Sweden

Presentation of research of Swedish representatives in COST project BM 0601, Advanced Methods For The Estimation Of Human Brain Activity And Connectivity (NEUROMATH)

 Dietrich von Rosen, Hans Liljenström, Björn Wahlund

Björn Wahlund has been working in the bio-statistical field since 1985. Dietrich von Rosen is trained mathematical statistician and Hans Liljenström is working within the field of biophysics. The cooperation between Björn Wahlund, Dietrich von Rosen and Hans Liljenström began around 1995.
 
 At that time we mostly worked with characterisation of affective disorders, using clinical and biological variables together with a fairly straightforward statistically treatment. Since year 2000 we have studied ictal EEG after brain stimulation with electroconvulsive therapy (ECT) of patients with severe forms of affective disorders. Last three years, we have worked with functional magnetic resonance imaging (fMRI) in affective disorders. We are especially interested in psychomotor function.

  As a part of a larger project, the aim of the EEG/ECT studies are to combine information from time series from many patients. The project intends to develop statistical/mathematical statistical/neuromodelling methodology in order to understand (individual) neurodynamics as well as to better understand why ECT is a powerful method among subgroups of affective disorders.

Mathematics

There are several challenging bio-mathematical/statistical problems linked to the analysis of the ictal EEG. The ECT treatment makes the series of observations non-stationary. The basic statistical concepts such as mean, variance and covariance are not obvious to identify. It is by far not obvious how to distinguish between a deterministic and a random part in these observations. Besides the problem of designing consistent experiments (which is more of administrative character and which has partly been solved) there is rather large subject variability in the response which is studied and which should be part of the model building. Indeed it is difficult to build models consisting of few parameters which fit data of the whole observation period and it we run into problems of high-dimensional analysis.  Concepts such as Kolmogorov-asymptotic, blocking of observations, the Marchenko-Pastur limiting distribution are all of interest.

Moreover, we try to understand relations between microscopic and macroscopic processes of neural systems. This involves investigations of the functional role and control of seemingly random events and processes at the cellular and sub-cellular level, and their relation to the complex, chaos-like dynamics of neuronal networks and systems. Mathematical analysis and computer modelling are used to interpret and understand experimental data.

Biological network modelling

We have studied the structure and dynamics of the EEG signal using neural networks and measures of complexity. We use computational methods of the neo-cortex to investigate how cortical neurodynamics depend on network properties and on intrinsic and external signals and fluctuations. We found similar dynamics in our mathematical models of post-ECT EEG data. Clinical data, however, show more complex patterns such as phase shifts between epileptic recruiting, slow-wave, poly-spike, etc. To simulate such pattern are going to include in our models effects of neuromodulation, intra-cortical connectivity modifications and connections to other cortical and subcortical structures.

Imaging methods

Another part of the research program is study the mirror neuron system in affective disorders using functional magnetic resonance imaging (fMRI). We study psychomotor changes in affective disorders by use of finger tapping and other specific research paradigm with fMRI. We are currently analysing the functional and effective connectivity of the functional network involving prefrontal, pre-motor, parietal, and anterior cingulum cortex.

Research groups SLU

Leaders: Hans Liljenström, Dietrich von Rosen

Two post doctoral students, one researcher, and 8 Ph. D. students

Furthermore, Hans Liljenström is the director of AGORA for bio systems: An international centre for dialogue between experimenters and theorists. The Agora for Biosystems is intended to provide a creative environment for interaction between theorists and experimenters in the biological sciences and related fields of research. This primarily includes multidisciplinary research, but also conferences, seminars, graduate courses, and summer schools in the interface of biology, medicine, physics, computer science, and theory of science. The purpose is to promote and advance the scientific knowledge and
understanding of the interconnected systems of organisms and their environment. A further aim is to create a platform for dialogues between science and the humanities. The Agora for Biosystems is under the auspices of the Royal Swedish Academy of Sciences.

Research group KI

Leader: Björn Wahlund (BW)

One researcher, three Ph.D. students

Furthermore, BW is a leader for the Swedish/Norwegian network of ECT. ECT-data (EEG, ECG and other physiological data) is currently sampled from 15 hospitals in Sweden and Norway and storage in a common data base. The network is linked to Nordic Association for Convulsive Therapy (NACT).