Brain Stimulation Projects

Slow Oscillations in EEG recordings are considered a hallmark of slow wave sleep (SWS), and SWS duration is highly correlated with physiological and cognitive processes: hippocampal memory and neural homeostasis. Although some studies during the last years have demonstrated that slow oscillations can be enhanced by different methods of brain stimulation such as Transcranial Magnetic Stimulation and Transcranial Direct Current stimulation, long term safety effects of these methods are not yet established. For this reason, recent studies have proposed that phase locked sensory stimulation could drive slow wave sleep, but the physiological and cognitive effects of this kind of stimulation have not been studied in detail.

The purpose of this project is therefore to study the physiological and cognitive correlates of sensory stimulation during SWS in humans. We develop new algorithms for on-line detection and stimulation of SO to study whether phase locked sensory stimulation is an effective method to enhance slow oscillations and to improve cognitive function related to specific components of declarative memory during sleep. Experiments are performed with healthy subjects to evaluate sleep dynamics, and on intra-cortical implanted epileptic patients to study cortical responses to auditory stimuli.

There are different neurodegenerative diseases associated with loss in memory or cognitive abilities. These diseases cause a decrease in life quality of patients. Currently, there is no way to stop or reverse the progression of these conditions and most of the treatments are based on pharmacological care. However, in the last decade several studies have shown that stimulation by unconventional methods could help to decrease the symptoms of different neurodegenerative diseases.

In particular, noninvasive electrical stimulation has been shown to be effective in improving memory retention. In turn, auditory stimulation during deep sleep has generated an increase in slow waves (SWS), which are associated with memory consolidation. It is believed that stimulating a hypersynchrony during sleep facilitates the process of neuronal homeostasis and plasticity, which promotes long-term memory consolidation. Despite electrical and acoustic stimulation during sleep have been shown to improve memory consolidation in young and elderly subjects, the successful implementation of these stimulation techniques is variable. It is believed that, in order to obtain more effective results, a stimulation must be carried out according to the natural cortical rhythms of the brain; A process that is not trivial because of its complexity. Our project is based on the development and validation of a system that allows non-invasive neurostimulation (electrical or auditory) during deep sleep periods, taking into account endogenous cortical activity in order to improve memory consolidation.