Frontal brain functioning and pain: Possible underlying mechanisms of increased pain responses in age- and dementia-related cognitive impairment

Abstract

Chapter 1 General introduction Chapter 2 Pain and executive functions: a systematic review Chapter 3 Does EEG activity during painful stimulation mirror more closely the noxious stimulus intensity or the subjective pain sensation? Chapter 4 Conditioned pain modulation (CPM) effects captured in facial expressions Chapter 5 Pain processing in older adults and its association with prefrontal characteristics Chapter 6 Pain processing in older adults with dementia-related cognitive impairment is associated with frontal neurodegeneration Chapter 7 General discussion Summary Samenvatting Dankwoord Curriculum vitae Chapter 1 General introduction 8 CHAPTER 1 General introductionThe proportion of older individuals in our society is increasing. 1 One of the many implications of this demographic change is that the number of individuals with pain also increases. Pain is quite prevalent in older compared to younger individuals, with more than half of the people over the age of 60 experiencing pain. 2,3 Pain is for example prevalent in older individuals with common chronic diseases such as cardiovascular, musculoskeletal and oncological diseases. 4 In order to treat pain well, it is important to study why older individuals become more vulnerable to pain.The present thesis studied the hypothesis that increased pain in older individuals might be due to decreased frontal brain functioning. We assessed frontal brain functioning by means of structural integrity of the frontal cortex and by neuropsychological performances that are linked to the function of the frontal cortex. The relation between pain and frontal functioning was not only studied in healthy older individuals but also in older individuals with dementia-related cognitive impairments, given that they might be even more vulnerable to pain due to more pronounced decreased frontal brain functioning.The rationale behind the frontal brain functioning hypothesis will be described in this general introduction. In the first part, the topic pain will be introduced, with a focus on the neurobiological pathways that mediate pain processing and the methods used to study pain processing in humans. In the second part, the current knowledge about the effect of age-and dementia-related cognitive impairment on pain processing will be discussed. At the end of this chapter, an overview of the studies described in the upcoming chapters will be given. Pain DefinitionThe newest definition of pain, updated in 2020, according to the International Association for the Study of Pain is that pain is "an aversive sensory and emotional experience typically caused by, or resembling that caused by, actual or potential tissue injury. " 5 This definition emphasizes that pain is an emotional and thus a subjective experience. Pain experience (especially acute pain) is often linked to nociceptive processes. Nociception refers to the physiological signal transduction and transmission in response to actual or potential tissue injury. 6 The two routes for nociceptive information, called the "ascending pain...