Chapter 13 Chapter Summary

Chapter Overview:

This chapter explores how our health can influence our memory and how memory can influence our health.

The first section focuses on the differences between normal aging and dementia. While memory abilities tend to decrease as we age, it is considered normal loss unless it interferes with day-to-day life. If the memory deficits are significant enough to interfere with daily living, then it is probably the result of a neurological disorder that affects not only memory but the ability to think and reason as well. The most frequently used assessment tool is the mini-mental state examination (MMSE) which can distinguish between various types of dementia.

The most common cause of dementia is Alzheimer’s disease accounting for between 60 and 70 percent of neurocognitive disorders worldwide. It is characterized by a buildup of amyloid plaques and tangles in the brain and a substantial reduction in the size of the brain. It typically starts with problems in short-term memory but as it progresses and the cortex and hippocampus shrink, problems with old memories, forming new memories, and staying focused on a task become more problematic. Cholinesterase inhibitors can be used to treat mild to moderate Alzheimer’s by improving neural communication. While the cause of Alzheimer’s is still debated, there is some evidence that there is a genetic link that prevents the brain from controlling the amounts of amyloids in the brain. Other explanations include concussions and heart disease.

Vascular dementia causes a decline in cognitive skills from a reduction in blood flow to the brain due to stokes. Vascular dementia can occur with Alzheimer’s or as a stand-alone cause of dementia. The symptoms of vascular dementia are quite varied as they depend on where the strokes occurred. It is typically identified through neuroimaging. Risk factors include age, hypertension, smoking, diabetes, cardiovascular disease, and cerebrovascular disease. Dementia with Lewy bodies (DLB) causes a decline in cognitive abilities as well as fluctuations in alertness, difficulty with movement, mood changes, and visual hallucinations. Symptoms tend to progress quite rapidly and there is no known cure. Frontotemporal dementia (FTD) is caused by the deterioration of spindle neurons in the frontal and temporal lobes. Unlike other forms of dementia, the deficits of FTD are not associated with memory; instead, initial symptoms are related to blunted emotions, apathy, and difficulties with language. As a result, tests for FTD focus on interpretations of social interactions instead of memory-based assessments.

While most types of dementia are not curable, there are a few treatable disorders, including hypothyroidism and vitamin B₁₂ deficiency, that can result in symptoms of dementia. By treating the disorder, the dementia is usually reduced or eliminated.

The second section in this chapter focuses on health conditions that can cause memory loss. Epilepsy can result in a lack of attention (therefore can create difficulties in learning) and the seizures themselves can cause brain damage that result in retrograde amnesia. Injuries to the brain as a result of accident or disease can also affect memory. Some diseases affect memory by causing inflammation that disrupts blood flow (e.g., encephalitis) while others simply destroy brain tissue. Blows to the head, including concussions, can not only disrupt the consolidation process for the time just prior to the trauma but, with multiple injuries, can cause long-term problems with memory. Korsakoff’s syndrome is typically the result of severe alcohol abuse and is caused by a vitamin B₁ (thiamine) deficiency. Individuals with Korsakoff’s syndrome have both retrograde and anterograde amnesia as well as some problems with short term memory. While most memory issues stem from physiological causes, dissociative amnesia is memory loss caused from psychological factors. Dissociative amnesia is diagnosed when there is a sudden loss of autobiographical memories and sense of self without a physical cause. Dissociative amnesia can occur for hours, days, to even years and are typically the result of stressful life conditions and/or past abuse. Most cases are resolved without treatment. Dissociative fugue is the loss of autobiographical memory combined with wandering from home. Brain imagery strongly suggest brain abnormalities exist in these individuals and may be the underlying cause of the amnesia. Because memories are consolidated to a more permanent store during slow-wave sleep (SWS), it is not surprising that health conditions associated with problems with memory are also associated with reduced SWS. In fact, memory loss linked with normal aging might also be the result of decreased SWS. 

The third section of this chapter discusses substances that affect memory. For example, patients are given twilight anaesthesia during many outpatient procedures to reduce anxiety and to induce temporary anterograde amnesia. Alcohol can also negatively impact memory, usually by impairing the acquisition of new memories; however, research has also revealed that small doses of alcohol can enhance recently learned memories probably due to the stimulating effects of alcohol.

The fourth section discusses how memories (or lack of them) impact health. Post-traumatic stress disorder (PTSD) is sometimes associated with problems with attention and memory. While some researchers have suggested that differences in memory problems amongst those suffering from PTSD might be related to alcohol abuse or depression, newer research has not found this connection. Instead, there is decreased performance on verbal and working memory tasks in people with PTSD with larger deficits in performance correlated with an increased severity of symptoms of PTSD. It is possible that problems in the prefrontal cortex can account for these deficits. The need to recheck that a behaviour was completed is a common symptom of obsessive-compulsive disorder (OCD). While some theorized that people with OCD might just be forgetting that they had already checked (i.e., poor memory), newer research has demonstrated that the repeated checking results in reduced vividness and detail of their memories of checking and therefore decreased confidence in the memories itself.

Most legal consultants would advise people to have an advance directive (AD) – a legal documents that states what medical decisions they would want in the eventuality they were unable to make the decisions themselves. Despite the importance of these decisions, many people often change their mind about what they want and, even more surprising, many people do not accurately remember all of the decisions they made. Typically, people tend to believe the options they previously selected, are consistent with what they would decide in the present. These memory biases also exist for remembering medical advice. That is, we tend to forget medical advice that is not consistent with our current beliefs and, in that way, maintain a view of ourselves as healthy.

Research has shown that people have better memory for information related to our survival than information that is not related. This survival effect seems to be evoked in an environment of evolutionary adaptiveness (EEA) but only when thinking about our own survival – a type of self-reference effect (SRE). Research has consistently shown that aerobic exercise can increase the size of the hippocampus and is related to improvements in visuospatial memory. For most Canadians, getting more exercise is a fairly simple way to improve some aspects of memory. Our malleable memories can be used towards promoting better health by implanting false memories of negative experiences with unhealthy foods and positive memories of healthy food. These false memories may push people towards healthier food choices.

Learning Objectives:

Having read this chapter, you will be able to do the following:

1. Differentiate between normal loss of memory that occurs because of aging and dementia.
2. Compare and contrast Alzheimer’s disease, vascular dementia, dementia with Lewy bodies, and frontotemporal dementia.
3. Discuss reversible causes of dementia.
4. Identify health conditions that can lead to problems with memory.
5. Identify substances that can lead to problems with memory.
6. Explain memory problems associated with post-traumatic stress disorder (PTSD).
7. Explain how a lack of metamemory skills may contribute to obsessive-compulsive disorder (OCD).
8. Identify health behaviours that can improve memory.
9. Identify how memory can be used to improve health.
10. Discuss the implications of research examining memory for advance directives.
11. Explain how memory biases affect individual memory for health-related advice.
12. Discuss evolutionary influences on memory.