New research from the US suggests that when we look for something in our environment, our attention scans one thing at a time, using a serial as opposed to a parallel process whose clock speed is controlled by brain waves or “neuron population oscillations”.
Thus next time you arrange to meet a friend in a crowded bar or restaurant, remember that your attention searches the room like a superfast spotlight, pausing on each face for only 1/25th of a second, before settling on the one familiar to you, or at least that is what postdoctoral associate Timothy J Buschman, and Picower Professor of Neuroscience Earl Miller suggest in a paper published in the 13 August online issue of the journal Neuron.
Both authors are from the Picower Institute for Learning and Memory and Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts.
The control of attention, the process that manages the information that floods in via our senses, is somewhat of a mystery, yet if we knew more about it, we might also find out more about cognition, or what happens when we think about what the information coming in through our senses is telling us.
Theories say that the mechanism of attention either processes sensory information in parallel (more or less all at once), or that it processes it serially (one chunk at a time). However, according to their background information, Buschman and Miller wrote that neither idea has much evidence behind it and that’s why they wanted to find out more.
Miller told the media that:
“For many years, neuroscientists have been debating competing theories on whether humans and animals spontaneously search elements of a visual scene in a serial or parallel manner.”
“Ours is the first study based on direct evidence of neurophysiological activity,” he added.
For the study, they trained two monkeys to look for one particular tilted, colored bar in a field of bars visible on a computer screen.
By observing what happened to “neuronal spiking activity” in three regions of the monkeys’ brains, Buschman and Miller found the monkeys spontaneously shifted their attention in a sequence as they searched for the bar on the screen, rather like a spotlight that jumped from one position to the next.
The other thing they discovered was that the attention shifts reflected in the neuronal spiking activity “were correlated with 1834 Hz oscillations in the local field potential, suggesting a clocking signal”.
Thus the study implies that brain waves act like a built-in clock that times the shifts of attention from one position to the next.
Buschman and Miller said their work could help improve understanding and treatments for conditions like attention deficit disorder, and perhaps even help find ways to increase the rate of cognition in the brain.
Researchers have been observing brain waves for over 100 years and over that time discovered that the brain has cycles of high and low activity. However, the mechanism linking this activity and the processes of memory, decision-making and communication among regions of the brain is still unclear.
This work suggests a new and fundamental role for brain waves: to make sure the “spotlight in the mind’s eye” moves at a rate of 25 times a second, as Buschman discovered.
“This is one of the first examples of how brain waves play a specific role in cognitive computations,” said Buschman.
“Attention regulates the flood of sensory information pouring into the brain into a manageable stream. In particular, a lot of different areas of the brain are involved in vision. If they all competed at once, it would be chaos,” Miller explained.
“Brain waves may provide the clock that tells the brain when to shift its attention from one stimulus to another,” he added, explaining that perhaps “oscillating brain waves may provide a way for several regions across the brain to be on the same page at the same time,” which is similar to how processing clock speed works to ensure different parts of a computer stay in step with each other.
Buschman and Miller now want to explore what happens with other senses, and find out whether brain waves act as a general clock for the brain, or are they just for the visual functions.
The National Science Foundation and the National Institute of Neurological Disorders and Stroke sponsored the study.
“Serial, Covert Shifts of Attention during Visual Search Are Reflected by the Frontal Eye Fields and Correlated with Population Oscillations.”
Timothy J. Buschman, Earl K. Miller.
Source: MIT News.
Written by: Catharine Paddock, PhD