Clinical Research Directory

Scaffolding of Brain Operations

Brain activity will be recorded while participants rest and/or perform perceptual discrimination tasks. These tasks include the presentation of sensory stimuli and require participants to detect and discriminate these stimuli, and to report about the objective properties of the stimuli as well as about their subjective perceptual experience using ratings of confidence, visibility, and/or alertness/sleepiness. All sensory stimuli used are neutral and consist of visual stimuli presented on a computer screen (either basic visual stimuli, e.g. an arrow, a grating or a dot, or neutral pictures of e.g. objects, buildings, landscapes), or auditory stimuli presented via headphones (either basic sounds, e.g. a beep or noise, or more complex sounds, e.g. a spoken word or rhythm). The experimental tasks may require participants to compare between sensory stimuli presented at different spatial locations or at different times, and/or to focus their attention on specific stimuli while suppressing distracting information; additionally, tasks may require participants to remember these stimuli for a delayed report. In these tasks, participants' performance will be quantified by motor responses (i.e., button press), reaction times and subjective ratings (confidence, visibility, alertness/sleepiness). Brain activity will be recorded by means of electroencephalography (EEG), a non-invasive technique consisting of electrodes placed along the scalp that record electrical field potentials generated by cortical neurons. EEG will be used to record brain activity prior to and in response to the sensory stimuli presented during the cognitive and perceptual tasks as well as during the participants' responses. Additionally, EEG may be used to record brain activity during a baseline resting state, while participants are not engaged in any particular tasks. In particular, the analysis of the EEG signal will focus on event-related brain activity (i.e., in response to the stimuli) such as event-related potentials (ERP), as well as ongoing and spontaneous and/or induced brain activity quantified as oscillations: wave-like signal fluctuations reflecting rhythmic variations of membrane potentials of cortical neurons. In addition, the investigators will use MRI to take an anatomical image of the brain to facilitate localizing the sources of the activity measured with EEG.