2009年11月5日,星期四

为什么"哪里" cannot be a 感官 processing 流

There is debate about the nature of the dorsal 听觉 processing 流. Some folks, Josef Rauschecker in particular, argue for a dorsal "哪里" 流, 哪里as others, Hickok & Poeppel and Warren et al., argue for a 感官-motor integration (sometimes called "how") 流. Here's why the "哪里" hypothesis can't, in principle, be right.

Spatial information associated with an 听觉 signal is a stimulus 特征 much like pitch. We don't talk about a "pitch 流" however. 为什么not? Because pitch (frequency) is just a cue for any number of processing goals. Pitch information can cue phonemic identity, speaker voice, 听觉 流 segregation ... even 感官-motor goals (humming back a tone). Spatial cues are no different in that they can cue explicit location judgments, 听觉 流 segregation, and any number of 感官-motor processes (head movements, saccades, locomotion toward or away from a source).

Processing 流s, I'm suggesting, are defined by goals or tasks -- 什么 the information is used for -- not by stimulus 特征s. Sensory-motor integration for vocal tract actions defines a goal -- control of the vocal tract -- and therefore is a viable candidate for a processing 流. Identifying the meaning of an 听觉 object is also a goal and a good candidate for a processing 流. Stimulus 特征s, like pitch or location are not goals, they are just cues that can be used within various task-driven processing 流s.

Of course, this doesn't imply that there isn't a specialized location processing system in the brain that uses interaural time and level differences to compute 空间的 information. Almost for sure there is (my guess is that it's subcortical), just like there is a system that processes pitch using frequency information. But we shouldn't confuse a specialized 特征 processing system (area) with a cortical processing 流 as the notion "流" is typically used.

Which reminds me. It is probably time to redefine the notion of a processing "流"。一世n particular, I think the dorsal-ventral distinction is getting tired and has now outlived its usefulness. I'll expand in a later post...

参考文献

Hickok,G.和Poeppel,D.(2000)。迈向语音感知的功能神经解剖学 认知科学趋势,4 (4),131-138 DOI: 10.1016 / S1364-6613(00)01463-7

Hickok,G.和Poeppel,D.(2007年)。语音处理的皮质组织 自然评论神经科学,8 (5),393-402 DOI: 10.1038 / nrn2113

Rauschecker JP, & Scott SK (2009). Maps and 流s in the 听觉 cortex: nonhuman primates illuminate human speech processing. 自然神经科学,12 (6),718-24 PMID: 19471271

Warren JE, Wise RJ, & Warren JD (2005). Sounds do-able: 听觉-motor transformations and the posterior temporal plane. 神经科学趋势,28 (12),636-43 PMID: 16216346

6条评论:

凯文·H said...

为什么不't determing 哪里 a sound is coming from be a viable goal? While some aspects of location are certainly easily handled by the brainstem, so are some aspects of object identification. Determing 哪里 and object is in space is much more of a issue than simple ITD/ILD. There is almost certainly some input from AM sensitives cells to detect 听觉 motion, large 视觉的 input, and heavy interaction with 空间的 在 tention. None of which can be adequately handled subcortically.

我不't really doubt your findings for spt, but it is a bridge too far to extrapolate those findings to everything 听觉 related dorsal of HG.

格雷格希科克说过...

凯文,你好

您提出了一些好的观点。在回答之前,让我问您一个问题:您为什么不为自己辩护"pitch 流"? Isn't 决定 什么 pitch a sound is a viable goal?

凯文·H said...

音高当然是'what'。我想这全都归结为您想要变得多么简约。每个神经组合都有它'自己的独特角色,因此将有一个特定组的单元最好地完成任务,但是我们不'不能全给他们自己'stream'。对于具有相似或重叠目标的许多不同组合,Stream只是一个有用的速记。

我认为您当然可以将流的一般有用的想法变成没有用的教条。例如,以AM。 AM在确定您听到的内容以及确定在哪里/将要出现的位置方面都很重要。一种愚蠢的教条式方法会说您必须有两个单独的AM处理区域,其中一个专门用于'what'处理,这就是全部'where'。对流的更加务实的设想是这些过程在某种程度上都是重叠且复杂的,并且大脑将尝试以尽可能高效的系统来解决所有问题,'完全适合我们想要的盒子。

In that same sense, I can certainly see 感官-motor areas fitting in quite nicely. Obviously, ever part of the processing 流 needs to get back to a motor system eventually, and some systems will need to make that leap sooner rather than later. There are a number of reason that this 感官-motor system might be biased to be caudal of HG. Being closer to motor cortex improves reaction times slightly, and it's的运动功能可能会与其他运动功能重叠,例如将声音定向与附近区域发生的空间处理有很大关系。

所以,我想我'm试图得出这样的结论:如果有人试图告诉您某个给定的区域可以'T具有特定的功能,因为该一般区域中的所有内容都专门用于特定的'stream' they are obviously wrong. But, I think your playing into their game if you simply try to redefine the 流. Whatever your definition is, there will be countless outliers. I'd much rather look 在 流s as a general organizing principle that probably has a lot more to do with anatomical efficiency than serial information flow.

As to 什么 什么 to label this nebulous, imperfect 'stream'. I'd say that it still looks like a bunch of caudal 听觉 cortex is primarily devoted to 空间的 tasks, so I'd still plan on calling it a 空间的 流.

格雷格希科克说过...

我认为您在谈论“教义”概念的教条化应用时,正处于正确的轨道上"stream", but you went foul when you stuck to the 空间的 流 dogma. :-)

音调:您说音调肯定是'what'. But this is not always true. I can play you a sequence of pitches and you can use that 感官 information to guide your own vocal tract actions to reproduce that sequence via humming. This is a 感官-motor task and therefore part of the "dorsal 流"(此任务还可以很好地激活Spt)。"Pitch processing"因为没有音高处理的目标,所以它不是流。这取决于任务。同样的"spatial processing", 什么 流 it enters into depends completely on the task.

声道的感觉运动整合'因为声道控制不是声学功能,所以这是一个目标,因此会遭受这个问题。访问语义表示也是一个目标,而不是声学特征。这些是"streams".

可以这样想:在一个层次上,您有一个感觉系统,可以将感觉输入分析成各种信息(间距,位置等)。然后,该感觉系统与大脑的其余部分进行交互以完成任务。感觉系统与大脑其余部分系统的“交互作用”是定义流的要素,对于给定任务有用的任何感觉信息都将进入该流。用这种思维方式,流实际上并不是感觉系统的一部分(即"auditory" or "visual"流是真空的),它们是感觉系统与其他神经系统相互作用的方式。

现在,在您的第一条评论中,您说:"wouldn't 决定 哪里 a sound is coming from be a viable goal?" Sure. But "determining" for 什么 purpose? To control an orienting response? (Dorsal 感官-motor 流.) To separate out one sound source from another? (Ventral 流?) To make decision as to whether the location of that sound source is the same as a previously presented sound source? (Who knows 什么 frontal problem solving 流.) You get the point.

Also, in your first comment you suggested I was extrapolating Spt to be THE DORSAL STREAM. Although it may sound like this from 什么 I write, 我不't actually believe it. I think Spt is just the interface between the 听觉 system and the vocal tract motor system. I think there are other interfaces with say head movement or ocular control systems, and musicians probably have a very nice 听觉-manual control system. I.e., lot's of 感官-motor "dorsal 流s" exist (note I said 'sensory' not 听觉-motor because any relevant 感官 information can enter the 流).

Finally, you say that a bunch of caudal 听觉 cortex is primarily devoted to 空间的 tasks. I'我一点也不相信这是真的。实际没有人操纵任务来查看是否"spatial"激活动作。但是,我们要做的一件事是表明非空间操作(添加多个声源)会激活尾巴"spatial" areas just as much as moving a sound source around (Smith et al. JoCN in press). This suggests that it is not 空间的 in any obvious way.

凯文·H said...

有趣的一点:我不知道't think that caudal AC is devoted to 空间的 tasks, but rather computations that are required for a lot of 空间的 tasks.

我还认为您对任务的强调过于教条。如果我们需要处理音调来说,确定是否有其他歌手不在音调范围内,或者帮助分离出两个声音,那么该音调是否会在完全不同的区域(音阶)处理?'what' 流) vs if we were processing our own pitch for vocal corrections (caudal 'sens-motor' 流)? That seems like a very wasteful setup.

您的JoCN文章当然很有趣,但是您花了太多时间。在具有相对简单的音高/空格任务的早期PP / PT区别纸上使用相同的逻辑。这些任务中的每一个都有非常简单的运动成分,因此可以公平地说他们发现的区域't have a 感官 motor component? No.

In an aside, I imagine that if you did a SVM analysis similar to 什么 you'在JoCN的数据集上完成了SPT论文,我敢打赌'd be able to pull apart some different patterns for movement/number. But I 会'如果没有,则承认以上情况't pan out =).

格雷格希科克说过...

关键是,也许"spatial" activations we are seeing in caudal AC are not the basic 空间的 computations but the higher-order use of that information. Based on the fact that these "spatial areas" seem to respond equally well to 听觉 object manipulations, maybe caudal AC is 哪里 听觉 流 segregation is happening. Yes, it is possible that with MVPA we might be able to find 空间的 selective responses in human AC but to date there is no evidence for this.

Passive listening to pitch vs. 空间的 variation indeed activates different regions. But just because something responds to stimulus x doesn'不是说那是"x area"。也许尾AC"spatial" response is really a system that is using 空间的 information to identify 听觉 objects. Or maybe it is active suppression of a 感官-motor system that wants to track the signal (subjects are usually told not to move their eyes and definitely not their heads)!

I personally think that it is still an open question whether caudal AC is a 空间的 computation *area* -- we need more research to confirm one way or the other. However, I am pretty darn sure it is not, and in fact cannot be, a "stream".