Date Published: March 2, 2018
Publisher: Public Library of Science
Author(s): Andréanne Sharp, Simon P. Landry, Maxime Maheu, François Champoux, Manuel S. Malmierca.
Auditory input plays an important role in the development of body-related processes. The absence of auditory input in deafness is understood to have a significant, and even irreversible, impact on these processes. The ability to map touch on the body is an important element of body-related processing. In this research, the crossed-arm temporal order judgment (TOJ) task was used to evaluate the spatial mapping of touch. This task elicits a conflict between visual and somatosensory body-related information through a change in posture. We used the crossed-arm TOJ task to evaluate the spatial mapping of touch in deaf participants. Results suggested that a change in posture had a greater impact on congenitally deaf participant TOJ than for hearing participants. This provides the first evidence for the role of early auditory exposure on spatial mapping of touch. More importantly, most deaf participants had auditory prosthetics which provided auditory input. This suggests an important, and possibly irreversible, impact of early auditory deprivation on this body-related process.
The representation and control of our body relies on the ability to perceive and distinguish our limbs in space, independent of their posture . This process requires the interaction of somatosensory and retinotopic inputs . Somatosensory inputs provide information on the body’s position in relationship to itself. This sensory information forms the internal frame of reference. Retinotopic input provides information on the body’s position in relationship to the environment. This sensory information forms the external frame of reference. Combining these complementary frames of reference forms a body representation that allows us to interface with our surroundings .
Individual scores for proportion of right-hand first answers across different SOA are shown in Fig 1. We performed an independent t-test between the mean group PCD score for deaf (M = 4.59, SD = 1.91) and hearing group participants (M = 2.49, SD = 1.19). Results from this analysis suggested significant different PCD scores between groups (t(20.146) = -3.373, p = .003). This result indicates that deaf participants had significantly higher TOJ error rates for the crossed posture (see Fig 2). Mean group unspeeded reaction times were analyzed using a repeated measure analysis with two within subject factors (SOA and posture) and the between subject factor group. Results from this analysis failed to reveal a significant between-subjects effect of group for reaction times (F(1,24) = 1.035, p = 0.319, ηp2 = 0.041).
The objective of this study was to investigate spatial mapping of touch in the deaf using the crossed-arm TOJ task. Results for the task revealed that deaf participants had a higher mean PCD group score, indicating more TOJ errors when crossing the arms, compared to hearing control group members. Results from the non-speeded reaction times for the crossed-arm task revealed no difference between groups. These results suggest that a period of deafness permanently alters spatial mapping of touch, but does not alter the time required to provide that judgment.