Cognitive Neuroscience Exam #1

2 Kinds of Brain Cells

1) Neurons: transmit electrical signals and do information processing (~100 billion)

2) Glia cells: non-electrical supporting, cells (more than half of the brain’s volume)

Neurons

• Specialized cells for the processing and transmission of information

  • Occurs through electrical and chemical communication (only cells that communicate like this)

• Cell body, dendrites, axon, and myelin sheath

• Shape varies by function

Dendrites

• Antennas that receive information from other neurons

• Contain many branches (dendric tree)

• Also may have little bumps called dendritic spines (result of learning something)

Axon

• Sends information to other neurons

• Typically the longest part of a neuron

Myelin Sheath

• Insulates the axon (bumps in diagrams)

• Helps transmission of signals

• Made up of a type of glia

• Fatty, white

  • Make up the white matter of the brain

• Fiber tract: groups of axons going to the same place

• Myelination has a developmental course

• Disruptions/damage can lead to neurological disease (e.g., multiple sclerosis)

Glia

• Supporting cells

• Critical to:

  • Modulating communication between neurons

  • Supporting connections between neurons

  • Guide developing neurons

  • Removing dead neurons & and help with reorganization when there is brain damage

Blood Brain Barrier

• No blood IN the brain

• Keeps a protective barrier to keep toxins out

• Glia help get nutrients from the blood to the neuron

Neural Communication

1. Neural transmission inside the cell (via electrical changes)

   • Dendrites (mostly) receive information

   • Collects in the soma

   • Information is sent down the axon to the axon terminals

   • Sends to other cells via electrical changes in the cell which in turn activates the synapse (the connection to other neurons)

2. Communication between cells (via chemical transmission)

Cell Membrane

• Separates the inside of the neuron from the extracellular fluid

• The fluid inside and outside the neuron are filled with ions (charged atoms)

• The inside concentrations are different from the outside concentrations

Electrical Signals

• Cell membrane keeps some ions inside the cell, and some outside

• When a neuron is at rest, the inside is negatively charged compared to the outside of the neuron

• Resting potential (-70 mV)

• When a neuron receives activity from another cell it can affect the concentration of ions

• Input from other cells can either open or close channels that allow certain ions in or out

• The change in ions due to this connection change the electrical charge of the neuron

Action Potential

• neuron firing, or “spikes”: change in charge

• If the connection sends +ions in the cell (Na+), it becomes more positive

• If positive enough (-55 mV) threshold of excitation occurs

• The neuron “fires”

• Sending the charge, rapidly to a peak of +40 mV

• Depolarization

• Repolarization- potential moves back to resting potential

• Hyperpolarization- briefly becomes more negative

• Once started, neuron cannot fire again until back to resting state

• Some connections can make the cell more positive (sending +ions into the cell)

• Some connections can make the cell more negative (sending -ions into the cell)

  • Hyperpolarizing the neuron

  • Taking it further away from having an action potential (inhibition)

• “All or nothing”

  • Was the threshold of excitation reached?

• Magnitude isn’t different with stimuli, but rate of firing is

Neuron to Neuron Communication

• Transmission between cells is chemical- neurotransmitters

• Released by presynaptic cell (axon)

• Across the synaptic cleft

• Received by the receptors on the postsynaptic neuron

• Opening channels that either depolarize the neuron or hyperpolarize the cell

• End result is postsynaptic neuron either having an action potential or not

• Based on the neurotransmitter passed and whether there is enough signal to pass the threshold of excitation

• In the end, all behavior boils down to this

Nervous System

• Peripheral Nervous System (anything outside of brain and spinal cord)

• Central Nervous System (most relevant to this class)

• Each vertebrae covers a section of the body

• Damage can result in lack of sensation in or motor control for the body areas served by the spinal cord at damage or below

Peripheral Nervous System

• Somatic NS: controls muscles, sends sensory information to the brain

• Autonomic NS: made up of sympathetic nervous system (fight or flight) and parasympathetic nervous system (rest and digest systems) as well as new enteric nervous system (gut/brain axis)

Central Nervous System

• Most sensory information (e.g. touch, pain) relay through the spinal cord

• All motor commands from the brain are sent to muscles via the spinal cord

Main Tissues of the Brain

• Gray matter= neuronal cell bodies

• White matter= axons, myelin, and glia cells

  • Represents the axonal connectivity of the brain

  • Most notable fiber tract: corpus callosum

  • Within hemispheres, between hemispheres, and between cortical and subcortical regions

• Ventricles= hollow chambers filled with cerebrospinal fluid (CSF)

  • CSF resembles blood plasma, but there’s no blood because of the blood-brain barrier

  • 4 main ventricles

  • Has direct implications for traumatic brain injury (TBI)

Meninges

• Membranes that surround the brain and spinal cord

• Protect the CNS

• Meningitis= inflammation of the meninges

Sagittal Plane

Bisects the body  into right and left halves

Coronal Plane

Divides the body into front (anterior) and back (posterior) regions

Horizontal Plane

Divides the brain into upper and lower parts (also called “transverse” or “axial” plane)

Anterior

Head end (also called “rostral”)

Posterior

Tail end (also called “caudal”)

Dorsal

Top part (also called “superior”)

Ventral

Bottom part (also called “inferior”)

Distal

Far part of brain

Proximal

Near part of brain

Brain Stem and Hindbrain

• All part of brain stem, critical to survival, rough sensory processing, motor tracts, and cranial nerves

  • Medulla

  • Pons

  • Midbrain

• Cerebellum

Medulla

• Sits on top of spinal cord

• Pretty critical to basic functioning

• Respiration, heart rate

• Arousal (via reticular activating system)

• Motor tracts

Pons

• Sits on top of medulla

• Lots of connective pathways

• Balance and eye movements

• Sleep cycles

• Supplier olive: important stop in the auditory pathway

Midbrain

• Sits on top of pons

• Some cranial nerve action

• Visual and auditory orienting mechanisms

Cerebellum

• Important for movement (tone/balance, muscle guidance and control)

• Learned movement

• Controls the timing aspect of movement

• Involved in cognition at large

• Contains all inhibitory neurons and about ⅓ of neurons in the whole brain

Subcortical Structures

• Hypothalamus

• Thalamus

• Basal Ganglia

• Limbic System

Hypothalamus

• Maintains equilibrium via endocrine system (hormonal system)

• Eating thirst, body temperature, etc.

Thalamus

• Gateway to cortex

• Relay center for almost all sensory and motor information

• Divided into different regions that subserve pathways for different systems

Basal Ganglia

• Collection of nuclei

• Dopamine nuclei

• Related to movement and implicit/autonomic memory

• Highly connected to frontal lobe

Limbic System

• Collection of structure (amygdala, hippocampus, cingulate cortex)

• Important for relating the organism to its environment based on current needs to the present situation, based on previous experience

• Implicated in emotions, learning, and memory

Cerebral Cortex

• sulci= grooves, gyri= bumps, fissure= deep sulci

  • Folds increase surface area

  • Sulci and gyri are very stable across individuals and species

  • That’s why atlases work

• The cortex is divided into four lobes/cortexes:

  1. Frontal (most anterior region)

  2. Parietal (region between the frontal and occipital lobe)

  3. Occipital (posterior region, visual processing)

  4. Temporal (lateral region, auditory, visual, semantic and language processing)

• Major Landmarks: Central Sulcus, Sylvian Fissure, and Longitudinal Fissure

Primary Cortex

• Primary visual cortex

• Primary auditory cortex

• Somatosensory cortex

• Primary motor cortex

Associate Cortex

• Non-primary cortex

• Typically doing higher level processing (learning, planning, memory, etc.)

• Can be unimodal (one sense) or multimodal (multiple senses)

Brodmann Areas

Different regions of cortex have been demarcated by histological examination of the cellular micro-anatomy aka cytoarchitectonic maps (~50 regions)

Direct Neuroimaging Methods

Directly measures neuron activity

Indirect Neuroimaging Methods

Measuring something that correlates with neuronal activity, e.g. fMRI

Limitations of Neuroimaging

1. The physical properties of the recording system

2. The physiological constraints of the brain

• Images of brain activity only have meaning when using the correct experimental design and interpreted using the correct analysis

Lesions

• Lesions are a result of traumatic brain injury, surgical resection, strokes as a likely reason, and disease

• Gold standard of learning about brain-behavior relationships

• Studying the impaired, we can learn about the unimpaired

• Can determine cause and effect

• Strengths of neuropsychology are establishing causal​​ relationships (changes in behavior due to changes in cortex)

Brain Lesion Studies

• Single case studies (provides great insight, but does it generalize?)

• Group case studies (more support of general mechanism, but difficult to find multiple patients with similar lesions)

  • Group can be heterogenous

  • Lesion can be heterogenous (size, severity, isolated damage)

Double Dissociation

• Normally derived from 2+ single cases with complementary profiles of strengths and weaknesses

• Used to infer the two tasks/stimuli use separate neural/cognitive resources

Weaknesses of Brain Damage Studies

• Damage is largely dictated by vasculature (strokes)

• Damage is typically large

• Size and shape depend on injury

• Not specific to anatomical or functional boundaries

• Functional deficits are rarely selective

• Individuals may experience cortical reorganization

• Limits the extent to which we can generalize from specialized populations

• Moreover, still making conclusions about what can’t be observed, only observing regions critical to behavior (not the whole network of regions), and the brain may compensate

• Lesions limited to the patients that present to you (most other methods you can design experiments and test hypotheses)

Transcranial Magnetic Stimulation

TMS

• Transient and safe disruption of local neuronal activity

• Scrambles neuron firing

• “Virtual lesions”- causal link

• Provides both information about “where” and “when”

• Important to have a control site

• Two types: single-pulse TMS and rapid TMS (rTMS)

• Can makes claims of causality, but can only get lateral surface of the brain and have to already know where to look for an effect

Transcranial Direct Current Stimulation

tDCS

• 9v battery

• Stimulated anodal (positive) electrode- increase activity

• Stimulated with cathode (negative) electrode- decrease activity

• Less intense and less focused than TMS

Single Unit Recording

• Measuring the action potential of neurons

• Recording the changes in electrical potentials through an electrode inserted through the brain

• Highly invasive- animal studies

• Typically intracellular recordings

Electrocorticography

ECoG

• Electrode implantations in humans- done for medical reasons only

• Epilepsy- seizures may be induced by aberrant neural activity in a focal region

• May be able to relieve symptoms by resecting that region- last resort

Intracranial Electrodes

• Not just passive recorders

• Can stimulate too!

  • “If this neuron/area is stimulated, we expect to see a change in X behavior”

• Penfield pioneered brain stimulation: testing for local, critical function “eloquent cortex”

• Therapeutic means: deep brain stimulation for Parkinson’s, tremors, etc.

Neurophysiology

• Recording directly from neurons!

• Great temporal and spatial resolution

• Both passive measurement and active manipulation

Electroencephalography

EEG

• Measures electrical activity that is readable from the scalp

  • Omnibus recording technique

  • The potential from a single neuron is too small to be picked up

  • Measures populations of neurons with synchronized potentials & oriented similarly

• High temporal resolution (ms) but poor spatial resolution

Magnetoencephalography

MEG

• Measures magnetic field activity that is readable from the scalp

• High temporal resolution (ms) but poor spatial resolution (MEG has better spatial resolution than EEGs though)

Event Related Potentials

ERPs (EEG and MEG signal)

• Evoked response as a function of task

• Takes the average of MANY trials

• Identifiable peaks and troughs in electrical activity

• Strange convention: up=negative

• Are measured based on their amplitude

• E.g. the P1- the first “major” positive waveform measured over lateral occipital cortex

  • Attending to specific region of space modulates the amplitude, but not latency, of the contralateral P1

Oscillations

EEG and MEG signal

• Steady state measures of ongoing waves of EEG activity over a period of time

• Frequency= the speed of the peaks and troughs

• Looking at the power of different frequency bands

• Power analysis (which frequency bands are the strongest and when)

• Time frequency analysis (frequency bands can indicate different types of cognition)

Source Localization

• Hard to know where the source of the signal is coming from

• Inverse problem- many sources can lead to the same EEG response

EEG and MEG Pros and Cons

• Advantages

  • Direct measure

  • Noninvasive

  • Has excellent temporal resolution (ms)

• Disadvantages

  • Requires large populations of neurons to be synchronized

  • Has poor spatial resolution (on the order of cm)

  • Localization of source can be complicated (MEG better than EEG)

CAT Scan

• Structural

• Derivative of X-rays

• Good at seeing fluid or different tissue mass in the brain

Positron Emission Tomography

• Records emissions of radioactivity from injected radioactive chemicals

• Can tag certain molecules (e.g. look at neurotransmitters)

• Can look at metabolism of neurons (e.g. glucose consumption)

Three Types of Data from MRI

1. MRI Structural Data

2. fMRI Functional Data

3. Diffusion Weighted Imaging (DWI, structural)

MRI Structural Data

• Different tissue types (grey matter, white matter, CSF)

• Each tissue has different physical properties under MR imaging

• Static- a snapshot of the brain

• Very high resolution

• Types of analysis

  • Look for damage

  • Size of region

  • Grey matter thickness

Diffusion Weighted Imaging

• White matter connections in the brain

• Integrity of myelination (e.g. MS)

• “Looking at flow of water in the brain, and how it is different in different tissues”

• Color (hue)= direction of the highest diffusion

• Brightness= degree of anisotropy

• Looking at uniformity.integrity of direction

• Tractography

• Good for looking at connections in the brain

fMRI

• fMRI signal= Blood Oxygen Level Dependent (BOLD)

• We are looking at blood, not looking directly at neural activity

• Oxygenated and deoxygenated blood have different magnetic response times

• basic model of relationship between BOLD fMRI and neuronal activity correlational (not causal)

• Two things have massively improved over the years:

1. Spatial resolution (field strength [Tesla] and more advanced protocols)

2. Sophistication of analysis and design techniques (partly due to all low hanging fruit already picked)

fMRI Pros and Cons

• Advantages

  • Great spatial resolution ~mm

  • Can image the whole brain

  • Don’t need to preselect where to measure

  • Non-invasive

  • Can design hypothesis driven experiments

• Disadvantages

  • Poor temporal resolution

  • Indirect measure of brain activity

  • Looking at correlations not causality

  • Some individuals cannot participate (e.g. anyone with magnetic implants, such as pacemakers)

  • Some individuals do not like to participate: it’s a confined environment (claustrophobia and VERY loud)

  • Must lay still for ~1 hour

  • Very expensive (~$1000 a subject)

  • fMRi signal is slow

    • Hemodynamic response function (change in BOLD signal over time)

    • Temporal resolution of fMRI signal is mostly limited by the sluggishness in the hemodynamic response to stimulus presentation

Types of fMRI Analysis

• Whole brain analysis

  • More exploratory

• Region of interest analysis

  • Pick a priori region of brain to investigate

Subtraction Method

fMRI analysis method involving averaging together all the images acquired during the 'on' phase of the task, and subtracting the average of all the “off” images

Adaption Method

fMRI analysis method where region is selective for specific stimulus

Multi Variate Pattern Analysis

• MVPA

• fMRI univariate contrasts and adaptation designs look at the average activation across a region

• Looks at the pattern of activity voxel-by-voxel

• Look at the similarity in the pattern of activity to learn about how information is processed and presented in the brain

  • e.g. through correlation

  • More similar- the more evidence they relate to the same function/representation of the region

Functional Connectivity

fMRI analysis method showing correlation between time series from different regions; infer communication between regions

Brain Reading

• Brain response can be used to predict which object is seen or imagined from a limited set (e.g. face v. house, bottle v. shoes)

• However, can only be done if experimenter pre-tests the participants on these items (to know where to look in that particular person)

• Think about what the comparison is

• Reconstruction

fMRI Pitfalls

• Reverse Inference

  • Not a 1:1 relationship of brain and behavior

• Individual Differences

  • Group averages are sometimes misleading

  • Lots of individual variability

Default Mode Network

• Areas of the brain that were more active at “rest,” or more tuned in to internally generated thought

• Can use that as a tool to examine and understand brain function

• Tasks and default network are anti-correlated

• “Baseline is greater than task, rather than task greater than baseline”

• Can use the default network and resting activity to explore brain function, especially across different populations

Hierarchy of Action

• Lowest level of movement= reflexes

• Highest level of movement= voluntary planned action based on goals and intentions

• More basic cognitive mechanisms in action include:

  • Object recognition

  • Locating an object in space

  • Linking object with limb positions and motor commands (sensory-motor transformation)

  • Knowledge of the present state of the body (somatosensation) and position of limbs in space (proprioception)

  • Selecting a specific movement (direction, force etc.)

  • Generating the movement

  • Monitoring the progress and outcome of the action (feedback)

• Higher cognitive mechanisms include:

  • The goals, plans and intentions of an individual

  • Stored semantic knowledge of objects and their uses

  • Stored motor programs for specific objects (e.g. lifting cups) and schemas for familiar situations (e.g. making tea)

Motor Neurons and Reflexes

• Reflex- quickest movement to control movement

• Stretch reflex, signalling goes through spinal cord (not up to brain)

  • Regulates the length of the muscle

• Allows things like posture stability to be maintained without involving the cortex

• Number of muscle fibers a neuron innervates relates to precision of movement (less fibers= less precision)

Motor Tracts

• Motor complex movements signals sent from the brain via motor tracts

• Organization of the tracts is meaningful of how our brain executes movement

• Lateral corticospinal tract: and medial corticospinal tract:

Lateral Corticospinal Tract

• Distal limb movements (arms, fingers, legs, foot, etc.)

• Fine motor control

• Cell bodies in primary motor

• Contralateral control- crosses at the medulla

Medial Corticospinal Tract

• Trunk and proximal limb muscles

• Postural control, bilaterally constrained movements (e.g., walking, bending)

• Contralateral control and Ipsilateral control

Cortical Motor Regions

• Primary Motor Cortex (M1)

• Supplementary Motor Complex

• Premotor areas

  • Frontal eye fields

• Anterior Cingulate

• R Inf. Frontal Cortex

• Parietal Lobe

Primary Motor Cortex

• Executes all voluntary movements of the body

• Somatotopically organized and crossed (left hemisphere= right side of the body)

• Stimulation results in movement

• Cortical magnification

• Might be organized by behavior rather than body

• Damage

  • Weakness or hemiplegia (the loss of voluntary movement on the contralateral side of the body)

• Primary motor neurons have a preferred direction

• Fire a little less for nearby directions; a lot less for very different directions

• Other information coded (not sure how these are coordinated):

  • Force

  • Torque

  • Trajectory and distance

Cortical Magnification

The amount of cortical space given to body part is not with respect to the size of the body part, but the precision and extent of movement

Population Vector

• Problem: Many neurons in M1 fire for a single movement, although they may have many different preferred directions.

  • How to know where to go? (Most active neuron?)

  • But movement is very precise and the preferred direction is quite broad…

• Solution: Population vector

  • Take the summed activity

  • Very precise direction

Motor Plan

• An abstract representation of intended movement

• The brain generates this entire plan of action before movement commences rather than creating the plan in a step-by-step manner as actions are being performed

• Implemented via supplementary areas

• Supplementary motor area (SMA)

• Premotor cortex (PMC)

  • NOT primary motor cortex!

• SMA and PMC modulate activity in primary motor to execute commands to move the muscles

Supplementary Motor Cortex

• Plays a role in planning, preparing, and initiating movements

• Both contralateral and ipsilateral control of M1, and also feeds into contralateral SMC

• Damage results in bimanual coordination impairment

  • Can’t use hands independently

• Motor planning

  • Active before action

  • Active for a specific sequence

  • Not active for repetitive movements

• Complex movement

  • Sequential movements

  • Coordination between limbs

  • TMS reduced ability to perform sequenced motor program

• Deals with spontaneous well-learned actions that don’t place strong demands on the environment

  • Initiated by internal goals

• May be involved with more domain general sequential processing

  • Numerical processing, working, memory, musical processing, language

Premotor Cortex

• SMC → PMC → M1

• Dorsal region: integrates motor commands with sensory cues

• Ventral region: integrates with manipulating specific object

• How it’s actually done. Moving from abstract representation of movement (SMC) to more concrete commands (PMC)

  • Ex./ wanting to spread cream cheese on bagel to actually determine how the hand, fingers, arm, etc. will perform the task

• Frontal eye fields

  • Voluntary eye movements

  • Distinct from reflexive eye movements (midbrain- superior colliculus)

• Mirror neurons

Mirror Neurons

• Respond to observed as well as self-enacted actions

• Part of action comprehension

• Basis of learning via imitation, and understanding action of others

• Foundation of communication?

• Embodied cognition

Anterior Cingulate

• Most involved when an action is novel or requires cognitive control

• Such as when a well-engrained response must be overwritten

• Involved in regulating the consequence and correcting

• Stroop task

• May modulate or override activity during simple motor tasks (most posterior)

• May modulate the selection of movements

• May modulate more complex motor actions or become active when a high degree of conflict exists

  • Posterior → anterior

• Gradient of going from more simple to more complex (most anterior)

Prefrontal Lobes in Action

• Involved in coordination of cognition generally (both external actions and internal thoughts)

• Involved in selection and maintenance of goals and responses

• Damages to this region does not impair physical movement but actions become inappropriate or disorganized

  • Perseveration (action repeating)

  • Utilization of behavior (act impulsively on irrelevant objects)

Parietal Cortex

• Integrates sensory information with movement

  • Spatial maps, and spatial map translation (e.g., into hand centered coordinates)

  • Overlaps with “where” or “how” visual stream

  • Overlaps with our somatosensory cortex

  • Preprioceptive information: sensory information received from internal sensors in the body, such as that about the position of body parts relative to one another

  • Kinesthetic information: actual movement of body parts

  • Feedbacks to premotor and primary motor cortices to correct and adjunct movement

• Largely left hemisphere

  • Bilateral control

• Damage (or TMS) leads to:

  • Adjusting movement

  • Misguided actions (e.g. misreach)

  • Grasping problems

  • Impairment of generating a mental model of movement (e.g.pantomime, or imagining)

Apraxia

• An inability to perform skilled, sequential, purposeful movement that cannot be accounted for by disruptions in more basic motor processes (e.g. muscle weakness)

• Usually a result of brain damage or trauma (usually left)

• Thought of as high order problem

• Bilateral

• Low level motor intact (e.g., grasping an object)

• Ideational/Conceptual and Ideomotor

  • Controversy over whether these are two distinct disorders, and one is just more severe

  • Ways to categorize apraxia

• Typically a result of damage to the parietal or frontal cortex

• Can be a result of the connections between frontal and parietal and M1

• But really can be any of our motor regions, cortical, subcortical which would determine the type of impairment

  • Spatial processing difficulties: RH parietal

  • Language, control of left hands: damage through corpus callosum

  • Visual feedback needed: requires different regions

Ideational Apraxia

• Inability to form a mental image of intended movement

• Issue with choosing correct action and the correct course of actions

• Inappropriate use of objects

• Impaired transitive gestures (object-related actions)

Ideomotor Apraxia

• Disconnection between the idea of the movement and its execution

• More pronounced for actions not initiated by interactions with external objects

• More pronounced for more abstract than concrete actions

• Pantomime impaired

Cerebellum in Action

• Posture and stability

• Timing associated with coordinating muscles

• Planning of movements

• Learning new skills

• Sensory motor integration and feedback

• Modulating effect on movement

• Damage= degrading motor abilities

• Ipsilateral control

• Organized for trunk/posture vs. limbs

• Damage means hard to coordinate movement, especially across multiple joints and with sensory feedback (ex./ dysarthia and cerebellar ataxia)

• Learning

• Prism glasses

  • Recalibration impaired

• Sensorimotor learning

• Forward model

  • Predict sensory consequences of motor actions, but does compute an error signal for future performance

• Timing device that provides a clock for events

  • Timing of initiation and cessation of aspects of the movement

  • Timing of discrete events (not continuous movements)

  • Affects temporal perception across domains (not just motor)

Basal Ganglia in Action

• Also called Striatum

• Collection of nuclei

• Basal ganglia loops= multiple pathways of basal ganglia involvement

• Highly connected to the frontal cortex

• Highly organized within different areas of BG

• Highly concentrated of the cells bodies generating the neurotransmitter dopamine

• “Setting” the motor system with regard to posture

• Motor planning

  • Important for initiating or stopping voluntary movements

  • Controlling the timing of and switching between motor acts

• Skill learning

  • Acting as an autopilot for well-learned sequential movements

  • Implicit learning

• Motivated movement with respect to reward

• SNc site of dopamine

• Intricate excitation and inhibition

• Overall output is to inhibit movement

• Direct (fast) pathway- promote movement (less inhibition on thalamus)

• Indirect (slow) pathway- inhibit movement (more inhibition on thalamus)

• “Gatekeeper”

  • Initiation of actions

  • Strong inhibitory baseline keeps system in check

  • Allows cortical representation of movement to become activated without triggering movement

  • As a motor plan gains strength, the inhibitory signal is deceased

Parkinson’s Disease

• Lack of dopamine

• Hypokinetic: absence of voluntary movement

• Posture

• Later stages develop delusions, paranoia, and memory issues

• Lack of inhibition through the direct pathway

• Lack of excitation to motor cortex