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Testable Content for Midterm 2.docx

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Western University
Kinesiology 1080A/B
Matthew Heath

Psychomotor Behaviour – Testable Content for Midterm #2 Cerebral Asymmetries in Downs Syndrome - people with down syndrome perceive speech with right cerebral hemisphere; model of reversed cerebral specialization - right side is not optimized for speech perception - 50% of people with down syndrome are left handed (90% of gen. population is right handed, 99% have speech & language lateralized to left hemisphere) - In DS, problem with verbal-motive behaviours is thought to arise from right hemisphere speech perception & left hemisphere movement production  model of biological dissociation - In DS, corpus callosum is rounded. Rostral fifth is particularly thin, RF is important for between hemisphere communication (verbal) - For people with DS, verbal instruction is very difficult; visual is much more effective  overdeveloped mirror neuron system Spinal Cord Connections with Extrafusal Muscle (diagram) - golgi tendon organ – sends information back to spinal cord (dorsal root) and synapses onto the interneuron which then synapses onto alpha motor.  olligosynaptic – 2 synapses) - Propriospinal neuron  between segment communication, acts as a converging point, gathers information and shares it with multiple alpha motor neurons (relay system) - Interneuron – allows for synaptic activity within same area of spinal cord CC Modulation of Action of MNs in Brain Stem/Spinal Cord (Corticobulbar Tract) - motor neuron activity organized by cerebral cortex - corticobulbar fibres: extended from the motor cortex to the ‘bulb’ (brainstem) - controls facial musculature and mastication muscles - Upper and lower MNs - pyramidal tract (descending motor pathway): 1 million fibres. Brain stem to spinal cord; descending motor neuron control. Composed of axons whose neurons originate in the M1, SMA, PMA, parietal lobe (50% originate in M1) - Upper MN in M1 important for facial & mastication muscle innervation - The facial nucleus is divided into ROSTRAL and CAUDAL o Rostral (top) – innervates bilaterally (goes down and connects to both sides)  only innervates upper facial muscles o Caudal (bottom) – innervates contralaterally (from contralateral cortex, goes down and connects only to one side)  innervates lower facial muscles (mouth, jaw area) - Tumor (Right cortex) contralesional – upper motor neuron injury/impairment: contralateral paralysis, affects caudal tracts – asymmetrical smile - Lower motor neuron injury/impairment – axon impairment – complete paralysis on 1 side of face. Corticospinal Tract  Ventral & Lateral Ventral - M1, SMA, PMA, most projections from M1 - Axon descends uncrossed  ipsilateral connection - Majority innervate axial musculature - Synapse first at propriospinal neurons (between segment communication)  can send projections to alpha motor neurons, which can then innervate trunk muscles Lateral - Originate from M1, SMA, PMA, & Parietal cortex - 75% of fibres cross over at level of pyramids and innervate other side of the body - monosynaptic connections  synapse on 1 alpha motor neuron - monosynaptic allows for precise & independent digit control - Goal-directed actions - Control distal muscle movement (hand, fingers, elbow) - Fundamental component to our ability to use precision movements (why we are evolved) - Humans have great dexterity because of so many fibres due to the sophistication of the lateral corticospinal tract Difference between ventral & lateral corticospinal tracts - 1. Lateral connects with an alpha motor neuron - 2. Ventral connects to propriospinal neurons, which ultimately synapse with motor neurons (propriospinal neurons allow coordination between multiple motor neurons) Lesion to Lateral Corticospinal Tract - impairs fine coordination of individual digits - people with stroke often have difficulty performing daily activities; they can only make a fist when manipulating objects - chronic deficit (long road to recovery)  have to have intact lateral corticospinal tract - contralesional impairment; quick diagnosis Important Terms - innervation ratio  the number of muscle fibres innervated by a single alpha motor neuron (can vary from a few to 1000+) *think about precision (few more precision, ex- eye muscles vs quad muscles) - Extrafusal fibres  power producing muscle fibres external with respect to muscle spindles - Intrafusal muscle fibres  muscle fibres inside of the muscle spindles; innverated by a special system of fusimotor neurons Motor Neurons and Motor Units Alpha Motor Neuron: neuron innervating power-producing muscle fibre Motor Unit: alpha motor neuron + all the muscle fibres – much larger than gamma motor neurons - the number of muscle fibres associated with a motor unit ranges from 10 (eye) to thousands (back musculature) - fibre diameter determines how rapidly it conducts - alpha motor neuron = much wider than gamma motor neuron - Neuromuscular junction: location where motor neuron synapses with the muscle fibre - Motor neuron pool: alpha motor neurons and all motor fibres associated w it. Fusi-Motor Neurons (Gamma) - small neurons innervating intrafusal muscle fibres and changing sensitivity of muscle response to dynamic stretch  gamma motor neurons detect stretch - intrafusal muscle fibre: INSIDE the muscle o Stretch = spatial info (where is our muscle?) o Run in parallel with outside fibres o Polar-to-polar (1 end of muscle to another) – really helps to detect stretch Motor Unit Types 1. Fast-Twitch, fatigable (FF) (Fast Motor Unit)  Highly myelinated  rapid impulses  Large fibre diameter  Characterized by high conduction velocity (100m/s)  Innervate fast twitch muscle fibres  High force, fatigues very quickly, fast contraction  Doesn’t rely on oxygen for energy source 2. Fast Twitch, fatigue-resistant (FR)  Medium conduction velocity (60m/s)  Medium fibre diameter  Innervate fast and/or slow twitch muscle fibres  Resistant to fatigue, fast contraction 3. Slow twitch, fatigue-resistant (SR)  Slowest conduction velocity (40m/s)  Small fibre diameter  Innervate slow twitch muscle fibres  Slow contraction, low force, highly resistant to fatigue Motor Unit and Muscle Fibre Types in Athletes - sprinter: 80% fast, 20% slow  fatigues, but has fast contraction speed - marathoner: 20% fast, 80% slow  does not fatigue as quickly, slow contraction speed) - average person: 50% fast, 50% slow - Couch potato: 60% fast, 40% slow - Spinal injury: 96% fast, 4% slow  why? Cannot sustain repeated movements (endurance) - Older adult: slow motor units. Ex- slip on ice, can’t maintain postural stability - This all demonstrates the plasticity of motor unit types Koceja Study - wobble board training  if you put older adults on it and train for 6 weeks, there will be an increase in fast twitch fibres - postural support  improvement with their balance The Henneman Principle (Size Principle) - associated with the recruitment of muscle fibres and motor units - as force increased, so does fibre recruitment - low force contraction – nearly all force produced by slowest motor units - if contraction force increased, larger motor neurons start to fire (FR unit types activated) - at the highest levels of force (maximal voluntary contraction) the largest motor units are recruited (all unit types activated) Synesthesia: “blending of the senses”, higher ability to consolidate information in long-term memory due to the fact that it is bound in 2 senses ERP Measures of Cognitive Processing ERP: Event related brain potential - measure using EEG  measures electrical activation of cortex Measuring neuronal activation - expose someone to stimuli & record the activations - N2pc = ERP related to the focusing of visuospatial attention - P300 = measure of stimulus classification processing speed - Why you may get astecondary impact injury DeBeaumont Study  1 study to show long term physical problems - 3 groups of athletes: non-concussed, concussed 1x, concussed 2x - 9 months removed from activity from which concussed - coloured trails test  #’s & colours (follow #’s) o no group differed on the impact battery (tests) - classification test  focus on stimuli (open end box) with EEG cap on head o speed for response same across all groups o n2pc – same across all groups o p300 – amplitude of p300 decreased as frequency of concussion increased o important in displaying the difference between physiological vs. psychological o neurons not firing (as effectively) in those with multiple concussions in classification of stimuli - the specificity of the long term effect of concussion provides a framework to pinpoint the cognitive system impaired in multiple concussions - Prosaccaed – when you look at a stimulus; entail direct spatial overlap between stimulus and response - they are stimulus driven - often reflexive  doesn’t take a lot of time to initiate a prosaccaed. - 180ms to initiate (aka – reaction time) Antisaccaed – looking mirror symmetrical to a stimulus - important because they provide us with a measure of top-down inhibitory control - this is because the first thing you have to do is inhibit the normally reflexive stimulus driven prosaccaed  response suppression. - They have to do vector inversion, which is a process where you have to perform a 180 degree spatial transformation of the target’s location. (intraparietal) - Might have a reaction time of 300ms – much longer to initiate. - The importance of them is that they provide us with a window to look at inhibitory control  Entail the same cortical and subvisual networks as prosaccaeds (areas in the frontal cortex).  Neurons in those areas are much more active for a antisaccaeds  thought to be related to response suppression.  Brain needs to work a lot harder to suppress a response - schitsofrenia  will prosaccaed instead of antisaccaed. Reflexive vs inhibit. - This is because their frontal lobe is not functioning properly MCI – Mild Cognitive Impairment - usually older adult - symptoms of forgetfulness; mild cognitive deficits - thought that people with MCI are on a progression towards Alzheimer’s. - use the antisaccaed task in Heath’s lab to compare to age matched controls – they perform poorly. *The very simple antisaccaed test can evaluate important conditions. Task Switch Impairment – switch costs - AABB tasks (pro pro then anti anti) - To see the cost of switching from one task to the other - Measuring reaction time - Findings: when you switch from pro to anti, there is no cost. Therefore the anti has a normal reaction time - When you switch from anti to pro, the subsequent pro has a significant cost. Task switch prosaccaed has a cost. = Unidirectional prosaccaed switch cost. - Response suppression leads to a residual inhibition of ocular motor networks - therefore the prosaccaed cannot be initiated as quickly The SNARC Effect – Spatial Numerical Association of Response Codes - idea that we all have a mental number line; most people: ascending left to right order - people who do a randomized version of this number line tend to be more creative people - how numbers influence movement - study: fixation cross in the middle of a display to focus on – 1,2 on left and 8,9 flashed on the right. - When you flash 1 & 2 in the left visual space participants had shorter movement times and shorter reaction times than when 8 & 9 was flashed in the same visual space - Vice versa for 8 & 9 in the right visual space. - When we move, we have this mental number line, when we get a stimulus that is congruent with this mental number line, then movement is optimized. Why in Hollywood movies the person who draws last wins the gun fight? - if you draw first, you make a top down decision.  lots of cortical activati
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