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Author | Frenkel-Toledo, S.; Yamanaka, J.; Friedman, J.; Feldman, A.G.; Levin, M.F. | ||||
Title | Referent control of anticipatory grip force during reaching in stroke: an experimental and modeling study | Type | Journal Article | ||
Year | 2019 | Publication | Experimental Brain Research | Abbreviated Journal | Exp Brain Res |
Volume | 237 | Issue | 7 | Pages | 1655-1672 |
Keywords | Anticipatory grip force; Referent control; Stroke | ||||
Abstract | To evaluate normal and impaired control of anticipatory grip force (GF) modulation, we compared GF production during horizontal arm movements in healthy and post-stroke subjects, and, based on a physiologically feasible dynamic model, determined referent control variables underlying the GF-arm motion coordination in each group. 63% of 13 healthy and 48% of 13 stroke subjects produced low sustained initial force (< 10 N) and increased GF prior to arm movement. Movement-related GF increases were higher during fast compared to self-paced arm extension movements only in the healthy group. Differences in the patterns of anticipatory GF increases before the arm movement onset between groups occurred during fast extension arm movement only. In the stroke group, longer delays between the onset of GF change and elbow motion were related to clinical upper limb deficits. Simulations showed that GFs could emerge from the difference between the actual and the referent hand aperture (Ra) specified by the CNS. Similarly, arm movement could result from changes in the referent elbow position (Re) and could be affected by the co-activation (C) command. A subgroup of stroke subjects, who increased GF before arm movement, could specify different patterns of the referent variables while reproducing the healthy typical pattern of GF-arm coordination. Stroke subjects, who increased GF after arm movement onset, also used different referent strategies than controls. Thus, altered anticipatory GF behavior in stroke subjects may be explained by deficits in referent control. | ||||
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Language | English | Summary Language | Original Title | ||
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ISSN | 0014-4819 | ISBN | Medium | ||
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Notes | PMID:30976821 | Approved | no | ||
Call Number | Serial | 98 | |||
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Author | Ezrati, O.; Friedman, J.; Dar, R. | ||||
Title | Attenuation of access to internal states in high obsessive-compulsive individuals might increase susceptibility to false feedback: Evidence from a visuo-motor hand-reaching task | Type | Journal Article | ||
Year | 2019 | Publication | Journal of Behavior Therapy and Experimental Psychiatry | Abbreviated Journal | Journal of Behavior Therapy and Experimental Psychiatry |
Volume | 65 | Issue | Pages | 101445 | |
Keywords | Obsessive-compulsive disorder; Movement; Agency; Proprioception; Proxies | ||||
Abstract | Background and objectives The Seeking Proxies for Internal States (SPIS) model of obsessive-compulsive disorder (OCD) posits that obsessive-compulsive (OC) individuals have attenuated access to their internal states. Hence, they seek and rely on proxies, or discernible substitutes for these internal states. In previous studies, participants with high OC tendencies and OCD patients, compared to controls, showed increased reliance on external proxies and were more influenced by false feedback when judging their internal states. This study is the first to examine the effects of false feedback on performance of hand movements in participants with high and low OC tendencies. Method Thirty-four participants with high OC tendencies and 34 participants with low OC tendencies were asked to perform accurate hand reaches without visual feedback in two separate sessions of a computerized hand-reaching task: once after valid feedback training of their hand location and once with false-rotated feedback. We assessed the accuracy and directional adaptation of participants' reaches. Results As predicted, high OC participants evidenced a larger decrease in their hand positioning accuracy after training with false feedback compared to low OC participants. Limitations The generalization of our findings to OCD requires replication with a clinical sample. Conclusions These results suggest that in addition to self-perceptions, motor performance of OC individuals is prone to be overly influenced by false feedback, possibly due to attenuated access to proprioceptive cues. These findings may be particularly relevant to understanding the distorted sense of agency in OCD. |
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ISSN | 0005-7916 | ISBN | Medium | ||
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Notes | Approved | no | |||
Call Number | Serial | 95 | |||
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Author | Dempsey-Jones, H.; Wesselink, D.B.; Friedman, J.; Makin, T.R. | ||||
Title | Organized Toe Maps in Extreme Foot Users | Type | Journal Article | ||
Year | 2019 | Publication | Cell Reports | Abbreviated Journal | Cell Reports |
Volume | 28 | Issue | 11 | Pages | 2748-2756.e4 |
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Abstract | Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists’ toe representation mimics typical hand representation. We further reveal “hand-like” features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience. | ||||
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Publisher | Elsevier | Place of Publication | Editor | ||
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ISSN | 2211-1247 | ISBN | Medium | ||
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Notes | doi: 10.1016/j.celrep.2019.08.027 | Approved | no | ||
Call Number | Serial | 99 | |||
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Author | Cantergi, D.; Awasthi, B.; Friedman, J. | ||||
Title | Moving objects by imagination? Amount of finger movement and pendulum length determine success in the Chevreul pendulum illusion | Type | Journal Article | ||
Year | 2021 | Publication | Human Movement Science | Abbreviated Journal | Human Movement Science |
Volume | 80 | Issue | Pages | 102879 | |
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ISSN | 0167-9457 | ISBN | Medium | ||
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Notes | Approved | no | |||
Call Number | Serial | 111 | |||
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Author | Bezalel, G.; Nachoum Arad, G.; Plotnik, M.; Friedman, J. | ||||
Title | Voluntary step execution in patients with knee osteoarthritis: Symptomatic vs. non-symptomatic legs | Type | Journal Article | ||
Year | 2021 | Publication | Gait & Posture | Abbreviated Journal | Gait Posture |
Volume | 83 | Issue | Pages | 60-66 | |
Keywords | Accidental falls; Gait; Knee; Osteoarthritis; Voluntary step | ||||
Abstract | BACKGROUND: Individuals with osteoarthritis fall at a greater rate than the general population, likely as a result of weakness, pain, movement limitations, and a decline in balance. Due to the high prevalence of osteoarthritis in the population, understanding the mechanisms leading to greater fall risk is an important issue to better understand. RESEARCH QUESTION: What is the influence of unilateral knee osteoarthritis on the characteristics of performing a voluntary step (i.e., similar to that performed to avoid a fall after a perturbation), compared to healthy age-matched controls? METHODS: Case-control study performed in a Health maintenance organization physical therapy clinic. The research group consisted of a referred sample of 21 patients with unilateral knee osteoarthritis. The control group consisted of 22 age-matched healthy individuals. All participants were over 65 years of age. Participants were excluded if they had a surgical procedure to back or lower limb within one year before testing, oncological or neurological disease or a deficit in tactile sense. Movements were performed with and without dual tasking. MEASUREMENTS: Duration of the initiation phase (cue to step initiation), preparatory phase (step initiation to foot off) and swing phase (foot off to foot contact). RESULTS: In the preparatory phase and swing phase, the osteoarthritis group moved more slowly than the control group, and these differences were larger for forward compared to backward movements. Dual-tasking slowed responses in the pre-movement initiation stage across groups. SIGNIFICANCE: The differences in basic parameters, and the slower movements in the osteoarthritis group, are consistent with known features of osteoarthritis, being a disease commonly regarded as primarily “mechanical”, and are likely to increase fall risk. These response deficits suggest we should take advantage of advanced rehabilitation techniques, including cognitive loading, to help prevent falls in older adults with osteoarthritis. | ||||
Address | Dept. Physical Therapy, Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel. Electronic address: jason@tau.ac.il | ||||
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Language | English | Summary Language | Original Title | ||
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ISSN | 0966-6362 | ISBN | Medium | ||
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Notes | PMID:33080457 | Approved | no | ||
Call Number | Serial | 107 | |||
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