Interaction Between Spatial Reference Frame And Spatial Domain In Deaf And Hearing Group

Based on double dissociations in clinical symptoms of patients withunilateral Visuospatial neglect, neuropsychological research distinguishesbetween different spatial domains(near vs. far) and different spatialreference frames(egocentric vs. allocentric). Far (extrapersonal) and near(peripersonal) spaces are behaviorally defined as the space outsidearm-reaching distance and the space within arm-reaching distance.Allocentric reference frame codes object positions relative to anotherobject/background subserving conscious perception of the external worldwhile egocentric reference frame codes object positions relative to theobserver’s body/body parts subserving goal-directed actions towards theobjects. Ventral visual stream was considered in involving processing infar space and representation of allocentric reference frame while Dorsalvisual stream was responsible for processing in near space andrepresentation of egocentric frame. By asking congenitally deafparticipants and hearing controls to perform allocentric and egocentricjudgment tasks on the same stimulus set in near and far space,respectively, and by using the size of the spatial congruency effectbetween allocentric and egocentric positions of the same target object to indicate the extent of influences between the two frames, we aimed toinvestigate whether the two frames and the potential interaction betweenthem in different domain were altered after early deafness.First, the spatial congruency effect was significant both in theallocentric tasks with egocentric positions as irrelevant information and inthe egocentric tasks with allocentric positions as irrelevant information,indicating that the two frames are two interacting rather than dissociablerepresentation systems both in near and far space. Second, in far spaceand near space, deaf participants’ responses were significantly slower inthe egocentric tasks as compared to hearing controls while the two groupsshowed comparable task performance in the allocentric tasks, indicatingthat egocentric reference frame was impaired after early deafness. Third,the pattern of interaction between the two frames was different betweendeaf and hearing groups both in two spatial domain. In far space,irrelevant egocentric positions caused more interference to allocentricprocessing than vice versa in the hearing group while irrelevantallocentric positions caused equivalent interference to egocentricprocessing as vice versa in the deaf group. In near space, irrelevantallocentric positions caused equivalent interference to egocentricprocessing as vice versa both in hearing and deaf group. In addition, inorder to figure out whether deficit of proprioception in deaf influencedthe ability of egocentric, we further set up an open loop task （target-directed task without seeing the pointing hand） to explore thedifferent performance between deaf and hearing group. The resultsshowed that there existed no such factor resulting in the inferiorperformance of deaf group. Implications of the above findings werefurther discussed.