PT - JOURNAL ARTICLE AU - Joesch, Maximilian AU - Weber, Franz AU - Eichner, Hubert AU - Borst, Alexander TI - Functional Specialization of Parallel Motion Detection Circuits in the Fly AID - 10.1523/JNEUROSCI.3374-12.2013 DP - 2013 Jan 16 TA - The Journal of Neuroscience PG - 902--905 VI - 33 IP - 3 4099 - http://www.jneurosci.org/content/33/3/902.short 4100 - http://www.jneurosci.org/content/33/3/902.full SO - J. Neurosci.2013 Jan 16; 33 AB - In the fly Drosophila melanogaster, photoreceptor input to motion vision is split into two parallel pathways as represented by first-order interneurons L1 and L2 (Rister et al., 2007; Joesch et al., 2010). However, how these pathways are functionally specialized remains controversial. One study (Eichner et al., 2011) proposed that the L1-pathway evaluates only sequences of brightness increments (ON-ON), while the L2-pathway processes exclusively brightness decrements (OFF-OFF). Another study (Clark et al., 2011) proposed that each of the two pathways evaluates both ON-ON and OFF-OFF sequences. To decide between these alternatives, we recorded from motion-sensitive neurons in flies in which the output from either L1 or L2 was genetically blocked. We found that blocking L1 abolishes ON-ON responses but leaves OFF-OFF responses intact. The opposite was true, when the output from L2 was blocked. We conclude that the L1 and L2 pathways are functionally specialized to detect ON-ON and OFF-OFF sequences, respectively.