Behavioral analysis of auditory processing
stroke, HL
STROKE
The study analyzed the participants’ central auditory processing using the Dichotic Digit Test (DDT), Frequency Pattern Test (FPT), and electrophysiological assessment (P300).The DDT is a behavioral test of central auditory processing that assesses the perception and understanding of speech sounds related to the acquisition and understanding of language. In addition to the auditory system, the test challenges cognitive functions as it requires attention and memory for execution.The procedures described in the auditory processing evaluation manual were adopted for this application.The FPT is used to assess the auditory electrophysiological potential involved in central auditory processing and is characterized by its ability to determine the location and lateralization as well as the recognition and discrimination of sound characteristics in environments with competitive noise.This test was also conducted in an acoustic booth, using 40 sequences of sounds recorded at 50 dB HL above the tritonal average, at frequencies between 500 and 2000 Hz. Three different acoustic signals were presented in each sequence, of which two sounds were emitted at the same frequency and the third at different frequencies. Each tone was parameterized with duration, interval, and rise and fall times of 200, 150, and 10 ms, respectively. The evaluation took place in two stages, the first instructing the participant to imitate the sound (humming) and the second to characterize the sounds in categories “high-pitched or shrill” or “coarse or deep” (labeling). The answers were converted into a percentage of correct answers, considering ≥75 % as the standard of normality.For the P300, four electrodes were placed: one on the forehead, one on the scalp, and two on the mastoid processes. The impedance was regulated until reaching intensities ≥ 5 Ω, and a difference ≥ 2 Ω between electrodes was accepted. Subsequently, an Electroencephalography (EEG) was performed to record spontaneous brain activity and identify artifacts, followed by an ABR test.After this preliminary stage, P300 was applied using a Contronic® Masbe ATC Plus device, and the participants were instructed to speak or wave their hands whenever they perceived a different sound signal. The binaural test exhibited a sequence of frequent stimuli (tone burst at 1000 Hz), and different and less frequent stimuli presented randomly (tone burst at 2000 Hz). The following criteria were used: 200 µV full scale; 20 ms plateau and rise and fall times of 5 ms; 0.5 Hz high-pass filter; 20 Hz low-pass filter, Notch – SIM; 1000 ms reading window; presentation of 300 stimuli, 20 % of which were rare. The P300 wave latency was marked at the point of maximum amplitude, and all electrophysiological recordings were analyzed by two experienced examiners. The latency data were recorded in milliseconds (ms) and amplitudes in microvolts (µV).In addition to the data obtained from the auditory processing assessment, the following data were collected: stroke classification, age at stroke onset, age at assessment, sex distribution, and the brain region affected.