Cellular & Molecular Physiology: Cell to Cell Communication | Cellular Neurophysiology | Cohen Lab | Neural Networks and Plasticity
One reason the brain is difficult to study is that many individual neurons or brain areas are active at once; conventional techniques allow one to monitor only one or a few neurons or locations at a time. We have worked on two optical methods for measuring brain activity; both utilize voltage-sensitive or Calcium-sensitive dyes and a fast camera with frame rates of 1 kHz or a 2-photon microscope. In the first variation, we use the dyes and a 2-photon microscope to follow the spike activity of individual neurons, and in favorable preparations about 500 individual neurons can be monitored simultaneously. We hope that monitoring many neurons simultaneously will improve our understanding about how nervous systems are organized to generate behaviors. In the second variation, each pixel in the recording receives light from a large number of neurons and processes (e.g. from an area of cortex 20 um x 20 um) and thus each signal represents the average of a population of neurons. There are several interesting aspects of vertebrate brain function where populations are involved.
Specialized Terms: Brain; Central Nervous System; Neurons; Vertebrate Physiology; Olfaction; Olfactory Bulb; Protein Sensors of Voltage and Calcium
Extensive Research Description
One active area is the development of fluorescent protein sensors of membrane potential. At present the voltage signals are just large enough to be useful in monitoring activity in invertebrate and mammalian nervous systems. We hope to find sensors that are both faster and have larger signals.
A second area is understanding the role of the mammalian olfactory bulb in olfactory processing. We have started comparing the input (from the nose) and the output (carried by mitral/tufted cells) to determine the olfactory transformation carried out by the bulb. We also want to know what the interneurons do to carry out this transformation.
- Storace, D.A, Braubach, O.R., Jin, L., Cohen, L.B., Sung, U. (2015) Monitoring brain activity with protein voltage and calcium sensors. Nature Scientific Reports, | 5:10212 | DO: 10.1038/srep10212
- Homma, R., Y. Kovalchuk, A. Konnerth, L.B. Cohen, and O. Garaschuk. (2013) In vivo functional properties of juxtaglomerular neurons in the mouse olfactory bulb. Frontiers in Neural Circuits, 7:23. doi: 10.3389/fncir.2013.00023.
- Jin, L., Han, Z., Platisa, J., Wooltorton, J.R.A., Cohen, L.B., and Pieribone, V.A., (2012) Single action potentials and subthreshold electrical events visualized in neurons using a novel fluorescent protein voltage sensor. Neuron, 75: 779-785. PMC3439164.
- Lam YW, Cohen LB, Zochowski MR. Odorant specificity of three oscillations and the DC signal in the turtle olfactory bulb. Euro J Neurosci, 17(3):436-46, 2003
- Homma R, Cohen LB, Kosmidis EK, Youngentob SL. Perceptual stability during dramatic changes in olfactory bulb activation maps and dramatic declines in activation amplitudes. Euro J Neurosci, 29:1027-1034, 2009.
- Wachowiak, M and Cohen L.B., (2001) . Representation of odorants by receptor neuron input to the mouse olfactory bulb. Neuron, 32: 723-735.