For years, conventional wisdom held that growing older tends to be bad news for brains. Past behavioral data largely pointed to loss in cognitive – that is, thinking – abilities with age, including poorer memory and greater distractibility. Physical measures of brain structure also showed atrophy, or loss of volume, in many regions with age.
Enter cognitive neuroscience, a subfield of psychology that incorporates methods from neuroscience. It uses measures of brain activity to understand human thought. The emphasis is on how the brain shapes behavior, asking questions like which brain regions help us form accurate memories or what area controls face perception.
Using cognitive neuroscience methods to study aging has unexpectedly revealed that,contrary to previous thought, aging brains remain somewhat malleable and plastic. Plasticity refers to the ability to flexibly recruit different areas of the brain to do different jobs. In contrast to the earlier, largely pessimistic view of aging, neuroimaging studies suggest aging brains can reorganize and change, and not necessarily for the worse.
One exciting new direction for research on the aging brain uses neurostimulation to temporarily activate or suppress distinct neural regions. With transcranial magnetic stimulation, a coil is held over a participant’s head. Participants may be able to feel some stimulation on the scalp when the coil is turned on. Transcranial direct current stimulation is an even more surprising technique, with current administered from a 9V battery. These methods are non-invasive, simply involving holding a device over a person’s head or attaching electrodes to the scalp, and are quite safe when operated within guidelines.
They allow us, for the first time, to manipulate brain activity in a healthy, functioning person. Other neuroscience methods allow neurons to be turned on or turned off using pharmacological, genetic, or other methods, but such manipulations can’t ethically be applied to humans. While neuroimaging methods allow us to view which brain regions are active while performing cognitive tasks, we haven’t been able to test whether those brain regions cause, or are critical for, those tasks.
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