Some Imagination! How Memory Fails Us/Where Dreams Are Made, Really

October 1, 2005

Some Imagination! How Memory Fails UsBy Sarah DavidsonLive Science Staff Writerposted: 01 November, 20047:00 a.m. EThttp://www.livescience.com/humanbiology/041101_False_memory.html

Playing on the imagination, scientists have found it's pretty easy to make people remember things that never happened.

The parts of the brain that form, store and then retrieve memories must all work together to accurately recall events, so scientists have long been skeptical of what people remember.

A new study was designed to "bring people into the laboratory and set up a circumstance in which they would remember something that did not happen," said Kenneth Paller of Northwestern University. Researchers monitored the subjects' brains with functional magnetic resonance imaging, or fMRI, to track the false memories.

They showed the participants pictures and asked them to imagine other images. Later, investigators asked whether certain objects were seen or imagined. Often, imagined images were recalled as real.

"We think parts of the brain used to actually perceive an object and to imagine an object overlap," Paller said. "Thus, a vividly imagined event can leave a memory trace in the brain that's very similar to that of an experienced event. When memories are stored for perceived or imagined objects, some of the same brain areas are involved."

The study, published recently in the journal Psychological Science, showed that certain parts of the brain were involved in forming false memories, and different parts of the brain were responsible for creating true memories.

The key to remembering that something was imagined when we recall it is the context surrounding a memory, the research showed. If you remember who told you to imagine something, where it was, what was going on around you, the separation between what really happened and what you imagined becomes more distinct.

When a person makes these external connections to the memory, he engages the parts of the brain that lead to true memories.

False memories are only one part of studying how memory occurs, but researchers say they are excited about the prospects of connecting what they have learned in the laboratory to the real world.

"What we learn could be useful for people who make decisions outside [the lab] based on the memory of others," Paller told LiveScience. http://www.livescience.com/humanbiology/041028_Lost_Dreams.html

Where Dreams Are Made, ReallyBy Michael SchirberLiveScience Staff Writerposted: 28 October, 20047:00 a.m. ET

Analyzed as portents of the future and windows to the subconscious, dreams have fascinated human beings since the dawn of recorded history. Their purpose, from a strictly cognitive point of view, remains a puzzle.

But a rare instance of dream loss in a patient with localized brain damage may pinpoint the where, if not the why, of dreaming.

The case involves a 73-year-old woman, who was admitted to the emergency room for a sudden loss of vision and weakness on the left side of her body. She had suffered a stroke that had damaged a small area in the back of her brain where visual processing is done.

Her sight returned after a couple of days, but subsequently she could no longer recall any dreams. Prior to the stroke she typically would remember three of four dreams a week.

Doctors from the University Hospital of Zurich, Switzerland, studied the woman while she slept on several occasions over a six-week period. As reported in a recent online version of the Annals of Neurology, they found that she continued to exhibit rapid eye movement (REM), which typically occurs at the same time as dreaming.

Yet, when the doctors woke the patient during REM, she still reported no dreams. All other aspects of her sleeping state were normal, and she showed no signs of disorientation or memory loss while awake.

"We know that REM is generated in the brain stem," said Jerome M. Siegel of the Brain Research Institute at the University of California, Los Angeles, so these results confirm that dreaming originates from a separate brain region.

The woman’s stroke affected the inferior lingual gyrus, which is known to be important in recognizing faces and landmarks and in dealing with emotions. The authors suggest that this area plays a key role in the dream experience.

One possibility is that REM activity acts like an internal movie, but when the processing center is damaged, "the movie is still playing, but the patient is not watching it, or forgets that they watched it," Siegel said.