Are the things we see 100% real?
What you see is a reconstruction of what MIGHT be out there, it's your brain's best guess of all that incoming neural activity. Neural activity has meaning.
Which parts of the brain encode information for:
i) object movement
iii) obejct identity
- movement - parietal visual areas
- colour processing - cortical area
- identity - inferotemporal visual areas
What determines the firing pattern of an individual cell?
What is pre-synaptic inhibition and its effects?
When an inhibitory neurone terminates on a pre-synaptic bouton of an excitatory neurone. - if excitatory alone activates -> EPSP - if inhibitory activates (on excitatory) as well -> smaller EPSP
What 3 types of neuronal inputs are there on post-synaptic boutons on a dendrite?
- inhibitory - excitatory - modulatory all determine whether an action potential is triggered
What is convergence?
many presynaptic cells converge onto one single nerve cell (or fewer) to give input.
What is divergence?
one nerve cell to synapse upon many other cells. The postsynaptic target could be within a single structure or widely separated.
What is the role of modulation?
Modulatory inputs use metabotropic receptors, typically change size of response without changing message. They control the state of the system.
What is an example of modulation within the primary visual cortex?
Serotonin -> fewer action potentials (at diff times) ACh -> more action potentials (at diff times) Changes the VOLUME - not on-off like excitatory or inhibitory.
What is meaningful neural activity associated with?
SPECIFIC pathways - eg. motor, sensory, cognitive etc.
What do specific pathways depend on, in terms of signals?
- fast (ligand-gated) - precisely localised (topographic organisation) - time-dependent signals - highly selective responses - information-rich activity
What are some features of modulatory pathway signals?
- slow (g protein couple) - diffuse (not localised/precise) - not time-dependent - linked to changes in arousal (sleep-wake cycle) - linked to changes in attention - linked to changes in mental state
What happens when we are awake?
Thalamic cells relay sensory info to cortex - transmits signal as it is.
What happens when we are asleep?
Thalamic cells become insensitive to their sensory input - withdrawal of modulatory (sensory) input leads to spontaneous bursts of activity being fired by thalamic cells.