Brain Changes in EEG and Brain Pulsatility to Novel Stimuli (Electro-PulCe)

Overview

The oddball paradigm is one of the most widely used methods of brain exploration for the study of attentional processes. It allows the measurement, by means of an Electro-Enchephalogram (EEG), of evoked potentials reflecting the electrophysiological reactivity to the detection of novel stimuli within a stream of standard stimuli. Other studies have recently suggested that, in addition to neuronal activation, certain other physiological processes related to cerebrovascular reactivity, such as the Brain Tissue Pulsatility (BTP), could also be sensitive to various cognitive processes and in particular to attentional processes. In one of the latest studies published in collaboration with our group, it was shown that the amplitude of the electrophysiological response classically associated with attentional activity (P300 wave) was significantly correlated with the amplitude of BTP, suggesting the involvement of cerebrovascular processes in attentional functions. Nevertheless, in this study, the two methods of EEG and Tissue Pulsatility Imaging (TPI) were not synchronized, since TPI was performed at rest and not during the oddball task itself, and to date no study has sought to couple the methods of EEG and ultrasound TPI in an oddball paradigm, for a simultaneous characterization of neuronal and cerebrovascular responsiveness during attentional processes. The general objective of this study will be to evaluate changes in BTP during the detection of novel stimuli in an oddball task in healthy volunteers, in which the two methods of TPI and EEG will be coupled and synchronized.

The oddball paradigm is one of the most widely used methods of brain exploration for the study of attentional processes. It allows the measurement, by means of an Electro-Enchephalogram (EEG), of evoked potentials reflecting the electrophysiological reactivity to the detection of novel stimuli within a stream of standard stimuli. Numerous studies have thus used the oddball paradigm to identify the neuronal reactivity involved in attentional orientation towards target stimuli. Other studies have recently suggested that, in addition to neuronal activation, certain other physiological processes related to cerebrovascular reactivity, such as the Brain Tissue Pulsatility (BTP), could also be sensitive to various cognitive processes and in particular to attentional processes. Ultrasound measurement of BTP is made possible by recent advances in both the development of ultrasound equipment and ultrasound signal processing. Our team and others have validated the measurement of BTP by ultrasound (Tissue Pulsatility Imaging - TPI) in healthy volunteers and clinical populations, and our results suggest that the mechanisms of BTP are significantly influenced by cerebrovascular physiology. In one of the latest studies published in collaboration with our group, it was shown that the amplitude of the electrophysiological response classically associated with attentional activity (P300 wave) was significantly correlated with the amplitude of BTP, suggesting the involvement of cerebrovascular processes in attentional functions. Nevertheless, in this study, the two methods of EEG and TPI were not synchronized, since TPI was performed at rest and not during the oddball task itself, and to date no study has sought to couple the methods of EEG and ultrasound TPI in an oddball paradigm, for a simultaneous characterization of neuronal and cerebrovascular responsiveness during attentional processes. The general objective of this study will be to evaluate changes in BTP during the detection of novel stimuli in an oddball task in healthy volunteers, in which the two methods of TPI and EEG will be coupled and synchronized.