Final answer:
The claim that new neurons do not appear in the adult vertebrate brain is false, as current evidence supports the occurrence of neurogenesis or the generation of new neurons from neural stem cells in adulthood.
Step-by-step explanation:
The statement that new neurons do not appear in the brains of adult vertebrate animals is false. Neurogenesis, the process of new neuron formation, can occur in the adult brain. Although fully differentiated neurons cannot divide to form new neurons, undifferentiated neural stem cells found throughout the brain can divide and form new neurons. These stem cells are capable of differentiating into neurons and integrating into the existing neural network.
The belief that adults cannot generate new neurons was common in the past, but current research has shown that neurogenesis does occur in adult brains, although the extent to which it happens is not fully understood and may not be very significant in humans.