Purchase this article with an account.
C. Gonzalez–Alvarez, A. Subramanian, S. Pardhan; How Does Cognitive Demand Affect Reaching and Grasping Behaviour for Normal and Simulated Visual Impairment . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4593.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Prehensile movements such as reach–to–grasp are affected by reduced visual information1. In addition, studies in our laboratory have shown that the presence of defocus affects both transport and grasp components. In this study, we examined how an additional demanding mental task affects prehensile movements, with normal viewing and in conditions of simulated visual dysfunction. Methodology: Ten young volunteers with normal vision took part. Subjects picked up a cylindrical object under normal viewing conditions and in simulated visual impairment produced by placing blurring lenses (+3.00DS) in front of both eyes. For the cognitive task, subjects performed a mental arithmetic exercise whilst carrying out the motor task. Data were obtained for four different conditions presented randomly: defocus and no defocus measured with and without the cognitive task. A motion analysis system (Vicon 460) recorded and reconstructed the 3D hand and fingers movements. The kinematic indices obtained were Maximum Wrist Velocity, Time to Maximum Velocity, Total Movement Time, Maximum Grip Aperture and Time to Maximum Grip Aperture. Results: In order to assess the influence of the cognitive demand, we compared results between cognition and no cognition for normal and defocus condition. The results show that in normal vision whist carrying out the cognitive task, individuals take longer to reach–to–grasp. The additional mental load also significantly affects the Maximum Grip Aperture (p<0.05). In the presence of blur, time to reach maximum velocity is longer, duration of the movement is longer and maximum grip aperture is smaller when performing a cognitive task at the same time. Conclusions: The data demonstrate that an additional cognitive demand primarily influences the grasp component in normal vision. When visual acuity is reduced the dual task affects both the transport and the grasp components of the reaching and grasping task. This has important clinical implications especially for patients who have newly acquired their visual impairment 1. Sivak et al. Neuropsychologia. 1990; 28:1095–1116
This PDF is available to Subscribers Only