Short answers, pulled from the story.
The brain is the organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It receives information from the sensory nervous system, processes it as thought, cognition, and intelligence, and coordinates motor control and the endocrine system. It is typically located in the head, near organs for vision, hearing, and smell.
In humans, the cerebral cortex contains approximately 14 to 16 billion neurons, and the cerebellum holds an estimated 55 to 70 billion neurons. The human brain has been estimated to contain approximately 100 trillion synapses, while even a fruit fly's brain contains several million.
All vertebrate brains can be embryonically divided into the forebrain or prosencephalon, the midbrain or mesencephalon, and the hindbrain or rhombencephalon. The forebrain subdivides into the telencephalon and diencephalon, and the hindbrain into the metencephalon and myelencephalon. These appear first as three roughly equal vesicular swellings at the front of the neural tube.
Humans have an average encephalization quotient in the 7-to-8 range, while most other primates fall between 2 and 3. Dolphins score higher than non-human primates at around 4.14, while the dog sits near 1.2, the horse near 0.9, and the rat near 0.4.
Most vertebrate species devote between 2% and 8% of basal metabolism to the brain, but in humans the figure rises to 20 to 25%. Most of that energy goes into sustaining the membrane potential of neurons, which is why large brains place severe metabolic demands on animals.
The oldest brain ever discovered was found in Armenia in the Areni-1 cave complex, inside the skull of a girl aged 12 to 14. Estimated to be over 5,000 years old, it was shriveled but well preserved because of the climate inside the cave.
In 1971, Tim Bliss and Terje Lomo published a paper on long-term potentiation, showing clear evidence of activity-induced synaptic changes that lasted at least several days. The synaptic plasticity hypothesis had been argued by Santiago Ramon y Cajal in the late 19th century, but experimental evidence was lacking until 1970.