So many interesting ideas have come from the investigation of the pre-frontal cortex that the rest of the brain is almost neglected. But maybe it was the enthusiasm for lobotomies, which shoved a knife through the eyehole in order to destroy that pre-frontal cortex with devastating and inhuman consequences, that kept researchers from looking at those other parts. The fact that the two halves of the brain could be separated by severing the corpus callosum, a band of tisssue that connected them, was kept quiet, though it was a surgery sometimes used in desperation to treat uncontrollable and life-threatening epilepsy.
Then it was realized that there was a cohort of the people who had separated brain hemispheres and that they could be studied to understand what difference it made. The people seemed to be functioning well-enough, but the main discovery was that their two half-brains became two people or rather two aspects of the person. Our culture so dearly loves binaries! More carefully designed experiments revealed that the right side, connected crossover-style to the left hand, had a different “style” from the opposite side of the X — left side to the right hand. Somehow involving “handedness” and literacy, the right brain was artistic, based on image, while the other side was logical, fact-based. Immediately the people who want to explain everything in gender binaries decided the artistic side was “female” and the rational side was “male.”
The more scientific folks were still pondering “fabulation.” The two hemispheres, when presented separately with different input, would construct fabulous little conflations that accounted for both sides. These stories were like those of early dementia sufferers who encountered things they could not reconcile without inventing a cover story. This research by now is extensive and fascinating (look for “split brain studies”), but it has distracted from getting down to the actual organic and discernible operation of the corpus callusom. What does it DO?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3163989/ is technical, official, and uses acronyms. Like all the other names based solely on observation, the parts of what seems a whole have Latin names based on shape: “spenium” is the thicker part (it means “bandage”) and “genu” is a part that looks a bit like a knee. (I recommend Google. My medical dictionary was soon outdated.) The areas form and elaborate at different rates, beginning right after birth and continuing into adulthood.
“By 11 years, both the anterior and posterior callosum have reached 90% of their maximum fiber directionality, and by 20 years they have 90% of their maximum external axonal structures “ (Harumph!) In short, these connections are still developing in the years a person (esp. a boy) are most exposed to damage from sports or abuse.
“There is evidence that callosal microstructure correlates with cognitive test performance in adolescents (ages 16–18 years). Specifically, FA in the body of the callosum (∼middle third) correlated positively with copy accuracy of a complex figure. FA in the splenium was positively correlated with processing speed, expressive vocabulary and single-word reading. Regression analyses confirmed that visuospatial performance was associated with FA in the body of the CC, whereas language performance (expressive vocabulary and single-word reading) was associated with FA in the splenium (Fryer et al. 2008).”
FA does not stand for “fuck all” but rather for “Diffusion tensor fractional anisotropy of the normal-appearing seven segments of the corpus callosum in healthy adults and relapsing-remitting multiple sclerosis patients.” https://www.ncbi.nlm.nih.gov/pubmed/15906348
Problems of this kind are called AgCC, meaning “agenesis of the corpus callosum” (It also stands for Abundant Grace Community Church.) Here’s the bottom line, which is a whole paragraph.
“Taken together, the neuropsychological findings in Primary AgCC highlight a pattern of deficits in problem solving, processing speed, and the social pragmatics of language and communication, which may result in significant complications of daily life. Parents report that children with AgCC and intact early motor development (i.e., sitting and walking within normal age range) are significantly likely to display clinically relevant behavior problems by the 6- to 11-year-old age range (Badaruddin et al. 2007). These include exhibit somatic complaints, attention problems, aggressive behavior, social problems and thought problems. The frequency of psychiatric diagnoses in AgCC is unknown, however diagnosis of learning disabilities, developmental delays and/or psychiatric disorders appear to be common (Brown and Paul, unpublished observations). The social impairments in AgCC are remarkably similar to those seen on the autism spectrum. In a sample of sixty-one 2- to 11-year-old children with AgCC, 34% of the sample met criteria for at least one item in the social interaction domain (with maximum of 46% who had impaired peer relationships). In the communication domain, at least 30% met on one item (with a maximum of 51 who had difficulty sustaining conversation).”
This subtly organic brain structure problem, whether developmental or caused by trauma, can be interpreted as being stupid, deficient and balky, thus adding more of a burden on a youngster who is by definition perhaps unable even to understand his problem, much less what to do about it. And the adults around him or her are probably not much better equipped. Their response can be an attempt to control behavior by punishment, maybe violent.
The following material is from “Medpage” and was written by Kristin Jenkins (pub. 3-17-17). Mercifully, she provides the origin of the acronyms.
“ A new biomarker that shows promise as a predictor of outcomes in children who sustain moderate to severe traumatic brain injury (msTBI) may help identify which youngsters could benefit from more aggressive treatment.
Note that the study found that early measures of interhemispheric transfer time (IHTT), the time required for signals to traverse the cerebral hemispheres through the corpus callosum, can predict which children will recover after msTBI and which will continue to decline neurologically and cognitively more than a year following injury.”
“The Recovery After Pediatric Brain Injury Study (RAPBI) demonstrates that early measures of interhemispheric transfer time (IHTT) can predict which children will recover after msTBI and which will continue to decline neurologically and cognitively more than a year following injury. . .”
“Demyelination of white matter is commonly found post-TBI and can have adverse cognitive repercussions, the researchers noted. This gets compounded in the maturing brain, since "myelination continues well beyond age 30.”
Myelin is the white insulation that protects individual neuron axons. If it is missing or too thin, the result is short-circuits and failure to transmit, just like a household extension cord. If I were an artist, I’d draw a brain in two halves with a corpus callosum throwing off sparks, maybe starting fires.