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Schematic illustration of the memory process involved for the memory of motor skills and cognitive information. SMA: supplementary motor area. See the text for detailed explanation.
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For clinical assessment of motor disturbances, the motor system is better classified into the voluntary versus automatic motor systems than into the pyramidal versus extrapyramidal motor systems. The voluntary motor system is related to externally guided movements initiated by the premotor area while the automatic motor system is related to memory...
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Citations
... Classical textbooks of neurology have written that the sensitivity of stretch receptor increases when extrapyramidal pathway injury, which leads to spasticity paralysis. Further, Kenichi, 2010 showed his opinion that a pure pyramidal tract lesion alone could only induce muscle weakness; hyperreflexia and spasticity appeared when the lesions included reticulospinal tract fibers that belonged to extrapyramidal system. In the previous studies (Yue et al., 2012) of acupuncture treatment of stroke, GB34 had a certain therapeutic effect on limb spasticity. ...
... By contrast, descending projections from other nuclei within the reticular formation are known to modulate muscle tonus and activity 22 and have been associated with increased muscle rigidity when damaged. 23 Theoretically, reticular dysfunction could therefore contribute to both neglect and spasticity. ...
... Little evidence exists regarding the role of the medial-temporal lobe in visual guidance of movements and in visuomotor or motor tasks. The hippocampus has recently been described in the context of memoryguided automatic movements (Uemura, 2010) and is believed to participate in the control of the ventral-striatal loop (or limbic loop), which plays a role in the control of motor behavior (e.g., motor reactions to emotions; Fernández-Seara, Aznárez-Sanado, Mengual, Loayza, & Pastor, 2009;van Rooyen, Young, Larson, & Teskey, 2006;Duvernoy, Vannson, Cattin, & Naidich, 2005;Tesche & Karhu, 1999;Halgren, 1991;Miyashita, Rolls, Cahusac, Niki, & Feigenbaum, 1989). The entorhinal cortex represents self-position in the environment in the form of place cells (Howard & Natu, 2005) and grid cells (McNaughton, Battaglia, Jensen, Moser, & Moser, 2006) and velocity for path integration (i.e., inference of position by integration of velocity; Burak & Fiete, 2009;Blair, Gupta, & Zhang, 2008;Howard, Fotedar, Datey, & Hasselmo, 2005;Lengyel & Erdi, 2004). ...
The division of cortical visual processing into distinct dorsal and ventral streams is a key concept in primate neuroscience [Goodale, M. A., & Milner, A. D. Separate visual pathways for perception and action. Trends in Neurosciences, 15, 20-25, 1992; Steele, G., Weller, R., & Cusick, C. Cortical connections of the caudal subdivision of the dorsolateral area (V4) in monkeys. Journal of Comparative Neurology, 306, 495-520, 1991]. The ventral stream is usually characterized as a "What" pathway, whereas the dorsal stream is implied in mediating spatial perception ("Where") and visually guided actions ("How"). A subpathway emerging from the dorsal stream and projecting to the medial-temporal lobe has been identified [Kravitz, D. J., Saleem, K. S., Baker, C. I., & Mishkin, M. A new neural framework for visuospatial processing. Nature Reviews Neuroscience, 12, 217-230, 2011; Cavada, C., & Goldman-Raiuc, P. S. Posterior parietal cortex in rhesus monkey: I. Parcellation of areas based on distinctive limbic and sensory cortico-cortical connections. Journal of Comparative Neurology, 287, 393-421, 1989]. The current article studies the coordination of visual information typically associated with the dorsal stream ("Where"), with planned movements, focusing on the temporal lobe. We recorded extracellular activity from 565 cells in the human medial-temporal and frontal lobes while 13 patients performed cued hand movements with visual feedback (visuomotor task), without feedback (motor task), or observed visual feedback without motor movement (visual-only task). We discovered two different neural populations in the human medial-temporal lobe. One consists of motor-like neurons representing hand position, speed or acceleration during the motor task but not during the visuomotor or visual tasks. The other is specific to the parahippocampal gyrus (an area known to process visual motion [Gur, M., & Snodderly, D. M. Direction selectivity in V1 of alert monkeys: Evidence for parallel pathways for motion processing. Journal of Physiology, 585, 383-400, 2007; Sato, N., & Nakamura, K. Visual response properties of neurons in the parahippocampal cortex of monkeys. Journal of Neurophysiology, 90, 876-886, 2003]) and encodes speed, acceleration, or direction of hand movements, but only during the visuomotor task: neither during visual-only nor during motor tasks. These findings suggest a functional basis for the anatomical subpathway between the dorsal stream and the medial-temporal lobe. Similar to the recent expansion of the motor control process into the sensory cortex [Matyas, F., Sreenivasan, V., Marbach, F., Wacongne, C., Barsy, B., Mateo, C., et al. Motor control by sensory cortex. Science, 330, 1240-1243, 2010], our findings render the human medial-temporal lobe an important junction in the process of planning and execution of motor acts whether internally or externally (visually) driven. Thus, the medial-temporal lobe might serve as an integration node between the two processing streams. Our findings thus shed new light on the brain mechanisms underlying visuomotor coordination which is a crucial capacity for everyday survival, whether it is identifying and picking up food, sliding a key into a lock, driving a vehicle, or escaping a predator.
To determine whether stroke patients who suffer from hemispatial neglect tend to stay in hospitals longer because they are prone to limb spasticity.
Retrospective analysis of inpatient medical notes.
Inpatient neurorehabilitation unit of a regional UK teaching hospital.
All patients (N=106) admitted to the neurorehabilitation unit between 2008 and 2010 who had suffered a stroke, as confirmed by computed tomography or magnetic resonance imaging.
Not applicable.
Statistical coincidence of hemispatial neglect and spasticity; length of hospital stay.
Chi-square analyses indicated that individuals with left neglect were nearly one third more likely to develop spasticity than those without neglect (87% vs 57%), while nearly one half of those with left-sided spasticity showed neglect (44% vs 13%). Individuals with neglect stayed in the hospital 45 days longer than those without neglect, but the presence or absence of spasticity did not affect length of stay.
The results provide the first statistical evidence, to the best of our knowledge, that neglect and limb spasticity tend to co-occur poststroke, though it is only the former that significantly prolongs stay. Diagnostic value aside, these results are important because they tell us that the treatment of neglect should not be overshadowed by efforts to reduce comorbid spasticity. Despite its poor prognosis, hemispatial neglect continues to receive little targeted therapy in some units.
