‘Sensory defensiveness’ is one issue individuals with brain injury often struggle with. This problem can manifest itself in many different forms.
It may present itself as increased negative reactivity to environmental sounds/noises. For example, someone may find himself to be very agitated by background noises from fans, clocks or even the hum of the refrigerator — things he may never have noticed before. Or a person may become overly startled and have trouble regaining his or her composure after hearing a loud car horn or siren.
These examples relate to an over-responsiveness of the nervous system to one kind of sensory input: auditory or sound input. This increased reactivity can occur in response to other forms of sensory input as well, including touch (e.g. from clothing tags on the skin), visual input (e.g. bright lights), movement (e.g. while in a car or on a bus) and even tastes and smells (e.g. from scented sprays or perfume).
On the surface, these symptoms may seem strange or be interpreted as weird behaviours. So, you may wonder how a person’s brain injury could lead to these new sensitivities and responses. What’s going on in the brain here?
Well, part of the answer is related to the Autonomic Nervous System (ANS). This is our ‘protective’ nervous system. When it is activated, a person’s body and brain become prepared for danger (i.e. heart rate increases, muscles are activated for movement, pupils dilate, etc.). When the ANS is activated, a person will often go into ‘fright, flight or fight’ mode.
After the danger has passed, a person’s Parasympathetic Nervous System (PNS) takes over, activating all the calming and restorative processes required to maintain health and equilibrium.
Both these systems are thus equally vital and important. However, when ‘sensory defensiveness’ develops, the regulation of these two systems goes awry. The ANS becomes triggered very easily, by not only signals warning of danger (e.g. a screaming child), but also by non-threatening sounds (or other inputs). When this happens, a person has ‘defensive’ reactions to sensations which may have never bothered him or her before. As well, the decreased regulation of the ANS/PNS leads to poor activation of the PNS when recovery processes should be occurring. This leaves a ‘sensory defensive’ person distressed and agitated long after the sensation has passed.
What can be done to help?
There are many different types of therapeutic approaches to address this issue.
For example, cognitive-based approaches rely on the use of our conscious thoughts to affect the lower-level processing in the nervous system. Of equal value however, are sensory-based strategies. We can use input to our basic senses to both raise and lower the activity of our nervous systems and to decrease the negative ‘reactivity’ to sensations experienced by a person with ‘sensory defensiveness’.
Certain sensations have a calming effect on the nervous system. One form of input to the tactile system can directly calm the nervous system: deep pressure touch (e.g. from massage, wrapping up in a blanket or wearing spandex clothing). As well, slow, rhythmic music – picked up by the auditory system – can also directly organize the nervous system, leading to a calmer state.
Another valuable sensory system is the proprioceptive system. It receives input when we do any heavy muscle work (e.g. push ups, using hand weights) or when our joints get compressed (e.g. during jumping, or while holding ourselves in a plank position or even a head or shoulder stand).
This ‘proprioceptive’ input has a very powerful organizing effect on the nervous system. Therefore, it can be used to bring someone to a state of calm (if their ANS is over-active) or to increase a person’s level of alertness and readiness for action (when their ANS is under-active, such as when a person is extra groggy and slow to move in the morning).
Our movement experiences send signals to the brain which can have an excitatory effect (e.g. fast movements with changes in speed/direction – such as felt when on a roller coaster) or a calming effect (e.g. slow gentle rocking – such as that used to rock a baby to sleep).
With our knowledge of how sensations affect the nervous system, we can use specific activities which provide calming and organizing sensory input, to help a person with sensory defensiveness. For example, a person with TBI may have become over-responsive to noises and bright lights. This could make a routine doctor’s visit become a very agitating and draining experience. The person may get bothered and feel unable to tolerate all the background noises in the waiting room (e.g. from cell phones, conversations, medical equipment, background traffic, etc.) or the fluorescent lighting or glare from the windows.
In this case, use of sensory-based activities 1 to 2 hours before the visit can actually help. Before leaving, the person could potentially apply deep pressure to his arms and legs by applying lotion with heavy strokes or by taking a long shower while using a loofah/scrubber. He could also have a family member apply ‘joint compressions’ to his body or take a rest under a weighted blanket. If able, he could do heavy muscle work by performing wall or table push-ups or even walk around with weighted ankle bands in the morning.
On the ride to the doctor’s office, the use of car window screens could help decrease the glare. And, listening to calming slow rhythmic music or a nature sounds CD may also help to calm his nervous system. These activities could be used to prepare his nervous system to be calm and balanced and this would in turn directly decrease his over-reactivity to sounds and bright lights that would otherwise bother him.
Each individual has very different needs and responses to sensations. The above activities may not be calming or organizing for everyone. And the properties of all sensory systems and input must be considered. For that reason, it is essential that an occupational therapist trained in Sensory Integration be consulted for an assessment when developing one’s own ‘sensory diet’ of activities for the above-mentioned purpose.
However, with the help of a trained occupational therapist, a person with ‘sensory defensive’ symptoms can develop a personalized ‘sensory diet’ to meet their nervous system’s needs. This can make a person’s return to regular daily activities so much less of a struggle and even more enjoyable!
photo credit: SALUT ! via photopin cc