Imaging Neurovascular Function and Functional Recovery after Stroke in the Rat Striatum Using Forepaw Stimulation

Abstract

Negative functional magnetic resonance imaging (fMRI) response in the striatum has been observed in several studies during peripheral sensory stimulation, but its relationship between local field potential (LFP) remains to be elucidated. We performed cerebral blood volume (CBV) fMRI and LFP recordings in normal rats during graded noxious forepaw stimulation at nine stimulus pulse widths. Albeit high LFP-CBV correlation was found in the ipsilateral and contralateral sensory cortices (r ¼ 0.89 and 0.95, respectively), the striatal CBV responses were neither positively, nor negatively correlated with LFP (r ¼ 0.04), demonstrating that the negative striatal CBV response is not originated from net regional inhibition. To further identify whether this negative CBV response can serve as a marker for striatal functional recovery, two groups of rats (n ¼ 5 each) underwent 20-and 45-minute middle cerebral artery occlusion (MCAO) were studied. No CBV response was found in the ipsilateral striatum in both groups immediately after stroke. Improved striatal CBV response was observed on day 28 in the 20-minute MCAO group compared with the 45-minute MCAO group (Po0.05). This study shows that fMRI signals could differ significantly from LFP and that the observed negative CBV response has potential to serve as a marker for striatal functional integrity in rats.

Functional circuit mapping of striatal output nuclei using simultaneous deep brain stimulation and fMRI

“…Although it may be intuitive to interpret our data as DBS-evoked neuronal inhibition, the situation appears to be particularly muddled in striatum, wherein dopaminergic neurotransmission has been hypothesized to induce vasoconstriction independent of direct activity changes within striatal neurons (Hsu et al, 2014) or regional metabolism (Shih et al, 2011). In addition, striatal CBV decreases have previously been shown with heightened local neuronal activity, as observed in rats during noxious forepaw stimulation (Shih et al, 2009; Shih et al, 2014a), or epileptic slow-wave discharge (Mishra et al, 2011). In light of these complexities, further work will be necessary to determine the underlying mechanism of striatal CBV decreases evoked during GPe- and SNr-DBS.…”

Role of Genetic Variation in Collateral Circulation in the Evolution of Acute Stroke

“…25 Images were skull-stripped, co-registered across subjects and analyzed using established protocols that we published previously. 26, 27 Specifically, CBF was calculated from CSL data using $\mathit{CBF}=\frac{false(\lambda /T_{1}false)false(S_C-S_{L}false)}{false(S_L+false(2\alpha -1false)S_{C}false)}$, where S C and S L are the MR signal intensities from the control and labeled images, respectively. λ is the water brain-blood partition coefficient, T 1 is that of tissue, and α is the arterial spin-labeling efficiency.…”

Enhancing endogenous capacity to repair a stroke-damaged brain: An evolving field for stroke research

“…The changes of neurovascular coupling also dynamically occur after focal cerebral ischemia and during recovery. Monitoring neurovascular coupling through cerebral blood volume fMRI and local field potential (LFP) after forepaw stimulation, Shih and coworkers (Shih et al, 2014) reported that both the fMRI and LFP responses in the cortex and striatum of the affected hemisphere were diminished immediately after stroke and recovered on day 28 after experimental stroke. In agreement with the experimental findings, an fMRI study in chronic stroke patients has revealed that an increase of regional cerebral blood flow is positively correlated to a significant recovery in speech and limb motor function (Mountz, 2007).…”