Change-related auditory P50: A MEG study
Introduction
The quick detection of abrupt changes in the sensory environment is one of the most important factors for survival. Sensory changes should be detected involuntarily and processed in a specific brain network for this purpose. Previous studies using electroencephalograms (EEG), magnetoencephalograms (MEG), and functional magnetic resonance imaging (fMRI) demonstrated a preattentive brain system sensitive to sudden sensory changes (change-related responses) in the auditory (Akiyama et al., 2011, Inui et al., 2010a, Inui et al., 2010b, Jones, 1991, Nishihara et al., 2011, Ohoyama et al., 2012, Otsuru et al., 2012, Yamashiro et al., 2011), visual (Urakawa et al., 2010), somatosensory (Kodaira et al., 2013, Otsuru et al., 2011), and multisensory (Downar et al., 2000, Tanaka et al., 2009) cortical areas. Change-related responses are considered to be based on sensory memory and comparisons of new sensory events with the preceding status.
Change-N1(m) of auditory evoked potentials (AEPs) or evoked fields (AEFs) is a very clear component peaking at around 100–130 ms after the change onset elicited by any abrupt auditory change (Inui et al., 2010a) and exhibits good test–retest reliability (Inui et al., 2012, Otsuru et al., 2012). The characteristics of Change-N1(m) are as follows. (1) It is elicited by any auditory change including the onset of a sound (Nishihara et al., 2011), offset of a sound (Yamashiro et al., 2009), and changes in sound pressure, frequency, or location (Inui et al., 2010a). (2) The amplitude is affected by the length of the preceding control sound to be compared (Akiyama et al., 2011, Inui et al., 2010a, Yamashiro et al., 2011), or the probability of the control and change sounds (Inui et al., 2010b, Ohoyama et al., 2012). (3) Its amplitude and latency depend on the magnitude of the auditory change (Inui et al., 2010a, Inui et al., 2010b, Nishihara et al., 2011, Yamashiro et al., 2011). (4) It arises in the superior temporal gyrus (STG) and the location does not differ among auditory changes in source estimation studies (Inui et al., 2012, Nishihara et al., 2011, Otsuru et al., 2012, Yamashiro et al., 2009).
However, no detailed studies have been performed on change-related cortical activity before Change-N1(m). AEP studies showed that the earliest component from the auditory cortex appeared as a small vertex-negativity peaking at around 20 ms. This was followed by positive deflections at 30 ms and 50 ms, which have been referred to as the middle-latency responses, P30 (Pa) and P50 (P1). Although P50(m) has been investigated in detail in both basic and clinical studies (for review, see Potter et al., 2006, Ross et al., 2010), parametric studies using middle latency components are generally rare. Furthermore, no study has examined change-related activity at the P50(m) latency in detail. The purpose of this study was to investigate whether change-related components preceded Change-N1m and how, if present, the magnitude of the change affected it using MEG.
Previous studies on change-related auditory responses have used abrupt changes in sound features in a continuous pure tone, and earlier components are typically not detected under these paradigms. Sharp transient stimuli, such as clicks characterized by steep rises in sound energy, have been used to investigate P50(m) and the earlier components (Orekhova et al., 2013, Potter et al., 2006, Ross et al., 2010), therefore, we considered that we would be able to identify early change-related responses clearer using clicks. Hence, we used an abrupt change in a continuous click train to investigate change-related early components in the present study.
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Participants
Twelve healthy volunteers (ten males and two females), aged 23–51 (mean 35.4) years old, participated in this study. This study was approved in advance by the Ethics Committee of the National Institute for Physiological Sciences, Okazaki, Japan, and written consent was obtained from all participants.
MEG recording
The experiment was carried out in a magnetically shielded room. Participants were instructed to watch a silent movie without attending to the sound stimuli. Magnetic signals were recorded using a
Sound location change-evoked magnetic responses
In all participants, the sound onset evoked clear magnetic responses in the bilateral temporal areas (Fig. 2A). The first clear magnetic component elicited by the stimulus onset appeared at around 50 ms (On-P50m, Fig. 2Aa), which was followed by a larger one at around 100 ms (On-N1m, Fig. 2Ab). Similar components were elicited at slightly later latencies for the ITD sounds. The first component peaked at around 60 ms (Fig. 2Ac) and the second one at around 110 ms (Fig. 2Ad) after the onset of the
Discussion
In the present MEG study, we recorded cortical responses to an abrupt auditory change in sound location using clicks, and investigated change-related responses earlier than Change-N1m. The results showed that (1) change-related responses were elicited at around 60 ms (Change-P50m), (2) the amplitude increased and latency shortened with an increase in the sound location change, and (3) source location was estimated in bilateral STG. All these results were consistent with previous findings on
Conclusion
The present study demonstrated that an abrupt change in sound location in a continuous click train elicited change-related cortical responses at around 60 ms following the onset of the change. To support that this P50m response was an endogenous component relating to the change, its amplitude and latency varied according to the degree of the change in a manner similar to Change-N1m. Therefore, the present results suggest that Change-P50m reflects endogenous brain activity driven by environmental
Acknowledgments
This work was supported by JSPS KAKENHI Grant Number 25351001.
References (38)
- et al.
Automatic cortical responses to sound movement: a magnetoencephalography study
Neurosci. Lett.
(2011) - et al.
Magnetic sources of the M50 response are localized to frontal cortex
Clin. Neurophysiol.
(2008) - et al.
Neuromagnetic source localization of auditory evoked fields and intracerebral evoked potentials: a comparison of data in the same patients
Clin. Neurophysiol.
(2001) - et al.
Auditory sensory gating to the human voice: a preliminary MEG study
Psychiatry Res.
(2008) - et al.
Combined mapping of human auditory EEG and MEG responses
Electroencephalogr. Clin. Neurophysiol.
(1998) Memory-dependent auditory evoked potentials to change in the binaural interaction of noise signals
Electroencephalogr. Clin. Neurophysiol.
(1991)- et al.
Sensory gating and source analysis of the auditory P50 in low and high suppressors
NeuroImage
(2009) - et al.
Effects of acute nicotine on somatosensory change-related cortical responses
Neuroscience
(2013) - et al.
Evoked potentials to movement sensation in duplex perception
Clin. Neurophysiol.
(2003) - et al.
The ‘F-complex’ and MMN tap different aspects of deviance
Clin. Neurophysiol.
(2005)