Electric field assisted patterning of neuronal networks for the study of brain functions

It is estimated that about 18 million people worldwide suffer from dementia and it is projected to increase to about 35 million by the year 2025. All types of dementia occur due to an aberration in memory retention and development, caused by malfunctioning neurons. Experimental investigation of the dynamics of neuronal networks is a fundamental step towards understanding how the nervous system works. Activity-dependant modification of synaptic strength is widely recognized as the cellular basis of learning, memory and developmental plasticity. Understanding memory formation and development thus translates to changes in the electrical activity of the neurons. To map the changes in the electrical activity, it is essential to conduct in vitro studies on individual neurons. Hence, there is an enormous need to develop novel ways for the assembly of highly controled neuronal networks. To this end, we used a 5 × 5 multiple microelectrode array system to spatially arrange neurons by applying a combination of DC and AC fields. We characterized the electric field distribution inside our test platform by using 2-dimensional finite element modeling (FEM) and determined the location of neurons over the electrode array as well as the expected direction of neurite growth. As the first stage in forming a neuronal network, dielectrophoretic AC fields were utilized to separate the neurons from the glial cells and to position the neurons over the electrodes. DC fields were then applied to induce directed neurite growth and achieve network formation. The neurons were obtained from 18 days old rat embryos from wild type Rattus Norvegicus. The technique of using a combination of DC and AC electric fields to achieve network formation has implications in neural engineering, elucidating a new and simpler method to develop and study neuronal networks as compared to conventional microelectrode array techniques.