Does sensory gating vary according to the neurological threshold axis of Dunn's four quadrant model in typical adults?

Objective: This study examined differences in sensory gating along the neurological threshold axis of Dunn’s four quadrant model of sensory processing. Method: Electroencephalographic measures were used to examine sensory gating ability in 65 typically developing adults ages 18-55. Event related potentials were recorded in response to repeated pairs of stimuli to the median nerve on the participants’ non-dominant wrists. Sensory gating was quantified as the ratio of the amplitude of the first-stimulus P50 to the amplitude of the second-stimulus P50. The Adolescent/Adult Sensory Profile was administered to determine the participants’ sensory processing pattern and their neurological threshold score. Results: Results were not significant in terms of identifying a relationship between sensory processing patterns along the neurological threshold with gating ability. However, results did show trends in support of the direction of the hypotheses. Conclusion: This study provides preliminary evidence to support the claim that a relationship exists between sensory gating and sensory processing patterns. However, additional research is warranted. SENSORY GATING AND NEUROLOGICAL THRESHOLD 3 Does Sensory Gating Vary According to the Neurological Threshold Axis of Dunn’s Four Quadrant Model in Typical Adults? Sensory Processing Disorder Sensory modulation, according to Miller and Lane (2000), is the process in which neural signals about the intensity, frequency, duration, complexity and novelty of sensory stimuli are interpreted and adjusted by the central nervous system to enable adaptive behavior. It is proposed that sensory processing disorder (SPD) reflects difficulty organizing the neural signals to sufficiently engage in appropriate responses and behaviors (Miller, Anzalone, Lane, Cermak, & Osten, 2007). A. Jean Ayres (1963) was the first to examine this idea. Her research involved, “the association between sensory processing and behavior in children with learning, developmental, emotional, and other disabilities” (Miller et al. 2007, p. 135). Ayres proposed that sensory processing deficits lead to functional problems (Miller et al., 2007). These functional problems can include reacting adversely or failing to respond to sensations in daily life. As a result, children with sensory processing disorder are hindered from full participation in daily occupations that provide them with a means to learn life skills, develop social relationships, and meet biological needs (Chang, Parham, Blanche, Schell, Chou, Dawson, & Clark, 2012). Consequently, children that lack the opportunity to participate in these situations may present clinically with developmental delay and maladaptive behaviors. Due to the consequences manifested from sensory processing difficulties, many researchers have worked to show the underlying neurology. It has been suggested that one of the underlying neurological problems in SPD may be impaired sensory gating (Davies & Gavin, 2007). Sensory gating is a minimization of the neurological response to repeated or extraneous sensory stimuli (Davies, Chang, & Gavin, 2008). SENSORY GATING AND NEUROLOGICAL THRESHOLD 4 Dunn’s Four Quadrant Model Winnie Dunn (1997) has put forth a model of sensory processing. In this model, Dunn describes a horizontal axis depicting behavioral regulation strategies and a vertical axis of neurological threshold intrinsic to the individual. The horizontal axis is a continuum ranging from passive to active regulation strategies. When a person is said to have a passive selfregulation strategy he/she allows the events of the environment to occur around them; where an individual with an active self-regulation strategy seeks to control the amount of stimulation he/she receives (Dunn, 2007). The vertical axis is a continuum ranging from low to high neurological thresholds. The neurological threshold is described as the intensity of a stimulus sufficient to generate a response. When an individual has a low neurological threshold he/she will be much more responsive to stimuli and when a person has a high neurological threshold he/she will not notice things as easily as others because of requiring much greater intensity. “ When these 2 continua intersect, 4 basic patterns of sensory processing emerge” (Dunn, 2007, p. 85). These include: sensation seeking, sensation avoiding, sensory sensitivity, and low registration. A person with a sensation seeking sensory processing pattern has a high neurological threshold and an active self-regulation strategy. He/she would actively seek out stimulation intense enough to obtain his/her threshold. An individual with a sensation avoiding sensory processing pattern has a low neurological threshold and an active self-regulation strategy. He/she would tend to limit sensory input to him/herself because too much input becomes overwhelming. A person with a sensory sensitivity sensory processing pattern has a low neurological threshold and a passive self-regulation strategy. He/she would be uncomfortable in a high intensity situation but may not withdrawal from it like those with a sensation avoiding processing pattern. A person with a low registration sensory processing SENSORY GATING AND NEUROLOGICAL THRESHOLD 5 pattern has a high neurological threshold and a passive self-regulation strategy. He/she would tend not to seek out stimulation and tend to miss things due to a high threshold for stimulation (Dunn, 2007). Sensory processing patterns rise to the level of sensory processing disorder when the associated behaviors interfere with daily life. According to the Sensory Profile, two standard deviations from the mean in any quadrant illustrate sensory processing disorder. Existing research suggests differences in neurological processes along the range of neurological thresholds. Jagiellowicz, Xu, Aron, Aron, Cao, Feng, and Weng (2010) measured neuroticism and introversion with the Highly Sensitive Person scale. Those with high sensitivity (introverts) reported noticing many subtleties in the environment. Sensory processing sensitivity was shown to make more of a contribution to differences in brain response, as measured by functional Magnetic Resonance Imaging than personality variables (Jagiellowicz et al., 2010). Aron and Aron (1997) proposed that sensory processing sensitivity is evident in behaviors. Their study found that sensitivity correlated with emotionality and introversion, where individuals with high sensitivity are most likely to be introverted (Aron & Aron, 1997). Ben-Sasson, Carter, and Briggs-Gowan (2010) examined the relationship between sensory over-responsivity (SOR, representing both sensory sensitivity and sensory avoiding) and behavior/temperament in children. They found, “the child’s actions to deal with overwhelming sensations have developmental consequences directly through their avoidance or indirectly through caregiver’s preventative adaptations to the child’s SOR” (Ben-Sasson et al., 2010, p. 1199). For example, tactile and auditory stimuli accompany many academic and social activities. If a child has SOR towards these sensory stimuli, then it may impact his/her participation in these occupations. This lack of participation may result in developmental delays with deficits in adaptive responses to new environments or challenges (Ben-Sasson, Carter, & Briggs-Gowan, 2009). Reynolds and SENSORY GATING AND NEUROLOGICAL THRESHOLD 6 Lane (2008) conducted a review of the literature regarding sensory over-responsivity as a frequent co-occurring diagnosis with ADHD, Fragile X syndrome, and autism. From a combination of the findings in the reviewed literature and three pediatric case studies they conducted, these researchers suggest that there is sufficient evidence for sensory overresponsivity as a stand-alone diagnosis (Reynolds & Lane, 2008).