Use of time differences in normal hearing--cortical processing of promontorial stimuli

TY - JOUR

T1 - Use of time differences in normal hearing--cortical processing of promontorial stimuli

AU - Mortensen, Malene Vejby

AU - Madsen, Stig

AU - Gjedde, Albert

PY - 2005

Y1 - 2005

N2 - To test the hypothesis that ability to discriminate small duration differences is positively correlated with activity in the right temporal lobe, we used positron emission tomography in six normally hearing subjects, stimulated via the promontory in a procedure that mimics the auditory nerve stimulation with a cochlear implant. Stimulus consisted of electrical bursts, and tasks included gap detection and temporal difference limen (TDL). TDL is a measure of discriminatory processing of sound duration in cochlear implant candidates, demonstrated to predict outcome. Good speech perception after cochlear implantation is associated with activity in right temporal areas. Although perceived variably by the subjects, the stimulus itself activated bilateral secondary somatosensory cortex, suggesting differential stimulation of multiple sensory modalities. Only TDL raised blood flow in both posterior middle temporal gyri (MTG) and the right prefrontal cortex. As the right posterior MTG is known to be active during duration discrimination of different modalities and in the perception of words containing manipulated phonemes, we conclude that recruitment of this part of the right hemisphere is important to the comprehension of speech containing mostly temporal cues. The study shows that stimulus-induced activation reflects the goal of the task rather than the nature of the stimulus.

AB - To test the hypothesis that ability to discriminate small duration differences is positively correlated with activity in the right temporal lobe, we used positron emission tomography in six normally hearing subjects, stimulated via the promontory in a procedure that mimics the auditory nerve stimulation with a cochlear implant. Stimulus consisted of electrical bursts, and tasks included gap detection and temporal difference limen (TDL). TDL is a measure of discriminatory processing of sound duration in cochlear implant candidates, demonstrated to predict outcome. Good speech perception after cochlear implantation is associated with activity in right temporal areas. Although perceived variably by the subjects, the stimulus itself activated bilateral secondary somatosensory cortex, suggesting differential stimulation of multiple sensory modalities. Only TDL raised blood flow in both posterior middle temporal gyri (MTG) and the right prefrontal cortex. As the right posterior MTG is known to be active during duration discrimination of different modalities and in the perception of words containing manipulated phonemes, we conclude that recruitment of this part of the right hemisphere is important to the comprehension of speech containing mostly temporal cues. The study shows that stimulus-induced activation reflects the goal of the task rather than the nature of the stimulus.

U2 - 10.1016/j.heares.2005.03.007

DO - 10.1016/j.heares.2005.03.007

M3 - Journal article

C2 - 15953518

SN - 0378-5955

VL - 205

SP - 94

EP - 101

JO - Hearing Research

JF - Hearing Research

IS - 1-2

ER -