Sensory Processing Disorder (SPD) is a neurological condition where the brain struggles to receive, organize, and respond to sensory information. This disorganized processing affects how a person perceives the world, impacting their daily life, learning, and behavior. Experts categorize SPD into three major patterns to understand the varied ways it presents.
The Three Foundational Patterns
The three primary patterns of SPD are Sensory Modulation Disorder (SMD), Sensory Discrimination Disorder (SDD), and Sensory-Based Motor Disorder (SBMD). Each describes a breakdown in the sensory-motor pathway, influencing interaction with the environment. SMD governs the intensity and nature of a person’s immediate reaction to sensory input, focusing on the nervous system’s ability to regulate incoming messages.
SDD governs the interpretation of sensory information after it is received. This involves difficulty distinguishing between subtle details, such as knowing if a sound was “cap” or “cat.” SBMD governs the motor output in response to sensory signals, resulting in difficulty using the body effectively and performing coordinated movements.
Sensory Modulation Disorder Subtypes
SMD involves three distinct subtypes describing how the nervous system regulates incoming sensory information. Sensory Over-Responsivity (SOR) involves reacting too intensely or for too long to tolerable stimuli. For example, a person with SOR might find a clothing tag irritating or perceive a normal sound as painfully loud.
Sensory Under-Responsivity (SUR) involves a delayed or muted response to sensory stimuli. These individuals may appear withdrawn or lethargic because they are not registering information like pain, extreme temperatures, or internal cues such as hunger. They may seem oblivious to their surroundings, even in loud or bright environments.
The third subtype is Sensory Seeking or Craving (SC), where the person actively seeks intense sensory input. This need often results in disorganized behavior, as the person constantly pursues more stimulation. A sensory seeker might crash into objects, spin excessively without getting dizzy, or need deep pressure input like tight hugs or heavy blankets.
Sensory Discrimination and Motor Disorders
Sensory Discrimination Disorder (SDD) involves the brain struggling to identify and interpret the subtle qualities of sensory input. This affects the ability to perceive fine differences and give meaning to sensations. For instance, a person with SDD may have difficulty telling the difference between a quarter and a dime by touch alone, or struggle to gauge the force needed to hold an object without breaking it.
Sensory-Based Motor Disorder (SBMD) is characterized by difficulties with balance, motor coordination, and planning movements. This pattern has two primary manifestations. Postural Disorder involves difficulty maintaining body position against gravity, leading to poor core stability and low endurance. Individuals might frequently lean on furniture for support or become easily fatigued during physical tasks.
The second manifestation is Dyspraxia, which refers to difficulty planning and executing novel motor tasks. This challenge affects the ability to conceptualize, plan, and sequence movements needed for skilled actions, such as learning a new sport or getting dressed. Both postural and dyspraxic challenges stem from disorganized processing of information from the vestibular (movement and balance) and proprioceptive (body awareness) sensory systems.