Brain fixation is critical to study the brain ex vivo (meaning, outside a living body). If a brain sample is not fixated soon after death, it deteriorates quickly due to the blood supply. After the fixation, the brain can be preserved for a long time.
|Dr. Insausti, holding a fixed human brain|
Dr. Insausti is also going to carry the histological study. Such study consists of two different phases: slicing the brain, and staining the slices. In order to slice the brain (or in our case, a block of tissue around the thalamus) into very thin sections, one first freezes the sample with dry ice and then sections it with a machine called "microtome". As opposed to thicker blocks of tissue, these thin slices can be examined under the microscope.
Rather than looking at the slices directly, one enriches their contrast first through a staining process. Different types of stains and dyes can be used to enhance different properties of the tissue. The most popular technique is arguably Nissl staining, invented by Franz Nissl in the late 19th century. After staining, the samples are mounted on slides that protect them, and can then be examined with a microscope.
|Nissl-stained slice of human thalamus|
|Looking at mounted slides with samples of a human hippocampus|