What’s in an activation? Insights from combining fMRI with electrophysiology
|Date||26 February 2016|
|Time||16:00 - 17:00|
BOLD-fMRI has become one of the most used techniques in cognitive neuroscience over the past two decades. We typically interpret the BOLD signal as reflecting an underlying neural process called ‘activity’ and differences between conditions are called an ‘activation’. The neurophysiological processes that actually underlie these activity and activations usually remain rather vague. Electrophysiological signals, like those recorded non-invasively with EEG or MEG, or invasively with ECoG or LFP recordings demonstrate a more and richer account of the neural activity. Where the BOLD signal only reflects a global measure ‘activity’, a wide variety of features can be measured with electrophysiological measures like spiking activity, frequency specific changes in synchronization and stimulus evoked phase locked activity. I will explore how linking electrophysiology to the BOLD could inform us about what kind of neural processes underlie the activity we measure with fMRI and can help us interpret the results we observe. Among the studies I will discuss is our latest work on how frequency specific changes in electrophysiology relate to cortical layer specific changes in activity measured by fMRI. Previously we demonstrated that the neural processes underlying alpha, beta and gamma power measured by EEG independently contribute to the BOLD signal. In this work we were able to demonstrate by combining high resolution fMRI with simultaneously recorded EEG that these different frequency bands are related to BOLD activity in different cortical layers.