Imaging Brain Activity With Voltage- and Calcium-Sensitive Dyes

Abstract

This paper presents three examples of imaging brain activity with voltage- or calcium-sensitive dyes and then discusses the methodological aspects of the measurements that are needed to achieve an optimal signal-to-noise ratio. Internally injected voltage-sensitive dye can be used to monitor membrane potential in the dendrites of invertebrate and vertebrate neurons in in vitro preparations. Both invertebrate and vertebrate ganglia can be bathed in voltage-sensitive dyes to stain all of the cell bodies in the preparation. These dyes can then be used to follow the spike activity of many neurons simultaneously while the preparations are generating behaviors. Calcium-sensitive dyes that are internalized into olfactory receptor neurons in the nose will, after several days, be transported to the nerve terminals of these cells in the olfactory bulb. There they can be used to measure the input from the nose to the bulb. Three kinds of noise are discussed. a. Shot noise from the random emission of photons from the preparation. b. Vibrational noise from external sources. c. Noise that occurs in the absence of light, the dark noise. Three different parts of the light measuring apparatus are discussed: the light sources, the optics, and the cameras. The major effort presently underway to improve the usefulness of optical recordings of brain activity are to find methods for staining individual cell types in the brain. Most of these efforts center around fluorescent protein sensors of activity.

Topography and Response Timing of Intact Cerebellum Stained With Absorbance Voltage-Sensitive Dye

“…Because the turtle Cb is thin, a novel approach is developed here to simultaneously record physiological responses across the entire Cb surface using voltage-sensitive dye recording techniques developed by Salzberg and Grinvald (Baker et al 2005; see modern reviews by Ebner and Chen 1995;Salzberg et al 1977;Wu et al 1998). This technique permits us to measure physiological activity with submillisecond resolution from a two-dimensional sheet of cortical tissue during afferent stimulation.…”

Imaging synaptic inhibition in transgenic mice expressing the chloride indicator, Clomeleon

“…Voltage-sensitive dyes, Ca 2+ indicators, intrinsic signal imaging and fMRI, have been used to image neural activity over dimensions ranging from individual synapses to large populations of neurons (Mao et al, 2001;Mrsic-Flogel et al, 2003;Grinvald and Hildesheim, 2004;Baker et al, 2005). However, the signals employed by these methods mainly rely on neuronal excitation.…”

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in <em>Aplysia californica</em>

“…The technique we have described compares favorably with other extracellular techniques such as multi-electrode arrays and voltage-sensitive dyes. The voltage-sensitive dye 29 technique is only used for recording, whereas our extracellular electrodes and multi-electrode arrays 30 can be used for both stimulation and recording. Both the multi-electrode array 29 and voltage-sensitive dyes 30 can record signals from many neurons simultaneously.…”

“…The voltage-sensitive dye 29 technique is only used for recording, whereas our extracellular electrodes and multi-electrode arrays 30 can be used for both stimulation and recording. Both the multi-electrode array 29 and voltage-sensitive dyes 30 can record signals from many neurons simultaneously. Although one single extracellular electrode may only record from one or two neurons depending on its tip size and the electrode location, it is certainly possible to position several on a ganglion simultaneously, and we have done this successfully.…”