Transcranial electrical stimulation (TES) induced synaptic plasticity in freely moving rats

Abstract

5 - 800 million people suffer from neurological or psychiatric disorders. Sadly, a significant portion of these patients don’t respond to medications, leaving them with treatment-resistant disorders. Furthermore, the number of new drugs being developed for psychiatric disorders is limited, as some big pharmaceutical companies have shifted their focus away from neuroscience research.

To address these challenges,non-pharmacological techniques have been developed, including deep brain stimulation (DBS) and transcranial electrical stimulation (tDCS). While DBS has shown success, it’s invasive, prompting researchers to explore non-invasive options like tDCS. This technique is appealing due to its simplicity and low cost. The effects of tDCS depend on the location of stimulation electrodes and the orientation of neurons relative to the electric field. These factors influence whether tDCS leads to neuron depolarization or hyperpolarization. By understanding these mechanisms, we can tailor tDCS for different conditions and brain regions. During tDCS, neurons experience subthreshold membrane polarization, which can lead to earlier action potentials. The intriguing part is that these effects can persist for minutes or even hours after the stimulation is turned off, known as long-lasting effects of tDCS. Animal studies have shed light on various cellular mechanisms involved in tDCS-induced neuroplasticity, including changes in firing rate, long-term potentiation, NMDA receptors, BDNF, and more.

To translate these findings to humans, we need to understand the electric fields generated in the brain during tDCS. To measure electric fields in rodents, I used a neuropixels probe and recorded from hippocampus and visual cortex simultaneously. My preliminary experiments showed that tDCS induced changes in neuronal firing rates that lasted for at least 50 minutes. The effects were more pronounced in the hippocampus, which is better aligned with the induced electric fields.

Overall, this research provides insight into tDCS’s potential to induce neuroplasticity and its effects on different brain regions. By optimizing stimulation protocols, we can explore state-dependent changes and better understand tDCS’s applications in human neuroplasticity.

Mihály Vöröslakos

Postdoctoral Researcher

My research interests include translational neuroscience, non-invasive brain stimulation and neuroscience tool development.