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Why Study Movement Variability in Autism?
Published in Elizabeth B. Torres, Caroline Whyatt, Autism, 2017
Maria Brincker, Elizabeth B. Torres
Following the hypothesis of Von Holst and Mittelstaedt, there might be some sort of internal signal—perhaps an efference copy—that allows a system to sort its overall afferent input into reafference and ex-afference, respectively. However, as we have underscored earlier, the actual efference, in the sense of the actual peripheral movement, is a rather complex and layered affair. In other words, the efference copy or, more broadly, embodied expectation had better be layered and complex as well, to be able to tease apart and decompose the signals of the returning afferent barrage. The simplistic picture of one isolated afference quantity minus one isolated efference quantity is simply not going to cut it even if we limit our consideration to one sensory modality or even one receptor channel in isolation.
Sensory Development and Motor Control in Infants and Children
Published in Mark De Ste Croix, Thomas Korff, Paediatric Biomechanics and Motor Control, 2013
In addition to afferent feedback, evidence has been provided for another feedback loop called efference copy, which is a replica of the original motor commands. This provides a reference for the afferent sensory information and provides a solution to the problem of determining whether errors are caused by changes in the environment or internally such as changes in body movement (Gandevia 1996).
Sensory and Motor Functions of Face Primary Somatosensory Cortex in The Primate
Published in Mark J Rowe, Yoshiaki Iwamura, Somatosensory Processing: From Single Neuron to Brain Imaging, 2001
Gregory M. Murray, Li-Deh Lin, Dongyuan Yao, Barry J. Sessle
Our data are compatible with the view that the motor centres can adjust the gain of transmitting elements in the somatosensory afferent pathways to compensate for the increased sensory input produced during or as a result of the movement (Chapin, 1987; MacKay and Crammond, 1989; Chapman, 1994). Our findings are also not inconsistent with the theory of corollary discharge or efference copy that is thought to modulate the transmission of sensory information and thus perception (see above); this modified sensory information also may be used by other motor centres in the control of movement. Many of the face SI neurones that we recorded likely had connections to orofacial sensorimotor centres, such as face MI and brainstem sensory and motor nuclei, e.g. there is both electrophysiological and anatomical evidence of direct projections from primate face SI to the brainstem (Darian-Smith, 1973; Dubner et al., 1978; Kuypers, 1981; Sirisko and Sessle, 1983; Bushnell et al., 1987). Thus, some of these corticofugal projection neurones might be concerned with the subcortical modulation of somatosensory responses during movements and may explain our findings of somatotopically organised and movement specific modulation of the low threshold somatosensory responses of face SI neurones during tongue protrusion and jaw movements. These corticofugal activities may modulate the somatosensory responses in such a way as to adjust the gain of somatosensory inputs evoked during the movements or generated by the movements, and thus maintain the sensorimotor system’s sensitivity to externally applied disturbances.
A Story of Discovery and Change: What We Learned from Studying Nystagmus in Infancy and Childhood
Published in Journal of Binocular Vision and Ocular Motility, 2022
Children with an eccentric gaze null position can present with a constant or intermittent head turn, used to maintain the eyes in the position of minimum nystagmus relative to the brainstem or orbit. This is particularly prominent when the child is concentrating on a distant object since INS intensity increases with attempted fixation. Head oscillations are common in INS but are not used as the strategy to improve vision. Head oscillations in most patients with INS probably reflect the same abnormal motor signal sent to eyes to the cervical muscles. I have labeled this phenomenon “neckstagmus.” Oscillopsia is not continuously present in patients with INS, but about 20% will report episodic oscillopsia under various levels of consciousness, environmental lighting conditions, medications, and body positioning. The reason for this is the unique ability of the developing visual system to create efference copy adaptation mechanisms. The absence of oscillopsia in visually mature patients is usually helpful in distinguishing neurologically significant from neurologically insignificant forms of nystagmus. Even patients with neurologically significant forms of nystagmus can develop suppression of oscillopsia if the nystagmus is longstanding and the onset is in the first decade of life.24
Joint Position Accuracy Is Influenced by Visuoproprioceptive Congruency in Virtual Reality
Published in Journal of Motor Behavior, 2022
Kate A. Spitzley, Andrew R. Karduna
Note that with only four trials per condition, the interpretation of VE results should be taken with caution. No differences in VE were seen between target angles or visual conditions (Figure 4a). The consistency between conditions in combination with the low averages across conditions indicates high task reliability among participants. Had participants been guessing at the target angles, much higher variable error would be expected. This is in agreement with previous repositioning studies investigating vision and proprioception (van Beers et al., 1996) and further supports the choice of 8° as an unnoticeable offset, assuming that a noticeable perturbation would decrease participant reliability. However, some increase in VE in the OV condition was expected as visuoproprioceptive mismatches introduce noise into the system. Previous studies have seen that both alterations in a sensory signal and issues during integration of sensory signals can lead to large changes in movement outcomes (Berkinblit et al., 1995; Cruse et al., 1990; Darling & Miller, 1993; Soechting & Flanders, 1989). This being the case, one of the following likely occurred in the present study: participants (a) completed the task by relying on feedforward information from motor planning and efference copy mechanisms, (b) did not interpret the visual offset as an error, or (c) interpreted the visual offset as an error and changed how they relied on sensory information to accommodate.
Joint-Position Sense Accuracy Is Equally Affected by Vision among Children with and without Cerebral Palsy
Published in Journal of Motor Behavior, 2021
Flávia de Andrade e Souza Mazuchi, Luis Mochizuki, Joseph Hamill, Patricia Martins Franciulli, Aline Bigongiari, Isabella Tábata de Almeida Martins, Ulysses Fernandes Ervilha
Without visual feedback, proprioception information plays an important role to someone to hit a target. Along the task, the groups equally applied the ongoing correction of movement using reafference because the children with normal development were as precise as the children with cerebral palsy. Reafference assists the motor control to reduce discrepancy between the planned movement (and efferent copy) and real position of the target. Analysis of position sense in children with spastic diplegic cerebral palsy allows understanding how the afferent-efferent flow information system is damaged (Craje et al., 2009). Those children might show difficulties to cope with motor tasks. Besides, they can use visual information just like children without cerebral palsy to correct the final position of a motor task.