Evaluation of auditory evoked late latency potentials in stuttering individuals

Stuttering is a speech disorder characterized with involuntary stoppages in the stream and rhythm of person?s speech not in compliance with his/her age. It generally starts between ages 3 and 8, and the cause is not certain. Stuttering is classified in three groups being developmental, psychological and neurological. Developmental stuttering its the most common form.Auditory evoked late latency potentials are the initial auditory electrical responses obtained from central nervous system, thalamic and auditory cortical regions. Among late latency potentials, P1 takes its source from secondary auditory cortex, and N1 from lateral supratemporal, frontal lobe in the primary auditory cortex and from midbrain.In our study, with the idea of stuttering may conclude delay auditory feedback, it is aimed to evaluate the cortical response at stuttering and comparison with normal speakers by using auditory late latency potentials.Fifteen male stutterers, who use their right hands and do not have any hearing loss and neurologic problems, and 15 male individuals having normal speech (control group) participated in the study. There was stuttering in the first and second degree relatives of 11 stutterers. Information was obtained from nine stutterers that stuttering started because of fear and psychological trauma, and from one stutterer because of high fever that did not cause neurologic deficit. Five stutterers did not know the starting cause of their stuttering.After the ear-nose-throat examination, immitansmetric examination, distortion product otoacoustic emission and pure tone audiometer tests were realized for the stutterers and for those having normal speech. Late latency records were obtained for those with normal audiological findings. Click stimulus was given from their right ears with TDH-49 earphones and gold electrodes were used. They were determined as vertex (Cz) non-inverting electrode, forehead (Fpz) ground electrode, mastoid (M1) inverting electrode. Silent images from the computer were shown to the subjects during test.As a result of recording the auditory evoked late latency potentials, P1 latency and N1 latency were respectively obtained as 56,68 ± 7,37 msn and 85,09 ± 3,90 msn for stutterers, and as 57,36 ± 7,74 msn and 86,68 ± 5,10 msn for those with normal speech. P1 amplitude and N1 amplitude were respectively found as 0,71 ± 0,53 µV and ?0,63 ± 0,46 µV for stutterers and as 0,73 ± 0,51 µV and ? 0,99 ± 0,76 µV for those with normal speech.A quite weak correlation was detected between stuttering time and N1 wave latency, while no correlation was detected between P1 wave latency. No statistically important difference is observed between the auditory-evoked late latency potentials of stutterers and those with normal speech.Key words: Stuttering, late latency, cortical potentials