Consoling touch is a pro-social behavior involving physical contact between a distressed individual and a caregiver. The physical contact, most commonly recognized in the form of a hand hold or embrace, is intended to comfort one or more of the participating individuals. Consoling touch is intended to provide consolation - to alleviate or lessen emotional or physical pain. [1] This type of social support has been observed across species and cultures. [2] Studies have found little difference in the applications of consoling touch, with minor differences in frequency occurrence across cultures. These findings suggest a degree of universality. [3] [4] It remains unclear whether the relationship between social touch and interpersonal emotional bonds reflect biologically driven or culturally normative behavior. Evidence of consoling touch in non-human primates, who embrace one another following distressing events, suggest a biological basis. [2] [5] Numerous studies of consoling touch in humans and animals unveil a consistent physiological response. An embrace from a friend, relative, or even stranger can trigger the release of oxytocin, dopamine, and serotonin into the bloodstream. [6] [7] These neurotransmitters are associated with positive mood, numerous health benefits, and longevity. [8] [9] Cortisol, a stress hormone, also decreases. [10] Studies have found that the degree of intimacy and quality of relationship between consoler and the consoled mediates physiological effects. [11] In other words, while subjects experience reduced cortisol levels while holding the hand of a stranger, they exhibit a larger effect when receiving comfort from a trusted friend, and greater still, when holding the hand of a high quality romantic partner.
The importance of consoling touch was first explored by Harry Frederick Harlow (Oct 31, 1905 – Dec 6, 1981). From 1950 through 1970, Harlow conducted controversial research on rhesus monkeys observing maladaptation resulting from maternal-separation and social isolation. [12] Infant monkeys were separated from their biological mothers and given two inanimate surrogate mothers. Cheekily referred to as ‘Iron Maidens’, the first of the two surrogates was constructed of wire and contained a feeding mechanism. The second contained no food and was constructed of rubber and soft terrycloth. In all variations of the paradigm the infants spent significantly more time clinging to the cloth mother. Only when the monkeys were hungry did they leave the terrycloth, only to return to it after eating. Monkeys accompanied by iron maidens behaved differently in novel environments than those in complete isolation. When chaperoned by a surrogate mother monkeys explored new environments, retreated to the surrogate when startled, only to continue exploring thereafter. Monkeys put in novel environments without an iron maiden cowered in the nearest corner, too fearful to explore. Those raised in complete isolation developed marked disturbed behavior such as pacing in cages, staring blankly, and self-mutilation. When introduced to other rhesus's, those raised in isolation did not socialize, kept separate from the group, and refused to eat. Harlow rehabilitated socially inept monkeys by enclosing them with a non-threatening, well socialized other. Harlow observed these social pair interactions, calling them "the isolate and the therapist'. Upon introduction, the isolate huddled in a corner. The therapist reacted by embracing the isolate. With consoling touch and modeling of social interaction, isolates were indistinguishable from therapists after one year. Harlow concluded that social rehabilitation is possible, however there may be a critical period, much like language development in humans. The need for close comforting physical contact became known as contact comfort. [13] [14] Contact comfort is believed to be the foundation of attachment and serves as the basis for consoling touch.
Extensive research has documented the importance of physical touch in human emotional and physical wellbeing. From a developmental perspective touch plays a vital role in infants' physical and cortical growth, stress relief, and secure attachment formation. [15] [16] Nurturing touch is positively associated with children's neuronal development thus determining the trajectory of their behavioral and cognitive growth. [17] [18] [19] Though no laboratory studies exist due to ethical considerations, data emphasizing the necessity of consoling touch was taken from orphanages where the caretaker to child ratio was 1:25. Children deficient in consoling touch during critical developmental stages had between 20%-30% less brain mass than children of similar age who received sufficient socialization. [20] In a 1997 study, Dawson et al. monitored the neural functioning of children born to depressed mothers. A key symptom of maternal depression is reduced social touch between mother and child. The electroencephalogram (EEG) results of children with depressed mothers had markedly reduced activity in the left frontal lobe. The abnormality remained consistent with the mother's condition throughout the duration of the three-year study. The children of mothers who managed to diminish depressive symptoms before their child's first year later developed a more normal brain pattern. [21] The likelihood of full neural recovery lessens as a child ages due to sensitive periods for brain development, the first year and a half being the most critical. [22]
From a therapeutic perspective consoling touch provides pain alleviation and facilitates healing. [23] [24] [25] In a 1993 study of young adults undergoing chemotherapy, hand holding was rated to be a significantly effective coping strategy in ameliorating treatment-related pain. Overwhelmingly, patients preferred to hold the hand of a close relative or partner. Consoling touch functioned to reduce anxiety associated with impending treatments and served as a source of security. Patient's subjective experience of treatment-related pain was significantly reduced when they felt more secure, less tense, and had social support. [26] Marshall Klaus's 1995 work demonstrated the power of social touch in labour and delivery. He found women receiving consoling touch during delivery had reduced labour duration, reported less anxiety and physical pain, and had reduced need for caesarean section. [27]
Numerous studies have been conducted exploring pain mitigation and consoling touch between romantic partners. From electric shocks to temperatures too hot for touch, holding the hand of a loved one decreases physical pain perception. [11] In 2018 couples were brought into a lab and administered mild heat pain while undergoing EEG. Not only were pain ratings significantly reduced in the hand holding condition, couples exhibited what is known as brain-to-brain coupling, or neural synchrony. [28] This means neural firing, both topographically and temporally, matches that of another party. [29] This mechanism is hypothesized to be an integral feature of empathy and shared experience. Neural synchrony is most easily detected in couples during shared experience, such as laughter. [29] Importantly, social touch nor neural synchrony are analgesics. Consoling touch can reduce pain perception, but not eliminate it entirely.
Recent research has shown that consoling touch modulates emotional responses as well as physical. [30] [31] In a 2019 study the neurobehavioral correlates of consoling touch were examined by showing participants photos of recently deceased relatives while undergoing functional magnetic resonance imaging (fMRI). Participant brain activity was monitored in two conditions, either in solitude, or while holding the hand of a significant other. Activation varied in several brain areas. Reduced reactivity was reported in the anterior cingulate cortex (ACC) and cerebellum in the hand-holding condition. [32] The ACC has neural connections to both the limbic system, the emotional center, and the prefrontal cortex, known for higher cognitive function. The ACCs location, paired with numerous empirical studies, confirm its involvement in emotion and pain regulation. [33] The cerebellum, located in the brainstem, is classically responsible for coordinating voluntary movements; however, recent work suggests it may play a role in emotional valence determination. [34]
A similar fMRI experiment evaluated the neurological effects of viewing moderately disturbing images while holding the hand of a significant other. Connectivity between the anterior insula and the ACC decreased during partner touch. The anterior insula is known for emotional and olfactory appraisal with an observed focus on disgust. [35] [36] Decreased connectivity between these two regions in the hand holding condition suggest that consoling touch elicits a buffering effect. [37]
Consoling touch has an emotional component that utilizes different neural networks and nerves than physical sensation processing alone. [31] This distinction has been described by studies examining discriminative touch versus affective touch. Discriminative touch conveys information regarding pressure, vibration, or stretching of the skin. This kind of processing involves type A nerve fibers, which relay information very quickly to the brains sensory regions. Affective touch, however, involves type C nerve fibers. Unmyelinated, slower traveling, type C nerves communicate pain signals, temperature, and social touch. [38] [39] In humans, type C nerves have the greatest response to soft strokes from stimuli matching skin temperature. [40] These afferent nerves also exhibit a tuning curve for caressing speed specific to that which an individual finds most pleasant. The 'social touch hypothesis', coined by Håkan Olausson in 2010, proposes that C afferent nerve fibers are most sensitive to tactile stimuli occurring during close social interaction. [39]
Much of the understanding of affective and discriminative touch can be attributed to a woman known as 'Patient G. L'. Patient G. L. had Guillain-Barré syndrome, a rare autoimmune disorder wherein an immune system attacks the body's own muscle and sensory neurons. [41] Due to the condition, Patient G. L. lacked type A nerve fibers, while type C remained intact. Though the patient could not perceive physical contact, such as pressure on her skin, she still reported an emotional response to consoling touch. Further functional magnetic resonance imaging (fMRI) examination confirmed the patient lacked activation in the somatosensory cortex during touch.
Because the somatosensory cortex is responsible for type A processing, a healthy control would exhibit activation of these areas. [42] [43] Instead, patient G. L. showed heightened activation in the posterior insula. The posterior insula is not sensitive to visceral input, but is involved in recognition, intensity encoding, and reward assessment. [44] Patient G. L. described being the recipient of social touch as "a faint, hard-to-place, pleasant sensation". [45] Olausson, a professor of clinical neuroscience, has compiled a great deal of work on the somatosensory system. [43] He has identified not only cases like Patient G. L., but her inverse. Numerous adults without type C nerve fibers, but with type A were identified and studied. FMRI data confirmed these patients exhibited activation of the somatosensory cortex with no firing of the posterior insula. [46] These findings are some of the first to confirm C afferent nerve fibers convey emotional and social information involving the reward system while type A communicate tactile information within the somatosensory cortex. [47] [39]
Individuals vary in their preference for consoling touch. It is speculated that culture and upbringing are the greatest determinants. [48] Going beyond environmental factors, there is a notable relationship between tactile experience and the autism spectrum. 96% of individuals on the spectrum report an altered, and largely heightened, sensitivity to tactile input. [49] These variations in nerve processing manifest in different ways, be it wearing very specific fabrics, or avoiding rain because the sensation of drops on the skin is painful. [50] Kevin Pelphrey, a clinical neuroscientist at Yale, recently evaluated response to social touch in non-autistic and autistic children. Children had their arms gently grazed with a paint brush and had their palms touched by a caregiver while in an fMRI scanner. Non-autistic children elicited the expected response. There was heightened activation of C afferent nerves and the posterior insula in the palm touch condition while type A nerves responded to the paintbrush condition. The children on the Autism spectrum, however, elicited a similar neuronal response in both conditions with marked activation of the somatosensory cortex. [48] The findings raise the possibility that individuals on the spectrum may not be extracting social information from touch. [49] These findings are preliminary and cannot be used to assume individual preference or experience of social touch.
A phantom limb is the sensation that an amputated or missing limb is still attached. It is a chronic condition which is often resistant to treatment. When the cut ends of sensory fibres are stimulated during thigh movements, the patient feels as if the sensation is arising from the non-existent limb. Sometimes the patient might feel pain in the non-existent limb. Approximately 80–100% of individuals with an amputation experience sensations in their amputated limb. However, only a small percentage will experience painful phantom limb sensation. These sensations are relatively common in amputees and usually resolve within two to three years without treatment. Research continues to explore the underlying mechanisms of phantom limb pain (PLP) and effective treatment options.
The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons, neural pathways, and parts of the brain involved in sensory perception and interoception. Commonly recognized sensory systems are those for vision, hearing, touch, taste, smell, balance and visceral sensation. Sense organs are transducers that convert data from the outer physical world to the realm of the mind where people interpret the information, creating their perception of the world around them.
The claustrum is a thin sheet of neurons and supporting glial cells in the brain, that connects to the cerebral cortex and subcortical regions including the amygdala, hippocampus and thalamus. It is located between the insular cortex laterally and the putamen medially, encased by the extreme and external capsules respectively. Blood to the claustrum is supplied by the middle cerebral artery. It is considered to be the most densely connected structure in the brain, and thus hypothesized to allow for the integration of various cortical inputs such as vision, sound and touch, into one experience. Other hypotheses suggest that the claustrum plays a role in salience processing, to direct attention towards the most behaviorally relevant stimuli amongst the background noise. The claustrum is difficult to study given the limited number of individuals with claustral lesions and the poor resolution of neuroimaging.
The insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus within each hemisphere of the mammalian brain.
Affective neuroscience is the study of how the brain processes emotions. This field combines neuroscience with the psychological study of personality, emotion, and mood. The basis of emotions and what emotions are remains an issue of debate within the field of affective neuroscience.
Microneurography is a neurophysiological method employed to visualize and record the traffic of nerve impulses that are conducted in peripheral nerves of waking human subjects. It can also be used in animal recordings. The method has been successfully employed to reveal functional properties of a number of neural systems, e.g. sensory systems related to touch, pain, and muscle sense as well as sympathetic activity controlling the constriction state of blood vessels. To study nerve impulses of an identified nerve, a fine tungsten needle microelectrode is inserted into the nerve and connected to a high input impedance differential amplifier. The exact position of the electrode tip within the nerve is then adjusted in minute steps until the electrode discriminates nerve impulses of interest. A unique feature and a significant strength of the microneurography method is that subjects are fully awake and able to cooperate in tests requiring mental attention, while impulses in a representative nerve fibre or set of nerve fibres are recorded, e.g. when cutaneous sense organs are stimulated or subjects perform voluntary precision movements.
The simulation theory of empathy holds that humans anticipate and make sense of the behavior of others by activating mental processes that, if they culminated in action, would produce similar behavior. This includes intentional behavior as well as the expression of emotions. The theory says that children use their own emotions to predict what others will do; we project our own mental states onto others.
Tactile discrimination is the ability to differentiate information through the sense of touch. The somatosensory system is the nervous system pathway that is responsible for this essential survival ability used in adaptation. There are various types of tactile discrimination. One of the most well known and most researched is two-point discrimination, the ability to differentiate between two different tactile stimuli which are relatively close together. Other types of discrimination like graphesthesia and spatial discrimination also exist but are not as extensively researched. Tactile discrimination is something that can be stronger or weaker in different people and two major conditions, chronic pain and blindness, can affect it greatly. Blindness increases tactile discrimination abilities which is extremely helpful for tasks like reading braille. In contrast, chronic pain conditions, like arthritis, decrease a person's tactile discrimination. One other major application of tactile discrimination is in new prosthetics and robotics which attempt to mimic the abilities of the human hand. In this case tactile sensors function similarly to mechanoreceptors in a human hand to differentiate tactile stimuli.
The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. It has two subdivisions, one for the detection of mechanosensory information related to touch, and the other for the nociception detection of pain and temperature. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of body position and balance (proprioception).
Haptic memory is the form of sensory memory specific to touch stimuli. Haptic memory is used regularly when assessing the necessary forces for gripping and interacting with familiar objects. It may also influence one's interactions with novel objects of an apparently similar size and density. Similar to visual iconic memory, traces of haptically acquired information are short lived and prone to decay after approximately two seconds. Haptic memory is best for stimuli applied to areas of the skin that are more sensitive to touch. Haptics involves at least two subsystems; cutaneous, or everything skin related, and kinesthetic, or joint angle and the relative location of body. Haptics generally involves active, manual examination and is quite capable of processing physical traits of objects and surfaces.
Christian Keysers is a French and German neuroscientist.
Pain empathy is a specific variety of empathy that involves recognizing and understanding another person's pain.
Mirror-touch synesthesia is a rare condition which causes individuals to experience a similar sensation in the same part or opposite part of the body that another person feels. For example, if someone with this condition were to observe someone touching their cheek, they would feel the same sensation on their own cheek. Synesthesia, in general, is described as a condition in which a concept or sensation causes an individual to experience an additional sensation or concept. Synesthesia is usually a developmental condition; however, recent research has shown that mirror touch synesthesia can be acquired after sensory loss following amputation.
Mindfulness has been defined in modern psychological terms as "paying attention to relevant aspects of experience in a nonjudgmental manner", and maintaining attention on present moment experience with an attitude of openness and acceptance. Meditation is a platform used to achieve mindfulness. Both practices, mindfulness and meditation, have been "directly inspired from the Buddhist tradition" and have been widely promoted by Jon Kabat-Zinn. Mindfulness meditation has been shown to have a positive impact on several psychiatric problems such as depression and therefore has formed the basis of mindfulness programs such as mindfulness-based cognitive therapy, mindfulness-based stress reduction and mindfulness-based pain management. The applications of mindfulness meditation are well established, however the mechanisms that underlie this practice are yet to be fully understood. Many tests and studies on soldiers with PTSD have shown tremendous positive results in decreasing stress levels and being able to cope with problems of the past, paving the way for more tests and studies to normalize and accept mindful based meditation and research, not only for soldiers with PTSD, but numerous mental inabilities or disabilities.
Tactile hallucination is the false perception of tactile sensory input that creates a hallucinatory sensation of physical contact with an imaginary object. It is caused by the faulty integration of the tactile sensory neural signals generated in the spinal cord and the thalamus and sent to the primary somatosensory cortex (SI) and secondary somatosensory cortex (SII). Tactile hallucinations are recurrent symptoms of neurological diseases such as schizophrenia, Parkinson's disease, Ekbom's syndrome and delirium tremens. Patients who experience phantom limb pains also experience a type of tactile hallucination. Tactile hallucinations are also caused by drugs such as cocaine and alcohol.
C tactile afferents are nerve receptors in mammalian skin that generally respond to nonpainful stimulation such as light touch. For this reason they are classified as ‘low-threshold mechanoreceptors’. As group C nerve fibers, they are unmyelinated and have slow conduction velocities. They are mostly associated with the sensation of pleasant touch, though they may also mediate some forms of pain. CT afferents were discovered by Åke Vallbo using the technique of microneurography.
Interoception is the collection of senses providing information to the organism about the internal state of the body. This can be both conscious and subconscious. It encompasses the brain's process of integrating signals relayed from the body into specific subregions—like the brainstem, thalamus, insula, somatosensory, and anterior cingulate cortex—allowing for a nuanced representation of the physiological state of the body. This is important for maintaining homeostatic conditions in the body and, potentially, facilitating self-awareness.
Meditation and pain is the study of the physiological mechanisms underlying meditation—specifically its neural components—that implicate it in the reduction of pain perception.
Social cognitive neuroscience is the scientific study of the biological processes underpinning social cognition. Specifically, it uses the tools of neuroscience to study "the mental mechanisms that create, frame, regulate, and respond to our experience of the social world". Social cognitive neuroscience uses the epistemological foundations of cognitive neuroscience, and is closely related to social neuroscience. Social cognitive neuroscience employs human neuroimaging, typically using functional magnetic resonance imaging (fMRI). Human brain stimulation techniques such as transcranial magnetic stimulation and transcranial direct-current stimulation are also used. In nonhuman animals, direct electrophysiological recordings and electrical stimulation of single cells and neuronal populations are utilized for investigating lower-level social cognitive processes.
Valeria Gazzola is an Italian neuroscientist, associate professor at the Faculty of Social and Behavioral Sciences at the University of Amsterdam (UvA) and member of the Young Academy of Europe. She is also a tenured department head at the Netherlands Institute for Neuroscience (NIN) in Amsterdam, where she leads her own research group and the Social Brain Lab together with neuroscientist Christian Keysers. She is a specialist in the neural basis of empathy and embodied cognition: Her research focusses on how the brain makes individuals sensitive to the actions and emotions of others and how this affects decision-making.
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