New paradigm for auditory paired pulse suppression.

Nobuyuki Takeuchi,Shunsuke Sugiyama,Makoto Nishihara,Kousuke Kanemoto,Koji Inui,Kenji Hashimoto

doi:10.1371/journal.pone.0177747

Abstract

Sensory gating is a mechanism of sensory processing used to prevent an overflow of irrelevant information, with some indexes, such as prepulse inhibition (PPI) and P50 suppression, often utilized for its evaluation. In addition, those are clinically important for diseases such as schizophrenia. In the present study, we investigated long-latency paired-pulse suppression of change-related cortical responses using magnetoencephalography. The test change-related response was evoked by an abrupt increase in sound pressure by 15 dB in a continuous sound composed of a train of 25-ms pure tones at 65 dB. By inserting a leading change stimulus (prepulse), we observed suppression of the test response. In Experiment 1, we examined the effects of conditioning-test intervals (CTI) using a 25-ms pure tone at 80 dB as both the test and prepulse. Our results showed clear suppression of the test response peaking at a CTI of 600 ms, while maximum inhibition was approximately 30%. In Experiment 2, the effects of sound pressure on prepulse were examined by inserting prepulses 600 ms prior to the test stimulus. We found that a paired-pulse suppression greater than 25% was obtained by prepulses larger than 77 dB, i.e., 12 dB louder than the background, suggesting that long latency suppression requires a relatively strong prepulse to obtain adequate suppression, different than short-latency paired-pulse suppression reported in previous studies. In Experiment 3, we confirmed similar levels of suppression using electroencephalography. These results suggested that two identical change stimuli spaced by 600 ms were appropriate for observing the long-latency inhibition. The present method requires only a short inspection time and is non-invasive.

Highlights

When a sensory stimulus is repeatedly presented, responses to it become weak over time, which is generally considered to be caused by inhibitory processes that prevent an overflow of irrelevant information, sometimes referred to as sensory gating
It was reported that positive symptoms of schizophrenia, such as auditory hallucinations [7, 8], and the risk for developing schizophrenia [9] have a relationship to impairment of positivity around 50 ms (P50) suppression
When compared to the test sound (Test) alone condition, post-hoc test results showed that the Test + Prepulse conditions with conditioning-test intervals (CTI) of 600 (p = 0.007), 700 (p = 0.009), and 800 (p = 0.020) ms were significantly smaller in amplitude

Summary

Introduction

When a sensory stimulus is repeatedly presented, responses to it become weak over time, which is generally considered to be caused by inhibitory processes that prevent an overflow of irrelevant information, sometimes referred to as sensory gating. Several methods are utilized to observe such changes in brain responsiveness in humans, including auditory P50 suppression and prepulse inhibition (PPI). It was reported that positive symptoms of schizophrenia, such as auditory hallucinations [7, 8], and the risk for developing schizophrenia [9] have a relationship to impairment of P50 suppression. Other clinical conditions known to be related to impairment of sensory suppression include bipolar disorder [10], panic disorder [11], epilepsy [12], and attention-deficit/hyper-active disorder [13]. P50 suppression deficit has been speculated to be associated with varied cognitive impairments in a wide range of disorders and their symptoms

Methods

Results

Conclusion