2009年2月11日,星期三

颞颞部区域Spt:im体育运动整合还是听觉影像?

Area Spt是我最喜欢的大脑位置之一。自从2001年和2003年在两篇论文中报道了它的存在以来,我们一直在努力表征其响应特性(Buchsbaum,Hickok和Humphries,2001; Hickok,Buchsbaum,Humphries和Muftuler,2003)。 Spt位于左后 S伊尔维亚地区 parietal-t帝国边界。 Spt的主要特征是它在语音感知期间和(隐蔽的)语音产生过程中均被激活。随后的工作发现,Spt不是特定于语音的,因为它也在音调旋律感知和产生(嗡嗡声)期间做出反应,并且Spt对声带手势具有相对选择性,因为它在音调旋律的感知和隐蔽嗡嗡声中的反应比在声调旋律期间的反应要多。音调旋律的感知和想象钢琴演奏(Pa&Hickok,2008)。根据这样的证据,我认为Spt是声带运动效应器的im体育运动整合区域,就像猴子区域LIP是眼睛的im体育运动整合区域和顶触区域(或区域(AIP)是手动执行器的im体育运动区域。

One nagging objection that has been raised more than once is this: "Isn't your 'motor' activity just auditory imagery?" That is, maybe during covert 排演 there is some kind of motor-to-sensory discharge that serves to keep active 感官 representations of speech in auditory cortex (i.e., Spt). Another possible objection that is less often raised is that the "感官" activity we see in Spt isn't really 感官 but is really motor preparation.

就在昨天,我们收到了一篇论文, 神经生理学杂志 我认为排除了此类异议(Hickok,冈田,& Serences, in press). Here's the logic. If Spt really is just like other 感官-motor integration areas (e.g., LIP, AIP), it will be composed of a population of 感官-weighted cells, motor-weighted cells, and truly 感官-motor cells. Two things follow, (i) the BOLD response to combined 感官-motor stimulation should be greater than the BOLD response to either 感官 or motor activation alone (because 感官-motor stimulation activates a larger cohort of cells than either 感官 or motor alone), and (ii) the pattern of activity within Spt may be different during 感官 activation than during motor activation (on the assumption that 感官 and motor weighted cells are not perfectly distributed across the sampled voxels within Spt. If we can show that the response to 感官 stimulation and motor stimulation are different, then Spt activity can't be all 感官 or all motor; it must be 感官-motor.

这是我们使用fMRI测试这些预测的方法。受试者要么听15s的连续语音(连续听),听3s的语音,然后休息12s(听+休息),要么听3s的语音,然后秘密地将语音演练12s(听+排练) :



First the BOLD results. Spt was identified separately in each subject by the subtraction, listen+rehearse minus listen+rest. This picks out areas that are more active during 排演 than rest. Here's the BOLD activation for each condition in each subject's Spt ROI:


在听+排练的情况下,我们预测在试验的第一阶段,BOLD响应将以im体育刺激为主,在试验的中期将混合im体育和排练响应(因为im体育响应尚未完成)。排练响应开始时还没有衰减),然后在试验的最后阶段将以排练响应为主。如果您将听+排练响应曲线与连续听曲线进行比较,您会发现此预测是如何产生的:第一阶段的响应相等(因为两个条件都涉及相同的im体育刺激),然后是连续听条件下的活动达到饱和状态并保持大致相同的活动水平,直到试验结束,而聆听+排练中的活动继续升高(大概是由于im体育和运动排练反应相加),然后回落到试验结束(大概是因为感官信号衰减)。因此,大胆的预测是成功的。

接下来,我们使用模式分类分析来查看在im体育刺激与运动激活过程中,Spt中反应的模式是否不同。从数据中删除了幅度信息以进行此分析。我们训练了一个支持向量机,对除了一次运行外的所有数据的两个条件(连续监听与监听+排练)进行分类,然后在其余运行中测试了其分类准确性。重复执行此保留单次操作程序,直到对所有运行进行分类。此外,我们在试验中的三个不同时间范围内进行了此分类:早期,中期和晚期。预测是,当两个条件由不同信号源最大程度地支配时,即在最后一个时间仓中,分类精度应该最大,而当两个信号都主要是im体育时,分类精度应该不比第一个时间仓中的偶然性好。这是我们发现的结果(蓝线代表通过排列测试确定的分类精度的5%上下边界):



Classification accuracy for the continuous listen vs. listen+rehearse conditions was significantly above chance only in the last time bin, that is when the BOLD signal was maximally dominated by distinct input sources, one 感官 the other motor. Notice too that 在 this time point the BOLD amplitude in these two signal are the same, which provides additional evidence that classification accuracy has nothing to do with amplitude.

If the pattern of activity in Spt is different during 感官 stimulation compared to during motor stimulation (and independent of amplitude), then Spt activity can't be all 感官 or all motor. This, together with the range of supporting evidence indicates that Spt is indeed a 感官-motor area.

参考文献

Buchsbaum B,Hickok G和HumphriesC。左后上颞颞回在语音处理中对语音感知和产生的作用。认知科学25:663-678,2001。

Hickok G,Buchsbaum B,Humphries C和Muftuler T.fMRI显示的听觉-运动互动:Spt区域的语音,音乐和工作记忆。 Journal of Cognitive Neuroscience 15:673-682,2003。

Hickok, G., Okada, K., & Serences, J. (in press). Area Spt in the human planum temporale supports 感官-motor integration for the speech processing. 神经生理学杂志

Pa J, and Hickok G. A parietal-temporal 感官-motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians. Neuropsychologia 46: 362-368, 2008.

9条评论:

匿名 said...

感谢您的发布。很有意思。但:

1)排练期间较高的BOLD可以用比收听期间更省力的处理来解释吗?其他方面的响应情况如何?

2)您如何说分类精度是“与幅度无关”?在使用SVM之前,您是否真的删除了逐个体素的条件均值响应?怎么样?即使条件之间的平均值在单变量测试中低于显着水平(并且在12 s时也不相同),SVM也会在信号振幅上集成微弱但始终如一的差异...

格雷格希科克说过...

1)否。因为如果只是努力,那么您会希望在聆听+排练条件下的幅度在试验结束之前一直保持较高的水平,但事实并非如此,它会回落到等于聆听条件的水平。

2.是的。在支持向量机之前,逐次运行对数据进行标准化(z转换)。正如我在文章中所指出的那样,您可以看到幅度不是决定因素:在试验的中间,幅度差异最大,但分类准确性并未明显高于偶然性;仅在没有幅度差异的最后一个时间段内,准确性才大于偶然性。

匿名 said...

This looks like a convincing paper. The plots you show are wonderful. I think it would be even better if you could show plots for a few other ROIs, ones that might be thought to be involved in auditory imagery, 排演 or response preparation (e.g. AI, left STG, dlPFC/Insula/vPM). If they show the profiles that would be predicted by your line of argument it would be very impressive. Any chance of posting them here?

格雷格希科克说过...

A reviewer suggested the same thing. It seems like a good idea 在 first, but in fact it's not that informative because you don't need pattern classification to show that say A1 shows differential responses to 感官 and motor events: it's clear from the amplitude data! Where pattern classification is useful, is when the amplitude in an area is the same in two conditions. Then you can see if the signal in the area is being driven by different sources.

还要注意,我们作为线索中时间点函数的分析提供了内部(即ROI)控制。此外,我们研究了连续听与静听+休息条件下的Spt分类准确度(在论文中)-在任何时间点,其准确性都没有比偶然性明显好。

匿名 said...

抱歉,格雷格,我不清楚。我的意思是这些其他区域的BOLD幅度随时间变化的曲线图。

彼得说过...

非常有趣的数据。一件事让我有些困惑。 9秒的BOLD响应对于监听+休息和连续监听是相同的。这意味着当这两个条件相同时,第9秒的BOLD响应仍主要反映了前3秒的神经活动。但是,聆听+排练与连续聆听之间的最大差异也发生在9秒。试听和排练任务中的对象在开始的3秒钟内正在听音乐时,可能已经在排练吗?

格雷格希科克说过...

是的,那是我的猜测。受试者知道他们将排练刺激(提示会在方块的开头出现),因此他们在语音刺激结束之前就开始了。

布拉德·布斯鲍姆(Brad Buchsbaum)说过...

这是模式分类的创新用途。做得好!

有两件事要考虑。首先,使用监听和排练>只听的对比使本地化Spt偏向于寻找运动加权反应。通常情况下,我们已经将SPT识别为具有“听”和“排练”的结合,这在im体育/运动方面没有偏见。当以这种方式隔离时,Spt激活的时程通常会在im体育阶段显示出比在激活期间更高的峰值。"rehearsal" phase. This pattern is not evident in your data where you see greater activity for 排演 than continuous 感官 stimulation. This may be because you have identified an ROI that is not strongly sensitive to 感官 input due to your localizer contrast. I would be curious to see what the time courses (and spatial distribution of "Spt")的样子,如果您改为使用连接符本地化器。

格雷格希科克说过...

嗨,布拉德,
感谢您抓住这一点。我其实不是'我在博客条目中对ROI定义的描述准确无误。这里 's引用我们描述我们实际工作的论文的引文:

"在个别受试者中,ROI的定义是(i)反映连续语音连词的激活>空休息块,语音和排练>(ii)位于左颞颞部区域内(在Heschl的Sylvian裂隙内)’s gyrus),通过共同注册每个主题来定义’带有自己的结构MRI的激活图。"

因此,我们确实像您(和我们)一贯那样使用连词。那么,为什么排练比只听*更多*激活?首先,我不't think there is actually more activation for 排演 than for listen. I think that Spt activates roughly equally to these two processes. It looks like more activation for rehearse than listen in the graph I posted because both processes are summing in the listen+rehearse condition in the middle phase of the trial; notice that rehearse and listen are equal by the end of the trial.

您指出,与在Spt中进行试验的排练阶段相比,在聆听中通常可以看到*更大*的活动。我同意,但我不 '认为这与我们在本研究中发现的不一致。回顾一下Hickok,Buchsbaum等人的图3A。 (2003)。该图显示了在侦听+练习状态以及侦听+休息状态下的Spt活动。注意第一个高峰"sensory" activation is greater in the listen+rehearse condition than listen+rest. I think this is because some of the rehearse response is already mixing in (summing) with the listen response. Notice too that the peak of the 感官 response in the listen+rest condition is similar to the rehearse amplitude *at 12-15s post trial onset* (which is where the trial ended in the present experiment).

你怎么看?