Network Dynamics and Synchronous Activity in Cultured Cortical Neurons

Abstract

Neurons extracted from specific areas of the Central Nervous System (CNS), such as the hippocampus, the cortex and the spinal cord, can be cultured in vitro and coupled with a micro-electrode array (MEA) for months. After a few days, neurons connect each other with functionally active synapses, forming a random network and displaying spontaneous electrophysiological activity. In spite of their simplified level of organization, they represent an useful framework to study general information processing properties and specific basic learning mechanisms in the nervous system. These experimental preparations show patterns of collective rhythmic activity characterized by burst and spike firing. The patterns of electrophysiological activity may change as a consequence of external stimulation (i.e., chemical and/or electrical inputs) and by partly modifying the "randomness" of the network architecture (i.e., confining neuronal sub-populations in clusters with micro-machined barriers). In particular we investigated how the spontaneous rhythmic and synchronous activity can be modulated or drastically changed by focal electrical stimulation, pharmacological manipulation and network segregation. Our results show that burst firing and global synchronization can be enhanced or reduced; and that the degree of synchronous activity in the network can be characterized by simple parameters such as cross-correlation on burst events.

Light induced stimulation and delay of cardiac activity

“…Cell connectivity over the whole array can be seen in Fig.5c where AP events are plotted as a single point for all channels during twenty seconds of recording. It can be seen 10 that the sub-threshold stimulation test, where only depolarization was evoked, does not spread over the whole cell layer. Fig.5a shows the behavior of one segment of the array in detail.…”

“…For example, Pelloux et al study pacemaker free cultures. The optical control of confocal microscopy lasers would allow pulses of various intensities of light to be applied in a suppression regime interspersed with 10 optical measurements. Laser stimulation could conversely be used to activate model systems that do not normally produce reliable APs [46] whereas ChR2 gives the advantage of artifact free and reliable stimulation without permeabilization.…”

“…Multi-site analysis of tissue is one of the most common applications for MEAs in vitro. Application of MEAs to record heart tissue [8,9] as well as neuronal network 35 behavior [10,11] is commonly done in various types of in vitro and in vivo preparations. Advantages are the good spatial resolution in combination with a high temporal resolution.…”

“…Scar formation requires use of higher stimulation voltages, which may exceed the electrochemical window of the electrodes and are therefore not suitable. Of even greater concern is the fact that electrical stimulation can permeabilize 10 the cell. Electropermeabilization of the cells can trigger action potentials, but at the same time damages the cell, preventing the desired long term interfacing [26].…”

“…on and off calculated here for ChR2 kinetics are expected to vary from that reported in the literature due to the nature of the measurement. 10 Initial simulation of the on and off kinetics used giant membrane patches to estimate on of .2 ms and off of 20 ms [32]. More recent current clamp measurements of whole cells report on of ChR2 to be 55.5 ms while off is 9.8 ms [45].…”