Brainmap: Laura Lewis, PhD- Using fast fMRI acquisition to make new inferences about neural dynamics

Abstract

Many aspects of high-level cognition take place on a timescale of hundreds of milliseconds, and measuring neural activity in this frequency range is important for cognitive neuroscience. However, current non-invasive neuroimaging methods are not able to precisely localize oscillatory neural activity above 0.2 Hz. While fMRI has excellent spatial resolution, it has typically been limited to measuring slow timescale activity, as the hemodynamic response is generally thought to be sluggish. I will present evidence that fast fMRI acquisition enables the direct detection of neural oscillations with frequencies of up to at least 0.75 Hz within single scan sessions. The amplitude of these oscillatory responses is an order of magnitude larger than predicted by canonical linear models, suggesting that the hemodynamic response can be surprisingly fast during ongoing neural activity. I will then present preliminary results demonstrating an application of this approach to localizing neural activity during slow wave sleep using simultaneous EEG-fMRI. Our results suggest that fMRI can be used to localize 0.1–0.75 Hz oscillations in the human brain, and identify new aspects of neurovascular dynamics to take into account when using fast fMRI methods.

About the Speaker

Laura Lewis completed her Ph.D. in Neuroscience at MIT, where she used intracranial electrocorticography in humans and optogenetic techniques in mice to identify neural circuit mechanisms of sleep and anesthesia. She then moved to Harvard University and Massachusetts General Hospital to develop new fMRI and EEG approaches to mapping neural dynamics during sleep and wake states. She was appointed as a Junior Fellow in the Harvard Society of Fellows in 2014, and was named a Kavli Fellow of the National Academy of Sciences in 2015.