Patients with traumatic brain injury, including thousands of service members who have suffered concussions from bomb blasts in Iraq and Afghanistan, may also yield important clues to the brain's timing mechanisms, and what happens when they're disrupted.
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In short, their timing is "off," possibly because their injury has affected the bundle of time they unconsciously define as "now."
Ghajar says that getting time right allows the healthy brain to project a few steps ahead of events happening around us, and to begin setting up to react even before it's necessary. Whether volleying a tennis ball, answering a question or responding to a gesture, this anticipation allows us to respond smoothly to our world. For many brain injury patients, such effortless interaction is subtly and painfully missing. These victims of brain injury may seem awkward, lazy, agitated or slow. But Ghajar thinks many of these patients have sustained damage somewhere in the brain's timing circuits.
The weak link
"You can explain a lot of pathologies," including schizophrenia, autism and ADHD, as problems of time perception, Ghajar says.
These patients may start with faulty perception at the level of a few seconds and below, he says. "But if things start going off-track within that time frame, they're going to stay off-track through longer spans of time."
That may be one explanation for what happens to Parkinson's and Huntington's disease patients.
These patients, whose neurological disorders progressively disrupt motor control, routinely misestimate the passage of time -- both at very short intervals and at spans lasting several minutes.
In both diseases, the brain chemical dopamine becomes progressively less available, or effective, in the basal ganglia's mid-brain neighborhood.
But give a Parkinson's patient his medicine, which mimics the effect of dopamine, "and his sense of time is restored dramatically -- within minutes," marvels brain scientist Buhusi.
Such bits of medical arcana suggest to some researchers that the basal ganglia might be the weak link in the internal clocks of these patients. But the weak link could as easily be flagging attention, others say. The Parkinson's drug L-Dopa also has the effect of goosing activity in these patients' prefrontal cortices, sharpening their attention.
"We've learned a lot from Parkinson's disease patients. But we clearly haven't got it all," Buhusi says.
As the link between time perception and health has grown more visible, the study of time is no longer the sole province of philosophers, physicists and poets.
"There is no National Time Institute," says Richard Ivry, a noted time-perception researcher at UC Berkeley. But as philanthropies and funders such as the National Institute of Mental Health and the Department of Veterans Affairs gain interest, time perception may cease to be what Ivry calls "the stepchild of the sensory system" that it has traditionally been in brain-science circles.
Time's time, in short, may be now.