DIC imaging for identification of motor and sensory nerves

Identification of motor and sensory nerves is important in applications such as nerve injury repair.Conventional practice relies on time consuming staining methods for this purpose.Here,we use laser scanning infrared diferential interference contrast(IR-DIC)microscopy for label-free observation of the two types of nerve.Ventral and dorsal nerve roots of adult beagle dogs were collected and sections of different thicknesses were imaged with an IR-DIC microscope.Different texture patterns of the IR-DIC images of the motor and sensory nerve can be distinguished when the section thickness increases to 40 pm.This suggests that nerve fibers in motor and sensory nerves have different distribution patterns.The result hints a potential new way for more rapid identification of nerve type in peripheral nerve repair surgery.

OBSERVING NEURONAL ACTIVITIES WITH RANDOM ACCESS TWO-PHOTON MICROSCOPE

As a second messenger in signal transduction,calcium ion plays a very important role in neuronal information processing and integrating.Limited by the imaging technique,it is difficult to simultaneously perform deep tissue imaging and measure intracellular free calcium concentration([Ca^(2+)]i)in different compartments of neurons in brain slice noncollinearly.By means of random access two-photon microscopy,which provides high optical penetration into tissues and low photo damage,we successfully measured[Ca^(2+)]i of different parts of pyramidal neurons in neocortical layer V in rat brain slices with high spatial and temporal resolution.Combining the patch clamp technique,we stimulated the soma with depolarizing current and explored the dynamics of calcium in pyramidal neurons.

Divergent Projection Patterns Revealed by Reconstruction of Individual Neurons in Orbitofrontal Cortex

The orbitofrontal cortex(OFC)is involved in diverse brain functions via its extensive projections to multiple target regions.There is a growing understanding of the overall outputs of the OFC at the population level,but reports of the projection patterns of individual OFC neurons across different cortical layers remain rare.Here,by combining neuronal sparse and bright labeling with a whole-brain florescence imaging system(fMOST),we obtained an uninterrupted three-dimensional whole-brain dataset and achieved the full morphological reconstruction of 25 OFC pyramidal neurons.We compared the wholebrain projection targets of these individual OFC neurons in different cortical layers as well as in the same cortical layer.We found cortical layer-dependent projections characterized by divergent patterns for information delivery.Our study not only provides a structural basis for understanding the principles of laminar organizations in the OFC,but also provides clues for future functional and behavioral studies on OFC pyramidal neurons.

Neural spike train reconstruction from calcium imaging via a signal-shape composition model

Dear Editor,Since calcium imaging can simultaneously record the calcium signals of several hundred neurons, it has been a powerful tool in measuring the functional activity of neural populations. However, calcium imaging is an indirect measurement of neuronal firing activity, and this technique requires reconstructing the AP trains from the corresponding calcium fluorescence signals of the recorded neurons.

Direction Selectivityof TmY Neurites in Drosophila

The perception of motion is an important func-tion of vision.Neural wiring diagrams for extracting direc-tional information have been obtained by connectome recon-struction.Direction selectivity in Drosophila is thought to originate in T4/T5 neurons through integrating inputs with different temporal filtering properties.Through genetic screening based on synaptic distribution,we isolated a new type of TmY neuron,termed TmY-ds,that form recipro-cal synaptic connections with T4/T5 neurons.Its neurites responded to grating motion along the four cardinal direc-tions and showed a variety of direction selectivity.Intrigu-ingly,its direction selectivity originated from temporal filtering neurons rather than T4/T5.Genetic silencing and activation experiments showed that TmY-ds neurons are functionally upstream of T4/T5.Our results suggest that direction selectivity is generated in a tripartite circuit formed among these three neurons—temporal filtering,TmY-ds,and T4/T5 neurons,in which TmY-ds plays a role in the enhancement of direction selectivity in T4/T5 neurons.