Modality Description

The 6-week Summer Workshop

Team projects will be performed under the guidance of a modality faculty and teaching assistant. Each team will consist of 2 - 4 trainees, and learn in-depth training of only one imaging modality (See example in the Participants section). At the end of the 6-week program, each team will present their learning project at the External Advisory Board meeting. It is expected that trainees will learn the basic concepts and limitations of neuroimaging modalities, practical issues and data processing of one imaging modality, and interpretation of their findings.

Specific Project-based training plan of the five neuroimaging methods

Diffusion tensor imaging (DTI). DTI measures the anisotropic diffusion of water in axonal fibers of the brain, using magnetic resonance imaging (MRI) with diffusion gradients. The fiber directions and fractional anisotropy can be used to trace fibers, producing a structural connectivity map of brain regions. In the DTI module, trainees will learn the basic theory of DTI and tractography, followed by a practice with MRI data of human brain (both new acquisitions and existing data) using Explore DTI software. In addition, a localizer fMRI will be used to correlate functional foci with the structural connectivity measured by DTI.

Functional MRI. fMRI indirectly measures cortical neural activity with millimeter spatial and second temporal resolution in humans and animals. Its core strengths are based on its accurate localization, high signal to noise ratio, repeated use and non-invasiveness. Our laboratory training will cover design of experimental paradigms, collection and analysis of fMRI data, and interpretation of functional images. Each team will select stimuli from well-characterized paradigms such as the Stroop or n-back task. Since fMRI measures hemodynamic responses induced by neural activity, potential pitfalls and limitations will extensively be discussed. Specifically, it is expected that trainees will learn the fundamentals of experimental design , data acquisition, data preprocessing, single subject analysis using a general linear model approach, and group analyses using analysis of variance and t-tests. Students should be familiar with basic neuroanatomy, E-Prime software, and the UNIX and/or Linux operating systems before they participate in the workshop.

Positron Emission Tomography (PET). PET is a nuclear medicine imaging modality that is used to measure the in vivo distribution of substances that are labeled with a positron emitting radioactive isotope for detecting blood flow, glucose metabolism, oxygen consumption, and drug-binding interactions. While regulations governing the exposure of human and animal subjects to ionizing radiation will prohibit trainees from designing and conducting their own research experiments, students will be able to observe and participate in current investigator sponsored research as well as designated training exercises. Training emphasis will be on modeling and data analysis.

Magnetoencephalography-electroencephalography (MEG-EEG). While EEG measures electric potential differences on the scalp generated by cortical synaptic activity, MEG measures induced magnetic fields generated by synchronized synaptic activity. EEG measures current sources oriented in both radial and tangential directions, with a presumed main contribution of radial sources, while MEG predominantly or exclusively detects tangential sources (from the fissures). These two techniques together provide more accurate information about underlying ionic currents. In this MEG-EEG modality, we will focus training on principles, data processing and applications to neuroscience, covering experimental paradigm design, data collection and analysis, and interpretation.

Functional Near-infrared Spectroscopy (fNIRS). FNIRS is a non-invasive brain imaging technology which uses low levels of non-ionizing red and near-infrared light to measure changes in the optical absorption and scattering of tissue. This light can be used to measure changes in the outer 5-8 mm of the cortex of the brain which allows recording during many cognitive, sensory, and movement tasks. FNIRS methods have particular utility in the study of brain activity in children and during tasks involving movement, since fNIRS instruments are smaller and more portable compared to many other imaging modalities. We will focus training on the basic principles of the fNIRS method and instrumentation, data processing, and interpretation. Students will be exposed to several types of fNIRS instruments including continuous wave, frequency-domain, and diffuse correlation spectroscopy.

Optical imaging methods (only for animal research). Recent advances in optical imaging technology have enabled unprecedented visualization of the dynamics of neural structure and function. In vivo and in vitro two-photon imaging using laser scanning microscopy makes it possible to resolve individual neurons, dendrites and capillaries, and to study in vivo physiological responses to stimuli at the level of individual neurons and capillaries. For wider field views of the functional organization of the brain areas, macroscope imaging systems coupled to CCD cameras can be used to reveal detailed functional organization by making use of "intrinsic signal". In the optical imaging module, laboratory projects will be either two-photon laser scanning microscopy or intrinsic optical imaging of animal brains, depending on trainees' interests.