RICERCA ITALIANA     

Estimation of brain functional connectivity with advanced methodological procedures

Università degli Studi di Bologna

Abstract

In recent years, the concept of brain connectivity is viewed as central for the understanding of the organized behavior of cortical regions. Various definitions of brain connectivity have been proposed: among the others, functional connectivity is defined as the temporal correlation between spatially remote neurophysiological events. This definition is data-driven and does not require additional knowledge of the neural circuits involved. Several algorithms have been proposed to evaluate functional connectivity from high resolution EEG. However, the comparative performances of these methods under different conditions of signal to noise ration (SNR) as well as other computational factors (such as the signal's length) have been not addressed adequately. Moreover, what kind of information on connectivity can actually be extracted from EEG without ambiguity is still insufficiently known.
The methods for the assessment of cortical connectivity could be usefully tested in simulations, by using both mathematical models or real cultured neuronal populations. Aim of this project is to develop, test and apply advanced methods for estimation of brain functional connectivity.
The project will be articulated in four main activities:
i) To develop and test alternative models of neural populations, for signal generation. In the first phase of the project, the parameters of the models will be assigned to simulate the power spectral density of cortical activity in some >>>

Principal Investigator

Mauro URSINO Università degli Studi di BOLOGNA

Research Objectives

From the considerations described in the "International Scientific Background" (see that section) it seems clear that some methods have been proposed in literature for the assessment of functional connectivity in humans. However, few simulation studies have partially explained the validity of these methods, leaving the other untested. Then, there is a need to appropriately test the principal linear and non linear methods for the assessment of cortical connectivity. However, the test can be adequately performed only in a simulation setup, and the simulation setup has to be as realistic as possible, to return information about the behavior of the methods in the real case. Realistic simulation setup means an adequate description of the dynamics of the neural population at the microscopic scale, then integrate such activity at a mesoscopic scale for the generation of macroactivity detectable by EEG electrodes. For these reasons, the project will involve specialists in both modeling of neural population dynamics (BOLOGNA and GENOVA units), specialists in the signal analysis processing (MILANO unit) and specialists in the propagation and application of advanced EEG processing tools with realistic head volume conductors (ROME unit). All these research groups will work together to achieve the main objective of the research project, that is to validate advanced methods for evaluation of functional connectivity, both with reference to scalp EEG signals, and populations of cultured >>>

Timescale

24 months

National and international background

Brain activity relies on the complementary principles of modular and distributed information processing. The cerebral functions can be investigated by identifying functionally specialized neuronal clusters and the relationships among them. The brain is a synergy of functionally interacting sub-systems, each dedicated to specific functions. The acknowledgement of this viewpoint implies that differences in brain activation among experimental conditions or groups of subjects may derive in general by different neuronal dynamics, either the neuronal activity or the network connectivity. In other words, similarly activated regions may produce different responses due to variations in their functional connectivity
Over the last decade, the development of non-invasive brain imaging methods based on hemodynamic (functional Magnetic Resonance Imaging, fMRI), or electro-magnetic (high resolution EEG; magnetoencephalography, MEG) measurements has been providing a great knowledge on the cerebral areas activation underlying motor and/or cognitive tasks in humans. Nowadays, a main issue remains open of how these regions communicated to each other. In this regards, the concept of brain connectivity is viewed as central for the understanding of the organized behavior of cortical regions beyond the simple mapping of their activity (Lee et al., 2003, Horwitz, 2003). Various definitions of brain connectivity have been proposed along these years: neuroanatomical, functional and effective >>>