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Copy of Neural Networks
Transcript of Copy of Neural Networks
Google X Labs
Self driving vehicles
Augmented reality glasses
Space elevators Magnitude Squared Coherence
Imaginary Coherence What is FC? fMRI Measures of Connectivity Functional Connectivity (FC) Functional Connectivity functional MRI Electroencephalography EEG spatio-temporal BOLD correlations statistical dependency of neural oscillations How can we study brain activity? Activation Tasks Is it really inactive at rest? cat face Connectivity is clinically significant Neuroplasticity Can be done at REST! TMS as a tool to study and to modulate networks TMS protocols: reliable measure to analyze connectivity of the brain at rest Single pulse TMS
Paired pulse TMS
Repetitive TMS (rTMS)
Continuous TBS (cTBS)
Intermittent TBS (iTBS) Can we predict behavioral changes
induced by TMS? OBJECTIVES OF THE PROJECT THERAPY Why use TMS in patients? Resting State Networks (RSNs) Default Mode Network Neural Networks Neural Network Plasticity in the
Human Brain Thesis in Neuroscience
Lana RIZK Baseline? 'Resting Brain' It is NOT!!!
Functionally associated groups of regions
Reproducible at rest across subjects and recordings
Can be observed with fMRI, PET, EEG/MEG Thus, functional networks assessed with EEG can be an important source of information on the encoding of individual cognition and information processing means communication
between distinct regions Similar and Synchronous oscillations Activation studies Somatotopic shifts
Increased activity in distinct but connected regions
Increased activity in the contralateral hemisphere Mechanisms of Plasticity after a Damage Network Approach What do the observed changes in FC mean? Adaptive?
Can we deliberately modulate connectivity (with e.g. TMS)? Damoiseaux et al. (2006) Fox et al. (2005) To characterize changes in FC induced by lesions or by degeneration & to assess their behavioral (clinical) significance
To define how the electrophysiological networks correlate to the underlying behavioral dysfunction
To study the effects of TMS on functional brain networks and network plasticity induced by stimulation Raichle & Mintun, 2006 Fox et al. (2005) Brookes et al. (2011) Good spatial resolution, BUT: indirect measurement of neuronal activity Good temporal resolution
Assesses directly activity of the neural tissue
BUT: source localization problem fMRI EEG Source-based Functional Connectivity Varela, Nature (2011) Phase Synchronization Analysis Imaginary Coherence van den Heuvel et al. (2010) Van den Heuvel et al. (2010) Separating Synchrony from Volume Conduction When the volumes recorded by two electrodes overlap, the shared neuronal population creates spurious synchrony between the signals.
It is important to examine volume conduction and to correct for it by e.g. excluding synchronicity with zero phase difference. Interhemispheric connectivity in the somatosensory network predicts motor deficits. Carter et al. (2010) Interhemispheric connectivity in the dorsal attention network predicts attentional deficits. Functional Connectivity in Stroke Patients FC increase after combined TMS therapy in patients with stroke Gerloff et al. 2006