The Effects of Monotic and Dichotic Interference Tones on 40 Hz Auditory Steady-State Responses in Normal-Hearing Adults

Auditory steady-state responses (ASSRs) recorded with simultaneous presentation of multiple tones modulated from 77–105 Hz exhibit frequency specificity and can be acquired with monotic or dichotic stimulation. This study examined the frequency specificity and dichotic characteristics of 40 Hz ASSRs recorded with amplitude-modulated (AM) probe tones and unmodulated (UM) or AM interfering tones in 27 normal-hearing adults. The effects on ASSR amplitudes of monotically or dichotically presented interfering tones of various frequency, modulation depth, and modulation rate were studied. Significant decreases in ASSR amplitudes occurred when the UM interfering tone was monotic, higher in frequency, and approximately within an octave of the probe tone. ASSR amplitudes were also reduced when the AM interfering tone was monotic and modulated at a lower depth and was an octave above the probe tone. Probe and interfering AM tones modulated at different rates produced similar reductions in amplitude for ASSRs acquired with monotic and dichotic stimulation. The findings of this study contribute to clarifying the carrier and temporal envelope interactions between tonal stimuli. Description of the effects of these stimulus parameters on 40 Hz ASSRs can benefit clinical applications of this technique, including evaluating auditory function in adults not capable of participating in behavioral audiometric tests. Las respuestas auditivas de estado estable (ASSR) registradas con una presentación simultánea de múltiples tonos modulados desde 77 a 105 Hz, exhiben especificidad frecuencial y puede ser adquiridas con estimulación monótica o dicótica. Este estudio examinó la especificidad frecuencial y las características dicóticas de las ASSR de 40 Hz registradas con sondas de prueba de amplitud modulada (AM) y con tonos de interferencia no modulados (UM), en 27 sujetos adultos normoyentes. Se estudiaron los efectos sobre las amplitudes de las ASSR producto de tonos de interferencia presentados en forma monótica o dicótica, caracterizados por diferentes frecuencias, profundidades de modulación y tasa de modulación. Ocurrieron reducciones significativas en la amplitud de las ASSR cuando el tono de interferencia UM era monótico, de frecuencia mayor, y aproximadamente dentro de una octava del tono de prueba. Las amplitudes de las ASSR también se redujeron cuando el tono de interferencia de AM era monótico y modulado a una profundidad menor y a una octava por encima del tono de prueba. Los tonos de prueba y de interferencia con AM, modulados a diferentes tasas, produjeron reducciones similares en la amplitud de las ASSR, cuando se lograban con estimulación monótica o dicótica. Los hallazgos de este estudio contribuyen a aclarar las interacciones con la envolvente temporal y la del portador, entre estímulos tonales. La descripción de los efectos de estos parámetros del estímulo sobre las ASSR de 40 Hz pueden beneficiar la aplicación clínica de esta técnica, incluyendo la evaluación de funciones auditivas en adultos no capaces de participar en pruebas audiométricas conductuales.

Ipsilateral Auditory Pathway Suppression in Dichotic CV Speech Perception

The exact nature of ipsilateral auditory pathway suppression under dichotic stimulation remains controversial. To help resolve this controversy, the distinctive feature confusions (blend vs nonblend errors) made on a dichotic listening CV test by two hemispherectomees were analyzed. Results support ipsilateral auditory pathway suppression under dichotic CV stimulation. Ipsilateral auditory pathway suppression is discussed in terms of stimulus specificity, subject, and task difference.

Dichotic listening and allusive thinking

SynopsisPrevious work suggests that allusive thinkers have a broader attentional process associated with weak central inhibition. The method of dichotic stimulation was used to investigate this concept. Sixty-three university students completed a battery of tests including 2 dichotic listening tasks. The Object Sorting Test was used as a measure of allusive thinking.Allusive thinkers showed a trend towards impaired shadowing performance. Mislabelling of shadow as distractor words andvice versa, on recall and recognition tasks, showed the strongest correlation with allusive thinking. Such mislabelling was considered to reflect impaired discrimination learning, and provides further support for a hypothesis relating allusive thinking to weak Pavlovian central inhibition.