The Reach and Grasp Movements
Name of Institution:
Hand movements have been the subject of an increasing number of studies over the last one decade with numerous research depicting that some of the major factors that affect motor learning in relation to reach and grasp movement being cognitive processes, movement organization and the environment. 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.
The effect of environment can be explained thus; According to (Pantes, 2009) reach and grasp movements requires the hand to be transported to an object of interest whilst the fingers are pre-shaped to match the dimension of the target object. These two components are closely attached in space and time with alterations to one component causing changes in the other. Studies have explored the manner in which the nervous system controls these components of hand movement when reaching to grasp an isolated object within the work space.
According to (Sveistrup, 2008), in the last one decade, cognitive science has greatly helped in showing interest in understanding the relation between the functional processes necessary to initiate a goal-directed action and the processes essential for perception and thought. For instance, correlation effects existing between motor response and object discernment is two directional. That is, possible actions can be effected by stimuli and characteristics of a set action can manipulate the perception of stimulus features (Fagioli & Schubotz, 2007).
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).
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).
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 motives of the agent. 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 the learning factors of motor system have been broadened extensively as a result of the ever evolving discoveries and with the growth of technical know how motor system functions as ceased to be a debated topic but an experimental one
- Sveistrup, H. (2008). Head, arm and trunk coordination during reaching in children: Experimental Brain Research. New York: Longman Groups Limited.
- Ng, Tommy H. B. (2010). Premovement brain activity in a bimanual load-lifting task: Experimental Brain Research. New York and London: Routledge
- Ashford, Derek. (2007). Developmental effects influencing observational modelling: A meta-analysis. Journal of Sports Sciences 25(5)
- Pantes, G. (2009). Memory pointing in children and adults: dissociations in the maturation of spatial and temporal movement parameters. Experimental Brain Research 76, 56-70
- Bruce, C., Desimone, R., & Gross, C.G. (1981). Visual properties of neurons in a polysensory area in superior temporal sulcus of themacaque. J. Neurophysiol. 46, 369–384
- Friedemann, M., & Johannes, D.(1994). Neuropsychologia, 32 2 265-269
- Randall, J. F., & Roland, S. J. (2003). Encyclopedia of the Human Brain (Vol. 30 pp. 399-414) Chicago, IL: Encyclopedia Britannica.
- Weir, P. L. (1994). Object Property and Task Effects on Prehension: In Insights into the Reach to Grasp Movement. Amsterdam: Elsevier.
- Cazzagon, M. (2011). A protocol for the assessment of sensory re-weighting in the development of coordination during reach-to-grasp in children: Gait & Posture. New York, NY: McGraw-Hill
- Pantes, G. (2009). Memory pointing in children and adults: dissociations in the maturation of spatial and temporal movement parameters: Experimental Brain Research New York: Prentice Hall.