The primate midget-parvocellular (PC) visual system contributes to redgreen color detection. In this week's Journal, Jusuf et al. sought to determine whether selective wiring of the pathway connects redgreen-sensitive cells with one another. The PC pathway successively involves cone photoreceptors, midget bipolar cells, midget ganglion cells, PC relay cells in the lateral geniculate nucleus, and finally the visual cortex. To determine whether color selectivity arises from cone-selective contacts, the authors examined the OFF pathway of the peripheral retina in dichromatic (redgreen color blind) and trichromatic (color normal) marmosets. They identified OFF midget bipolar cells immunohistochemically and retrogradely labeled OFF midget ganglion cells. The authors found a loose convergence pattern of connections between these populations that was not related to redgreen color vision. Thus, the function of the PC pathway in the peripheral retina does not depend on recognition between individual members of bipolarganglion cell mosaics.
2. BDNF and Thermostatic Control
Adi Katz and Noam Meiri
We generally take our internal body thermostat for granted, but this week, Katz and Meiri provide evidence that this system is sensitive to early experience. The authors examined the developmental plasticity of this hypothalamic controller during the critical period. In the chick, heat- and cold-sensitive neurons are located in the preoptic/anterior hypothalamus (PO/AH). The authors report that brain-derived neurotrophic factor (BDNF) is a key regulator in the PO/AH. Chicks that were heat-conditioned (37.5C for 24 h) on postnatal day 3 had increases in BDNF but not nerve growth factor or neurotrophin-3. Cold conditioning also induced BDNF transcription, whereas cold acclimation in older chicks did not. Both heat- and cold-induced BDNF expression was lim
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Society for Neuroscience