Physics and Technology in Medicine Vol. 3 No. 1 (June) 2022, 1 - 7 http://myjms.mohe.gov.my/index.php/ptm
Review Article
The Variation in Imaging Method of Activation Detection Associated with Pain- Love-Empathy Brain Responses
A
HMADA
HYAT,N. A., S
AZALI,S. N. A. & *T
AMAM,S.
ABSTRACT
The brain is the main organ that processes a lot of information, including emotion and cognitive behaviour. This paper aims to highlight the dynamic reorganization of the brain connectivity model associated with pain, love, and empathy responses. Various approaches in cognitive neuroscience use functional neuroimaging methods to determine the brain activation areas via visual stimulus, emotion label inventories, face recognition, and physical pain stimulation. The brain activation areas were recognized according to the types of tasks chosen for the participants, such as emotional expression, face detection, and physical pain-induced tasks. These three emotional categories have their respective neural correlation and share some activation areas that comprise empathy-pain and love-pain related. This area of research has brought many benefits in the healthcare sector in which physicians and psychologists, as well as other people, understand and explore more about their body functions, thus leading them to foster healthier relationships and emotional awareness.
Keywords: Emotion, neural connectivity, pain, love-empathy, brain response
Faculty of Science and Technology, Universiti Sains Islam Malaysia (USIM), Bandar Baru Nilai, 71800 Nilai, Malaysia
*Corresponding Author: Tamam, S.
Email: [email protected] Tel: +606-7986365
Fax: +606-7986516
Received: 28 October 2021 Revised: 26 July 2022
Accepted for publication: 16 August 2022
Publisher: Malaysian Association of Medical Physics (MAMP) http://www.mamp.org.my/
https://www.facebook.com/MedicalPhysicsMalaysia
Copyright © 2022 Malaysian Association of Medical Physics.
All rights reserved.
INTRODUCTION
Brain imaging studies have become one of the most growing interest research among academicians. This is because understanding neural development changes and their roles in both developments of mental conditions and the effect on treatment efficacy is vital (Lee et al. 2014).
This rapid advancement in the development of the emotional brain generally focuses on the dynamic changes during adolescence, specifically in terms of emotional behaviour (Casey 2015). The adaptive and regulation control of emotion contributes to a significant role in mental health and daily functioning. Although the research on health effects is broad and varied (Kubzansky 2015; Sbarra
& Coan 2018), the relationships between both positive and negative emotions can be narrowed to more subsidiary routes through health behaviours (Sbarra & Coan 2017).
Furthermore, humans are special creatures involved in complex social atmospheres and mostly spend their lives working together and pondering about others. In consequence, previous neuroscience studies engaged with social impact have tried to characterize the neural correlates with experiences (Bernhardt & Singer 2012; Lockwood 2016).
Every human brain is unique and differs in terms of both anatomy and physiology. Nevertheless, cognitive emotion management and control are effective ways to regulate emotional responses (Ochner et al. 2012; Mulej et al. 2015). Empathy is categorized as a vital component of social interaction within the human, especially when relating the emotional experience. This feeling is defined as an ability to share the sentimental states of people, either the closest ones or the strangers, which allows us to predict and understand problems, motivations, and actions (Bernhardt &
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Singer 2012). Preceding research depends on the various perceptions of empathy and its factors, such as sympathy, compassion, or inspiration for prosocial behaviour (Bernhardt & Singer 2012; Kanske et al. 2015; Kogler et al.
2020).
Although the empathic neural responses to other persons always happen spontaneously, they are also immensely regulated by numerous situational and individual factors (Zaki 2014; Feng et al. 2015). Numerous studies have been conducted that are related to the neural correlates of human experience that focus on the observation of other people in pain as an alternative measurement of empathy (Lockwood 2016). According to Enrico Schulz (2010), humans have a very complex experience called pain, which is affected by tissue damage or other unpleasant stimuli and creates unfriendly feelings. However, each human can encounter different pain perceptions, varying widely across different populations (Decety et al. 2010; Christian et al., 2017). This is supported by Lockwood (2016), where pain can be generally defined as the perception of real or endangered tissue damage, including the feeling of unpleasantness (Lockwood 2016). Other than that, the feeling of pain somehow can be connected with love emotion. According to the Oxford English Dictionary, love is defined as ‘a strong feeling of affection’ and ‘a great interest and pleasure in something’ in which the term ‘love’
itself is consistent with ‘pleasure’ in affective neuroscience (Tamam & Ahmad 2017).
METHOD FOR MEASUREMENT OF COGNITIVE RESPONSE
There are various approaches in cognitive neuroscience using functional neuroimaging methods to determine the brain activation areas associated with empathy, pain, and love responses. Visual cues are known to be the most effective technique for conducting research related to emotion regulation. Thirty-three participants were involved in an experiment to determine the physicians’ pain empathy response. They were given visual cues, with two conditions of needle pricking on the body parts. They were divided into two groups to differentiate the empathy pain reaction of physicians from normal people that have no medical experience (Decety et al. 2010). Other than that, the functional Magnetic Resonance Imaging (fMRI) experiment was also conducted in 2015 by Brittany and her team, involving three different visual perspectives as a stimulus and projecting it to the participants. In the experiment, the participants were asked to imagine the pain they experienced by themselves, the person they loved, and the strangers from a third point of view (Christian et al. 2017).
The other researcher, Borja (2020), has investigated brain activity that can voluntarily be modulated and attribute emotion to others by analyzing movie clips from Hollywood. The chosen clips were categorized from movies that have the main character experiencing strong emotional fluctuations (Jimenez et al. 2020). The same method was used in a study that sought to determine the differences in neural correlates between interpreting facial expressions enduring pain and explicitly observing pain through a harmful agent. This involved 48 static images as stimuli showing either a nociceptive tool that affected the right hand or right foot and assisted with a face that expressed the pain.
The control images are also provided to indicate the neutral expression with the normal condition, as shown in Figure 1 (Vachon-Presseau et al. 2012).
FIGURE 1 a) Pain-inducing and neutral reaction from every category, b) the estimated scores of perceived pains (± standard error of the mean) according to each category (Vachon-Presseau et al. 2012)
Apart from that, there is another method that was also used to model the brain activations and connectivity of empathy, pain, and love, which is the labelling of emotion
level inventory. Behavioural data were obtained in an experiment involving four distinct samples with a different number of participants in each category. They were asked to
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answer the emotion label inventory after watching movies that could trigger their emotion, while brain scanning procedures were conducted at the same time. This procedure aimed to deliver an emotional profile of the movie clips enhanced by the brain images gained from the fMRI scanning. Furthermore, the emotion label inventory was able to provide a richer explanation of what that particular candidate had experienced during the projection of the movie clips.
It was complementary aid on the relevance of the subject that can help researchers choose suitable visual cues (Raz et al. 2016). This method was also selected in a study of brain-behaviour relationships by Christov and Iacoboni in 2016. The experiment involved two questionnaires that required 20 participants to answer after they completed the fMRI tasks. They were the Interpersonal Reactivity Index (IRI) and Personal Altruism Level (PAL), which both have distinct goals. The IRI was designed to measure cognitive and emotional empathy mechanisms that consist of twenty- four statements with 5 points ranking. On the other hand, PAL was used to study the nature of prosocial behaviour, including comforting, sharing, and comforting other people (Cristov & Iacoboni 2016).
Alternatively, the neural processing of love emotion regulation study also used face identity recognition as a visual cue to examine the activated parts in the brain. An extended corpus of studies on face perception and identity recognition has been conducted and assisted research on the neurological imaging-related emotional and feeling information compared to any other stimuli (Blank et al.
2014; Vila et al. 2019). This technique has also succeeded in helping Esther Heckendorf (2016) complete the study regarding the neural processing of familiar and unfamiliar children’s faces along with the prospective moderating effect of empathy and childhood familiarity of love withdrawal. A total of forty-nine participants were selected and asked to complete the Handedness Questionnaire, Children’s Report of Parental Behaviour Inventory, and Interpersonal Reactivity Index for analysis purposes (Heckendof et al. 2016).
There was also another approach which is physical pain stimulation, to determine the emotional regulation response, especially the pain. In research to observe the dorsal posterior insula as a fundamental role in human pain, seventeen candidates were scanned during two phases where capsaicin cream was applied to the lower right leg, and the online pain ratings were recorded using a Visual Analog Scale (VAS) (Segerdahl et al. 2015).
CONNECTION OF BRAIN PART ACTIVATIONS WITH DIFFERENT
APPROACHES
Previous studies have indicated that pain and negative emotional developments are scattered across brain regions (Chang et al. 2015; Krishnan et al. 2016; Zhou et al. 2020).
However, different tasks and approaches taken by the researchers might lead to various results. This was proven in a study that used an emotional expression task to reveal the
impacts of local and global motion on emotional perception during movie viewing. This experiment has managed to conclude that brain activity in areas that indicated favoured responses to emotional content was significantly linked over time with frame-wide distinctions in global motion rather than local motion. Furthermore, based on the analysis of imaging data, there was a substantially stronger blood oxygenation level-dependent (BOLD) response to neutral clips in terms of the emotional aspect. This was specifically observed in the right inferior frontal gyrus (IFG), bilateral occipitotemporal cortex, right superior temporal gyrus (STG), right precuneus (PCu), right fusiform gyrus, left inferior occipital gyrus (IOG) and left cerebellum (Dayan et al. 2018). This was mentioned in a review study related to the significant developments in affective neuroscience on cinematic empathy in which IFG was also activated along with other regions, including the anterior insula (AI) and the dorsal anterior cingulate cortex (ACC) when the one suffering from pain is psychologically closer to the observer (Raz & Hendler 2014).
Apart from that, emotion regulation tasks of intrapersonal and interpersonal were also conducted by Hallam (2014) to investigate the neurophysiological processes when involving the regulation of others’
emotions. This experiment has shown that both intrapersonal and interpersonal emotion regulation involved largely overlapping brain regions, including the bilateral frontal cortices, the pre-supplementary motor area (pSMA), and the left temporoparietal junction (TPJ). Another study that used visual stimulation for task emotional expression was related to the neuronal activities of people being happily and unhappily in love (Stoessel et al. 2011). As hypothesized, it was discovered that the BOLD changes have reduced for unhappy lovers in regions linked to emotional and reward circuits, for instance, the frontal brain areas, ACC, insula, posterior cingulate cortex (PCC), precuneus, and the caudate nucleus. These brain regions also play a part across multiple individuals involving positive and negative emotions, for example, sadness, happiness, grief, and also romantic love (Stoessel et al.
2011).
On the other hand, a face detection task has a significant role in the emotional responses of empathic behaviour. This was because the intensity and valence between positive and negative emotions of facial expressions could alter the impact of the inability to respond to the facial cues that were induced by Transcranial Magnetic Stimulation (TMS). This study was able to prove that the dorsomedial prefrontal cortex (dmPFC) area is able to support the impaired performance of TMS in the facial detection task of empathic response (Balconi & Bortolotti 2013). Furthermore, facial expression conveys information vital for social interaction. It is not attained from the expression alone but also from a collection of contextual information such as the scene in which the face appears (Ngo & Issacowitz 2015; Clark et al. 2020) or the facial expression of people surrounding (Hess et al. 2020).
According to a study of the face affectivity for love response, brain areas that process loved faces were located in ACC, PCC, medial orbitofrontal cortex (mOF), frontal
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inferior pars triangularis (FrInfTri), along with smaller clusters observed in other regions, as shown in Figure 2 (Vila et al. 2019).
The neural processing of emotional behaviour is a crucial topic in numerous clinical and non-clinical frameworks. In consequence, Fehr (2014) has developed and explored a video stimulus inventory to study about neural correlation of empathic processing, specifically in complex social circumstances, which included realistic neutral, social-positive, and reactive-aggressive action situations (Fehr et al. 2014). The experiment was able to show the distribution of brain-activated regions across
bilateral precentral and frontal gyri (superior, medial, and middle), mainly in the left cingulate and postcentral gyrus, inferior parietal lobule, and precuneus (Fehr et al. 2014). In order to advance the understanding of neural correlation empathy, Theory of Mind (ToM) and self-other differentiation were investigated together in this research (Reniers et al. 2014). Furthermore, across the area of activation shared, conjunction analyses were done. These three conditions have shown activation in the left frontal pole, a cluster in the middle occipital gyrus, and extended into the parahippocampal gyrus, cuneus, and other regions (Reniers et al. 2014).
FIGURE 2 Brain activations of face-affectivity were found on voxel-wise analysis for loved faces (Vila et al. 2019)
On the other side, an Activation-Likelihood Estimate (ALE) meta-analysis of previous neuroimaging studies was conducted to analyze and synthesize the brain networks that are most consistently involved in processing compassion.
Seven different regions were observed from the result, and they are the middle and medial frontal gyrus, bilateral inferior frontal gyrus, bilateral insula, basal ganglia/thalamus circuitry, and ACC (Kim et al. 2019). The same method was used by Jauniaux (2019) to provide a general quantitative map of brain regions engaged in empathy according to past fMRI research on pain empathy.
Other-oriented tasks from the results showed a larger extent of activations in the core, such as left AI and right anterior midcingulate cortex (aMCC), while secondarily (i.e., in left MFG, right IFG, superior parietal lobule SPL) compared to self-oriented tasks (Jauniaux et al. 2019).
Although numerous fMRI studies have discovered activated regions involved in the emotional regulation, processing of reward and motivation, not much is known about whether romantic love affects the brain’s neural activity during rest. Therefore, a study was conducted by Song (2015) to determine the functional connectivity (FC) across the ‘in-love’ (LG) group, ‘ended-love’ (ELG), and
‘single group’ (SG). The outcome of this particular study was a discovery of a significant increase in FC in the LG across ACC, amygdala, caudate nucleus, NAC, and insula (Song et al. 2015). Many types of love exist and play different roles in emotion control. Hence, a meta-analysis
review was done to compare three distinct loves, including brand love, maternal love, and romantic love. Among these three, maternal love and romantic love mostly share the same brain activations. Romantic love that associates certain brain activations were the right cingulate gyrus, right hippocampus, and left putamen. Other main activated regions were also discovered in this experiment, such as the left caudate head, left thalamus, and left culmen (Watanuki
& Akama 2020).
Moreover, the study of pain matrix and ToM has also drawn much attention from researchers to study a person’s mental state. In a study conducted by Jacoby (2016), the whole-brain analysis for the pain matrix showed activations in bilateral insula, aMCC, secondary sensory (SII), MFG, and other regions (Jacoby et al. 2016). Besides, a study proposed that neural connectivity and activation among the self-other response and top-down control systems indicate or represent the individual differences in prosocial preference and its contextual modulation (Cristov et al.
2016). From the outcome, the result fitted the hypothesis that participants who show greater neural connectivity of self-other response tasks during the scanning should also behave more generously than the group who showed the contrary result. Furthermore, positive correlations were observed from the pain perception experiment found in the somatosensory cortex, posterior insula, and operculum, along with other minimal reactions in other regions (Cristov et al. 2016).
Right Left
Anterior
Posterior
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Nevertheless, the neural correlation between empathy, pain, and love are not always categorized as mutually exclusive components. Instead, these three emotional behaviours can come simultaneously, and they are interrelated with one another. This is because our brain is unique and able to process a lot of information independently without affecting any of them. In 2013, Preis examined whether past pain exposure improved neural activity as a connection of empathy for pain. According to the entire sample of whole-brain analysis, there was a greater activation detected in the pain exposure condition, specifically in the MFC, dmPFC, and retrosplenial cortex (Pries et al. 2013). This connectivity was strongly supported by another experiment involving the functional coupling of emotional processing pain and empathy using an fMRI study. The research identified that AI and aMCC were activated in the brain when the subject experienced the pain of others as it was implicated in emotional attributes of empathy for pain. Furthermore, the neural responses in the left AI inversely correlated with the alexithymia traits, while in contrast, aMCC were positively related to subject sensitivity to others’ pain (Zhou et al. 2020).
As love is categorized as emotional behaviour, it has the ability to modulate pain, and numerous studies have been done to determine whether love can trigger or reduce pain (Tamam & Ahmad 2017). A behavioural study has demonstrated that the visual presentation of romantic partner pictures is necessary to diminish the pain induced for experimental purposes. This is proven when the partner’s pictures reduced the pain as strong as holding the partner’s hands compared to viewing pictures of a stranger (Younger et al. 2010). It was associated with hidden activity in sensory (brainstem and AI) and affective emotion, which consists of the hippocampus, putamen, and anterior cingulate. At the same time, the cognitive area covered supplementary motor area, SFG, and other neural pain connectivity (Younger et al. 2010).
CONCLUSION
The neuroimaging study of emotional development, especially between pain, empathy, and love, provides many benefits to humans in various forms. This is because it can help people understand and explore more about their own body and how it works, thus leading them to foster healthier relationships and emotional awareness. Besides, this area of research also offers initial insight into brain networks regulating another person’s feelings which is relevant to comprehending mental health issues that are affected by social interaction problems.
This review paper replicated the findings of previous research related to the neurophysiological study involving empathy, love, and pain. It has been demonstrated that the fMRI study was the most preferred method to extract data and observe the brain parts activated during the emotional perception tasks. Although pain, empathy, and love are different from one another in terms of the emotional category, there was a discovery by previous researchers that the brain function with the interconnection of these
categories. The overlapping of brain regions and shared activations were found between empathy-pain and love-pain related. In contrast, the relationship between empathy and romantic love was rarely discovered compared to those two connections. Therefore, further studies are needed to clarify the relationship between empathy or self-other regulations with pain perception to discover the overlapping and sharing brain patterns.
ACKNOWLEDGEMENT
This research has been funded by USIM’s Research and Innovation Management Centre under grant number PPPI/FST/0119/051000/16819.
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