Functional Signal- and Paradigm-Dependent Linear Relationships between Synaptic Activity and Hemodynamic Responses in Rat Somatosensory Cortex

Linear relationships between synaptic activity and hemodynamic responses are critically dependent on functional signal etiology and paradigm. To investigate these relationships, we simultaneously measured local field potentials (FPs) and optical intrinsic signals in rat somatosensory cortex while de...

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Bibliographic Details
Published in:The Journal of neuroscience 2004-04, Vol.24 (15), p.3850-3861
Main Authors: Nemoto, Masahito, Sheth, Sameer, Guiou, Michael, Pouratian, Nader, Chen, James W. Y, Toga, Arthur W
Format: Article
Language:English
Subjects:
Animals
Behavioral/Systems/Cognitive
Blood Volume - physiology
Brain Mapping
Cerebrovascular Circulation - physiology
Electric Stimulation
Evoked Potentials - physiology
Hindlimb - physiology
Magnetic Resonance Imaging
Male
Microelectrodes
Optics and Photonics
Oxygen - blood
Rats
Rats, Sprague-Dawley
Somatosensory Cortex - anatomy & histology
Somatosensory Cortex - blood supply
Somatosensory Cortex - physiology
Statistics as Topic
Synaptic Transmission - physiology
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Summary:Linear relationships between synaptic activity and hemodynamic responses are critically dependent on functional signal etiology and paradigm. To investigate these relationships, we simultaneously measured local field potentials (FPs) and optical intrinsic signals in rat somatosensory cortex while delivering a small number of electrical pulses to the hindpaw with varied stimulus intensity, number, and interstimulus interval. We used 570 and 610 nm optical signals to estimate cerebral blood volume (CBV) and oxygenation, respectively. The spatiotemporal evolution patterns and trial-by-trial correlation analyses revealed that CBV-related optical signals have higher fidelity to summed evoked FPs (SigmaFPs) than oxygenation-derived signals. CBV-related signals even correlated with minute SigmaFP fluctuations within trials of the same stimulus condition. Furthermore, hemodynamic signals (CBV and late oxygenation signals) increased linearly with SigmaFP while varying stimulus number, but they exhibited a threshold and steeper gradient while varying stimulus intensity, suggesting insufficiency of the homogeneity property of linear systems and the importance of spatiotemporal coherence of neuronal population activity in hemodynamic response formation. These stimulus paradigm-dependent linear and nonlinear relationships demonstrate that simple subtraction-based analyses of hemodynamic signals produced by complex stimulus paradigms may not reflect a difference in SigmaFPs between paradigms. Functional signal- and paradigm-dependent linearity have potentially profound implications for the interpretation of perfusion-based functional signals.
ISSN:0270-6474
1529-2401
DOI:10.1523/JNEUROSCI.4870-03.2004