S1: Information Processing in the Nervous System Flashcards
What does our parietal visual area do?
It encodes information about object movement
What does to cortical area in our brain do?
Process colour
What does the inferotemporal visual areas in the brain do?
Encode information about object identity
Explain how what we see is a reconstruction created by our brains rather than the copy of the real thing
What your eye detects is limited by its hardware, what your eye tells your brain is very selective, there isn’t a single representation of the image in the brain.
When we look at something, what we are seeing is our brains best guess of what is there - what our eye tells our brain in extremely selective.
What is synaptic integration?
- Neurones in the brain receive thousands of synaptic inputs from other neurones
- Synapic integration is the term used to describe how neurone ‘add up’ these inputs before generation of a nerve impulse or action potential
- Synaptic intergration therefore determines the firing pattern of an individual cell
What is convergence in neural circuit?
Single nerve cells generally receive convergent input from many presynaptic cells
What is divergence in neural circuit?
It is common for one nerve cell to synapse upon may other cells
Explain postsynaptic inhibition
It will release inhibitory transmitter holding the post synaptic membrane away from threshold (hyperpolarisation) which decreases the liklihood of action potentials firing
Explain presynaptic inhibition
Some inhibitory cells target the presynaptic boutens of other cells, suppressing their release of transmitter and hence very selectively changing the pattern of input onto the cells that they in turn contact. Presynaptic receptors can also be targeted selectively by therapeutic agents.
Explain postsynaptic excitation
Some of the presynaptic cells will release excitatory transmitter, by bringing the membrane potential of the postsynaptic cell closer to threshold, it increases the likelihood it will fire APs.
What is a modulatory role some inputs have?
It changes the excitability of postsynaptic cells without changing the information being processed
Modulators can control how nerve cells respond to specific inputs, without altering the information being processed - they change the strength of the message rather than the actual message.
What affects whether or not a post synaptic cell will fire an AP?
It depends upon the balance of excitation, modulation and inhibition –> synaptic integration
What are the characteristics of signals that specific pathways depend on?
- Precisely localised connections
- Fast synapses (ligand gated receptors)
- TIme dependent signals
- Highly selective responses (different cells respond to different events)
- Activity in these pathways is information rich
What are the characteristics of signals that modulatory pathways produce?
- Diffuse connectivity
- Slow synapeses (metabotrophic receptors)
- Signal timing is relatively unimportant
- Linked to changes in arousal and attention
Explain the primary visual pathway using specific and modulatory pathways
Specific inputs:
Retina –> Thalamus –> Primary Visual Cortex
Modulatory inputs:
Brainstem and forebrain
- When awake, ganglion cells in the retinal sense the light and transmits it to the thalamus that relays it to the cortex.
- When asleep, the modulatory signals to the thalamus (which usually boost signally from sensory cells) to stop firing so they become insensitive to their sensory inputs.
Instead, the thalamus produces its own burst of activity which the cortex receives and the cortex is now cut off from retinal signal and produces its own slow wave activity
