• Chemical (i.e., NT)
• Sometimes electrical

• – 70 mV

• EPSP from many dendrites is summed at the spike-triggering zone of the axon hillock
• Action potential is initiated if summation of EPSPs causes depolarization
• Action potential regenerates along the axon at Nodes of Ranvier

• –55 mV
• Onset of action potential

1. Calcium influx
2. Synaptic vesicles are mobilized
3. Synaptic vesicles fuse with synaptic membrane and are released
4. Synaptic vesicles are recycled

• Reaction time
• Accuracy

• Posner (1986)
• Participants asked if letters were the same or different
• Participants were fastest at identifying similiarity when the letters were identical (e.g., AA v. Aa), & both vowels
• Slowest to react when both stimuli were consonants

• Reicher (1969)
• Participants asked whether a target letter was in among a group of letters
• Participants most accurate when the stimulus was a word (vs. random string of letters)

• STROOP task response latencies disappear when the participant responds via button press rather than oral report
• Imaging results can differ depending on the type of computer used for data preparation

Psychopharmacological method:

Definition, use in research

• Manipulating a NT to observe the effect of the NT system (including projections and structures) on cognition
• What is the role of NT_x in process_x?
• DV: cognitive functioning

Psychopharmacological method:

Example of study

• Ketamine (NDMA receptor antagonist) administered prior to a forced-swim task
• Rats spent less time immobile
• Interpretation: NDMA involved in depressive behaviours

Psychopharmacological method:

Benefits and Limitations

Benefits

• Clinical application
• Site specificity
• Elucidates acute and chronic role of NTs in cognition

Limitations

• Selectivity of receptor subtypes and varying functions (e.g., D1 vs. D2)
• How is the site involved?

In vivo single-unit recordings:

 Definition, use in research

• Measures neuron's electrically charged membrane to detect action potentials
• What are the functional circuits between brain regions that mediate cognition?
• DV: spike train

In vivo single-unit recordings:

 Example of study

• Used in monkeys to identify topographic setup of the visual system and feature detection cells
• Researchers able to identify receptive fields via cell-specific responding

In vivo single-unit recordings:

Benefits and Limitations

Benefits

• Temporal resolution (recording in real time)
• Spatial resolution
• Electrode placement can be permanent

Limitations

• Small scale
• Correlational
• Fails to account for temporal characteristics of firing

• Action potentials per second
• "Spike" means action potential

• Infer functional relationship if spikes are temporally synchronized

• Constituative: gene is removed from the CNS.
• Conditional: gene is removed under certain conditions
• Temporal
• Regional
• Cell/neuronal type
• Combination of above conditions

Gene knock-out approach:

Description, use in research

• Either constitutive or conditional removal of a gene (typically coding for a NT receptor type), such that changes in functioning can be observed
• What is the effect of gene_x on cognition? What cognitive changes occur when the gene is excised?

Gene knock-out approach:

Example of study

• Dopamine D1 receptors excised from mice
• Decrease in dopamine self-administration

Gene knock-out approach:

Benefits and Limitations

Benefits

• Target specificity
• In conditional KO, temporal, target, and/or regional specificity
• Inducible

Limitations

• Permanent
• Upregulation/adaptation of other systems
• In conditional KO, possibility of over excision (beyond the specified condition)

Gene knock-in approach:

Description, use in research

• Exogenous gene is spliced into the DNA to observe the effect on cognitive functioning
• How does the addition of gene_x affect cognitive functioning?

Gene knock-in approach:

Example of study

• Immunofluorescence to mark and visualize neurons and projections
• Optogenetics to control neuronal firing

• Inhibition of prelimbic cortex-NAcc pathway decreases self-administration of cocaine in rats

Gene knock-in approach:

Benefits and Limitations of optogenetics

Benefits

• Causal -- manipulation of behaviour
• Real time
• Control and experimental conditions in the same specimen

Limitations

• Process may affect other systems (knock-in of large molecules)

Gene knock-in approach:

Benefits and Limitations of immunofluorescence

Benefits

• Highly specific visualization of neural connectivity (e.g., can differentiate axon from dendrite)
• Temporal selectivity
• Tissue selectivity

Limitations

• Process may affect other systems (knock-in of large molecules)

Disrupted neural functioning:

Methods

• Pharmacology
• Genetic manipulation
• Lesions

• Selective lesions in animal models
• Naturalistic observations after TBI or disease
• Artificial lesions (e.g., TMS)

Transcranial Magnetic Stimulation:

Description, use in research

• Temporarily disrupts neural functioning through magnetic field
• What is the role of region_x in cognitive functioning?

Transcranial Magnetic Stimulation:

Example of study

• TMS used to differentiate regions involved in language perception
• TMS to the rostral inferior frontal gryus disrupted semantic identification
• TMS to the caudal inferior frontal gyris disrupted phonological identification

• To what extent were neurons in surrounding regions disrupted (i.e., spatial selectivity)
• What are the downstream effects of the neural disruption?
• What was the control condition (sham TMS or waitlist?)

Transcranial Magnetic Stimulation:

Benefits and Limitations

Benefits

• Clinical utility
• Repeated applications for treatment of mood disorders, Parkinsons, OCD
• Reversible
• Non-invasive

Limitations

• Limited to cortical areas
• Poor special specificity
• Control groups (waitlists v. sham)

• Global versus specific deficits
• Were the observed deficits due to a disruption in task-specific functioning, or due to a global deficit that disrupted constituent skills?
• Control group with brain damage
• Different tasks to support assumptions

• CT
• MRI
• DTI

• EEG
• ECoG
• MEG
• PET
• fMRI

Computed Tomography:

Description, use in research

• X-rays are absorbed by the tissue; higher density tissue absorbs more rays and appears white
• Structural image of the brain
• Diagnostic uses (brain damage)

Computed Tomography:

Benefits and Limitations

Benefits

• Diagnostic use (brain damage)
• Non-invasive
• Temporal resolution 
• Quick, cheap (utility in emergencies)

Limitations

• Poor spatial resolution
• Poor contrast between grey and white matter
• X-ray radiation
• Only elucidates structure

Magnetic Resonance Imaging:

Description, use in research

• Structural 3D image of the brain (density of hydrogen atoms) via measuring energy released by H⁺ protons after exposure to magnetic force
• MRI's magnetic force aligns protons. Radiowaves force protons into predictable orientations. Once the radiowaves are off, the protons release energy as they return to the orientation of the magnetic field.

Magnetic Resonance Imaging:

Benefits and Limitations

Benefits

• Spatial resolution
• Best among structural imaging techniques
• Contrast between grey and white matter

Limitations

• Stressful
• Elucidates structure only

Diffusion Tensor Imaging:

Description, use in research

• Same method as MRI
• Visualization of axon tracts/structure of projections provides evidence for functional connectivity
• DV: water/water flow in axons of white matter tracts

Diffusion Tensor Imaging:

Example of study

• White matter connectivity in MS
• MS patients trained to improve balance showed decrease in white matter pathology

Diffusion Tensor Imaging:

Benefits and Limitations

Benefits

• Structural connectivity

Limitations

• Doesn't elucidate functional connectivity

Electroencephalography:

Description, use in research

• Measures summed action potentials via electrical potential and frequency of pyramidal cell activity
• Activity in response to stimuli

• Electrical potential: brain activity; voltage/amplitude/power
• Frequency: rhythm of activity; Hz

• Event-related potential (ERP)
• Time-frequency analysis

Event-related potential (ERP):

Description, use in research

• Method of examining EEG data
• Time-locked activity: examination of activity immediately following stimulus presentation or behavioural response
• How does EEG signal change as a function of mental state or in response to stimuli?

Event-related potential (ERP):

DV

• Polarity (positive or negative) at a time after stimulus presentation
• e.g., P300

Electroencephalography:

Time frequency analysis

• Temporal plot of neural activity across time as a function of frequency
• (amplitude by time) by frequency
• Can be plotted topographically

Electroencephalography:

Example of study

• Semantic processing of words versus music
• Participants' EEG response (i.e., N400) indicated that the mismatched descriptor and musical mood (e.g., sad --> "Shake it off") was unexpected; same response as word presentations without music

Electroencephalography:

Benefits and Limitations

Benefits

• Clinical/diagnostic utility
• Temporal resolution of ERPs (ms)
• Direct measure of neural activity

Limitations

• Limited to cortical areas
• Poor spatial resolution (EEG and ERP)
• Need lots of data to overcome noise

Electrocortogram:

Description, uses in research

• Similar to EEG
• Electrodes are placed on the surface of the brain
• Limited to pre-surgery

Magnetoencephalography:

Description, use in research

• Neural activity (electrical potential) is measured using magnetic fields
• Magnetic sensors measure magnetic fields associated with neurons' electric currents
• Used in pre-surgery and research (time course of activity)

Magnetoencephalography:

Benefits and Limitations

Benefits

• Temporal resoultion (same as EEG)
• Spatial resolution
• Direct measure of neural activity

Limitations

• Less able to detect information from cortical gyrus
• Sensitive to flow parallel to the cell, moving away from electrode
• Usually limited to pre-surgery

Positron Emission Tomography:

Description, use in research

• Neural activity inferred from tracer accumulation in blood flow, oxygen flow, and sugar metabolism
• Radio-labeled oxygen or glucose accumulate because they are not metabolized
• Functional image without structural image (former is superimposed onto image of latter)
  
  

Positron Emission Tomography:

Benefits and Limitations

Benefits

• Clinical/diagnostic utility (some tracers serve as biomarkers)
• Cortical and subcortical analyses
• Spatial resolution

Limitations

• Invasive
• Poor temporal resolution
• Indirect measure of neural activity

Functional magnetic resonance imaging:

Description

• Measures oxygen levels in blood (BOLD: blood-oxygen level dependent)
• Action potentials deplete oxygen from area; to return to homeostasis, there is an influx of oxygen-rich blood to the area 6-10 sec after an action potential. This is what is measured.

• Spatial region in the brain

• Region of interest

• Fitting fMRI images to a standarized brain atlas
• Can distort image and impact findings

Functional magnetic resonance imaging:

Methodological and theoretical considerations

• A-priori selection of voxels in ROI
• Extent of distortion after smoothing
• Level of activation necessary to meet threshold is defined by the experimenter
• Activation can be inhibition or excitation

• Subtraction method
• Target activity minus baseline, averaged across the group gives picture of activation due to the activity

Functional magnetic resonance imaging:

Benefits and Limitations

Benefits

• Okay spatial resolution (not as good as structural MRI)
• Function of cognitive processing
• Clinical/diagnostic utility
• Research design flexibility

Limitations

• Correlational
• Indirect measure of neural activity
• Difficult to establish functional pathways
• Poor temporal resolution
• Stressful
• Noise

• object of perception

• Computers and equipment can make a difference
• Small sample sizes
• Correlational
• Glia send electrical signals, although discussion centres around neuronal potentials
• Excitatory versus inhibitory signals
• Voxels may span functional areas  

• Ganglion cells
• Projects to the lateral geniculate nucleus
• Functionally distinct pathways (magnocellular and parvocellular cells)
• Bipolar cells and amacrine cells
• Information from photoreceptors
• Early processing
• Photoreceptors
• Light travels through these layers in the order listed. Information is sent back through the layers and out through the optic nerve

• Temporal hemiretina project ipsilaterally
• Nasal hemiretina project contralaterally

• Retina, lateral geniculate nucleus, V1
• Retina, superior colliculus, pulvinar nuclei, V1

• M cells
• Information from rods, concerning movement
• Project to layers 1 and 2 of LGN
• Importance: LGN receives all information but separates by function

• P cells
• Information from cones
• Projects to LGN layers 3-6
• Importance: LGN receives all information but separates by function

• name for pathway: LGN projects to V1

• Primary visual cortex

• Primary visual cortex

• Area in the visual field to which a neuron preferentially responds to changes in light

• Centre/surround

• Contrast
• Edges that comprise environment
• LGN doesn't code for orientation

• Contrast: LGN
• Orientation: V1

• Ocular dominance columns
• Orientation columns
• Layers of cells with similar spatial receptive fields but that respond preferentially to colour, size, eye, etc.

• Layer of cells that respond preferentially to information from one eye

• Regions outside of V1 that are involved in visual processing

• Different areas elaborate on the various features of input
• Analytical
• Features are separated functionally and processed by specialized areas

• Extrastriate region that responds to motion in the receptive field
• 2 attributes are needed to activate receptive fields (movement on x and y planes)
• Located in occipital lobe near the temporo-parietal junction

• Present various stimuli (controlling for illumination and contrast) both moving and stationary
• Use subtractive method (fMRI) to identify voxels that are active for motion but not for the stationary stimuli

• TMS to disrupt V5 reduces ability to detect direction of stimulus movement

• fMRI
• Moving stimulus: observe BOLD activation as it moves to various parts of the receptive field

• Visual percepts formed in extrastriate regions
• Elaboration of lower-order V1 perception
• Tested with optical illusions
• What regions are active when there are illusory stimuli?
• What regions are inactive when there are hidden stimuli?
• Illusory movement only activates V5, not V1 (whereas actual movement activates both)

• Colour perception
• Form perception

• Deficits in colour vision with retained ability to perceive depth and form

• Colour perception occurs in V4 area of the anterior visual cortex
• Patient with lesion in the right hemisphere near the temporo-occipital border could not name or match hues presented in the left visual field
• Retained ability in the right visual field, as lesion was limited to the right hemisphere

• Deficits in motion perception (inability to perceive fluidity of movement)

• Bilateral damage to V5

• Sensory integration
• Learned ability
• Brain weighs the reliability of each stimulus
• e.g., McGurk effect the brain prioritizes visual over auditory cues

• Faster and more holistic processing

• Lower order regions
• Superior colliculus
• Also, primary visual cortex

• Phantom limb pain
• If the brain "sees" the hand moving, the evidence is deemed reliable enough to reduce pain
• Visual system dominance overrides maladaptive pathways

• McGurk effect
• Phantom limb
• Synesthesia

• Stimuli must converge in space and time
• i.e, presented with one another

• Abnormal activity in V4
• Connections between sensory regions

• Violinists have greater MEG activity in right hemisphere (corresponding with left hand that controls the strings)
• Level of activity correlates with first age of music training

• Participants with normal vision were blindfolded for 5 days
• By day 5, blindfolded participants had increased tactile sensitivity
• Tactile tasks were associated with activation in occipital lobe
• Lobe's resources re-allocated to touch
• Effects diminished within 20 hours of blindfold removal

• Transformation of 2D image to 3D representation
• Recognition of what and where an object is

• Perception is processing whereas recognition is mental representation
• Perception and recognition aren't the same
• We perceive unified objects
• Perception is flexible and robust
• Product of perception is connected to memory and learning
• Active control

• Dorsal stream: where/how pathway running along the superior fasciculus (occipitoparietal)
• Impaired with lesions to parietal lobe

• Ventral stream: what pathway running along the inferior longitudinal fasciculus (occipitotemporal)
• Impaired with lesions to temporal lobe

• V1

• Where/how
• Spatial perception
• Object locations
• Interacting with objects

• Object/shape discrimination
• Object perception
• Object recognition
• Object identification

• Case study of D.F.
• Damage to ventral stream
• Visual agnosia
• No loss to visual acuity
• Inability to name objects from seeing them (able to identify if held)
• Inability to match hand position with card slot when asked, but able to correctly align when asked to insert card

• Ability to recognize objects but not to apply this information toward goal-directed behaviour
• Associated with damage to the dorsal stream (where/how pathway)

Neuron properties of the visual pathways of object recognition:

Describe their receptive fields and how they relate to the pathway's function

• Parietal lobe (dorsal stream) receptive fields are not stimulated by particular sizes of stimuli
• Less concern with physical properties
• Come from fovea and periphery
• "Where" function because of lack of specificity for size and acuity

• Temporal (ventral stream) receptive fields encompass the fovea and process stimuli for identification
• "What" functions

• Ability to recognize objects despite changes in viewing position, illumination, and surroundings

• View-dependent frame of reference
• View-invariant frame of reference

• We store information about how an object would look in various viewpoints
• From memory we are able to recognize objects in various viewpoints

How has view-dependent frame of reference (theory) been challenged, and how has the challenge been addressed?

• Storing information about every object in every orientation would not jive with perceptual memory and speed of recognition
• Theory holds if we make comparisons against exemplar objects in memory
• Evidence to support: increased response time to identify novel objects as same/different

• Object constancy by identifying the critical features of an object

• Both
• View-dependent frame of reference occurs in right fusiform area
• View-invariant frame of reference occurs in left fusiform area

• Also called suppression effect
• Decrease in object recognition neural activity after repeated viewings

• Lateral occipital cortex

• No
• PET study showed similar activation of lateral occipital cortex when viewing familiar and novel shapes

• Cell that preferentially responds to a whole object (e.g., cat) rather than its parts

• Also called hierarchical coding hypothesis
• Final percept is coded by a single cell (i.e., gnostic unit)

• Susceptibility to error through neuronal misfire or death
• Perception of novel objects
• Changes in stimulus over time

• Neurons detect features
• Activation of constellation of neurons allows object recognition

• Inability to identify seen objects while retaining ability to perceive shapes and identify touched objects
• Example of intact perception with impaired recognition

• Kinesthetic codes
• Multimodal representations (i.e., tactile and visual)
• Mental manipulation of objects
• Action knowledge
• Learning -- we have more experience with inanimate objects that can be held

• Increased activation in premotor cortex when viewing maniplatable objects

• Better recognition  of objects when they can be represented in motor terms

• Case study of J.B.R.: associative agnosia more pronounced when viewing living things

• Superior temporal sulcus & inferotemporal gyrus
• Cells that respond only to faces
• Faces must be ecologically valid
• Fusiform face area

In macaque monkeys

• Single-cell recordings show greater activation of STS, inferotemporal gyrus, and FFA when viewing faces
• Increased BOLD response in the FFA when viewing faces
• Stimulation of these areas causes monkeys to report seeing faces (when they haven't)

• Superior temporal sulcus: dynamic perception
• Features that change (e.g., expression)

• Fusiform face area: invariant facial properties

• No
• We are "experts" at faces; people who are experts at other things (e.g., cars) show greater activation of the fusiform area when viewing that object
• Specialized areas also for body processing (fusiform body area), place (parahippocampal place area)

• Analytic processing: processing of component parts
• Most objects are perceived this way
• Holistic processing: processing the stimulus as a whole
• Facial processing
• Impaired ability in prosopagnosia
• Retained ability to recognize parts, but inability to integrate into a whole

• Ability to predict what a participant is looking at based on receptive fields patterns of neural activation

• Voxel-level encoding: recording in V1, V2, and V3 to determine receptive fields of individual voxels there
• Match voxel activation patterns to known patterns

• Process of attending to a stimulus
• Modulation of perceptual processing
• Changes in neural activity when stimuli are attended to
• Mechanism that allocates attentional resources and controls flow of information to the brain

Top-down

• Voluntary
• Selective
• Goal-driven
• Can occur with or without changing focal point (i.e., overt or covert)

Bottom-up

• Involuntary, reflexive
• Stimulus-driven

• Idea that not all stimuli make it "in" for processing
• Limited intake of information
• Consistent with early selection models

• Model of attention
• Gating model; at initial stages of perception, attention selects some information for higher processing and discards other information
• Attention filters at the level of sensory processing
• Information loss due to lack of processing

[image]

• Model of attention
• Everything is processed
• Attention filters at the level of higher perceptual analyses (i.e., higher order processing is unconsciously selective)
• Full processing of all information, but with conscious awareness or responding only occuring for one

[image]

• Both have evidence against (e.g., cocktail party)
• ERP evidence consistent with early selective processing
• Some information selected for further processing, other information is discarded
• New hybrid suggests that all stimuli are processed at the sensory level, but past that point signal strengths are attenuated if they do not receive attention

• All parts of the visual pathway (e.g., lateral geniculate nucleus, V1)
• Greater activation of extrastriate regions compared to V1

• ERP study
• Participants had to attend to first the right visual field and then the left
• Activation found in the occipital cortex in the hemisphere contralateral to the field of visuospatial attention

• There is competition between stimuli when they fall in the same receptive field
• Receptive fields get larger up the visual hierarchy, which makes competition greater
• Attention biases this competition, such that neuronal firing is stronger for the stimulus that is attended to
• Effect is most pronounced in V4 because of larger receptive fields

• Participants stared at a fixation point while being shown either sequential or simultaneous stimuli with either passive or covert attention
• Reduction in activation between sequential and simultaneous presentation in V4, but no difference in V1

• Covert attention tasks show increased activation of the lateral geniculate nucleus, decreased activation of the inhibitory thalamic reticular nucleus, and greater activation of V1
• Bottom-up process, since attention is modulating early visual processing

• Item pops out
• Conjunction search

• Visual search for a stimulus when there are distractors
• Can be voluntary (e.g., systematic) or involuntary (e.g., reflexive eyemovements, automatic spotlight)

• Attention is drawn to salient objects based on notable features/properties
• Knowledge may also play a role (e.g., having a rough idea where the stimulus will be)

• Various extrastriate regions
• Each specializes in a type of feature (e.g., colour, size)

• Distinct patterns of responding are evident when attending to one feature as opposed to many features
• Selective attention in sensory-specific regions alters processing of sensory input
• Suggests independent feature processing before perception

• In class, discussed study showing that spatial occurs first
• Not always the case
• Feature attention may occur earlier if there is competition between stimuli of similar features

• Frontoparietal attention system
• Parietal cortex

• Goal-directed attentional allocation
• Source of location bias in attention
• V1 and V4 modulatory activity
• Attentional shifts (cognitive flexibility)

• Right hemisphere
• Reflexive (attention driven by stimulus)
• Maintaining vigilence

• Superior colliculus
• Overt attention
• Eye movement
• Visual search/guiding eyes to salient features
• Pulvinar (thalamus)
• Covert attention
• Reflexive spatial attention
• Filter

• To the brain

• Away from the brain to output

• Arriving
• From receptors to brain

• Exiting
• From brain to output (e.g., muscles)

• Primary motor cortex
• Association motor areas
• Supplementary motor cortex
• Premotor cortex
• Posterior parietal cortex

• Voluntary movement
• Planning
• Control
• Execution
• Goal-directed
• Homunculus
• Topographical arrangement

• Trajectory-based
• Muscle memory in space
• Movement based on goal
• Location-based
• Visual system movement based on target

• Removing afferent neurons from monkeys does not affect motor responding
• Suggests against higher-order
• Monkeys still respond correctly after applying a torque that opposes direct movement
• Suggests that target was a location, not a particular movement
• Endpoint control of movement inherent to location-based coding

• Increased firing when movement is in a certain direction
• Correlation between M1 firing and movement direction

• Summation of preferred-directions of response from individual neurons
• (Not much information gleaned from individual neurons' preferred-direction responding)

• How well an individual neuron aligns with a population vector

• Monkeys given warning cue that they will need to respond soon
• M1 neurons active before movement (in response to cue)

• Change just before the movement is executed
• Implicated in planning

• Planning aligns with preferred direction; execution most neurons are firing in non-preferred directions
• Thus, difference in firing patterns
• Good because it allows for flexibility in motor responses

• Affordance competition hypothesis

• Affordance: constant updating of sensory information via feedback loops
• Competition: higher-order decision making constrains outcomes with respect to goals, outcomes, etc.
• We select actions and how to achieve them at the same time
• While you execute a behaviour, the next is being planned
• Suggests that motor systems share neuronal activity

• Reaching
• Holding

• Sequential movement
• Coordinated movements (both hands)

• Eye movements while looking at a target

• Actions with respect to a target (e.g., pointing)

Compare the premotor and posterior parietal cortices with respect to

i. Frames for movement

ii. Changes under TMS

Premotor cortex

• Hand-centred frame for movement
• Represents position of target object relative to the hand
• TMS increases multipoint movement without conscious intention

Posterior parietal cortex

• Eye-centred frame for movement
• Represents object's location in space
• TMS increases desire to move without corresponding action

1. EEG registers population vector activity from M1, premotor cortex, and parietal cortex
2. EEG information entered into computer
3. Computer algorithm transforms EEG data into an external effector source

• Basal ganglia
• Striatum
• Subthalamic nucleus
• Globus pallidus
• Substantia nigra
• Cerebellum

• Striatum

• Processed through either direct or indirect pathway

1. Striatum
2. Inhibitory signal to globus pallidus (internal) & substantia nigra (pars reticularis)
3. Inhibitory signal to thalamus
4. Excitatory signal to cortex

• Excitatory modulation from D1
• Cortical excitation
• Fast process

[image]

1. Striatum
2. Inhibitory signal to globus pallidus (external)
3. Inhibitory signals to subthalamic nucleus and globus pallidus (internal)& substantia nigra (pars reticularis)
• STN sends excitatory signals to globus pallidus (internal) & substantia nigra (pars reticularis)
4. Inhibitory signal to thalamus
5. Excitatory signal to cortex

• Inhibitory modulation from D2
• Cortical inhibition
• Slow process

[image]

• Huntington's: over-initiation of movement
• Impairement of indirect pathway
• Hypoactivity of globus pallidus (internal) increases cortical activity

• Parkinson's: disorganized movement, difficulty initating movement
• Hypoactivity of direct pathway
• Hyperactivity of globus pallidus (internal) decreases cortical activity

• L-DOPA
• Deep brain stimulation

• Dopamine release from substantia nibra (pars compacta) into striatum increases direct pathway activity and suppresses indirect pathway activity

• Inhibition at baseline!
• Prevents some movements from being initiated
• High activation needed to overcome inhibition

• Winner-takes-all system: only one action will reach the threshold to overcome inhibition
• Signal activation releases movement from basal ganglia's inhibition

• Neuron that fires both when performing an action and when viewing another perform the action

• Premotor cortex
• Parietal & temporal lobes

• Action is real and visible (i.e., not mimed)
• Action does not need to be seen, as long as it is inferred
• Action can be heard 
• Action can be natural continuation of what was last seen (e.g., hand reaching for an object when a screen comes down)
• Specificity varies
• Differential firing when grasping has diverging goals (e.g., grasping fruit to eat vs. to put into a container)
• Some respond to general grasping while others respond to specific behaviours (e.g., particular hand position)

• fine-tuning new motor behaviours

• Sensorimotor interactions that guide motor learning

• At baseline, participants were very accurate at performing a behavioural task
• When normal vision is disrupted with prism glasses, participants are initially impaired but show improvement
• Disruption causes increased cortical activation
• Practice causes decreased cortical activation
• After adaptation and subsequent removal of glasses, students show over-compensation, such that motor behaviours still reflect disorted reality of prism glasses

• Cerebellum
• tDCS to cerebellum increases learning rate of new tasks

• M1
• tDCS to M1 increases retention of acquired skills

• Also called prediction models or forward prediction models
• Dynamic use/integration of information to make predictions regarding outcomes of motor behaviours
• Occurs in the cerebellum via projections from M1 and sensory systems
• Temporally specific (i.e., depends on perception and conditions)
• Improves motor adaptation