Tag Archives: Frequency

An interesting essay

29 Nov

from www.lastwordonnothing.com

Break through

By Virginia Hughes | November 29, 2011

This past summer, I spent two weeks sitting, working and, once, sleeping next to a hospital bed, trying and failing to communicate with my father.

He had called for an ambulance on the evening of July 25 because he couldn’t breathe. With end-stage emphysema, he often couldn’t breathe, but apparently that night he was frightened enough to call for help. At the hospital, the doctors intubated him and doused him with the sedatives one needs to withstand a hard plastic tube down the throat. My sister and I never knew if he had agreed to the intubation, or if he was too weak or panicked to voice a clear opinion. Over the next few days in the ICU, although still heavily sedated, he sometimes acted in ways that seemed deliberate: he would open his eyes wide, or furrow his brow, or nod to a question or squeeze my hand. But I was never really sure. I wasn’t sure if he would have wanted us to agree to the tracheostomy procedure, on August 2, or remove the ventilator, on August 9.

What if I could have been more sure?

I couldn’t help but think about that a couple of weeks ago while having coffee with Jon Bardin at the Society for Neuroscience meeting in Washington, D.C. A few years back, Jon left the science magazine where we both worked to pursue a PhD in neuroscience. He joined the lab of Nicholas Schiff, an expert on the neural basis of consciousness, and began studying the brain activity of people with severe brain injury. And now at the conference, Jon told me, he would be presenting a poster of unpublished data suggesting that brain waves can reveal whether a somewhat conscious person is tuning in when other people speak.

Later I found Jon’s poster, one of thousands pinned on boards in the basement of the convention center. The star of his data was patient M1, a 57-year-old woman whom I’ll call Janet. Seven years ago, Janet had a stroke that left her in a ‘minimally conscious state’ until she died about a year ago. During that long hospital stay, she sometimes responded to other people — by tracking objects with her eyes or following simple commands — but never initiated an action and never spoke.

About three years ago, using a technique called electroencephalography (EEG), Jon and his colleagues put a few dozen electrodes on Janet’s scalp and recorded the brain waves emitted over a 72-hour period. Brain waves represent the synchronous activity of thousands or millions of neurons and are measured in frequency units called Hertz, or cycles per second. On a raw EEG read-out, low-frequency brain waves look fat, like a mountainscape, whereas high-frequency waves are skinny and sharp, like blades of grass. Waves of different frequencies have been tied to different biological functions. For example, somewhat slow ‘alpha’ waves, 8 to 13 Hertz, appear when eyes close.

Many things happened around Janet during those three days of recording: her family came in and out, her neighbor watched television, monitors beeped, nurses gabbed. Most relevant for the experiment were the seven minutes when the researchers played a recording of her sister telling a story about a family trip to Paris. Here’s what Janet’s brain waves looked like in the seconds before and after the onset of the recording (green)…follow link to read more

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