Cardiorespiratory and Emotional Responses During Balance Exercises.

Purpose: Physical exercises on unstable surfaces have been largely applied for clinical practice as well as in sports training. Although the unsteadiness can lead to physiological and psychological adaptations, little is known about the autonomic and emotional acute responses during the practice of balance exercises. This study aimed to evaluate both cardiorespiratory and emotional responses while standing on different unstable surfaces. Methods: Eighty-eight healthy participants performed postural balance tasks in three experimental conditions: (1) a rigid surface (control); (2) balance pad; and (3) the Both Sides Up (BOSU) ball. Respiratory activity was recorded through the thoracic movement and the heart rate variability by the electrocardiographic signal during the balance tasks. After the participants evaluated the level of perceived stability and emotional aspects related to each experimental condition. Results: The main results showed that BOSU condition was perceived as more unstable, unpleasant, with higher arousal and lower dominance levels (p < .05). Accordingly, participants had also an increase in the mean respiratory frequency and heart rate (p < .05). Conclusion: These results showed that the postural task with greater instability prompted congruent physiological adjustments to ensure the homeostasis in the more challenging condition. Therefore, the cardiorespiratory and emotional responses should be considered to ensure the safety and benefits in rehabilitation programs in which the exercise progression is based on unstable surfaces.

Implicit action prediction constrains observed biological action reconstruction.

Voluntary movements include a predictive control of the sensory-motor consequences of executed or observed actions. The motor system predicts further steps of actions relying on its pure observation. This study seeks to disclose the interference of an implicit motor prediction effect during actions reconstruction. Videos of human actions directed to objects were presented to volunteers. Subsequently, they combined four static frames of those videos randomly arranged on the screen. Such combination could be chronological (from the beginning to the end of the action) or reverse (from the end to the beginning of the action). The observed actions were also biological (human movement) or non-biological (movement of objects). The grasping began with the actor's hand in a resting position over a table (Experiment I), or with his hand in contact with the object (Experiment II). In the first experiment, participants presented lower accuracy in the biological condition rearranging in chronological order. In the second experiment, however, the accuracy was lower in reverse order. The interpretation of such results is that the implicit predictive mechanisms interfered in the rearrangement of the frames. As an example: the expected movement after a grasping action whose outcome is capping a bottle would be the withdrawal of the hand. Therefore, combining frames of a recent seen action, volunteers present less accuracy if the first frame to be placed is counterintuitive.

Emotional categorization of objects: A novel clustering approach and the effect of depression.

Most everyday actions engender interactions with meaningful emotionally-laden stimuli. This study aimed to select pictures of objects as emotional stimulus of affordance to be grasped. The participant's depression trait was also assessed to examine its effect on the judgment of these pictures, and time spent in the classification was computed. Sixty-three participants joined this study. Self-Assessment-Manikin scale was used to classify pictures of the objects, and Beck Depression Inventory was applied to distribute the sample according depression trait. Cluster analysis was used in the classification of 123 objects based on valence and arousal values. Cluster results returned 102 classified pictures in three categories: pleasant (21), neutral (48) and unpleasant (33). Where cluster analysis did not agree, the picture was excluded and not used any further (21). Pleasant pictures presented the highest valence values and unpleasant pictures the lowest, and both categories returned the highest arousal level. In the middle of the valence range, the neutral category evoked the lowest arousal levels. Participants were slower to classify unpleasant pictures in valence sub-scale and faster to classify neutral pictures in arousal one. There was no effect of depression in the response time needed to score the pictures. Thus, agreement of high-performance soft clustering algorithms emerged as a good tool to classify pictures representing objects based on valence and arousal dimensions. Depression trait does not significantly affect the accuracy or time-order of emotional classification. Finally, we presented a set of emotional stimuli that can be employed to examine distinct aspects of emotion over physiology and behavior.

Observing Grasping Actions Directed to Emotion-Laden Objects: Effects upon Corticospinal Excitability.

The motor system is recruited whenever one executes an action as well as when one observes the same action being executed by others. Although it is well established that emotion modulates the motor system, the effect of observing other individuals acting in an emotional context is particularly elusive. The main aim of this study was to investigate the effect induced by the observation of grasping directed to emotion-laden objects upon corticospinal excitability (CSE). Participants classified video-clips depicting the right-hand of an actor grasping emotion-laden objects. Twenty video-clips differing in terms of valence but balanced in arousal level were selected. Motor evoked potentials (MEPs) were then recorded from the first dorsal interosseous using transcranial magnetic stimulation (TMS) while the participants observed the selected emotional video-clips. During the video-clip presentation, TMS pulses were randomly applied at one of two different time points of grasping: (1) maximum grip aperture, and (2) object contact time. CSE was higher during the observation of grasping directed to unpleasant objects compared to pleasant ones. These results indicate that when someone observes an action of grasping directed to emotion-laden objects, the effect of the object valence promotes a specific modulation over the motor system.

Motor imagery modulation of body sway is task-dependent and relies on imagery ability.

In this study we investigate to what extent the effects of motor imagery on postural sway are constrained by movement features and the subject's imagery ability. Twenty-three subjects were asked to imagine three movements using the kinesthetic modality: rising on tiptoes, whole-body forward reaching, and whole-body lateral reaching. After each task, subjects reported the level of imagery vividness and were subsequently grouped into a HIGH group (scores ≥3, "moderately intense" imagery) or a LOW group (scores ≤2, "mildly intense" imagery). An eyes closed trial was used as a control task. Center of gravity (COG) coordinates were collected, along with surface EMG of the deltoid (medial and anterior portion) and lateral gastrocnemius muscles. COG variability was quantified as the amount of fluctuations in position and velocity in the forward-backward and lateral directions. Changes in COG variability during motor imagery were observed only for the HIGH group. COG variability in the forward-backward direction was increased during the rising on tiptoes imagery, compared with the control task (p = 0.01) and the lateral reaching imagery (p = 0.02). Conversely, COG variability in the lateral direction was higher in rising on tiptoes and lateral reaching imagery than during the control task (p < 0.01); in addition, COG variability was higher during the lateral reaching imagery than in the forward reaching imagery (p = 0.02). EMG analysis revealed no effects of group (p > 0.08) or task (p > 0.46) for any of the tested muscles. In summary, motor imagery influences body sway dynamics in a task-dependent manner, and relies on the subject' imagery ability.

Distribution and morphology of nitrergic neurons across functional domains of the rat primary somatosensory cortex.

The rat primary somatosensory cortex (S1) is remarkable for its conspicuous vertical compartmentalization in barrels and septal columns, which are additionally stratified in horizontal layers. Whereas excitatory neurons from each of these compartments perform different types of processing, the role of interneurons is much less clear. Among the numerous types of GABAergic interneurons, those producing nitric oxide (NO) are especially puzzling, since this gaseous messenger can modulate neural activity, synaptic plasticity, and neurovascular coupling. We used a quantitative morphological approach to investigate whether nitrergic interneurons, which might therefore be considered both as NO volume diffusers and as elements of local circuitry, display features that could relate to barrel cortex architecture. In fixed brain sections, nitrergic interneurons can be revealed by histochemical processing for NADPH-diaphorase (NADPHd). Here, the dendritic arbors of nitrergic neurons from different compartments of area S1 were 3D reconstructed from serial 200 µm thick sections, using 100x objective and the Neurolucida system. Standard morphological parameters were extracted for all individual arbors and compared across columns and layers. Wedge analysis was used to compute dendritic orientation indices. Supragranular (SG) layers displayed the highest density of nitrergic neurons, whereas layer IV contained nitrergic neurons with largest soma area. The highest nitrergic neuronal density was found in septa, where dendrites were previously characterized as more extense and ramified than in barrels. Dendritic arbors were not confined to the boundaries of the column nor layer of their respective soma, being mostly double-tufted and vertically oriented, except in SG layers. These data strongly suggest that nitrergic interneurons adapt their morphology to the dynamics of processing performed by cortical compartments.

Preparing to grasp emotionally laden stimuli.

BACKGROUND: Contemporary theories of motor control propose that motor planning involves the prediction of the consequences of actions. These predictions include the associated costs as well as the rewarding nature of movements' outcomes. Within the estimation of these costs and rewards would lie the valence, that is, the pleasantness or unpleasantness of a given stimulus with which one is about to interact. The aim of this study was to test if motor preparation encompasses valence. METHODOLOGY/PRINCIPAL FINDINGS: The readiness potential, an electrophysiological marker of motor preparation, was recorded before the grasping of pleasant, neutral and unpleasant stimuli. Items used were balanced in weight and placed inside transparent cylinders to prompt a similar grip among trials. Compared with neutral stimuli, the grasping of pleasant stimuli was preceded by a readiness potential of lower amplitude, whereas that of unpleasant stimuli was associated with a readiness potential of higher amplitude. CONCLUSIONS/SIGNIFICANCE: We show for the first time that the sensorimotor cortex activity preceding the grasping of a stimulus is affected by its valence. Smaller readiness potential amplitudes found for pleasant stimuli could imply in the recruitment of pre-set motor repertoires, whereas higher amplitudes found for unpleasant stimuli would emerge from a discrepancy between the required action and their aversiveness. Our results indicate that the prediction of action outcomes encompasses an estimate of the valence of a stimulus with which one is about to interact.