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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
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.
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.
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.
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.
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.
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.
At the calyx of Held nerve terminal, Wu and Paradiso show that small hyperpolarizations or depolarizations can travel back up the axon and influence the threshold for action potential initiation.
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.
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.
This study finds that playing an action video game results in improvements in visual contrast sensitivity. These improvements do not happen for an equivalent group who played a non-action video game.
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.
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.
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.
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.
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.
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.
This study shows that chronic amphetamine exposure in rats downregulates the NMDA receptor NR2B subunit on striatal neurons. This loss of NR2B has consequences for synaptic transmission and for behavior, sensitizing the rats to the stimulant.
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.
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.
The authors identify motoneurons selectively vulnerable and resistant to motorneuron disease longitudinally in vivo. Their data suggests that subtype-selective ER stress responses influence disease pathology and the progressive manifestations of weakening and paralysis.
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.
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.
Using computational methods to model neural recordings and behavioral data, the authors find that reinforcement learning rules, combined with a standard model of decision-making, can explain a range of experimentally observed phenomena in perceptual learning.