Integrating fMRI with complementary neurophysiological measurements can provide a more comprehensive understanding of brain function, and help to clarify the neural basis of BOLD fMRI signals. Here, we will discuss multi-modal imaging studies of the human brain using simultaneous EEG-fMRI, along with studies in animal models, which allow for more direct, invasive monitoring and manipulation of neural circuits. This talk will also briefly discuss technical challenges and methodology involved in acquiring and analyzing simultaneous fMRI-electrophysiological data.
Target Audience
Researchers interested in multi-modal brain imaging (such as simultaneous EEG-fMRI) and the neural basis of the BOLD fMRI signal.Educational Objectives
- Identify key benefits and challenges involved in combining fMRI with complementary measurements of neural activity
- Identify ways in which multi-modal imaging can help to elucidate the neural basis of BOLD fMRI signals
Overview
Functional MRI (fMRI) is a widely used, non-invasive technology for investigating human brain function, as it allows for whole-brain coverage and spatial resolution of millimeters and below. Yet, the blood-oxygen level dependent (BOLD) fMRI response is an indirect, hemodynamic indicator of brain activity, and inferences drawn from fMRI are limited by our incomplete understanding of the neural and physiological processes that influence fMRI signals. On the other hand, techniques that provide more direct measures of neural activity (such as EEG and invasive electrophysiology) can offer millisecond-scale temporal resolution, but are limited by either coarse spatial resolution or restricted spatial coverage. Here, we will discuss how integrating fMRI and electrophysiological signals can leverage the complementary strengths of these modalities, as well as help to clarify the neural basis of fMRI signals.
In humans, multi-modal imaging can be carried out noninvasively by recording scalp EEG concurrently with fMRI [1]. EEG and fMRI can be combined to examine cognitive processes [2] as well as spontaneous brain activity and resting-state networks [3-5]. As EEG provides established markers of brain state, simultaneous EEG-fMRI has been applied for studying state-dependent human brain activity and network connectivity; for example, across vigilance levels [6,7] and during sleep (e.g., reviewed in [8]).
In animal models, invasive recordings and manipulations of neural activity can more readily be performed. Measures such as single- and multi-unit activity, local field potentials, and astrocytic calcium signals can be recorded together with whole-brain fMRI to investigate neural circuits and to examine the neurophysiological basis of fMRI [9-12]. Further, targeted manipulation of neural activity can be combined with fMRI to examine brain-wide effects of specific perturbations (e.g. [13-15]).
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