoupling may have resulted from ‘passive’ overspill of perfusion-related responses between functional regions, we conducted the present study using temporally staggered, rather than simultaneous whisker and forelimb stimulation. This paradigm minimized overlap of neural responses in barrel cortex and forelimb SI, while maintaining overlap of vascular response timecourses between regions. When forelimb stimulation either preceded or followed whisker stimulation, barrel cortex OIS response timecourse broadened and time-to-peak shifted in the temporal direction of the forelimb stimulus. In contrast with OIS and EP magnitude decreases previously observed during simultaneous stimulation, barrel cortex OIS response magnitude during staggered stimulation increased, and no detectable changes in underlying EP activity were observed. Spatial extent of barrel cortex OIS responses also increased during staggered stimulation. These findings provide evidence for ‘passive’ overspill of perfusion-related responses into regions distinct from those which are functionally active, and emphasize the importance of stimulus timing on OIS response modulation. It will be important to consider potential influences of ‘passive’ vascular overspill when designing and interpreting functional imaging studies which use hemodynamic responses to infer underlying neural activity.