How brain chooses to focus on some faces and ignore others
A new study has explained how the brain chooses what to pay attention too and what to merely monitor and ignore.
MIT neuroscientists found that a part of the prefrontal cortex known as the inferior frontal junction (IFJ) controls visual processing areas that are tuned to recognize a specific category of objects.
Scientists know much less about this type of attention, known as object-based attention, than spatial attention, which involves focusing on what's happening in a particular location.
However, the new findings suggest that these two types of attention have similar mechanisms involving related brain regions, senior author Robert Desimone from MIT, said.
In both cases, the prefrontal cortex — the control center for most cognitive functions — appears to take charge of the brain's attention and control relevant parts of the visual cortex, which receives sensory input.
In the new study, the researchers found that IFJ coordinates with a brain region that processes faces, known as the fusiform face area (FFA), and a region that interprets information about places, known as the parahippocampal place area (PPA).
The IFJ has previously been implicated in a cognitive ability known as working memory, which is what allows us to gather and coordinate information while performing a task, such as remembering and dialing a phone number, or doing a math problem.
For this study, the researchers used magnetoencephalography (MEG) to scan human subjects as they viewed a series of overlapping images of faces and houses.
The researchers presented the overlapping streams at two different rhythms — two images per second and 1.5 images per second — allowing them to identify brain regions responding to those stimuli.
Daniel Baldauf, a postdoc at the McGovern Institute and the lead author of the paper, said that his team wanted to frequency-tag each stimulus with different rhythms. When you look at all of the brain activity, you can tell apart signals that are engaged in processing each stimulus.
Each subject was told to pay attention to either faces or houses; because the houses and faces were in the same spot, the brain could not use spatial information to distinguish them.
When the subjects were told to look for faces, activity in the FFA and the IFJ became synchronized, suggesting that they were communicating with each other. When the subjects paid attention to houses, the IFJ synchronized instead with the PPA.
The researchers believe that the IFJ holds onto the idea of the object that the brain is looking for and directs the correct part of the brain to look for it.
The study is published in the April 10 online edition of Science.
(Posted on 11-04-2014)