What is connectomics
Connectomics is the production and study of connectomes, which are comprehensive maps of connections within an organism's nervous system.
How does an axon know how /where to grow?
Axons are attracted/repelled by a other molecules
Why does a baby has a lot of activity in the cortex although does not have mature organs?
spontanious activity by neuro circuits
What do calcium pulses mean (retinol waves in still blind baby mice)?
spontaneous active neurons
How does activity influence connectivity and vice versa?
What are Homeostatic mechanisms?
preserving connections
Nomenclature long term mechanisms of placicity
Activity only knows the pre and post neuron
What is Hebb’s postulate and the findings from Hubel and Wiesel?
‘Out of sync, out of link’
First experimental work in hippocampus: Plasticity induced by firing rate. What was the result of different frequencies of the firering stimulation?
black: stimulated, white: unstimulated
Plasticity in a feedforward network. What are we interested in?
Change in the weights
What are the rules in Rate-based plasticity?
Issues:
Can lead to instability without normalization.
Solutions include subtractive and divisive normalization.
What influences the Hebbian plasticity?
Hebbian plasticity, the connections of the pre and post synapse, can modify the weights based on the correlation/covariance on the inputs
-> Covariance rule (is unstable)
What are Normalization Constraints? What types are there?
Regularization for weights. Substractive and divisive
What is the BCM Rule (Bienenstock-Cooper-Munro)?
Plasticity rule changes based on postsynaptic activity threshold (metaplasticity).
Threshold “slides” based on activity history.
Explains adaptation to environmental changes (e.g., light/dark exposure in visual cortex).
What does STDP stand for?
Spike-timing-dependent plasticity
What is Spike-timing-dependent plasticity (STDP)?
Spike-timing-dependent plasticity (STDP) is a biological process that adjusts the strength of synaptic connections between neurons based on the relative timing of their action potentials (or spikes). It is a temporally sensitive form of synaptic plasticity
Spike-timing dependent plastiity (STDP) experiment
fireing is the same, timing is different rechts: depression
What are plasticity factors?
we focus on relative timing
Various experimental results for plasticity rules
curves look different, different in brain region and cell types
Bi and Poo rule
LTP: Long term potentiation
LTD: Long term depression
Bi and Poo systematically mapped the time-dependent curve relating the order of pre- and postsynaptic spikes to the magnitude and direction of synaptic change in cultured hippocampal neurons. Their work demonstrated that small differences in spike timing—on the order of tens of milliseconds—could induce either long-term potentiation (LTP) or long-term depression (LTD).
What is Triplet STDP?
Triplet (and not pairwise) STDP can explain data where pairs of spikes are repeated at different frequencies p
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