Brain Mechanisms of Action & Decision PDF
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University of York
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This document covers brain mechanisms of action and decision, including advanced movement topics such as optic ataxia, coordination, linking complex movements, and the roles of the cerebellum and basal ganglia. It also discusses various neurological disorders like Parkinson's and Huntington's disease. The document has various quizzes and figures.
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The Brain Mechanisms of Action and Decision Check-In Code: TBC Session 2: Advanced Movement First, let’s check in… Who wore it better? Quick recap Premotor cortex (PMA): Links action with visual objects. Selects appropriate movements. Modula...
The Brain Mechanisms of Action and Decision Check-In Code: TBC Session 2: Advanced Movement First, let’s check in… Who wore it better? Quick recap Premotor cortex (PMA): Links action with visual objects. Selects appropriate movements. Modulates primary motor cortex. An ‘intention’ area. Supplementary motor cortex (SMA): AKA the ‘supplementary motor area’. Well learned actions that do not place strong demands on monitoring the environment. Posterior parietal cortex: Is a ‘planning’ area. Also involved in spatial reasoning and attention. Primary motor cortex (PMC): Responsible for the execution of all voluntary movements of the body. Advanced Movement "Upon finding a rock or stationary object the sea squirt then becomes sessile, absorbs much of its own brain and returns to a rather primitive condition, a process paralleled by some human academics upon obtaining university tenure." Rodolfo Llinàs (1987) 'Mindness as a Functional State of the Brain' p-341. Advanced Movement Squirt Du Soleil Advanced Movement Todays class: Advanced Movement Making it look easy Action and goals Optic ataxia and coordination Linking complex movements The cerebellum and basal ganglia Hypo- and Hyper-kenetic disorders Parkinson’s, Huntington's and more… Chapter 5 (ps 148-165) Warm up quiz I Could a ninja catch an arrow mid-flight while in combat? A. True B. False Warm up quiz II How long does it take to become a professional ballet dancer? A. 2-4 B. 4-6 C. 6-8 D. 8-10 *According to the Atlanta Ballet Association. Warm up quiz III In Latin what does ‘cerebellum’ mean? A. Wrinkly brain B. Condensed brain C. Little brain D. Groovy brain Warm up quiz IV Tell me what sports, activities or hobbies you do that require fine motor movement? Sensory-motor coordination 6.5 hours travel time to the ISS. The ISS is 408 km high. It orbits at 17150 Miles Per Hour. Tim Peake Docking glitch High stakes skills Motor coordination factors to consider: Position of perspective in relation to body. The hand and arm relative to everything else. Feedback. Speed and hight. 1. Graded and competitive goal selection Selecting goals for action Graded activation (Roitman and Shadlen, 2002) 2. Sensorimotor transformation: reaching Helps locate targets Reaching This system is responsible for transforming visual information about the location of objects in extrapersonal space into the direction of a reaching movement (a visuomotor transformation). A path connects the parieto-occipital extrastriate area (PO), the mediodorsal parietal (MDP), the medial intraparietal (MIP) and the dorsal premotor area (PMd). 3. Sensorimotor transformation: grasping Helps with hand orientation Grasping This system is responsible for transforming visual information about the properties of objects, such as shape and size, into commands for effective grasping (another visuomotor transformation!). A path connects the dorsal extrastriate (ES) cortex with the Anterior Intraparietal sulcus (AIP), and then the ventral premotor area (PMv). Successful docking Motor coordination Successful Docking! solutions: 1. Attention to environment. 2. Goal selection. 3. Sensorimotor transformations. Optic Ataxia An inability to reach accurately under visual guidance – i.e. making Milner’s Posting Task visuomotor sensory transformations. Reaching accurately involves reaching in the right direction, with the correct grip scaling and grip orientation/finger placement. Visual guidance means being able to see both the target and the hand throughout. (Milner and Goodale, 1995) Dorsal and ventral streams Parietal cells represent locations of visual stimuli. The brain must transform between multiple coordinate systems to generate reaching to a visual target. Double Dissociation: Evidence that the parietal cortex helps the coordination of visual and position information for pre-motor areas. Complex movements Linking Sequences Linking sequences The SMA is essential for generating linked self- generated movements. Without it we would no longer be able to perform well learned movements and rely on external cues to get things done. There must be a functional dissociation between the pre-motor cortex and supplementary motor cortex for producing cued and uncued movements. Deactivation of the SMA produces severe disruption of learned sequences. (Tanji and Shima, 1994) The Cerebellum Dense Wrinkly ‘Silent’ Hard to measure Through the medium of road signs Error correction Signals leaving the motor cortex go through the cerebellum. It also gets signals on what the body is doing from the spinal cord. It compares the two and adjusts what you do to produce smooth motion. This is why I am informally referring to it as the ‘stabilizer’. Motor learning Cerebellar neuronal circuits learn to make more accurate movement the over time. After the motor act has been repeated many times (i.e. motor training), the successive steps of the motor act become gradually more precise. Once the cerebellum has perfectly learned its role in different patterns of movements, it establishes a specific motor program for each of the learned movements. ‘Ballistic’ movements These movements include writing, typing, talking, running etc. These movements occur so rapidly that it is almost impossible to depend for their control on the sensory feed-back. These movements are referred to as "ballistic" movements. Once the movement is activated there is no way to modify its present course by any sensory feed-back control mechanism. Cerebellum: Input and Output Motor error correction Motor error correction Reentrant circuits Cognitive error correction Motor error correction Cognitive error correction Reentrant circuits The cerebellum saves! Nastia Liukin 2006 Cerebellar dysfunction Cerebella Ataxia Hypometria & Dysdiadocho Response Delays kinesia Errors in range and Delayed response. direction of movement. Impaired ability Uncontrolled eye Hypometria: to perform rapid movements. movements short alternating Unsteady gait. of intended goal. movements. Slurred speech and more. Cerebellar ataxia Alcohol & field sobriety tests The FST allows police to gauge the extent you have been on the sauce. The cerebellum is sensitive to the ethanol found in booze. Cerebellum reliant aspects of the FST include: Walking in a line. Touching the tip of the nose with eyes closed. Quality control on bad ideas... The Basal Ganglia Inhibition Action selection Initiation The Basal Ganglia Loop Aka Striatum Basal Ganglia The Direct and Indirect Pathways There are ‘direct’ and 1. Red is excitatory glutamate ‘indirect’ pathways. 2. Blue is inhibitory GABA. 3. Pink is modulatory Dopamine. Hypokinesia Insufficient direct pathway output. Excess indirect pathway output. Hyperkinesia Excess direct pathway output. Insufficient indirect pathway output. The Direct Pathway: Stimulates movement D1 Dopamine Receptors = Direct Pathway Cortex (stimulates) striatum (inhibits) SNr-Gpi (less inhibition of thalamus) Thalamus (stimulates) cortex. Cortex then stimulates the corticalspinal tract via upper motor neurones lower motorneurones muscles = movement. The Indirect Pathway: Inhibits movement D2 Dopamine Receptors = Indirect Pathway Cortex (stimulates) striatum (inhibits) GPe (less inhibition of STN) STN (stimulates) SNr-Gpi (inhibits) Thalamus (is stimulating less) Cortex Cortex (is stimulating less) Upper motorneurones Stimulated less Lower motorneurones (stimulated less) Muscles (stimulated less) = flaccid muscles and less movement. Parkinson’s disease SYMPTOMS: Resting tremor in limbs(~4-5 Hz) that disappears on movement or during sleep. Muscle rigidity – resistance to passive movement: jerky (cogwheel) movement. Akinesia – general paucity of involuntary movement. Bradykinesia (slowness). Parkinson’s neurology Huntington’s disease Progressive disease causing involuntary muscle jerks. It will ultimately affect the whole body. Also intellectual deterioration, depression and occasionally psychoticism. Genetically determined (single dominant gene). Causes degeneration of the output neurones from the striatum, reducing inhibitory modulation of Huntington’s insights Huntington’s neurology Bringing it all together in a figure Bringing it all together in a figure skater Surya Bonaly Backflip (1998) For more info on this check out the two links in the notes section Monty and I would like you to remember 1. Goal selection is graded and competitive. 2. The SMA is essential for linking complex movements. 3. The cerebellum and basal ganglia help fine tune our movements. 4. Huntington's and Parkinson’s give us insights into basal ganglion function. 5. Advanced movements require an intricate set of checks and balances contingent on feedback.