CDL PS3002
Lecture 3
Motor control
Serial order
Reading
–Gazzaniga, Ivry and Mangun, Cognitive Neuroscience, Chapter 11
–Kolb and Whishaw, Fundamentals of Human Neuropsychology, Chapter 9
–Bruce, Green and Georgeson, Visual Perception, Chapter 10, pp. 311-314
Overview
• behaviour = series of actions
– components of actions are performed one after another
e.g. speech production, reaching, piano playing
• behaviourism
serial order = chains of responses
– each component acts as a discriminative stimulus
for the following one
• Lashley (1951)
action sequences cannot be explained in terms of chains of responses
- Motor sequences
- Computational problems in motor control
- Hierarchical control
- Role of sensory feedback
– different ordering of the same component units
e.g.
gait of a horse (trotting, pacing)
phonemes in a word (tire-rite)
a mechanism must be responsible for ordering independently
from association between single elements
– spoonerism (displacement of initial phonemes)
anticipation errors
e.g. Our queer old dean - Our dear old queen
the speaker skips adjacent elements which should be linked by association
– speed
e.g. professional piano players
elements separated by less than 100 ms - sensory feedback needs 200 ms
– co-articulation
e.g. type-writing (Genter, Grudin & Conway, 1980)
Degrees of freedom
df = number of different ways in which a movement can be performed
– direction
– degree of muscle contraction
– motor neurone discharge
e.g. movement of the arm
a
n
space
e
p
i
c
onset of movement (milliseconds)
Cortical motor areas
Sub-cortical structures involved in motor control
Central sulcus
Motor
Sensory
Cerebellum
correction of errors
Area 4 (M1)
primary motor cortex
Area 6
medial surface
supplementary motor area
lateral surface
pre-motor cortex
Area 8
frontal eye fields
Prefrontal cortex
Basal ganglia
force
High order plans independent from particular muscular systems
Hierarchical control
e.g. written using
• Pathways from SMA to MC to Spinal cord
1 1-1 6
dominant hand
wrist
Premotor (PM) Cortex
Supplementary Motor (SMA) Cortex
Motor Cortex
Cerebellum
non-dominant hand
mouth
Basal ganglia
Brain Stem
foot
W . W . N orto n
Pyramidal
tract
Extra pyramidal
tract
Spinal Cord
Motor pathways
Output
to muscles
Input
from muscles
Cognitive model (McKay, 1987)
1) representation of action goal
2) selection of particular action from a set
of appropriate actions (lexical level)
3) translate selected action in pattern of muscular activation
Relative role of sensory feedback
•Autonomy of lower levels
spinal reflex arcs
Brown (1911)
resection of spinal cord and dorsal root
rhythmic movements
central pattern generators
independence from sensory feedback
1 1-0 3
Taub and Berman (1968)
recovery of mobility in deafferented animals
W . W . N orto n
Sherrington (1947)
spinal animals
emphasis on sensory feedback
Neuropathy
loss of sensory fibres
spared motor fibres
patient insensitive to pain
patient performs coordinated movements
Spect- Pet studies (e.g. Roland 1993)
Simple movement
controlateral primary motor cortex
Internal and external guidance of movement
Complex sequences
Area 6 (SMA + PM)
Complex sequence
controlateral - prefrontal - basal ganglia
and bilateral PM and SMA
SMA (fibres from prefrontal cortex and basal ganglia)
internally guided (production of whole learned sequence)
PM (fibres from - parietal cortex- cerebellum)
externally guided (reproduction of sequence step by step)
Imagined complex sequence
bilateral SMA
Electrophysiological studies
Internal and external guidance of movement
S1 signals that a “go” signal (S2) will follow, they have then execute a response (R)
Readiness (bereitschaft) potential appears in time interval between S1 and S2
1 1-3 6
Complex sequences
Area 6 (SMA + PM)
S1
S2
R
Associated with planning of single movements
SMA (fibres from prefrontal cortex and basal ganglia)
internally guided (production of whole learned sequence)
PM (fibres from - parietal cortex- cerebellum)
externally guided (reproduction of sequence step by step)
Mushiake et al., 1992
W . W . N orto n
single cell recording before 3-step sequence execution
tone (S1) signals which type of sequence (externally-internally guided) pertains
• Two components recorded in cells of over :
–PMC - externally cued sequences
e.g. repeat back a visually presented sequence
–SMA - internally cued sequences
e.g. execute a practised sequence
Goldberg (1985)
anatomical basis of control of internally and externally cued
sequences
Pre-motor area
input from parietal cortex and cerebellum
integration of multi-sensory information
SMA
input from prefrontal cortex (internal goals)
and basal ganglia
(initiation of action by
regulating inhibition)
Summary and conclusions
• Serial order
• Degrees of freedom
• Hierarchical organisation
cognitive models
motor pathways
- Frontal areas plan
- Motor areas command the movement
- Spinal cord carries information to periphery
- Motor neurons carry the message to the muscles
• Internally and external guided action sequences