PROPRIOCEPTION SLT301 WEEK 2 ROSALIND ROGERS Using a computer metaphor, inside our cortex, we constantly ‘run a programme’ that creates an internal model of where our body is, in real time. This dynamic internal body map or schema captures an accurate internal 3D representation of our body’s dimensions, body mass –both at a macro and micro level of detail. It details our body posture and it’s positioning. At a macro level we need to know our body shape and place in relation to our environment. At a micro level, we need to know the relationship of each part to another. This may be where our fingers are to each other, or where our feet are in relation to each other. It also includes small details. For example, where our tongue position is in order to plan where to begin to plan to produce a speech sound –is our tongue raised at the back as for producing /k/ or is the tongue flattened out for certain vowels? We need to know where our lips are in relation to each other –open or closed- in order to bring a cup of tea safely to our mouth. How do we do this? We process and interpret information from our skeletal muscles and joints, which is using a sense called proprioception –literally one’s own perception of one’s body. We also use other senses, where possible, to build up and to check the accuracy of our internal model. We also use vision, touch and vestibular information in order to make this internal model as accurate as possible. What makes the accuracy of this internal body model so important? In order to execute a movement correctly, you have to work out a plan from your current body position. So, starting to walk, do you need to stand up, change your point of gravity, and where will you place your first step? If your current body position is not accurately represented in your CNS, then you will have to use a ‘trial and error’ approach to that motor action. In summary, it is critically important for us as humans to develop an accurate internal body representation, which dynamically reflects real time changes in our body position. So, lets then explore proprioception as the most essential sense for this internal body model As a sense, it does not give information about our bodies when they are static. However, any time that our muscles or joints sense that our body or limb position, or posture, has changed, proprioceptive information is communicated to our CNS. What are the Receptors for Proprioception? This has been introduced in Stage 4 of the Pathways and Routes Unit, when we were looking at sensory feedback from muscles and joints. 1.Muscle Spindles 2.Golgi Tendon Organs 3.Joint and Ligament receptors –Ruffini Endings and Paciniform endings, also called Pacinian corpuscles What are the pathways for proprioception? First need to draw out the difference between: Subconscious proprioception; co-ordinates basic postural control -POSTURE Conscious proprioception: important for complex motor activity which is cortically planned and hence conscious; mainly in Dorsal Column and to some extent Spino-Cervical KINAESTHESIA…movement The conscious proprioception route from kinaesthesia receptors travels in two general pathways • Spinal Cord to Thalamus to Cerebral Cortex • Spinal Cord to Cerebellum to Thalamus to Cortex. The Dorsal Column Medial Lemniscal Tract (DCML) conveys localised sensations of fine touch, vibration, two point discrimination, and conscious proprioception from the skin and joints to the postcentral gyrus of the cerebral cortex. The Trigeminal Pathway carries somatosensory information from the face, mouth, outer two thirds of the tongue and the dura mater covering the brain. Conscious proprioceptive input travels along with discriminative touch in the trigeminal lemniscus. The Spinocerebellar Pathway This pathway conveys unconscious proprioceptive information to the cerebellum. It is an important tract because it allows us to make postural adjustments when we are moving, without engaging our cortex. Beyond the Pathways: What happens at the Cortex? Proprioception information is processed in three main areas in the cortex: 1. The Motor Network, which is covered in the Motor Control System notes in Stage 4 in the Pathways and Routes Unit. 2. Somatosensory Cortex and the Specialised Parietal system which is in the posterior parietal lobes and the relevant association areas 3. Right Inferior Frontal to the Parietal Lobe network HAPPENS IN PARALLEL! Areas of the primary motor cortex are activated when afferent muscle spindle information is being processed in the parietal lobes. 1ST: the processing at the primary sensory area in the somatosensory cortex. 2ND: the associative level where the incoming stimuli is made sense of within that sensory system, 3RD: the integrative level, where the specific sensory association areas exchange information within and across the hemispheres. This is in order to verify the accuracy of the internal body model using all related senses’ information. This is a video showing how children with proprioceptive challenges might present https://www.youtube.com/watch?v=b2iOliN3fAE This is an excellent video presenting children with Sensory Processing Disorder SPD We will watch the intro and then from 5.27. https://www.youtube.com/watch?v=D1G5ssZlVUw https://www.youtube.com/watch?v=wvDi5B_7Cv0 What Proprioceptive pathway is not being tested in this typical neuro exam? Analyse these actions with respect to the use of this sense? Scooter Board https://www.youtube.com/watch?v=3plxeImXwyY https://www.youtube.com/watch?v=Fg9X33 TNLkU This is a 5 year old Ninja! https://www.youtube.com/watch?v=tcQojvS y_QM&t=415 This is the six year old Ninja!
