neural basis - matt roser, L2 Flashcards
Who measured the speed of axon potentials and what was the speed?
Von Helmholtz measured the speed of axon potentials at 90 ft/sec
What hypothesis did Von Helmholtz refute?
The hypothesis of ‘vitalism’ which suggested that neural signals were a vital force of nature
Who is credited with the invention of the method for staining neurons?
Camillo Golgi invented the method of staining neurons with silver nitrate, known as the ‘Golgi’ method
What concept did Santiago Ramón y Cajal discover regarding neurons?
Cajal discovered the synapse and the functional polarity of neurons
What was the disagreement between Golgi and Cajal?
Golgi believed the nervous system was a continuous mass, while Cajal believed it was composed of individual units
What significant publication did Donald Hebb release in 1949?
The Organization of Behaviour
What does Hebb’s theory propose about brain activity?
It proposes that complex psychological phenomena might be produced by brain activity
What are neurons considered in the nervous system?
Neurons are the basic, distinct units of the nervous system
What is the resting potential of a neuron?
-70mV
What is the role of astrocytes in the central nervous system?
Astrocytes supply nutrients, structural support, clean-up, and chemical protection for neurons
What are the two primary types of glial cells in the peripheral nervous system?
Schwann cells and satellite cells
What is the function of the sodium-potassium pump?
It exchanges 3 Na+ (sodium) ions for 2 K+ (potassium) ions to maintain ion concentrations
-sodium ions must be kept in greater concentration outside the cell by low permeability
What happens when depolarization reaches a threshold in a neuron?
An action potential is generated
What is the synaptic cleft?
The space separating pre- and post-synaptic membranes
What are excitatory post-synaptic potentials (EPSPs) caused by?
Opening Na+ channels leading to depolarization
What do inhibitory post-synaptic potentials (IPSPs) do?
Hyperpolarize the neuron and move the potential away from the firing threshold
-K+ channels
What is temporal summation in neural processing?
PSPs in close succession overlap and add together
What is the most common excitatory neurotransmitter in the brain?
Glutamate
What is the role of GABA in the brain?
It acts as the most common inhibitory neurotransmitter
What effect does dopamine have in the brain?
It can be excitatory, inhibitory, or modulatory depending on the receptor
What is the mesolimbic system associated with?
Reward and learning
What is the difference between agonists and antagonists in drug action?
Agonists facilitate post-synaptic effects, while antagonists inhibit them
What is positive reinforcement?
The presentation of an appetitive stimulus in association with a behavior
What is the result of anterograde amnesia?
Inability to form new long-term memories following injury
What did Cajal propose about synaptic connections?
They are modified by learning and can persist as memory
strength can be increased by sensitisation and classical conditioning -> reduced by habituation -> storage of non declarative memory is embedded in the neural circuit that produces the behaviour -> unconscious memories
What is the effect of dopamine antagonists on reinforcement learning?
They block reinforcement learning
What is the role of the hippocampus in memory?
It is involved in memory consolidation
Fill in the blank: The brain’s most common inhibitory transmitter is _______.
GABA
True or False: The synapse is the junction where neurons communicate with each other.
True
What is the process of classical conditioning?
Association between two stimuli and an automatic response
What is Anterograde amnesia?
Inability to form new long term memories following insult / injury
What is retrograde amnesia?
Inability to recall memories preceding insult
Which brain structures are primarily involved in memory consolidation?
Medial Temporal Lobe & Hippocampus
What does ECT stand for?
Electroconvulsive therapy
Who is Henry Molaison commonly referred to in studies of memory?
H.M.
What type of surgery did H.M. undergo?
Bilateral resection of medial temporal lobe including the hippocampus
What type of memory remained intact after H.M.’s surgery?
Previous declarative memory (digit span, perceptual learning, instrumental & classical conditioning)
What type of amnesia did H.M. experience?
Dense anterograde amnesia
Is the hippocampus necessary for short term memory?
No
What is the critical function of the hippocampus?
Consolidation of new memories
What principle explains the strengthening of synapses through simultaneous input?
Hebbian learning
What must occur for long-term potentiation (LTP) to be induced?
*The postsynaptic cell must be depolarized (by strong input)
*The postsynaptic cell must receive additional input (weak input)
When was long-term synaptic potentiation (LTP) first observed?
1966
What is the cellular basis of all long-term learning?
Use-dependent strengthening of synaptic connections
What does Hebb’s law state?
‘Cells that fire together wire together’
What neurotransmitter is involved in long-term potentiation?
Glutamate
What type of receptors are NMDA receptors?
Double gated – transmitter & voltage
contain transmembrane channel for Ca2+
What happens when glutamate binds to NMDA receptors?
receptors depolarise the cell (remove the MG+ block), Opens Ca2+ channel, activating enzyme
What triggers the insertion of more AMPA receptors into the membrane?
Activation of enzyme by Ca2+, insertion of more AMPA receptors into the membrance, retrograde messenger leads to increased presynaptic glutamate release -> leading to bigger excitatory sensory potentials
What is the result of low-frequency stimulation of a synapse?
Long-Term Depression
What happens to inputs that do not contribute to postsynaptic firing?
They are weakened
What do neurons work as in processing information?
A network of units
How do drugs affect synaptic transmission?
In many ways
What is reinforced behavior likely to do?
Increase the likelihood of reoccurring
How are learned behaviors, experience, and memory instantiated in the brain?
As patterns of synaptic strength
what does the cell body contain?
nucleus - DNA coding production of proteins which serve functions within the cell
mitochondria - produce adenosine phosphate - energry
-both used in processes within dendrites, axon and terminal buttons
what are the supporting cells?
neuroglia
-half of brains volume
-central ns glia cells are astrocytes and oligodendrocytes
-peripheral ns glia cells are schwann and satelitte cells
what is the role of oligodendrocytes in the central nervous system?
form processes which produce the myelin sheath
how neurons work?
transmission - one direction, dendrites -> terminals
-dendrites & soma recieve input from previous neurons
-input changes potential of the neuron
-resting potential is the charge across the membrance at rest - membrane is polarized
-charge is caused by differences in ion concentractions and maintained by diffusive & electrostatic pressures
what is the process of depolarization?
what happens in the process of neural transmission?
NT molecule binds with a receptor -> opens ion channels and changes to the polarisation of the post synaptic membrane
-effects depend on ion channel opened: excitatory and inhibitory
what happens in neural processing?
- ion channels open and PSPs decay over time
- several EPSPs needed to meet threshold
- allows inputs from temporal and spatial summation -> IPSP & EPSPs CANCEL EO
what effect do the primary transmitters have?
-exicatory & inhibitory effects
-effects on post synaptic neuron is determined by the receptors present, the state of the neuron and the presence of other transmitter substances -> complex modulation of neural processing
what does glutamate do?
increases the membrance potential of the post synaptic cell
-is an amino acid produced by neurons metabolism
-activates types of receptors e.g. NMDA receptors control Na+ and Ca2+ gates
-Ca2+ involved in changes to AMPA receptors -> long term potentiation
what is GABA?
Gamma-AminoButyric Acid
-most common inhibitory transmitter
what does GABA do?
-decreases membrance potential of the postsynaptic cell
-prevents excessive excitation, inhibitory interneurons increase the flexibility of the nervous system
what does dopamine do?
-dopaminergic projections from substansia nigra and ventral tegmental area modulate activity in striate, limbic and contrical areas.
what does dopaminergic projections from substantia nigra cause?
modulates input areas of the basal ganglia
-degenerations causes parkinsons disease
what do dopaminergic projections from ventral tegmental areas modulate?
reward and learning,
changing behaviour to unexpected or highly salient stimuli
-stimuli associated are percieved as exciting or rewarding
what do drugs have to cross in order to have an effect?
the blood-brain barrier
-aids regualtion of brains chemical enivronment
what does drug action impact?
-precursor for AGO
-prevents storage of NT in vesicles
-inhibits release of NT (ant)
-stimulates release of NT (AGO)
-stimulates postsynptic receptors (AGO)
-blocks postsynaptic receptors (ANT)
what are examples of drug action?
cocaine - a catecholamine agonist, blocks reuptake of dopamine and norepinephrine
why are drugs addictive?
drug-taking behaviour is reinforced
-thru positive and negative reinforcement
-linked to release of dopamine in the nucleus accumbens - part of the mesolimbic dopaminergic system
what is negative reinforcement?
the removal of an aversive stimulus
(e.g. anxiety) in association with a behavior
why is temporal proximity important in addiction?
-both herion and morphine convert into dopamine in the brain but heriod is more addictive -> crosses the blood brain barrrier faster so is an effective reinforcer
what is learning?
the acquisition of information
what is memory?
the retention of information
what is operant conditioning?
Involves an association between a learned response and a stimulus
Reinforcement, through presentation of an appetitive stimulus, and successive refinements of a complex behaviour leads to strengthening of associations between a stimulus and a response (the behaviour)
what is hebbs rule?
a synapse that is repeatedly active when the post synpatic neuron is firing will become strengthened
-classical conditioning
how is operant conditioning shown within the brain?
Basal ganglia integrates perception and action planning
-> Destruction leads to failure of instrumental conditioning
what brain areas are included in reinforcement?
-main: ventral tegmentum and dopamine
how is the ventral tegmentum reinforced?
-electircal microstimulation of VT have reinforcing effects on behaviours -> projects to nucleus accumbens, prefrontal cortex, hippocampu and the amygdala - the **mesolimbic dopaminergic system **
-extracellular dopamine concentraction and FMRI activation increased in Nucleus accumbens after stimulation
how is dopamine reinforced?
-DA responds to the reward durinf the period when the monkey is learning a task -> reward is unexpected until performed reliably
-dopamine in nucleus accumbens surges in response to the predictive stimulus
-response of midbrain dopaminergic neurons represents a learning signal that codes for errors in prediction of reward
what is the mesolimbinc dopamine system involved in?
modulation of associative learning in general, not only that involving reinforcement
why is long term depression caused by low frequency stimulation of a synapse?
weakened neurons, after inputs which aren’t involved -> learning becomes insatiated
