Connectivity Papers

Useful Papers - Connectivity


Lee et. al (2003), "A report of the functional connectivity workshop, Dusseldorf 2002," NeuroImage 19, 457-465 PDF

Summary: An excellent overview of the state of connectivity analyses today, with a survey of current methods, pitfalls, and open questions. Many terms are clearly defined. The overview looks not only at human neuroimaging techniques, but at a variety of anatomical techniques from various species.

Bottom line: Invaluable primer on the issues in connectivity.

Horwitz (2003), "The elusive concept of brain connectivity," NeuroImage 19, 466-470 PDF

Summary: A sort of minority opinion, to go with Lee et. al (above). Essentially a deeper primer on the pitfalls of studying connectivity, Horwitz raises questions about just how clear any of the term used in the field are at their core. In particular, he highlights the point that different neuroimaging techniques probably study very different types of connectivity, and their results may not be directly comparable.

Bottom line: Comparing connectivity across experimental techniques is necessary, yet done at your own risk...


Friston et. al (2003), "Dynamic causal modeling," NeuroImage 19, 1273-1302 PDF

Summary: The first introduction to the DCM concept, and necessary reading for the current state of connectivity research. The DCM framework essentially expands on the classic general linear model, adding in bilinear terms that attempt to model resting connectivity between regions and how experimental manipulations change that connectivity. Friston demonstrates how DCM encompasses a variety of other techniques (SEM, etc.) and explicitly includes the temporal dimension in assessing connectivity.

Bottom line: Well, it's big. And dense. But if you're at all interested in DCM, you should probably at least flip through it.

Mechelli et. al (2003), "A dynamic causal modeling study on category effects: bottom-up or top-down mediation," Journal of Cognitive Neuroscience 15, 925-934 PDF

Summary: A really interesting example of DCM use in a real-world setting. Authors used the dataset from another study, provided by the fMRI Data Center, and applied DCM to examine the connection between secondary visual areas and parietal regions. They discovered that category effects - differences in responses between chairs, faces, and houses - in occipital and temporal cortex are mediated by very early visual effects - not just top-down effects.

Bottom line: An excellent road map for a classic DCM analysis, and a useful handbook for those interested in trying it out.

Kondo et. al (2004), "Functional roles of the cingulo-frontal network in performance on working memory," NeuroImage 21, 2-14 PDF

Summary: A recent example of the SEM approach. Kondo et. al used SEM to model the connection between ACC and PFC in high-reading-span and low-reading-span groups, discovering a closer connection in the former than the latter. Some discussion of how SEM is carried out, as a guide for those wishing to try the method.

Bottom line: Nice example of how SEM works in a fairly complicated between-group study.

Goebel et. al (2003), "Investigating directed cortical interactions in time-resolved fMRI data using vector autoregressive modeling and Granger causality mapping," Magnetic Resonance Imaging 21, 1251-1261 PDF

Summary: Yet another approach to measuring connectivity, this time from the BrainVoyager group and attempting to impose some concept of directionality on the connectivity analyses. The concept of Granger causality - imported from economics - is described from a neuroimaging point of view. The VAR framework (a multivariate technique) is described and used to analyze a visuomotor mapping study.

Bottom line: Nice look at another type of connectivity work and the pitfalls of trying to impose directionality on it.