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|کد مقاله||سال انتشار||تعداد صفحات مقاله انگلیسی||ترجمه فارسی|
|30177||2015||7 صفحه PDF||سفارش دهید|
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Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Schizophrenia Research, Volume 162, Issues 1–3, March 2015, Pages 269–275
Background Well-documented auditory processing deficits such as impaired frequency discrimination and reduced suppression of auditory brain responses in schizophrenia (SZ) may contribute to abnormal auditory functioning in everyday life. Lateral suppression of non-stimulated neurons by stimulated neurons has not been extensively assessed in SZ and likely plays an important role in precise encoding of sounds. Therefore, this study evaluated whether lateral suppression of activity in auditory cortex is impaired in SZ. Methods SZ participants and control participants watched a silent movie with subtitles while listening to trials composed of a 0.5 s control stimulus (CS), a 3 s filtered masking noise (FN), and a 0.5 s test stimulus (TS). The CS and TS were identical on each trial and had energy corresponding to the high energy (recurrent suppression) or low energy (lateral suppression) portions of the FN. Event-related potentials were recorded and suppression was measured as the amplitude change between CS and TS. Results Peak amplitudes of the auditory P2 component (160–260 ms) showed reduced lateral but not recurrent suppression in SZ participants. Conclusions Reduced lateral suppression in SZ participants may lead to overlap of neuronal populations representing different auditory stimuli. Such imprecise neural representations may contribute to the difficulties SZ participants have in discriminating complex stimuli in everyday life.
Individuals with schizophrenia (SZ) have auditory frequency discrimination deficits (Javitt et al., 1997 and Rabinowicz et al., 2000), which are likely to impact real-world auditory functioning. Importantly, auditory deficits in SZ are found not only for frequency discrimination tasks but also for intensity discrimination (Bach et al., 2011) and cue localization tasks (Perrin et al., 2010). Deficits also appear for more complex auditory tasks that require precise encoding of sensory features (Cienfuegos et al., 1999, Leitman et al., 2005, Micoulaud-Franchi et al., 2011, Gold et al., 2012, Ramage et al., 2012, Weintraub et al., 2012, Wu et al., 2012 and Kantrowitz et al., 2013). Similarly, direct brain measurements in SZ show reduced amplitude of auditory cortical responses to various sound properties (Clementz et al., 1997, Michie et al., 2000, Salisbury et al., 2002, Bramon et al., 2004, Jansen et al., 2004, Light and Braff, 2005, Spencer et al., 2008, Hall et al., 2011a and Hall et al., 2011b); reduced gray matter volumes in auditory cortex (Hirayasu et al., 2000 and Kasai et al., 2003); and abnormal microscopic characteristics of auditory cortex (Sweet et al., 2003 and Deng and Huang, 2006). Here, we assess whether reduced effectiveness of lateral suppression should be considered a candidate for explaining some auditory deficits. Lateral suppression is the reduced responsiveness of one set of neurons as a result of the prior activation of neighboring neurons. Likewise, recurrent suppression is the reduced responsiveness of a set of neurons as a result of these same neurons being active recently. Lateral suppression is thought to be a mechanism that leads to smaller populations of neurons being active in response to any given acoustic stimulus ( Chen and Jen, 2000 and Wang et al., 2002) and for a shorter amount of time ( Wehr and Zador, 2003). This is advantageous because the smaller the population and the more abrupt its response, the less overlap there will be with neural populations representing other stimuli, which should support better auditory discrimination. Thus, disruption of lateral suppression could be a candidate mechanism for explaining some of the discrimination deficits observed in SZ as resulting from excessive overlap in neural representations for different sounds. Many previous studies showed less reduction of auditory responses when tones and clicks are repeated in SZ, relatives of those with SZ, and in bipolar disorder (Clementz et al., 1998, Boutros et al., 2004, Olincy and Martin, 2005 and Rojas et al., 2007). However, these prior studies have not separately measured lateral and recurrent suppression because the repeated stimuli have been identical in frequency content. One magnetoencephalography (MEG) study did show that alternation of tones with different frequencies resulted in less suppression of the N1 response in SZ (Rojas et al., 2007), consistent with a lateral suppression deficit. To measure lateral and recurrent suppression in SZ, we recorded event-related brain potentials (ERPs) while presenting stimuli similar to those used in previous MEG studies (Okamoto et al., 2004 and Pantev et al., 2004). The stimuli have energy in alternating frequency bands, which should activate neurons sensitive to those frequencies and suppress activity of neighboring frequencies (for lateral suppression) and the originally stimulated neurons (for recurrent suppression). We predicted that individuals with SZ would show less lateral suppression than healthy controls. Previous studies using this type of paradigm reported lateral and recurrent suppression of the N1 response, an index of auditory sensory memory and pitch processing (Pantev et al., 1989, Lu et al., 1992 and Näätänen and Winkler, 1999) that we expect to show suppression deficits in lateral suppression (cf. Rojas et al., 2007). However, it is also possible that other components such as P2 will show suppression deficits in SZ because prior MEG studies only reported findings for N1, but the P2 is an index of spectral processing and therefore might also reflect frequency-dependent suppression (Shahin et al., 2005, Shahin et al., 2007, Snyder et al., 2006 and Snyder et al., 2009).