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Volume 12 Issue 5, May 2009

Experiments often generate large amounts of data, of which only a small fraction is typically presented in a publication. This inevitable data selection critically affects the conclusions. In neuroimaging experiments, for example, voxels (cubes in picture) are selected in a region of interest (reddish squares). The random noise in the data (dice) co-determines selection. Circularity (MÖbius band) can arise in unexpected ways when our focus on a region of interest leads us to neglect the background of excluded data (gray band). Although the problem is well understood in theory, some widespread practices may need to be adjusted.p 535

Editorial

  • The UCLA community, together with the UK-based Pro-test movement and the US campaign group Speaking of Research, is organizing a demonstration in support of animal research. The experience of scientists in the UK suggests that this approach can help stem the tide of rising violence against researchers.

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Book Review

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News & Views

  • Playing action-based video games has been shown to improve attentional processing. A study now finds that it also induces long-lasting improvements in contrast sensitivity, a basic visual function that commonly deteriorates with age. These improvements do not happen for an equivalent group who played a non-action video game.

    • Gideon P Caplovitz
    • Sabine Kastner
    News & Views
  • A study now demonstrates that the transduction channel responsible for converting sound to neural signals in the mammalian cochlea is excluded from the tallest row of stereocilia and is instead more likely in the bottom row.

    • Kateri J Spinelli
    • Peter G Gillespie
    News & Views
  • Ih is an excitatory inward current at subthreshold voltages, but enhancing Ih in CA1 pyramidal neurons leads to inhibition of action potential firing. A report in this issue suggests activation of the potassium current IM underlies this paradox.

    • Bruce P Bean
    News & Views
  • A recent study in Nature shows that sister neurons of the same lineage are preferentially interconnected to each other, thereby suggesting a local guidance mechanism using chemospecific markers.

    • Tom Binzegger
    News & Views
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Perspective

  • This perspective illustrates some of the problems involved in analyzing the complex data yielded by systems neuroscience techniques, such as brain imaging and electrophysiology. Specifically, when test statistics are not independent of the selection criteria, common analyses can produce spurious results. The authors suggest ways to avoid such errors.

    • Nikolaus Kriegeskorte
    • W Kyle Simmons
    • Chris I Baker
    Perspective
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Brief Communication

  • Here, the authors show that scratching the cutaneous receptive field of primate spinothalamic neurons produces inhibition during histamine-evoked itchiness, but not during spontaneous activity or activity evoked by pain. This suggests that the inhibition of itch by scratching is state-dependent in the spinal cord.

    • Steve Davidson
    • Xijing Zhang
    • Glenn J Giesler Jr
    Brief Communication
  • Much work has been devoted to the elucidation of pain signaling, whereas the transduction of pleasant touch has garnered less attention. In this study, the authors present data suggesting that pleasant touch is mediated by a particular dedicated type of peripheral nerve fibers, the low-threshold, unmyelinated mechanoreceptive C-tactile afferents.

    • Line S Löken
    • Johan Wessberg
    • Håkan Olausson
    Brief Communication
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Article

  • Mechanically sensitive transducer channels are responsible for the detection of sound-induced hair cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.

    • Maryline Beurg
    • Robert Fettiplace
    • Anthony J Ricci

    Collection:

    Article
  • The authors study the molecular mechanisms that discriminate axonal microtubules from somatodendritic microtubules. They report that amino acid substitutions in the beta loop region of kinsin-1 can change the compartmentalization of kinesin-1 from axons to axons and dendrites. Moreover, tyrosinated tubulins normally prevent kinesin-1 from binding to microtubules, but do not similarly inhibit kinesin-1 that is changed to allow localization to both axons and dendrites.

    • Yoshiyuki Konishi
    • Mitsutoshi Setou
    Article
  • How proteins are targeted for dendrites versus axons remains unclear. Lewis et al. show that the dendritic localization of several transmembrane proteins is dependent on specific myosin motors and an intact actin network. They also target Channelrhodopsin-2 specifically to dendrites, demonstrating a potentially important tool for probing neuronal circuits.

    • Tommy L Lewis Jr
    • Tianyi Mao
    • Don B Arnold
    Article
  • Voltage-gated channels influence processing of synaptic potentials in dendrites. George et al. report the hyperpolarization-activated cation current (Ih) exerts both direct depolarizing and net inhibitory hyperpolarizing effects on subthreshold excitatory postsynaptic potentials, as a function of synaptic strength. Interaction of Ih with an M-type potassium current (Im) underlies the inhibition.

    • Meena S George
    • L F Abbott
    • Steven A Siegelbaum
    Article
  • The authors combine electrophysiology, calcium imaging and immunohistochemistry to show that L-type Cav channels in rat A17 amacrine cells are well placed to mediate reciprocal inhibitory feedback to rod bipolar cells. However, they find that the contribution of these channels to GABA release is diminished by large-conductance Ca2+-activated potassium (BK) channels, which suppress postsynaptic depolarization in A17s and limit Cav channel activation.

    • William N Grimes
    • Wei Li
    • Jeffrey S Diamond
    Article
  • Calcium influx through AMPA receptors can trigger a switch in AMPA receptor subunit composition and cause a loss of Ca2+ permeability at the parallel fiber–stellate cell synapse in the cerebellum. Cull-Candy and colleagues now report that mGluRs and GABAB receptors both modulate this plasticity as well.

    • Leah Kelly
    • Mark Farrant
    • Stuart G Cull-Candy
    Article
  • Oxidative damage contributes to loss of nervous system function in age as well as a result of degenerative disease. But how exactly can oxidation impair neuronal function? In the worm C. elegans, this study shows that the potassium channel KVS-1 is subject to oxidation at a particular cysteine residue. Mutation of this residue led to preservation of chemosensation in aging worms.

    • Shi-Qing Cai
    • Federico Sesti
    Article
  • Akt signaling has been implicated in a number of diseases, but its role in brain disorders is less clear. Here, the authors report that CTMP, an endogenous inhibitor of Akt, is critical in the neurodegeneration that is associated with stroke. Blockade of CTMP in a stroke model rescues hippocampal neurons.

    • Takahiro Miyawaki
    • Dimitry Ofengeim
    • R Suzanne Zukin
    Article
  • Responses of primary visual cortex neurons to optimal gratings are suppressed when a non-optimal grating is superimposed. Using intrinsic optical imaging and intracellular recordings, the authors report that this effect is mediated by divisive suppression in independent population codes for stimulus orientation and strength.

    • Sean P MacEvoy
    • Thomas R Tucker
    • David Fitzpatrick
    Article
  • Selective attention is proposed to enhance relevant responses. Here the authors report that, paradoxically, responses in auditory cortex are suppressed when rats are engaged in a task, relative to responses that occurred while the animals were awake, but not performing any task.

    • Gonzalo H Otazu
    • Lung-Hao Tai
    • Anthony M Zador
    Article
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