Navigation Links
JPEG for the mind: How the brain compresses visual information
Date:2/10/2011

Most of us are familiar with the idea of image compression in computers. File extensions like ".jpg" or ".png" signify that millions of pixel values have been compressed into a more efficient format, reducing file size by a factor of 10 or more with little or no apparent change in image quality. The full set of original pixel values would occupy too much space in computer memory and take too long to transmit across networks.

The brain is faced with a similar problem. The images captured by light-sensitive cells in the retina are on the order of a megapixel. The brain does not have the transmission or memory capacity to deal with a lifetime of megapixel images. Instead, the brain must select out only the most vital information for understanding the visual world.

In today's online issue of Current Biology, a Johns Hopkins team led by neuroscientists Ed Connor and Kechen Zhang describes what appears to be the next step in understanding how the brain compresses visual information down to the essentials.

They found that cells in area "V4," a midlevel stage in the primate brain's object vision pathway, are highly selective for image regions containing acute curvature. Experiments by doctoral student Eric Carlson showed that V4 cells are very responsive to sharply curved or angled edges, and much less responsive to flat edges or shallow curves.

To understand how selectivity for acute curvature might help with compression of visual information, co-author Russell Rasquinha (now at University of Toronto) created a computer model of hundreds of V4-like cells, training them on thousands of natural object images. After training, each image evoked responses from a large proportion of the virtual V4 cells -- the opposite of a compressed format. And, somewhat surprisingly, these virtual V4 cells responded mostly to flat edges and shallow curvatures, just the opposite of what was observed for real V4 cells.

The results were quite different when the model was trained to limit the number of virtual V4 cells responding to each image. As this limit on responsive cells was tightened, the selectivity of the cells shifted from shallow to acute curvature. The tightest limit produced an eight-fold decrease in the number of cells responding to each image, comparable to the file size reduction achieved by compressing photographs into the .jpeg format. At this level, the computer model produced the same strong bias toward high curvature observed in the real V4 cells.

Why would focusing on acute curvature regions produce such savings? Because, as the group's analyses showed, high-curvature regions are relatively rare in natural objects, compared to flat and shallow curvature. Responding to rare features rather than common features is automatically economical.

Despite the fact that they are relatively rare, high-curvature regions are very useful for distinguishing and recognizing objects, said Connor, a professor in the Solomon H. Snyder Department of Neuroscience in the School of Medicine, and director of the Zanvyl Krieger Mind/Brain Institute.

"Psychological experiments have shown that subjects can still recognize line drawings of objects when flat edges are erased. But erasing angles and other regions of high curvature makes recognition difficult," he explained

Brain mechanisms such as the V4 coding scheme described by Connor and colleagues help explain why we are all visual geniuses.

"Computers can beat us at math and chess," said Connor, "but they can't match our ability to distinguish, recognize, understand, remember, and manipulate the objects that make up our world." This core human ability depends in part on condensing visual information to a tractable level. For now, at least, the .brain format seems to be the best compression algorithm around.


'/>"/>

Contact: Lisa DeNike
Lde@jhu.edu
443-287-9960
Johns Hopkins University
Source:Eurekalert  

Related medicine news :

1. What makes fructose fattening? OHSU researchers find some answers in the brain
2. Gestures May Help the Brain See
3. Study Links Brain Molecule to Risk of Major Depression
4. Major step taken toward an open and shared digital brain atlasing framework
5. Schizophrenia Drugs May Spur Subtle Brain Tissue Loss
6. Allergies Linked to Lower Brain Cancer Rate in Study
7. Brains need love, too
8. Electrical Stimulation of the Brain May Spark Insight
9. Targeted particle fools brains guardian to reach tumors
10. Brain scans predict likely success when it comes to quitting smoking
11. Brain pacemakers: A long-lasting solution in the fight against depression
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
JPEG for the mind:  How the brain compresses visual information
(Date:2/13/2016)... Salt Lake City, Utah (PRWEB) , ... February 13, 2016 , ... When an ... kids, Host Parents aren’t always sure what they are in for and they are often ... Pairs are more than they were hoping for. This year’s Au Pair of the Year ...
(Date:2/12/2016)... ... February 12, 2016 , ... The law firm of Morrow, Morrow, ... The purpose of these scholarships is to encourage applicants to pursue a degree ... employment within these two parishes. , “We have available jobs in St. Landry ...
(Date:2/12/2016)... ... ... Each year, the American Physical Therapy Association (APTA) offers a Combined Sections Meeting. ... Almost 10,000 physical therapists across the country are expected to attend this annual convention ... field and network with their colleagues. As in years past, HydroWorx is proud ...
(Date:2/12/2016)... ... 2016 , ... Itopia, a leader in cloud services automation ... Platform (CIP) into Cielo®, a discovery, migration and cloud orchestration engine. This integration ... and medium business (SMB) clients. , In recent years, BI and ...
(Date:2/12/2016)... Vail, Colorado (PRWEB) , ... February 12, 2016 , ... ... 164 ASC Industry Physician Leaders to Know in 2016 . The list consists of ... leaders nominated physicians to establish this list. , An Ambulatory Surgery Center, also ...
Breaking Medicine News(10 mins):
(Date:2/11/2016)... 2016 The primary goal of this research ... on the usage of liquid biopsy. Key information the ... - Timeframe of liquid biopsy adoption amidst future users ... organization type - Sample inflow to conduct liquid biopsy ... serum, and so on. - Correlation analysis of sample ...
(Date:2/11/2016)... YORK , Feb. 11, 2016 ... instruments commonly used in laboratories. These may range from ... condensers. Laboratory glassware is made from borosilicate glass because ... Laboratory plasticware, on the other hand, started gaining popularity ... it was easier to replace glass with plastic in ...
(Date:2/11/2016)... 2016  Governor Andrew M. Cuomo today announced a ... throughout Western New York . This ... Polytechnic Institute, includes a major expansion of Athenex,s North ... Buffalo , as well as the creation of ... Dunkirk . The combined projects are expected ...
Breaking Medicine Technology: