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Midterm

PSYC 251 Midterm: Psychology 251 - midterm 2 typed notes
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Department
Psychology
Course Code
PSYC 251
Professor
Adam Krawitz

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Psychology 251 - Exam 2
Topic 3: Perception - Bottom-up and Top-down influences
- Bottom-up - stimulus driven, feedforward connections. Depends on the proximal stimulus and
genetic “hard-wiring” of sensory systems
Involves low-level-processing intermediate high-level processing
to determine what something is based on information given form the
stimulus
- Top-down - Driven by goals and expectations, feedback connections.
Depends on past experience, internal state, and environmental context.
We perceive the world in a way that is “most likely’ based on our past
experiences
- Perception depends on both types of processing!
- Interactive activation theory: McClelland and Rumelhart - model of
letter and word perception; integrates bottom-up and top-down processes.
Knowledge of a word helps interpret what letters are in it (rather than the
other way around).
Features letters words = bottom-up processing uses feature
detectors; features excite or inhibit letters, letters compete with other
letters and excite or inhibit words.
Words letters features = tyop-down processing; words compete
with other words and excite letters.
Word superiority effect - bottom-up and top-down processes are necessary to explain
perception.
Topic 4: Action
Action is a change in the environment.
- Somatic - skeletal muscle - moves limbs
- Autonomic - controlled by the brain. Includes smooth muscles (blood pressure, digestion), cardiac
muscles (heartbeat), endocrine glands (secrete hormones), and exocrine glands (sweat, saliva).
- Internal actions - CNS: can the brain/mind take actions on itself?
Update memory, switch tasks, etc. Very similar to brain functions used to take physical actions.
PROBLEM: How do we effect change in the world?
IMPORTANCE: Actions are necessary to achieve goals (eating, drinking, reproducing, etc)
CHALLENGE: Inverse problem - determining what actions to take in order to achieve goals. (we work
backwards to figure out what we need to do to get there).
Motor System
- Motor control is hierarchical
- Motor equivalence - our movements are consistent with
abstract motor plans (motor plan is not represented as a
movement of specific muscles, but rather the general
movement in space)
Our writing appears similar (apart from quality) with
each body part used to write (hand, foot, teeth, etc.)
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- Inverse model - current position and desired
position - what sequence of motor commands is
needed to reach a desired position?
Used to create motor plans
- Forward model - current position and motor
commands predict the position that will be ended
in.
Used to evaluate motor plans and/or action
Efferent copy - internal copy of a motor
command. Compare actual behaviour and
predicted behaviour to make sure/know if
actual outcome matched predicted behaviour.
- Feedforward control - motor command to muscle;
fast but less accurate (inverse)
- Feedback control - motor command sent to muscle;
actual outcome compared to the desired state.
Adjustments made based on errors (forward)
Motor planning - PREMOTOR CORTEX
- Planning of voluntary actions begins at a conceptual
level based on goals
Quench thirst (goal) drink from cup (conceptual)
pick up cup (effector) activate muscles in arm
(implementation)
- Premotor cortex is involved in selecting goals and
planning actions at a conceptual level, particularly
when plans are driven by external stimuli.
Readiness potential - planning in the premotor cortex occurs before voluntary movement.
Precedes action sometimes ~1 sec before.
Planning for multiple alternative actions:
o Task: Reach for target with arm
o Spatial cues: cued with two possible targets (red and blue); different action for each target
o Memory period: cues are removed, prepare for both actions
o Colour cue: cued with actual target, now prepares for single action
o Go signal: initiate action. (most activity for the chosen action
plan at this point.)
- Mirror neurons - some neurons in the premotor cortex represent
actions at a conceptual level.
Performing or observing an action, ex breaking a peanut.
Whether breaking a peanut or watching someone else do it, the
neuron fires. Hearing not seeing/seeing not hearing - still fires
(So not a visual, perceptual, or auditory neuron).
Consistent with the idea that these neurons represent action
concepts, not the specific muscle movement.
Motor sequencing - SUPPLEMENTARY CORTEX
- This is adjacent to the premotor cortex. Involved in selecting goals and planning actions at a
conceptual level.
- Involved in selecting goals and planning actions at a conceptual level, particularly when plans involve
internally generated sequences of actions (like tying shoelaces, playing a song, performing a dance).
- Recording from SMA neurons during different movement sequences; using peristimulus time
histogram - each little mark when a neuron fires (action potential); each row is a trial. Pick event (one
action in a sequence) to line data up on.
One neuron fires in anticipation of a particular sequence.
One neuron fires before a particular action in a particular sequence
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One neuron fires before the third action in every sequence
- Behavioural performance with SMA deactivated by muscimol injection
(GABA agonist)
Injection of muscimal temporarily lesions supplementary motor
areas - could perform cued sequence just fine, but could not
perform learn sequence with the SMA (Supplementary motor area)
deactivated.
Circle = cue for specific action
Square = cue for learned action
Triangle = action
Blue = correct, red = error
Motor representation - MOTOR
CORTEX/SUPERIOR COLLICULUS
- Motor cortex represesnts directional
movements of body parts, not specific
actions.
- Signals from the motor cortex traced directly to lower motor neurons and
lower circuit neurons in the brainstem and spinal cord.
- spinal cord (lower motor neuron) medulla (pyramidal decussation)
pons midbrain (upper motor neuron) primary motor cortex
(precentral gyrus)
- Topography and cortical magnification are the same for the motor cortex
as in the somatosensory cortex (both side by side strips on the brain - one
receives input, one controls movement output)
- Motor homunculus - more cortex to hand control than in the somatosensory homunculus, less arm
and leg motor control.
- Motor cortex activity is correlated with movement
direction
Task: move joystick from center to a peripheral
target. Recordings from a single motor cortex
neuron show firing increases with direction of
movement; most firing in the preferred direction of
movement. Ex: if neuron prefers downward
movement, it fires the most when joystick is moved
from center to down.
Response rate as a function of directino of
movement can be summarized by a tuning curve;
tuning curves can be used to create a population
vector
Each vector represents the direction of movement
that a neuron prefers; length = how much that
neuron fires. Add to get the vector between the two which is the predicted direction of movement =
population vector. This accurately represents actual movement direction.
So direction of the population vector will predict the
direction of a forthcoming movement.
Motor targets - INTRAPARIETAL CORTEX
- Intraparietal sulcus (IP) helps to guide movements to
the correct location, orientation, and configuration.
Lateral (LIP) represents space for eye movements -
retinal-centered receptive fields. Location is relative to
where the eyes are looking.
Ventral (VIP) represents space for facial movements 0
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Description
Psychology 251 Exam 2 Topic 3: Perception Bottomup and Topdown influences Bottomup stimulus driven, feedforward connections. Depends on the proximal stimulus and genetic hardwiring of sensory systems Involves lowlevelprocessing intermediate highlevel processing to determine what something is based on information given form the stimulus Topdown Driven by goals and expectations, feedback connections. Depends on past experience, internal state, and environmental context. We perceive the world in a way that is most likely based on our past experiences Perception depends on both types of processing! Interactive activation theory: McClelland and Rumelhart model of letter and word perception; integrates bottomup and topdown processes. Knowledge of a word helps interpret what letters are in it (rather than the other way around). Features letters words = bottomup processing uses feature detectors; features excite or inhibit letters, letters compete with other letters and excite or inhibit words. Words letters features = tyopdown processing; words compete with other words and excite letters. Word superiority effect bottomup and topdown processes are necessary to explain perception. Topic 4: Action Action is a change in the environment. Somatic skeletal muscle moves limbs Autonomic controlled by the brain. Includes smooth muscles (blood pressure, digestion), cardiac muscles (heartbeat), endocrine glands (secrete hormones), and exocrine glands (sweat, saliva). Internal actions CNS: can the brainmind take actions on itself? Update memory, switch tasks, etc. Very similar to brain functions used to take physical actions. PROBLEM: How do we effect change in the world? IMPORTANCE: Actions are necessary to achieve goals (eating, drinking, reproducing, etc) CHALLENGE: Inverse problem determining what actions to take in order to achieve goals. (we work backwards to figure out what we need to do to get there). Motor System Motor control is hierarchical Motor equivalence our movements are consistent with abstract motor plans (motor plan is not represented as a movement of specific muscles, but rather the general movement in space) Our writing appears similar (apart from quality) with each body part used to write (hand, foot, teeth, etc.) Inverse model current position and desired position what sequence of motor commands is needed to reach a desired position? Used to create motor plans Forward model current position and motor commands predict the position that will be ended in. Used to evaluate motor plans andor action Efferent copy internal copy of a motor command. Compare actual behaviour and predicted behaviour to make sureknow if actual outcome matched predicted behaviour. Feedforward control motor command to muscle; fast but less accurate (inverse) Feedback control motor command sent to muscle; actual outcome compared to the desired state. Adjustments made based on errors (forward) Motor planning PREMOTOR CORTEX Planning of voluntary actions begins at a conceptual level based on goals Quench thirst (goal) drink from cup (conceptual) pick up cup (effector) activate muscles in arm (implementation) Premotor cortex is involved in selecting goals and planning actions at a conceptual level, particularly when plans are driven by external stimuli. Readiness potential planning in the premotor cortex occurs before voluntary movement. Precedes action sometimes ~1 sec before. Planning for multiple alternative actions: o Task: Reach for target with arm o Spatial cues: cued with two possible targets (red and blue); different action for each target o Memory period: cues are removed, prepare for both actions o Colour cue: cued with actual target, now prepares for single action o Go signal: initiate action. (most activity for the chosen action plan at this point.) Mirror neurons some neurons in the premotor cortex represent actions at a conceptual level. Performing or observing an action, ex breaking a peanut. Whether breaking a peanut or watching someone else do it, the neuron fires. Hearing not seeingseeing not hearing still fires (So not a visual, perceptual, or auditory neuron). Consistent with the idea that these neurons represent action concepts, not the specific muscle movement. Motor sequencing SUPPLEMENTARY CORTEX This is adjacent to the premotor cortex. Involved in selecting goals and planning actions at a conceptual level. Involved in selecting goals and planning actions at a conceptual level, particularly when plans involve internally generated sequences of actions (like tying shoelaces, playing a song, performing a dance). Recording from SMA neurons during different movement sequences; using peristimulus time histogram each little mark when a neuron fires (action potential); each row is a trial. Pick event (one action in a sequence) to line data up on. One neuron fires in anticipation of a particular sequence. One neuron fires before a particular action in a particular sequence
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