Final answer:
During senescence, the brain undergoes various changes, including reduced neuroplasticity, which leads to a decline in information processing, reasoning, and memory.
Step-by-step explanation:
According to the textbook, one of the changes that happens to the brain during senescence is b) Reduced neuroplasticity. Neuroplasticity is the brain's ability to reorganize itself by forming new neural connections, and it tends to decline as we age. This decrease in neuroplasticity can affect information processing abilities, reasoning, and memory, which are aspects of fluid intelligence. As such, older adults may experience a reduced ability to integrate new information and adapt to new situations or environments.