Linking Senses+Behaviour to Memory Flashcards
What is the Drift Diffusion Model?
- Framework used to describe the decision making process regarding neuroscience in noisy/ambiguous environments
What are the components of the drift diffusion model?
- Drift rate: Rate at which evidence accumulates in favour of one decision over another
- Threshold: How much evidence is needed to make a decision?
- Noise : Random fluctuations in accumulation of evidence
- reaction time: The gap in time from when the evidence starts accumulating to when the decision is made
What is the other title for ‘Normal distribution’?
Gaussian distribution
How does reaction time plot on a graph?
1/reaction time gives a normal distribution which implies the varying factor is rate of evidence accumulation
What experiments can be used to test reaction time in drosophila and what were the results?
- Odours in two chambers one is attractive one is repellent - quick reaction time
- When the odours are more complex and more ambiguous then the decision making takes longer
- Rightward skew in reaction time
Explain reaction time experiments in mice
- Mouse pokes its nose in the odour port – when it hears a buzz, it has to stop sniffing and choose a water port based on which odour it smelled.
- Reward only for going to the correct water port.
- If mouse’s odour sampling time is cut short by the buzzer it makes less accurate decisions
How can the mouse reaction time experiments be explained by the drift diffusion model?
- Accumulating lots of evidence when the buzzer allows a long time , you make the right decision
- If you don’t allow enough time to reach the full decision threshold you are likely to make a mistake (not gathering enough evidence)
When is the threshold for evidence accumulation set lower?
Under certain conditions where there is a priority on speed not accuracy e.g. in danger
What is the physical implication of drift diffusion?
Ramping up neural activity
Explain the physical implications of the drift diffusion model including motor command neurons in monkeys brain
- Motor command neurons exhibit increased activity when monkey is ab to move its eyes to the right (opposite for the left)
- Before the monkey makes a decision about which direction to move its eyes, neuron activity gradually increases (evidence accumulation)
- The rate of this ‘ramping’ depends on the strength of evidence accumulation (higher/lower drift rate)
- Neuron reaches peak activity around 70ms before decision, suggests consistent timing despite stimulus strength
- Once threshold is reached, decision is made implying evidence for the neuron ‘causing’ the decision
How are Kenyon cells related to decision making?
- Kenyon cells store olfactory memories
- Fly mutant, FoxP takes abnormally long to decide between two odours
- Due to Kenyon cells being ‘leaky due to excess K+ channel expression
- This slows down their rate of evidence accumulation