Journal of Neuroscience Methods 87 (1999) 45 – 56 The neurochip: a new multielectrode device for stimulating and recording from cultured neurons Michael P. Maher a, *, Jerome Pine b , John Wright c , Yu-Chong Tai c a Diision of Biology, California Institute of Technology, Pasadena, CA 91125, USA b Diision of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA c Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA Received 27 March 1998; received in revised form 30 September 1998; accepted 1 October 1998 Abstract The neurochip is a silicon micromachined device upon which cultured mammalian neurons can be continuously and individually monitored and stimulated. The neurochip is based upon a 4 ×4 array of metal electrodes, each of which has a caged well structure designed to hold a single mature cell body while permitting normal outgrowth of neural processes. We demonstrate that this device is capable of maintaining cell survival, and that the electrodes can both record and stimulate electrical activity in individual cells with no crosstalk between channels. © 1999 Elsevier Science B.V. All rights reserved. 1. Introduction To study the dynamics of a functioning neural net- work, we wish to measure the electrical activity of all the cells in a small network of cultured neurons. Addi- tionally, non-invasive and specific stimulation of the neurons is required to simulate external inputs, to map the connections, and to study plasticity (changes in the connections between the neurons based on the activity patterns) over times of days or weeks. We have de- signed and built a silicon micromachined device called the neurochip (Wright et al., 1996; Maher et al., 1998) which satisfies these requirements. As a first step to- wards studying a full network, we demonstrate two- way, non-invasive communication between external electronics and individual neurons cultured in the neu- rochip. There have been previous demonstrations of related devices for use with individual peripheral mam- malian neurons (Pine, 1980), with invertebrate neurons (Regehr et al., 1989; Stett et al., 1997), and with mam- malian cell networks (Gross et al., 1977). The neu- rochip significantly improves on these methods by associating individual electrodes with the cell bodies of each of the neurons in a small network. We have chosen to work with rat hippocampal neurons for the following reasons. (1) Similar to most CNS neurons, these cells spontaneously form densely interconnected networks in vitro (Bartlett and Banker, 1984; Fletcher et al., 1991). (2) A vast literature base exists regarding their cell culture and physiology. (3) At 18 days gesta- tion (E18), nearly all of the cells in the rat hippocampus are excitatory pyramidal neurons which survive well in dissociated culture. Our goal is to have access to all individual neurons in a small cultured network. We briefly review currently used techniques, to evaluate their adaptability to this purpose and to motivate our neurochip design. Stan- dard electrophysiological techniques (sharp electrode and whole-cell patch recordings) involve making a con- nection to the interior of a cell by puncturing the cell membrane with a saline-filled glass pipette. With re- gards to the study of small-to-medium sized networks of neurons, the main problems with these methods are that (1) penetrating the cell can alter the cell’s proper- * Corresponding author. Present address: Institute for Non-Linear Science, University of California, San Diego, La Jolla, CA 92093- 0402, USA. 0165-0270/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII:S0165-0270(98)00156-3