This doesn't look so complicated! What's the big deal??
It's the mappings of the frontal cortex of a monkey - you can see connections from the amygdala (emotional information like fear), hippocampus (memory encoding), sensory stimuli from the visual cortex, motor cortex, auditory, olfaction, etc.
The frontal cortex is where it's believe we make decisions - some believe it is the seat of our personality. The case of Phineas Gage is one of the oldest, most famous case studies involved with personality and its correlation to the frontal cortex.
Quick background: while working blasting rock (I believe for the railroad), he was responsible for planting explosives, but something went wrong, and while he was patting the gunpowder with an iron rod, he mistakenly caused an explosion, sending the rod through the side of his face, straight through his frontal lobes. He was barely even knocked out by the explosion, and was basically conscious the whole time. He did however start experiencing some "side effects."
A list of issues pertaining to his personality changes:
"Fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operations, which are no sooner arranged than they are abandoned in turn for others appearing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was 'no longer Gage.'"