Avaliação de limiar e máximo conforto auditivo por meio de procedimentos operantes com crianças surdas prélinguais submetidas a implante coclear
Resumo
The cochlear implant is a prosthetic electric device that is implanted through surgery. I
has the propose of substituting the cochlear functions allowing thus, the individuals with
pre and post-linguistic neurosensorial deafness to begin to detect environmental sounds.
One of the necessary procedures to help someone to develop hearing skills after the
implant is to trace electrodes, which is a procedure that basically consist of determining
measures of threshold and maximum hearing comfort for each implanted electrode. In
order to obtain these within the clinical practice, the oral skills of the individuals with
implant must be considered. The precision of these measures become very compromised
among implanted children with pre-linguist deafness, due to the deficit of their speech
capacity. The purpose of the present study is to propose an evaluation of two procedures
that attempt to obtain measures of both, hearing threshold and maximum hearing
comfort without using neither, directions or verbal answers. The study consist de two
experiments composed by seven pre-linguist children with profoundly neurosensorial
deafness, which have acquired the Nucleus 24® cochlear implant system . In one of de
procedures, a simple operant discrimination between the presence and absence of de
hearing stimulus was established during the training phase. Following, a testing phase
was introduced in order to determine the hearing threshold to assess the discrimination
loss through a descendant scale, which measures the variation intensity of the electric
stimulus (Experiment 1). In the other procedure, it was established that during the
electric stimulation of the training phase, an answer could stop the stimulus while no
answer produce a positive reinforcement. Next, the intensity of the stimulus was
modified during the test phase in ascendant scales with or without an answer, in order to
determine whether or not the stimulus was comfortable to the subject (Experiment 2). In
both procedures, the electric stimulation was realized through an electrode located in the
cochlear medial region. Electro-physiologic measures of the ECAP and ESR were
evaluated in an additive form within the same date that the operational procedures were
realized. Also, measures of the hearing threshold obtained during clinical approach of
the last evaluation, preceding the beginning of the experiments, were registered. All of
these measures were compared to results obtained from de operant procedures. The
results demonstrated in the Experiment 1, all of the participants learned the taught
discrimination and how to use this skill during the variation of the electric stimulation in
descendant scales. This experiment was also used to indicate hearing threshold
measures with consistence to all of the participants. In the Experiment 2, five of the
seven participants mastered the procedure; however, the results indicate that the order
two participants learned that the answer would interrupt an electric stimulus and its
absence would lead to the reinforcement. Thus, their performance aimed for
identification of the consistence level of the maximum comfort in ascendant scales of
variation. The training phase was not successful with the other participants,
compromising then the consistence of the performance demonstrated during the testing
phase; nonetheless, the measures are suggested for them as well. Concerning the
relationship among the operant measures and the other measures betaken in the study,
the results show that measures of operant threshold are similar to or smaller than the
measures obtained through clinical methods. Regarding the maximum comfort values as
the most relevant data. It has been emphasized that the two participants that fulfilled the
expected performance in the procedure, demonstrated stapedial reflex values (ESR)
similar to the obtained from operant form. The data suggest initial evidence that the
operant procedure can contribute to the realization of tracing electrodes with larger
precision among pre-linguistic children with implants.