Visual area of brain plays role in memory

Reuters News

An area of the brain that plays a role in vision is also important in remembering objects, scenes, and distances, US researchers report in the April 2nd issue of the journal Science.

Scientists have wondered if recalling information about an object or a scene actually involves visualizing it in terms of color, shape and texture, or if that information is just an extraneous by-product of the brain's activity as people draw on their memory.

To find out, scientists at Harvard University in Boston, Massachusetts, asked volunteers to memorize four pictures of stripes. In one picture there were four vertical stripes, in another two horizontal stripes, in a third there were three stripes on a diagonal, and in the fourth there were five stripes on the opposite diagonal.

After gazing at the four pictures, the volunteers were asked to close their eyes and answer questions about the images. Their brain activity was monitored by positron emission tomography (PET) scanning. Results of the scanning showed activity in Area 17 of the brain, part of the visual cortex, as volunteers recalled the images.

The PET scan showed where the activity was located in the brain, but not whether such imagery was critical to the task of recalling specific information about the images.

To find out, the investigators used transcranial magnetic stimulation to scramble the signals in Area 17 of the volunteers' brains. When asked questions about the pictures again, the volunteers performed poorly.
The results show that the parts of the brain's visual cortex are used in at least some forms of visual imagery as well as in visual perception, write the investigators.

SOURCE: Science 1999;284:167-170.