Memory and the Brain

In the following days, Nader recalls, he passed through subway stations where walls were covered with notes and photographs left by people searching desperately for missing loved ones. Like millions of people, Nader has vivid and emotional memories of the September 11, , attacks and their aftermath.

But as an expert on memory, and, in particular, on the malleability of memory, he knows better than to fully trust his recollections. Most people have so-called flashbulb memories of where they were and what they were doing when something momentous happened: Kennedy, say, or the explosion of the space shuttle Challenger. Unfortunately, staggeringly terrible news seems to come out of the blue more often than staggeringly good news.

But as clear and detailed as these memories feel, psychologists find they are surprisingly inaccurate. Nader, now a neuroscientist at McGill University in Montreal, says his memory of the World Trade Center attack has played a few tricks on him. He recalled seeing television footage on September 11 of the first plane hitting the north tower of the World Trade Center. But he was surprised to learn that such footage aired for the first time the following day.

Nader believes he may have an explanation for such quirks of memory. His ideas are unconventional within neuroscience, and they have caused researchers to reconsider some of their most basic assumptions about how memory works.

What happens in your brain when you make a memory?

In short, Nader believes that the very act of remembering can change our memories. Much of his research is on rats, but he says the same basic principles apply to human memory as well. In fact, he says, it may be impossible for humans or any other animal to bring a memory to mind without altering it in some way.

Memories surrounding a major event like September 11 might be especially susceptible, he says, because we tend to replay them over and over in our minds and in conversation with others—with each repetition having the potential to alter them. For those of us who cherish our memories and like to think they are an accurate record of our history, the idea that memory is fundamentally malleable is more than a little disturbing. Not all researchers believe Nader has proved that the process of remembering itself can alter memories.

THE BRAIN FROM TOP TO BOTTOM

But if he is right, it may not be an entirely bad thing. It might even be possible to put the phenomenon to good use to reduce the suffering of people with post-traumatic stress disorder, who are plagued by recurring memories of events they wish they could put behind them.

Nader was born in Cairo, Egypt. His Coptic Christian family faced persecution at the hands of Arab nationalists and fled to Canada in , when he was 4 years old. He attended college and graduate school at the University of Toronto, and in joined the New York University lab of Joseph LeDoux, a distinguished neuroscientist who studies how emotions influence memory.

Neuroanatomy of memory

Even the most cherished ideas in a given field are open to question. Scientists have long known that recording a memory requires adjusting the connections between neurons. Each memory tweaks some tiny subset of the neurons in the brain the human brain has billion neurons in all , changing the way they communicate. Neurons send messages to one another across narrow gaps called synapses. A synapse is like a bustling port, complete with machinery for sending and receiving cargo—neurotransmitters, specialized chemicals that convey signals between neurons.

All of the shipping machinery is built from proteins, the basic building blocks of cells. One of the scientists who has done the most to illuminate the way memory works on the microscopic scale is Eric Kandel, a neuroscientist at Columbia University in New York City. In five decades of research, Kandel has shown how short-term memories—those lasting a few minutes—involve relatively quick and simple chemical changes to the synapse that make it work more efficiently.

But after the memory is consolidated, it changes very little. Nader would challenge this idea. Nader got to wondering about what happens when a memory is recalled. Researchers had found that a memory could be weakened if they gave an animal an electric shock or a drug that interferes with a particular neurotransmitter just after they prompted the animal to recall the memory. This suggested that memories were vulnerable to disruption even after they had been consolidated. To think of it another way, the work suggested that filing an old memory away for long-term storage after it had been recalled was surprisingly similar to creating it the first time.

Both building a new memory and tucking away an old one presumably involved building proteins at the synapse. Nader decided to revisit the concept with an experiment. That was easy—rodents learn such pairings after being exposed to them just once. Afterward, the rat freezes in place when it hears the tone. But if memories have to be at least partially rebuilt every time they are recalled—down to the synthesizing of fresh neuronal proteins—rats given the drug might later respond as if they had never learned to fear the tone and would ignore it.

If so, the study would contradict the standard conception of memory. It was, he admits, a long shot. Nader, who looks slightly devilish in his earring and pointed sideburns, still gets giddy talking about the experiment. But the data struck a more harmonious chord with some psychologists. After all, their experiments had long suggested that memory can easily be distorted without people realizing it. In a classic study led by Elizabeth Loftus, a psychologist then at the University of Washington, researchers showed college students a series of color photographs depicting an accident in which a red Datsun car knocks down a pedestrian in a crosswalk.

The students answered various questions, some of which were intentionally misleading. Later the researchers asked all the students what they had seen—a stop sign or yield sign? To Nader and his colleagues, the experiment supports the idea that a memory is re-formed in the process of calling it up. Hardt and Nader say something similar might happen with flashbulb memories. People tend to have accurate memories for the basic facts of a momentous event—for example, that a total of four planes were hijacked in the September 11 attacks—but often misremember personal details such as where they were and what they were doing at the time.

• Explicit memory.
• How Our Brains Make Memories | Science | Smithsonian.
• Apartheids Child, Freedoms Son.
• CAMPAÑAS MILITARES ARGENTINAS - III (1854-1865) (Spanish Edition).
• Letters to My Children: A Father Passes on His Values.

Hardt says this could be because these are two different types of memories that get reactivated in different situations. Television and other media coverage reinforce the central facts. But recalling the experience to other people may allow distortions to creep in. Some experts think he is getting ahead of himself, especially when he makes connections between human memory and these findings in rats and other animals. Daniel Schacter, a psychologist at Harvard University who studies memory, agrees with Nader that distortions can occur when people reactivate memories.

The question is whether reconsolidation—which he thinks Nader has demonstrated compellingly in rat experiments—is the reason for the distortions. For explicit memories — which are about events that happened to you episodic , as well as general facts and information semantic — there are three important areas of the brain: Implicit memories , such as motor memories, rely on the basal ganglia and cerebellum.

• Psychic Volume 2?
• I Feed My Pain.
• Short-term memory – like writing your name with a sparkler.

Short-term working memory relies most heavily on the prefrontal cortex. There are three areas of the brain involved in explicit memory: Episodic memories are autobiographical memories from specific events in our lives, like the coffee we had with a friend last week. How do we know this?

His epilepsy was cured, and Molaison lived a further 55 healthy years. However, after the surgery he was only able to form episodic memories that lasted a matter of minutes; he was completely unable to permanently store new information.

Accessibility Navigation

He was, however, still able to improve his performance on various motor tasks, even though he had no memory of ever encountering or practising them. The study of Henry Molaison was revolutionary because it showed that multiple types of memory existed. We now know that rather than relying on the hippocampus, implicit motor learning occurs in other brain areas — the basal ganglia and cerebellum.

The neocortex is the largest part of the cerebral cortex, the sheet of neural tissue that forms the outside surface of the brain, distinctive in higher mammals for its wrinkly appearance. In humans, the neocortex is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning and language. Over time, information from certain memories that are temporarily stored in the hippocampus can be transferred to the neocortex as general knowledge — things like knowing that coffee provides a pick-me-up.

Implicit memory

Researchers think this transfer from hippocampus to neocortex happens as we sleep. This is particularly important because strong emotional memories e. The amygdala doesn't just modify the strength and emotional content of memories; it also plays a key role in forming new memories specifically related to fear. Fearful memories are able to be formed after only a few repetitions.