Movement-related Events Research Articles

Comparison of methods of derivation of the yank-time signal from the vertical ground reaction force–time signal for identification of movement-related events

Temporal changes in ground reaction force magnitudes reflect movement strategy, and thus underlying muscle activation patterns, during movement tasks. Speculatively, these changes may be observed more readily when the force–time signal is differentiated, yielding the yank-time signal. However, the differentiation process, including the signal filtering used before or after differentiation, can significantly affect the signal-to-noise ratio (SNR) and likelihood of meaningful inference. The aim of the present study was to compare three methods of deriving the yank-time signal: Method 1 derived the yank-time signal using 2nd-order central differentiation subsequent to application of a 4th-order Butterworth filter; Method 2 included the same process as Method 1 but additionally filtered the yank-time data with a Savitzky-Golay smoothing filter; and Method 3 directly and simultaneously derived and smoothed the yank-time signal using a Savitzky-Golay digital differentiation filter. The current analyses revealed Method 2 had the best SNR, followed by Methods 3 and 1, but caused a small loss of signal amplitude. With regards to timing of inflection points in the yank-time data, no significant difference was observed. Therefore, Method 3 led to the best derivation of the yank-time signal due to its efficiency and preservation of signal characteristics and good SNR. Also, a strong association between the first maximum point of the yank-time signal and the start of the downward movement of the body’s centre of mass during a countermovement jump, as identified by 3-D motion analysis, was observed. Thus, subtle events (e.g. start of downward movement) can be easily observed in the yank-time signal.

Temporally restricted dopaminergic control of reward-conditioned movements.

Midbrain dopamine (DA) neurons encode both reward and movement-related events, and are implicated in disorders of reward processing as well as movement. Consequently, disentangling the contribution of DA neurons in reinforcing versus generating movements is challenging and has led to lasting controversy. We dissociated these functions by parametrically varying the timing of optogenetic manipulations in a Pavlovian conditioning task, and examining the influence on anticipatory licking prior to reward delivery. Inhibiting both ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) DA neurons in the post-reward period had a significantly greater behavioral effect than inhibition in the pre-reward period of the task. Furthermore, the contribution of DA neurons to behavior decreased linearly as a function of elapsed time after reward. Together, the results indicate a temporally restricted role of DA neurons primarily related to reinforcing stimulus-reward associations, and suggest that directly generating movements is a comparatively less important function.

Activation Modeling and Classification of Voluntary and Imagery Movements From the Prefrontal fNIRS Signals

The trends in movement-related functional activity measurement for brain-computer interface (BCI) are mostly associated with the central lobe of the brain. This consideration may be a faulty approach for the paralyzed patient. This limitation demands an alternative approach for movement-related BCI. For the first time, we propose the prefrontal hemodynamics for implementing movement-related BCI. This paper aims to model the activation pattern and the classification performances of the prefrontal hemodynamics regarding the movement-related events. Utilizing functional near-infrared spectroscopy (fNIRS) the changes in the concentration of the oxidized hemoglobin and deoxidized hemoglobin regarding voluntary and imagery movements are acquired. With necessary preprocessing, the fNIRS signals are statistically analyzed to localize the most significant activated regions regarding the applied stimuli. The experiment shows that movement-related events have a strong correlation with the prefrontal hemodynamics. The patterns of the movement-related hemodynamics are modeled by polynomial regression and used to classify the voluntary and imagery events based on the maximum similarity approach. The resulting classification accuracies are found promising that proves the effectiveness of the prefrontal fNIRS signal to be effective in movement-related brain functionality analysis.

Use of electric field sensors for recording respiration, heart rate, and stereotyped motor behaviors in the rodent home cage

BackgroundNumerous environmental and genetic factors can contribute significantly to behavioral and cardiorespiratory variability observed experimentally. Affordable technologies that allow for noninvasive home cage capture of physio-behavioral variables should enhance understanding of inter-animal variability including after experimental interventions. New methodWe assessed whether EPIC electric field sensors (Plessey Semiconductors) embedded within or attached externally to a rodent’s home cage could accurately record respiration, heart rate, and motor behaviors. Comparison with existing methodsCurrent systems for quantification of behavioral variables require expensive specialty equipment, while measures of respiratory and heart rate are often provided by surgically implanted or chronically affixed devices. ResultsSensors accurately encoded imposed sinusoidal changes in electric field tested at frequencies ranging from 0.5–100Hz. Mini-metronome arm movements were easily detected, but response magnitude was highly distance dependent. Sensors accurately reported respiration during whole-body plethysmography. In anesthetized rodents, PVC tube-embedded sensors provided accurate mechanical detection of both respiratory and heart rate. Comparable success was seen in naturally behaving animals at rest or sleeping when sensors were attached externally. Video-verified motor behaviors (sniffing, grooming, chewing, and rearing) were detectable and largely separable by their characteristic voltage fluctuations. Larger movement-related events had comparably larger voltage dynamics that easily allowed for a broad approximation of overall motor activity. Spectrograms were used to quickly depict characteristic frequencies in long-lasting recordings, while filtering and thresholding software allowed for detection and quantification of movement-related physio-behavioral events. ConclusionsEPIC electric field sensors provide a means for affordable non-contact home cage detection of physio-behavioral variables.

Grip force scaling and sequencing of events during a manipulative task in Huntington's disease

The aim of the study was to investigate force regulation and sequencing of events in Huntington's disease (HD) patients when performing a drawer opening task using the precision grip. Results revealed that HD patients used excessive grip force levels that were unrelated to the actual task demands. Also, they demonstrated a higher grip force value at load force onset in addition to an increased delay between initiation of grip force and load (pulling) force. These data indicate a deficit in the coordinated activation of both forces due to HD. Furthermore, the patients showed bradykinesia along with a prolonged interval between the movement phases underlying the task, denoting an impairment in encoding serially ordered events. Together, these results illustrate the deteriorating effect of striatal pathology on manual function. Accordingly, an amended control of grasping forces and serial encoding of movement-related events due to HD are likely to affect the proficiency of common manipulative skills.

Presence of Very Early Events Preceding Self-Paced Movements in Epileptic Patients. An Intracerebral Exploration

In epileptic patients explored with depth electrodes kept within the brain for several days (“chronic conditions”) to localize their focus, recordings were taken from the less perturbed deep brain areas, before and during the execution of self-paced movements. A few deep leads (some of which were located in areas which did not display a classical readiness potential) showed that phasic paroxystic events very often occurred 2,000 ms and, sometimes, even about 3,000 ms before the movement (movement-related events, MREs). This finding suggests that the preparation of a “voluntary” self-paced movement may begin well before the appearance of the readiness potential or, alternatively, that intracerebral paroxystic spikes delay the decision making. This type of phasic process may be undetectable in scalp recording from normal subjects and only be revealed when some brain structures have become hyper-reactive due to the epileptic process.