THE REACH AND GRASP MOVEMENTS Essay Example
Hand movements have been the subject of an increasing number of studies over the last one decade. The innovation of a computerized motion analysis in man as well as use of neuropsychological techniques in behaving monkeys, have made it possible to describe the movements of hand during object oriented actions and to identify some of the brain mechanism involved in the control of these movements (Pantes, 2009, 57). Grasping is the motor counterpart of a broader function hence cannot be motor aspects alone. When handling process is taking fore, manipulation for grasping is a prerequisite and at the same time the object identification signals originating from sight are processed. In this sense some authors considered the finger pads as the somatosensory macula.
Studies have shown that during the reach, the finger closes and this process is dependent upon highest point of aperture amplitude, as well as acceleration and velocity of the hand. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters (Weir, 1994, 203).
Some of the motor learning factors in relation to the reach and grasp movement can be categorized as those that are within an individual and factor within the environment. The factors within an individual that affect the motor learning include;cephalocaudal, proximodistal differentiation and integration, each of these factors reverses with age (Sveistrup, 2008, 78).
Given the many research studies that have been done on this topic, this paper examines the factors affecting the reach and grasp activities with special reference to objects like empty glass and glass with water and tennis ball.
When we consider the structure of a motor, the area F5 concentrates on the organization of the hand grasping movements. In order to grasp an object, an individual must be able to control hand and finger movements and precisely shape his/her hand before touching the object. The first process depends, largely on the precentral motor (F1) (Sveistrup, 2008, 81). Lesions or inactivations of this area produce force deficit, flaccidity and, most importantly, a severe
destruction of individual finger movements.
One most important factor affecting the touch and grasp movement is the visual properties of the object. Scientifically an object can only been seen by the human eyes only if the light of reflection from the object hits the human eye causing a recognition of that particular object due to the reflex actions and further prompting the touch and grasp movements respectively (Weir, 1994 109).
A fundamental issue that any model of grasping has to address is the fact that there are several ways of grasping. The selected grip depends on the visual character of object, but also on object functions and the intensions of the agent as regards the object. Let us imagine a glass that is empty, glass containing water and a tennis ball. Once any of the object is recognized as the object, both the empty and the filled glass will be held similarly that is by the body but the force will differ due to weight exerted on the hand from the content of both glasses. For the tennis ball the grasping will be different because of its shape. The fingers will be twisted inwardly in order to accommodate the round shape of the tennis ball. The selection of one of these possible ways of grasping depends on preliminary object recognition and on agent intention, and not exclusively on the visual intrinsic properties of the object (Cazzagon, 2011, 98).
Our views on functions of motor system have been broadened extensively as a result of the ever evolving discoveries. Motor systems is not only limited in translating thoughts and other emotions or sense but it also creates internal actions representation which are useful for a variety of purposes such as generation of action. With the growth of technical know how motor system functions as ceased to be a debated topic but an experimental one.
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