Sensory physiology

KV1.3 channel gene-targeted deletion produces 'super-smeller mice' with altered glomeruli, interacting scaffold proteins, and biophysics. Fadool, D. A. et al. Neuron 41, 389–404 (2004)

Mice with a targeted deletion of the voltage-dependent K+ channel KV1.3 are found to have a heightened sense of smell, with a threshold for odour detection that is 1,000- to 10,000-fold lower than the wild type. Anatomically, they have smaller olfactory glomeruli than wild-type mice, and more of them. Potassium currents in olfactory bulb neurons from the KV1.3−/− mice have slower inactivation and a modified voltage dependence, and are not modulated by activators of receptor tyrosine signalling cascades.

Neurological disorders

Diffusion tensor MRI of early upper motor neuron involvement in amyotrophic lateral sclerosis. Sach, M. et al. Brain 127, 340–350 (2004)

It is difficult to assess the involvement of upper motor neurons during the early stages of amyotrophic lateral sclerosis (ALS). Sach and colleagues show that diffusion tensor imaging can identify changes that are related to upper motor neuron involvement in patients with ALS before they show clinical symptoms related to corticospinal tract lesions.

Neural modulation

Selective D2 receptor actions on the functional circuitry of working memory. Wang, M. et al. Science 303, 853–856 (2004)

D2 dopamine receptors have been implicated in various cognitive and motor functions. To clarify the functions of these receptors, Wang et al. recorded from prefrontal cortical neurons in monkeys performing an oculomotor task while applying selective D2 agonists and antagonists through iontophoresis. They found that D2 receptors modulate saccade-related activity, whereas D1 receptors modulate memory-related activity.

Gene expression

Stochastic yet biased expression of multiple Dscam splice variants by individual cells. Neves, G. et al. Nature Genet. 1 February 2004 (10.1038/ng1299)

The Drosophila homologue of Dscam is essential for axon guidance and undergoes alternative splicing to generate 38,016 possible isoforms. Neves et al. used single-cell RT-PCR to investigate the expression of Dscam in single photoreceptors. The authors find that individual photoreceptors express 14–50 mRNAs from the possible range of Dscam isoforms, and that populations of photoreceptor subtypes express broad but distinctive subsets of Dscam. They propose that the Dscam repertoire of a cell could provide a mechanism for generating unique cell identity in the nervous system.