Experiments involving molecular analysis of rare cell types from Drosophila brains often require large numbers of flies to recover enough material. This limits the experiments that researchers can do since more specific targeting of neurons means smaller numbers of relevant tissue, and that targeted tissue is hard to isolate.
Neuropixels probes are next-generation electrodes that record the activity of hundreds of neurons in the brain. They were developed through a collaboration funded by Howard Hughes Medical Institute, Wellcome Trust, Gatsby Charitable Foundation, and Allen Institute for Brain Science. The head of the collaboration is Tim Harris at HHMI Janelia Research Campus, and the electrodes are designed and fabricated by imec, the nanoelectronics research center.
Drosophila brains can be mounted on a 22x22 mm glass coverslip for efficient parallel processing of large numbers of unique samples via fluorescent in situ hybridization (FISH) or immunohistochemistry (Meissner et al., in preparation; Wu et al., 2016). FlyLight and Janelia Experimental Technology previously described a Drosophila Mounting T-Dish that aids the mounting process (https://www.janelia.org/open-science/drosophila-mounting-t-dish).
FlyFizz is an evolving webspace dedicated to enabling the exchange of information relating to one growing subfield of Drosophila brain physiology: understanding how neural circuits generate behavior by applying electrophysiological and optical imaging techniques, particularly in behaving flies. We hope this space will become a repository for supplemental information regarding published techniques and a community forum for discussion, software distribution, and job postings.
Designed primarily for use with the rodent treadmill, the Encoder Interface provides an inexpensive and easy-to-build method to connect a quadrature encoder to serial and analog interfaces. The emphasis is on simplicity and ease of assembly. The interface reads the encoder and calculates speed and direction based on the time between encoder edge changes using the internal timer on the processor. Speed is updated every time it changes. If no changes are detected over set time (typically 50 milliseconds), the speed is set to 0. Distance is also accumulated.
System Overview
Hardware Development
A GRIN lens is a small rod-shaped lens that behaves like a standard lens but has a width of less than 1mm, so it can be inserted into the brain. (1)
Implanted gradient index (grin) lenses are used to make multiphoton microscopy possible through lower cortical and subcortical regions in a mouse. In addition, they can facilitate visualization of measures like calcium transport and be used in repeated imaging for weeks and longer (2).
About the Innovation
Visualization of the axonal structures of individual neurons is critical to understand how neural signals are organized and communicated in the brain. Janelia researchers developed an imaging system for whole-brain, high-resolution fluorescence imaging. They showed that researchers could use it to trace individual axonal fibers and fine axon collaterals across the brain. These can map the long-distance projections of single neurons.
The treadmill relatively small and inexpensive compared to most existing designs. It is manually driven with a single sensor to track the movement of the belt. Some of the users make use of this sensor, but it is not necessary for all. For the users that do not monitor the position or can use their own data acquisition systems, all that is needed are the parts documented in the zip file. Fundamentally, it can be used as a free turning manual treadmill.
