| Records |
| Author |
Noy, L.; Alon, U.; Friedman, J. |
| Title |
Corrective jitter motion shows similar individual frequencies for the arm and the finger |
Type |
Journal Article |
| Year |
2015 |
Publication |
Experimental Brain Research |
Abbreviated Journal |
Exp Brain Res |
| Volume |
233 |
Issue |
4 |
Pages |
1307-1320 |
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| Abstract |
A characteristic of visuomotor tracking of non-regular oscillating stimuli are high-frequency jittery corrective motions, oscillating around the tracked stimuli. However, the properties of these corrective jitter responses are not well understood. For example, does the jitter response show an idiosyncratic signature? What is the relationship between stimuli properties and jitter properties? Is the jitter response similar across effectors with different inertial properties? To answer these questions, we measured participants' jitter frequencies in two tracking tasks in the arm and the finger. Thirty participants tracked the same set of eleven non-regular oscillating stimuli, vertically moving on a screen, once with forward-backward arm movements (holding a tablet stylus) and once with upward-downward index finger movements (with a motion tracker attached). Participants' jitter frequencies and tracking errors varied systematically as a function of stimuli frequency and amplitude. Additionally, there were clear individual differences in average jitter frequencies between participants, ranging from 0.7 to 1.15 Hz, similar to values reported previously. A comparison of individual jitter frequencies in the two tasks showed a strong correlation between participants' jitter frequencies in the finger and the arm, despite the very different inertial properties of the two effectors. This result suggests that the corrective jitter response stems from common neural processes. |
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0014-4819 |
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| Notes |
PMID:25630905 |
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76 |
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| Author |
Portnoy, S.; Rosenberg, L.; Alazraki, T.; Elyakim, E.; Friedman, J. |
| Title |
Differences in Muscle Activity Patterns and Graphical Product Quality in Children Copying and Tracing Activities on Horizontal or Vertical Surfaces |
Type |
Journal Article |
| Year |
2015 |
Publication |
Journal of Electromyography and Kinesiology |
Abbreviated Journal |
Journal of Electromyography and Kinesiology |
| Volume |
25 |
Issue |
3 |
Pages |
540�547 |
| Keywords |
Motor equivalence; Electromyography; Tablet; Occupational Therapy; Muscle fatigue; Motor control |
| Abstract |
The observation that a given task, e.g. producing a signature, looks similar when created by different motor commands and different muscles groups is known as motor equivalence. Relatively little data exists regarding the characteristics of motor equivalence in children. In this study, we compared the level of performance when performing a tracing task and copying figures in two common postures: while sitting at a desk and while standing in front of a wall, among preschool children. In addition, we compared muscle activity patterns in both postures. Specifically, we compared the movements of 35 five- to six-year old children, recording the same movements of copying figures and path tracing on an electronic tablet in both a horizontal orientation, while sitting, and a vertical orientation, while standing. Different muscle activation patterns were observed between the postures, however no significant difference in the performance level was found, providing evidence of motor equivalence at this young age. The study presents a straightforward method of assessing motor equivalence that can be extended to other stages of development as well as motor disorders. |
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1050-6411 |
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no |
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77 |
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| Author |
Levin, M.F.; Liebermann, D.G.; Parmet, Y.; Berman, S. |
| Title |
Compensatory Versus Noncompensatory Shoulder Movements Used for Reaching in Stroke |
Type |
Journal Article |
| Year |
2015 |
Publication |
Neurorehabilitation and Neural Repair |
Abbreviated Journal |
Neurorehabil Neural Repair |
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Issue |
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Pages |
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| Keywords |
adaptation; arm movement; compensation; kinematics; recovery; rehabilitation |
| Abstract |
BACKGROUND: The extent to which the upper-limb flexor synergy constrains or compensates for arm motor impairment during reaching is controversial. This synergy can be quantified with a minimal marker set describing movements of the arm-plane. OBJECTIVES: To determine whether and how (a) upper-limb flexor synergy in patients with chronic stroke contributes to reaching movements to different arm workspace locations and (b) reaching deficits can be characterized by arm-plane motion. METHODS: Sixteen post-stroke and 8 healthy control subjects made unrestrained reaching movements to targets located in ipsilateral, central, and contralateral arm workspaces. Arm-plane, arm, and trunk motion, and their temporal and spatial linkages were analyzed. RESULTS: Individuals with moderate/severe stroke used greater arm-plane movement and compensatory trunk movement compared to those with mild stroke and control subjects. Arm-plane and trunk movements were more temporally coupled in stroke compared with controls. Reaching accuracy was related to different segment and joint combinations for each target and group: arm-plane movement in controls and mild stroke subjects, and trunk and elbow movements in moderate/severe stroke subjects. Arm-plane movement increased with time since stroke and when combined with trunk rotation, discriminated between different subject groups for reaching the central and contralateral targets. Trunk movement and arm-plane angle during target reaches predicted the subject group. CONCLUSIONS: The upper-limb flexor synergy was used adaptively for reaching accuracy by patients with mild, but not moderate/severe stroke. The flexor synergy, as parameterized by the amount of arm-plane motion, can be used by clinicians to identify levels of motor recovery in patients with stroke. |
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1545-9683 |
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| Notes |
PMID:26510934 |
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no |
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79 |
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| Author |
Awasthi, B.; Williams, M.A.; Friedman, J. |
| Title |
Examining the role of red background in magnocellular contribution to face perception |
Type |
Journal Article |
| Year |
2016 |
Publication |
PeerJ |
Abbreviated Journal |
PeerJ |
| Volume |
4 |
Issue |
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Pages |
e1617 |
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| Abstract |
This study examines the role of the magnocellular system in the early stages of face perception, in particular sex categorization. Utilizing the specific property of magnocellular suppression in red light, we investigated visually guided reaching to low and high spatial frequency hybrid faces against red and grey backgrounds. The arm movement curvature measure shows that reduced response of the magnocellular pathway interferes with the low spatial frequency component of face perception. This finding provides behavioral evidence for magnocellular contribution to non-emotional aspect of face perception. |
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en |
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2167-8359 |
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no |
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81 |
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| Author |
Frenkel-Toledo, S.; Liebermann, D.G.; Bentin, S.; Soroker, N. |
| Title |
Dysfunction of the Human Mirror Neuron System in Ideomotor Apraxia: Evidence from Mu Suppression |
Type |
Journal Article |
| Year |
2016 |
Publication |
Journal of Cognitive Neuroscience |
Abbreviated Journal |
J Cogn Neurosci |
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Issue |
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Pages |
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Stroke patients with ideomotor apraxia (IMA) have difficulties controlling voluntary motor actions, as clearly seen when asked to imitate simple gestures performed by the examiner. Despite extensive research, the neurophysiological mechanisms underlying failure to imitate gestures in IMA remain controversial. The aim of the current study was to explore the relationship between imitation failure in IMA and mirror neuron system (MNS) functioning. Mirror neurons were found to play a crucial role in movement imitation and in imitation-based motor learning. Their recruitment during movement observation and execution is signaled in EEG recording by suppression of the lower (8-10 Hz) mu range. We examined the modulation of EEG in this range in stroke patients with left (n = 21) and right (n = 15) hemisphere damage during observation of video clips showing different manual movements. IMA severity was assessed by the DeRenzi's standardized diagnostic test. Results showed that failure to imitate observed manual movements correlated with diminished mu suppression in patients with damage to the right inferior parietal lobule and in patients with damage to the right inferior frontal gyrus pars opercularis-areas where major components of the human MNS are assumed to reside. Voxel-based lesion symptom mapping revealed a significant impact on imitation capacity for the left inferior and superior parietal lobules and the left post central gyrus. Both left and right hemisphere damages were associated with imitation failure typical of IMA, yet a clear demonstration of relationship to the MNS was obtained only in the right hemisphere damage group. Suppression of the 8-10 Hz range was stronger in central compared with occipital sites, pointing to a dominant implication of mu rather than alpha rhythms. However, the suppression correlated with De Renzi's apraxia test scores not only in central but also in occipital sites, suggesting a multifactorial mechanism for IMA, with a possible impact for deranged visual attention (alpha suppression) beyond the effect of MNS damage (mu suppression). |
| Address |
Loewenstein Hospital, Ra'anana, Israel |
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English |
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0898-929X |
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| Notes |
PMID:26942323 |
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82 |
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