Memories need to be "Turned on" and are enhanced by emotion

The definition of "memory" for some may revolve around studying for a test or simply recalling where they last put their car keys. However, according to Pennsylvania State University psychologists, memory is far more selective than previously thought - people may have to "turn on" memories in order to recall even the simplest details.

According to the study, attribute amnesia occurs when a person uses a piece of information to perform a task, but is then unable to report specifically what that information was as little as one second later.

For humans to recall events, facts or processes, they have to be committed to memory. 

The process of forming a memory involves encoding, storing, retaining and subsequently recalling information and past experiences.

It is commonly believed that you will remember specific details about the things you're attending to, but our experiments show that this is not necessarily true.

In some cases, people have trouble remembering even very simple pieces of information when they do not expect to have to remember them.

The research team tested the memories of 100 undergraduate students, divided into several groups. Each group performed a variation of the experiment in order to replicate the results for different kinds of information, such as numbers, letters or colors.

Trial participants were shown four characters on a screen arranged in a square - for example three numbers and one letter - and were asked to report which corner a specific letter was in after they disappeared from the screen. At this stage of the task, the participants rarely made an error.

After this task had been repeated numerous times, the participants were asked an unexpected question - to identify which of the four characters they had just seen had also appeared on the previous screen. 

Only 25% of participants identified the correct character - the same percentage as would be expected from a random guess.

Similar results were obtained when participants were asked to locate odd numbers, even numbers and colors.

This result is surprising because traditional theories of attention assume that when a specific piece of information is attended, that information is also stored in memory and therefore participants should have done better on the surprise memory test.

The researchers have labeled the phenomenon they have witnessed as "attribute amnesia," as they reported in the published article featuring in the online journal Psychological Science.

Attribute amnesia occurs when a person uses a piece of information to perform a task, but is then unable to report specifically what that information was in as little as one second later.

The information we asked them about in the surprise question was important, because we had just asked them to use it. It was not irrelevant to the task they were given.

When the question was repeated in subsequent trials, and no longer a surprise, the participants answered significantly more correct answers with the average of correct answers between 65% and 95% across the different experiments.

Memory can be described as the process of retaining information over time or the ability to use past experiences to determine a future path. 

For this experiment, the researchers point out, people's expectations play an important role in determining what they remember, even for information they are specifically using. 

"It seems like memory is sort of like a camcorder, if you don't hit the 'record' button on the camcorder, it's not going to 'remember' what the lens is pointed at. But if you do hit the 'record' button - in this case, you know what you're going to be asked to remember - then the information is stored."

The researchers suggest that this selective memory storage might be a useful adaptation because it prevents the brain from remembering information that is probably not important. The researchers plan to continue this line of research as they study whether people are aware of their own lack of memory.

Emotion 'encodes' memory

Another study published in the journal Nature and conducted at New York University, also highlights this adaptive nature of memory: that it continually updates itself according to what knowledge may be important in the future.

This new study indicates that human memory has, in effect, a just-in-case file, keeping seemingly trivial sights, sounds and observations in storage for a time where they may become useful.

The study used mild electric shocks to create apprehension and measured how the emotion affected memory of previously seen photographs.

Those who took the memory test immediately after watching scrolling images of tools and animals remembered as many tools as they did animals; the shocks had no apparent effect. 

But those who took the test 6 hours or a day later recalled about 7% more items from the "shocked" category. For example, they remembered more tools if they had been zapped while viewing tool images.

"The emotional experience of the shocks strengthened or preserved the memories of things that, at the time they were encoded, seemed mundane. At least when it's tested hours or a day later."

Eating walnuts to boost memory?

A factor that has been found to improve performance and memory on cognitive function tests in a new study is swapping your daily snack for a handful of walnuts.

According to researchers at the David Geffen School of Medicine at the University of California, Los Angeles, cognitive function was consistently greater in adult cognitive function test participants that consumed walnuts, regardless of age, gender or ethnicity.

It is exciting to see the strength of the evidence from this analysis across the USA population supporting the previous results of animal studies that have shown the neuroprotective benefit from eating walnuts; and it's a realistic amount - less than a handful per day (13 g).

The study adds to a growing body of research surrounding walnuts' positive effect on reducing cognitive impairment and overall brain health, which includes the possible beneficial effects of slowing or preventing the progression of Alzheimer's disease in mouse models.

The study indicates that there are numerous possible active ingredients in walnuts that may be contributing factors in protecting cognitive functions. This includes the high antioxidant content of walnuts, the combination of numerous vitamins and minerals, the significant source of alpha-linolenic acid and a plant-based omega-3 fatty acid with heart and brain-health benefits.

It isn't every day that research results in such simple advice - eating a handful of walnuts daily as a snack, or as part of a meal, can help improve your cognitive health.

Recently we reported on a study that finds a 30-minute nap straight after exposure to new information may boost infants' memory.

References:

1.     Emotional learning selectively and retroactively strengthens memories for related events, Joseph E Dunsmoor, et al., Nature, doi:10.1038/nature14106, published online 21 January 2015, abstract.

2.     A cross sectional study of the association between walnut consumption and cognitive function among adult US populations represented in NHANES, L. Arab, et al., JNHA, published online 16 December 2014, abstract.

3.     Penn State news release, accessed 22 January 2015, via EurekAlert.

4.     Edelman news release, accessed 22 January 2015, via EurekAlert.

5.     Additional source: The New York Times, How the brain stores trivial memories, just in case, accessed 22 January 2015.