Tactile disorders, or sensory processing disorders, affect the sense of touch. In these disturbances, sensation may be felt too intensely or too subtly, or objects may in various ways seem unrecognizable when held in the hand. Tactile disorders are rooted in the brain and central nervous system and may result from neural disregulation or from brain tumors, injury or surgery. Understanding the various tactile disorders sheds light on what is a very challenging issue to those who suffer them.
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Perhaps the most common of the tactile disorders, those with tactile defensiveness have markedly diminished tolerance for any tactile sensations. Although it is experienced by some adults, it generally manifests in children. The Children’s Academy for Neurodevelopment and Learning explains that incoming stimuli is not adequately processed and screened in the brain, causing the child to register even mild sensory input as extreme, irritating or even painful.
Tactile hyposensitivity is the opposite of tactile defensiveness. Those with this tactile disorder have a diminished tactile stimulation. This can result in injury, because pain threshold is often quite high. Those with tactile hyposensitivity may gravitate toward experiences of high sensation in order to feel. They may love extremes in tastes such as very salty or spicy, may like surfaces that provide lots of texture and stimulation, and may seek out messy, boisterous activities.
Tactile apraxia is a tactile disorder of object exploration. It involves a disturbance of hand movement when manipulating an object in the presence of movements without use of an object (e.g., repetitive movements or gestures). Those with tactile apraxia have difficulty attuning hand movements to the characteristics of an object under certain circumstances.
A person with tactile agnosia cannot recognize objects by touch. According to the Mayo Clinic Department of Neurology, tactile agnosia is a subtle and nondisabling disorder. This tactile disorder results from lesions, tumors or damage to the mesial temporal, relrosplenial and/or mesial occipital cortices of the brain. Those with tactile agnosia usually have no difficulty in identifying objects through their other senses.
Tactile aphasia shares some similarities with tactile agnosia. Someone with tactile aphasia cannot name an object when perceived by touch. It may be unilateral or bilateral (i.e., it may affect one hand or both hands). Someone with tactile aphasia often can describe the function of an object, though perhaps not clearly. He is able to name the object when perceived by other senses, such as sight.