Столкновение геополитических интересов НАТО и России в Молдавии

<p>(A) H-reflex modulation recorded in the right FCR muscle of 14 right-handed observers, during observation of one cycle of a flexion-extension movement of the mover’s right hand (B, average movement trace performed by the mover in all different experiments (±SEM), when observers are explicitly instructed to report the mover’s hand position corresponding to the last time the LED light was flashed in each trial. In panel A the cumulative plot of the average data points from all subjects is fitted with a common sinusoid equation with the same period as that fitting the movement. Note the reduced scale of the ordinate compared to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177457#pone.0177457.g002" target="_blank">Fig 2A</a>. Δϕ: phase difference between reflex modulation in flexor muscle of the observer and hand oscillation of the mover. Flex = downward direction of the moving hand.</p

The role of attention in human motor resonance

<div><p>Observation of others' actions evokes in primary motor cortex and spinal circuits of observers a subliminal motor resonance response, which reflects the motor program encoding observed actions. We investigated the role of attention in human motor resonance with four experimental conditions, explored in different subject groups: in the first <i>explicit</i> condition, subjects were asked to observe a rhythmic hand flexion-extension movement performed live in front of them. In two other conditions subjects had to monitor the activity of a LED light mounted on the oscillating hand. The hand was clearly visible but it was not the focus of subjects’ attention: in the <i>semi-implicit</i> condition hand movement was relevant to task completion, while in the <i>implicit</i> condition it was irrelevant. In a fourth, <i>baseline</i>, condition subjects observed the rhythmic oscillation of a metal platform. Motor resonance was measured with the H-reflex technique as the excitability modulation of cortico-spinal motorneurons driving a hand flexor muscle. As expected, a normal resonant response developed in the <i>explicit</i> condition, and no resonant response in the <i>baseline</i> condition. Resonant responses also developed in both <i>semi-implicit</i> and <i>implicit</i> conditions and, surprisingly, were not different from each other, indicating that viewing an action is, <i>per se</i>, a powerful stimulus for the action observation network, even when it is not the primary focus of subjects’ attention and even when irrelevant to the task. However, the amplitude of these responses was much reduced compared to the <i>explicit</i> condition, and the phase-lock between the time courses of observed movement and resonant motor program was lost. In conclusion, different parameters of the response were differently affected by subtraction of attentional resources with respect to the <i>explicit</i> condition: time course and muscle selection were preserved while the activation of motor circuits resulted in much reduced amplitude and lost its kinematic specificity.</p></div

Phase differences between observed movement and H-reflex modulation.

<p>Derived in each subject from the sinewave function fitting the subject’s average data points in the <i>explicit</i>, <i>semi-implicit</i> and <i>implicit</i> observation conditions. Note that in the <i>explicit</i> condition phases are always in advance of the observed movement (as in the actual execution of the same movement), whereas in the <i>semi-implicit</i> and <i>implicit</i> conditions they are scattered across the entire possible range (-180° to +180°).</p

Sinusoidal time-course of reflex amplitude modulation.

<p>Average correlation coefficients of the circular-linear analysis (±SEM) obtained in the <i>explicit</i>, <i>semi-implicit</i> and <i>implicit</i> conditions are significantly different from the R coefficients obtained in the <i>baseline</i> condition (** p≤0.01, ***p≤0.001).</p

Data acquisition and experimental protocol.

<p>(A) Average traces (μV ±SEM) of 25 H-reflexes recorded from a single subject, in a single trial of movement observation in the <i>explicit</i> condition. (B) Average sinusoidal time course of 25 flexion-extension hand movements. Black dots on the sinewave indicate the 5 different delays during the hand flexion-extension cycle in which reflexes were recorded (d1 = 0, d2 = 200, d3 = 400, d4 = 600, d5 = 800 ms) corresponding to 5 different hand angular positions, dividing the 1Hz oscillation cycle in five equal parts. Note the motor resonant response, i.e. the modulation of the reflex amplitude matches the cyclic time course of the observed movement, with smaller reflexes recorded during observation of the extension phase (e.g. d1 and d5) and larger ones during the observation of the flexion phase (e.g. d3 and d4).</p

Amplitude of H-reflex modulation.

<p>Derived in each subject from the sinewave function fitting the subject’s average data points in the <i>explicit</i>, <i>semi-implicit</i> and <i>implicit</i> observation conditions, the average H-reflex amplitude modulation (± SEM) is significantly larger in the <i>explicit</i> condition compared to each of the other conditions, and is significantly smaller in the <i>baseline</i> condition compared to the <i>semi-implicit</i> and <i>implicit</i> conditions, which were not different from each other (***p<0.001).</p