These notes provide an overview of the entire course in outline form. A more detailed sample lecture outline is also included.
Course Overview
Introduction
Issue 1: What is Controlled?
- Striated muscles (n=640)
- Tendons
- Bones
- Joints
- Soft tissue
- + Smooth muscles
- + Glands
Distinction Between Voluntary and Involuntary Movements:
- Reflexes
- Example: patellar reflex (myotatic reflex)
- Is a knee jerk not voluntary?
- Modulation of reflexes
- Jendrassik maneuver
- Suppression of reflexes
External:
- Visual
- Auditory
Issue 2: Cues Used by the Nervous System
- Reflexes
- Example: patellar reflex (myotatic reflex)
- Is a knee jerk not voluntary?
- Modulation of reflexes
- Jendrassik maneuver
- Suppression of reflexes
External:
- Visual
- Auditory
- Touch/Pressure
- Pain
- Gravity
- Receptors
- Olfactory
Internal:
- Proprioreceptors
- Receptors in muscles, tendons, fascia and ligaments
- Learned triggers
- S R
- UCS UCR
- (Si + UCS)n Si Ri
- Intention
- Cognitive Control
Issue 3: Cues Used by the Nervous System to Control Movements
- Sensorimotor, mnemonic, and cognitive
- Example of the language system
Issue 4: Levels of Analysis
Level I:
- Emotion/Cognition
- Grapho-Motor System
- Motor-Speech System
- Auditory System
- Visual System
- Writing Speaking Hearing Reading
- Formulation
Language System:
- Working
- Memory
- Comprehension
- Serial model of motor control
- Computations required by serial model of motor control
- Feed-forward / feedback control
Issue 5: What is Computed and How?
Serial Model of Motor Control:
- Definitions
Kinematics:
- Change in position, for example, of limb over time. Could specify in terms of timedependent changes in joint angle.
Dynamics:
- Patterns of forces associated with the movements – joint torques.
- Assume you visually specify object position with respect to the body. To reach it, is then necessary to compute:
- Inverse kinematics: Compute the joint angle to get the finger to the target.
- Inverse dynamics: Given desired target position and kinematics, compute the forces needed to get the arm there.
- Computations required by serial model of motor control
- Feed-forward / feedback control
- E.g. touch X
- Eye in head
- Head on trunk
- Arm on trunk
- Arm joints / hand
- Egocentric
- Center scan
- Retinotopic
- Object centered?
Issue 6: Spatial Coordinate Frames Used for Sensorimotor Control
- Cerebral cortex
- Basal ganglia
- Cerebellum
- Brainstem
- Spinal cord
Issue 7: What Brain Regions are Involved in Motor Control?
- Stimulation
- Ablation / human clinicopath correlations
- Anatomy of connections
- Animal studies
- Reflexes
- Locomotion
- Behavioral patterns
- Gene-based studies
Issue 8: What Techniques are Used to Study Motor Control?
- Degrees of freedom problem
- Serial order of behavior
- Sensory / perceptual motor transform
- Motor equivalence
- Motor learning and plasticity
- Higher order control: cognition, motivation
- Computational models
Issue 9: Challenges for the Field
- 3DF
Degrees of Freedom Problem:
- 1DF
- DF
- DF 3DF at wrist
- 2DF
Degrees of Freedom Problem:
- Plan ahead
- Minimize jerk (da/dt)
- Built-in synchronies (e.g. “associated movements”)
- “Too complicated so can’t be done so we don’t do it” (Alexander + Crutcher)
- End point calculations vs. trajectory calculations
Possible Solutions to the Degrees of Freedom Problem:
- Speech
- Complex actions
- Milk in cupboard
- Cereal box in fridge
- Co-articulation
- Fingers move ahead – not in order of letters to be typed – as in “an epic”
- Modularity?
- Chunking?
Examples of Serial Order of Behavior:
- Source: Rosenbaum, D.A. (1991) Human Motor Control. New York, Academic, p. 16.
Co-articulation
- Source: Rosenbaum, D.A. (1991) Human Motor Control. New York, Academic, p. 6.
Sample Lecture Outline for Lecture 5: Motor Cortex
Primary Motor Cortex
- M1 has body map
- But controversy about maps is coming…
- Wilder Penfield experiments
- Microelectrode stimulation-recording experiments (Asanuma)
- Multiple motor areas in addition to M1
Role of the Pyramidal Track
- Anatomy of the Pyramidal Track (origin and destination)
- Stroke
- Privileged access to motor neurons in spinal cord
- Kuypers’ experiments (transsection of pyramidal tract vs.. reticular spinal tracts)
- Paradox of one PT neuron innervates motor neurons for multiple motor neuronal pools
What is Coded by M1 Neurons?
- Breakthrough with experimental protocol introduced by Edward Everets (1960’s)
- M1 neurons code for load - early story
- M1 neurons have a population code for direction of movement (Georgopoulos experiments)
- Population vectors
M1 Map/Representation is Highly Plastic.
- Laboratory evidence (Nudo)
- Evidence from human scans
What M1 Neurons Respond to is not Simply Related to Corresponding Muscle EMG Activity.
- Different conditions producing EMG activity in a single muscle may not all induce spike activity in a motor neuron connected to that muscle.
The Hypothesis that Different Motor Cortical Areas Specialize in Different Aspects of Movement.
- “Simple” movements
- Sequential movements
- Imagined movements
