Synopsis "Mechanisms of Eye Hand Coordination"
Eye and hand movements can be made independent and in isolation of eachother. Yet, a tight coordination between the eyes and hands are observed, particularly inthose tasks that demand, manipulating objects in external space. For example, whensubjects were asked to do a simple day to day activity of making sandwiches, the eyeswere always found to land on the intended target of the hand before the hand initiates themovement (Johansson et al., 2001; Land and Hayhoe, 2001; Hayhoe et al., 2003; Hayhoeand Ballard, 2005). This tight coupling between eye and hand is a consequence of havinga retina that has maximum visual acuity at the centre or the fovea, where there is amaximum concentration of photoreceptors. To overcome this limitation, the eye israpidly rotated in the orbit, to redirect the high acuity fovea to specific regions in visualperiphery, so that high resolution information can be obtained. The rapid eye movementthat shifts the fovea to the region of interest is called a saccadic eye movement. Toprecisely manipulate a knife, to cut the bread or spread jam on a slice of bread, highacuity visual information regarding the position of these objects are needed. Hence atight coupling between the saccadic eye and hand movements is always seen whensubjects perform such activities. Such a tight coupling between the eye and hand is alsocrucial for the survival of an arboreal primate like a monkey which is swinging from onebranch to the other, so that the eyes are locked to the target of the intended handmovement. Thus eye-hand coordination maybe crucial for survival, hence favored bynatural selection thereby facilitating complex actions in peripersonal space amongprimates, including humans.
