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1 Department of Health Care Sciences, University of Texas Southwestern, Dallas, Texas, USA
2 Department of Radiology, University of Texas Southwestern, Dallas, Texas, USA
* To whom correspondence should be addressed. E-mail: jon.williamson{at}utsouthwestern.edu.
The purpose of this investigation was to determine if central command activated regions of the insular cortex, independent of muscle metaboreflex activation and blood pressure elevations. Subjects (n = 8) were studied during i.) rest with cuff occlusion; ii.) static handgrip exercise (SHG) sufficient to increase mean blood pressure (MBP) by 15 mmHg and iii.) post-SHG exercise cuff occlusion (PECO) to sustain the 15 mmHg BP increase. Data were collected for HR, MBP, ratings of perceived exertion (RPE) and discomfort (RPD) and regional cerebral blood flow (rCBF) using single photon computed tomography (SPECT). Comparing time periods when MBP was matched during SHG and PECO, HR (+7 ±3 bpm; p < 0.05) and RPE (15 ±2 units; p < 0.05) were higher for SHG. During SHG, there were significant increases in rCBF for hand sensorimotor (+9 ±3%), right inferior posterior insula (+7 ±3%), left inferior anterior insula (+8 ±2%) and anterior cingluate regions (+6 ±2%), not found during PECO. There was significant activation of the inferior (ventral) thalamus and right inferior anterior insular for both SHG and PECO. Although prior studies have shown regions of the insular cortex can be activated independent of mechanoreflex input, it was not presently assessed. These findings provide evidence that there are rCBF changes within regions of the insular and anterior cingulate cortices related to central command 'per se' during handgrip exercise, independent of metaboreflex activation and blood pressure elevation.
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