Imaging of the Habenula in the Human Brain
The habenula is too small for standard fMRI. We used a series of tricks to make sure we could find the human habenula in a reward-disappointment experiment:
- Instead of collecting standard 3 x 3 x 4 mm voxels from whole brain, we used 2 x 2 x 2 voxels from just a slab of brain.
- We did not smooth the data, The habenula is against the ventricle, so smoothing would average two very different values.
- We manually co-registered each subject's functional and structural images, focusing on the habenula.
- From a small number of voxels that are in the right spot to be called habenula, we choose those that would anticorelate to putamen activity during reward (in monkeys, when the habenula activates, the striatum inactivates). Then, we used only those voxels to study activity during disappointing events.