Neurotechnique

Second harmonic imaging of membrane potential of neurons with retinal. Nemet, B. A. et al. J. Biomed. Opt. 9, 873–881 (2004)

The authors describe an optical method for imaging the membrane potential of neurons using all-trans retinal. When retinal is adsorbed to the neuronal plasma membrane, changes in membrane potential cause a change in its second harmonic generation that can be used to produce high-resolution images of live neurons. This study was carried out using cultured neurons, but it should be possible to extend the technique to acute brain slices.

Development

Control of dendritic branching and tiling by the tricornered-kinase/furry signaling pathway in Drosophila sensory neurons. Emoto, K. et al. Cell 119, 245–256 (2004)

Dendritic fields are often precisely controlled so that a given territory is completely covered by the dendrites of neighbouring neurons without any overlap. Emoto and colleagues show that the tiling of sensory neuron dendrites in Drosophila requires two evolutionarily conserved proteins — the tricornered (TRC) kinase and Furry (FRY). Flies in which either is mutated have dendrites with excessive branching and overlap. The evidence indicates that TRC and FRY promote repulsion between like dendrites and also limit dendritic branching.

Eye Movements

Dissociation of spatial attention and saccade preparation. Juan, C.-H. et al. Proc. Natl Acad. Sci. USA 101, 15541–15544 (2004)

It is unclear whether covert shifts in attention represent shifts in gaze that are planned but not executed, or an independent process. To address this question, Juan et al. measured deviations in saccades evoked by stimulation of the frontal eye fields in macaque monkeys during a pro-saccade or anti-saccade task. The results indicate that neurons in the frontal eye fields can covertly orient attention without preparing to carry out an eye movement.

Synaptic Plasticity

Single-shock LTD by local dendritic spikes in pyramidal neurons of mouse visual cortex. Holfhoff, K. et al. J. Physiol. 560.1, 27–36 (2004)

The dendrites of pyramidal neurons in layer 5 of mouse visual cortex show a variety of spiking activity, including spatially restricted spikes that are triggered by NMDA (N-methyl-D-aspartate) receptor activation. The authors use two-photon and confocal imaging to investigate these spikes, and find that they involve a high-amplitude, rapid calcium transient that is restricted to a small compartment of the dendrite. A single such spike, elicted by a single synaptic stimulus, can produce local, input-specific, long-term synaptic depression.