Irina Bystron, Zoltán Molnár, Vladimir Otellin, and Colin Blakemore
This week, Bystron et al. provide information on the earliest neurons that appear in the human telencephalon, well before the formation of the cortical plate or the onset of synaptogenesis. They identified the cells as neurons based on microtubule associated protein 2 (MAP2) immunoreactivity in tissue available from embryonic forebrain 1 - 2 months after conception. These cells may serve a role in guiding axons or transverse neuronal migration akin to the "pioneer" neurons in invertebrates or the transient early neurons in several mammalian species.
2. Goals and Habits in the Overtrained Rat
Alexis Faure, Ulrike Haberland, Françoise Condé, and Nicole El Massioui
While learning a task, goal-directed performance is dictated by associations between an action and the outcome. If the outcome or reward is reduced, the behavior changes as well. However after many repetitions, reward-motivated actions become a matter of habit and essentially continue regardless of the outcome. This week, Faure et al. examine the turning point between action–outcome and stimulus–response associations in the rat nigrostriatal dopaminergic pathway.