National Geographic Channel will air “Brain Games: Brains Behaving Badly ” on Sunday, February 28 at 9pm EST. As part of a virtual roundtable, Brain Blogger was selected to screen the episode and address the thought provoking question raised therein:

Are humans hardwired for transgressions? Why are some of the brain’s most basic instincts considered bad behavior? Why does bad behavior come so naturally to us?

As a neurologist, when the brain goes haywire, I often witness the reversion of humankind to its primal self. The cortex of the human brain has evolved in such a way that it is often responsible for the differences between us and animals. Strokes, seizures, trauma, infection, and degeneration of certain brain structures are fascinating to encounter in that they induce certain transgressions. Here, I provide just two patient examples that I came across early in my neurology career.

Case 1: One my first “strange” cases as a neurology resident was an elderly woman who came to my clinic accompanied by her son who whispered to me to help her stop the “excessive humping” (pelvic thrusting is the medical description). We tested her for seizures and vitamin deficiencies to account for this behavior which were all normal. However, both of her temporal lobes lit up on her brain MRI and I immediately knew what she had — Kluver-Bucy Syndrome. Aside from indiscriminate hyper-sexuality, the full constellation of symptoms includes increased oral exploration, placidity, strong tendency to react to visual stimulus, and inability to recognize familiar objects. It was actually the herpes simplex virus that attacked both of her temporal lobes which was easily treated with some antiviral medications — with return of her normal prudent self.

Case 2: About mid-way through my training, a priest came into my neurology clinic with his wife complained that he would gamble all of the household funds at a casino nearly two hours away. The behavior escalated to the point where even the weekly church collections were gambled away — actions very uncharacteristic of this otherwise noble individual. In my office, I noticed that he had a tremor of right hand of pill-rolling quality. The rest of my neurological exam confirmed that in fact he had Parkinson’s disease. This and other disorders affecting the orbitofrontal cortex such as in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) can lead to pathologic gambling. Briefly, the orbitofrontal cortex represents a critical structure in a nervous system involved in decision making and processing rewards.

In short, our brains may have been very well hardwired for transgression, but evolutionary changes to certain neural structures, connections, and social behavioral constructs have halted their manifestation.

Keep thinking…

References

Bechara A, Damasio H, & Damasio AR (2000). Emotion, decision making and the orbitofrontal cortex. Cerebral cortex (New York, N.Y. : 1991), 10 (3), 295-307 PMID: 10731224

Poletti M, Lucetti C, Logi C, Baldacci F, Cipriani G, Nuti A, Borelli P, & Bonuccelli U (2013). Cognitive correlates of negative symptoms in behavioral variant frontotemporal dementia: implications for the frontal lobe syndrome. Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology, 34 (11), 1893-6 PMID: 23532547

Image via Fer Gregory / Shutterstock.