How Are Memories Made & Stored?

How Are Memories Made & Stored?

What exactly is a memory and how do they manifest inside our brains?  Which part/s of our brain are responsible for making memories?  And how does our brain know how to associate the fragrance of a perfume, the sight of waves crashing against a shoreline, or that song from the 1980s with a memory that can mentally transport you to another time?

The longest living cells in the body are brain cells, which can last us an entire lifetime.  25 million new cells are produced by the body every single second,  which means that within 13 seconds, more cells are produced in one person than there people in the USA!  

The term ‘episodic memory’ has been coined by neuroscientists to describe the ability to store and retrieve memories.  The hippocampus, although only small and buried deep inside the brain, provides the connection hub for the rest of the brain.  If the hippocampus is damaged it can cause profound memory loss and spatial navigation problems.  This tiny area of the brain has been under much scrutiny by scientists since the 1950s.

Dr Matias Ison and Professor Rodrigo Quian Quiroga, from the University of Leicester in the UK and Ronald Reagan UCLA Medical Center, CA, have published a study in the journal Neuron, that has shed new light on how memories are formed and the important role that the medial temporal lobe and hippocampus plays.  The scientists in Leicester have been able to observe the speed of neurons forming new associations in epilepsy patients who were undergoing brain surgery.  Each participant was shown images of family members, famous actors, athletes and places, such as the Eiffel Tower and the White House.  Then they were shown images where composite photos were created from the individual images previously shown: for example Clint Eastwood in front of the Leaning Tower of Pisa.   

The researchers noticed that the composite images caused those neurons that fired for just one of the images to fire for both, even after only being seen by the participant only once.  What has proved interesting is that the same medial temporal lobe neurons were activated when the participant saw either a composite photo or Clint Eastwood on his own or the leaning Tower of Pisa on its own. 

“It was impressive to see how individual neurons signaled the learning of new contextual associations between people and places and that the changes in firing could occur just after one instance,” said Dr. Ison. “this was also compatible with basic mechanisms underlying episodic memory formation.”

Whilst the cortex is bigger than the hippocampus it helps us to process other elements that use C22_01_1200_1200_Neuro-Anatomical-Brain-8-part our senses.  Scientists now believe that the hippocampus helps to create order out of these snapshots and helps to recall them as memories.  The brain cortex could be thought of as the library whilst the hippocampus as the librarian.

The brain uses more than 25% of the body’s oxygen intake.  The hippocampus is sensitive to the body’s oxygen levels and can be damaged as a result of a heart attack, respiratory failure, sleep apnea, carbon monoxide poisoning or near drowning.  Damage can also be caused by chronic epilepsy seizures and sometimes hepes encephalitis.  It is also one of the first areas in the brain to show damage due to Alzheimer’s disease.  Studies have shown that hippocampal atrophy can also be caused by stress.  For example Post Traumatic Stress Disorder (PTSD) and childhood abuse can invoke a mechanism which is believed to involve serotonin and glucocorticoids, resulting in neuropsychological conditions.  Magnetic Resonance Imaging (MRI) can also cause a reduction in volume of the hippocampus of both combat PTSD victims and child abuse victims. 

C40_01_1200_1200_Physiology-of-Nerves-Series-5-models-metal-boardTraumatic experience can have long term repurcussions on the structure and function of the brain. 

A scientific project at Lawrence Livermore National Laboratory LLNL and Stanford University to develop an implantable neural device that wil be able to stimulate and record neurons within the brain to help resotre memory.  They hope to track neural activity and to stimulate types of therapy aimed at restoring memory.

“Currently, there is no effective treatment for memory loss caused by a condition such as traumatic brain injury,” said LLNL’s Satinderpall Pannu, project leader and director of the LLML’s Center for Bioengineering. 

Traumatic brain injury has affected in excess of 270,000 military service personnel since 2000 and often associated with severe memory loss.

Have you worked with Alzheimer’s patients or those suffering from a form of traumatic brain injury?  What rehabilitation methods have you used to help your patients? 

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