Learning Through Dreams

Researchers at Harvard University and Harvard Medical School conducted an experiment that indicates that dreaming during non-REM (rapid eye movement) sleep after performing a difficult task helps participants complete the activity more successfully after waking. (Scientists have only observed learning during non-REM sleep and not during REM sleep.) The researchers’ results also indicate that just thinking about the activity after first performing it does not help in later attempts to complete the task. These findings support earlier research indicating that sleep improves memory and learning.

“Task-related dreams may get triggered by the sleeping brain’s attempt to consolidate challenging new information and to figure out how to use it,” Dr. Robert Stickgold, study co-author, told ScienceNews about their results.

Researchers recruited 99 college students between the ages of 18 and 30 to participate in the study. For the experiment, the volunteers spent 60 minutes working individually to solve a 3-D virtual maze on a computer. During the activity, the participants performed several trials, and started the maze at a different location each time. In addition, while solving the maze, the participants were told to memorize the location of a specific tree’s location in the puzzle.

After spending an hour working on the maze, the participants were given a five-hour break. Half of the participants were instructed to take a nap, and the other half of participants were told to take part in quiet activities, such as reading or watching a video. For the nap group, the researchers fitted each participant with scalp sensors to monitor their brain activity while asleep. In addition, members of the napping group were asked about the content of their dreams just before they fell asleep, one minute after non-REM sleep, and at the end of their nap. Of the 50 participants in the nap group, four recounted dreaming about the maze activity. For the participants in the quiet activity group, each members was asked what they were thinking about at the beginning, middle, and end of the activity period.

After a lunch break and another period of quiet activity in which both groups of participants took part, the volunteers were asked to repeat the virtual maze activity. Those participants in the nap group who recalled dreaming about the maze in their sleep performed better the second time around in the maze activity and also found the tree that they had been told to remember quicker than other participants. All of the members of the nap group had been relatively unsuccessful in their attempts to complete the maze in the earlier session. The study authors suggest that tasks that are difficult and/or important to complete provoke memory processes in the brain required for learning to activate during sleep.

The scientists plan to continue their research into the connection between dreaming and learning. Future research plans include having study participants navigate through a more “exciting” virtual maze. The researchers are also interested in determining whether participants that have REM dreams about the maze during a normal full night’s sleep are able to better navigate the maze the next day.

The results of the scientists’ research were published in the April 22, 2010 online edition of the journal Current Biology. Study authors included Erin J. Wamsley, Matthew Tucker, Jessica D. Payne, Joseph A. Benavides, and Robert Stickgold.

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Researchers Link Circadian Rhythms to Learning and Memory

A properly-working circadian system helps Siberian hamsters remember things, such as where to find food sources. (Credit: Eric Wong/Shutterstock)

Researchers at Stanford University, led by senior research scientist Norman Ruby, recently discovered a link between circadian rhythms and learning and memory. The subject of the researchers’ study was the Siberian hamster (also called the dwarf hamster). Their research indicated that a correctly-functioning circadian system is necessary for the hamsters’ ability to remember what they have learned. Hamsters that had their circadian systems disabled were unable to consistently recall objects in their environment as compared to hamsters with working circadian systems.

The scientists developed a non-invasive procedure to disable the hamsters’ circadian systems by manipulating the hamsters’ exposure to light. First, the hamsters were exposed to two hours of bright light late at night. Next, the hamsters’ normal cycle of light/dark was delayed by three hours. After the treatment–the single treatment is enough to destroy the hamsters’ circadian system the hamsters’ normal cycle of light and dark was resumed. To test the hamsters’ memory and learning ability, the researchers used a standard test called a “novel object recognition task.” This technique takes advantage of a hamsters’ innate interest in exploring its environment.

The Novel Object Recognition Task

In this technique, two objects are placed in the opposite corners of a box. A hamster is then placed in the box. (As shown in the box marked “A”.) The hamster will typically examine the objects in its environment, spending an equal amount of time with the two objects. After a period of five minutes, the hamster is removed from the box, and one of the objects in the box is replaced with a new one. The hamster is then placed back into the box. (As shown in the box marked “B”.) A normal hamster with an unimpaired circadian system will spend time examining both objects, but will spend twice the amount of time at the new object. In comparison, a hamster with an impaired circadian system will spend the same amount of time at both objects, as it does not remember seeing one of the objects before.

This illustration shows the two steps of the novel object recognition task.

Previous research indicates that learning retention depends on the amount of a neurochemical called GABA in the brain. GABA controls brain activity. The biological clock manages an animal’s daily cycle of sleep and alertness by inhibiting different parts of the brain through the release of GABA. The hippocampus is the part of the brain that stores memories. When the hippocampus is over-inhibited by the release of too much GABA, the hippocampus becomes overwhelmed, and memories aren’t stored correctly.

Research Implications for Human Diseases

This research has implications for several diseases that impact learning and memory. For example, those affected with Down Syndrome don’t perform well on cognitive tests due to an over-inhibited brain during development. People with Alzheimer’s disease could also benefit from this study, as memory loss is also linked with an over-inhibited brain. In addition, as people age, their circadian systems begin to degrade and break down. This breakdown could explain short-term memory loss in the elderly.

In two separate studies focused on Down Syndrome and Alzheimer’s disease, mice exhibiting the symptoms of each were given pentylenetetrazole (PTZ), a GABA antagonist. PTZ works in the brain by blocking GABA from binding to synapses, which lets them continue to fire. This continual firing of the synapses keeps the brain in an excited state. In the mice, the PTZ counteracted the inhibitory affects of GABA, and improved their ability to learn and retain memories.

Ruby and his colleagues hypothesized that giving PTZ to hamsters with impaired circadian systems would see a similar improvement. The results of their experiment confirmed the researchers’ hypothesis–after being given PTZ, the impaired hamsters showed a definite improvement in their learning and memory skills.

The results of this study were published online October 1 in an early edition of the journal Proceedings of the National Academy of Sciences. Other researchers who contributed to the paper include co-authors H. Craig Heller, Calvin Hwang, Colin Wessells, Fabian Fernandez, Pei Zhang, and Robert Sapolsky.

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Adult Brains Can Rewire after a Stroke

A child’s brain has an amazing ability to adapt and change to new experiences it is very plastic. Over the past 25 years, researchers have found that an adults brain also has plasticity. Many times, its plasticity helps an adult master a new skill or adapt to a changing environment. Sometimes, the plasticity makes up for an injury.

A case study of a stroke patient adds to evidence proving that adult brains are capable of creating new neural pathways. The victim, known as BL, had a stroke that left him with a blind area in his upper left visual field. BL described how objects looked distorted in the lower left visual field, right below his blind area. Neuroscientists from Johns Hopkins University and Massachusetts Institute of Technology hypothesized that these distortions were caused by rewiring in the visual cortex, the part of the brain that processes visual information, to compensate for the stroke.

Dr. Daniel Dilks of MIT, and his colleagues tested their hypothesis. BL was shown basic shapes while he stared at another object. When they presented the shapes in his upper left visual field, he recorded seeing nothing. But when they presented the shapes just below his blind area, he recorded something different. Triangles appeared pencil-like. Circles appeared cigar-like. Squares appeared like rectangles. The shapes extended up into his blind area. His brain had rewired to use the part of the visual cortex that no longer received direct visual information.

The fMRI studies confirmed that the deprived visual cortex began to assume new properties that led to the visual distortions. “We discovered that it (the visual cortex) takes on new functional properties, and BL (the stroke victim) sees differently as a consequence of that cortical reorganization,” Dr. Daniel Dilks said.

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