Reduced Auditory Processing Capacity during Vocalization in Children with Selective Mutism Miri Arie, Yael Henkin, Dominique Lamy, Simona Tetin-Schneider, Alan Apter, Avi Sadeh, and Yair Bar-Haim Background: Because abnormal Auditory Efferent Activity (AEA) is associated with auditory distortions during vocalization, we tested whether auditory processing is impaired during vocalization in children with Selective Mutism (SM). Methods: Participants were children with SM and abnormal AEA, children with SM and normal AEA, and normally speaking controls, who had to detect aurally presented target words embedded within word lists under two conditions: silence (single task), and while vocalizing (dual task). To ascertain specificity of auditory-vocal deficit, effects of concurrent vocalizing were also examined during a visual task. Results: Children with SM and abnormal AEA showed impaired auditory processing during vocalization relative to children with SM and normal AEA, and relative to control children. This impairment is specific to the auditory modality and does not reflect difficulties in dual task per se. Conclusions: The data extends previous findings suggesting that deficient auditory processing is involved in speech selectivity in SM. Key Words: Auditory Processing, elective mutism, selective mut- ism, social anxiety, social phobia, vocalization S elective Mutism (SM) is a psychiatric disorder of childhood characterized by consistent failure to speak in specific social situations (where speaking is expected) despite ability to speak normally in other situations (DSM-IV-TR). Based on the literature describing the connections between vocaliza- tion and hearing, and on review of the neural substrates sup- porting these connections, Bar-Haim et al (2004) suggested that deficient auditory processing during vocalization might impair the ability of some children with SM to simultaneously speak and process incoming auditory signals. To preserve auditory sensitivity to external signals during stimulation by one’s own voice, negative feedback circuits are activated (Hoy 2002). In humans, activity of the middle-ear acoustic reflex (MEAR) during vocalization results in decreasing the masking influence of the speaker’s own voice, thereby improving the speaking person’s ability to hear external sounds while vocalizing (Borg et al 1984; Borg and Zakrisson 1973; Borg and Zakrisson 1975). Additionally, efferent activity of the medial olivocochlear bundle has been implicated in the improvement of signal-to-noise ratio and speech intelligibility in noise (Dewson 1968; Giraud et al 1997; Micheyl and Collet 1996), and thus has an important role in preventing desensitization of the auditory system during vocalization. Bar-Haim et al (2004) reported that, compared with speaking control children, children with SM displayed significant aberrations in MEAR thresholds and decay functions, and diminished suppression effect of transient oto- acoustic emissions (TEOAE), indexing reduced activity of effer- ents from the olivocochlear bundle. The objective of the present study was to test whether auditory processing is indeed impaired during vocalization in children with SM who display abnormal auditory efferent activity (AEA), with a new sample of children. Specifically, while all children were expected to show poorer performance in a task requiring both auditory processing and vocalizing (dual task) relative to a task requiring auditory processing alone (single task), we expected that relative to children with SM who have normal AEA, and relative to normally speaking controls, children with SM and abnormal AEA would show a greater dual-task performance cost. Furthermore, we expected these results to be specific to auditory-vocal performance, and not to occur on a visual-vocal task. Methods and Materials Participants Participants were 28 children recruited into three study groups: 9 children with SM and abnormal AEA; 9 children with SM and normal AEA; and 10 speaking control children. Table 1 summarizes children’s characterization data by group. For com- plete description of the referral process, diagnostic procedures, inclusion criteria, and questionnaires used in the study, see Supplement 1. Audiologic Assessment Children who met the study’s psychiatric inclusion criteria were invited for audiologic assessments. Children with normal air-conduction thresholds (i.e., pure-tone average of 0.5, 1, and 2 kHz  15dBHL), normal tympanograms, and normal auditory brainstem response (ABR) were further tested for AEA function. The assessment of AEA function included testing of ipsi- and contra-lateral MEAR pure-tone thresholds at 0.5, 1, and 2 kHz, ipsi- and contra-lateral reflex decay to 0.5 and 1 kHz pure tones, and TEOAE suppression effect in both ears. For detailed description of audiologic procedures and criteria for auditory efferent deficiency, see Bar-Haim et al (2004) and Supplement 1. Assessment of Auditory Monitoring Performance During Vocalization All children were trained to vocalize (counting 1 to 10 repeatedly) until preset criteria of fluency (breaks of silence not From the Adler Center for Research in Child Development and Psychopa- thology, Department of Psychology (MA, DL, AS, YB), Tel Aviv University; Department of Communication Disorders (YH, STC), Sackler Faculty of Medicine, Tel Aviv University; the Speech and Hearing Center (YH, STC), The Chaim Sheba Medical Center; Department of Psychiatry (AA), Sack- ler Faculty of Medicine, Tel Aviv University; the Feinberg Child Study Center (AA), Schneider’s Children’s medical Center of Israel. Address reprint requests to Yair Bar-Haim, Ph.D., The Adler Center for Re- search in Child Development and Psychopathology, Department of Psy- chology, Tel-Aviv University, Ramat Aviv, Tel-Aviv 69978, Israel; E-mail: yair1@post.tau.ac.il. Received August 10, 2005; revised February 8, 2006; accepted February 10, 2006. BIOL PSYCHIATRY 2007;61:419 – 421 0006-3223/07/$32.00 doi:10.1016/j.biopsych.2006.02.020 © 2007 Society of Biological Psychiatry