Action Potential

New NN papers (published online December 11th)

Fox et al., Coherent spontaneous activity accounts for trial-to-trial variability in human evoked brain responses

Tanaka, Inactivation of the central thalamus delays self-timed saccades

Bermingham et al., The claw paw mutation reveals a role for Lgi4 in peripheral nerve development

Duff et al., Development of shared information in communication despite hippocampal amnesia

Hiramoto & Hiromi, ROBO directs axon crossing of segmental boundaries by suppressing responsiveness to relocalized Netrin

Liu et al., CaM kinase II phosphorylation of slo Thr107 regulates activity and ethanol responses of BK channels

Morgan et al., Axons and dendrites originate from neuroepithelial-like processes of retinal bipolar cells

Comments welcome.

Comments

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    Zhang Guanyang said:

    Dear Bloggers,

    I guess blogger is a more affecionate title for people who blog. That’s why i use it here.

    I would like to inform you that the function of ‘subscribe to this blog’s feed’ does not seem to work. It leads to a page of all HTML codes after i click on it. Could you look into this matter?

    Thanks!

    Guanyang

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    Annette Markus said:

    I’m sorry the RSS feed is not working. We will look into it and hopefully get it fixed quickly.

    Thanks,

    Annette

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    John O'Leary said:

    The RSS feed works fine for me. The “subscribe” link just gives you the location of the feed and will in most browsers (Apple’s Safari is one exception) give you a page of code when you click on it.

    You need an RSS reader to actually use RSS feeds. Bloglines is one way to read feeds.

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    Xiaohong Wan said:

    Coherent spontaneous activity or fMRI artifacts account for trial-to-trial variability? – comments to Fox et al. Coherent spontaneous activity accounts for trial-to-trial variability in human evoked brain responses 1

    At the electrophysiological level, Arieli et al. 2 demonstrated that the ongoing activity accounts for the large variability of evoked cortical responses. In the paper of Fox et al. 1, the same question is asked that what accounts for the trial-to-trial variability of event-related fMRI responses. They have showed that the simultaneous fluctuations of the RMC are corresponding to the trial-to-trial variability of the evoked LMC fMRI responses by reducing 40% noise. They have suggested that the signal measured in the RMC represents the spontaneous fluctuations that are coherent within the somatomotor system. Hence, they supported their hypothesis that the coherent spontaneous activity accounts for trial-to-trial variability, and demonstrated that the spontaneous and task-related activity have an approximately linear superposition fashion.

    However, I am strongly suspecting that the concurrent RMC fluctuations represent the coherent spontaneous activity of the somatomotor system, Given that the coupling mechanism between the hemodynamics and the underlying neuronal activity is not clear and the BOLD fMRI has amounts of noises. Since Biswal et al. 3 showed the significant correlation of spontaneous fMRI in the LMC and RMC with a fast fMRI scanning, a few of groups also showed the spontaneous correlation within the brain by a conventional fMRI scanning [4, 5, 6]. However, none of them clearly demonstrated these fMRI fluctuations are not fMRI artifacts. Evenly, they did not remove the well-known artifacts using the conventional fMRI scanning [7, 8]. Till now, there are no works directly demonstrating that the spontaneous cortical activity can be detected by the fMRI technique.

    As Fox et al. 1 indicated in their supplement not only the selected RMC but also the other regions can reduce the noise more or less, for example, the IPS can account for 16% SNR. These results show that the correlated fMRI fluctuations are not only restricted within the somatomotor system, but rather in an extensive region.

    Taken together, the concurrent RMC fMRI fluctuations might just be artifacts. This interpretation gives a simple explanation why it accounts for the trial-to-trial variability of evoked LMC responses and why the two responses are linearly superposited. However, at least, Fox et al. show us a method to improve the SNR of evoked fMRI responses.

    References:

    1 Fox, M.D. , Snyder, A., Zacks, J.M., Raichle, M.E. Nature Neurosci. 9, 23 – 25 (2006).

    2 Arieli, A., Sterkin, A., Grinvald, A. & Aertsent, A. Science 273, 1868–1871 (1996).

    3 Biswal, B. , Yetkin, F. , Haughton, V. & Hyde, J. Magn. Reson. Med. 34, 537–541 (1995).

    4 Lowe, M.J., Mock, B.J. & Sorenson, J.A. Neuroimage 7, 119–132 (1998).

    5 Fox, M.D. et al. Proc. Natl. Acad. Sci. USA 102, 9673–9678 (2005).

    6 Fransson P., Human Brain Mapp. 26, 15-29 (2005).

    7 Lund T. E., Magn Reson Med 46, 628 (2001)

    8 Wise, R.G., Ide, K., Poulin, M. J., Tracey,

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    Benjamin A Schulz said:

    Mozilla Firefox users will see an orange RSS symbol in the address bar for RSS-enabled pages. Clicking on it let’s you add the feed as a “LiveBookmark”, which becomes an automatically updated folder in your bookmarks with links to the feed’s current content.

    There are also several Firefox extensions that display RSS feeds in a straight-forward manner. Good ones include Sage (simple, streamlined), and Wizz (feature-rich).