Disynaptic inhibition shapes tuning of OFF-motion detectors in Drosophila

Gold Nanorod-Embedded PDMS Micro-Pillar Array for Localized Photothermal Stimulation

Gold nanorods (GNRs) are one of the most promising biomaterial choices for the photothermal activation of neurons due to their relative biocompatibility, unique photothermal properties, and broad optical tunability through their synthetic shape control. While photothermal stimulation using randomly accumulated GNRs successfully demonstrates the potential treatment of functional neural disorders by modulating the neuronal activities using localized heating, there are limited demonstrations to translate this new concept into large-arrayed neural stimulations. In this paper, we report an arrayed PDMS micropillar platform in which GNRs are embedded as pixel-like, arrayed photothermal stimulators at the tips of the pillars. The proposed platform will be able to localize GNRs at predetermined pillar positions and create thermal stimulations using near-infrared (NIR) light. This will address the limitations of randomly distributed GNR-based approaches. Furthermore, a flexible PDMS pillar structure will create intimate interfaces on target cells. By characterizing the spatiotemporal temperature change in the platform with rhodamine B dye, we have shown that the localized temperature can be optically modulated within 4°C, which is in the range of temperature variation required for neuromodulation using NIR light. We envision that our proposed platform has the potential to be applied as a photothermal, neuronal stimulation interface with high spatiotemporal resolution.

Heterogeneity of synaptic connectivity in the fly visual system

Visual systems are homogeneous structures, where repeating columnar units retinotopically cover the visual field. Each of these columns contain many of the same neuron types that are distinguished by anatomic, genetic and - generally - by functional properties. However, there are exceptions to this rule. In the 800 columns of the Drosophila eye, there is an anatomically and genetically identifiable cell type with variable functional properties, Tm9. Since anatomical connectivity shapes functional neuronal properties, we identified the presynaptic inputs of several hundred Tm9s across both optic lobes using the full adult female fly brain (FAFB) electron microscopic dataset and FlyWire connectome. Our work shows that Tm9 has three major and many sparsely distributed inputs. This differs from the presynaptic connectivity of other Tm neurons, which have only one major, and more stereotypic inputs than Tm9. Genetic synapse labeling showed that the heterogeneous wiring exists across individuals. Together, our data argue that the visual system uses heterogeneous, distributed circuit properties to achieve robust visual processing.