4 research outputs found
All-viral tracing of monosynaptic inputs to single birthdate-defined neurons in the intact brain
Neuronal firing patterns are the result of inputs converging onto single cells. Identifying these inputs, anatomically and functionally, is essential to understand how neurons integrate information. Single-cell electroporation of helper genes and subsequent local injection of recombinant rabies viruses enable precise mapping of inputs to individual cells in superficial layers of the intact cortex. However, access to neurons in deeper structures requires more invasive procedures, including removal of overlying tissue. We developed a method that, through a combination of virus injections, allows us to target 4 or fewer hippocampal cells 48% of the time and a single cell 16% of the time in wild-type mice without use of electroporation or tissue aspiration. We identify local and distant monosynaptic inputs that can be functionally characterized; in vivo; . By expanding the toolbox for monosynaptic circuit tracing, this method will help further our understanding of neuronal integration at the level of single cells
General Anesthetic Conditions Induce Network Synchrony and Disrupt Sensory Processing in the Cortex
General anesthetics are commonly used in animal models to study how sensory
signals are represented in the brain. Here, we used two-photon (2P) calcium
activity imaging with cellular resolution to investigate how neuronal activity
in layer 2/3 of the mouse barrel cortex is modified under the influence of
different concentrations of chemically distinct general anesthetics. Our
results show that a high isoflurane dose induces synchrony in local neuronal
networks and these cortical activity patterns closely resemble those observed
in EEG recordings under deep anesthesia. Moreover, ketamine and urethane also
induced similar activity patterns. While investigating the effects of deep
isoflurane anesthesia on whisker and auditory evoked responses in the barrel
cortex, we found that dedicated spatial regions for sensory signal processing
become disrupted. We propose that our isoflurane-2P imaging paradigm can serve
as an attractive model system to dissect cellular and molecular mechanisms
that induce the anesthetic state, and it might also provide important insight
into sleep-like brain states and consciousness