Humor as a reward mechanism: event-related potentials in the healthy and diseased brain

Establishing the Roles of the Dorsal and Ventral Striatum in Humor Comprehension and Appreciation with fMRI

Humor comprehension (i.e., getting a joke) and humor appreciation (i.e., enjoying a joke) are distinct, cognitively complex processes. Functional magnetic resonance imaging (fMRI) investigations have identified several key cortical regions but have overlooked subcortical structures that have theoretical importance in humor processing. The dorsal striatum (DS) contributes to working memory, ambiguity processing, and cognitive flexibility, cognitive functions that are required to accurately recognize humorous stimuli. The ventral striatum (VS) is critical in reward processing and enjoyment. We hypothesized that the DS and VS play important roles in humor comprehension and appreciation, respectively. We investigated the engagement of these regions in these distinct processes using fMRI. Twenty-six healthy young male and female human adults completed two humor-elicitation tasks during a 3 tesla fMRI scan consisting of a traditional behavior-based joke task and a naturalistic audiovisual sitcom paradigm (i.e., Seinfeld viewing task). Across both humor-elicitation methods, whole-brain analyses revealed cortical activation in the inferior frontal gyrus, the middle frontal gyrus, and the middle temporal gyrus for humor comprehension, and the temporal cortex for humor appreciation. Additionally, with region of interest analyses, we specifically examined whether DS and VS activation correlated with these processes. Across both tasks, we demonstrated that humor comprehension implicates both the DS and the VS, whereas humor appreciation only engages the VS. These results establish the role of the DS in humor comprehension, which has been previously overlooked, and emphasize the role of the VS in humor processing more generally.SIGNIFICANCE STATEMENT Humorous stimuli are processed by the brain in at least two distinct stages. First, humor comprehension involves understanding humorous intent through cognitive and problem-solving mechanisms. Second, humor appreciation involves enjoyment, mirth, and laughter in response to a joke. The roles of smaller subcortical brain regions in humor processing, such as the DS and VS, have been overlooked in previous investigations. However, these regions are involved in functions that support humor comprehension (e.g., working memory ambiguity resolution, and cognitive flexibility) and humor appreciation (e.g., reward processing, pleasure, and enjoyment). In this study, we used neuroimaging to demonstrate that the DS and VS play important roles in humor comprehension and appreciation, respectively, across two different humor-elicitation tasks.

Data-point-wise spatiotemporal mapping of human ventral visual areas: Use of spatial frequency/luminance-modulated chromatic faces

Visual information involving facial identity and expression is crucial for social communication. Although the influence of facial features such as spatial frequency (SF) and luminance on face processing in visual areas has been studied extensively using grayscale stimuli, the combined effects of other features in this process have not been characterized. To determine the combined effects of different SFs and color, we created chromatic stimuli with low, high or no SF components, which bring distinct SF and color information into the ventral stream simultaneously. To obtain neural activity data with high spatiotemporal resolution we recorded face-selective responses (M170) using magnetoencephalography. We used a permutation test procedure with threshold-free cluster enhancement to assess statistical significance while resolving problems related to multiple comparisons and arbitrariness found in traditional statistical methods. We found that time windows with statistically significant threshold levels were distributed differently among the stimulus conditions. Face stimuli containing any SF components evoked M170 in the fusiform gyrus (FG), whereas a significant emotional effect on M170 was only observed with the original images. Low SF faces elicited larger activation of the FG and the inferior occipital gyrus than the original images, suggesting an interaction between low and high SF information processing. Interestingly, chromatic face stimuli without SF first activated color-selective regions and then the FG, indicating that facial color was processed according to a hierarchy in the ventral stream. These findings suggest complex effects of SFs in the presence of color information, reflected in M170, and unveil the detailed spatiotemporal dynamics of face processing in the human brain.

Cognitive, neural and endocrine functioning during late pregnancy: An Event-Related Potentials study

This study investigated cognitive, neural and endocrine function during late pregnancy. One of the first to examine brain ERPs in pregnant women, the study is unique in its focus on response inhibition function. In the study, cognitive function was evaluated by a digit-symbol coding test, an arithmetic ability test, and a visual stop-signal task which places enhanced demands on impulse control and response inhibition, considered a hallmark of executive function. Brain activity was measured by scalp-recorded Event-Related Potentials (ERPs) during the stop-signal task. HPA axis reactivity was assessed by measuring salivary cortisol levels before and after experimental sessions. Test performance, ERPs and cortisol reactivity were compared across groups of 23 women in their third trimester of pregnancy and 22 non-pregnant controls. Pregnant women scored lower than the control group on the digit-symbol coding test. On the stop-signal task, both groups had similar error rates, but pregnant women had longer response times to Go trials. On the Stop condition of the task in which a response must be inhibited, pregnant women demonstrated significantly better performance. At the electrophysiological level, in response to Go stimuli pregnant women exhibited greater amplitude of P2 than controls. In response to Stop-signals, pregnant women had lesser amplitudes of P1 and N2 and greater amplitude of P3. Cortisol reactivity to the test session was significantly more pronounced in non-pregnant women with significant correlations found between cortisol reactivity and behavioral responses. The results suggest that response patterns of women in late pregnancy are less impulsive and more cautious and controlled.

Humor Affects Fairness Considerations in the Gain and Loss Contexts

Human decision-making behaviors in social contexts are largely driven by fairness considerations. The dual-process model suggests that in addition to cognitive processes, emotion contributes to economic decision-making. Although humor, as an effective emotional regulation strategy to induce positive emotion, may influence an individual's emotional state and decision-making behavior, previous studies have not examined how humor modulates fairness-related responses in the gain and loss contexts simultaneously. This study uses the Ultimatum Game (UG) in gain and loss contexts to explore this issue. The results show, in the gain context, viewing humorous pictures compared to humorless pictures increased acceptance rates and this effect was moderated by the offer size. However, we did not find the same effect in the loss context. These findings indicate that humor's affection for fairness considerations may depend on the context and provide insight into the finite power of humor in human sociality, cooperation and norm compliance.

Humor drawings evoked temporal and spectral EEG processes

The study aimed to explore the humor processing elicited through the manipulation of artistic drawings. Using the Comprehension-Elaboration Theory of humor as the main research background, the experiment manipulated the head portraits of celebrities based on the independent variables of facial deformation (large/small) and addition of affective features (positive/negative). A 64-channel electroencephalography was recorded in 30 participants while viewing the incongruous drawings of celebrities. The electroencephalography temporal and spectral responses were measured during the three stages of humor which included incongruity detection, incongruity comprehension and elaboration of humor. Analysis of event-related potentials indicated that for humorous vs non-humorous drawings, facial deformation and the addition of affective features significantly affected the degree of humor elicited, specifically: large > small deformation; negative > positive affective features. The N170, N270, N400, N600-800 and N900-1200 components showed significant differences, particularly in the right prefrontal and frontal regions. Analysis of event-related spectral perturbation showed significant differences in the theta band evoked in the anterior cingulate cortex, parietal region and posterior cingulate cortex; and in the alpha and beta bands in the motor areas. These regions are involved in emotional processing, memory retrieval, and laughter and feelings of amusement induced by elaboration of the situation.

Olfactory impairment in Parkinson's disease is a consequence of central nervous system decline

Early diagnosis and timely treatment of Parkinson's disease are essential factors to provide these patients with a longer period of a better quality of life. Olfactory loss is among the first non-motor symptoms of the disease; however, in light of the many causes of smell loss, it is a very unspecific biomarker and should only be used as part of a diagnostic test battery. In this study, we investigated the olfactory response in 71 subjects, consisting of Parkinson's disease patients, hyposmic and anosmic patients of other causes, and normosmic individuals searching for sensitive, distinct biomarkers for which we used scalp event-related 64-channel electroencephalography and psychophysical tests. The analysis of the global field power indicated significant measurable differences between patients with Parkinson's disease and otherwise olfactory dysfunctional and normosmic individuals. The localization of brain sources, in particular, provides evidence for differences in mainly late EEG-components suggesting a decline of central brain networks as a causal factor for olfactory loss in Parkinson's disease. The findings indicate a different pattern of olfactory processing in patients with Parkinson's disease compared to olfactory dysfunctions of other origin, which provide further insights into the mechanisms behind olfactory dysfunction in Parkinson's.

Laughter is the best medicine: The Second City® improvisation as an intervention for Parkinson's disease

BACKGROUND

Expressive therapies are increasingly incorporated into the management of Parkinson's disease (PD), although there are little objective data assessing their benefits.

OBJECTIVE

Develop and study a novel community Improvisation Theater (IT) program for PD in order to improve quality of life.

METHODS

A prospective, rater-blinded, modified cross-over design study of IT for PD. 22 subjects were randomized 1:1 to active-start (AS) or control-start (CS) groups, controlling for age and Hoehn and Yahr stage. Participants were recruited from the Northwestern PD and Movement Disorders Center. 60 min IT sessions were led by The Second City^® faculty weekly for 12 weeks. The primary aim was to assess feasibility, determined as 70% of participants attending at least 75% of the classes. Exploratory data were obtained comparing pre- and post-intervention outcomes using Wilcoxon signed rank test for UPDRS parts I-IV, PDQ-39, and 5 neuro-QoL measures (communication, anxiety, stigma, depression, and wellbeing).

RESULTS

All 22 participants completed the study. 21/22 (95%) participants attended at least 80% of the classes. All participants indicated that they would recommend the class to others with PD. 21/22 participants enjoyed the class and felt it was beneficial for their symptoms. A significant improvement pre-to-post intervention was seen with the UPDRS part II ADL measure (mean -1.5, p = 0.019).

CONCLUSION

A novel improvisation program can be well-attended, enjoyable, and improve ADL measures among patients with PD of varying ages and disease severity.

The Rationale for Exercise in the Management of Pain in Parkinson's Disease

Pain is a distressing non-motor symptom experienced by up to 85% of people with Parkinson’s disease (PD), yet it is often untreated. This pain is likely to be influenced by many factors, including the disease process, PD impairments as well as co-existing musculoskeletal and/or neuropathic pain conditions. Expert opinion recommends that exercise is included as one component of pain management programs; however, the effect of exercise on pain in this population is unclear. This review presents evidence describing the potential influence of exercise on the pain-related pathophysiological processes present in PD. Emerging evidence from both animal and human studies suggests that exercise might contribute to neuroplasticity and neuro-restoration by increasing brain neurotrophic factors, synaptic strength and angiogenesis, as well as stimulating neurogenesis and improving metabolism and the immune response. These changes may be beneficial in improving the central processing of pain. There is also evidence that exercise can activate both the dopaminergic and non-dopaminergic pain inhibitory pathways, suggesting that exercise may help to modulate the experience of pain in PD. Whilst clinical data on the effects of exercise for pain relief in people with PD are scarce, and are urgently needed, preliminary guidelines are presented for exercise prescription for the management of central neuropathic, peripheral neuropathic and musculoskeletal pain in PD.

The detection and classification of the mental state elicited by humor from EEG patterns

In this paper we investigate the use of EEG to detect the affective state of humor. The EEG of five subjects was recorded while they recalled humorous videos. Extracted frequency features were compared to a control state in which users where asked to remain in a neutral mental state. An ANOVA test performed on the two groups: neutral and humor recall found a statistically significant difference in the frequency range 28-32 Hz for a number of channels including T7 and P7. Both of which presented the greatest statistically significant results with p values of 0.009 and 0.0 respectively Furthermore, we demonstrate that these mental states can be classified using Principal Component Analysis followed by a 3 features Linear Discriminant Analysis resulting in a leave one out classification accuracy of 95%.

The Roles of Dopamine and Hypocretin in Reward: A Electroencephalographic Study

The proper functioning of the mesolimbic reward system is largely dependent on the neurotransmitter dopamine. Recent evidence suggests that the hypocretin system has significant projections to this reward system. We examined the distinct effects of reduced dopamine or reduced hypocretin levels on reward activity in patients with Parkinson’s disease, dopamine deficient, as well as patients with narcolepsy-cataplexy, hypocretin depleted, and healthy controls. Participants performed a simple game-like task while high-density electroencephalography was recorded. Topography and timing of event-related potentials for both reward cue, and reward feedback was examined across the entire dataset. While response to reward cue was similar in all groups, two distinct time points were found to distinguish patients and controls for reward feedback. Around 160ms both patient groups had reduced ERP amplitude compared to controls. Later at 250ms, both patient groups also showed a clear event-related potential (ERP), which was absent in controls. The initial differences show that both patient groups show a similar, blunted response to reward delivery. The second potential corresponds to the classic feedback-related negativity (FRN) potential which relies on dopamine activity and reflects reward prediction-error signaling. In particular the mismatch between predicted reward and reward subsequently received was significantly higher in PD compared to NC, independent of reward magnitude and valence. The intermediate FRN response in NC highlights the contribution of hypocretin in reward processing, yet also shows that this is not as detrimental to the reward system as in Parkinson’s. Furthermore, the inability to generate accurate predictions in NC may explain why hypocretin deficiency mediates cataplexy triggered by both positive and negative emotions.

Humour processing in frontotemporal lobar degeneration: A behavioural and neuroanatomical analysis

Humour is a complex cognitive and emotional construct that is vulnerable in neurodegenerative diseases, notably the frontotemporal lobar degenerations. However, humour processing in these diseases has been little studied. Here we assessed humour processing in patients with behavioural variant frontotemporal dementia (n = 22, mean age 67 years, four female) and semantic dementia (n = 11, mean age 67 years, five female) relative to healthy individuals (n = 21, mean age 66 years, 11 female), using a joint cognitive and neuroanatomical approach. We created a novel neuropsychological test requiring a decision about the humorous intent of nonverbal cartoons, in which we manipulated orthogonally humour content and familiarity of depicted scenarios. Structural neuroanatomical correlates of humour detection were assessed using voxel-based morphometry. Assessing performance in a signal detection framework and after adjusting for standard measures of cognitive function, both patient groups showed impaired accuracy of humour detection in familiar and novel scenarios relative to healthy older controls (p < .001). Patient groups showed similar overall performance profiles; however the behavioural variant frontotemporal dementia group alone showed a significant advantage for detection of humour in familiar relative to novel scenarios (p = .045), suggesting that the behavioural variant syndrome may lead to particular difficulty decoding novel situations for humour, while semantic dementia produces a more general deficit of humour detection that extends to stock comedic situations. Humour detection accuracy was associated with grey matter volume in a distributed network including temporo-parietal junctional and anterior superior temporal cortices, with predominantly left-sided correlates of processing humour in familiar scenarios and right-sided correlates of processing novel humour. The findings quantify deficits of core cognitive operations underpinning humour processing in frontotemporal lobar degenerations and suggest a candidate brain substrate in cortical hub regions processing incongruity and semantic associations. Humour is a promising candidate tool with which to assess complex social signal processing in neurodegenerative disease.