Brain in Action 01 Feb 2024 PDF

Brain in Action 01 February 2024 16:29 Main Ideas Notes 1. Concepts and Keywords ○ Neuron: Basic unit of the nervous system. ○ Action Potentials: Electrical impulses for neural communication. ○ Neural Tuning/Coding: Mechanism by which neurons respond to stimuli. ○ Synapse: Junction between two neuro...

Brain in Action 01 February 2024 16:29 Main Ideas Notes 1. Concepts and Keywords ○ Neuron: Basic unit of the nervous system. ○ Action Potentials: Electrical impulses for neural communication. ○ Neural Tuning/Coding: Mechanism by which neurons respond to stimuli. ○ Synapse: Junction between two neurons for signal transmission. ○ Cognitive Process: Involves motivation/goal, volition, planning, initiation, execution, monitoring, and stopping of actions. ○ Generally serial, resource -intensive, feedforward ○ Generally continuous, resource -independent, feedback ○ Neuroanatomical Pathway: Physical pathways in the brain for action control. 2. Theories and Models ○ Hierarchical Action Control: Concept that action control is organized in a hierarchical manner in the brain. ○ Computational Model of Action Control (Blakemore et al): Describes cognitive processes in action control using goal/intention, planner motor command (inverse model), efference copy, forward model, and sensory feedback. ○ Spinal Stretch Reflex Circuit: Demonstrates reflexive action at the spinal level, involving muscle spindle, dorsal root, ventral root, and motor neuron. 3. Hypotheses ○ Hierarchical control hypothesis: Actions are controlled at different levels of the nervous system, with higher levels (e.g., cortex) for complex planning and lower levels (e.g., spinal cord) for execution. ○ Computational efficiency hypothesis : Suggests that delegating control to lower levels (like the spinal cord) allows the brain to focus on higher -level functions. 4. Practical Applications ○ Brain-Computer Interface (BCI): Illustrates the application of hierarchical motor control, bypassing lower motor hierarchy levels. 5. Key Insights ○ Action control involves both high -level cognitive processes and specific neuroanatomical pathways. ○ The spinal cord plays a crucial role in action execution, especially in reflex actions. ○ Higher brain functions, such as planning and decision -making, are integral to voluntary action control. Summary 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Glossary EMG (Electromyogram): A technique to record electrical activity of muscles. Synergy: A coordinated action of muscles producing movement. Equifinality: Ability to achieve the same outcome through different motor pathways. PTN (Pyramidal Tract Neuron): Neurons in the corticospinal tract projecting to the spinal cord. CM cell (Corticomotoneuronal cell): Directly connects M1 to spinal motor neurons. Neural coding: Process of how neurons represent various aspects of the environment or movement. Precentral gyrus: Part of the frontal lobe where M1 is located. Plasticity: The brain's ability to change and adapt, especially in response to learning or experience. Corticospinal tract: Major pathway connecting the brain to the spinal cord for motor control. Somatotopy: The point-for-point correspondence of an area of the body to a specific point on the central nervous system. PSYC0032 The Brain in Action Page 1 Notes The Visual System as an Example of Pathway Organisation Afferent pathway: Begins with photoreceptor cells in the retina capturing light, transforming it into electrical signals. Cortical pathway: Signals travel from the optic nerve to the lateral geniculate nucleus (LGN) of the thalamus. Hierarchical processing: From LGN, signals reach the primary visual cortex (V1), where basic features like orientation and spatial frequency are processed. Retinotopic mapping: Visual information is organized spatially in V1, preserving the spatial relationships found in the retina. Dorsal and ventral streams: After V1, the visual pathway splits; the dorsal stream processes 'where' and the ventral stream 'what'. Parallel processing: Different attributes (color, motion, form) are processed simultaneously in specialized cortical areas. Feedforward processing: Information flows in one direction from retina to higher visual areas for initial processing. Feedback mechanisms: Higher visual areas can modulate the activity of lower areas, enhancing feature detection. Functional specialization: Specific regions (e.g., V4 for color, MT for motion) are dedicated to processing particular visual aspects. Binding problem: Integration of disparate features into a single percept occurs at higher cortical levels. Pathway Organisation of Action Control in the Brain Motor cortex: Initiates and directs voluntary movements. Basal ganglia: Involved in movement selection and initiation, receiving input from the cerebral cortex and sending output back via the thalamus. Cerebellum: Coordinates timing and precision of movements, adjusts motor output to maintain balance and smooth motions. Prefrontal cortex: Involved in planning complex behaviors and movements. Supplementary motor area (SMA): Plays a role in the coordination of movements, particularly sequences. Premotor cortex: Integrates sensory information and guides movement selection based on external cues. Brainstem: Contains motor nuclei controlling facial expressions and core muscle groups for posture. Spinal cord: Final relay for motor commands heading to muscles, integrating reflexes and central commands. Hierarchical control: Higher brain centers modulate the activity of spinal motor neurons to shape actions. Reciprocal inhibition: Ensures that when one muscle contracts, the opposing muscle relaxes, facilitating smooth movement. Reverse Engineering Human Actions Observation and imitation: Studying how humans replicate observed actions to understand the underlying mechanisms. Motion capture technology: Collects detailed data on human movement for analysis. Computational modeling: Simulates human motor control to predict and replicate actions. Robotics: Utilizes findings from human action studies to improve machine motor functions. Functional MRI (fMRI): Visualizes active brain areas during action execution and observation. Electrophysiology: Records electrical activity of neurons during movement to understand control processes. Transcranial magnetic stimulation (TMS): Probes the function of specific brain regions in real-time during tasks. Lesion studies: Examine changes in action control following damage to specific brain areas. Neuropsychological testing: Assesses how different brain disorders affect motor function. Artificial intelligence: Incorporates principles of human action control into algorithms for autonomous systems. Notes Two Key Hierarchical Levels of the Motor Pathway Associated with Distinct Cognitive Processes Primary motor cortex (M1): Directly commands muscle contractions for movement execution. Premotor and supplementary motor areas: Involved in the preparation and planning of movements. M1 Neurons: Encode force and direction of movements. Premotor cortex: Selects movements based on external cues and internal intentions. Supplementary motor area: Coordinates sequences of movements and bimanual tasks. Motor planning: Involves the anticipation and organization of movements before they occur. Decision making: Premotor areas contribute to deciding between different motor actions. Sensorimotor integration: M1 integrates sensory feedback for ongoing adjustment of movements. Cognitive control: SMA and premotor cortex are involved in the voluntary control of actions. Learning and memory: Both regions are implicated in motor learning and the consolidation of motor skills. 1. Motor Cor Corticospina MI Neuroana 5). Monosynapti connections Spinal Stretch Reflex Circuit Monosynaptic reflex: The simplest reflex arc, involving only one synapse between the afferent and efferent neuron. Muscle spindle: Detects stretch in a muscle and sends information to the spinal cord. Alpha motor neurons: Efferent neurons that directly innervate muscles to contract. Reciprocal inhibition: Antagonist muscles are inhibited during the reflex to prevent conflict. Gamma motor neurons: Adjust the sensitivity of muscle spindles. Central pattern generators: Spinal circuits that can produce rhythmic muscle contractions independently of brain input. Reflex modulation: Can be influenced by descending signals from the brain. Synaptic plasticity: The strength of reflexes can change with experience and learning. Protective function: The reflex protects muscles from overstretching and injury. Clinical relevance: Reflex testing is a diagnostic tool for assessing the integrity of the nervous system. 3. Neural Co General Defi Methods of S Identifie Popula feature BCI: An Application of Hierarchical Motor Control Brain-computer interface (BCI): Technology that translates brain activity into commands for external devices. Signal acquisition: Brain signals are recorded using EEG, fMRI, or implanted electrodes. Signal processing: Algorithms decode the brain activity patterns associated with intention to move. Output devices: Can range from computer cursors to robotic limbs or wheelchairs. Feedback systems: Provide the user with sensory input to refine control of the BCI. Adaptive algorithms: BCIs can learn and adapt to individual users' brain patterns over time. Restorative applications: Aims to assist individuals with motor impairments or paralysis. Neurofeedback: Used for rehabilitation, allowing patients to visualize and modify their brain activity. Research tool: BCIs contribute to understanding of the neural basis of motor control. Ethical considerations: Raises questions about privacy, autonomy, and enhancement. 2. MI Somat Somatotopic muscles. Fractured So questions ab Key Concep “Movements movements. Population S Motor Equifin Summary Po Primary Moto Complex MI Hebbian Syn Additional T Propriospina Spike-Trigge force. Notes rtex (MI) Anatomy, Connectivity, and Function al Tract: Main pathway for MI to control muscles. atomy: Layered structure with specific layers for input (Layer 4) and output (Layer ic and Polysynaptic Projections: Techniques like retrograde viral tracing reveal from MI to muscles. otopy c Motor Map: Systematic relation between cortex neuron locations and connected omatotopy: Dispersed representation of muscle control in the cortex, raising bout MI organization. oding inition: Relationship between neuron firing and stimulus/movement parameters. Study: ed Neuron Studies: Investigate specific neurons' role in muscle movement. tion Studies: Analyze correlations between large neuron groups and movement es. pts or Muscles?” Controversy: Debate whether MI codes for muscle force or Synergies: MI organizes neurons to code for multi-muscle actions. nality: Multiple ways to achieve the same action goal. oints or Cortex Role: Direct muscle access, essential for fine motor skills. Somatotopy: Multiple neuron-muscle mappings. nergy Model: Suggests computational efficiency in MI's organization. Topics al Tract: Role in dexterity and its evolutionary significance. ered Averaging: Technique for understanding MI neuron contributions to muscle PSYC0032 The Brain in Action Page 2 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Reverse Engineering Human Actions Reverse engineering: Understanding human actions by analysing their underlying causes. Focuses on identifying the stimuli or reasons behind specific actions. Involves deciphering the complex process from output (action) to the input (cause). Aids in understanding the cognitive and physiological processes behind actions. Utilizes a multidisciplinary approach, including psychology and neurology. Employs techniques like behavioral analysis and neuroimaging. Seeks to unravel the decision-making process leading to an action. Examines the role of external factors (environmental, social) in influencing actions. Investigates the impact of internal states (emotional, cognitive) on actions. Aims to create models or algorithms that predict human behavior. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Notes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Non-invasive Mapping of Motor Cortex with Transcranial Magnetic Stimulation Transcranial Magnetic Stimulation (TMS): A non-invasive technique to stimulate the brain. Used to map functional areas of the motor cortex. Induces electric currents in the brain, eliciting motor responses. Helps in identifying the motor representation of different body parts. Useful in studying brain plasticity and recovery post-injury. Assists in diagnosing and understanding neurological disorders. Can temporarily disrupt normal brain activity to study its effects. Aids in therapeutic interventions for conditions like depression. Provides insights into the connectivity between brain regions. Safe and painless, making it suitable for repeated use in clinical and research settings. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Two Approaches to Neural Coding Identified neuron approach: Focuses on specific neurons and their roles Useful in understanding the direct relationship between neuron activity a Involves detailed study of individual neurons, often through invasive me Population coding approach: Studies the collective behavior and pattern Useful for understanding complex brain functions and overall neural net Involves statistical and computational methods to analyse large neuron Offers insights into how the brain integrates information from various sou Both approaches provide complementary insights into neural coding. The choice of approach depends on the research question and the leve Advances in technology and methodology are continuously refining thes M1 Physiological Output Pathways: Corticospinal Tract Corticospinal tract: Major pathway for motor output from the brain to the spinal cord. Originates in the primary motor cortex (M1). Responsible for voluntary precise movements, especially in the limbs. Involves both the lateral and anterior corticospinal tracts. Lateral tract: Controls movement in distal limbs, especially fine motor skills. Anterior tract: Influences trunk and proximal limb muscles. Majority of fibres decussate (cross over) at the medullary pyramids. Direct connection between brain and spinal motor neurons. Essential for tasks requiring dexterity, like writing or typing. Damage to this tract can result in motor deficits and loss of voluntary movement. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. Somatotopy is "Fractured" Fractured somatotopy: Non-contiguous representation of body parts in M1. Challenges the traditional view of a continuous homunculus. Indicates a more complex and distributed motor representation. Suggests overlapping areas for different muscle groups. May provide a basis for motor redundancy and flexibility. Reflects the brain's ability to adapt and reorganize. Could be a result of evolutionary changes in motor demands. Implies multiple neuronal pathways for controlling a single muscle. Offers insights into the neural basis of motor coordination. Has implications for understanding and treating motor disorders. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. Movements or Muscles? Controversy Focus of controversy: Whether M1 primarily codes for individual muscle Muscle-centric view: M1 neurons encode specific muscle contractions. Movement-centric view: M1 is involved in coding complex movements, n Studies show M1 neurons' activity correlating with muscle force (muscle Other studies indicate M1 involvement in task-specific movements (mov The controversy highlights the complexity of motor control and neural co Ongoing debate in the neuroscience community. Implications for understanding motor disorders and rehabilitation. The controversy is crucial for developing effective neuroprosthetics. Future research may provide more clarity on M1's exact role in motor co 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. M1 Neuroanatomy: Microscopic Microscopic neuroanatomy of M1: Focuses on cellular and synaptic structures. Layered structure, with each layer having distinct types of neurons and functions. Layer 5: Notably prominent, containing large pyramidal neurons. Pyramidal neurons: Key role in sending motor signals to the spinal cord. Contains Betz cells: Some of the largest neurons, involved in motor functions. Dense network of dendrites and axons facilitating complex neural interactions. High degree of synaptic plasticity, allowing for learning and adaptation. Interneurons play a crucial role in modulating output signals. Myelination in axons aids in rapid signal transmission. Synaptic connections with sensory areas for integrating sensory and motor information. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. What is Neural Coding Neural coding: The mechanism by which information is represented in the brain. Involves understanding how neurons encode various stimuli and responses. Focuses on the relationship between neural activity and behavioral output. Key for deciphering how the brain processes and transmits information. Involves studying patterns of neural firing and synaptic interactions. Essential for understanding sensory perception, cognition, and motor control. Utilizes techniques like single-neuron recording and functional imaging. Aids in developing brain-computer interfaces and neuroprosthetics. Challenges include deciphering the complexity of neural networks. Provides insights into learning, memory, and neural plasticity. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. Centre-Out Task Centre-out task: A standard experimental paradigm in motor control stud Involves moving a cursor from a central point to various targets. Used to study motor planning, execution, and control. Helps in understanding directional tuning of motor cortex neurons. Provides insights into how movement direction is encoded in the brain. Often used in combination with neural recording techniques. Aids in studying the role of motor cortex in spatial movement control. Useful in understanding motor learning and adaptation. Helps in investigating the effects of neural disorders on motor control. Provides a controlled environment for studying complex motor tasks. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Monosynaptic and Polysynaptic Projections from M1 to Muscles Monosynaptic projections: Direct connections between M1 neurons and spinal motor neurons. Key for rapid and precise motor control. Polysynaptic projections involve intermediate interneurons, allowing complex motor patterns. Provide a basis for graded control of muscle activation. Involved in reflex arcs and automatic motor responses. Enable modulation of motor signals for smooth execution of movements. Contribute to the precision and variability of motor tasks. Essential for complex tasks requiring coordination of multiple muscles. Aid in the distribution of motor commands to various muscle groups. Allow for adaptive motor responses to changing environmental conditions. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. Two Contrasting Methods for Studying Neural Coding Identified neuron studies: Focusing on specific neurons and their connections. Aids in understanding the role of individual neurons in coding. Involves tracing neural pathways and recording from identified neurons. Provides detailed insights into neural circuitry and function. Population studies: Analysing the collective behavior of neural groups. Offers insights into how neural networks process information. Involves statistical analysis of large-scale neural activity. Can reveal patterns and principles not evident in single-neuron studies. Useful for studying complex brain functions like consciousness and decision-making. Challenges include managing and interpreting large datasets. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. Population Vector Population vector: A method to represent the overall direction of movem Combines the firing rates of multiple neurons to predict movement direc Used in studies of motor cortex to understand how movement direction i Reflects the collective activity of a neural population rather than individu Provides a way to visualize and quantify the overall tendency of motor a Useful in decoding brain activity in brain-machine interface applications. Aids in understanding how the brain coordinates complex motor tasks. Demonstrates how diverse neural signals can converge to represent a u Offers insights into the neural basis of motor coordination and planning. A fundamental concept in population coding studies in neuroscience. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. M1 Neuroanatomy: Location and Somatotopy Location of M1: Located in the precentral gyrus of the frontal lobe. Adjacent to the central sulcus, separating it from the sensory cortex. Somatotopy: Representation of different body parts in distinct M1 areas. Motor homunculus: Map showing body part representation in M1. Proportional representation: Body parts requiring fine control occupy larger areas. Distinct areas for hand, face, and tongue movements. Organization reflects the degree of motor complexity of different body parts. Dynamic organization: Can change based on learning and experience. Involved in planning and execution of voluntary movements. Connectivity with other brain areas for integrating sensory and motor information. "Movements or Muscles?" Controversy Muscle-centric view: Primary motor cortex codes for individual muscle contractions. Supports the idea of low-level coding of motor actions Centres on the idea that M1 primarily influences muscle force. Evarts' study (1968) supports this view, showing neuron firing rate correlates with muscle contraction. Challenges from studies indicating M1's involvement in broader movement patterns. Movement-centric view: Suggests M1 codes for complex movements rather than individual muscles. Supports high-level coding, where neurons contribute to task-specific movements. Emphasizes the role of M1 in coordinating multiple muscles for fluid movements. Controversy reflects the complexity of understanding M1's role in motor control. Ongoing research is essential to resolve this debate and improve our understanding of motor cortex functionality. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. Population Coding Studies Population coding studies: Investigate how groups of neurons collective Focus on the patterns and interactions of neuron populations. Employ statistical and computational methods to analyze neural data. Provide insights into how complex information is processed in the brain. Used to understand high-level brain functions like decision-making and Challenge the traditional focus on single-neuron studies. Offer a more holistic view of neural processing and representation. Essential for advancing brain-computer interface technologies. Provide a basis for developing computational models of brain function. Critical for understanding the neural basis of cognitive processes and be 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. Notes in coding. nd motor output. hods. s of neuron groups. work behavior. groups. urces. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. of detail required. e approaches. Population Synergies in M1 Population synergies: Concept of coordinated activity among groups of neurons in M1. Essential for producing complex and fluid motor actions. Synergies involve simultaneous activation of multiple muscles. Provide a framework for understanding how movements are organized in the brain. Reflect the brain's strategy for simplifying control of numerous muscles. Studied through techniques like intracortical microstimulation (ICMS). Offer insights into the neural basis of motor learning and adaptation. Important for understanding motor disorders and developing rehabilitation strategies. Challenge the traditional view of one-to-one correspondence between neurons and muscles. Highlight the complexity and efficiency of motor control in the brain. s or coordinated movements. not just muscle activity. -centric view). vement -centric view). ding. 1. Evarts et al. (1968) What They Did: Investigated how primary motor cortex (MI) neurons encode muscle force. Findings: Demonstrated that MI neurons encode muscle force, not movements (low-level coding). Implications: This study supports the theory that the primary motor cortex is primarily involved in controlling muscle force rather than coordinating complex movements. 2. Shenoy et al. (2011) Study Focus: Analyzed multiple MI/PMd neurons during the preparation period of a delayed reaching task. Findings: Found that individual neurons have varied response profiles; the pattern of activity across multiple neurons stabilizes during preparation. Implications: This suggests that motor preparation involves a complex, coordinated activity across multiple neurons, challenging the simplicity of earlier models of motor cortex function. ntrol. dies. 3. Lawrence & Kuypers (1968) Experiment: Created bilateral pyramidal tract lesions in the brainstem. Outcome: Observed a lasting deficit in fine finger movement. Implications: This study underscores the critical role of the pyramidal tract in controlling fine motor movements, particularly in the fingers. 4. Strick and Colleagues (Retrograde Viral Tracing) Methodology: Used rabies virus injections in muscle and analyzed retrograde transport to spinal motor neurons and the cortex. Outcome: Helped map the connections from muscles to MI. Implications: Provided a more detailed understanding of the neural pathways from the MI to muscles, highlighting the complexity of motor control at the neural level. ent encoded by a group of neurons. ion. s encoded. al neurons. ctions. 5. Spike-Triggered EMG Averaging in MI Approach: Used spike-triggered electromyogram (EMG) averaging during single-neuron recording in MI. Key Discovery: Identified that an MI cell can contribute to force in several muscles, indicating a one-to-many mapping. Implications: This finding suggests a high level of task specificity in the MI, where some neurons may drive a muscle in one task but not another, indicating a complex coding system for tasks within MI. nified motor command. 6. Fractured Somatotopy (Microstimulation Studies) Study Method: Applied microstimulation to the motor cortex. Findings: Showed that neurons driving a specific muscle are not grouped together but scattered and interspersed with neurons projecting to other muscles. Implications: This challenges the traditional understanding of somatotopy in the motor cortex and suggests a more complex organizational structure. y encode information. movement control. 7. Wilder Penfield's Studies (1930s-1960s) Procedure: Conducted intraoperative direct electrical stimulation of the cortical surface during neurosurgery for epilepsy. Result: Developed the concept of the "Penfield homunculus," illustrating a somatotopic motor map. Implications: This classic study provided foundational insights into how different areas of the MI are systematically related to control of different muscles and body parts. ehaviors. PSYC0032 The Brain in Action Page 3 Notes Notes PSYC0032 The Brain in Action Page 4 PSYC0032 The Brain in Action Page 5