Older but mellower: aging brain shifts gears to emotional advantage.

Given all the bad news that science has delivered about brain cells withering and memory waning as the years mount, older people have a right to be cranky. But, instead, the over-50 crowd handles life's rotten realities and finds life's bright side more effectively than whippersnappers do. In no small part, that's because the aging brain makes critical emotional adjustments, a new study indicates.

Advancing age heralds a growth in emotional stability accompanied by a neural transition to increased control over negative emotions and greater accessibility of positive emotions, according to a team led by neuroscientist Leanne M. Williams of Westmead (Australia) Hospital. A brain area needed for conscious thought, the medial prefrontal cortex, primarily influences these emotional reactions in older adults, Williams and her colleagues say.

In contrast, people under age 50 experience negative emotions more easily than they do positive ones. These younger adults' emotion-related activity centers on the amygdala, a brain structure previously implicated in automatic fear responses.

This gradual reorganization of the brain's emotion system may result from older folk responding to accumulating personal experiences by increasingly looking for meaning in life, the researchers propose in the June 14 Journal of Neuroscience.

Evidence that emotional functions improve in older brains "indicates that our ability to register the significance of information is preserved, and even enhanced, as we age," Williams says. Older people may benefit from associating information they need to remember with personally significant matters, such as a favorite tune, he adds.

Ironically, older individuals' reliance on the medial prefrontal cortex to regulate emotions comes as aging kills cells in this area. The surviving neurons somehow pick up the slack, the investigators note.

The researchers studied 122 males and 120 females, ages 12 to 79, who had no current or past mental illnesses and good physical health.

Scores on a questionnaire that assesses emotional stability rose steadily from adolescence into the senior years.

Brain testing occurred as volunteers viewed images of various facial expressions. They had been told to identify the emotion in each expression and to rank its intensity. Researchers measured neural response using functional magnetic resonance imaging, which tracked blood-flow changes, and an electrode-studded cap that monitored brain cells' electrical responses.

In older adults, mushrooming medial prefrontal cortex activity triggered by negative facial expressions occurred in conjunction with neural responses that have been linked to conscious thought. This pattern appeared even in older adults who displayed especially low numbers of prefrontal neurons.

In contrast, young people showed far more medial prefrontal activity, and thus conscious thought, in response to positive facial expressions than older people did.

The new results provide a neural framework for growing evidence that, unlike young people, older adults focus on positive information and downplay negative events, remarks psychologist Mara Mather of the University of California, Santa Cruz. The amygdala showed little volume decline with age in the new study, so it's unlikely that age-related shrinkage of that structure causes the psychological shift, she adds.

"Older adults apparently use cognitive-control processes supported by prefrontal brain regions to help them avoid experiencing negative information and focus instead on positive information," Mather says.

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