Environmental Engineering Reference
In-Depth Information
on motor planning. Future studies should examine kinematic findings at a deeper level to
understand the use of vision in both open and closed loop functions. Additionally, since
the treatment of visual contrast information by the CNS changes with time, as discussed
in the next section, new studies must focus on delineating the role of such information for
populations differing by age.
4.2 Aging and luminance contrast
While there are changes at the ocular level with age, the predominant cause of functional
decline is due to a slowing of central processing in the brain (Chaput & Proteau, 1996; Inui,
1997; Light, 1990; Shields et al., 2005). The slowing of temporal processing has been
specifically implicated in the decline of luminance contrast sensitivity in adults over 60.
Motion sensitivity, which is dependent on contrast sensitivity, also declines with age
(Spering et al., 2005; Trick & Silverman, 1991). Motion sensitivity is also known to be directly
linked to function of dopaminergic circuitry, a system known to play a major role in the
aging process (Wild-Wall et al., 2008). Despite these declines, older adults become more
dependent on vision over time, resulting from the relative sparing of visual resources when
compared to other sources of sensory feedback (Adamo et al., 2007; Chaput & Proteau, 1996;
Goble et al., 2008; Lemay et al., 2004). The important concept to note is that this sparing of
neurons in the visual systems results in a greater amount of substrate available for positive
neuroplastic changes relating to motor output. Indeed, such positive changes have been
documented in older adults when trained via the visual system to improve speed of
processing (Ball, Edwards, & Ross, 2007; Edwards et al., 2005; Long & Rourke, 1989; Zhou et
al., 2006). The key question to consider is how might this potential for plastic changes be
manipulated and optimized? Given that the processing of luminance contrast information is
linked in multiple ways with speed of processing, and speed of processing is a central theme
in aging related functional decline, this visual property may be a useful means to answer the
plasticity question. We believe a number of attributes of 3D VEs make them an ideal tool to
aid in investigating this question, and believe design of VEs will directly benefit from the
information gained. Therefore, we intend to investigate changes in sensorimotor processing
of luminance contrast in older adults compared to younger adults. The information gained
from this study will be directly applicable to development of technologies to rehabilitate
and enhance function in aging and neurologically compromised adults.
4.3 Future research aims
Aim 1 is to test the hypothesis that luminance contrasts of target and limb have an effect on
upper extremity kinematics in a virtual environment. This will be investigated using the
methodology described previously with a reach to grasp paradigm. We will test a
population of adults age 18-25 without history of visual or upper extremity sensorimotor
dysfunction. We intend to study five contrast levels ranging from very low to very high.
Based on previous studies of visual feedback, we believe that low levels of luminance
contrast will negatively affect kinematic markers of upper extremity performance, for
example slowed movement time, when compared to moderate and high levels. We also
believe that high levels of contrast will not have a significant effect on performance
measures when compared to the moderate level for this group of participants.
