Tactile Sensory System Examination - Essay Example

A detailed analysis of the tactile sensory system examining the neuroscience, praxis and sensory modulation in relation to Autism [Name of University] [Date] Introduction Autism is often expressed as a Pervasive Developmental Disorder (PDD) that normally arises in the initial three years of existence. It is more specifically, defined as (DSM- IV, American Psychiatric Association, 1994) “the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interests”. The few of its most frequent symptoms consists of limited social dealings, and atypical or challenging behaviors (Homer et al., 2002), sensory dispensation intricacies (Baranek 2002; Dawson and Watling, 2000), discrepancies in or delayed language development (Smith et al., 2004). ASD, Autism spectrum disorders are enduring neurodevelopmental disorders described as impairments in these three areas of functioning: communication abilities; restricted, stereotyped or repetitive behaviour patterns; and social behavior. Most researchers concur that autism is originated by either abnormal organization within the central nervous system, irregular brain structure, or both. Due to the variation of symptoms, the wide variety in their severity and the functional deficits’ continuum, the term ASDs is now being utilized to report the disparity observed in these children (Wing, 1997). Although there had been several theoretical evidence regarding the causes of autism, nowadays, more specific knowledge is available for the neurological and genetic abnormalities that exist. It’s been proposed that a surplus of axons in particular regions of brain results in an over-connection of these regions. Yet, their connections to other regions of the brain seem to be fragile (Herbert, 2005). It seems to be a need of coordination among these areas of brain. This lack of synchronization seems to affect brain functioning. People with ASDs have trouble conveying dissimilar cognitive functions mutually in an organized way. They suffer from difficulties in organization and planning (Prior & Hoffman, 1990). Synchronizing volition with sensation and movement can be complicated for some. In autism every part of the brain appears to perform on its own (Just et al., 2004) thus lacking a coordination of information. The Sensory Systems The information related to the environment is interpreted through sensory systems. It can be explained as a process within the brain which arranges sensory experiences – sound (taste), touch, gravitational pull, body awareness, movement and sight – into collective information which is then utilized by the individuals in reacting to and learning about the environment. It is the aptitude or failure to construct helpful information from sensory occurrences. The sensory processes occur unconsciously within the brain and central nervous system where the information about pain, temperature, touch, movement and pressure is interpreted (Ayres, 1963). Sensory stimulation is a realization that a sensory organization has been stimulated (e.g. the skin has touched something). Hence it is essential to note that the sensory integration is different from sensory stimulation. Sensory Integration Sensory integration is associated to the way brain arranges and organizes the sensations received by human body through sensory organs. It permits us to gather pieces of information to generate a response; it associates meaning to sensory inputs by evaluating them with prior experiences; it facilitates elevated motor coordination levels and it is the foundation of perception. Each individual experiences varying sensory integration levels. There is a range of ability in sensory integration and processing. Sensory Integrative Dysfunction Around 5-10% of children experience sufficient difficulties with sensory integration that may lead them to have certain learning disabilities, be slow learners, or go through behavioural problems. However, children with the least sensory integrative capabilities typically have great problem in functioning and may be categorized within the analytical categories of autism and severe mental retardation. ASD Sensory Processing Most of the facts describing such disorders originate from retrospective videotape analysis, initial narration of living with autism and parental reports. Findings are confined to studies explaining apparent behaviours pinpointing sensory processing models and do incorporate study exploring neurophysiologic processes. Autism is referred to be a factor leading to Sensory Integrative Dysfunction. Sensory Responding Differences In the literature, mutilations with modulating external sensory input had been extensively accounted as a description of autistic characteristics. However, these intricacies have also been narrated by individuals with ASDs themselves. Disparity in auditory processing is one of the most generally described sensory processing mutilations with a complete range of nonconforming responding noted. Paradoxical visual reaction is also recorded in the literature. Inefficient utilization of eye gaze and evasion of eye contact have been explained as initial social attributes of autism. Over receptivity to tactile input has also been accounted within the literature. Initial clinical information of nonconforming reactions to sensory input can be accounted to Kanner (1943) who was the first to described autism. The first theories on the causes of atypical behaviors among children with autism were based on observations of hypo- or hyper-arousal and unusual reactions to sensory input. Grandin (1995) inscribed of her personal incidences with autism and distinguished for instance that certain clothing textures could turn her fidgety, anxious and distracted. Rogers et al. (2003) learnt that children of age between 21-50 months with ASDs showed noteworthy troubles in taste/smell sensitivity, tactile sensitivity, low energy, auditory filtering, underactive stimulation and weak muscular parts of the sensory profile. Such deficiencies in integrating and processing sensory input can lead to problems in learning, moving and behaving and thus can impact their school, home and social activities. Children with ASDs mostly show an excessive dislike (hyper-responsiveness) to or extreme quest for something in a response to sensory input (hypo-responsiveness). From a scientific outlook, the sensory associated behaviors displayed by individuals with autism are considered to help them in managing with their sensory atmosphere by either avoiding or generating sensory input, consequently a child is extremely confined in his ability to contribute functionally in home, school, or play activities. Though when such children are provided the opportunity to get suitable input within the framework of meaningful activity, the capacity of the CNS to integrate and process sensory input can be improved - and movement, behaviour and learning have the prospect to be improved (Ayres, 1972). A Detailed Analysis of Tactile System Tactile Functioning (Somatosensory) According to Ayres, “The sense of touch is critical in helping us function in the environment on a daily basis” (Ayres, 1979). Continuous tactile stimulation is obligatory for all individuals as it has the capability to keep functioning and organization of human activities. We feel feelings of vibration, pain, movement, pressure and temperature via sensory receiving cells known as receptors. It provides information to help in motor planning, visual processing, cognitive learning, body awareness, social skills and emotional security (Tomcheck & Dunn, 2007). The tactile system is comprised of two components listed below: The protective (shielding/ uh oh!) system is an added primeval component that makes us aware if something might be considered dangerous is stirring our bodies. In that case, the body responds against the environment in order to guard itself from the potential harm by inducing a flight or fight response or it may at times simply alerts the nervous system. The discriminative (Aha!) system is more sophisticated and offers us with particulars about touch (e.g. when something is touching us, pressure of touch, the location of that touch and different features of the body touching us). It was noticed that a victorious tactile system is dependent upon a balance between both of these systems. In case there is an existence of an imbalance, it leads to under-responsive tactile discrimination or tactile defensiveness results. Inadequate tactile discrimination is an outcome of an undeveloped ability to distinguish between tactile occurrences and recalling past experiences. Such an individual will probably have opposition to investigating the environment, fine motor problems, and a discrepancy in utilizing tools to execute ‘everyday’ tasks, as experienced by children suffering from ASDs (Tomcheck & Dunn, 2007). However the scope of aversion or desirability of an object depends on the child him/herself. Moreover, the child might also exhibit hypo and hyper sensitivity to tactile sensations and as a consequence may restrain from soft touch but be unconscious of broken bones. Tactile sensations can generate pessimistic emotional reactions (Ayres, 1972) whereby the child may possibly over-react to convinced tactile experiences (like touching squashy materials) (Wilbarger, 2002). Such an incidence may result in the activation of a ‘flight or fight’ response by the child. These are frequently referred as tactile defensiveness. Various sensory receptors are dispersed throughout the human body and are activated by interoceptive, proprioceptive or exteroceptive input. Exteroceptive input transmits sensory information regarding the body’s communication with the outside environment. Interoceptive input transmits information about internal state of the body and proprioceptive input relays information about pose sense originating from the body and its constituent parts. A sensory receptor’s activation converts into a nerve impulse and is then relayed by the spinal nerves or cranial fibers to their particular relay nuclei located within the central nervous system (CNS). The sensory input is afterwards processed as it advances, through the ascending sensory systems to the cortex of the cerebral hemisphere or to the cerebellum. Sensory input is also conveyed to other portions of the CNS in order to either function to educe a response, or to be integrated into pattern-generating circuitry (Homer et al., 2002). The Ascending Sensory Pathways The ascending sensory pathways, on the basis of their anatomic localization, are categorized into three discrete pathways: the somatosensory pathways, the dorsal column–medial lemniscal (DCML), and the anterolateral system (ALS). The ALS includes the spinoreticular, spinohypothalamic, spinothalamic, spinomesencephalic, and spinotectal tracts. It relays primarily temperature and pain sensation, along with nondiscriminative (rudimentary or poorly localized) pressure, touch, and some proprioceptive sensation. The DCML pathway includes the fasciculus cuneatus, fasciculus gracilis, and medial lemniscus. It relays vibratory, discriminative tactile and position sense. These ascending sensory pathways are the chief avenues that relay the information regarding the body’s dealings with the outer environment, movement and position of its parts, its internal condition to the brain. In all three ascending sensory pathways, the first order neuron cell bodies exist in the dorsal root ganglia. The cognizant perception of sensory input from an external stimuli is arbitrated by the DCML and spinothalamic pathways to the ventral subsequent lateral thalamus nucleus, while sensations that could not reach consciousness are arbitrated by the spinomesencephalic, spinotectal, spinohypothalamic, spinoreticular, and the posterior, rostral and anterior spinocerebellar, and cuneocerebellar tracts. These tracts finish in the reticular formation, mesencephalon, hypothalamus and then cerebellum, respectively. Sensory information may eventually extract a reflex or other motor reaction due to the useful integration of the cerebellum, ascending (somatosensory) pathways, and the somatosensory cortex, along with the descending pathways (motor) and motor cortex. Tactile receptors Tactile receptors include peripheral nerve endings, disc-shaped, of large-diameter myelinated, Aβ fibers. Every disc-shaped terminal is linked with a dedicated epithelial cell called as the Merkel cell which is located in the epidermis’s stratum basale. The Merkel’s discs are located generally in glabrous (hairless), and rarely in hairy skin. These discs retort to discriminative tactic stimuli that assists the distinction of shape, edges and texture of objects. Encapsulated mechanoreceptors Encapsulated mechanoreceptors consist of Ruffini’s end organs, Meissner’s corpuscles and pacinian corpuscles. These lie in the glabrous skin’s dermal papillae of the forearm, lips, sole and palm, and also in tongue’s connective tissue papillae. These corpuscles comprise of the Aβ fibers’ peripheral terminals, which are enclosed with a peanut-shaped (structural) device comprising of a pile of concentric Schwann cells bordered by a capsule made up of connective tissues. They are fast adjusting and are receptive to two-point touch (fine) discrimination, and thus are of great significance to the people with visually disorder by allowing them to read. The largest of mechanoreceptors are Pacinian corpuscle. These are fast adapting and cross sectionally look like an onion. All Pacinian corpuscles comprise of Aβ-fiber terminals, enclosed in layers of adapted fibroblasts that are then covered in a capsule made up of connective tissues. Pacinian corpuscles are present in the hypodermis, dermis, external genetalia, interosseous membranes, ligaments, pancreas, joint capsules, and peritoneum (Wilbarger, 2002). They adapt more rapidly than Meissner’s corpuscles and are assumed to reply to vibratory and pressure stimuli, incorporating tickling sensations. Ruffini’s end organs are positioned in the dermis, underlying hypodermis of skin having hair and joint organs. The Aβ myelinated fibers’unmyelinated peripheral terminals are gradually adapting. They entwine around the center of collagen fibers that is enclosed by a lamellate cellular capsule. Ruffini’s end organs react to collagen bundle stretches or joint capsules and might supply proprioceptive information (Homer et al., 2002). Golgi tendon organs and Muscle spindles are also included in encapsulated mechanoreceptors, but, being specialized functioning receptors, they are described separately. They detect sensory information from the skeletal muscles and relay it to the spinal cord to perform an essential role in generating reflexes and motor control relating the cerebellum (Dunn, 1999). Moreover, sensory information from these receptors is then relayed by DCML pathways, to the cerebral cortex, which arbitrates information regarding position sense, posture, body orientation and its movement. Central Nervous System CNS is one of the three constituents of the nervous system in humans. It mainly consists of brain and the spinal cord. Spinal cord It is the most essential structure between the brain and the body. It is cylindrical in structure, consisting of nervous tissues, including grey and white matter, uniformly structured and distinguished into four parts: thoracic (T), sacral (S), cervical (C) and lumbar (L). It expands from the foramen magnum where it lies in continuity with the medulla oblongata to the plane of the first and second lumbar vertebrae. Its length is around 40 to 50 cm and diameter is about 1 to 1.5 cm. From its each side two consecutive nerve roots rows emerge which join to shape 31 spinal nerve pairs. The spinal nerves include sensory and motor nerve fibers. A dermatome is innervated by its each segment.  Medulla It appears as an inflamed tip of the spinal cord. It connects brain to the spinal cord. Nerve impulses reaching here steadily excite the diaphragm and the intercostal muscles helping in the breathing process, regulating heartbeat and the regulating the arterioles diameter thus regulating blood flow. The breathing process is controlled by neurons having mu (µ) receptors, to which opiates, such as heroin, bind. This explains for the oppressive outcome of opiates on breathing (Wilbarger, 2002). Damage to the medulla leads to instant death, as the connection between the brain and spinal cord lapses. Thalamus All sensory information (excluding olfaction) passes via paired structures, called thalamus, to the cerebral cortex’s somatic-sensory regions and similarly returns from there to them. Stimuli from the cerebellum go by them on their way to the cerebral cortex’s motor areas. Cerebral cortex It is a neural tissue sheet enclosing the cerebrum and cerebellum. It is distinguished into right and left hemispheres. It plays a vital role in attention, memory, consciousness, perceptual awareness, language and thought. It is mainly comprised of six horizontal layers, differentiating in composition from each other in terms of connectivity and neurons. It is around 2–4 mm in thickness. The cerebral cortex surface is folded, such that greater than 75% of it is obscured in the furrows, called "sulci". The neocortex is distinguished in six horizontal layers; the hippocampus part (archicortex), consists of three cellular layers, and is segregated into subfields. Neurons present in these layers join vertically forming small microcircuits (columns) (Brodal, 2010). Modulation and the Ayres 1979 theory Sensory modulation accounts for both behavioural responses and physiological reactions. Behaviourally, it is used to describe the individual’s ability to organize and regulate responses to sensations in an adaptive and graded manner, in congruence with the situational demands, or can be referred as the CNS’s ruling of its own action (Ayres, 1972). Physiologically, it is associated with cellular process of sensitization and habituation that changes the function and structure of neurons, thus impacting synaptic transmission. Sensory integration refers to neurological processes that systematize sensation arising from an environment and the individual’s body and enables the utilization of body efficiently within the environment (Ayres, 1972). It is a theory of relationship between brain and behaviour. This theory consists of three components. The first relates to development and depicts distinctive sensory integrative performance; the second explains sensory integrative dysfunction, while the third leads intervention programs. The three main postulates of this theory are: 1. Learning depends on the capacity to intake and process environmental and movement sensation utilize it for planning and organizing behaviour. 2. People with decreased capacity to process sensation may experience difficulty while generating appropriate actions resulting in an interference with behaviour and learning. 3. As a piece of significant activity, enhanced sensation may result in the progression of an adaptive communication thus improves the processing capability to sensation. Thus it may ultimately enhance bahavioural responses and learning process. CNS Function, Tactile input and Sensory Processing The sensory receptors of each constituent of the nervous system are different from each other; however, the mechanism of altering the sensory information from physical to electrochemical has few similarities (Dunn, 1999). All receptors possess an “electrical potential” set up by the charged ion distribution on the inner and outer sides of the cell membrane. In case of a weak stimulus, the concentration of electrical charges is very minimal and thus the receptors potential is also insufficient to be transmitted further than this level and thus the input cannot reach the CNS for further processing. However, if the sensory signal is sufficiently intense or provided for a prolonged period, then the receptor potentials can be combined together resulting in the generation of a potential to act within the sensory neuron. An action potential produced by any sensory stimulus is similar to that of other (Homer et al., 2002). Tactile sensations originate from receptors resided in the skin that ignite when something touches or us or is touched by us. They give the brain the boundaries of our body to allow us in differentiating self from others. They are progressed in two distinct and separate touch systems to help us in differentiating pressure touch from light touch. So a hypersensitive individual may exhibit intolerance for even light touch while the hyposensitive may show immense tolerance towards even pressured touch. Mechanoreceptors density and the size of receptor field may help us determine tactile discrimination. In fine discrimination regions, receptor concentration is high while a small receptor field. High receptor density regions are found to be more skilled. The tactile system also utilizes lateral inhibition to refine discrimination and focus input. Receptors linked with the Dorsal Column Medial Lemniscal Pathway (DCML) reply to motorized stimuli, relaying vibratory, proprioceptive (deep pressure), touch pressure information, and primarily tactile. Inputs are translated into potential actions set and conveyed through the axon to the cell body, dorsal root ganglion. Tactile sensation relates to understanding or insight of the position, or change in location, of an external sensory stimulus pertained to the skin. Besides within the parietal lobe, tactile aspects and coverage of proprioceptive input and following projection to brain’s anteriormotor planning. Thus, from the DCML, output is expected to impact motor planning and objects manipulation (Homer et al., 2002). The decline in sensory response towards the motor cortex occurring subsequent to disturbance of DCML is serious and hampers with the creation of acts by coordinated fine motor. The discrepancy in identifying an object’s form and size during the mechanism of active exploitation leads to problems in object handling. Thus the DCML may be accounted to have a part in modulating arousal. The Anterolateral System (AL) consists of segregate pathways that work primarily to arbitrate crude touch, pain, and temperature. Mediation of tickle sensation and neutral are also pertained to spread inside these anterolateral pathways. The sensory integration theory suggested the tactile system to be of extreme significance in formulating behaviour. Thus the somatosensory system is an exceptionally pervasive system from an interactive and a receptor perspective. Hence, the AL pathways venture to the brain areas accountable for autonomic regulation (hypothalamus), stimulation (reticular system) and emotional attitude (limbic structures).thus it can be postulated that tactile defensiveness may be associated to the linkages between these systems and the areas of brain (Bundy, Lane & Murray, 2002). Praxis It is an exceptionally human skill enabling us to efficiently interact with the material world. It is the foundation for interacting in an adjusting manner with this physical world. It is not an austerely neuromotor functions however it utilizes neuromotor system to execute the practice acts (Ayres, 1964). Praxis means action, doing and practice. Motor planning depends upon effective sensory integration. It entails conscious consideration to the chore while depending on piled up information regarding unconscious sensations (Ayers, 1972). Praxis involves three elements that cooperate and assist in the accomplishment of overall goal. These are: 1. Ideation: means determining or realizing a notion of what needs to be done. This involves recalling prior data regarding similar occurrence to comprehend the current sensory experience. 2. Planning: It involves utilization of the stored data to plan a route of action to interrelate with the environment. 3. Execution: It involves physical performance of the cognitive plan so that the actual interaction between the individual and environment may result. It is aided by the vestibular and tactile systems as they provide awareness about the way body moves and the way it can be used to operate with the environment (Ayers, 1964). Poor Motor Planning (Dyspraxia) It is an immaturity or impairment in the movement synchronization and therefore practicability: a capability to perform non-habitual contact with the environment (Bundy, Lane & Murray, 2002). Tactile processing, Somatodyspraxia, Bilateral Integration and Sequencing Dysfuntion Somatodyspraxia, is characterized mainly by reduced motor planning and tactile discrimination problems. It is regarded as a definite trouble in the praxis’s motor planning component and is apparent in intricacies in executing actions like imitating gestures and doing diverse motor tasks (Homer et al., 2002). Sequencing dysfunction and bilateral integrations are characterized by principal shortages in visual, proprioceptive and vestibular integration. These shortfalls result in difficulties with motor Tactile Dysfunctioning and Autism The autistic behaviour exhibit by children with ASDs is an outcome of reduced tactile discrimination resulting in the inability to store information regarding the way things feel (Bundy, Lane & Murray, 2002). This may lead to discrepancies in the utilization of tactile sense for complex purposes such as learning at school, inability to identify the sensation of touch without viewing, frightened of darkness, inability to dress up such as untied shoes and twisted waistbands, scattering of food during eating process and may result in an inappropriate hand writing due to the inability of utilizing tools like pencil, cutlery, paintbrush etc and an avoidance to initiate tactile experiences like picking up toys or tools. Conclusion Research in the field of Neurosciences has exhibited that when humans and animals are permitted to interact and discover the environments regarded as meaningful and interesting by them, an increased synapses formation results. This leads to the generation of a sensory response utilizing the CNS. However, children with ASDs are unable to do so. The major factor explored was the tactile dysfunctioning that leads to the discrepancies in sensory integration and dysparaxia, resulting in an unusual behavioural response exhibited by such children. Although the detailed study of tactile processing may help in the application of therapies to individuals with ASDs, which may help in acquiring the desired responses for a given stimulus. References American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders. 4th ed. Text rev. Washington (DC). Ayres, A.J. (1972). Sensory integration and learning disorders. Los Angeles: Western Psychological Services. Ayres, A. J. (1963). The Eleanor Clarke Slagle Lecture: The development of perceptual-motor abilities: A theoretical basis for treatment of dysfunction. American Journal of Occupational Therapy 17, pp.221–225. Ayres, A. J. (1964). Tactile functions: Their relation to hyperactive and perceptual motor behavior. American Journal of Occupational Therapy 18, pp.6–11. Ayres, A. J. (1979). Sensory integration and the child. Los Angeles: Western Psychological Services. Baranek, G.T. (2002). Efficacy of sensory and motor interventions for children with autism. Journal of Autism and Developmental Disorders 32, pp.397-422. Brodal, P. (2010). The Central Nervous System. Oxford University Press. Bundy, A. C., Lane, S., & Murray, E. A. (2002). Sensory integration: Theory and practice. 2nd ed. Philadelphia: F. A. Davis. Dawson, G., & Watling, R. (2000). Interventions to facilitate auditory, visual, and motor integration in autism: A review of the evidence. Journal of Autism and Developmental Disorders 30, pp.415-421. Dunn, W. (1999). Sensory Profile. San Antonio, TX: Psychological Corporation. Grandin, T. (1995). Thinking in pictures. New York, NY: Vintage Press Random House. Herbert, M.R. (2005). Large brains in autism: The challenge of pervasive abnormality. Neuroscientist 11, pp.417-440. Homer, R., Car, E., Strain, P., Todd, A., & Reed, H. (2002). Problem behavior interventions for young children. Journal of Autism and Developmental Disorders 32. Just, M. A., Cherkassky, V.L., Keller, T.A., & Minshew, N.J.( 2004). Cortical activation sand synchronization during sentence comprehension in high-functioning autism: Evidence of underconnectivity. Brain 127(8), pp.1811-1821. Kanner, L. (1943) Autistic Disturbances of Affective Contact. Nervous Child 2, pp.217-250. Prior, M., & Hoffman, W. (1990). Brief report: Neuropsychological testing of autistic children through an exploration with frontal lobe tests. Journal of Autism and Developmental Disorders 20(4), pp.581-590. Rogers, S. J., Hepburn, S., and Wehner, E. (2003). Parent reports of sensory symptoms in toddlers with autism and those with other developmental disorders. J. Autism Dev. Disord. 33, pp.631–642. Smith, C., Goddard, S., & Fluck, M. (2004). A scheme to promote social attention and functional language in young children with communication difficulties and autistic spectrum disorder. Educational Psychology in Practice 20, pp.319-333. Tomcheck, S.D, and Dunn, W. (2007). Sensory Processing in children with and without Autism: a comparative Study using the short sensory profile. American journal of occupational therapy 61 (2), pp.190 – 200. Wilbarger, J. L., & Wilbarger, P. L. (2002). Wilbarger approach to treating sensory defensiveness and clinical application of the sensory diet. Sections in alternative and complementary programs for intervention chapter 14. A. C. Bundy, E. A. Murray, & S. J. Lane (eds.), Sensory integration: Theory and practice (2), pp.335–338. Wing, L. (1997). The autism spectrum. Lancet 350, pp.1761-1766. Read More