Bilateral hearing impaired children assessment of horizontal auditory localization accuracy in a virtual visual environment with free head movement

Twenty-two hearing-impaired children (13 males and 9 females, mean age: 10.45 years, standard deviation 3.13 years) participated in an auditory localization experiment in a virtual visual environment. We investigated the contribution of head movements to localization along the interaural plane in absence of motor constraints and visual cues on a virtual scene, experienced by individuals wearing a head-mounted display while listening to stimuli coming from a circular loudspeaker array. Each session included multiple test conditions. In each condition, the stimulus was presented from loudspeaker positions that were randomly balanced across a sequence of 13 x 5 = 65 trials. Each participant performed the task first with both devices turned on ("On-On"), then with one device (either the left or right one) turned on and one off ("On-Off"), and finally with both devices turned off ("Off-Off"). The On-On condition was presented first during each test session because it provided an everyday listening context participants were accustomed to, and consequently confident with. The third condition was omitted if a patient's pure tone average threshold was above the stimulus level used for the test in the frequency range [0.5-4] kHz. Depending on this threshold, nine Bi HA listeners attended also the Off-Off condition. Two Bi HA listeners were unable to attend the On-Off test condition either, since their session had to be stopped as early as they reported annoyance or fatigue to the experimenter. Children were affected by non-syndromic hearing loss ("GEN NO SDR") in 8 cases (6 GJB2 gene mutations, 2 other gene mutations), syndromic hearing loss ("SDR") in 4 (2 Usher syndromes, 1 chromosomal instability, 1 Waardenburg syndrome), and 1 enlarged vestibular aqueduct (inner ear malformation, "IEM"). Other causes of hearing loss ("Other") were congenital cytomegalovirus infection in 2 cases, chemotherapy with platinum derivatives for neuroblastoma in 2, preterm delivery in 1, and prolonged neonatal intensive care unit stay in 1 case. The cause was not identified ("ND") in 3 cases. All participants were right-handed and had no diagnosis of motor impairment. Reported are: the participant's anonymous id ("Participant"), the age ("Age"), the cause of hearing impairment ("MacroCause"), the years of experience with each device ("Experience DX", "Experience SX"), the left and right pure-tone individual hearing thresholds at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, without and with devices ("Threshold w/o 500 DX" is the right threshold at 500 Hz without devices, and the others are named accordingly), the group ("Group", an example is "Bi CI On-Off" identifying the group of listeners with two cochlear implants, one turned on and the other turned off, and the others are named accordingly), the test condition ("Condition", an example is "NOICSX_ICDX", identifying the listening condition with the left cochlear implant turned off and the right cochlear implant turned on, and the others are named accordingly), the target ("Target", angle in sexagesimal degrees), the signed error ("Signed_error", the difference between the target angle and the pointed angle in sexagesimal degrees), the unsigned error ("Unsigned_error", the absolute difference between the target angle and the pointed angle in sexagesimal degrees), the difference between the target and head orientation angle in the moment when the target was hit ("Head_rotation", in sexagesimal degrees), the head covered distance during a single trial ("Head_distance", in meters).