Representation of reward value involves a distributed network including cortical and subcortical structures. Because neurodegenerative illnesses target specific anatomic networks that partially overlap with the reward circuit, they would be predicted to have distinct impairments in reward processing. This review presents the existing evidence of reward processing changes in neurodegenerative diseases including mild cognitive impairment (MCI), Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Huntington's disease, as well as in healthy aging. Carefully distinguishing the different aspects of reward processing (primary rewards, secondary rewards, reward-based learning, and reward-based decision-making) and using tasks that differentiate the stages of processing reward will lead to improved understanding of this fundamental process and clarify a contributing cause of behavioral change in these illnesses.

Representation of reward value involves a distributed network including cortical and subcortical structures. Because neurodegenerative illnesses target specific anatomic networks that partially overlap with the reward circuit, they would be predicted to have distinct impairments in reward processing. This review presents the existing evidence of reward processing changes in neurodegenerative diseases including mild cognitive impairment (MCI), Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Huntington's disease, as well as in healthy aging. Carefully distinguishing the different aspects of reward processing (primary rewards, secondary rewards, reward-based learning, and reward-based decision-making) and using tasks that differentiate the stages of processing reward will lead to improved understanding of this fundamental process and clarify a contributing cause of behavioral change in these illnesses.

Background

Behavioral variant frontotemporal dementia (bvFTD) is characterized by marked deficits in empathy and social behavior; however, the effect of these symptoms on partner relationships has not been quantitatively measured.

Objective

We aimed to determine the effect of empathy loss and behavioral symptoms on partner and familial relationship status in bvFTD. We ascertained whether patients were currently in marriage/partner relationships or were separated/divorced, the timing and duration of these relationships, and whether the patients had relationship infidelity. We investigated the relationship status of 483 patients (156 with bvFTD, 38 with nonfluent variant primary progressive aphasia, 72 with semantic variant primary progressive aphasia, 49 with corticobasal syndrome, 45 with progressive supranuclear palsy syndrome, and 123 with Alzheimer disease) over the course of follow-up, and correlated relationship status with patients' first visit Interpersonal Reactivity Index and Neuropsychiatric Inventory.

Results

Relationship dissolution and infidelity were significantly more frequent among patients with bvFTD than in the other groups. Across all patients, empathy loss was associated with relationship dissolution. In the bvFTD group, patients who experienced relationship dissolution or infidelity had significantly lower empathy than those who did not.

Conclusions

Changes in relationship status differed across dementia groups and were associated with empathy decline.

Background

Behavioral variant frontotemporal dementia (bvFTD) is characterized by marked deficits in empathy and social behavior; however, the effect of these symptoms on partner relationships has not been quantitatively measured.

Objective

We aimed to determine the effect of empathy loss and behavioral symptoms on partner and familial relationship status in bvFTD. We ascertained whether patients were currently in marriage/partner relationships or were separated/divorced, the timing and duration of these relationships, and whether the patients had relationship infidelity. We investigated the relationship status of 483 patients (156 with bvFTD, 38 with nonfluent variant primary progressive aphasia, 72 with semantic variant primary progressive aphasia, 49 with corticobasal syndrome, 45 with progressive supranuclear palsy syndrome, and 123 with Alzheimer disease) over the course of follow-up, and correlated relationship status with patients' first visit Interpersonal Reactivity Index and Neuropsychiatric Inventory.

Results

Relationship dissolution and infidelity were significantly more frequent among patients with bvFTD than in the other groups. Across all patients, empathy loss was associated with relationship dissolution. In the bvFTD group, patients who experienced relationship dissolution or infidelity had significantly lower empathy than those who did not.

Conclusions

Changes in relationship status differed across dementia groups and were associated with empathy decline.

Behavioural variant frontotemporal dementia is characterized by abnormal responses to primary reward stimuli such as food, sex and intoxicants, suggesting abnormal functioning of brain circuitry mediating reward processing. The goal of this analysis was to determine whether abnormalities in reward-seeking behaviour in behavioural variant frontotemporal dementia are correlated with atrophy in regions known to mediate reward processing. Review of case histories in 103 patients with behavioural variant frontotemporal dementia identified overeating or increased sweet food preference in 80 (78%), new or increased alcohol or drug use in 27 (26%), and hypersexuality in 17 (17%). For each patient, a primary reward-seeking score of 0-3 was created with 1 point given for each target behaviour (increased seeking of food, drugs, or sex). Voxel-based morphometry performed in 91 patients with available imaging revealed that right ventral putamen and pallidum atrophy correlated with higher reward-seeking scores. Each of the reward-related behaviours involved partially overlapping right hemisphere reward circuit regions including putamen, globus pallidus, insula and thalamus. These findings indicate that in some patients with behavioural variant frontotemporal dementia, low volume of subcortical reward-related structures is associated with increased pursuit of primary rewards, which may be a product of increased thalamocortical feedback.

Behavioural variant frontotemporal dementia is characterized by abnormal responses to primary reward stimuli such as food, sex and intoxicants, suggesting abnormal functioning of brain circuitry mediating reward processing. The goal of this analysis was to determine whether abnormalities in reward-seeking behaviour in behavioural variant frontotemporal dementia are correlated with atrophy in regions known to mediate reward processing. Review of case histories in 103 patients with behavioural variant frontotemporal dementia identified overeating or increased sweet food preference in 80 (78%), new or increased alcohol or drug use in 27 (26%), and hypersexuality in 17 (17%). For each patient, a primary reward-seeking score of 0-3 was created with 1 point given for each target behaviour (increased seeking of food, drugs, or sex). Voxel-based morphometry performed in 91 patients with available imaging revealed that right ventral putamen and pallidum atrophy correlated with higher reward-seeking scores. Each of the reward-related behaviours involved partially overlapping right hemisphere reward circuit regions including putamen, globus pallidus, insula and thalamus. These findings indicate that in some patients with behavioural variant frontotemporal dementia, low volume of subcortical reward-related structures is associated with increased pursuit of primary rewards, which may be a product of increased thalamocortical feedback.

The human face plays a central role in emotions and social communication. The emotional and somatic motor networks generate facial behaviors, but whether facial behaviors have representations in the structural anatomy of the human brain is unknown. We coded 16 facial behaviors in 55 healthy older adults who viewed five videos that elicited emotions and examined whether individual differences in facial behavior were related to regional variation in gray matter volume. Voxel-based morphometry analyses revealed that greater emotional facial behavior during the disgust trial (i.e. greater brow furrowing and eye tightening as well as nose wrinkling and upper lip raising) and the amusement trial (i.e. greater smiling and eye tightening) was associated with larger gray matter volume in midcingulate cortex, supplementary motor area, and precentral gyrus, areas spanning both the emotional and somatic motor networks. When measured across trials, however, these facial behaviors (and others) only related to gray matter volume in the precentral gyrus, a somatic motor network hub. These findings suggest that the emotional and somatic motor networks store structural representations of facial behavior and that the midcingulate cortex is critical for generating the predictable movements in the face that arise during emotions.