Skilled motor control

Skilled motor control has been evaluated in tests of manipulative ability, such as a paw reaching for food, in tests of lever pressing, and in simple and choice reaction time tasks in operant test apparatuses. 

Montoya et al., 1990 Abrous et al., 1992). Lesions restricted to the discrete areas of the striatum, suggest that dopaminergic innervation of more lateral areas is likely to be critical for skilled-reaching performance (Sabol et al., 1985 Pisa, 1988 Pisa and Cyr, 1990). 

Analysis of the regional changes in dopamine turnover in rats trained to use just one forelimb for bar pressing indicates significant increases in dopamine turnover bilaterally, in particular in the posterior and the lateral areas of the striatum (Church et al., 1986). In like vein, Cousins and Salamone trained rats on a fixed ratio 5 (FR5) schedule of 

There is, however, a difficulty in interpreting the outcome of these tests of free operant performance, in that it is extremely difficult to distinguish whether the recorded impairments involve an underlying deficit in the motor, sensory or motivational function (Hamilton et al., 1985 Cousins and Salamone, 1996b). Attention has therefore turned to tests in which animals are trained to make rapid movements in response to an imperative stimulus in discrete trial tasks, in which specific changes in signal detection, choice accuracy, reaction time and movement latency can potentially distinguish sensory, motor and motivational components of the deficit. 

The 9-hole box apparatus has been used with different schedules to evaluate the role of the dopamine systems in tests of sustained and divided attention, in which the rats have to detect and respond to brief light stimuli in any one of five open holes (Baunez and Robbins, 1999). Although this experiment was primarily designed to consider the effects of STN lesions, which produce a general disruption of performance in the attentional task (Baunez and Robbins, 1997), 6-OHDA lesions of the dorsal striatum had no effect on accuracy but lengthened latencies of responding correctly and increased the numbers of omissions and perseverative errors (Baunez and Robbins, 1999). 

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Children with autism often experience difficulties with motor control and learning complex motor skills, such as riding a tricyde pumping their l s on a swing or buttoning, zipping, and tying shoe laces. They may do well in academic areas, such as math. 

Neilson, P.D., Neilson, M.D., and O Dwyer, N.J. 1998. Evidence for rapid switching of sensory-motor models. In J. Piek (Ed.), Motor Control and Human Skill A Multidisciplinary Perspective, pp. 105-126. Champaign, IL, Eluman Kinetics. 

The selection set is a presentation of the items from which the user makes choices. The elements in the selection set correspond to the elements of a specific activity output. Selection sets may have written letters, words and sentences, symbols used to represent ideas, computer icons, or line draw-ings/pictures. They may be presented in visual (e.g., letters on keys), tactile (e.g., Braille), or auditory (e.g., voice synthesis) form. We can define two selection methods through which the user makes selections using the control interface direct selection and indirect selection (Cook and Hussey, 2(X)2). For any particular application, the three elements of the human-technology interface will be chosen based on the best match to the consumer s skills (motor, sensory, linguistic, and cognitive) (Cook and Hussey, 2002). 

Information from wel1-control 1 ed animal studies that focus on the effects of prenatal exposure to single and polydrug use will be of great value. Further evaluation of the fine motor movements that appear to be clearly neurological ly deviant in the PCP-exposed infants is essential. The emerging socialization skills during the second year of life also need more detailed evaluations. 

Questions arise when discussing the necessary degree of control of plasma PA levels. While results from a variety of studies vary widely and there is no consensus what the optimal plasma PA level should be, current best evidence suggests that tighter metabolic control (low PA levels) correlates directly with improvements in IQ, motor skills, attention span, behavioral skills, and cognitive ability. In most of these areas, effects of lower PA levels have beneficial effects throughout the life of the patient (NIH Consensus Statement Online, 2000). 

From these various analyses, it is clear that dopamine regulation of the striatum does not simply control detailed movement, but is involved in the selection and initiation of appropriate goal directed actions (Dunnett and Robbins, 1992 Robbins and Everitt, 1992), as influenced by motor learning (i.e. the acquisition of skills and habits Mishkin et al., 1984 Jog et al., 1999), in the context of motivational information related to needs and rewards (Suri and Schultz, 1999). Theoretical formulations of this process have moved away from the neuropsychological theory, although still conceptually useful, to mathematical and neural network modeling (Houk et al., 1995 Servan-Schreiber et al., 1998), which is beyond the scope of the present review. 

A second report from the Maternal Lifestyle Study focused on motor development in 392 children prenatally exposed to cocaine and 776 non-exposed control infants who were identified by meconium assay and mothers self-reporting (327). Motor skills were assessed at 1 month with the NICU Network Neurobehavioral Scale (NNNS), at 4 months with the posture and fine motor assessment of infants (PFMAI), at 12 months with the Bayley Scales of Infant Development-2nd edition (BSID-II), and at 18 months with the Peabody Developmental Motor Scales (PDMS). The infants with prenatal cocaine exposure had motor skill deficits at 1 month, but normal function at 18 months. Heavy cocaine use was associated with poorer motor performance. Both lower and higher nicotine exposures related to poorer motor performance. 

In nine prospective, longitudinal, multicenter studies, 1227 infants who were exposed in utero to cocaine (n = 474), opiates (n = 50), cocaine + opiates (n = 48), or neither (n = 655) were followed for 1-3 years after birth. Prenatal exposure to cocaine and/or opiates was not associated with mental, motor, or behavioral defects after controlling for birth weight and environmental risks. This result should be treated with caution, since the effects of prenatal opiates or cocaine exposure may become more evident as more advanced motor, cognitive, language, and behavioral skills develop (57). 

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