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1.4 Neurotransmitters + their effect on behaviour Cheat Sheet by

- Synapse (how these relate to excitatory and inhibitory neurotransmitters) - Definition of agonist and antagonist - Explanation of the role of acetylcholine in memory - Antagonist/agonist: Antonova et al (2011) Acetylcholine in memory formation - Use of smart drugs - Role of culture in the formation of memories

Antonova (2011)

 
Aim:
wanted to see if scopol­amine affected hippoc­ampal activity in the creation of spatial memory.
Procedure
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20 healthy male adults (mean age 28). were injected with either Scopol­amine or a placebo
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Pts were put into an fMRI and scanned whilst playing the "­Arena task." A virtual reality game where the goal was to navigate around an "­are­na" to reach a pole.
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After learning where the pole was located, the pts were told to actively rehearse how to get to the pole in the arena.
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Repeated measures design - pts returned 3/4 weeks later and redid the test - receiving the opposite treatment
Research method
Experiment
IVs
Scopol­ami­ne/­Placebo
DV
fMRI - Brain activity
Antagonist
Scopol­amine
Agonist
Acetyl­choline
Findings
1) When pts were injected with scopol­amine, they demons­trated a signif­icant reduction in the activation of the hippoc­ampus compared to when they received a placebo.
2) They were also more accurate in the placebo group.
Counte­r-a­rgu­ment: Kulkofsky

Neuron

Neurons are cells within the nervous system that transmit inform­¬≠ation to other nerve cells, muscle, or gland cells. Most neurons have a cell body, an axon, and dendrites.

Explain synaptic transm­ission

Synaptic transm­ission is the biological process by which a neuron commun­icates with a target cell across a synapse. Chemical synaptic transm­ission involves the release of a neurot­ran­smitter from the pre-sy­naptic neuron, and neurot­ran­smitter binding to specific post-s­ynaptic receptors.

Excitatory + Inhibitory

Neurot­ran­smi­tters have either an excitatory or Inhibitory effect of the neighb­oring neuron.
= Excitatory neurot­ran­smi­tters are released into an excitatory synapse causing a neuron to fire, leading to an action potential, this produces stimul­ating effects on the brain.
E.g E.g. Acetyl­choline when in excitation it makes the receiving neuron positively charged and more likely to fire and is thought to be involved in the process of memory consol­ida­tion.
 

Neurot­ran­smitter

Neurot­ran­smi­tters are electr­och­emical messages that result in a vast array of behavi­ours. The effects of Neurot­ran­smi­tters can be amplified or reduced.

*Human behaviour is highly complex, thus trying to determine cause and effect is difficult to prove.

Neurot­ran­smi­ssion

Describe Neurot­ran­smi­ssion

Neurot­ran­smi­ssion is the process of nerve cell commun­ica­tion. The neurons that are interc­onn­ected commun­icate with each other by releasing chemicals called neurot­ran­smi­tters into small gaps between the two nerve cells call the synapse gap (see above).

The process of electr­och­emical transm­ission starts in the dendrites that branch out from the cell body and these receive incoming impulses from neighb­oring neurons.

The impulse passes down the axon as action potential, down to the terminal buttons, containing synaptic vesicles (tiny sacs) filled with neurot­ran­smi­tters which are released into the synapse.

A released neurot­ran­smitter is available for the synapse gap for a short amount of time during which it may be destroyed, pulled back into the presyn­aptic axon terminal through reuptake (reabs­orp­tion), or reach the postsy­naptic membrane and bind to one of the receptors on its surface.

If the neurot­ran­smitter bind onto the receptor on the postsy­naptic neuron, this process changes the membrane potential and so contri­butes to activating an electrical pulse in the postsy­naptic neuron. Here the chemical mechanism becomes electrical again.
 

Conclu­sions (Antonova (2011)

It appears that acetyl­choline may play an important role in memory consol­idation - why do you think this?
Becausethe hippoc­ampus was activated - so what??
It was demons­trated that neurot­ran­smi­tters themselves can be affected by other chemicals - why?
Because drugs interfere with the way neurons send, receive, and process signals via neurot­ran­smi­tters.
= Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurot­ran­smitter in the body. This allows the drugs to attach onto and activate the neurons.

Antagonist

Is a substance that fits into a receptor site on the postsy­naptic neuron, preventing the neuron from firing by blocking access to it.

Agonist

Looks like the neurot­ran­smitter and fits in the receptor site but it amplifies the behaviour. The reaction can be excitatory or inhibitory.

= Drugs are exogenous agonists.

= Neurot­ran­smi­tters are endogenous agonists.
 

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