The science of memory


THE two-letter initials H.M. are the most famous in the history of the brain sciences. Henry Gustav Molaison was a mechanic in Connecticut and suffered from chronic epilepsy since his childhood. In 1953, a neurosurgeon removed a tiny portion of his midbrain, known as the hippocampal region. This cured Henry’s debilitating illness but had a tragic side-effect. Henry could no longer create new memories; every time he met someone or experienced something, it was as if for the first time. For all purposes, Henry was living permanently in the present.

However, Henry’s botched surgery revolutionized brain research—until then, it was believed that memory functions depended on the entire brain. No one knew the centrality of the hippocampal region as the engine of memory formation and for renewing old memories. For over half a century, Henry willingly subjected himself to numerous researches and was known worldwide as H.M. to protect his identity. His real name was revealed only after his death in 2008.

The science of memory is a complex and evolving discipline. We chart here, briefly, how we remember and forget with age, and the concept of “false memory” and how it is leading to a legal course correction.

Why do we forget as we age?

As we get older, we start forgetting things such as where we kept the glasses or the car keys or names of people. Research suggests that the human brain shrinks as we age because of cell loss. There is also cell loss in a region of the brain leading to reduction in the production of a neurotransmitter responsible for memory. This further leads to loss in the ability to make strong connections between brain cells that leads to formation of memories.

In fact, cognitive functions that rely on the prefrontal cortex and the hippocampus, which include memory formation and retrieval, are affected majorly by age-related deterioration. While there is normal age-related memory loss, one of the major reasons why the study of age-related memory loss has become an important area is dementia. According to the World Health Organization, 47.5 million people have dementia worldwide and there are 7.7 million new cases every year. Dementia—a syndrome in which there is decline in memory, thinking, behaviour and the ability to perform everyday activities—is caused by a variety of diseases and injuries that affect the brain, such as Alzheimer’s disease or stroke.

According to Scientific American, in Alzheimer’s disease, an abnormal protein called amyloid beta begins to appear on the neurons, forming plaques and compromising brain activity. There are many other reasons cited for Alzheimer’s, including genes, previous brain trauma, heart disease and gender. But not enough is known about the disease and the progressive decline of the brain functions because of it, and to find cures for it.

False memory
In a remarkable experiment in 2013, neuroscientists at the Center for Neural Circuit Genetics at the Massachusetts Institute of Technology (MIT) implanted false memories in the brains of mice. Their research, published in the journal Science in the same year, showed how neurons in the mice’s brains can be manipulated to create fear memories and false associations by using a technique called optogenetics that allows for minute control over individual brain cells.

In humans, too, imagination can lead to creation of powerful false memories. “Just like our mouse,” Susumu Tonegawa, part of the research team at MIT, told Science, “there could be a false association of what you have in your mind rather than what is happening to you.”

The implications are far-reaching; for instance, false memories of witnesses who testify in criminal cases can led to false convictions.

And positively, implanting false memory through psychiatric therapy can be used to treat post-traumatic stress disorders or even to treat addictions like alcoholism.

No one knows this as up close as Elizabeth Loftus, a psychologist and memory researcher from the University of California. In hundreds of criminal cases, she has informed juries that “memories are pliable and that eyewitness accounts are far from perfect recordings of actual events”, notes a August 2013 profile of Loftus in Nature magazine.

In a 1996 study called ‘Lost in the mall’, Loftus found that participants in a study can be made to believe, after being corroborated by relatives, that they were dramatically lost in a mall as a child; a quarter of the participants claimed to remember the false event concocted by Loftus.



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