Abstract
Electrical recording permits direct readout of neural activity but offers limited ability to correlate it to the network topography. On the other hand, optical imaging reveals the architecture of neural circuits, but relies on bulky optics and fluorescent reporters whose signals are attenuated by the brain tissue. Here we introduce implantable devices to record brain activities based on the field effect, which can be further extended with capability of label-free electrophysiological mapping. Such devices reply on light-addressable potentiometric sensors (LAPS) coupled to polymer fibers with integrated electrodes and optical waveguide bundles. The LAPS utilizes the field effect to convert electrophysiological activity into regional carrier redistribution, and the neural activity is read out in a spatially resolved manner as a photocurrent induced by a modulated light beam. Spatially resolved photocurrent recordings were achieved by illuminating different pixels within the fiber bundles. These devices were applied to record local field potentials in the mouse hippocampus. In conjunction with the raster-scanning via the single modulated beam, this technology may enable fast label-free imaging of neural activity in deep brain regions.
Highlights
Systems neuroscience aims to correlate observed behaviors to underlying cellular and circuit dynamics
The chips were examined for their field-effect behavior, and as expected, light-addressable potentiometric sensors (LAPS) chips exhibited inversion, depletion, and accumulation regimes shown in the capacitance-voltage characteristic (Fig 2b)
To assess the sensitivity of LAPS to local charge, we examined their photocurrent behavior in response to pH changes (Fig 2c)
Summary
Systems neuroscience aims to correlate observed behaviors to underlying cellular and circuit dynamics. Electrophysiological recordings with miniaturized electrodes arrays capture neural dynamics at the single-neuron and population levels and correlate it to behavior [1,2,3]. By leveraging advances in complementary metal-oxide-semiconductor (CMOS) processing, neural probes can simultaneously record activity of hundreds of neurons [1, 3]. These probes do not reveal structural connectivity within the circuit. Optical imaging allows for direct visualization of large neuronal ensembles [4], and with the introduction of miniaturized endoscopes, its use can be extended from superficial cortical regions to deep.
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