Alzheimer’s Muddles Memory of How Things Work

Which is bigger, a key or an ant? That question might be easy for you to answer quickly, but it could be a little more confusing for a person with Alzheimer’s.

The most obvious trait of the mind-ruining disease is memory loss, with patients forgetting once-familiar people, places and experiences. New research shows how this mental deterioration extends to semantic memory, which has more to do with remembering facts and concepts and underlies a basic understanding of how things works.

For their study, researchers recruited 70 cognitively healthy people, 27 patients with Alzheimer’s 25 patients with mild cognitive impairment (MCI), often considered a precursor to dementia. All were tested on their ability to make size judgments about two pictures shown to them — the premise being that the bigger the difference in size between two objects, the faster a person would be able to answer the question.

"If you ask someone what is bigger, a key or an ant, they would be slower in their response than if you asked them what is bigger, a key or a house," researcher Terry Goldberg, of the Hofstra North Shore-LIJ School of Medicine, said in a statement.

This held true in the experiments, but the MCI and Alzheimer’s patients had much more trouble when asked to respond to a task with small size differences.

The experiment was then tweaked so that the participants were shown pictures of a small ant and a big house or a big ant and a small house. The MCI and Alzheimer’s patients did not have a problem making judgments about the small ant and big house, but had trouble with the more incongruent set. They were confused about which object was actually larger when shown a big ant and a small house, and were more likely to answer incorrectly or take longer to arrive at a response, the researchers said.

Goldberg said the findings indicate “that something is slowing down the patient and it is not episodic memory but semantic memory.”

The team will continue to study these patients over time to see if these semantic problems get worse as the disease advances.

PredictAD software promises early diagnosis of Alzheimer’s

Scientists at VTT Technical Research Centre in Finland have developed new software called PredictAD that could significantly boost the early diagnosis of Alzheimer’s disease.

The comparative software contrasts patient’s measurements with those of other patients kept in large databases, then visualizes the status of the patient with an index and graphics.

The support system and imaging methods were developed by VTT and Imperial College London.

The researchers used material compiled in the U.S. by the Alzheimer’s Disease Neuroimaging Initiative based on the records of 288 patients with memory problems. Nearly half of them, or 140 individuals, were diagnosed with Alzheimer’s disease on average 21 months after the initial measurements, which is about the same as the current European average of 20 months.

The researchers concluded that half of the patients could have been diagnosed with the disease around a year earlier, or nine months after the initial measurements. They say the accuracy of the predictions was comparable to clinical diagnosis.

There are several advantages of an early diagnosis of Alzheimer’s. It can delay institutionalization and slow down the progress of the disease. It is also advantageous from the clinical trials perspective because if patients caught early can be included in the trials, treatment is likely to be more effective.

Working towards the same goal, researchers at Lancaster University in the U.K. recently developed an eye test method to detect early signs of Alzheimer’s.

The VTT researchers will spend the next five years carrying out the test at memory clinics in Europe. They also hope to expand its scope to include other illnesses that cause dementia. According to 2010 figures, an estimated 35.6 people live with dementia worldwide, and that number is expected to rise to 65.7 million by 2030.

The findings of the research were published in the Journal of Alzheimer’s Disease in November 2012. VTT cooperated with the University of Eastern Finland and Copenhagen University Hospital Rigshospitalet on this project.

Kim Peek, The Real Rain Man

Kim Peek, who lent inspiration to the fictional character Raymond Babbitt—played by Dustin Hoffman—in the movie Rain Man, was a remarkable savant. A savant is an individual who—with little or no apparent effort—completes intellectual tasks that would be impossible for ordinary people to master.

Kim Peek’s special abilities started early, around the age of a year and a half. He could read both pages of an open book at once, one page with one eye and the other with the other eye. This style of reading continued until his dead in 2009. His reading comprehension was impressive. He would retain 98 percent of the information he read. Since he spent most of his days in the library with his dad, he quickly made it through thousands of books, encyclopedia and maps. He could read a thick book in an hour and remember just about anything in it. Because he could quickly absorb loads of information and recall it when necessary, his condition made him a living encyclopedia and a walking GPS. He could provide driving directions between almost any two cities in the world. He could also do calendar calculations (“which day was June 15, 1632?”) and remember old baseball scores and a vast amount of musical, historical and political facts. His memory abilities were astounding.

Unlike many individuals with savant syndrome, Kim Peek was not afflicted with autistic spectrum disorder. Though he was strongly introverted, he did not have difficulties with social understanding and communication. The main cause of his remarkable abilities seems to have been the lack of connections between his brain’s two hemispheres. An MRI scan revealed an absence of the corpus callosum, the anterior commissure and the hippocampal commissure, the parts of the neurological system that transfer information between hemispheres. In some sense Kim was a natural born split-brain patient.

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The Persistence of Memory in Mice

It’s frequently said that scent is the sense most powerfully tied to memory. For mice, it turns out, that’s especially true—at least when it comes to a sniff of the urine of potential mates.

According to a study published in Science by researchers from the University of Liverpool, female mice exposed to the potent pheromone darcin (found in male mouse urine) just a single time will repeatedly return to the exact site of exposure up to 14 days later, even after the pheromone is taken away.

“We have shown that a male sex pheromone in mice makes females …remember exactly where they encountered the pheromone and show a preference for this site for up to two weeks afterwards,” said lead author Sarah Roberts in a statement. “Given the opportunity, they will find that same place again, even if they encountered the scent only once and the scent is no longer there.”

“This attraction to the place they remember is just as strong as attraction to the scent itself,” said co-author Jane Hurst. “Darcin, therefore, induces mice to learn a spatial map of the location of attractive males and their scents, to which they can easily return.”

The researchers determined that the important factor was the pheromone darcin because the same results occurred when a synthetic version of the chemical was put into a petri dish on its own. Additionally, when the female mice were exposed to female urine instead, there was no indication of a preference, because darcin isn’t present in the females’ urine.

Interestingly, the pheromone also produced a powerful effect on another group of mice: competitor males. When they were used in the same experiment, they also demonstrated a preference for the place where they remembered smelling other males’ urine, but they didn’t show this type of spatial memory when the urine used was their own. The researchers speculate that this is because of a motivation to linger near the site and mark the territory with their own pheromone scent, to advertise their availability to female mates.

The scientists speculate that this lingering affinity for the memory of urine is used by the mice as a mental shortcut for finding mates. In a natural setting (instead of cages), rather than having to smell the pheromones from a distance and then track them to the source, they can simply camp out by urine deposited by a potential mate and wait for their likely return.

Western University-led research debunks the IQ myth

After conducting the largest online intelligence study on record, a Western University-led research team has concluded that the notion of measuring one’s intelligence quotient or IQ by a singular, standardized test is highly misleading.

The findings from the landmark study, which included more than 100,000 participants, were published in the journal Neuron.

Utilizing an online study open to anyone, anywhere in the world, the researchers asked respondents to complete 12 cognitive tests tapping memory, reasoning, attention and planning abilities, as well as a survey about their background and lifestyle habits.

"The uptake was astonishing," says Owen, the Canada Excellence Research Chair in Cognitive Neuroscience and Imaging and senior investigator on the project. "We expected a few hundred responses, but thousands and thousands of people took part, including people of all ages, cultures and creeds from every corner of the world."

The results showed that when a wide range of cognitive abilities are explored, the observed variations in performance can only be explained with at least three distinct components: short-term memory, reasoning and a verbal component.

No one component, or IQ, explained everything. Furthermore, the scientists used a brain scanning technique known as functional magnetic resonance imaging (fMRI), to show that these differences in cognitive ability map onto distinct circuits in the brain.

With so many respondents, the results also provided a wealth of new information about how factors such as age, gender and the tendency to play computer games influence our brain function.

"Regular brain training didn’t help people’s cognitive performance at all yet aging had a profound negative effect on both memory and reasoning abilities," says Owen.

Hampshire adds, “Intriguingly, people who regularly played computer games did perform significantly better in terms of both reasoning and short-term memory. And smokers performed poorly on the short-term memory and the verbal factors, while people who frequently suffer from anxiety performed badly on the short-term memory factor in particular”.

To continue the groundbreaking research, the team has launched a new version of the tests at http://www.cambridgebrainsciences.com/theIQchallenge

"To ensure the results aren’t biased, we can’t say much about the agenda other than that there are many more fascinating questions about variations in cognitive ability that we want to answer," explains Hampshire.

(Image by Lasse Kristensen/Shutterstock)

REM sleep enhances emotional memories

Witnessing a car wreck or encountering a poisonous snake are scenes that become etched in our memories.

But how do we process and store these emotional scenes so that they’re preserved more efficiently than other, more neutral memories?

In a new study published recently in “Frontiers in Integrative Neuroscience,” University of Notre Dame researchers Jessica Payne and Alexis Chambers found that people who experienced rapid eye movement (REM) sleep soon after being presented with an emotionally-charged negative scene — a wrecked car on a street, for example — had superior memory for the emotional object compared to subjects whose sleep was delayed for at least 16 hours. This increased memory for the emotional object corresponded with a diminished memory for the neutral background of the scene, such as the street on which the wrecked car was parked.

These results suggest that the sleeping brain preserves in long-term memory only those scenes that are emotionally salient and aid in adaptation.

“Our results suggest that REM sleep, which has long been thought to play a role in emotional processing and emotional memory, helps us selectively preserve in memory only what is most important and perhaps beneficial to survival,” says Payne, a Notre Dame assistant professor of psychology who specializes in sleep’s impact on memory, creativity and the ability to process new ideas.

We know that emotional events occupy a privileged position in our memories — they shape our personalities, represent defeats and achievements, mark milestones in our lives and often drive anxiety and mood disorders.

This study shows that the sleeping brain doesn’t just consolidate all recently encountered information. It appears to select for consolidation only the most emotional part of the experience, and the evidence suggests that REM sleep critically modulates memory for highly arousing emotional information.

(Image: iStock)

Long-Term Anabolic-Androgenic Steroid Use May Severely Impact Visuospatial Memory

The long-term use of anabolic-androgenic steroids (AAS) may severely impact the user’s ability to accurately recall the shapes and spatial relationships of objects, according to a recent study conducted by McLean Hospital and Harvard Medical School investigators.

In the study, published online in the journal Drug and Alcohol Dependence, McLean Hospital Research Psychiatrist Harrison Pope, MD, used a variety of tests to determine whether AAS users developed cognitive defects due to their admitted history of abuse.

"Our work clearly shows that while some areas of brain function appear to be unaffected by the use of AAS, users performed significantly worse on the visuospatial tests that were administered. Those deficits directly corresponded to their length of use of anabolic-androgenic steroids," explained Pope. "Impaired visuospatial memory means that a person might have difficulty, for example, in remembering how to find a location, such as an address on a street or a room in a building… We are worried that with higher doses of AAS and longer periods of lifetime exposure, some people might even eventually develop visuospatial deficits similar to those sometimes seen in elderly people with dementia, who can easily become lost or disoriented."

Brain cells activated, reactivated in learning and memory

Memories are made of this, the song says. Now neuroscientists have for the first time shown individual mouse brain cells being switched on during learning and later reactivated during memory recall. The results are published Dec. 13 in the journal Current Biology.

We store episodic memories about events in our lives in a part of a brain called the hippocampus, said Brian Wiltgen, now an assistant professor at the Center for Neuroscience and Department of Psychology at the University of California, Davis. (Most of the work was conducted while Wiltgen was working at the University of Virginia.) In animals, the hippocampus is important for navigation and storing memories about places.

"The exciting part is that we are now in a position to answer a fundamental question about memory," Wiltgen said. "It’s been assumed for a long time that the hippocampus is essential for memory because it drives reactivation of neurons (nerve cells) in the cortex. The reason you can remember an event from your life is because the hippocampus is able to recreate the pattern of cortical activity that was there at the time."

According to this model, patients with damage to the hippocampus lose their memories because they can’t recreate the activity in the cortex from when the memory was made. Wiltgen’s mouse experiment makes it possible to test this model for the first time.

Lithium rescues synaptic plasticity and memory in Down syndrome mice

Down syndrome (DS) patients exhibit abnormalities of hippocampal-dependent explicit memory, a feature that is replicated in relevant mouse models of the disease. Adult hippocampal neurogenesis, which is impaired in DS and other neuropsychiatric diseases, plays a key role in hippocampal circuit plasticity and has been implicated in learning and memory. However, it remains unknown whether increasing adult neurogenesis improves hippocampal plasticity and behavioral performance in the multifactorial context of DS. We report that, in the Ts65Dn mouse model of DS, chronic administration of lithium, a clinically used mood stabilizer, promoted the proliferation of neuronal precursor cells through the pharmacological activation of the Wnt/β-catenin pathway and restored adult neurogenesis in the hippocampal dentate gyrus (DG) to physiological levels. The restoration of adult neurogenesis completely rescued the synaptic plasticity of newborn neurons in the DG and led to the full recovery of behavioral performance in fear conditioning, object location, and novel object recognition tests. These findings indicate that reestablishing a functional population of hippocampal newborn neurons in adult DS mice rescues hippocampal plasticity and memory and implicate adult neurogenesis as a promising therapeutic target to alleviate cognitive deficits in DS patients.