Earth Science News  





. Mapping The Selective Brain

The fMRI scans revealed a sensory processing area of the brain known as the left supramarginal gyrus as a distinctive categorical processing area. This area activated when subjects heard sound pairs that they had earlier reported perceiving as different. In contrast, the left supramarginal gyrus did not respond significantly to sound pairs that the subjects perceived as the same, found the researchers.
by Staff Writers
Washington DC (SPX) Nov 22, 2007
Researchers have added a new piece to the puzzle of how the brain selectively amplifies those distinctions that matter most from the continuous cascade of sights, sounds, and other sensory input. Whether recognizing a glowering face among smiling ones or the unmistakable sound of a spouse calling one's name, such "categorical perception" is central to sensory function.

Specifically, Rajeev Raizada and Russell Poldrack report identifying a brain region that selectively amplifies behaviorally significant speech sounds. They also emphasized that their experimental approach represents a useful advance because it not only detects brain activity associated with a given task, but identifies the type of computation the brain is performing during the task.

The researchers reported their findings in the November 21, 2007, issue of the journal Neuron, published by Cell Press.

In their experiments, the researchers used a set of ten computer-synthesized speech sounds that represented a continuum from the sound "ba" to the sound "da." They designated these on a 1 to 10 scale, with the former being pure "ba" and the latter being pure "da."

The researchers first played human volunteers different pairs of the two sounds, for example 4 and 7, and asked them to indicate which pairs they distinguished as different from one another.

They next played the same pairs of sounds to the subjects as the subjects' brains were scanned using functional magnetic resonance imaging (fMRI). This widely used technique involves using harmless radio waves and magnetic fields to measure blood flow in brain regions, which reflects activity.

By searching for brain areas distinctively activated during pairs of sounds the subjects perceived as different, the researchers could pinpoint any brain region involved in the selective amplification of categorical perception.

The fMRI scans revealed a sensory processing area of the brain known as the left supramarginal gyrus as a distinctive categorical processing area. This area activated when subjects heard sound pairs that they had earlier reported perceiving as different. In contrast, the left supramarginal gyrus did not respond significantly to sound pairs that the subjects perceived as the same, found the researchers.

What's more, lower-level auditory regions of the brain or another speech-processing area did not respond significantly to the distinctive sound pairs, found the researchers.

The researchers wrote that "A key aspect of the method proposed here, and one that is especially relevant to categorical perception, is that we were seeking not just neural amplification per se, but in particular selective amplification. Thus, an area such as the left supramarginal gyrus not only amplified differences between the phonetic stimuli, but moreover it specifically amplified only the differences that corresponded to crossing each subject's perceptual category boundary.

"The way in which the brain selectively amplifies stimulus differences can help to reveal how its representations of the world are structured," they wrote. "Such amplification can be said to be involved in a neural representation, as opposed to being just incidental activity, only if it is related to perception and behavior.... Used together, these tools can help to reveal when the brain sees the world in shades of gray, and when it sees in black-and-white."

Community
Email This Article
Comment On This Article

Related Links
All About Human Beings and How We Got To Be Here




Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
How Do We Make Sense Of What We See
Baltimore MD (SPX) Nov 21, 2007
M.C. Escher's ambiguous drawings transfix us: Are those black birds flying against a white sky or white birds soaring out of a black sky? Which side is up on those crazy staircases? Lines in Escher's drawings can seem to be part of either of two different shapes. How does our brain decide which of those shapes to "see?" In a situation where the visual information provided is ambiguous -- whether we are looking at Escher's art or looking at, say, a forest -- how do our brains settle on just one interpretation?

.
Get Our Free Newsletters Via Email
  



  • LSU Helps Bangladesh Save Lives By Providing Storm Surge Models 24 Hours In Advance Of Cyclone Sidr
  • Tsunami-Recording In The Deep Sea
  • Bangladesh cyclone an 'ecological disaster': experts
  • Mexico fumigates flooded Tabasco to prevent dengue

  • New Research Shows Climate Change Triggers Wars And Population Decline
  • Ancient Chinese town on front lines of desertification battle
  • MIT Sees Acceleration In US Greenhouse Emissions
  • Climate change: Political outlook murky despite the science

  • TRMM Turns Ten - Studying Precipitation From Space
  • Rosetta: OSIRIS' View Of Earth By Night
  • Strange Space Weather Over Africa
  • KAGUYA Captures The Earth Rising Over The Moon

  • China a big, but not only, contributor to record oil prices: analysts
  • Analysis: Billions pumped into Niger Delta
  • Britain to build world's biggest biomass plant
  • The Power Of Multiples: Connecting Wind Farms Can Make A More Reliable - And Cheaper - Power Source

  • UN cuts AIDS infection estimate: report
  • Repellents Between Dusk And Bedtime Make Insecticide-Treated Bednets More Effective
  • Global Fund approves over 1 bln dlrs in new grants to fight disease
  • Bug-Zapper: A Dose Of Radiation May Help Knock Out Malaria

  • Are Current Projections Of Climate Change-Impacts On Biodiversity Misleading
  • 390-Million-Year-Old Scorpion Fossil Is The Biggest Known Bug
  • Evolutionary Biology Research On Plant Shows Significance Of Maternal Effects
  • Cooling Down Begins At Svalbard Global Seed Vault

  • Atmospheric Measuring Device For Understanding Smog Formation
  • China pollution costs 5.8 pct of GDP: report
  • Local Sources Major Cause Of US Near-Ground Aerosol Pollution
  • Brazilian CO2 pollution outstripping economic growth: study

  • Mapping The Selective Brain
  • How Do We Make Sense Of What We See
  • New Antarctica Research Season Kicks Off
  • UW-Madison Scientists Guide Human Skin Cells To Embryonic State

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement