June 5, 2009

Seeing your brain anatomy without fMRI scan

Migraine sufferer literally sees his brain surface being curved
In the article entitled "Migraine Aura: Retracting Particle-Like Waves in Weakly Susceptible Cortex", published in the open-access journal PLoS ONE, my colleague, Nouchine Hadjikhani, and I uncovered in a rather unconventional manner the spatial form and temporal evolution of pathological activity patterns in human cortex during migraine with aura. We compared symptom reports of visual field defects with the topographic representation of these symptoms on the cortical surface obtained by non-invasive functional magnetic resonance imaging (fMRI).

Migraine maps and other maps

A keen engineer provided us with fascinating data. He marked the progression of his visual disturbances with a pencil on a sheet of paper. For about half an hour, every minute he newly outlined the location of his visual field disturbance while keeping his gaze fixed on a cross that he had drawn on the paper when the attack started. So we got many drawings, he called them migraine aura maps, each with about thirty lines.

Nouchine recorded then another map from his cortical surface—called retinotopy—using fMRI. In this map, positions in visual field are marked on the cortical surface, for example with a color code ranging from cyan (lower hemimeridian, 6 o'clock position) via blue (horizontal hemimeridian, that would be 3 o'clock) to red (upper hemimeridian, you got it). Let us first use this color code in the picture above, voilĂ .

What you see below is a 3D picture of the primary visual cortex with the same color code as used for azimuthal positions in the visual field.

The primary visual cortex is a credit card-size large area in the brain receiving visual information from the eyes. The cross with the 4 letters c,r,d,v mark anatomical directions and cuneus, lingual gyrus, CS, and occitipal pole are just names for anatomical landmarks known to the specialist. Important is that the primary visual cortex is organized retinotopic, that is, neighboring points in the cortex process information from neighboring points in the visual field. Without retinotopic organization, the picture would be not smoothly colored but randomly.

This retinotopic mapping allowed me to reconstruct the spatial patterns that correspond on the cortical surface to the engineer's lines in the aura map. I compared the aura map with his typical anatomical landmarks and we uncovered that the engineer actually saw his curved brain from within because there where remarkable correlations between his aura map drawing and the curved shape of his primary visual cortex.

Towards novel therapeutic methods using chaos control

These patterns revealed valuable information about the self-organization principles behind migraine pathophysiology. The gained knowledge, namely the confined location of the activity, opens up entirely new therapeutic methods based on chaos control. I work currently on intelligent neuronavigated transcraniel stimulation techniques that can be used in combination with biofeedback training via a brain-computer interface to persistently decrease susceptibility to this pathological activity in exactly the right location. My hope is that location is the key to non-pharmaceutical medical therapies using biomedically engineered approaches.

Suggested further reading:
Chaos and Migraine.

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