Ferri Raffaele, Elia Maurizio, Agarwal Nivedita, Lanuzza Bartolo, Musumeci Sebastiano A, Pennisi Giovanni
Department of Neurology, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Via Conte Ruggero 73, 94018 Troina, Italy.
Clin Neurophysiol. 2003 Sep;114(9):1671-80. doi: 10.1016/s1388-2457(03)00153-6.
In order to understand better the psychophysiological basis of auditory processing abnormalities in autism, we decided to study two automatic components of the auditory event-related potentials (ERPs): the mismatch negativity (MMN)--a component of the ERP which is recorded when, during repetitive auditory stimulation, rare changes are introduced--and the novelty-related P3a which is recorded as a response to unexpected novel events occurring in a sequence of repetitive stimuli.
Ten male subjects, mean age 12.3 years (SD 4.95), affected by autism and mental retardation were admitted to this study. All patients were also mentally retarded. Ten normal male subjects, mean age 12.2 years (SD 3.94), were used as controls. Auditory evoked potentials were recorded from 19 scalp electrodes (10-20 system), and stimuli were presented in sequences consisting of 2000 tones (70 dB, ISI=800 ms). Three types of stimuli were presented: (1) standard stimuli (1000 Hz tones, 80% of total stimuli), (2) deviant stimuli (1300 Hz tones, 10% of total stimuli), and (3) novel stimuli (complex and non-monotonal, 10% of total stimuli). To quantify the MMN, the evoked response to the standard tones was subtracted from the corresponding deviant stimulus response and its amplitude and latency at peak were measured over Fz, Cz and Pz; similarly, the P3a component of the ERP was obtained by subtracting the response to the standard tone from that to the novel stimuli and its amplitude and latency at peak were measured over Fz, Cz and Pz. Also, the amplitude and latency at peak for the N1 component of the auditory evoked potential obtained with the standard stimuli were measured over Fz, Cz and Pz. The correlation between age and MMN and P3a amplitude was also analyzed.
N1 showed significantly shorter latencies in the autistic groups. MMN elicited by deviant stimuli, but not that elicited by novel stimuli, was found to be significantly larger in autistic children than in normal controls. P3a showed higher amplitude in autistic subjects than in normal controls during childhood; the opposite was observed during young adulthood.
Our findings indicate that significant changes in ERPs can also be seen in non-cooperative individuals with autism and mental retardation, which might be different from the changes already reported for high-functioning autistic subjects and deserve further insight. These changes show developmental modifications that should be taken into consideration when analyzing data from autistic subjects.
为了更好地理解自闭症患者听觉处理异常的心理生理基础，我们决定研究听觉事件相关电位（ERP）的两个自动成分：失匹配负波（MMN）——ERP的一个成分，在重复性听觉刺激过程中引入罕见变化时可被记录到——以及与新奇性相关的P3a，它是对一系列重复性刺激中出现的意外新奇事件的反应。
10名患有自闭症和智力障碍的男性受试者（平均年龄12.3岁，标准差4.95）被纳入本研究。所有患者均伴有智力障碍。10名正常男性受试者（平均年龄12.2岁，标准差3.94）作为对照。从19个头皮电极（10 - 20系统）记录听觉诱发电位，刺激以由2000个音调（70分贝，刺激间隔=800毫秒）组成的序列呈现。呈现三种类型的刺激：（1）标准刺激（1000赫兹音调，占总刺激的80%），（2）偏差刺激（1300赫兹音调，占总刺激的10%），以及（3）新奇刺激（复杂且非单调，占总刺激的10%）。为了量化MMN，将对标准音调的诱发电位反应从相应的偏差刺激反应中减去，并在Fz、Cz和Pz处测量其峰值的幅度和潜伏期；类似地，通过将对新奇刺激的反应减去对标准音调的反应来获得ERP的P3a成分，并在Fz、Cz和Pz处测量其峰值的幅度和潜伏期。此外，在Fz、Cz和Pz处测量用标准刺激获得的听觉诱发电位N1成分峰值的幅度和潜伏期。还分析了年龄与MMN和P3a幅度之间的相关性。
自闭症组中N1的潜伏期明显更短。发现自闭症儿童中由偏差刺激诱发的MMN显著大于正常对照组，但由新奇刺激诱发的MMN并非如此。在儿童期，自闭症受试者的P3a幅度高于正常对照组；在青年期则观察到相反的情况。
我们的研究结果表明，在患有自闭症和智力障碍的不合作个体中也能观察到ERP的显著变化，这可能与已报道的高功能自闭症受试者的变化不同，值得进一步深入研究。这些变化显示出在分析自闭症受试者数据时应予以考虑的发育性改变。
