A study has found that the human brain undergoes distinct changes throughout a lifetime, with some reports suggesting five distinct epochs or eras. The timing of these changes is not entirely clear, with one report indicating that adult mode may not start until the early 30s, while another identifies specific ages of change at 9, 32, 66, and 83. The research appears to identify multiple key points of brain development and aging, although the exact number and timing of these events may vary.