Neurovascular coupling has never been investigated with high frequency DBS.
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We studied it using simultaneous optical imaging and electrophysiology in rat M1.
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Thalamic DBS increased both neural activity and perfusion in M1.
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M1 vascular and neural response both saturated at higher DBS frequencies.
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DBS-evoked vascular response represents both evoked potential and MU activity.
Abstract
Background
Deep brain stimulation (DBS) is an effective treatment for movement disorders, yet its mechanisms of action remain unclear. One method used to study its circuit-wide neuromodulatory effects is functional magnetic resonance imaging (fMRI) which measures hemodynamics as a proxy of neural activity. To interpret functional imaging data, we must understand the relationship between neural and vascular responses, which has never been studied with the high frequencies used for DBS.
Objective
To measure neurovascular coupling in the rat motor cortex during thalamic DBS.
Method
Simultaneous intrinsic optical imaging and extracellular electrophysiology was performed in the motor cortex of urethane-anesthetized rats during thalamic DBS at 7 different frequencies. We related Maximum Change in Reflectance (MCR) from the imaging data to Integrated Evoked Potential (IEP) and change in broadband power of multi-unit (MU) activity, computing Spearman’s correlation to determine the strength of these relationships. To determine the source of these effects, we studied the contributions of antidromic versus orthodromic activation in motor cortex perfusion using synaptic blockers.
Results
MCR, IEP and change in MU power increased linearly to 60 Hz and saturated at higher frequencies of stimulation. Blocking orthodromic transmission only reduced the DBS-induced change in optical signal by ∼25%, suggesting that activation of corticofugal fibers have a major contribution in thalamic-induced cortical activation.
Conclusion
DBS-evoked vascular response is related to both evoked field potentials as well as multi-unit activity.