The following article was inspired by the book, The Brain’s Sense of Movement by Alain Berthoz and the concepts taught by the Postural Restoration Institute (PRI). The purpose of this narrative is to explore the multisensory nature of PRI.
Traditionally, we presume that the goal of our PRI interventions is to create postural changes and thus function via first repositioning to achieve positional and neuromuscular neutrality by decreasing the dominant L AIC/R BC/R TMCC lateralized pattern, followed by retraining the body to be able to fully appreciate the submissive R AIC/L BC/L TMCC pattern, and finally restoring authentic reciprocal alternation between the two. This ultimately means the ability to walk and breathe utilizing all 3 planes of motion as well as have the movement variability capacity to experience other potential functional strategies of these synergistic patterns such as sports performance activities or simply carrying an object while walking.
Within this paradigm, we tend to think about inhibiting specific chains of muscle (members of the L AIC/R BC/R TMCC) while facilitating the opposing R AIC/L BC/L TMCC neuromuscular synergistic pattern. More details of these chains and their composition can be found at https://www.posturalrestoration.com/the-science. Depending on an individual’s specific patterns and where they are in their restorative process, some of these chains and plane of function (meaning sagittal, frontal, and transverse) may need to be emphasized more than others. However, the bottom line is that PRI practitioners are mainly considering within their treatment rationales which chain(s) of these synergistic patterns of neuromuscular function need to be inhibited/facilitated and the corresponding plane of emphasis. Again, this is all for the goal of efficient and effective movement.
In my recent previous article (http://www.posturalrestoration.com/community/post/2633/biasing-bilateralism-with-unilateral-sensory-and-manual-integration-by-heather-carr?id=2633), I discussed the interrelated somatosensory nature of neuromuscular function. This means that the brain is programmed not only to simply facilitate or inhibit various agonistic and antagonistic chains of muscle but that this mechanism is accompanied by the ability to also sense and feel these contractions, accompanying body segment positions, and movement relative to each other. To be more specific, our somatosensors (such as tactile, proprioceptive, and kinesthetic receptors) are feeding the brain information regarding position, velocity, and acceleration. In PRI, we refer to these as reference centers. PRI teaches 6 key ones (as described in the Impingement and Instability course) that when one has the ability to sense they most likely can also simultaneously engage the corresponding desired neuromuscular chains and hence movement patterns for better function and performance. The brain does not aim to separate motor from tactile, proprioceptive, and kinesthetic processing but needs all of this information for proper motion. In cases where there is impairment here, such as with a stroke or peripheral neuropathy, movement capability can become significantly dysfunctional.
Let’s take this a step further. When processing somatosensory signaling, the brain concurrently needs other sensory signals that are crucial for desired movement goals. This includes vestibular, visual, and auditory reception and thus perception. The vestibular receptors provide critical information to the brain such as where the head is oriented with respect to gravity, its velocity and acceleration, as well as the plane of its motion. In fact, the semicircular canals are organized in 3 perpendicular planes with one another which enables the differentiation between sagittal, transverse, and frontal vectors of head movement. This triplanar architecture is reflected in the subcortical areas where the 3 dimensional directional information is retained and further integrated with visual, auditory, and somatosensory signals. Furthermore, muscles are represented in the brain by their “eigenvectors”, their own virtual vectors that convey the amplitude of force exerted by each muscle and its corresponding plane of action. There seems to exist patterns of redundancy with the orientation of the planes of the semicircular canals to how the brain processes 3 dimensional movement and position to enable more consistent sensory processing. For example, the three pairs of extraocular muscles are approximately parallel to the planes of the semicircular canals likely making it easier for the brain to reconcile triplanar multisensory information.
What is important to understand is that without the merging of ALL the sensory information, the brain will not be able to completely know its position and movement with respect to itself, the ground, and other objects. For example, without synchronized signals from both the visual the vestibular systems, the brain wouldn’t be able to tell whether the body and/or the environment is moving. Without appropriate integrated tactile, proprioceptive, and kinesthetic signaling, the brain has no idea where its body segments are positioned relative to the head and the ground. Without proper visual processing, the body loses information regarding orientation of the position of self with relation to the environment coupled with reduced direction, speed, and acceleration of movement signaling. Furthermore, the auditory system also provides information regarding environmental space as patterns of sound are detected and contribute to an individual’s orientation relative to their surroundings. In sum, postural positioning and movement with respect to the self, ground, and other objects is dependent on all of these sensory signals.
Not only do we need authentic sensory signaling from the vestibular, visual, auditory, and sensorimotor systems but this information must be perceived by the brain in a coherent manner. Thus the term, “neurosensory coherence,” describes this phenomenon. There are certain parts of the brain such as the superior colliculus, cerebellum, and lateral geniculate nucleus of the thalamus that are especially important for merging these signals together and communicating with around 20 other brain structures. In fact, these sensory pathways are so intertwined that some neurons can respond to different types of sensory receptor signals. For example, 2nd order vestibular neurons fire from both oculomotor and neck efferent signals as well as incoming afferent vestibular, visual, and proprioceptive signals. Some bimodal neurons can be fired with either visual or tactile input and thus can create the same perception. The visual stimulus of a finger moving to touch one’s face can be perceived as actually touching the face without real contact due to the overlapping tactile and visual receptor field function. Some cases of hemi neglect have shown that injection of cold water into the ear and thus stimulating the vestibular system can temporarily alleviate symptoms of neglect including hemianopsia (seeing only ½ of a visual field) and/or hemianethesia (reduced sensation on ½ of the body). Likewise, somatosensory stimuli (example of transcutaneous electrical-stimulation) as well as visual stimuli (such as prism glasses) can also reduce symptoms of neglect. What this means is that a somatosensory stimulus can simultaneously be perceived as a somatosensory, vestibular, or visual stimulus and vice versa. The somatosensory primary cortex seems to have no preference for the various sensory inputs. There are a variety of neurosensory patterns in the brain that can all contribute to neurosensory perception and body schema. Therefore, movement ultimately creates and requires a symphony of somatosensory, visual, vestibular, and auditory sensory signaling that must be properly synchronized, merged, and modulated together with other cortical and subcortical discharge. When this neurosensory coherence occurs, desired and efficient movement is permitted. Therefore, in cases where this is not occurring the clinical dilemma involves figuring out which sensory system(s) to manipulate to achieve the desired functional outcome.
Within the paradigm of PRI, we assume an inherent asymmetry and lateralization of the postural system. However, based on the information presented in this article, I hope you are now also assuming this includes an asymmetrical and lateralized sensory system. Once again, the brain merges all of this information together for processing posture and movement modulation. The brain is actually constantly checking to see if how it predicted position and motion was indeed perceived as accurate. Furthermore, this information is not just being used to only put us in certain positions and permit movement but also is concurrently telling us where we are located in space relative to the ground and peripheral environment. Movement is orientation and orientation is movement. For example, the brain regulates the firing threshold of a motor neuron. This threshold (meaning how easy or difficult it is to fire) is influenced by the position of the body part and thus also has a spatial dimension within it. Considering both the agonist and antagonist facilitation or inhibition tendencies (think PRI patterns), these thresholds convey spatial information because of their correlation to different body segment angles. This is one of the main principles that PRI non-manual techniques are based on. We are attempting to encode new threshold relationships between agonists and antagonists in synergistic patterns in specific positions which concurrently encode new spatial patterns with vestibular, visual, and auditory frames of reference.
To help understand this concept even more, wherever you are right now pause to do the following: Acknowledge the position you are in and how this feels. For example, if you are sitting where do you and don’t feel pressure? What angles are your body segments at? Can you sense whether your body is leaning or rotated in a particular direction? Are you moving? Are you on an object that is moving (car) or are you moving on an object (walking on the ground)? Are objects moving around you (cars or people)? What sounds do hear? Are they coming from far or near? Now for the punchline: ALL of what you just experienced, including what you see and hear is YOU. Not only is your body but also what you perceive beyond your personal space is YOU. It is YOUR NEUROSENSORY WORLD. The question then becomes: is your neurosensory world coherent on both sides of not only your body but also SPACE which includes the visual and sound fields?
If you exist in a lateralized body and world, you therefore not only posture and move differently on each side but you also perceive space such as the ground, gravity, objects, and sound asymmetrically as well. PRI practitioners are typically trying to teach our patients and clients to position and move in new ways to become less lateralized. However, in reality we are also simultaneously teaching them a new orientation and perception of space. Therefore, when you are working with your patient or client, try to imagine their entire neurosensory world (as you just practiced) and perceived reality. This “imagination” of neurosensory perception is what Ron Hruska bases his neurosensory decision making recommendations on. He interacts with patients to figure out how best to modulate their neurosensory world to achieve authentic reciprocal alternating body and space coherence.
In conclusion, the L AIC/R BC/R TMCC dominant pattern promotes a neurosensory illusion of being half lost in space and body. Therefore, when you are instructing your patients and clients in a PRI technique, consider not just the specific muscles and plane you are trying to inhibit or facilitate but also the corresponding sensory pieces to them. Many of these aspects are already in the techniques whether you realized it or not. Basically, any time you reposition the postural system you are concurrently reorienting its perceived space. Consider what other sensory mediums you can use to achieve this. This is why the Postural-Visual Integration course is so powerful because it emphasizes the visual aspect of our space which is a huge piece of our neurosensory world. I am really looking forward to learning how the auditory system can be engaged to instill coherent space and body function at this spring’s annual symposium…….