Cognitive Neuroscience Midterm 1

rationalism

knowledge through reasoning

empiricism

knowledge through experience

associationism

complex mental processes are formed through the association of simpler ones

Hermann Ebbinghaus

internal mental processes can be measured in reproducible ways

Edward Thorndike

adaptive behavior through laws of effect and exercise; basis for operant conditioning; analogy to human learning

John Watson

psychology as the science of observable behavior; focus on stimulus-response

cognitive psychology

established in 1950s-60s as branch of psychology focused on studying mind in terms of information processing; shifted away from behaviorism and stimulus-response; challenged idea of brain as blank slate built from experience

Ulric Neisser

father of cognitive psychology

Gale

conducted experiments on live animals to demonstrate brain is essential for consciousness (not widely accepted until 18th century)

Thomas Willis

father of neuroscience; established link between brain damage and specific behavioral deficits

Franz Gall

two brain hemispheres connected by white matter; contralateral organization; higher mental functions correlated with size of cortex; brain organized into functionally specialized regions

phrenology

pseudoscience proposed by Gall that larger brain regions cause bumps on the skull

Jean Pierre Flourens

conducted ablation studies on pigeons and rabbits and found brain damage often caused no loss of function or effects unrelated to phrenology; demonstrated different brain divisions have distinct functions

aggregate field theory

the whole brain is responsible for behavior (challenging localization)Jo

John Hughlings Jackson

functional localization of cognitive functions; topographic organization in the brain; three-level hierarchy of nervous system organization

Paul Broca

human ablation studies; Patient Leborgne (Tan) who could understand language but could not speak; Broca’s area is left frontal lobe region for speech production

Carl Wernicke

sensory aphasia (fluent speech but impaired comprehension); speech marked by unusual word substitutions and mispronunciations (paraphasia); Wernicke’s area found in left temporal lobe

impact of Broca and Wernicke

demonstrated focal brain damage causes specific behavioral deficits; language comprehension vs. production

David Ferrier

discovered primary visual, auditory, and tactile cortex using stimulation and ablation

Gustav Fritsch and Eduard Hitzig

mapped out motor strip through electrical stimulation of dog cortex

Wilder Penfield

electrical stimulation to localize seizure origins in epilepsy patients; revealed organization of motor, sensory, speech, and memory functions; provided early functional mapping of human brain

Kornbinian Brodmann

classified cortex into 52 regions using cell staining

cytoarchitectonics

structural arrangement of neurons across brain regions

Camillo Golgi

developed staining technique to visualize individual neurons

reticular theory

proposed by Golgi; nervous system as a singular, interconnected network

Santiago Ramon y Cajal

neuron doctrine: nervous system is made of individual neurons supported by glial cells; observed unidirectional transmission of electrical signals from dendrites to axonal tip; information is transmitted within neurons via action potentials

Hermann Hemlholtz

electrical impulses carry information along a neuron’s axon; first to measure speed of nerve conduction; developed law of conservation of energy

human brain

contains approximately 86 billion neurons; each neuron can form up to 10,000 connections (10 quadrillion total synaptic connections); number of neurons and connections can fluctuate due to learning, experience, and neuroplasticity; humans have highest number of neurons in cerebral cortex

neuron

comprised of nucleus, soma, dendrites, axon, and axon terminal

soma

contains nucleus which acts as cell’s control center, integrating incoming signals and generating output signal

dendrites

branching fibers with protrusions (spines) that receive synaptic input

axon

tube-like nerve fiber that transmits signals to other neurons

axon collaterals

allow an axon to transmit signals to multiple neurons

axon terminals

small branches at the end of the axon where communication occurs

sensory neurons

carry sensory information to the brain

relay neurons (interneuron)

transmit between sensory and motor neurons

motor neurons

transmit to muscles and glands

pyramidal cells

projection neurons, primarily excitatory, notable for their long apical dendrite

stellate cells

interneurons with axons that don’t leave the cortex, can be excitatory or inhibitory (but often inhibitory)

glial cells

support and insulate neurons; speed up signaling, regulate extracellular chemicals, and enable neurons to modify connections; approximately equal numbers of neurons and glial cells in the CNS

radial glial cells

guide neuron migration during embryonic development

myelin

fatty substance that covers axons

myelination

insulates axons from each other, preventing signal interference; speeds up conduction, enabling efficient long-distance communication

symptoms of demyelination

motor impairments, sensory deficits, cognitive dysfunction, vision problems, fatigue

neuronal signaling

1. neurons receive input from other neurons through dendrites

2. if inputs are strong enough the neuron fires and an electrical pulse (action potential) is sent down the axon via electrical transduction

3. synaptic transmission of information from the axon terminal to the next neuron is usually through chemical transduction at the synapse

resting membrane potential

typically -70mV; at rest the inside of the neuron is more negative than the outside; membrane potential is the difference in electrical charge between the inside and outside of a neurona

action potential

brief reversal of the resting membrane potential

maintaining resting membrane potential

neuronal membrane (bilayer of fatty lipids) prevents ions from crossing except at ion channels and pumps; resting membrane potential results from asymmetrical ion distribution (more Na, Ca, and Cl outside and more K inside the neuron); resting potential arises from unequal distribution of ions inside vs. outside the neuron

ion channels

specialized structures with a pore that can open, close, or inactivate

diffusion

ions move ions from high to low concentration to reach equilibrium

electrical gradients

ions are attracted by opposite charges and repelled by like charges

ion pumps

at rest Na channels are closed while K crosses very slowly; ion pumps consume energy (ATP) to move ions against concentration gradients

Na/K pump

critical for preserving resting membrane potential; moves 2 K inside for every 3 Na moved outside; maintains higher K concentration inside and higher Na concentration outside; moves more positive ions out than in which contributes to negative resting potential

electrochemical equilibrium

stable resting potemtial at -70mV; balance of two forces prevents unlimited charge buildup

action potential

brief change in the polarity of the electrical charge across the membrane; depolarization must exceed threshold of excitation for action potential to occur; all or nothing firing principle

Hodgkin-Huxley Cycle

1. depolarization of membrane to -55mV; voltage-gated Na channels open

2. Na influx rapidly increases membrane potential leading to a spike at +40mV

3. repolarization occurs; Na channels close; voltage-gated K channels open; dominant permeability switches back to K

4. Efflux of K pushes membrane potential below resting level (hyperpolarization/undershoot)

5. Return to resting potential

axon hillock

decision point for generating an action potential

all-or-none response

if threshold is reached, an action potential fires at full strength; if not, no action potential occurs; signal is actively regenerated along the axon by voltage-gated ion channels, preventing signal loss over distance

action potential propagation

one way transmission; influx of positive charge depolarizes the surrounding membrane; passive current flow brings membrane just ahead of the action potential to threshold; voltage-gated channels open and action potential propagates

refractory period and hyperpolarization

prevent backflow and ensure action potential moves only down the axon

refractory period

prevents immediate reactivation of voltage-gated Na channels, ensuring one way propagation of action potentials; without this neurons could fire at abnormally high rates and synchronize excessively, increasing excitability and seizure risk

axon diameter

affects action potential speed; larger axons correlate to faster conduction

myelination

affects action potential speed; insulates the axon and speeds up transmission

Nodes of Ranvier

gaps in myelin where voltage-gated ion channels regenerate the signal

saltatory conduction

axon potentials jump from node to node, reducing energy use and increasing conduction speed

synapse

region of contact where neuron transfers information to another cell

presynaptic neuron

axon’s output synapsing onto another neuron

postsynaptic neuron

receiving neuron typically at the dendrites

chemical transmission across neurons

neurotransmitters are responsible for sending nerve signals across the synapse; neurotransmitters diffuse from presynaptic cell across the synapse and bind to the postsynaptic membrane

chemical transmission features

common and numerous; slower than electrical; unidirectional; flexible in allowing for inhibitory vs excitatory connections

chemical synaptic transmission

1. action potential opens voltage gated Ca channels

2. Ca influx triggers vesicles in presynaptic neuron to bind to membrane

3. neurotransmitter is released into synaptic cleft via exocytosis

4. neurotransmitter binds to receptor molecules in postsynaptic membrane

ionotropic receptors

directly open ion channels causing fast responses

metabotropic receptors

activate indirect signaling cascades, causing slower but longer lasting effects

neurotransmitter diversity

over 100 neurotransmitters; some bind to different postsynaptic receptors meaning they can increase or decrease firing depending on receptor type; glutamate is the most common excitatory neurotransmitter in the brain

neurotransmitter removal

1. degradation - enzymes break down neurotransmitters into inactive components

2. diffusion - neurotransmitter moves out of synapse following its concentration gradient

3. reuptake - transport proteins pull neurotransmitter back into the presynaptic neuron for recycling or storage

effects of enhancing excitatory neurotransmitter release

strengthens postsynaptic activation which could enhance learning and memory but could also lead to instability, anxiety, and hyperactivity

EPSP

excitatory postsynaptic potential - positive ions flow into the cell leading to depolarization and the neuron being more likely to fire an action potential

IPSP

positive ions flow out (negative flow in) which leads to hyperpolarization and the neuron being less likely to fire

gap junctions

physically connect two neurons, allowing direct communication between cytoplasm

electrical synaptic transmission

permits fast, synchronized signaling where electrical changes in one neuron directly affect another; fast but less plastic/adaptable; less common but found in circuits that require precise synchronization

importance of electrical synapses

reflex circuits, rhythmic circuits, motor coordination circuits, sensory circuits

temporal synaptic summation

signals that arrive at the same location in quick succession

spatial synaptic summation

signals that arrive at different dendritic branches and converge at the soma

central nervous system

control center: brain and spinal cord

peripheral nervous system

courier: sensory nerves, motor nerves, ganglia (nerve cell bodies)

Somatic PNS

interacts with external world; neurons send messages between sense periphery and CNS; voluntary muscle control

Autonomic PNS (visceral)

regulating internal world; neurons control heart, intestines, and organs; automated, visceral function such as digestion

Afferent Pathway (input to CNS)

Somatic brings sensory input from CNS; Autonomic brings sensory input from internal organs to CNS

Efferent Pathway (output from CNS)

Somatic sends motor commands to voluntary muscles to contract and relax; Autonomic sends signals to organs to stimulate and regulate function

sympathetic

activates body to react to threats or opportunities; increases respiration, heart rate, and blood pressure; redirects blood flow from digestive organs to muscles

parasympathetic

shifts body to recovery mode when no urgent demands; decreases respiration, heart rate, and blood pressure; redirects blood flow to digestive system for energy replenishment

CNS commonalities

all mammals have a cerebral cortex but not all vertebrates; pallium is considered the evolutionary correlate of the cortex; comparative neuroanatomy highlights shared structures and species-specific adaptations in brain organization

rostral

toward the mouth

caudal

toward the tail

anterior

toward the front

posterior

toward the back

dorsal

toward the top

ventral

toward the belly

superior

toward the top

inferior

toward the bottom