Study Materials

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:

  1. Plan ahead
  2. Minimize jerk (da/dt)
  3. Built-in synchronies (e.g. “associated movements”)
  4. “Too complicated so can’t be done so we don’t do it” (Alexander + Crutcher)
  5. 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