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L. Bherer

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2 papers

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YNICL Journal 2016 Journal Article

Influence of aerobic exercise training on the neural correlates of motor learning in Parkinson's disease individuals

C. Duchesne
F. Gheysen
A. Bore
G. Albouy
A. Nadeau
M.E. Robillard
F. Bobeuf
A.L. Lafontaine

BACKGROUND: Aerobic exercise training (AET) has been shown to provide general health benefits, and to improve motor behaviours in particular, in individuals with Parkinson's disease (PD). However, the influence of AET on their motor learning capacities, as well as the change in neural substrates mediating this effect remains to be explored. OBJECTIVE: In the current study, we employed functional Magnetic Resonance Imaging (fMRI) to assess the effect of a 3-month AET program on the neural correlates of implicit motor sequence learning (MSL). METHODS: 20 healthy controls (HC) and 19 early PD individuals participated in a supervised, high-intensity, stationary recumbent bike training program (3 times/week for 12 weeks). Exercise prescription started at 20 min (+ 5 min/week up to 40 min) based on participant's maximal aerobic power. Before and after the AET program, participants' brain was scanned while performing an implicit version of the serial reaction time task. RESULTS: Brain data revealed pre-post MSL-related increases in functional activity in the hippocampus, striatum and cerebellum in PD patients, as well as in the striatum in HC individuals. Importantly, the functional brain changes in PD individuals correlated with changes in aerobic fitness: a positive relationship was found with increased activity in the hippocampus and striatum, while a negative relationship was observed with the cerebellar activity. CONCLUSION: Our results reveal, for the first time, that exercise training produces functional changes in known motor learning related brain structures that are consistent with improved behavioural performance observed in PD patients. As such, AET can be a valuable non-pharmacological intervention to promote, not only physical fitness in early PD, but also better motor learning capacity useful in day-to-day activities through increased plasticity in motor related structures.

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YNIMG Journal 2012 Journal Article

Absolute quantification of resting oxygen metabolism and metabolic reactivity during functional activation using QUO2 MRI

C.J. Gauthier
L. Desjardins-Crépeau
C. Madjar
L. Bherer
R.D. Hoge

We have recently described an extension of calibrated MRI, which we term QUO2 (for QUantitative O2 imaging), providing absolute quantification of resting oxidative metabolism (CMRO2) and oxygen extraction fraction (OEF0). By combining BOLD, arterial spin labeling (ASL) and end-tidal O2 measurements in response to hypercapnia, hyperoxia and combined hyperoxia/hypercapnia manipulations, and the same MRI measurements during a task, a comprehensive set of vascular and metabolic measurements can be obtained using a generalized calibration model (GCM). These include the baseline absolute CBF in units of ml/100g/min, cerebrovascular reactivity (CVR) in units of %Δ CBF/mm Hg, M in units of percent, OEF0 and CMRO2 at rest in units of μmol/100g/min, percent evoked CMRO2 during the task and n, the value for flow-metabolic coupling associated with the task. The M parameter is a calibration constant corresponding to the maximal BOLD signal that would occur upon removal of all deoxyhemoglobin. We have previously shown that the GCM provides estimates of the above resting parameters in grey matter that are in excellent agreement with literature. Here we demonstrate the method using functionally-defined regions-of-interest in the context of an activation study. We applied the method under high and low signal-to-noise conditions, corresponding respectively to a robust visual stimulus and a modified Stroop task. The estimates fall within the physiological range of literature values, showing the general validity of the GCM approach to yield non-invasively an extensive array of relevant vascular and metabolic parameters.

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