One of the most distinctive physical features of the human brain is the fact that the cortex is divided into two hemispheres. The main connection between the two halves is a thick bundle of fibers called the corpus callosum. This is no quiet lane, it’s a major freeway constituting around 200 million neural tracts.
In an increasingly rare procedure, the callosum is sliced as a radical treatment for epilepsy. People who receive this treatment are referred to colloquially as split-brain patients and lab tests reveal profound effects on their mental functioning. In many ways, it’s as if the surgery leaves their mind divided in two.
A new paper reports on an elderly gentleman, referred to as H.W., who aged 88 presented at a clinic complaining of recent intermittent problems controlling his left hand and some mild memory difficulties. Preliminary tests found him to be high functioning. He scored 30 out of 30 on the “mini mental state examination”, which is used to pick up signs of dementia or confusion. But when the researchers – a team led by Natalie Brescian – scanned H.W.’s brain, they made a surprising discovery. He had no corpus callosum. The main channel between his two brain hemispheres was completely missing. More.
Apparently, the brain adapts best to this injury when it is early. In the case, the guy was created with it.
The article goes on to note that the actual damage from the severing of the two halves (an older form of epilepsy treatment) was often apparent only in lab tests, not in normal life with friends and family.
So another lecture hall neuroscience myth bites the dust.
Note: Such anomalies may be more common than we realize. The thing is, there weren’t easy means of discovery in the past, and even today, no one is usually looking for them. This guy only came to attention when he showed up, very late in life, complaining about minor neuro problems.
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