Casanova himself has used the tissue from the Harvard brain bank to test his hypothesis that autism is basically a wiring problem. The brains of people with autism, he thinks, are very good at forming short-range connections, but not as good at forming long circuits that integrate different parts of the brain. This may explain why people with autism have narrow areas of tremendous strength – say an ability to remember detailed train schedules, work complex mathematics calculations in their head, or create impressive works of art – but also global weaknesses, like language and social skills.
His work has led to clinical trials for a possible treatment for autism, using transcranial magnetic stimulation to change the levels of excitation in the brain. The hope is that the change will allow the brain to rewire itself, thus improving some of the negative symptoms.
When a donation arrives at a brain bank, investigators carefully slice it into sections. Roughly half the brain is preserved in formalin – an updated version of the smelly chemical used on dissection animals in science classes. The other half is thinly sliced and stored in a deep freezer at -80C to keep the chemical state of the brain cells intact.
Preserving and protecting each brain costs about £800 ($1,260), says Esiri.
Sometimes, the brain is scanned before being carved up. A technology called Diffusion Tensor Imaging can show the connections between one part of the brain and another. Some researchers also want other tissue – from the gut, blood, skin and teeth – which several of the banks have begun collecting as well.
As scientists request tissue, small samples are carved out of the brain and sent off. Most researchers can do their work with no more than 2 grams (0.07 ounces) of brain tissue – or just 100 mg to examine only the DNA – out of a total of about 1,200-1,300 grams in the average brain.
“The problem is it’s very difficult to isolate 100 mg of frozen tissue and keep it frozen,” says Ronald Zielke, director of The Eunice Kennedy Shriver National Institute of Child and Human Development Brain and Tissue Bank for Developmental Disorders at the University of Maryland. “In theory there’s a lot of tissue there, but that’s not necessarily the reality,” because researchers may want to focus on a specific and tiny area of the brain.
Zielke said his brain bank, which includes a wide range of developmental disorders, ships out about four samples a day, all year round. “We have over 860 researchers in 23 countries that have received tissue from us since 1991,” he says.
Each brain can be used by as many as 50 or 100 different researchers, he said, but it is not inexhaustible. New brains are needed all the time to keep up the supply, he said.
To be most useful to science, a brain has to be frozen within 24 hours of death. After that, the proteins in the brain start to degrade, though the structure – the relative size of different parts of the brain, for instance – may still prove useful.
This means reaching out to families at the worst possible time, when their loved ones have just died, a responsibility that often falls down to local medical examiners in US. “Medical examiners are absolutely critical for autism research,” says Zielke. “Without their support and participation, [efforts to get brain donations] will limp along.” His brain bank has received a grant from the Autism Research Institute, an advocacy group, to educate medical examiners about the need for brain donations and the proper procedures for ensuring that brains can be used for research. “The probability of any one individual dying is relatively low, thank goodness,” says Zielke, but every year, one or two people with autism die in just about every state. “If all medical examiners participated, there would be no shortage of autism tissue for research. In one or two years, we’d have enough,” he says.