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Perception & Motor Complete Summary - 3.6 Neuropsychology
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This summary contains all content from week 1 of the 2024 Neuropsychology exam. Grade received: 8.8!
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3.5 NeuropsychologyWeek 1
Perception & Motor
System
,Kolb & Wishaw (2015) → Chapter 9: Organization of
the Motor System
The neocortex: initiating movement
● General
○ Four neocortical regions produce skilled
movements
■ Posterior cortex → specifies movement
goals, sends sensory information from
vision, touch hearing to frontal regions
(multiple routes)
● Direct routes prompt primary
motor cortex to execute
automatic movements
● Conscious controlled
movements requires indirect routes through temporal & frontal
cortex
■ Prefrontal cortex (PFC) → generates plans for movements, passes
along to premotor & motor cortex
■ Premotor cortex → anterior to M1, recognizes others movements and
selects similar or different areas
■ Primary motor cortex (M1) → more elementary movements than the
premotor lexicon (eg hand & mouth movements)
● Mapping the motor cortex using electrical stimulation
○ Most movements induced by experiments were triggered by stimulation of
precentral gyrus (M1), also dorsal premotor cortex (supplementary)
○ Homunculus (Penfield) → each hemisphere has a mirror representation, also in
supplementary motor cortex, upside down relative to actual body
■ Relative sizes of body parts represented very different to actual sizes →
large hands, thumb, lips, tongue and small trunk, arms, legs
■ Linked to precision of certain body parts
● Multiple representations in the motor cortex
○ General
■ Later experiments showed that there may be as many as 10 homunculi →
better electrical stimulation
○ Natural movement categories
■ Ethology → scientific study of animal behavior under natural conditions
■ Movement with extra load is compensated in the brain
■ Movements evoked by stimulation lack the flexibility of typical movements
■ Many cortical maps exist → each region represents three types of
organization
● Body part to be moved
● Spatial location to which the movement is directed
, ● Movement’s function
■ Certain movement types cluster together relative to the part of the motor
cortex from which they are elicited → flexible cortical map (Graziano)
■ Similarities of Penfield & Graziano
● Whole body movements → dorsal premotor cortex
● Hand movements (reaching) → more ventral premotor cortex
● Hand movements to mouth → most ventral part of premotor cortex
● Hand grasping movements around the body → M1 (more ventral if
movement is directed to mouth)
● General → whole body movements more in premotor, discrete
movements more M1
○ Visual-parietal-motor connections
■ Parietal cortex stimulation can also evoke movements → also
homunculus
■ Stepping movements → dorsal parietal regions
■ Reaching movements → medial parietal regions
■ Hand and mouth movements → more ventral parietal regions
■ Dense anatomical connections
■ Visual cortex provides information for motor cortex to instruct the action
for movement (identifying location and shape of target) → parietal
regions represent sensory receptors that will be activated when the
object is contacted (reach and grasp)
● There is a dual pathway for the grasping action (parietal to motor)
● The movement lexicon
○ Graziano's mapping studies support the view that there is a lexicon of
movements in the cortex → different people perform similar skilled movements
○ Spontaneous use of different grips from babies to children → not learned,
encoded neural patterns
○ Lesions in thumb part of homunculus leads to weaker hand abilities → evidence
for maps, impairment is not in the hand itself but the in the coordination of action
■ Hard to make complementary movements when there are lesions on
premotor cortex (more important in making whole body movements than
M1)
○ Large part of learning to move entails learning how to use preorganized
movement patterns to achieve both skill and strength → blend together motor
reflexes
○ Neurons in M1 are active not only in the planning but also in the execution of the
movements → increased firing rate for increased force
■ Motor cortex specifies movement direction
○ Single cell recordings show that movements are not produced by actions of a
single cell but by the coordinated activity of populations of cells
■ Single cells have a “preferred” direction which increases activation
● Mirroring movement
○ Actions are learned, specific, dependent upon interactions with others
, ○ Single cells discharge not only when an action is made but also when the
monkey sees other monkeys making the same movement
○ Mirror system neurons → encode the goal of an action, do not respond well to
pictures or videos of movements, sometimes respond only to particular
movements, some are more broad, can fill in parts of the movements that are not
seen
○ Mirror neuron system
■ Core mirror neuron system → responds to transitive actions, Broca’s
area
■ Distributed mirror neuron system → can respond to intransitive actions
(no goal is present)
○ Flexible properties of the mirror system → able to understand actions of others,
related to higher cognitive functions, cognitive understanding of an action is
embodied in the neural systems that produce that action
○ Likely important for self-awareness, social awareness, awareness of intention &
action in others, verbal & gestural language
■ May be related to empathy, autism, seeing others points of view
■ Related to human abilities of mimicry and representing actions using
language
The brainstem: motor control
● General
○ 26 pathways from brain to spinal cord → send information about posture &
balance, control autonomic nervous system
○ Motor neurons are the final common path for motor functions, those produced in
brainstem often full body movements
○ Able to elicit almost every innate movement that an animal of that species
might make in the brain stem with electrodes → increased vigor with increased
stimulation
○ Other brainstem functions → controlling movements used in eating, drinking,
sexual behavior, posture, ability to stand upright, make coordinated movements
of limbs
● The basal ganglia and movement force
○ Basal ganglia → subcortical nuclei in
forebrain, connect sensory regions of the
neocortex with motor cortex
○ Caudate putamen → large cluster of nuclei
located beneath frontal cortex, tail into
temporal lobe which ends in the amygdala
○ Basal ganglia receive input from
■ All areas of neocortex & limbic
cortex, motor cortex
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