Brain cells work together to pay attention.When the brain snaps to attention, individual neurons don't necessarily work harder, but clusters of them form cooperative units, a new study suggests.
This unifying brain process, in which nerve cells briefly align the peaks and valleys of their electrical outbursts, may underlie an animal's shifting of attention to a particular sight, sound, or other sensation, according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. a team of neuroscientists led by Peter N. Steinmetz of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena.
In the past decade, several scientists linked synchronized electrical activity in groups of neurons to perception and memory in cats and other nonhuman animals (SN: 2/21/98, p. 120). Preliminary evidence also implicates coordinated neural firing in human perception and learning (SN: 2/20/99, p. 122).
Some investigators hold that groups of neurons must fire in aligned patterns to generate thoughts and consciousness. Others regard such synchronized activity as a byproduct by·prod·uct or by-prod·uct
1. Something produced in the making of something else.
2. A secondary result; a side effect.
Noun 1. of more crucial processes that occur within densely connected webs of neurons.
Taking the former position, Steinmetz and his colleagues have focused on the allocation of mental resources. "Change in synchrony synchrony /syn·chro·ny/ (-krah-ne) the occurrence of two events simultaneously or with a fixed time interval between them.
atrioventricular (AV) synchrony may be an essential neural mechanism of selective attention," they conclude in the March 9 NATURE.
The researchers recorded the electrical activity of neurons in a monkey brain area near the middle of the cortex. Cells in this region, the secondary somatosensory cortex somatosensory cortex
Variant of somatic sensory cortex. , emit discharges most rapidly when the animal touches an item while paying close attention to it.
Each monkey was trained to perform the same visual task and one of three tactile maneuvers. They also learned to switch from one task to the other at assigned times while the researchers presented visual and tactile stimuli simultaneously.
The visual task required each monkey to detect, in a series of trials, which of three white squares on a computer screen dims slightly.
As for tactile tasks, one monkey touched a finger pad over which a series of raised letters moved. Upon finding a match for a letter shown on a computer screen, the animal pressed a key. Another monkey completed a more difficult version of this task, in which the letter to be matched changed after each correct response. The third animal had to indicate repeatedly whether raised bars on a finger pad had the same or different orientations.
The monkeys switched between tactile and visual tasks every 7 to 8 minutes as microelectrodes implanted in their brains recorded cell activity in the secondary somatosensory cortex. The scientists analyzed responses of 436 individual neurons and 648 pairs of neurons.
Nearly 80 percent of individual neurons discharged different numbers of electrical pulses during the two tasks, an encouraging sign that the change of attention altered their firing rates. Moreover, two-thirds of all neuron pairs displayed synchronized activity during one or both tasks.
Most importantly Adv. 1. most importantly - above and beyond all other consideration; "above all, you must be independent"
above all, most especially , the researchers say, synchrony in cellular duos reached higher levels during tactile trials--and in particular during the more difficult letter-matching challenge--than during the visual task. Coordinated activity often rose without accompanying hikes in firing rates by individual neurons.
"Whatever the underlying mechanism, these results are strong evidence that neuronal [pulse] synchrony correlates with a cognitive process, namely, shifting of the attentional focus," assert Emilio Salinas Salinas, city, United States
Salinas (səlē`nəs), city (1990 pop. 108,777), seat of Monterey co., W Calif.; inc. 1874. It is the shipping and processing center of a fertile valley famous for its grain and lettuce. of the Howard Hughes Medical Institute Howard Hughes Medical Institute, (HHMI), nonprofit medical research organization founded in 1953 by Howard Hughes and largly funded from proceeds of the 1984–85 sale of Hughes Aircraft. Headquartered in Chevy Chase, Md. at the Salk Institute for Biological Studies The Salk Institute for Biological Studies is an independent, non-profit, scientific research laboratory located in La Jolla, California. It was founded in 1960 by Jonas Salk, M.D., the developer of the polio vaccine. in La Jolla, Calif., and Ranulfo Romo of the National Autonomous University of Mexico The National Autonomous University of Mexico (Spanish: , abbreviated UNAM) is a large public university in Mexico. It was founded on September 21 1551 as the Real y Pontificia Universidad de México in Mexico City in a comment in the same issue of NATURE.
It's unclear whether increased synchrony in the somatosensory cortex improves subsequent stages of tactile processing in the brain, Salinas and Romo say.