From: deputydawg23x@gmail.com   
      
   To locate objects, brain relies on memory   
   Neuroscientists identify brain region that holds objects in memory until they   
   are spotted.   
      
      
   Anne Trafton | MIT News Office    
   October 29, 2015   
      
      
   Imagine you are looking for your wallet on a cluttered desk. As you scan the   
   area, you hold in your mind a mental picture of what your wallet looks like.   
   MIT neuroscientists have now identified a brain region that stores this type   
   of visual representation during a search. The researchers also found that this   
   region sends signals to the parts of the brain that control eye movements,   
   telling individuals    
   where to look next.   
   This region, known as the ventral pre-arcuate (VPA), is critical for what the   
   researchers call "feature attention," which allows the brain to seek objects   
   based on their specific properties. Most previous studies of how the brain   
   pays attention have    
   investigated a different type of attention known as spatial attention -- that   
   is, what happens when the brain focuses on a certain location.   
   "The way that people go about their lives most of the time, they don't know   
   where things are in advance. They're paying attention to things based on their   
   features," says Robert Desimone, director of MIT's McGovern Institute for   
   Brain Research. "In the    
   morning you're trying to find your car keys so you can go to work. How do you   
   do that? You don't look at every pixel in your house. You have to use your   
   knowledge of what your car keys look like."   
   Desimone, also the Doris and Don Berkey Professor in MIT's Department of Brain   
   and Cognitive Sciences, is the senior author of a paper describing the   
   findings in the Oct. 29 online edition of Neuron. The paper's lead author is   
   Narcisse Bichot, a research    
   scientist at the McGovern Institute. Other authors are Matthew Heard, a former   
   research technician, and Ellen DeGennaro, a graduate student in the   
   Harvard-MIT Division of Health Sciences and Technology.   
   Visual targets   
   The researchers focused on the VPA in part because of its extensive   
   connections with the brain's frontal eye fields, which control eye movements.   
   Located in the prefrontal cortex, the VPA has previously been linked with   
   working memory -- a cognitive    
   ability that helps us to gather and coordinate information while performing   
   tasks such as solving a math problem or participating in a conversation.   
   "There have been a lot of studies showing that this region of the cortex is   
   heavily involved in working memory," Bichot says. "If you have to remember   
   something, cells in these areas are involved in holding the memory of that   
   object for the purpose of    
   identifying it later."   
   In the new study, the researchers found that the VPA also holds what they call   
   an "attentional template" -- that is, a memory of the item being sought.   
   In this study, the researchers first showed monkeys a target object, such as a   
   human face, a banana, or a butterfly. After a delay, they showed an array of   
   objects that included the target. When the animal fixed its gaze on the target   
   object, it received    
   a reward. "The animals can look around as long as they want until they find   
   what they're looking for," Bichot says.   
   As the animals performed the task, the researchers recorded electrical   
   activity from neurons in the VPA. Each object produced a distinctive pattern   
   of neural activity, and the neurons that encoded a representation of the   
   target object stayed active until    
   a match was found, prompting the neurons to fire even more.   
   "When the target object finally enters their receptive fields, they give   
   enhanced responses," Desimone says. "That's the signal that the thing they're   
   looking for is actually there."   
   About 20 to 30 milliseconds after the VPA cells respond to the target object,   
   they send a signal to the frontal eye fields, which direct the eyes to lock   
   onto the target.   
   When the researchers blocked VPA activity, they found that although the   
   animals could still move their eyes around in search of the target object,   
   they could not find it. "Presumably it's because they've lost this mechanism   
   for telling them where the    
   likely target is," Desimone says.   
   Focused attention   
   The researchers believe the VPA may be the equivalent in nonhuman primates of   
   a human brain region called the inferior frontal junction (IFJ). Last year   
   Desimone and postdoc Daniel Baldauf found that the IFJ holds onto the idea of   
   a target object -- in    
   that study, either faces or houses -- and then directs the correct part of the   
   brain to look for the target.   
   The researchers are now studying how the VPA interacts with a nearby region   
   called the VPS, which appears to be more important for tasks in which   
   attention must be switched quickly from one object to another. They are also   
   performing additional studies    
   of human attention, in hopes of learning more about disorders such as   
   Attention Deficit Hyperactivity Disorder and other attention disorders.   
   "There's really an opportunity there to understand something important about   
   the role of the prefrontal cortex in both normal behavior and in brain   
   disorders," Desimone says.   
   TOPICS:   
   ResearchBrain and cognitive sciencesNeuroscienceMemoryMcGovern InstituteSchool   
   of Science   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)