Finally, it is notable that of the two major ePN targets, iPN axons only project to the lateral horn but spare the mushroom body (Figure 7D). The mushroom body is a well-documented center for olfactory learning and memory, whereas PN projections selleck chemical to the lateral horn are implicated in regulating innate

olfactory behavior (Heimbeck et al., 2001) (see also Parnas et al., 2013). ePN axons exhibit striking stereotypy in their terminal arborization patterns in the lateral horn, but not in the mushroom body (Caron et al., 2013, Jefferis et al., 2007, Marin et al., 2002 and Wong et al., 2002). Recent anatomical tracing in mice also revealed differential input organization in distinct olfactory cortical areas (Miyamichi

et al., 2011 and Sosulski selleck kinase inhibitor et al., 2011), suggesting a common principle in olfactory systems of insects and mammals. The selective innervation by iPNs of targeting neurons in the lateral horn suggests that regulation of innate olfactory behavior engages an additional level of specific inhibition to ensure that olfactory information carrying different biological values, such as food and pheromone, is funneled into distinct downstream circuits, resulting in the activation of distinct behavioral outputs. Two-photon GCaMP imaging experiments were performed with either a LSM 510 Two-Photon Laser-Scanning Confocal Microscope (Zeiss) with a 40× NA 0.8 water-immersion objective (Zeiss) and modelocked Ti:Sapphire laser (Coherent) tuned to 920 nm or a customized two-photon microscope (Prairie Technologies) with a 40× NA 1.0 water-immersion all objective (Zeiss) and laser tuned to 927 nm at ∼73–75°F. The excitation power at the specimen was ∼10 mW, and the pixel dwell time was 2.0 μs. All lateral horn images were acquired at a 2.488 Hz frame rate with 460 × 300 pixels per frame. Each imaging cycle was 45 s, and

500 msec odor stimuli (as determined by the solenoid valves) were always delivered at 5 s. To minimize bleaching, images were only taken from the first 16 s (40 frames) of each cycle. In most experiments, the same odor was applied every other cycle for three repeats, while different odors were usually applied in an alternate manner to minimize potential olfactory adaptation. Image acquisition was suspended during the 500 msec optogenetic stimulation period to protect the PMTs. On average, each imaging session lasted ∼1.5 hr, with most of the flies appearing healthy at the end of the experiments; they could still move their legs at a regular pace. For some experiments, the fly brains were dissected and fixed for post hoc staining. Time-lapse imaging series of GCaMP3 from a single z plane were usually recorded in the control hemisphere once before mACT transection and once after transection.