SPD and what it is
Sensory Processing Disorder is a disorder in which sensory information received from the outside world or one’s own body is poorly interpreted and is not organized into appropriate responses. Children with this disorder have lives that are so affected by their sensory issues that it adversely affects their ADLs (Activities of daily living) to the point where they have trouble operating under normal conditions. SPD can affect only one sense or it can affect nearly all of them, and can affect them either in a hypersensitive or hyposensitive way. One child may be overly sensitive to loud sounds and another may not be affected by their sense of touch (tactile), or vice versa.
Children with SPD often have trouble with motor and other skills that are needed for a school environment and so usually suffer from emotional issues and low self-esteem. These troubles can create more social, educational, and emotional problems such as inability to make friends, failing school, and being defined as uncooperative, awkward, and unruly.
Sensory Modulation Disorder
Sensory Modulation Disorder (SMD) is a specific subtype of SPD and is defined by issues with the brain regulating the sensory information gained from the environment in an effective manner and still remaining at the appropriate alertness level. In normal sensory modulation, the CNS (central nervous system) is able to regulate attention, attend to important and necessary stimuli, and filter out stimuli that are unimportant. When sensory modulation is working correctly, it works automatically and with no effort on the part of the child. When a child has SMD it is difficult and ineffective and requires effort with no assurance of correctness. The brain normally pays attention to the sensory stimuli it needs to pay attention to and ignores the unimportant, background stimuli. With Sensory Modulation Disorder, the child has a hard time ignoring the unimportant stimuli and simultaneously paying attention to the important ones. Thus they can shift from being hypersensitive to certain things and then hyposensitive to others. They fail to attach meaning to an activity or sensation because they cannot modulate the sensory input they are receiving because there is poor registry of such sensations.
Sensory Discrimination Disorder
Sensory Discrimination Disorder (SDD) is another specific subtype of SPD and is defined by difficulties in interpreting sensory stimuli that is coming from one or more of the 8 senses: tactile, visual, olfactory, auditory, gustatory, proprioceptive, vestibular, and interoceptive. This means that when a child receives stimuli from one of these senses, they cannot necessarily differentiate it from another stimulus of the same sense. Thus they receive confusing signals from their brain telling them one thing but in reality they’re experiencing something else entirely. For example a child with auditory discrimination problems will have difficulty distinguishing a request by a teacher from background noise the child hears. A child with a vestibular issue would not be able to tell which way they were spinning or moving in relation to the space around them.