Interoception: The Hidden Sensory System

Introduction and Overview

Thank you for your participation today. I'm excited to be presenting on the topic of the interoceptive system. As we start talking about sensory processing, interoception, and the whole sensory-motor system, it's important to understand that children are little sensory beings and there's a wide range of what can be considered as "normal". As we dig in and start to understand the interoceptive system, we will gain some insight into children who might have something hiding in the background that is getting in the way of doing the things they want to do. That's what we're interested in: enabling people to participate in activities that are meaningful and purposeful. That is occupational therapy in a nutshell. Hopefully, as a result of today's course, you will all be able to connect your existing OT knowledge to this new sensory system called the interoceptive system.

Ayre's Sensory Integration Theory

We can never start a conversation about sensory integration and sensory processing without tipping our hat to Jean Ayres' Sensory Integrative Theory and foundational research. I recognize that many of you are familiar with this theory, but we will review it to make sure we are all on the same page.

One of the postulates of Ayres' Sensory Integrative Theory is that "adequate sensory processing and integration of sensory information is an important foundation for adaptive behavior." Notice that the postulate doesn't use the terms "appropriate" behavior or "correct" behavior. We want to have the tools to adapt to what comes our way. We need to feel like we have the capability, the competence and empowerment to deal with situations so that we can adequately process and pull multiple sensory inputs together in order to respond to our environment with behavior that's adaptive.

With sensory integrative dysfunction, the brain does not process or organize the flow of sensory impulses in a way that gives the individual precise information about him/herself and the world. Maybe there's a difference in the way that we understand where our body is in space or tactile input and tactile processing. That the way the brain is processing that information is just not as adaptive or precise as we might find in a more mature system. Somatosensory refers to the body and the senses together. The term somatosensory can be used synonymously with sensory motor or sensorimotor.

The Five Senses + Three

In addition to the traditional five senses that most of us are familiar with and taught at a young age (sight, sound, smell, touch, and taste), there are three more sensory systems that we should also be aware of: the proprioceptive system, the vestibular system, and the interoceptive system. Let's begin by defining these additional three systems.

The proprioceptive system. The proprioceptive system gives us information about where we are, and the position of our body in space. The receptors for the proprioceptive system are in the joints and muscles. Of course, if I shine a light in my ear I can't see it because I don't have a receptor there. In order for the proprioceptive system to fire or to be aware or to respond, we have to stimulate the receptors in the joints and muscles.

The vestibular system. The vestibular system relates to the inner ear. The only way to stimulate the vestibular system is to move the head. That system helps us know where our head is in space in relation to our body and our spatial orientation. It's a gravitational sensor that tells us where we are in relation to the Earth.

The interoceptive system. Interoceptive receptors are on the internal organs. In my opinion, it doesn't make sense to talk about the senses unless we also talk about how the praxic system and the kinesthetic system play a role in movement orientation. We don't have a receptor for those systems because those are outputs. We have appropriate praxis if we have appropriate input into the sensory systems.

When the senses come together to create an adaptive response, that is sensory integration. We integrate the senses, resulting in the end product of performance and social engagement. The end product is being able to do the things we want to do. We need to be able to take in sensation from our environment and pull it together in a way that supports our function. For example, the vestibular, proprioceptive, and tactile senses all contribute to body awareness. Body awareness is necessary for concentration, organization, and self-esteem, among others. When we integrate those senses, the end product is performance skills (sensory-perceptual, emotional, cognitive, and communication/social).

When we talk about performance and social engagement, the interoceptive system contributes to the end product of resilience and adaptive coping. That's why we're increasingly interested in this system of interoception. In children that have struggled to meet some of the performance goals that we would like to see them meet, we need to look at whether they have interoception deficits and what we can do to help them.

I always like to give a nod to Jane Case-Smith who is a mentor of mine and a beloved occupational therapist. She asserts that the drive to engage in occupation as the mechanism through which children develop skills and competencies. Children have an innate drive to engage in all kinds of crazy occupations. The theory of sensory integration is that children want to figure out how to be in the world in lots of different ways. Our job and our goal is to enable that.

Core Elements of Sensory Integration Intervention Process (Fidelity Measures)

One of the things that happened in the last 10 years which helped to advance our science in the area of sensory integration and processing started with some well-established and highly-regarded occupational therapists coming together to create the fidelity measures (Parham et al., 2007). As they relate to evidence-based research, these measures were developed to serve as a tool so that researchers could properly document and demonstrate that delivery of an intervention adheres to the underlying therapeutic principles on which it is based. As stated in an article from the American Journal of Occupational Therapy, "Outcomes research that uses a carefully thought out fidelity instrument allows practitioners to appraise the relevance of a study’s intervention procedures to their own practice challenges." Furthermore, the article goes on to state that "fidelity measurement has increasing significance for evaluation, treatment effectiveness research, and service administration" (Parham et al., 2011). 

In order to know whether or not the intervention that someone provides can be considered sensory integration versus simply a therapeutic intervention, we follow the following fidelity measures:

• The therapist's behavior and attitude are two of the components of the intervention in order for it to be sensory integration.
• Sensory integration provides the just-right challenge. If the therapist or individual is giving a child something to do and it's too easy or too hard, the activities have not been selected in order to give the child the just-right challenge. It fails to meet this area of fidelity.
• With sensory integration, children have to be able to collaborate on the activity choice.
• Children have to guide self-organization, so they are active co-participants in the activity.
• A sensory integration intervention must support optimal arousal. If someone is providing an intervention and the child gets overwhelmed or underwhelmed and they're not aroused appropriately and optimally with an output outcome, then it's something different than sensory integration.
• Sensory integration creates a play context.
• Sensory integration maximizes the child's success.
• Sensory integration ensures their physical safety.
• The room is arranged to engage the child. Set things up so that as the child selects the activities they want to work on, it will be on behalf of their growth in the sensorimotor system. 
• Sensory integration fosters a therapeutic alliance.

Why Sensation is Important for Learning

Why is sensation important for learning? The brain learns best when it's aroused to attend to the learning opportunity. Sometimes we forget that piece. I teach at a college from 3:00 to 6:00 on Mondays and by that time of day, the students are brain-dead. They're like a bunch of zombies sitting in front of me and I have to be somewhat entertaining for them. The whole point of sensory integration as a therapeutic intervention is to get the body and brain ready for good learning and the next just-right challenge. If an internal sensation is demanding a priority (e.g., hunger, the need to go to the bathroom), it's difficult to shift away from that internal sensation in order to pay attention to the learning opportunity in your environment. We are wired to take care of our internal needs. If an external demand being placed upon us is competing with an internal demand, most likely the internal demand is going to win out for our attention. In other words, we're not available for the learning opportunity, whether it's social or academic. Whatever it is, we have diverted attention which keeps us from being able to move forward and achieve the end product.

Postulates of Sensory Integration: Theoretical Base

These postulates are from the fidelity measure article that I referenced earlier. For the sake of time, I won't go into great detail on these, but I wanted to briefly review them so that we all have a foundation for the next section. 

1. An optimal state of arousal is a prerequisite for adaptive responses to occur. 
2. It's difficult to learn or respond appropriately when you're exhausted or hungry, for example
3. Sensory integration occurs during adaptive responses. 
4. Every time that we respond adaptively, we have this integration happening in the nervous system.
5. Multiple sensory systems may be needed to facilitate an optimal state of arousal.
6. Adaptive responses must be directed toward the child’s current developmental level. Remember that sensory integration is a developmental theory. We always have to think about what is developmentally appropriate to expect of this individual before we put in that next just right challenge. At that point, the just right challenge will produce development.
7. Activities that reflect the “just right challenge” produce growth and development.
8. Problems with sensory modulation or in foundational abilities contribute to deficits in end product abilities. They get in the way of being able to do what we want to do.
9. The child needs to be self-directed, with therapist guidance, for sensory integration to occur. 
10. When they are self-directed, that's when we the best work occurs in the sensory nervous system.
11. Adaptive responses are elicited through activities that facilitate sensory modulation, discrimination, and integration resulting in improved postural control, praxis/bilateral integration, and participation. Adaptive responses come in when we get involved in activities that cause our sensory pathways to be working and developing. Then, the receptors fire, output occurs, and the individual is excited about what they've accomplished, resulting in a feedback loop.
12. Intervention is directed to underlying deficits in sensory modulation, discrimination, integration, and/or foundational abilities and not toward training in specific skills or behaviors. We direct intervention at that underlying sensory system so that the system grows and develops and the adaptive response can come, otherwise, we've taught splinter skills.
13. As the child achieves increasingly complex adaptive responses in therapy, changes will be evident in outcome abilities such as self-regulation, self-esteem, social participation, academic performance, and participation in daily life routines and activities. Those changes will extrapolate exponentially to other activities throughout their lifetime.

Atypical Sensory Processing

Where do we see atypical sensory processing? We commonly see it in children who are poor sleepers, poor eaters, children who are hard to soothe, and children who are unresponsive to others. We also may witness a child using a less than optimal strategy in order to feel more in control, to feel more regulated. For example, they might engage in hand flapping, rocking, head banging, screaming, or hitting. When we get overwhelmed, our sensory system is no longer modulated. That's typical. We just want to have an adaptive response as much as we can. When we see those kinds of behaviors or those outputs, then we can start thinking perhaps there is some sort of dysfunction in that sensory system.

Function-Dysfunction Continuum

Within the theory of sensory integration, I find it helpful to think about function and dysfunction on a continuum. Paula Kramer's work looks at areas of occupational performance by mapping them out using a function-dysfunction continuum. Function would be considered something that is developmentally appropriate and supports an adaptive response. Dysfunction would occur if we don't have an adaptive response. As you go through the following list, compare the function and dysfunction descriptions side-by-side. Sometimes these are obvious, but I have found a lot of benefit in mapping out the function-dysfunction continuum when writing goals, when performing my assessments, and when talking with others about the continuum and where we want to be on that continuum. 

Case: Winnie

Winnie is a 9-year-old girl with challenges in sensory processing and sensory integration that affect her participation in daily occupations and limit her social opportunities. An occupational therapy evaluation identified difficulties in the area of self-care, sensory processing, and social interactions. Winnie’s mother describes her as high strung and says that she can be snobbish. She has only one friend. Her mother states that Winnie grows extremely anxious when her routine is interrupted and she has difficulty recovering. She says she "can’t breathe" and her heart is so loud it hurts her ears. When overwhelmed, Winnie is diagnosed with encopresis and has occasional accidents, wetting her pants. Asthma has been ruled out. Mother and father are very concerned about Winnie’s behavior (avoidance, tantrums) and lack of interest in activities outside the house. She is overly avoidant of novel experiences. She has poor frustration tolerance and will become anxious to the point that she will cry or tantrum. As a child, she refused to nap, and even now, transitioning to sleep can result in tears and tantrums. 

Function-Dysfunction

Let's examine Winnie's case using a sensory processing lens to assess where she falls on the function-dysfunction continuum (Figure 1). First, we want to ask ourselves: Does she have an optimal state of arousal? No. Does she have adaptive responses to sensation? No, she's avoidant; she gets overwhelmed by sensation. Does Winnie have multi-sensory systems working together? No, there seems to be some dysfunction. Are Winnie's adaptive responses appropriate to her current developmental level? No, we would expect a nine-year-old to be a little bit more regulated and certainly not to be wetting/soiling her pants. Winnie is unable to tolerate frustration when given an age-appropriate task. She does not engage in adaptive sensory modulation to produce age-appropriate end products (e.g., playing with others, doing her homework, going to bed without tantrums). She is not self-directed. She avoids participating in sensory activities. Her development is not age-appropriate. There are some issues going on with Winnie where we would consider a delay, especially in bowel and bladder independence. She does not tolerate increasingly complex challenges.