, Giuseppe Alfredo Papa 2, Rocco Salvatore Calabrò 11 IRCCS Centro Neurolesi Bonino-Pulejo, 98124 Messina, Italy
2 Kinestudio, Terme Vigliatore, 97050 Messina, Italy
Abstract
The evidence on how touch-based therapy acts on the brain activity opens novel cues for the treatment of chronic pain conditions for which no definitive treatment exists. Touch-based therapies, particularly those involving C-tactile (CT)-optimal touch, have gained increasing attention for their potential in modulating pain perception and improving psychological well-being. While previous studies have focused on the biomechanical effects of manual therapy, recent research has shifted towards understanding the neurophysiological mechanisms underlying these interventions. CT-optimal touch, characterized by gentle stroking that activates CT afferents, may be used to reduce pain perception in chronic pain conditions and to enhance psychological well-being. Further research is needed to fully elucidate the neurophysiological mechanisms involved and to establish the therapeutic efficacy of CT-optimal touch in various clinical populations.
Keywords
- touch-based therapy
- manual therapy
- CT-optimal touch
- neurophysiological impact
- chronic pain
Touch is one of our five senses that most influences our connection with other
individuals. It is used to interact with the whole environment, as well as to
communicate positive messages, like reassurance, comfort, sympathy, and support
with other individuals. Touch can give both pleasantness, reducing pain, and
unpleasantness [1]. The personal perception of the touch is influenced by
physical characteristics, like softness, temperature, force and velocity.
Touch-based therapy is one of the oldest medical interventions, and it is defined
as passive movements or forces applied to joints and soft tissues, typically
performed by hand [2, 3]. The first organ we keep in contact with during a
touch-based therapy is clearly the skin. The skin, our largest organ, plays a
vital role in how we interact with the world around us. Three types of sensory
fibres innervate the skin: A-Beta (A
This aspect is particularly critical in children. Those raised in institutional settings, where there is a lack of care and associated physical touch, are at a higher risk of behavioural, emotional, and social problems [12, 13, 14]. For instance, Wilbarger et al. [15] examined sensory processing capacities in internationally adopted children, particularly those who had experienced prolonged institutional care. Their studies underscore that post-institutionalized children often suffer long-term sensory processing disruptions due to early deprivation, which impacts their overall functioning and development [13, 15]. In this context, the role of touch in mammalian development is fundamental, as it allows management of anxiety, stress, depression, pain, and physical illness [16].
In healthcare, touch is an integral part of routine services, particularly in physiotherapy and osteopathy, where touch-based techniques are frequently employed. As a result, an increasing number of studies are examining the neurophysiological effects of touch. These studies have explored how the brain processes both discriminative touch (which involves distinguishing different stimuli) and affective touch (such as pleasant, gentle stroking) [5, 17, 18, 19]. The neurophysiological response to touch triggers the release of specific chemicals and neurotransmitters, leading to neuroendocrine changes, vagal stimulation, reduced stress, pain, and depression, and enhanced immune function [20, 21, 22]. These physiological effects support the clinical benefits of touch-based approaches, such as manual therapy [23, 24] for a wide range of musculoskeletal conditions, including low back pain as well as specific disorders like fibromyalgia [25, 26, 27]. In these disorders, where chronic pain is the predominant symptom, maladaptive neuroplastic mechanisms can easily occur at brain level, leading to changes in brain connectivity [28]. Previous studies have shown a reduction in grey matter volume in both the whole brain and specific regions, such as the cingulate cortex, prefrontal cortex, thalamus, insula, precentral cortex, temporal cortex, and praecuneus, in various chronic pain conditions [29, 30, 31]. During the process of chronification, various modulatory mechanisms have been proposed, including central sensitisation. According to some authors [32, 33], central sensitization is referred to pain hypersensitivity that can be elicited by amplified neural signalling within the central nervous system. The presence of central sensitization in patients with chronic pain can worsen the global outcomes of the patients [34].
To objectively study the role of touch at brain level, several non-invasive methods can be used. For instance, functional magnetic resonance imaging (fMRI) and the blood oxygenation level dependent (BOLD) technique allow the detection of active brain areas by searching for changes in deoxyhaemoglobin, which reflects the underlying neuronal activity and neurovascular coupling, thus providing insights into neural functioning [35]. In addition, electroencephalography (EEG) allows the registration of neurophysiological brain activity, investigating the temporal domain and therefore the real-time neuronal processes that determine the sensation of touch. These neuroimaging devices could be useful to individuate objectively neurophysiological changes due to touch-based interventions in both healthy individuals, but also in people affected by chronic pain.
By reporting the effects of touch on brain structures and functions, this opinion aims to discuss the potential mechanisms through which touch-based therapies, especially CT-optimal touch, can modulate pain perception, alleviate chronic pain, and potentially improve therapeutic outcomes in patients suffering from chronic musculoskeletal and other conditions causing chronic pain.
Among touch-based interventions, CT-optimal touch is a gentle stroking of the
skin, which activates the small unmyelinated CT afferent nerves. This type of
touch, also known as gentle touch, can produce pleasant sensations [36, 37]. The
significance of CT-optimal touch lies in its ability to influence pain processing
pathways, offering a potential approach for pain relief in various clinical
settings. Recent behavioral studies have shown that CT-optimal touch can reduce
pain perception in humans [38, 39, 40]. This can be explained by a model suggesting
that the CT-afferent system interacts with the medial pain system at various
levels of the central nervous system [41]. In fact, it may inhibit pain signals
at the dorsal horn of the spinal cord, thereby preventing higher-order processing
of these signals [42]. Additionally, it can downregulate several cortical areas,
such as the insula and anterior cingulate cortex (ACC), which play key roles in
the affective aspects of pain perception [39, 43, 44]. This mechanism places
CT-optimal touch as a valuable tool for targeting both the sensory and emotional
dimensions of pain. Moreover, CT-fibers respond to both static (e.g., hugging and
holding) and dynamic touch, these features being relevant for understanding the
perception of social touches, like hugging and handholding. According to Ali
et al. [45], static touch was preferred over dynamic CT non-optimal
touch (i.e., stroking touch at a velocity of
Thus, while CT-optimal touch shows promise in pain management, further research is needed to explore its limitations, particularly in conditions that alter normal touch perception.
Although it is known that touch-based interventions provide important effects on pain-relief perception, this field of research deserves greater attention in the future. As the number of individuals suffering from chronic pain continues to rise, there is a lack of well-documented non-invasive and non-pharmacological interventions [54]. A systematic review [34] indicates that pain during physical activity frequently hinders adherence, emphasizing the need for pain relief strategies. Therefore, clinicians must thoroughly understand patients’ pain experiences and beliefs to motivate them to follow care programs. It is noteworthy that the underlying mechanisms of chronic pain remain incompletely understood, but studies indicate that musculoskeletal pain and neuropathic pain are associated with changes in the structural and functional connectivity of brain regions involved in pain processing. Notably, the insula, ACC, and prefrontal cortex show connectivity changes linked to increased pain intensity and duration [31, 55]. Due to these largely unknown mechanisms, to discover effective treatments for chronic pain is challenging. Currently, treatment involves a multimodal approach combining pharmacological, non-pharmacological, and physical rehabilitation methods. Nevertheless, many individuals continue to suffer from chronic pain [56]. Based on the presented evidence, CT-optimal touch may be a promising intervention in reducing chronic pain, and it also appears to have a positive effect on other psychological symptoms and distress. For instance, Weze et al. [57] found that the use of CT-optimal touch, alone or in addition to other conventional medical treatments, was found to be a safe intervention for people with psychological conditions (e.g., depression and anxiety). Moreover, Schaub et al. [58] have demonstrated that the use of CT-optimal touch applied during gentle hand massage, in people affected by dementia, can reduce salivary cortisol and amylase levels. These authors suggested that hand massage provided a positive effect on agitation three hours after the intervention, but a greater effect was found in the two weeks after.
However, little is known about the neurophysiological and neurobiological mechanisms of touch-based therapies that stimulate CT-fibers.
The neurophysiological process of touch begins with the activation of
mechanoreceptive afferents in the skin, comprising fast-conducting, myelinated
A
The analgesic effect of touch could be also attributed to a reduction in the
activation of pain-related neural substrates, notably the dorsal ACC and the
anterior IC [69, 70]. Researchers have confirmed the power of touch in modulating
pain [41, 47], which is influenced by two major nociceptive fibers: A
In recent years, numerous non-pharmacological, rehabilitative, complementary and alternative medicine approaches have been developed for the treatment of chronic pain [54]. Among these, virtual reality, for example, has shown promise for managing chronic pain and improving patient outcomes [80]. Similarly, therapeutic exercise has long had a positive impact on chronic pain [81]. But why, then, introduce manual therapy and gentle touch stimulating CT fibers for the treatment of chronic pain conditions?
This question may find a potential answer in the fact that tactile stimulation of CT fibers not only appears to play a role in alleviating pain [25, 46, 47, 52], but also in enhancing psychological well-being [57, 58]. This is especially relevant since chronic pain conditions are often associated with depression and anxiety, which can exacerbate the persistence of pain [82]. Furthermore, it is a technique that does not require significant costs. Introducing gentle touch as part of the treatment for chronic pain is important for several reasons. First, gentle touch therapy, which targets CT-fibers, has been shown to activate pathways in the brain associated with emotional processing and social bonding [18, 36, 52, 67, 78]. This activation can help modulate the perception of pain by fostering a sense of comfort and safety, which is crucial for patients who often feel isolated and distressed by their chronic condition. Moreover, chronic pain is not just a physical experience but a complex interplay of physical, emotional, and psychological factors [83]. The gentle touch, by engaging CT fibers, directly influences the parasympathetic nervous system, promoting relaxation and reducing stress [39, 57, 74, 78]. This reduction in stress can help break the cycle of pain amplification, where anxiety and mood alteration exacerbate pain perception. Additionally, gentle touch therapy is non-invasive, easy to implement, and carries minimal risk, making it an accessible option for a wide range of patients. It can be used in conjunction with other treatments, enhancing their effectiveness by addressing the emotional and psychological components of chronic pain. This holistic approach not only targets the pain itself but also improves overall quality of life, providing patients with a greater sense of well-being and control over their condition.
In conclusion, touch-based interventions represent a promising avenue for therapeutic intervention, particularly in the context of chronic pain and psychological well-being. The activation of CT afferents through gentle, targeted touch has been shown to modulate neural pathways associated with pain processing and emotional regulation. However, the effectiveness of these therapies in chronic pain patients remains underexplored, given that current research primarily focuses on healthy individuals. The rising prevalence of chronic musculoskeletal pain, coupled with the scarcity of non-invasive treatment options, underscores the need for further investigation into the therapeutic benefits of touch-based interventions. Future studies should prioritize understanding the neurophysiological mechanisms underlying these therapies, ensuring their applicability across various patient populations.
MB, RSC, and GAP designed the research study. GAP provided help and advice on the selection of relevant papers on the topic. MB, GAP, and RSC wrote the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.
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This research received no external funding.
The authors declare no conflict of interest. Rocco Salvatore Calabrò are serving as one of the Guest editors and Editorial Board Members of this journal. We declare that Rocco Salvatore Calabrò had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Gernot Riedel. Giuseppe Alfredo Papa is from a private practice. We declare that there is not any form of conflict of interests.
References
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