Emotional and behavioral symptoms in neurodegenerative disease: a model for studying the neural bases of psychopathology

Abstract

Disruptions in emotional, cognitive, and social behavior are common in neurodegenerative disease and in many forms of psychopathology. Because neurodegenerative diseases have patterns of brain atrophy that are much clearer than those of psychiatric disorders, they may provide a window into the neural bases of common emotional and behavioral symptoms. We discuss five common symptoms that occur in both neurodegenerative disease and psychopathology (i.e., anxiety, dysphoric mood, apathy, disinhibition, and euphoric mood) and their associated neural circuitry. We focus on two neurodegenerative diseases (i.e., Alzheimer's disease and frontotemporal dementia) that are common and well characterized in terms of emotion, cognition, and social behavior and in patterns of associated atrophy. Neurodegenerative diseases provide a powerful model system for studying the neural correlates of psychopathological symptoms; this is supported by evidence indicating convergence with psychiatric syndromes (e.g., symptoms of disinhibition associated with dysfunction in orbitofrontal cortex in both frontotemporal dementia and bipolar disorder). We conclude that neurodegenerative diseases can play an important role in future approaches to the assessment, prevention, and treatment of mental illness.

Figure 1

Prevalence estimates for symptoms of psychopathology in Alzheimer’s disease (AD) reported by caregivers using the Neuropsychiatric Inventory (Cummings 1997). Data from Mega and colleagues (1996). Mini Mental State Examination scores for Mild AD: 21–30; Moderate AD: 11–20; Severe AD: 0–10

Figure 2

Prevalence estimates for symptoms of psychopathology in frontotemporalobar dementia (FTD) reported by caregivers using the Neuropsychiatric Inventory (Cummings 1997). Data on behavioral variant FTD (bvFTD) and semantic variant primary progressive aphasia (svPPA) from Liu and colleagues (2004).

Figure 3

Karaoke singing task elicits self-conscious emotion in healthy participants but not in patients with FTD. Note. The large pictures show the participants while watching themselves singing Karaoke style (the small picture insets show the video recordings of them singing “My Girl,” which were recorded earlier in the testing session). Still images were taken from videotaped recordings of the laboratory testing session. The participants provided consent for their videotape being used for scientific publication. (A) An embarrassment response in a healthy control participant. The participant exhibits an embarrassment response, as indexed by smiling, smile suppression, gaze aversion, and face touching. (B) A patient with behavioral variant FTD watching himself singing Karaoke style. The patient exhibited no embarrassment response during the task.