How running preserves the memory

Exercise has long been known to combats stress, but a study by Brigham Young University suggests that it can also combat forgetfulness. The researchers found that running protects against the negative effects of stress on the hippocampus-the part of the brain responsible for learning and memory.

Within the hippocampus, memory formation and recall work best when the connections between neurons-synapses, are strengthened over time, a process called long-term potentiation (LTP). Chronic or prolonged stress, however, weakens the synapses and with them the LTP, negatively impacting memory.

The ideal situation for improving learning and memory would be to experience no stress and to exercise. To study the link between memory, stress and exercise, researchers divided mice into four groups: sedentary no stress, exercise no stress, exercise with stress, and sedentary with stress. The mice were then exposed to stress inducing situations, such as walking on an elevated platform or swimming in cold water, or put on a running wheel depending on their grouping.

To determine how the variables affected each group's memory, the researchers used electrophysiology to measure the LTP in the animals' brains. They found that the stressed mice who exercised had considerable higher LTP rates than those who had not exercised. The researchers also used a maze-running experiment to test the mice's memories. The stressed mice who exercised performed just as well as non-stressed mice who exercised.

Additionally, the exercising mice made significantly fewer memory errors in the maze than the sedentary mice. The findings suggest exercise is an effective way to protect learning and memory mechanisms from the negative cognitive impacts of chronic stress on the brain.
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Memory loss before Alzheimer's disease

A UCL-led team has developed a cognitive test to detect subtle memory deficits years before Alzheimer's disease symptoms develop. The study involved 21 people who carry the mutation for early onset Alzheimer's disease who have not shown any symptoms based on standard cognitive tests, alongside 14 controls. On average the study participants were seven years away from predicted onset of symptomatic disease.

The participants underwent a memory test with 30-minute recall, and were then checked seven days later to see if they still remembered. The authors found that people who were closest to the expected onset of symptoms could remember things after 30 minutes but then had forgotten things after seven days. The researchers say their findings demonstrate that memory formation wasn't the issue, so typical tests wouldn't identify any problems.

The researchers found a correlation between long-term forgetting and subjective memory complaints. This could be the earliest test to detect changes in someone's cognition that lead to Alzheimer's disease. The study's first author, Dr. Philip Weston (UCL Dementia Research Centre), said: "The study would appear to significantly advance the knowledge of the earliest cognitive changes in Alzheimer's, and offers a new useful approach to testing people both in drug trials and in the clinic."
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Roles of brain protein

A protein called AKT, is ubiquitous in brain tissue and instrumental in enabling the brain to adapt to new experiences and lay down new memories. AKT comes in three distinct varieties residing in different kinds of brain cells and affecting brain health in very distinct ways. It is a central protein that has been implicated in a bevy of neurological diseases.

Discovered in the 1970s and known best as an "oncogene" (one that, when mutated, can promote cancer), AKT has more recently been identified as a key player in promoting "synaptic plasticity," the brain's ability to strengthen cellular connections in response to experience. AKT is one of the first proteins to come up after observing scary objects, it is a central switch that turns on the memory factory.

For the study, Hoeffer's team silenced the three different isoforms, or varieties, of AKT in mice and observed their brain activity. They made a number of key discoveries: AKT2 is found exclusively in astroglia, the supportive, star-shaped cells in the brain and spinal cord that are often impacted in brain cancer and brain injury.

 AKT1 is ubiquitous in neurons and appears to be the most important form in promoting the strengthening of synapses in response to experience-memory formation. (This finding is in line with previous research showing that mutations in AKT1 boost risk of schizophrenia and other brain disorders associated with a flaw in the way a patient perceives or remembers experiences.)
AKT3 appears to play a key role in brain growth, with mice whose AKT3 gene is silenced showing smaller brain size.
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Memory depends on subtle brain signals

The fragrance of hot pumpkin pie can bring back pleasant memories of holidays past, while the scent of an antiseptic hospital room may cause a shudder. The power of odors to activate memories both pleasing and aversive exists in many animals. The intricate biochemical mechanism for storing scent-associated memories differs slightly from a less-understood mechanism for erasing unnecessary memories.

Understanding how brains actively erase memories may open new understanding of memory loss and aging, and open the possibility of new treatments for neurodegenerative disease. In multiple ways, the processes of forgetting and remembering are alike. In fruit fly models of odor-associated learning, both the saving and erasure of memories involves
dopamine activation of the brain cells. This clue in flies is important for understanding the human brain.

The olfactory systems of flies and humans are actually quite similar in terms of neuron types and their connections.activation of the neurons causes them to make an identical messenger molecule,  Tcyclic AMP, leading to a cascade of activity within the cell, either building or breaking down memory storage.

The research team discovered one G protein, called G alpha S, that latched on to a neural dopamine receptor called dDA1, associated with memory formation. They found a different G protein, called G alpha Q, linked up with a nearby dopamine receptor called Damb, associated with the machinery of forgetting. The next question was whether those two different G proteins could be controllers of the fly brain's memory machinery.

To find out, the researchers silenced genes involved in the production of the G alpha Q protein in the flies. The flies with the protein silenced were exposed to odors in aversive situations and sent through mazes to see how well they remembered to turn away in the presence of the scent. It appears in flies that some level of forgetting is a constant, healthy process.

There is a slow process that whittles away memories, and it continues whittling them away unless another part of the brain signals the memory is important and overrides it.It may be that the process of acquiring and forgetting memories ebbs and flows in a state of balance. Important memories like the taste of mom's pumpkin pie might be forever retained, but trivialities like what you wore ten years ago can fade into oblivion without consequence.
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How sleep helps the brain

Sleep contributes to the brain's ability to change and reorganise itself and this can help people with learning and memory disorders. Researchers used cutting edge techniques to record activity in the dendrites. Dendrite is parts of brain cells that is responsible for keeping new information.

They discovered that activity in dendrites increases when we sleep, and that this increase is linked to specific brain waves that are seen to be key to how we form memories.

Human brain have the ability to change and adapt based on our different experiences, sleep is very important for the changes. A large proportion of these changes may occur during very short and repetitive brain waves known as spindles.

Sleep spindles have been associated with memory formation in humans. During spindles, specific pathways are activated in dendrites, allowing memories to be reinforced during sleep.
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Development of memory is a gradual process

The hippocampus, a brain structure that is central to learning and memory, does not complete its maturation until adolescence. The hippocampus, a region deep inside the brain, plays a central role for memorization and recall of details, as well as general memory performance.

Using high-resolution imaging the scientists were able to obtain information about the sizes of different subregions of the hippocampus.
The study involved many children and adolescents aged 6 to 14 years as well as young adults aged 18 to 26 years.

After checking the images, they realized that the age differences in the subregions do not follow a standard pattern and a lot is still happening beyond the age of six. A special task assessed whether the participants remember details of objects or their general characteristics.

Participants were shown some images, researchers added minor changes to the objectives during second display, participants were asked to indicate whether they had seen the respective images before and indicate any changes and differences between the first and the second image.

The scientists also examined how the
development of the hippocampal subregions is associated with age. In particular, two subregions showed age-related differences linked to differences in memory for details: the dentate gyrus, whose function consists the separation of features so that they can be recalled separately, and the entorhinal cortex, whose cortical connections contribute to memory formation, stabilization, and retrieval.

The assumption that these two subregions and the hippocampus as a whole only complete their maturation in adolescence has changed perspective on the development of learning and memory. Using high-resolution magnetic resonance imaging. This new study shows that the maturation process lasts until the fourteen years.
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