Shane / Ph.D. / LMT The Primal Sense

The Psychology of Touch
1. Auflage 2025
ISBN: 979-8-31780060-4
Verlag: BookBaby
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 85 Seiten

Reihe: The Primal Sense

The Primal Sense is reviews the nature of touch and is geared to those in the health professions and healing arts who use some form of manual therapy. It provides both the standard information about the sense of touch and bolsters it with the latest findings in neuroscience and psychology. The Primal Sense explores the nature of touch in an evidenced-based discussion regarding the different models of touch along with cultural influences; the neuroscientific aspects of the touch system; the social, emotional, and development impact of touch; applying touch in the context of clinical intimacy and healing. Lastly, it offers some useful exercises to enhance the reader's own sense of touch.

Paul Shane, Ph.D., LMT is licensed in medical massage, certified in Structural Integration and trained in Acupressure and Reflexology. He has advanced education in clinical psychology, history of psychology, and philosophy of psychology. Dr. Shane worked for more than twenty years as a college lecturer in psychology and massage therapy. He currently serves as the Co-Founder and Director of Academic Content at the Center for Bodymind Education-an online learning resource-and is author of Principles of Somatic Psychology: Am Evidence-Based, Transdisciplinary Approach for the Holistic Healthcare Professions and Body Psychology 101: An Introduction to the Somatopsychic Perspective. For more information, visit: www.centerforbodymindeducation.com.

Autoren/Hrsg.

Shane, Paul

Ph.D.,

LMT,

Leseproben

Chapter Two The Neurophilosophy of Touch

KEY LEARNING POINTS

• The skin is the largest organ of the body. It is intimately tied to the brain via the hypothalamic-pituitary-adrenal (HPA) axis thus creating a brain-skin connection. The skin is an organ of emotion and identity.
• The function of touch includes not just the body, but the body-ego boundary space around the body.
• Touch is a function of body consciousness which is composed of four neural streams of experience.
• The somatosensory system is composed of peripheral afferent fibers which innervate mechanoreceptors in the skin and then travel to the dorsal column.
• Afferent fibers are known as Aß fibers or C-tactile fibers and detect gentle, caressing touch sensations.
• C-tactile fibers are associated with emotional experiences of pleasant or unpleasant including feelings of affection and arousal.
• C-tactile fibers transmit pleasurable at a preferred soft touch velocity of three to five centimeters per second at normal skin temperature.
• C-tactile fibers probably contribute to the sense of body ownership.
• The parietal lobes process cutaneous and proprioceptive information. The posterior parietal cortex, premotor, and motor areas control for touching objects.
• Massage and gentle touch activate the peripheral nervous system which in turn activates the Default Mode Network (DMN) which is responsible for inducing relaxation, daydreaming, drowsiness, and is central to one’s sense of bodily self.
• A substantial portion of the sensory-motor cortex is devoted to the hands.
• Hands are involved in thinking, problem-solving, calculating, and social interactions thus making them organs of contact, perception, and communication.

Embodied Consciousness, Touch, and Space

Touch differs from the other senses in that it gives us a stronger sense of reality than just seeing or hearing and even tasting and smelling. It brings a kind of experiential urgency in our consciousness (Ratcliffe, 2013). Thinking about touch must be framed within the context of body consciousness. Touch is guided by consciousness and, in turn, changes consciousness. Touch is a function of body consciousness which is composed of four neural streams of experience. These streams combine to give us a seamless whole sense of being embodied. Each stream has its own experiential purpose: body-ownership, body-location, self-agency, and a first-person perspective. Body-ownership is consciously identifying with one’s body and its parts as one’s own. Body-location is being aware of knowing one’s body and its parts are here and now in this specific place and time. Self-agency is knowing that one’s actions are self-initiated and self-controlled. First-person perspective is having a uniquely personal, embodied point-of-view. These four factors are the essence of embodied consciousness and the sense of touch is behind each one (Gauthier et al., 2020; Serino et al., 2013; Sidarus, Vuorre, & Haggard, 2017; Tsakiris, 2010).

These aspects are all represented within a highly specialized neural map in the brain called the body matrix or, as is more commonly known, the body schema. The body matrix is the experience of being a body including the peripersonal space immediately surrounding it. Its purpose is “to maintain the integrity of the body at both the homeostatic and psychological levels, and to adapt to changes in our body structure and orientation…” (Moseley, Gallace, & Spence, 2012, p. 39). The sensory inputs for the body matrix combine visual, tactile, and proprioceptive experience. Body consciousness arises from the multisensory processing in the temporoparietal lobes, premotor cortex, posterior parietal cortex, and extrastriate cortex (Blanke, 2012). Interoceptive and emotional signals are processed in the insula constituting another fundamental component of self-awareness. The bodily self is experienced as being in the here-and-now by the integration of multisensory body and vestibular signals at the temporo-parietal junction. The temporo-parietal junction is an important processing area for multisensory information in the forms of touch, proprioception, visual perception and vestibular information of body balance and alignment in the gravity field (Blanke et al., 2004; Blank & Mohr, 2005; Blanke et al., 2002).

Certain brain centers constantly monitor the physical positions head and hands in space in relation to the body and its movements around nearby objects to orient ourselves to the ever-changing space around us. This is done by our unconsciousness comparing the changing body schema to the space around the body. The coordination of body and spatial navigation includes seeing, hearing, and sensing the body’s position (Holmes, & Spence, 2004). For the body to interact with its surrounding environment requires a neural map of the body-in-space. Each body movement necessarily changes the distance and orientation of the body in relation to its target objects. As the body changes—as well as the surrounding environment—so too does the peripersonal space. The body-in-space map is continually updating itself in response to body actions by either enlarging or contracting the peripersonal space as required. Changes in the space around the hands—which are a specialized area of the peripersonal space are caused by hand movements. This principle includes the whole body in response to its actions. The experience of personal space is modified by the vestibular system (Pfeffer et al., 2017). Besides body movements and tool use affecting the shape of peripersonal space, other changes are induced by interpersonal interactions with others (Dijkerman, 2015; Teneggi et al., 2013), personality traits such as anxiety and defensiveness (Lourenco et al., 2011; Sambo & Iannetti, 2013), and the size and shape of the physical body itself (Longo & Lourenco, 2007).

Our hands operate at the limits of peripersonal space to touch, grasp, and manipulate objects. Any objects outside of our body-space require us to move toward them (Rizzolatti et al., 1997). This is a very provocative idea in that it would mean that our sensory experience, as it extends beyond the wall of our actual body, integrates the immediate environment around our bodies into our body consciousness, thus making the space around us a kind of conscious space and no less a part of our body than our skin or bones.

The Somatosensory System

Sensory Receptors in the Skin

The somatosensory system is part of the sensory nervous system that allows perception of touch, pressure, pain, temperature, position, movement, and vibration. It is a neural network that recognizes objects, different textures, and social interactions. It begins with stimulation of the peripheral sensory nerve fibers. Cutaneous fibers are myelinated and innervate mechanoreceptors for touch while the other fibers detect thermal and pain stimuli.

Psychophysical and neurophysiological studies paint a complex picture of the peripheral neural pathways which detect tactile sensations in relation to the higher brain levels where perceptions are formed. The somatosensory system decodes a wide range of tactile stimuli and thus endows us with a remarkable capacity for object recognition, texture discrimination, sensory-motor feedback, and social exchange.

The first step in somatosensory perception begins with the activation of primary sensory neurons whose cell bodies reside within the dorsal root ganglia. Dorsal root neurons are pseudo-unipolar with one axon that extends to the periphery and a sister axon that penetrates the spinal cord and synapses with second-order neurons in the spinal cord gray matter and, in some cases, the dorsal column nuclei of the brainstem. Within the exteroceptive somatosensory system, a large portion of our sensory body map is devoted to scanning for potentially dangerous stimuli. Most dorsal root neurons are attuned to pain and thermal changes. The perception of harmless or harmful sensations relies on two types of sensory neurons: low-threshold mechanoreceptors (LTMRs) that react to innocuous physical contact and high-threshold mechanoreceptors (HTMRs) that respond to harmful physical changes. HTMRs are nociceptors tuned to stimuli that threaten damage to the body (Lallemend & Ernfors, 2012). Both receptors function by sensing the deformations in the skin’s surface (Gardner & Johnson, 2013a).

LTMRs are distinguished by their conduction speed, adaptation to new stimuli, and their cutaneous end organs which detect a certain range and type of stimulation. LTMRs are divided into two major types by skin quality: hairy and non-hairy. Hairy skin is a defining characteristic of mammals. It regulates body temperature, protects against environmental threats, and contributes to tactile perception. We rely heavily on hairy skin for a variety of touch sensations, ranging from social exchanges to our ability to detect the presence of foreign objects on our skin. Hair follicles are specialized mechanosensory organs. Human and non-human primate studies of tactile perception from hairy skin stimulation are far fewer in comparison to studies of non-hairy skin. The density and intricate innervation patterns of hair follicles coupled with the large amount of hairy skin areas across the body means most primary somatosensory neurons are designated to hairy skin. Non-hairy skin or glabrous skin holds four kinds of sensory end organs: Pacinian corpuscles, Ruffini nerve endings, Meissner corpuscles, and Merkel’s...