[讨论]听觉处理 auditory processing in human&a

Intensityfficeffice" />

 

Sound intensity has been shown to increase activation volume within the auditory cortex (Bilecen et al., 2002), especially within the primary auditory areas (Hart et al., 2002). Furthermore, there is evidence of the existence of an amplitopic pattern of intensity encoding (Bilecen et al., 2002). The activated areas moved in the dorsomedial direction along the HG with increasing sound pressure level (SPL). This finding is consistent with the results from single-cell recordings from the primary auditory cortex (Heil et al., 1994) and a MEG study by Pantev et al. (1989) showing an amplitopic gradient perpendicular to the tonotopic gradient. Selective attention to sound intensity, activated right STG, right parietal and frontal areas (Belin et al., 1998). Activity in the right temporal cortex was independent of discrimination difficulty, suggesting selective involvement of this area in the sensory aspects of the detection of intensity changes. This observation is consistent with patient data showing that unilateral excision of the right temporal lobe (Milner, 1962) may cause deficits in intensity discrimination. Activity within the right-hemispheric fronto-parietal network, conversely, was modulated by the attentional demands – it was inversely proportional to intensity discriminability. Thus, discrimination of sound intensity involves two different cortical networks: a right fronto-parietal network responsible for allocation of attention, and a region of the associative auditory cortex specifically involved in sensory computation of sound intensity differences (Belin et al., 1998). On the other hand, intensity discrimination ability may be preserved (Engelien et al., 1995) or slightly reduced even after bilateral perisylvian lesions, indicating that intensity coding may to some extent be accomplished by subcortical auditory structures.

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原文由 thinker_jeff 发表于 2005-11-1 23:35:22 :引用：

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原文由 zhixl 发表于 2005-11-1 9:27:15 :2.个体差异,特别是初级听觉皮质的位置个体差异很大,所以参考一些经过加算平均处理后的研究结果时一定要慎重. 自己写report的时候也要尽量避免写出"定位在primary auditory area"的字样,否则会遇到麻烦的.\

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I guess this maybe because each individual had the unique learning history about his (her) native language.fficeffice" /> 

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我想，听觉的初级皮质和语言的学习，是两个完全不同的层次。一个只是在感觉水平，而语言的学习则是在思维水平。

 Individual differences of  auditory area locationfficeffice" />

 

It should be emphasized that the locations of auditory areas are variable in different subject. The anatomical works have shown that the auditory cortex is not organized as a homogeneous area and that the structure of the auditory cortex is highly variable among individuals (Penhune et al., 1996; Westbury et al., 1999). Single-neuron mapping of auditory cortex in laboratory animals, including nonhuman primates, indicates clearly that the location, boundaries, and organization of auditory fields with respect to gyral patterns also vary considerably between subjects (e.g., Merzenich and Brugge, 1973; Merzenich et al., 1975).  Therefore the group analyses with PET and functional magnetic resonance imaging (fMRI), as well as difficulty in the identification of multiple sources with magnetoencephalogram (MEG), may lead to conflicting results of attentional enhancement.

 

  ‘What’ and ’where’ pathwayfficeffice" />

 

Current opinion supports the notion of two major cortical streams, popularly known as ‘what’ and ‘where’ pathways (Rauschecker & Tian 2000). The ‘where’ (dorsal) pathway is thought to link A1 via the caudomedial belt to frontal eye field and parietal targets that are implicated in spatial processing. The‘what’ (ventral) pathway is thought to represent a pattern (or object) information stream that originates in the anterior core and belt areas and influences targets within the temporal lobe. This what/where distinction has gained support not only from animal studies (Rauschecker et al., 1997, Tian et al., 2001) but also more recently in human studies (Alain et al., 2001) .

Despite the attractive simplicity of the dual-streams hypothesis, there is abundant evidence for more complexity. A fundamental concern is that localization and pattern processing are not necessarily independent auditory tasks: spatial information is one of the key factors contributing to the ‘determination’ (or recognition) of sound sources (Yost et al., 1991), and sound localization is greatly in fluenced by the spectral and temporal structure of sounds. Moreover, a growing body of evidence suggests that spatial information is carried in temporal discharge patterns and encoded in the ensemble activity distributed throughout auditory cortex (Mickey et al., 2001).

Recent evidence from human imaging studies (Maeder et al., 2001, Clarke et al., 2002, Bushara et al., 1999, Griffiths et al., 2000, Wise et al., 2001) is generally consistent with the basic dual-pathway hypothesis, but reveals some caveats. On the one hand, evidence shows that the processing of various auditory stimuli that are thought to be representative of ‘what’ tasks (e.g. pitch, working memory, and phonemes) predominantly activate auditory cortex and inferior prefrontal lobe, whereas spatial processing is associated with the activation of posterior temporal areas, parietal cortex and superior frontal sulcus (Alain et al., 2001). On the other hand, the imaging studies offer some fresh insights. For example, Zatorre and coworkers (Zatorre et al., 2002) have shown that the ‘where’ pathway might be involved in tasks such as sensorimotor integration and the disambiguation of overlapping sound sources, and that spatial sensitivity is linked to spectro-temporal features (Zatorre et al., 2001). Alain and co-workers (Alain et al., 2001) reported a significant correlation between the temporal and parietal cortex during pitch and localization tasks, revealing the possibility of considerable cross-talk between the streams.

［此帖子已被 zhixl 在 2005-11-2 13:19:39 编辑过］

听觉‘What’ and ’where’ pathway 是相对比较新的研究结果,这些结论基本在意料之中.视觉的What’ and ’where’ pathway 也基本上是沿着这两条道路线走的.因为异种感觉是要统和的,所以这种分布方式有利于多重感觉的统和(我研究的课题).

视觉和听觉的‘What’ and ’where’ pathway 已经分别被研究得较为清晰了. 但视听觉的空间/时间的统和位置却没有被广泛研究,如果有人对这个课题感兴趣,我们可以探讨

我看的new cognitive neuroscience 中一篇文章认为，what ,where 的说法不准确，根据两方面病人的实验结果，应该是“识别”和“动作”（原文不是这些词，大致这个意思）。当然，你上面也提到了这个意思。

It seems I need to explain more about why I think each individual had the unique learning history about his (her) native language. Here are the points from other people’s research based on my memory only.fficeffice" />

 

1.                  Some research on infants shows that first 3 months of the language environment is the critical period for the baby to discriminate the pronunciations in any language. After this period the ability to discriminate pronunciations has been optimized in the particular language he (she) had listened in those 3 months. At the same time the baby has lost some ability to discriminate the pronunciations in other languages. For example, a Japanese infant has the potential to discriminate any pronunciation in all languages in the first 3 months, however, after those 3 months exposing in Japanese only, the baby will not able to discriminate the sounds “r” and “l” in English.

2.                  This discriminating ability is very likely in Auditory Cortex. That means the early leaning history about language will make difference over Auditory Cortex area.

3.                  The children with native language in English have pretty much the same active cortical area when they’re using English. If a child starts to learn English as a second language before 7 years old, most likely he (she) will end up having same active cortical area when he (she) uses English. But if a child starts to learn English as a second language after 7 years old, he (she) will having a shifted active cortical area when he (she) uses English.

 

There are many studies in this topic if you search in Web.

对前面讨论的东西不清楚，不过上面 thinker_jeff 列的几点大致看过文章或新闻

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原文由 thinker_jeff 发表于 2005-11-2 22:41:02 :

It seems I need to explain more about why I think each individual had the unique learning history about his (her) native language. Here are the points from other people’s research based on my memory only.fficeffice" />

 

1.                  Some research on infants shows that first 3 months of the language environment is the critical period for the baby to discriminate the pronunciations in any language. After this period the ability to discriminate pronunciations has been optimized in the particular language he (she) had listened in those 3 months. At the same time the baby has lost some ability to discriminate the pronunciations in other languages. For example, a Japanese infant has the potential to discriminate any pronunciation in all languages in the first 3 months, however, after those 3 months exposing in Japanese only, the baby will not able to discriminate the sounds “r” and “l” in English.

2.                  This discriminating ability is very likely in Auditory Cortex. That means the early leaning history about language will make difference over Auditory Cortex area.

3.                  The children with native language in English have pretty much the same active cortical area when they’re using English. If a child starts to learn English as a second language before 7 years old, most likely he (she) will end up having same active cortical area when he (she) uses English. But if a child starts to learn English as a second language after 7 years old, he (she) will having a shifted active cortical area when he (she) uses English.

 

There are many studies in this topic if you search in Web.

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thinker_jeff为我们介绍了一个语音处理的研究结果: 婴儿的前3个月是听觉皮质的细胞团对语音的原辅音"处理特异化" 的关键期,3个月之后的婴儿听觉皮质的细胞团只能特异识别母语(前3个月接触的语言)所包含的原辅音.而对母语不包含的原辅音识别比较困难. thinker_jeff同时建议大家在考虑初级听皮质解剖位置(超乎寻常的)个体差异形成原因时,考虑上面介绍的研究结果.

我觉得 thinker_jeff的建议值得重视,因为有些现象支持他的假设:1)猴的初级听皮质也有个体差异,但不如人类那样差异到不可思议的地步,而猴脑是不需要处理语音的.2)虽然大部分的学者都认为人类的初级听皮质主要参与听觉信号的检测任务,但并没有研究显示它"一定"不参与识别任务.

这里我想介绍一个我最近一段时间阅读听觉处理研究论文的心得:很多论文只写auditory cortex而不写是 praimary auditory cortex 还是second auditory cortex. 我分析其中重要原因之一是praimary auditory cortex 的位置还没有被确定,而且个体差异很大,所以作者出于谨慎只写auditory cortex,而不明确写是 praimary auditory cortex 还是second auditory cortex. 所以我现在读论文的时候,如果作者没特殊说明的话,我会将auditory cortex理解成 praimary auditory cortex  + second auditory cortex.

前面的帖子里有没说清楚的地方,这里明确一下:解剖位置个体差异极其恶劣的是praimary auditory cortex  不是second auditory cortex

I think zhixl's interpretation is much more professional than my original one. fficeffice" />