Memory: A Curious Journey

When we discuss memory, particularly in the context of learning, we usually refer to psychological models, such as the Working Memory Model of Baddeley and Hitch or the earlier Multi-store Model of Atkinson and Shiffrin. At a push we may refer to Cowan’s Embedded Process Theory or discuss working memory from within models of instructional design, such as Cognitive Load Theory or Load Reduction Instruction. But it’s not only about models and memory has been investigated with the help of certain individuals who have been able to provide a unique insight and into how we process, recall and forget things we have learned.

While, traditionally, these models of memory have helped us to understand how memory works by devising hypotheses and then conducting experiments to test them, memory research became even more interesting with advent of sophisticated scanning techniques, most notably functional magnetic resonance imaging or fMRI. A combination of experimentation, scanning and study of individuals with specific memory deficits provides memory researchers with a wealth of information to help solve the many puzzles that human memory offers up, while at the same time casting doubt on the brain-as-computer hypothesis. One person who has perhaps done more to inform this understanding wasn’t a psychologist, neuroscientist or researcher of any kind. Known only as H.M. until his death in 2008, Henry Molaison did more for the study of memory than perhaps all other research combined.

The Man with no Memory

Born in 1926 in Manchester, Connecticut, Henry had a long history of epilepsy, caused possibly by a bicycle accident when he was seven years old. He suffered from major partial seizures when he was young and then major tonic-clonic seizures from about the age of sixteen. Henry worked on a factory production line until the age or twenty-seven, at which point the seizures became so frequent that he could no longer work at all. He was referred to William Beecher Scoville, a neurosurgeon based out of Hartfield hospital, Connecticut who operated on Henry in 1953. In an attempt to cure Henry’s epilepsy, Scoville removed a large section of his brain, namely, around two-thirds of his medial temporal lobes on both hemispheres. The surgery, known as a bilateral medial temporal lobectomy, resulted in the removal of parts of Henry’s hippocampus and most of his amygdala, as well as other areas. This extensive procedure did manage to partially control the seizures but also resulted in severe anterograde amnesia. This meant that while his working memory and procedural memory remained intact, he was unable to commit any new events to his explicit memory, in other words, Henry couldn’t make any new memories. In addition, Henry suffered from moderate retrograde amnesia, meaning that he was unable to recall events in the one or two year period prior to his surgery or up to eleven years before that.

Henry suffered from severely impaired memory as the result of surgery, though others might experience similar problems due to other factors such as viral infections. When I was four years old my parents took my brother and I on holiday to Athens, Greece. My father had received a classical education and had grown up with fascination of ancient civilisations, so while my friends spent their time on beech holidays, Dad continued in his attempts to educate us in keeping with his own schooling. While we were holidaying, Mum contracted encephalitis (a virus that causes inflammation of the brain), initially resulting in her misplacing most of her long-term memory and suffer damage to her short-term memory. She spent a long time in hospital in Oxford and gradually most of her long-term memory returned and her short-term memory improved.

The memories of her time in Greece never returned and she has suffered from short-term memory problems and epilepsy ever since. For as long as I can recall, she has kept brief notes in her diary to remind her of things she needed to do or reminders of things she fears she might forget. Now in her seventies, age has compounded her memory difficulties and she keeps a list of what she has done and who she has seen each day so that she can retain some sense of continuity in her life.

Henry Molaison’s case was first reported in a 1957 by Scoville and the British-Canadian neuropsychologist Brenda Milner and he continued to be studied until his death in 2008. Indeed, Henry was a vital part of the search for link between brain function and memory and had an important role to play in the development of cognitive neuropsychology as a discipline. What this wealth of information has highlighted is the complexity of the memory formation and how memory appears to be spread throughout the cortex. Most notably, however, studying people like Henry has provided researchers with important details about the role of certain brain structures, in particular the hippocampus. The hippocampus (so named because of its resemblance to a seahorse) is a major component of the human brain (as well as other vertebrates), involved in the consolidation of short-term and long-term memory and spatial memory. It may also play a role in our ability to imagine, including predicting and planning our future.

Memory, imagination and creativity

We can assume that memory and imagination are somehow linked, that they are supported by the same neural network. This network undoubtedly includes the hippocampus, but is also likely to include other brain areas as well, known as the core network or default mode network. It seems clear that the hippocampus and the medial temporal lobes (MTL) play important roles in the ability to recollect past experiences, but, as O’Keefe and Dostrovsky point out, the hippocampus isn’t only concerned with memory.

There is a tendency to think of brain regions as only having one function when, in reality, they almost always have several. The hippocampus, for example, is also concerned with location-specific information and damage to this region has been found to severely disrupt spatial navigation ability. This may well explain the memory and navigation deficits seen in people with bilateral hippocampal damage.

This is all well and good, but what about the relationship between the hippocampus and imagination? In early studies, it did appear that people with severe amnesia did have problems imagining and planning their personal future, for example, the patient ‘KC’ who suffered from widespread damage to his brain that included the MTL. Klein and colleagues report that their patient (‘DB’), who had similar impairments to KC, was unable to project himself into the future.

When Henry was asked what he believed would happen tomorrow, he answered, ‘whatever is beneficial’. He appeared to have no information stored that would inform him of the possibilities available, no ‘database’ to consult when asked what he would do the next day, week, or in years to come.’ Often when asked to make a prediction about his personal future, Henry would pick out an event from a distant memory, but at other times he would not respond at all.

Cognitive nudges

Memory impairments can seem unfathomable at times. In the spring of 2019 I visited my mum in her flat on the other side of town. She initially seemed her usual self, perhaps a little low in spirit, but with a peculiar air of confusion. With a little prompting from me she admitted that she had woken that morning and walked into her living room, perplexed by the photographs of my younger brother’s wedding two years previously. ‘I’d forgotten Matthew got married,’ she admitted, ‘and I still have no memory of it.’ It transpired that she had also misplaced the memory of my other brother marrying only the year before and had only realised when she discovered that she had added the name ‘Smith’ to his wife’s name in her address book. We spent the afternoon chatting about both weddings and looking through photographs and as the hours and days passed, the memories returned. Mum’s memories weren’t lost, they simply became temporarily inaccessible and the gentle nudges – the photographs and the conversations, helped to reconnect her to the past.

Neuroscientist Catherine Loveday had been experimenting with a device developed by Microsoft called SenseCam, a small camera that takes a series of random still photographs throughout the day. When older people with memory impairments are kitted out with these devices, the pictures allow them to reconstruct in their mind events throughout the day that might have been misplaced. These cognitive nudges are all around us, both from our recent and long-term past – the schools we attended, buildings that remain from our childhood or repeats of television shows from our teenage years.

Many aspects of human memory remain unfathomable but as theoretical models, case studies and other techniques arise, we get a little closer to understanding how all the pieces fit together. It’s still a work in progress, but with the help of people like Henry, we’re slowly getting there.

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