Cortical sources of middle latency responses of auditory evoked magnetic field

doi:10.1016/0378-5955(95)00195-6

Hearing Research

Volume 92, Issues 1–2, December 1995, Pages 47-51

https://doi.org/10.1016/0378-5955(95)00195-6 Get rights and content

Abstract

In the recordings of middle latency responses of auditory evoked magnetic fields in 4 male subjects, we observed distinct components at 11, 19 and 33 ms after click stimulus. Equivalent current dipole sources of these components were located in the supratemporal auditory cortex, where the earliest component source was found at the most medial site.

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Cited by (36)

Phase coherence of auditory steady-state response reflects the amount of cognitive workload in a modified N-back task
2015, Neuroscience Research
Citation Excerpt :
This makes it easy to separate ASSR and EMG. ASSR is known to be evoked most strongly by a 40 Hz auditory stimulus (Galambos et al., 1981; Ross et al., 2000), and the source localizes in the primary auditory cortex (Engelien et al., 2000; Gutschalk et al., 1999; Herdman et al., 2002; Kuriki et al., 1995; Pantev et al., 1996; Weisz et al., 2004). ASSR has been already used in auditory function research in psychiatric disorders and as the evaluation index for testing hearing sensitivity (Picton et al., 2003).
The auditory steady-state response (ASSR) is an oscillatory brain activity evoked by repetitive auditory stimuli. Previous studies have reported that the power and phase locking index (PLI) of ASSR could be modulated by the degree of workload. However, those studies used different physical stimuli for tasks of differing difficulty, and the effect of the internal workload itself has not been clearly understood. In this study, we employed the modified N-back task as a visual working memory task in order to vary the degree of difficulty while keeping the physical stimulus constant. The experiment consisted of four types of tasks: No-Load (NL), 1-back, 2-back, and 3-back tasks. The auditory stimulus was a 40 Hz click sound to induce ASSR. Sixteen healthy subjects participated in the present study and magnetoencephalogram responses were recorded using a 148-channel magnetometer system. The hit rate decreased and the reaction time increased according to the task difficulty. Grand averaged phase coherence activities showed the 40 Hz ASSR reductions accompanying an increase in the task difficulty even with the identical external stimuli. In particular, the phase coherence activities in 3-back task were significantly lower than that in the NL and 1-back tasks. Our results suggest that the ASSR can be a useful indicator for the amount of workload in the brain.
Bioelectric Measurements: Magnetoencephalography
2014, Comprehensive Biomedical Physics
Magnetoencephalography (MEG) records magnetic fields produced by the brain electric activity. Modern devices enable rapid scanning of activity over the whole head. MEG has applications both in basic neuroscience and in the clinical realm. With increasing sophistication of MEG data analysis, studies of evoked responses and brain spontaneous activity have been extended to reveal functional connectivity between brain regions, supporting higher cognitive functions. Clinical MEG applications include the localization of eloquent cortices and epileptic foci in planning brain surgery. In the near future, MEG instruments will have capability for both structural imaging and MEG measurements in the same session.
Steady-state MEG responses elicited by a sequence of amplitude-modulated short tones of different carrier frequencies
2013, Hearing Research
Citation Excerpt :
The latency of ASSR, if converted from 40-Hz repetition rate, corresponds to that of the middle latency response. The middle latency responses measured using MEG consisted of three waves having short rise and fall times of 5–10 ms in a period of about 40 ms after the click stimulation (Kuriki et al., 1995). Dipole sources of those waves were located in the medial site of the auditory cortex.
The auditory steady-state response (ASSR) is a weak potential or magnetic response elicited by periodic acoustic stimuli with a maximum response at about a 40-Hz periodicity. In most previous studies using amplitude-modulated (AM) tones of stimulus sound, long lasting tones of more than 10 s in length were used. However, characteristics of the ASSR elicited by short AM tones have remained unclear. In this study, we examined magnetoencephalographic (MEG) ASSR using a sequence of sinusoidal AM tones of 0.78 s in length with various tone frequencies of 440–990 Hz in about one octave variation. It was found that the amplitude of the ASSR was invariant with tone frequencies when the level of sound pressure was adjusted along an equal-loudness curve. The amplitude also did not depend on the existence of preceding tone or difference in frequency of the preceding tone. When the sound level of AM tones was changed with tone frequencies in the same range of 440–990 Hz, the amplitude of ASSR varied in a proportional manner to the sound level. These characteristics are favorable for the use of ASSR in studying temporal processing of auditory information in the auditory cortex. The lack of adaptation in the ASSR elicited by a sequence of short tones may be ascribed to the neural activity of widely accepted generator of magnetic ASSR in the primary auditory cortex.
Auditory magnetic evoked responses
2013, Handbook of Clinical Neurophysiology
Citation Excerpt :
These two responses in particular are often elusive from the MEG signal. Responses in the cortex have been recorded with MEG as early as 15 ms (Kuriki et al., 1995) and 19 ms (Scherg et al., 1989; Kurike et al., 1995). However, as reviewed by Yvert et al. (2001) and Lütkenhöner et al. (2003a), these early sources are also difficult to record, and the results show variability across participants and studies.
Localization of primary auditory cortex in humans by magnetoencephalography
2003, NeuroImage
Brief auditory stimuli activate the primary auditory cortex (PAC) earlier than any other cortical area so, within a certain latency range, the PAC is the only cortical source contributing to the auditory evoked field (AEF). Nevertheless, there is no AEF component specific to PAC that can be reliably detected in all individuals. The present study suggests that a peak in the first temporal derivative of the magnetic field at about 20 ms (dP20m) is a genuine correlate of PAC activity. AEFs in response to clicks presented to the right ear were recorded with a 37-channel axial gradiometer system positioned over the left hemisphere in nine normal-hearing subjects. More than 8500 stimuli were presented in each of two independent sessions at a rate of approximately 3/s. The dipole coordinates for the dP20m derived from the two sessions typically differed by only a few millimeters. Coregistration of the dipoles with structural magnetic resonance images suggests that dP20m arises from an area close to the retroinsular origin of Heschl's gyrus. Although the dP20m is simply the point of steepest slope on the well-known middle-latency peak, P30m or Pam, it would appear that dP20m and P30m do not have the same cortical origin. Evidence is provided that P30m receives major contributions from at least two distinct cortical areas, only one of which is PAC.
Human auditory middle latency responses: Influence of stimulus type and intensity
2001, Hearing Research
Human auditory middle latency responses (MLR) to click and tone pip stimuli of different intensities were recorded by means of magnetoencephalography (MEG) and electroencephalography (EEG). Clicks elicited larger responses with significantly shorter latencies than the tone pips at the same intensity in dB sensation level (SL). Most MLR amplitudes increased and their latencies decreased with increasing stimulus intensity for both types of stimulation. Pa and Nb amplitudes saturated at intensities of 60 dB SL in the case of click stimulation. The shorter latencies of MLR evoked by the click were explained by its short rise time and the high frequency content of its spectrum. MEG source analysis yielded MLR sources which were clearly different from those of the slow cortical wave N1. They seem to be located in primary auditory areas along Heschl’s gyrus.

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Research paperCortical sources of middle latency responses of auditory evoked magnetic field

Abstract

Electroenceph. Clin. Neurophysiol.

Hear. Res.

Electroenceph. Clin. Neurophysiol.

Neurosci. Lett.

Research paper
Cortical sources of middle latency responses of auditory evoked magnetic field