Discrete and Effortful Imagined Movements Do Not Specifically Activate the Autonomic Nervous System

International audienceBACKGROUND: The autonomic nervous system (ANS) is activated in parallel with the motor system during cyclical and effortful imagined actions. However, it is not clear whether the ANS is activated during motor imagery of discrete movements and whether this activation is specific to the movement being imagined. Here, we explored these topics by studying the baroreflex control of the cardiovascular system. METHODOLOGY/PRINCIPAL FINDINGS: Arterial pressure and heart rate were recorded in ten subjects who executed or imagined trunk or leg movements against gravity. Trunk and leg movements result in different physiological reactions (orthostatic hypotension phenomenon) when they are executed. Interestingly, ANS activation significantly, but similarly, increased during imagined trunk and leg movements. Furthermore, we did not observe any physiological modulation during a control mental-arithmetic task or during motor imagery of effortless movements (horizontal wrist displacements). CONCLUSIONS/SIGNIFICANCE: We concluded that ANS activation during motor imagery is general and not specific and physiologically prepares the organism for the upcoming effortful action

Discrete and Effortful Imagined Movements Do Not Specifically Activate the Autonomic Nervous System

Background: The autonomic nervous system (ANS) is activated in parallel with the motor system during cyclical and effortful imagined actions. However, it is not clear whether the ANS is activated during motor imagery of discrete movements and whether this activation is specific to the movement being imagined. Here, we explored these topics by studying the baroreflex control of the cardiovascular system. Methodology/Principal Findings: Arterial pressure and heart rate were recorded in ten subjects who executed or imagined trunk or leg movements against gravity. Trunk and leg movements result in different physiological reactions (orthostatic hypotension phenomenon) when they are executed. Interestingly, ANS activation significantly, but similarly, increased during imagined trunk and leg movements. Furthermore, we did not observe any physiological modulation during a control mental-arithmetic task or during motor imagery of effortless movements (horizontal wrist displacements). Conclusions/Significance: We concluded that ANS activation during motor imagery is general and not specific and physiologically prepares the organism for the upcoming effortful action

Data recording.

<p>Typical data of EMG activity, Arterial Pressure (AP) and Heart Rate (HR) are illustrated for the <i>rest</i>, the <i>movement</i> and the <i>posture</i> phases during an executed movement.</p

Normalized values of Arterial Pressure (AP) and Heart Rate (HR).

<p>The distribution of normalized values of AP (AP = MP_AP/R_AP ×100−100) and HR (HR = MP_HR/R_HR ×100−100) are shown for the imagined <i>trunk</i> and <i>leg</i> movements. Arrows represent the proportion of positive (grey bars) and negative (white bars) normalized values. MP_AP: average AP during the <i>movement</i> and the <i>posture</i> phases; R_AP: average AP during the <i>rest</i> phase; MP_HR: average HR during the <i>movement</i> and the <i>posture</i> phases: R_HR: average HR during the <i>rest</i> phase.</p

Heart rate (HR) during control conditions.

<p>(A) Average values (±SD) of HR for the <i>cognitive</i> (C) task and the <i>rest</i> (R) condition. (B) Average values (±SD) of HR for the <i>executed</i> (E) and <i>imagined</i> (I) wrist movements and for the <i>rest</i> (R) condition.</p

EMG patterns.

<p>Typical EMG patterns from one participant are depicted for executed (E) and imagined (I) <i>trunk</i> and <i>legs</i> movements during the <i>rest</i> (R), the <i>movement</i> (M) and the <i>posture</i> (P) phases. S: Sternocleidomastoideus, RA: Rectus Abdominis, RF: Rectus Femoris.</p

Arterial pressure (AP) and heart rate (HR).

<p>Average values (±SD) of AP and HR during the <i>rest</i> (R), the <i>movement</i> (M) and the <i>posture</i> (P) phases are illustrated for both <i>trunk</i> (white bars) and <i>leg</i> movements (grey bars). (A–B) <i>executed</i> movements. (C–D) <i>imagined</i> movements. Stars (*) indicate significant differences (<i>p</i><.05).</p