Determining neuronal activity from fMRI signals – macroscopic and mesoscopic models

Abstract:  Functional MRI currently is the most popular non-invasive tool to investigate human brain function. It provides whole brain coverage, high spatial resolution (in the order of millimeter) and moderate temporal resolution (in the order of seconds). However, it assesses neuronal activity indirectly via changes in blood oxygenation. Thus, it is necessary to develop biophysical generative models covering the relationship between neuronal activity and measured fMRI data and use model inversion to determine excitatory and inhibitory neural activity.

In the first part of my talk, I will describe experiments and theoretical models, within the dynamic causal modeling framework, to investigate the hemodynamic response underlying the fMRI signal. These generative models have been employed both for single brain area deconvolution and to infer effective connectivity in networks of multiple brain areas. In the second part of my talk, I will describe extension of these macroscopic models for cortical-dependent fMRI (i.e. laminar fMRI). Laminar fMRI is an emerging field of human neuroimaging that seeks to localize neuronal activity within distinct layers of the cerebral cortex and to non-invasively investigate mesoscopic functional circuits in the human brain, a domain previously only accessed with invasive methods in animals and intraoperatively in humans. This opens new avenues for human cognitive neuroscience: We cannot only image the patch of cortex involved in a specific brain function but distinguish feedforward from feedback processing streams within this patch based on their respective cortical depth activity profiles. Finally, I will provide an overview of my research program at UHN.

Brief Bio: Kâmil Uludağ studied from 1992 till 1997 Physics at the Technical University of Berlin. He completed his Ph.D. in Physics in 2003 on Near-Infrared Optical Spectroscopy (Humboldt University, Berlin) and moved for a postdoc position to the Center for Functional MRI (UCSD, San Diego, USA) to work on the physiological and physical basis of functional MRI. In 2004, he was appointed Head of Human Brain Imaging group at the Max-Planck-Institute for Biological Cybernetics, Tübingen. From June 2010 to December 2018, he was Associate Professor in the Faculty of Psychology & Neuroscience and Head of the Department of Cognitive Neuroscience continuing his work on the basis of fMRI utilizing the new Ultra-High Field human MRI scanners (7 and 9.4 Tesla). Since May 2019, he is Full Professor at the Department of Medical Biophysics, University of Toronto.

See below for link to join via zoom:

Topic: KCN Event: Kamil Uludag

Time: Apr 29, 2021 10:00 Eastern Time (US and Canada)

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