Welcome to the iEEG and Brain Imaging Group Homepage!

This research group is affiliated to the Epilepsy Center, University Clinics Freiburg, and to the Bernstein Center of Computational Neuroscience (BCCN), University Freiburg

Intracranial EEG (iEEG) is an uniquely suitable method to capture local, synchronized activity of the human cerebral cortex . The aim of our research group is to characterize local cortical activity in humans based on intracranial EEG. By following this aim, we contribute to a better description and ultimately also to a better understanding of the function of the human cerebral cortex. In addition to studies based on iEEG alone, a special emphasize of our work is on the comparison of iEEG to and its integration with other neuroimaging methods, in particular with functional MRI (fMRI), including both meta-analyses and original fMRI studies. Furthermore, we are interested in the comparision of iEEG with conventional EEG non-invasively recorded from the scalp surface.

In terms of functinal systems, we are investigating the cortical motor system, the auditory and language systems, and brain regions involved in cognitive incuding emotional processing, such as the amygdala, the insular cortex, or the prefrontal cortex. Investigating these brain regions with iEEG and functional neuroimaging methods is however not only motivated by basic research questions, but also by the aim to contribute to the developement of important clinical / biomedical application. This includes the developement of new approaches for functional mapping of cortical functions for pre-neurosurgical evaluation (of motor and language functions) and the characterization of control signals for brain-machine interfaces (BMIs) for paralyzed patients (both motor and cognitive).

Recently published:

Towards a functional map of the human insula

One of the most mysterious regions of the human brain is the insular cortex, buried in the depth of the lateral fissure, which seperates the frontal and parietal lobes from the temporal lobe (Figure 2). Fro a long while, the insular cortex recieved little attention from neuroscience research. This has, recently, dramatically changed: an increasing number of recent studies addresses the functional role of the insular lobe. A number of reports have connected the insula to important high-level cognitive functions such as error detection, including social norm violation, general task monitoring, language processing, and also self-awareness and even consciousnes. Furthermore, the insula might play a crucial role in neuropsychiatric disorders, such as drug addiction (see for instance the recent New York Times article 'A small part of the brain and its profound effects'). Other studies have proposed more basic functions that might be supported by the insular cortex, including basic auditory processing, sensation of pain, smell, and taste, and simple motor funcitons.

Figure 2: Postion of the insular cortex in the human brain shown in red (modified from http://en.wikipedia.org/wiki/Insular_cortex). The parts of the frontal, parietal and temporal lobe that usually cover the insula are removed. The green line indicates the position of the central sulcus of the insula, which separates the larger anterior insular cortex (AIC) from the smaller posterior insular cortex (PIC).

There is, however, no functional map of the insular cortex available that might serve as a framework to investigate these various possible functions of the insular cortex in the human brain. As a basis for such a map, we have investigated which parts of the insula are found to be reproducibly activated by several different classes of experiments, namely experiments on auditory and language, experiments with voluntary motor tasks, and experiments tracking activity related to changes in peripheral autonomic functions such as heart rate. We find that destinct parts of the insular cortex showed reproducible responses to each of the three classes of experiments. Results for the auditory and hand motor experiments are shown in Figure 3 below. This functional differentiation is a first step towards a functional map of the human insular cortex, which we anticipate to become an important tool for future investigation of insular function and dysfunction in the human brain.

Figure 3: Functional mapping of the human insular cortex using a meta-analysis approach. Modified from Mutschler I, Wieckhorst B, Kowalevski S, Derix J, Wentlandt J, Schulze-Bonhage A, Ball T. Functional Organization of the Human Anterior Insular Cortex, Neuroscience Letters (2009). In (a), the region of the insular cortex (grey outline) with reproducible reponses during auditory processing and in language tasks is shown in red (color code an 'activation likelihood estimate'). In (b), the region with reproducible hand movement responses is shown.

Based on these findings, next steps of research will be to extent this map to further functional modalities and to validate the results with other techniques, in particular with intracranial EEG recordings and based on anatomical connectivity data. A further issue to be addressed is the specific function of the proposed insular motor area and its potential as a source of control signals for a brain-machine interface.