Trevor Ponder Human Memory

The brain cells that fire when a person watches a brief film clip are triggered again when the person thinks back on that imagery a few minutes later, a new study shows. The research offers insights into how the brain summons up past experiences and may also provide clues to brain disorders, like Alzheimer’s disease, that harm short-term memory.

Scientists have known for decades that memories are often processed and retrieved by the hippocampus, a curved structure deep in the brain. But exactly how memories are recorded and recalled remains a mystery.

Dr. Itzhak Fried, a professor of neurosurgery at the University of California, Los Angeles, has been exploring the mechanisms of memory at the single-neuron level in the human brain. For the past 10 years, his research has focused on patients with severe epilepsy who have many tiny electrodes implanted in their brains. The electrodes are used to pinpoint seizure-causing brain regions for surgical removal, but they can also provide information about how individual brain cells process memories.

In his latest study, published in the online edition of Science on September 4, 2008, Dr. Fried and colleagues at the Weizmann Institute of Science in Israel monitored electrode recordings of hundreds of neurons while patients watched a series of film clips and then later recalled them. Thirteen patients participated in a total of 43 viewing and recall sessions. The study was funded in part by NIH’s National Institute of Neurological Disorders and Stroke (NINDS).

The patients were shown about a dozen brief clips, each lasting about 5 to 10 seconds, of famous people, characters, landmarks or activities. The clips included segments of TV shows like The Simpsons and Seinfeld, portions of a speech by Martin Luther King, the Golden Gate Bridge and the famous Hollywood sign. Each clip was replayed a few times during each viewing session. After viewing sessions, the patients engaged in a different task for a few minutes. They were then asked to think about the video clips they’d seen and say aloud which clips came to mind.

During the videos, more than half of the monitored neurons had a significant response to one or more clips, and these neurons became reactivated each time those clips were replayed. Later, as the clips were remembered, the same neurons fired again. In general, there was a 2-second lag between neuron firing and verbal reporting of remembered clips.

For example, a neuron located near the hippocampus in one patient showed a powerful response each time a clip from The Simpsons appeared. It fired with less intensity when Seinfeld was shown and remained essentially silent during 46 other clips. When the patient later thought about the Simpsons clip, the neuron fired for several seconds but had little or no response to other memories. In all the patients, several neurons in and around the hippocampus showed similar, selective responses to different film clips.

It’s not clear exactly what aspects of the clips triggered the cells’ responses. Nevertheless, this study adds to a growing body of evidence that neurons in the brain’s memory centers can play a dual role, responding first to sensory input and then re-activating when that experience is later remembered.

==================================================
Learn more in Trevor Ponder’s training programs:
http://www.memoryonfire.com – audio book
http://www.elementsofmemory.com – PDF book
==================================================

Brain Facts hippocampus, memory cells

Some people are better than others at remembering what they have just seen — holding mental pictures in mind from moment to moment. An individual’s capacity for such visual working memory can be predicted by his or her brainwaves, researchers funded by the NIH’s National Institute of Mental Health have discovered.

A key brain electrical signal leveled off when the number of objects held in mind exceeded a subject’s capacity to accurately remember them, while it continued to soar in those with higher capacity, report University of Oregon psychologist Edward Vogel, Ph.D., and graduate student Maro Machizawa.

Analogous to a computer’s RAM, working memory is the ever-changing content of our consciousness. It’s been known for years that people have a limited capacity to hold things in mind that they’ve just seen, varying from 1.5 to 5 objects. “Our study identifies signals from brain areas that hold these visual representations and allows us to coarsely decode them, revealing how many objects are being held and their location in the visual field,” explained Vogel.

To find out if the amplitude of detectable signals reflects the number of objects held in visual memory, the researchers presented 36 subjects with a series of trials containing an increasing number of objects. Subjects briefly viewed a picture containing colored squares, followed by a one-second delay, and then a test picture. They pressed buttons to indicate whether the test picture was identical to — or differed by one color — from the one seen earlier. The more squares a subject could correctly identify having just seen, the greater his/her visual working memory capacity. Subjects averaged 2.8 squares.

==================================================
See for yourself by trying Trevor Ponder’s training programs:
http://www.memoryonfire.com/memoryonfireaudio.html – audio book
http://www.elementsofmemory.com/elementsbook.html – PDF book
==================================================

Electrodes on the scalp recorded neural activity during the one-second delay to pinpoint signals reflecting activity of brain areas involved in holding the images in working memory. Asking subjects to remember just one of two sets of colored squares that appeared on the left and right sides of the screen revealed signals near the opposite rear side of the head as emanating from the brain area involved.

The researchers found that the more squares a subject correctly identified, the higher the spike of corresponding brain activity — up to a point. Amplitude of the signal for correct trials was much higher than incorrect ones, suggesting that the delay activity specifically reflects the maintenance of successful representations in visual memory. Neural activity of subjects with poorer working memory scores leveled off early, showing little or no increase when the number of squares to remember increased from 2 to 4, while those with high capacity, who correctly remembered more squares, showed large increases.

Using a similar task with functional magnetic resonance imaging (fMRI), a research team at Vanderbilt University reports in the same issue of Nature that the posterior parietal cortex, an area at the top rear part of the brain, is the brain area responsible for holding representations in visual working memory — and likely source of the signal in the Oregon study.

“Simply by measuring the amplitude increase across memory array sizes, we can accurately predict an individual’s memory capacity,” said Vogel.

Since working memory capacity is strongly predictive of performance on a broad array of cognitive abilities — reasoning, language, flexible problem solving — Vogel foresees the physiological measure as finding applications in assessing individuals who are behaviorally or verbally impaired, such as in cases of stroke or paralysis. The technique has also been used to study development of cognitive abilities in pre-verbal children.

Memory Techniques mental pictures, visual memory

Hoping to improve your tennis serve? It’s probably better to catch
a few winks than load up on java after a lesson, results of a
NIMH-supported study suggest. Caffeine impaired such motor learning
and verbal memory, while an afternoon nap benefited all three types
of learning tested by Sara Mednick, Ph.D., and colleagues at the
University of California, San Diego. The researchers report on
their findings in the November issue of Behavioural Brain Research.

Ninety percent of Americans use caffeine daily, some substituting
it for sleep. While the stimulant enhances alertness and
concentration, it’s been unclear whether it also helps learning and
memory. By contrast, daytime naps, like nighttime sleep, benefit
both alertness and memory, Mednick and colleagues have shown in a
series of studies.

In this first head-to-head day-time comparison, 61 participants
trained in the morning on verbal memory, motor, and perceptual
learning tasks. After lunch, one group napped (60-90 min), while
two other groups listened to a book on tape and received a pill
containing either the caffeine equivalent of a little less than a
Tall Starbucks brewed coffee (200mg) or a placebo. Later in the
afternoon, the three groups were tested to see how well they had
learned the tasks.
==================================================
Learn more in Trevor Ponder’s training programs:
http://www.memoryonfire.com/memoryonfireaudio.html – audio book
http://www.elementsofmemory.com/elementsbook.html – PDF book
==================================================

Findings of This Study

The nap group performed significantly better on a finger tapping
motor task and in recalling words, than the caffeine group. The nap
group also trumped the other groups on a texture discrimination
task of perceptual learning. The placebo group performed better
than the caffeine group on all three tasks. Curiously, just
thinking that the pill might contain caffeine — the placebo effect
— helped as much as a nap on the motor task.
Significance

Evidence suggests that caffeine interferes with tasks that require
processing explicit, as opposed to implicit, information – like
recalling a specific word, versus remembering how to type or ride a
bike. Studies show that consolidation of such explicit verbal
memory during sleep depends on lowered levels of the chemical
messenger acetylcholine in the brain’s memory hub. Yet, by blocking
activity of a natural sedative chemical, caffeine boosts
acetylcholine in this hub.
==================================================
Learn more in Trevor Ponder’s training programs:
http://www.memoryonfire.com/memoryonfireaudio.html – audio book
http://www.elementsofmemory.com/elementsbook.html – PDF book
==================================================

“This increase in acetylcholine by caffeine may impair the
consolidation process by blocking replay of new memories,” proposes
Mednick. “Consistent with this, we found that the greater the
explicit component of each task, the worse the caffeine group
performed.”

What’s Next?

“Such an impairment of performance runs counter to society’s
assumption that caffeine typically benefits cognitive performance,”
she notes. “Apparent improvements with caffeine might actually
reflect a relief from withdrawal symptoms. Just as no medicinal
alternative to a good night’s rest has been discovered, so too
caffeine, the most common pharmacological intervention for
sleepiness, may not be an adequate substitute for the memory
enhancements of daytime sleep, either.”

Mednick and colleagues are using new pharmacological agents found
to selectively enhance particular stages of nighttime sleep to see
if they can enhance memory consolidation during daytime naps. Brain
imaging will pinpoint effects on neural circuits. These studies of
pharmacologically enhanced naps could lead to improved treatments
for memory impairment in mental disorders, based on manipulations
of sleep, say the researchers.

==================================================
http://www.memoryonfire.com/memoryonfireaudio.html
http://www.elementsofmemory.com/elementsbook.html
http://trevorponder.com
==================================================

…………………………….

Memory and Food caffeine, memory food