We report on a novel method for two-dimensional electrical mapping of neuronal activity using a 1 mm2 array of 16384 sensor field-effect transistors fabricated by an extended CMOS (complementary metal oxide silicon) technology. The contact from neurons to chip is made by an insulating oxide on the chip surface that provides a purely capacitive drive of the sensor transistors. As a test system for multi-transistor-array (MTA) recording we use cultured neurons from the pond snail. We present electrical maps of an individual neuron and of a small neuronal network at a resolution of 7.8 µm. MTA recording provides a tool to image network dynamics of cultured nerve cells and brain slices for studies in neurobiology and biosensorics.
Multi-transistor-array (MTA) mapping of neuronal network activity. (a) Array of sensor transistors with twelve snail neurons cultured for 24 hours. The fluorescence micrograph of the marked area is shown on the left, neurons were stained with the dye DiI. The neurons I, II, III form a network joined by electrical synapses. (b) Records of three selected sensor transistors beneath neurons I, II and III. A burst of action potentials is elicited in neuron I by stimulation with an impaled micropipette. Postsynaptic neurons II and III are excited by coupling via electrical synapses. The arrows mark the time chosen for plotting the maps. (c) Electrical maps. Extracellular voltage on an area of 375 µm x 375 µm corresponding to the area marked in a). At time 102 ms, neuronal excitation is recorded in the region of neuron I. Later at time 111 ms electrical activity is localized in neuron II and at time 119 ms in neuron III. The time dependence of the voltage map for the whole measurement (508 ms) is shown as a supplementary time lapse video No. 2 online.
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