In the early 20th century, sensing was typically considered passive. The prevailing notion was that the nervous system processed sensory inputs without playing an active role in modulating the signals. Around 1950, R. W. Sperry as well as E. von Holst and H. Mittelstaedt proposed that self-generated neural activity, which was labeled "reafference" by von Holst and Mittelstaedt, is also important in sensory processing. Over the years, the notion that sensing is an active process, with self-generated “efference copy” processed alongside sensory inflow, has been demonstrated across a broad range of sensory systems in a wide variety of species (e.g., insects, bats, rats, and humans). This Collection from the Journal of Neurophysiology is focused on how self-generated neural activity influences the processing of sensory information. (Image: http://dx.doi.org/10.1152/jn.00657.2015)
Cover: Multiregional Brain-on-a-Chip in vitro model. Neurons (green) from different brain regions (here prefrontal cortex, left, and amygdala, right) are restricted to distinct areas, but are connecting controllably to the other brain region through axons which are guided by microcontact printed lines. This is a zoom in image from the entire brain-on-a-chip model, which consists of three brain regions. This multiregional brain-on-a-chip is electrically active and reacts to drug applications in a brain region dependent way. Astrocytes are labelled in red. The smallest distance between the different brain areas is 1 mm. From Dauth S, Maoz BM, Sheehy SP, Hemphill MA, Murty T, Macedonia MK, Greer AM, Budnik B, Parker KK. Neurons derived from different brain regions are inherently different in vitro: a novel multiregional brain-on-a-chip. J Neurophysiol 117: 1320 –1341, 2017; doi:10.1152/jn.00575.2016.