Those with episodic amnesia are not ‘stuck in time,’ says philosopher Carl Craver

In 1981, a motorcycle accident left Toronto native Kent Cochrane with severe brain damage and dramatically impaired episodic memory. Following the accident, Cochrane could no longer remember events from his past. Nor could he predict specific events that might happen in the future.

When neuroscientist Endel Tulving, PhD, asked him to describe what he would do tomorrow, Cochrane could not answer and described his state of mind as “blank.”

Psychologists and neuroscientists came to know Cochrane, who passed away earlier this year, simply as “KC.” Many scientists have described KC as “stuck in time,” or trapped in a permanent present.

It has generally been assumed that people with episodic amnesia experience time much differently than those with more typical memory function. 

However, a recent paper in Neuropsychologia co-authored by Carl F. Craver, PhD, professor of philosophy and of philosophy-neuroscience-psychology, both in Arts & Sciences at Washington University in St. Louis, disputes this type of claim.

“It’s our whole way of thinking about these people that we wanted to bring under pressure,” Craver said. “There are sets of claims that sound empirical, like ‘These people are stuck in time.’ But if you ask, ‘Have you actually tested what they know about time?’ the answer is no.”

Time and consciousness

A series of experiments convinced Craver and his co-authors that although KC could not remember specific past experiences, he did in fact have an understanding of time and an appreciation of its significance to his life.

Interviews with KC by Craver and his colleagues revealed that KC retained much of what psychologists refer to as “temporal consciousness.” KC could order significant events from his life on a timeline, and he seemed to have complete mastery of central temporal concepts.

For example, KC understood that events in the past have already happened, that they influence the future, and that once they happen, they cannot be changed. 

He also knew that events in the future don’t remain in the future, but eventually become present. Even more interestingly, KC’s understanding of time influenced his decision-making.

If KC truly had no understanding of time, Craver argues, then he and others with his type of amnesia would act as if only the present mattered. Without understanding that present actions have future consequences or rewards, KC would have based his actions only upon immediate outcomes. However, this was not the case.

On a personality test, KC scored as low as possible on measures of hedonism, or the tendency to be a self-indulgent pleasure-seeker.

In systematic tests of his decision-making, carried out with WUSTL’s Len Green, PhD, professor of psychology, and Joel Myerson, PhD, research professor of psychology, and researchers at York University in Toronto, KC also showed that he was willing to trade a smaller, sooner reward for a larger, later reward.

In other words, KC’s inability to remember past events did not affect his ability to appreciate the value of future rewards. 

‘Questions are now wide open’

KC’s case reveals how much is left to discover about memory and how it relates to human understanding of time.

“If you think about memory long enough it starts to sound magical,” Craver said. “How is it that we can replay these events from our lives? And what’s going on in our brains that allows us to re-experience these events from our past?”

Craver hopes that this article — the last to be published about KC during his lifetime — brings these types of questions to the forefront. 

“These findings open up a whole new set of questions about people with amnesia,” Craver said. “Things that we previously thought were closed questions are now wide open.”

(Image credit)

I first met Henry Molaison more than half a century ago, during the spring of my third year in graduate school. I have tried to resurrect the details of my interactions with him that week, but human memory does not allow such excursions. The explicit minutiae of unique episodes fade as time passes, making it impossible for us to vividly re-experience the details of events in the distant past. What I do know is that I was very excited to have the opportunity to study such a rare case as Henry, and I had spent months preparing. Looking back at the results of all the tests he did that week, it was clear even then that the consequences of the operation carried out on him in 1957 – an experimental procedure to cure his epilepsy – had been catastrophic. Henry was left in a permanent state of amnesia, unable to retain any new information.

At the time of Henry’s operation, little was known about how memory processes worked. The extensive damage to the inner part of the temporal lobes on both sides of Henry’s brain made him a vital case study for memory researchers then and now. As the years passed, his fame grew and eventually spread to countries outside North America – and all that time Henry was stuck in the same moment. From time to time, I would tell him how important and well known he was, and he would smile sheepishly, as the praise was already slipping out of his consciousness. In his lifetime he was known as HM; only after his death, in 2008, was his identity revealed to the world.

Memory appears susceptible to eradication of fear responses

Fear responses can only be erased when people learn something new while retrieving the fear memory. This is the conclusion of a study conducted by scientists from the University of Amsterdam (UvA) and published in the leading journal Science.

Researchers Dieuwke Sevenster MSc, Dr Tom Beckers and Prof. Merel Kindt have developed a method to determine whether an acquired fear response is susceptible to modification. By doing so, they have revealed the circumstances under which an acquired fear response can be eradicated. In order to measure whether a person actually learnt something new, the researchers used a measure for Prediction Error – in other words, the discrepancy between a person’s anticipation of what is going to happen and what actually happens.

No fear response

Cognitive Behavioural Therapy is currently the most common and effective type of treatment for people suffering from anxiety disorders. However, the effects are often short-lived and the fear returns in many patients. One major finding of Van Kindt’s research lab is that when participants were given propranolol, a beta blocker, while retrieving a specific fear memory, the acquired fear response was shown to be totally erased a day or month later. The researchers repeatedly found that the fear did not come back, despite the use of techniques specifically aimed to make it return. This indicates that the fear memory was either fully eradicated, or could no longer be accessed. One crucial finding was that while participants could still remember the association with the fear, that particular memory no longer triggered the former fear response.

Fear conditioning

For their study the researchers used a fear conditioning procedure in which a specific picture was followed by a nasty painful stimulus. While the participants viewed the pictures, the researchers measured the anticipation of the painful stimulus as well as the more autonomous fear response on the basis of the startle reflex.

The current findings will contribute to the further development of more effective and efficient therapies for patients suffering from excessive anxiety disorders, such as trauma victims. There was no independent measure to indicate whether the memory is susceptible to modification up until now. The researchers have shown that the fear response can be eradicated completely, provided that the person concerned actually learns something new while retrieving the fear memory.

(Image: iStock)

Episodic Memory and Appetite Regulation in Humans

Psychological and neurobiological evidence implicates hippocampal-dependent memory processes in the control of hunger and food intake. In humans, these have been revealed in the hyperphagia that is associated with amnesia. However, it remains unclear whether ‘memory for recent eating’ plays a significant role in neurologically intact humans. In this study we isolated the extent to which memory for a recently consumed meal influences hunger and fullness over a three-hour period. Before lunch, half of our volunteers were shown 300 ml of soup and half were shown 500 ml. Orthogonal to this, half consumed 300 ml and half consumed 500 ml. This process yielded four separate groups (25 volunteers in each). Independent manipulation of the ‘actual’ and ‘perceived’ soup portion was achieved using a computer-controlled peristaltic pump. This was designed to either refill or draw soup from a soup bowl in a covert manner. Immediately after lunch, self-reported hunger was influenced by the actual and not the perceived amount of soup consumed. However, two and three hours after meal termination this pattern was reversed - hunger was predicted by the perceived amount and not the actual amount. Participants who thought they had consumed the larger 500-ml portion reported significantly less hunger. This was also associated with an increase in the ‘expected satiation’ of the soup 24-hours later. For the first time, this manipulation exposes the independent and important contribution of memory processes to satiety. Opportunities exist to capitalise on this finding to reduce energy intake in humans.