In many ways, humans aren’t particularly special: we’re not that fast or strong, our bodies aren’t built to handle extreme environments, and we don’t have a hyper-specific niche to fill in our ecosystems. However, our conquest of the biological world around us has been possible because of our brains—massive, interconnected networks operating in sync to yield thought. Our overdeveloped frontal cortex provides the requisite structural complexity needed to enact many of the complicated behaviors and thoughts we experience. Brodmann area 9 (BA 9), a part of said frontal cortex, helps actualize many of the cognitive activities and actions that we associate with being human.
Despite playing a key role in higher-order thinking, this area isn’t readily apparent upon first glance. Its borders aren’t defined by visible hills (gyri) and valleys (sulci) on the brain surface, but rather by its cytoarchitecture, its cellular composition. Cortex is arranged in six layers, and BA 9 has a high density of granular cells in layer IV, which is why it’s sometimes called granular frontal area 9.
Areas 9 comprises part the dorsolateral prefrontal cortex, a region responsible for working memory, executive control, and emotional regulation. It is especially important in emotional intelligence and social cognition. Laughing at an inside joke, knowing when to not talk back to your boss, thinking about and setting goals, and other such important social skills are mediated by BA9. As with any part of the brain, area 9 doesn’t work alone. It has connections to many other cerebral regions, such as the temporal and parietal lobes, and the anterior cingulate cortex. The temporal lobe helps 9 with memory processing (especially in reference to the aforementioned social behaviors), and the cingulate cortex assists in more of that executive control dimension. Though we may love to think of ourselves as beings of higher reason, our thinking wouldn’t be possible without the myriad connections between all the different brain areas.
Damage to area 9 further highlights our reliance on biology. Lesions in the area can lead to frontal lobe syndrome, characterized by a smattering of behavioral and cognitive deficits in social behavior, abstract thinking, and motivation. If, after a head injury, someone’s personality changed, they started behaving in socially unacceptable ways, and they had no desire to do anything, they might have damaged Brodmann’s area 9.
The brain is a complicated organ, and that’s an understatement in and of itself. We’re still discovering new things about it every day, and we’re constantly surprised at what we find. Though it’s easy to think of humans as this uber-dominant species that’s very different from other, lesser, animals, Brodmann’s area 9 reminds us that we’re all subject to the same laws of nature. Our rich social lives and the many mental tasks we juggle daily are, at least in part, thanks to BA 9.
References
Hathaway, W. R., & Newton, B. W. (2023, May 29). Neuroanatomy, prefrontal cortex. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK499919/
Hertrich, I., Dietrich, S., Blum, C., & Ackermann, H. (2021). The Role of the Dorsolateral Prefrontal Cortex for Speech and Language Processing. Frontiers in human neuroscience, 15, 645209. https://doi.org/10.3389/fnhum.2021.645209
McHale, A., Cho, Y., & Fudge, J. (2021). Cortical granularity shapes information flow to the amygdala and its striatal targets in nonhuman primate. bioRxiv, 2021.05.06.442678. https://doi.org/10.1101/2021.05.06.442678
King Lab at Creighton University 