References

Achard, S, Salvador, R, Whitcher, B, Suckling, J, Bullmore, E (2006) A resilient, low-frequency, small-world human brain functional network with highly connected association cortical hubs. J Neurosci 26, 63-72 Albert, R, Jeong, H, Barabasi, A-L (2000) Error and attack tolerance of complex networks. Nature 406, 378-382 Albert, R, Barabasi, A-L (2002) Statistical mechanics of complex networks. Rev Mod Phys 74, 47-97 Amaral, LAN, Scala, A, Barthelemy, M, Stanley, HE (2000) Classes of small-world...

Diffusion Weighted Image Acquisition

The random motion of water molecules in biological tissues may cause the signal intensity to decrease in MRI. The NMR signal attenuation from molecular Fig. 1. Schematic representations of diffusion displacement distributions for the diffusion tensor. Ellipsoids (right) are used to represent diffusion displacements. The diffusion is highly anisotropic in fibrous tissues such as white matter (left). The direction of greatest diffusivity is generally assumed to be parallel to the local direction...

Phase Locking

An alternative to the classical coherence measure is to separate phase and amplitude information in the signals and analyze the phase locking or phase synchrony as a measure of connectivity between neural assemblies. Phase locking between two oscillators is defined as n,m(t) < const,pn,m(t) n 1(t) m 2(t), where n and m are integers and 1(t) and 2(t) are the instantaneous phases of the signals (Tass, et al., 1998). In order to compute any measure of phase synchrony, the instantaneous phase of...

Info

The model captures important features of the data. A, When the probability of occurrence is plotted against avalanche size, a nearly straight line is formed in a log-log graph. This line indicates that the relationship between probability and size can be described by a power law P(S) S-a, where P is the probability of observing an avalanche of size S, and S is the total number of electrodes activated in the avalanche. For a critical branching process, the exponent of the power law, a,...

Myelin Water Fraction

Although the specificity of T1 and T2 measurements are generally perceived as being poor, several investigators have recently shown that the T2 signal decay in neural tissue is multi-exponential with echo time (Menon and Allen 1991 MacKay et al. 1994 Whittall et al. 1997). Further investigation has shown that different water tissue compartments each have distinct T2 characteristics, and may be separated (see Fig. 24). In white matter, the water signal compartments are believed to originate from...

From Diffusion to Pathways White Matter Tractography

In addition to providing information about the mean diffusivity and anisotropy, diffusion imaging methods can also yield novel information about the orientation of local anisotropic tissue features such as bundles of white matter fascicles. In diffusion tensor imaging, the direction of the major eigenvector, ei, is generally assumed to be parallel to the direction of white matter. This directional information can be visualized by breaking down the major eigenvector into x, y and z components,...

Xt 4t t t

Typically is taken to be a constant, i.e., which is reasonable for most experimental systems. It should be noted that only solutions which are asymptotically stable can be accurately approximated using numerical integration. There are two main programs available for the numerical integration of delay differential equations. The widely-used (and free) package XPPAUT (Ermentrout, 2005) can perform numerical integration using a variety of fixed step numerical methods, including Runge-Kutta. It has...