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  • 1
    ISSN: 1432-1106
    Keywords: Prehension ; Reach to grasp ; Working memory ; Visual attention ; Visual feedback ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This paper reports two experiments which examined the effects of Parkinson's disease (PD) upon the sensorimotor mechanisms used to control prehension movements. Transport and grasp kinematics for visually-guided and memory-guided prehension movements were examined in healthy control subjects and compared against those of patients with idiopathic PD. Two research questions were addressed: (1) Are patients with PD particularly susceptible to distraction by non-relevant objects? (2) Are patients with PD especially reliant on external feedback when executing goal-directed actions? The results indicated that the patient group were no more susceptible to distraction by non-relevant objects than the control group. In contrast, the patients with PD were shown to be significantly, impaired when executing memory-guided reaches. Furthermore, the deficits exhibited by the PD group on memory-guided reaches were confined solely to those markers associated with the transport component of the prehension movement. That is, while both controls and patients with PD widened their grip aperture on memory-guided trials, the magnitude of this adjustment was comparable across the two groups. The implications of these findings for theories of visuomotor processing in sufferers of PD and the control of prehension movements more generally are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Keywords: Sodium channels ; Acetylcholine receptor channels ; Patch clamping ; Gene expression ; PC12 cells ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract An important component of neuronal differentiation is the tightly controlled expression of a spectrum of ion channel proteins. Ion channels play a critical role in the generation and propagation of action potentials as well as in the cellular response to neurotransmitters, and thus are central in the transfer and integration of information in the nervous system. A model system amenable to analysis of ion channel expression and neuronal differentiation is the rat pheochromocytoma (PC12) cell line. Here, we have used electrophysiological and molecular biological approaches to analyze the expression of voltage-dependent sodium (Na) channels and nicotinic acetylcholine receptors (nAChR) in mutagenized variants (nnr cells) of the PC12 cell line. Our data reveal striking differences in the expression of these channels when compared to wild-type PC12 cells. Even in the absence of nerve growth factor (NGF), nnr cells express functional Na channels and Na channel mRNA at levels exceeding those in wild-type PC12 cells differentiated with NGF. In contrast, acetylcholine-induced currents were evident in only a small proportion of cells, presumably due to the altered pattern of expression of mRNAs encoding individual nAChR subunits. The altered ion channel expression in these variants provides an avenue for analyzing Na channel and nAChR channel function, as well as for identifying mechanisms governing their expression.
    Type of Medium: Electronic Resource
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