A 3D reconstruction of the brain that made the biggest contribution to neuroscience will allow scientists to continue to get insights into the brain for years to come.
The brain of Henry Molaison (known to science until his death in 2008 as ‘Patient HM’), who was left with no short-term memory after surgery which cured him of epilepsy, has already improved our understanding of memory and will continue to do so for years to come.
He became one of the most famous people in neuroscience after he had several parts of his brain removed to cure him of his epilepsy in 1953. The amnesia which followed and his willingness to be tested helped give valuable insights into where memories are formed and stored in the brain.
When he died in 2008, his true identity was revealed to the world. He donated his brain to science after suffering respiratory failure. This lead to Jacopo Annese at the Brain Observatory in San Diego, California, being able to link memory problems to specific areas of Molaison’s damaged brain.
When Henry Molaison was a child, he had major epileptic seizures. He ended up seeking help from William Scoville at Hartford Hospital in Connecticut after anti-epileptic drugs failed to help with his condition. Scoville operated on Molaison (at the age of 27 years old) and removed portions of his brain. This included his medial temporal lobes, which contains an area called the hippocampus.
This lead to Molaison not being able to form any new memories (this is known as anterograde amnesia). Molaison also had some difficulty recalling past events (partial retrograde amnesia). The operation did however lead to Molaison’s epilepsy becoming manageable, despite the other effects on his brain. More information about ‘procedural memory’ was also gained. Molaison could learn new skills despite not remembering doing them before. This provided evidence that procedural memory was located outside of the hippocampi.
This helped scientists understand more about the brain and how it works. When the operation was performed, it was commonly believed that memory was stored throughout the brain. This was the initial indicator that memory was confined to certain areas, such as the hippocampi and areas around it (which were removed from Henry Molaison’s brain).
There were also some other issues apart from memory resulting from the surgery. Molaison lacked the ability to report internal states. This meant that he could not feel pain or tell whether he needed to eat or drink. This was because his entorhinal cortex was removed, which prevented the areas of the hippocampi that remained from functioning properly.
It was understood that only a dissection would tell us of his full injury, as scans taken between 1984 and 1993 were not of a high enough resolution in order to reveal everything. When he died in 2008, his brain was donated to science. It was frozen and cut into 2401 slices making up his brain, and these slices were only 70 micrometres thick. Pictures were taken of each slice in high resolution and took three days in total to complete. These images were used to create a very detailed 3D model which other researchers could view virtually (information about this can be found on thebrainobservatory.org). It was revealed that there was a lesion in the frontal lobes which had not been previously known. The individual slices were also preserved for any future use.
Molaison has been the most studied patient in the history of neuroscience, and the digital images and slices of his brain will provide new opportunities for neuroscience to benefit from him long after his death. The virtual 3D reconstruction and the post-mortem examination of his brain have been published and will now lead to further advances in our knowledge of the brain.