Brain Centres & Sensory Impairments PDF

Brain Centres & Sensory Impairments T3 Systems │ CNS Class 3 │ October 2024 Brain Centres Thalamus Centrally located, near hypothalamus, hippocampus and amygdala Essential to sensory system Interacts with numerous brain centres Thalamus (cont’d) Thalamus has areas “matched”...

Brain Centres & Sensory Impairments T3 Systems │ CNS Class 3 │ October 2024 Brain Centres Thalamus Centrally located, near hypothalamus, hippocampus and amygdala Essential to sensory system Interacts with numerous brain centres Thalamus (cont’d) Thalamus has areas “matched” with partner areas in sensory cortex Functions as relay station for afferent data sent to brain Thalamus (cont’d) “Gates” data; suppresses info with less importance Burst: Alerts brain of new info Tonic: Transmits the info to the centre Selects data transmission routes Acts as a hub among brain centres Sensory Cortex Data from thalamus re- constructed in sensory cortex, analyzed and assigned sensory experience Sensory Cortex (cont’d) S1: Organized somatotopically – according to body part mapping Sensory Cortex (cont’d) Homunculus organization: ? In-coming data for a body part coalesces in S1 area for that body Sensory Cortex (cont’d) Modality & location data from S1 interpreted broadly in S2 areas, creating integrated picture Sensory Impairments Convergence Convergence of signals from different body locations can cause interpretation confusion Origin of pain can be unclear Convergence (cont’d) ?: e.g. of convergence problem - pain perceived at location other than site of stimulus/origin Convergence (cont’d) Referred pain (cont’d): Brain tends to interpret converged signals as coming from body surface tissues, since deeper structures have less 1° neuron receptors Convergence (cont’d) Scleratomal sensation sometimes merges with convergence issues. The Role of Individual History Individual history can influence how brain interprets afferentation Individuals can be hypersensitive or desensitized to sensations in certain tissue areas Proximal Depolarization Interpretation confusion about signals coming from a location along the neuron vs from the receptor. Proximal Depolarization (cont’d) Carpal Tunnel Syndrome & Cubital Tunnel Syndrome: ? Proximal Depolarization (cont’d) Can occur in the spine Sciatica: Symptoms along sciatic nerve caused by proximal depolarization at nerve root Irritation of C- spine nerves can mimic symptoms of thoracis outlet syndrome Phantom Phenomena Sensation experienced in body part that is no longer present Can be initiated via: 1. Proximal depolarization: Proximal nerve segments still able to transmit to 2° neurons Phantom Phenomena (cont’d) 2. As brain-generated phenomenon: Brain continues to receive info that appears to be coming from missing tissues Phantom Phenomena (cont’d) Adaptations in sensory cortex for missing body part do occur Sense of its existence can shift e.g. Telescoping: Perception that amputated body part moves closer to stump Phantom Phenomena (cont’d) Those born without certain body parts don’t have same developed sense of their existence (but may still experience phantom sensations) Many amputees have chronic phantom pain Phantom Phenomena (cont’d) Mirror therapy (and VR) has been used to treat phantom limb pain Essentially, brain is tricked into thinking there is nothing wrong with amputated limb