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Topic Name: Researchers show People with rare type of memory loss still sensitive to others

Category: Biomedical

Research persons: Dr. R. Shayna Rosenbaum

Location: York University, United States

Details

People with a devastating brain injury that has wiped out many of their personal memories may still be able to understand other people’s feelings and intentions, according to a joint study by the Rotman Research Institute at the Baycrest Centre for Aging and the Brain, and York University’s Department of Psychology, Faculty of Health.

The study, published in the Nov. 23, 2007 issue of Science, reports that severe loss of autobiographical episodic memory does not necessarily compromise the ability to figure out the mental states of other people, including their feelings and intentions.

For people with this distressing cognitive condition and for those caring for them, there is a “hope” message in the findings, says lead investigator Dr. Shayna Rosenbaum, a cognitive neuropsychologist at Baycrest’s Rotman Research Institute and assistant professor of psychology at York University.

Even though there might be some social consequences of losing your autobiographical memory, it doesn’t mean all is lost, Dr. Rosenbaum says. “The person can still be in tune with others’ feelings and intentions which can help sustain social relationships, especially with loved ones. It’s encouraging to know that this ability may be more resilient and preserved in us than was first thought.”

Understanding the feelings and intentions of others is the basis of our socialization and what makes us human. It’s known as “Theory of Mind” and associated with the prefrontal cortex. In scientific circles, an idea has floated around for a long time that in order to imagine and make sense of other people’s thoughts, we must rely on our own personal autobiographical recollections (episodic memory). But some scientists have been skeptical of this assumption and wondered if Theory of Mind abilities can exist without episodic memory.

Dr. Rosenbaum and senior scientists at the Rotman – including the world-renowned memory pioneer Dr. Endel Tulving, frontal lobes expert Dr. Donald Stuss, and Dr. Brian Levine whose expertise is autobiographical memory – had an extraordinary opportunity to test this long-held assumption by conducting the first systematic examination of this theory in two individuals with limited autonoetic awareness, a rare cognitive condition.

The individuals, known as K.C. and M.L., sustained severe head injuries several years earlier in motorcycle and cycling accidents that erased most of their autobiographical episodic memory. They could no longer remember personal episodes of their past and how they felt. Dr. Tulving had studied K.C. many years ago and noted that K.C. was also unable to imagine himself at a future point in time. He came up with the phrase “autonoetic awareness” to describe this human ability to mentally time travel.

In this latest study, K.C., M.L. and 14 healthy controls were put through a series of tests widely known to be sensitive to Theory of Mind and perspective taking (ie. the clear appreciation of empathy, deception, sarcasm and false beliefs in others). Some of the tests involved looking at the eye regions of faces to determine if the person was deceitful or playful, and viewing emotional scenarios and listening to narratives to determine the other’s mental state.

Investigators found that K.C. and M.L. performed as well as healthy subjects on all measures even though they had severely impaired autonoetic awareness.

“We found that if you’re trying to put yourself mentally in someone else’s shoes, you don’t need to put yourself in your own shoes first,” says Dr. Rosenbaum.

This preserved ability to infer other people’s feelings and intentions may be related to semantic memory (knowledge of general facts about the world and people) that was left intact after the injury, Dr. Rosenbaum suggests. She adds that more studies are needed to look at what parts of the brain are involved in this compensation.

“Our findings suggest that episodic memory is not necessary to have normal insight into other people’s minds,” reinforces Dr. Tulving, a cognitive psychologist who is internationally recognized for his landmark research to distinguish different types of human memory. “We still do not know whether episodic memory might be necessary for the development of such an insight in the first place! This is yet another open problem.”

Note for Episodic memory

Episodic memory refers to the memory of events, times, places, associated emotions, and other conception-based knowledge in relation to an experience. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory. The counterpart to declarative, or explicit memory, is procedural memory, or implicit memory.
The formation of new episodic memories requires the medial temporal lobe, a structure that includes the hippocampus. Without the medial temporal lobe, one is able to form new procedural memories (such as playing the piano) but cannot remember the events during which they happened.
The prefrontal cortex (and in particular the left hemisphere) is also involved in the formation of new episodic memories (also known as episodic encoding). Patients with damage to the prefrontal cortex can learn new information, but tend to do so in a disordered fashion. For example, they might show normal recognition of an object they had seen in the past, but fail to recollect when or where it had been viewed.

Note for Semantic memory

Semantic memory refers to the memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory. The counterpart to declarative, or explicit memory, is procedural memory, or implicit memory.
Semantic memory includes generalized knowledge that does not involve memory of a specific event. For instance, you can answer a question like "Are wrenches pets or tools?" without remembering any specific event in which you learned that wrenches are tools.
Comprehensive models of semantic memory illustrate the structure and representation of semantic categories. One approach argues that a series of associations between nodes in a memory network correspond to categories and the links between nodes represent meaningful relationships or associations among the categories. These relationships would then be explicitly “pre-stored” (E. E. Smith, 1978). For example, a subject must decide whether a sentence like All maples are trees is true. The subject should be able to make the correct decision by searching for the appropriate link(s) directly from semantic memory, retrieving the link, and answering the statement.

Note for Theory of mind

Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others. As originally defined, it enables one to understand that mental states can be the cause of—and thus be used to explain and predict—others’ behavior. Being able to attribute mental states to others and understanding them as causes of behavior means, in part, that one must be able to conceive of the mind as a “generator of representations” and to understand that others’ mental representations of the world do not necessarily reflect reality and can be different from one’s own. It also means one must be able to maintain, simultaneously, different representations of the world. It is a ‘theory’ of mind in that such representations are not "directly observable". Many other human abilities—from skillful social interaction to language use—are said to involve a theory of mind.

The study was funded by both Baycrest and York University, supported by grants from the Heart and Stroke Foundation of Ontario Centre for Stroke Recovery, and the Louis and Leah Posluns Centre for Stroke and Cognition at Baycrest.

About Researcher

Dr. R. Shayna Rosenbaum
Principal Investigator
Cognitive Neuroscience Lab, York University
Room 041
Atkinson Building
York University

Associate Scientist
Rotman Research Institute

Research Focus
The role of the hippocampus and related brain structures in recent and remote memory
Neural representation of spatial memory and cognition
The role of different frontal regions in emotional-cognitive processing