Using a combination of behavioral, psychophysiological, neurophysiological, and brain imaging methods, researchers in our lab investigate how cognition and emotion modulate somatosensory processing in the human brain. In addition, we also explore topics in which pain serves as an important stimulus modality, such as empathy and reinforcement learning. Our long-term goal is to enhance the basic knowledge of cognitive neurosciences, and provide novel insights into relevant neuropsychiatric disorders. Below we highlight some of the main research themes in our lab.
RESEARCH TOPICS
Pain encoding and intensity discrimination
The experience of pain is quite variable across individuals. How do an individual’s cognitive and affective states evaluate and modulate nociceptive information?
In a delayed discrimination paradigm, we discovered that participants’ ability to encode the intensity information of pain was biased by their anxiety and involved a distinct neural stream encompassing the medial thalamus, medial prefrontal cortex, and amygdala (Tseng et al., 2017, The Journal of Neuroscience). When participants discriminated painful stimulus intensities, their discrimination ability was modulated by their vigilance to pain. This modulation was mirrored by an enhanced coupling within prefrontal-thalamic attention networks, which allow the superior prefrontal region to estimate the relative intensity differences between noxious stimuli (Yang et al.,2018, Pain). These studies exemplify how human responses to pain are modulated by cognition and emotion.
In a delayed discrimination paradigm, we discovered that participants’ ability to encode the intensity information of pain was biased by their anxiety and involved a distinct neural stream encompassing the medial thalamus, medial prefrontal cortex, and amygdala (Tseng et al., 2017, The Journal of Neuroscience). When participants discriminated painful stimulus intensities, their discrimination ability was modulated by their vigilance to pain. This modulation was mirrored by an enhanced coupling within prefrontal-thalamic attention networks, which allow the superior prefrontal region to estimate the relative intensity differences between noxious stimuli (Yang et al.,2018, Pain). These studies exemplify how human responses to pain are modulated by cognition and emotion.
Pain modulation by stimulus expectancy
Our subjective experience of pain is largely shaped by expectations. How do top-down expectations interact with bottom-up nociceptive inputs to modulate pain perception?
In a stimulus expectancy paradigm, we found that positive expectations (expectations of decreased pain) and negative expectations (expectations of increased pain) engaged separate brain regions encoding the mismatch between actual and expected pain (i.e., prediction error) and involved opposite coupling with the descending pain modulatory system. Interestingly, positive and negative expectations produced correlated pain rating changes and brain activation. These findings suggest that aversive prediction error signals underlie stimulus expectancy effects on pain, and positive expectation- and negative expectation-related modulation mechanisms are interrelated. These mechanisms help to explain why we humans can adapt quickly and appropriately to noxious stimuli whose intensity deviates from our expectations. (Shih et al., 2019, The Journal of Neuroscience).
In a stimulus expectancy paradigm, we found that positive expectations (expectations of decreased pain) and negative expectations (expectations of increased pain) engaged separate brain regions encoding the mismatch between actual and expected pain (i.e., prediction error) and involved opposite coupling with the descending pain modulatory system. Interestingly, positive and negative expectations produced correlated pain rating changes and brain activation. These findings suggest that aversive prediction error signals underlie stimulus expectancy effects on pain, and positive expectation- and negative expectation-related modulation mechanisms are interrelated. These mechanisms help to explain why we humans can adapt quickly and appropriately to noxious stimuli whose intensity deviates from our expectations. (Shih et al., 2019, The Journal of Neuroscience).
In another stimulus expectancy paradigm combining emotion regulation and computational modeling, we revealed that the relative emotional responses between expectations and sensory inputs modulated their integration to form pain perception in healthy subjects. These phenomena involved brain regions processing anxiety for negative expectations and processing pleasantness for positive expectations. For negative expectations, subjects’ anxiety also appeared to impair the updating of expectations via suppressed prediction error signals, thus perpetuating negative expectancy effects. This study highlights the important role of emotions when pain experiences are shaped by stimulus expectancy, and adds to the growing studies investigating the computational mechanisms behind pain modulation by stimulus expectancy in humans. (Tsai et al., 2024, The Journal of Neuroscience).
Tactile detection and discrimination
While perceiving somatic stimuli, the ability to accurately discriminate their spatial and temporal properties is essential for human behavior, but how does our brain differentiate these properties?
In a tactile discrimination paradigm, we found that tactile detection elicited activation specifically involved in spatial discrimination within the right inferior and superior parietal lobules, and the functional connectivity between these two regions predicted individual spatial discriminability. In stark contrast with spatial discrimination, tactile detection produced little activation specifically related to temporal discrimination. The revealed close relationship between detection and spatial discrimination not only elucidates the substantial influence of sensory detection on spatial information processing, but aids in explaining why we can promptly and precisely direct our response to a somatic stimulus from the external world. (Huang et al., 2022, Cerebral Cortex).
We are currently examining the link between somatosensory and motor circuits to see whether the revealed mechanisms could explain sensorimotor deficits in relevant neurological disorders.
In a tactile discrimination paradigm, we found that tactile detection elicited activation specifically involved in spatial discrimination within the right inferior and superior parietal lobules, and the functional connectivity between these two regions predicted individual spatial discriminability. In stark contrast with spatial discrimination, tactile detection produced little activation specifically related to temporal discrimination. The revealed close relationship between detection and spatial discrimination not only elucidates the substantial influence of sensory detection on spatial information processing, but aids in explaining why we can promptly and precisely direct our response to a somatic stimulus from the external world. (Huang et al., 2022, Cerebral Cortex).
We are currently examining the link between somatosensory and motor circuits to see whether the revealed mechanisms could explain sensorimotor deficits in relevant neurological disorders.
Pain habituation
Habituation to pain, a behavioral response decrement that occurs after repetitive painful stimulation, is not only an endogenous analgesia mechanism, but adaptive for animals to pursue valuable goals under threat. Despite the wide studies on the peripheral mechanisms associated with pain habituation, the cerebral correlates of habituation to pain remain incompletely understood. In this line of work, we aim to explore the cerebral mechanisms underlying pain habituation from a motivational-ethological perspective. Given chronic pain has been posited to emanate from aberrant habituation to pain, this study will hopefully provide new insights into the pathogenic mechanisms and therapeutic strategies for chronic pain.
Reward and punishment learning
Reward and punishment are important modulators of reinforcement learning to guide human behaviors. Although humans usually learn to maximize reward and minimize punishment at the same time in daily life, the mutual influence between reward and punishment learning remain largely unknown. With this in mind, we design a probabilistic instrumental learning task to address this issue. Using computational models, we are testing several hypotheses that possibly explain the complex interaction between reward and punishment learning. We expect that the results obtain in this project will characterize the distinct and shared mechanisms between learning from positive and negative outcomes.
Empathy
Empathy plays an important role in human emotional experiences and social interaction, and impaired empathy is a characteristic of many neuropsychiatric disorders. Although understanding the feelings of others is itself an emotional process, the relationship between self-related basic emotions (e.g., happiness and sadness) and attributed emotions remains unclear. In this project, we plan to recruit healthy adults and patients with neuropsychiatric disorders showing impaired empathic responses to investigate how emotion processing modulate human empathy. The results of this research will not only enhance current knowledge about the neural underpinnings of social emotions, but inform investigations on relevant neuropsychiatric disorders.