Final answer:
Scientists were surprised to discover increased brain plasticity and the continuation of neurogenesis into adulthood. Initially observed in songbirds, this neurological adaptability is also present in humans, with the generation of new neurons in the hippocampus being essential for learning and memory.
Step-by-step explanation:
The brain changes that surprised scientists when it was discovered was the increased brain plasticity later in life. While it was known that the brain undergoes significant development in early childhood, reaching about 90% of its adult size by the age of six, the concept of continued neuroplasticity into adulthood was not always accepted. Traditional beliefs held that all neurons were present at birth and no new neurons would be formed. However, more recent research has shown that neurogenesis, the birth of new neurons, occurs throughout adulthood. This finding, initially discovered in songbirds and later in mammals including humans, highlights that the brain retains the ability to generate new neurons in the hippocampus, which is crucial for learning and memory. Activities such as exercise and certain antidepressants have been found to promote neurogenesis, whereas stress has the opposite effect. This discovery of neurogenesis and the adaptability of the adult brain through neuroplasticity continues to offer hope for new treatments for neurodegenerative diseases like Alzheimer's.