In a Host of Ailments, Seeing a Brain Out of Rhythm

Dr. Llinás, the chairman of neuroscience and physiology at the N.Y.U. School of Medicine, believes that abnormal brain rhythms help account for a variety of serious disorders, including Parkinson’s disease, schizophrenia, tinnitus and depression. His theory may explain why the technique called deep brain stimulation — implanting electrodes into particular regions of the brain — often alleviates the symptoms of movement disorders like Parkinson’s.

The theory is far from widely accepted, and most neurosurgeons say the mechanisms behind deep brain stimulation remain a mystery. Still, surgeons like Dr. Kelly are excited about the research, saying it suggests new targets for treating a variety of disorders.

“It’s a mystery to me why it took me so long to get what Rodolfo was saying,” Dr. Kelly said. “I’d like to latch on to the excuse that I was too busy. In truth, I was too dumb to listen. Now I tell my younger colleagues, ‘Listen to this man.’ He’s on to something that can revolutionize neurosurgery and our understanding of how the brain works.”

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The thalamus and cortex work dynamically by passing loops of information back and forth, Dr. Llinás said. “If you think of the brain as an orchestra, the thalamus is the conductor. The players are in the cortex. When the conductor makes a move, the players follow. The conductor then hears their sounds and makes new moves, resulting in a continuous dialogue.”

Cells in the thalamus and cortex rely on intrinsic electrical properties to keep the music going. “Groups of neurons, millions strong, act like little hearts beating all their own,” Dr. Llinás said. They can oscillate at multiple frequencies, depending on what is happening in the outside world.

When the brain is awake, neurons in the cortex and thalamus oscillate at the same high frequency, called gamma. “It’s like a Riverdance performance,” Dr. Llinás continued. “Some cells are tapping in harmony and some are silent, creating myriads of patterns that represent the properties of the external world. Cells with the same rhythm form circuits to bind information in time. Such coherent activity allows you to see and hear, to be alert and able to think.”

But at day’s end, cells in the thalamus naturally enter a low-frequency oscillation. They burst slowly instead of firing rapidly. With the thalamus thrumming at a slower rhythm, the cortex follows along. You fall asleep. Your brain is still tapping out slow rhythms, but consciousness is suspended.

So if a small part of the thalamus gets permanently stuck at a low frequency, or part of the cortex fails to respond to the wake-up call, Dr. Llinás said, an abnormal rhythm is generated, a so-called thalamocortical dysrhythmia.
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Dr. Llinás believes that these disrupted rhythms can be set off by a variety of causes — faulty genes, brain injury, chemical imbalance. In the case of his colleague Dr. Kelly, a small portion of the auditory cortex was damaged by helicopter noise. Dr. Llinás spotted it in the MEG machine — a spot oscillating as if in light sleep.

Tinnitus and other dysrhythmias can be treated with deep brain stimulation, drugs or tiny surgical lesions that return brain oscillations to normal, he said. The goal is to wake up parts of the brain that have fallen into low-frequency sleep mode.