We investigated sound detection in humans with magnetoencephalography and behavioural measurements. Sounds with intensity increasing smoothly over 125-1000 ms elicited a transient response in auditory cortex with a peak latency in the 200-600 ms range. Importantly, peak latency accurately predicted behavioural reaction time and was unaffected by attentional engagement. Peak amplitude was augmented when the study participants attended to the stimuli and when stimulus duration was decreased. For investigating the cause of these amplitude variations in the averaged response we designed a wavelet-based method for analysing single-trial responses. We found that attention affects the amplitude of the single-trial responses whereas the intensity slope of the stimulus modifies their latency distribution. The transient response reported here holds promise for rapid, objective hearing assessment not requiring a behavioural task.
"This may imply that early processing of the spectrotemporal structure of an auditory stimulus does not require attentive engagement. Consistent with previous studies (Mäkinen et al., 2004; Tiitinen et al., 2005) the amplitude of the transient brain response was enhanced when the subjects attended to the stimuli. In the young subjects, attentive engagement enhanced the response amplitude to sinusoids notably more than expected based on previous results and when compared to the attention effect in the aged subject group. "
[Show abstract][Hide abstract] ABSTRACT: The aim of the study was to investigate the effects of aging on human cortical auditory processing of rising-intensity sinusoids and speech sounds. We also aimed to evaluate the suitability of a recently discovered transient brain response for applied research.
In young and aged adults, magnetic fields produced by cortical activity elicited by a 570-Hz pure-tone and a speech sound (Finnish vowel /a/) were measured using MEG. The stimuli rose smoothly in intensity from an inaudible to an audible level over 750 ms. We used both the active (attended) and the passive recording condition. In the attended condition, behavioral reaction times were measured.
The latency of the transient brain response was prolonged in the aged compared to the young and the accuracy of behavioral responses to sinusoids was diminished among the aged. In response amplitudes, no differences were found between the young and the aged. In both groups, spectral complexity of the stimuli enhanced response amplitudes.
Aging seems to affect the temporal dynamics of cortical auditory processing. The transient brain response is sensitive both to spectral complexity and aging-related changes in the timing of cortical activation.
The transient brain responses elicited by rising-intensity sounds could be useful in revealing differences in auditory cortical processing in applied research.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 03/2010; 121(6):902-11. DOI:10.1016/j.clinph.2010.01.007 · 3.10 Impact Factor
"The stimulus set comprised a speech stimulus (Finnish vowel /a/; F0 = 113 Hz) and a 570-Hz sinusoid frequency-matched to the strongest harmonic of the vowel spectrum in the vicinity of the first formant (F1). The intensity of the stimuli increased linearly from 0 to 60 dB (SPL) over a duration of 750 ms (see ). The stimuli were presented binaurally, via ear tubes, in separate sequences, using a random interstimulus interval of 1–4 s (N 80 repetitions per stimulus sequence). "
[Show abstract][Hide abstract] ABSTRACT: The effects of aging in the cortical processing of auditory stimuli were studied using whole-head magnetoencephalography (MEG) and long-duration stimuli slowly rising in intensity. The stimuli were 750-ms sinusoids or speech sounds. The two subject groups (N = 9 + 9) studied were, on the average, 61 and 24 years of age. It was found that aging results in considerable delays in averaged transient brain activity.
International Congress Series 06/2007; 1300(1300):85-88. DOI:10.1016/j.ics.2007.01.015
[Show abstract][Hide abstract] ABSTRACT: Magnetoencephalography (MEG) was used to measure brain activity while participants performed a simple reaction to targets after either a random interval (uncued targets) or a series of isochronous warning stimuli with 200-ms intervals that acted as a countdown. Targets could arrive "on time" or "early" relative to the preceding warning stimuli. Cerebellar activity before any stimulus onset predicted uncued simple reaction time. Onset of activity in somatomotor cortex relative to the target predicted reaction time after two warning stimuli when the target arrived on time or early. After three warning stimuli, when the target arrived on time and was certain to occur, prestimulus cerebellar activity and somatomotor onset were significant predictors of reaction time. When the target arrived early after three warning stimuli, prestimulus cerebellar and cingulate activity were predictive. The cerebellar results may reflect a number of possible factors, including a role in timing, response readiness, prediction and attention.
Human Brain Mapping 07/2006; 27(7):552-61. DOI:10.1002/hbm.20200 · 5.97 Impact Factor
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