The diversity of lobula plate tangential cells (LPTCs) in the Drosophila motion vision system.

To navigate through the environment, animals rely on visual feedback to control their movements relative to their surroundings. In dipteran flies, visual feedback is provided by the wide-field motion-sensitive neurons in the visual system called lobula plate tangential cells (LPTCs). Understanding the role of LPTCs in fly behaviors can address many fundamental questions on how sensory circuits guide behaviors. The blowfly was estimated to have ~ 60 LPTCs, but only a few have been identified in Drosophila. We conducted a Gal4 driver screen and identified five LPTC subtypes in Drosophila, based on their morphological characteristics: LPTCs have large arborizations in the lobula plate and project to the central brain. We compared their morphologies to the blowfly LPTCs and named them after the most similar blowfly cells: CH, H1, H2, FD1 and FD3, and V1. We further characterized their pre- and post-synaptic organizations, as well as their neurotransmitter profiles. These anatomical features largely agree with the anatomy and function of their likely blowfly counterparts. Nevertheless, several anatomical details indicate the Drosophila LPTCs may have more complex functions. Our characterization of these five LPTCs in Drosophila will facilitate further functional studies to understand their roles in the visual circuits that instruct fly behaviors.

Sequential Nonlinear Filtering of Local Motion Cues by Global Motion Circuits.

Many animals guide their movements using optic flow, the displacement of stationary objects across the retina caused by self-motion. How do animals selectively synthesize a global motion pattern from its local motion components? To what extent does this feature selectivity rely on circuit mechanisms versus dendritic processing? Here we used in vivo calcium imaging to identify pre- and postsynaptic mechanisms for processing local motion signals in global motion detection circuits in Drosophila. Lobula plate tangential cells (LPTCs) detect global motion by pooling input from local motion detectors, T4/T5 neurons. We show that T4/T5 neurons suppress responses to adjacent local motion signals whereas LPTC dendrites selectively amplify spatiotemporal sequences of local motion signals consistent with preferred global patterns. We propose that sequential nonlinear suppression and amplification operations allow optic flow circuitry to simultaneously prevent saturating responses to local signals while creating selectivity for global motion patterns critical to behavior.

Propofol target-controlled infusion for sedated gastrointestinal endoscopy: A comparison of propofol alone versus propofol-fentanyl-midazolam.

Gastrointestinal (GI) endoscopy is the major technique for diagnosis of GI disease and treatment. Various sedation and analgesia regimens such as midazolam, fentanyl, and propofol can be used during GI endoscopy. The purpose of the study was to compare propofol alone and propofol combination with midazolam and fentanyl in moderate sedation for GI endoscopy. One hundred patients undergoing GI endoscopy were enrolled in this study. All patients received a propofol target-controlled infusion (TCI) to maintain sedation during the procedure. Patients were randomly allocated into either Group P (propofol TCI alone) or Group C (combination of propofol TCI plus midazolam and fentanyl). Dermographic data, anesthetic parameters (sedation regimen, blood pressure, heart rate, and oxygen saturation), procedure parameters (procedure time, colonoscopy, or panendoscopy), propofol consumption, and adverse events (hypoxia, hypotension, and bradycardia) were all recorded. Postprocedural records included recovery time, postoperative adverse events (nausea, vomiting, dizziness, recall, and pain) and satisfaction. The average propofol consumption was 251 ± 83 mg in Group P and 159 ± 73 mg in Group C (p < 0.001). The incidence of transient hypotension was higher in Group P (p = 0.009). The recovery time and discharge time were both shorter in Group C (p < 0.001 and p = 0.006 respectively). Overall, postprocedural adverse events were similar in both groups. The postanesthetic satisfaction was comparable in both groups. TCI of propofol combined with midazolam and fentanyl achieved sedation with fewer hypotension episodes and shorter recovery and discharge time than propofol TCI alone in patients undergoing GI endoscopy.