Now you feel it, now you don't.

Brain Research![Figure][1] Mice shed light on mechanisms involved in whisker sensitivity. CREDIT: MARQUES/SHUTTERSTOCK What determines the detection of a sensory stimulus? To address this question, Takahashi et al. combined in vivo two-photon imaging, electrophysiology, optogenetics, and behavioral analysis in a study of mice. Calcium signals in apical dendrites of pyramidal neurons in the somatosensory cortex controlled the perceptual threshold of the mice's whiskers. Strong reduction of dendritic calcium signaling impaired the perceptual detection threshold so that an identical stimulus could no longer be noticed. Science , this issue p. [1587][2] [1]: pending:yes [2]: /lookup/doi/10.1126/science.aah6066