Volume 10 Issue 6, June 2007

Synesthesia, in which letters or numbers elicit color perception, could be due to increased brain connectivity between relevant regions, or due to failure to inhibit feedback in cortical circuits. Diffusion tensor imaging now provides evidence for increased connectivity in word processing and binding regions of the brain.

The olfactory epithelium is one of the few sites of adult neurogenesis, but the identity of its stem cell has been debated. A report by Leung and colleagues identifies the horizontal basal cell as this progenitor.

Szapiro and Barbour describe a new mode of neuron-to-neuron communication mediated solely by spillover of neurotransmitter that diffuses out of the synaptic cleft to bind more distant receptors on postsynaptic neurons.

Reward-related events activate dopamine and other neurons in many brain areas. A report in Nature, however, now suggests that neurons in the lateral habenula signal to dopamine neurons when no reward is expected.