Samenvatting
Summary Lectures network models, representation and consciousness
- Vak
- (5234NMRA6Y)
- Instelling
- Universiteit Van Amsterdam (UvA)
Lecture notes and summary
[Meer zien]Voorbeeld 4 van de 62 pagina's
Voorbeeld 4 van de 62 pagina's
In winkelwagengesponsord bericht van onze partner
Gekoppeld boek
Titel boek:
Auteur(s):
- Uitgave:
- ISBN:
- Druk:
Verkoper
Volgen
Voorbeeld van de inhoud
Network Models, Representation and ConsciousnessLecture: Recap on Cellular Neurophysiology, reducing the neuron, Meijas 2
Lecture: Learning representations: Perceptrons & error backpropagation, Bothe 6
Lecture: Recurrent networks and auto-associative memory, Pennartz 10
Lecture: Ch 4 & 5: Networks, consciousness and panpsychism, Pennartz 15
Chapter 4 21
Chapter 5 23
Lecture: Models of Reinforcement Learning, Pennartz 24
Lecture: Predictive coding models: perceptual inference and learning, Lee 30
Lecture: Models of neural dynamics (advanced), Meijas 34
Lecture: Ch.6: Which brain structures are involved in consciousness, Pennartz 38
Chapter 6 44
Lecture: Spiking neural networks and predictive coding, Bohte 45
Lecture: Ch.8,9: Requirements and Mechanisms for conscious representation,
Pennartz 49
Chapter 8 57
Chapter 9 57
Lecture: Ch.10,11: Multi-level theory and philosophical implications, Pennartz 57
Chapter 10 57
Chapter 11 57
1
,Lecture: Recap on Cellular Neurophysiology, reducing the neuron, Meijas
computational modeling: testing, insight and predication
Hopfield model: understand different types of memory
- relies on properties of parallel-distributed processing
- Von Neumann: central processing unit, instructed by a programmed sequence
- robust and fault tolerant
- high learning capacity and flexibility
- robust to noise, and capable of handling fuzzy and incomplete information
- massive parallelism: many simultaneous operations → high speed of computation
Membrane potential: Membrane potential arises from a separation of positive and negative
charges across the cell membrane (-60 to -80 mV)
- rapid electrical signaling → you only have to open the gates
Inside Outside Eq pot
Na+ (sod) 50 440 +55mV
Cl- 52 560 -60mV
K+ (pot) 400 20 -75mV
A- 385 ~0 --
Ca2+ 0.001 2 120mV
Equilibrium potential (=reversal potential): the potential at which the electrical driving
𝑅𝑇 [𝐴]𝑜𝑢𝑡
force equals the chemical (diffusional) driving force → Nernst equation 𝐸𝑘 = 𝑧𝐹
𝐼𝑛 [𝐴]𝑖𝑛
Electrical driving force: depends on membrane potential (+ions attracted to inside)
Chemical driving force: depends on concentration difference of ion across membrane
2
,With multiple ion species:
- A: resting state
- B: both chemical and electrical driving forces go inside the cell → increasing the
number of positive charges
- C: the driving force of K+ goes to the outside of the cell
𝑅𝑇 𝑃𝑘 *[𝐾]𝑜𝑢𝑡 𝑃𝑁𝑎 *[𝑁𝑎]𝑜𝑢𝑡 𝑃𝐶𝑙 *[𝐶𝑙]𝑖𝑛
- 𝑉𝑚 = 𝐹
𝐼𝑛( 𝑃𝑘* [𝐾]𝑖𝑛
+ 𝑃𝑁𝑎*[𝑁𝑎]𝑖𝑛
+ 𝑃𝐶𝑙*[𝐶𝑙]𝑜𝑢𝑡
)
ion channel
- in the absence of the ionic gradient: the current-voltage plot is linear
- for single channel: for every ion channel there is a relationship between the current
and the voltage
- groups as electric circuits: different electrical properties with different ion channels.
different types of channels in parallel: different equilibrium potentials → different
battery-conductance combinations
capacitance: store charge in the cell → any input will not change the membrane potential
directly.
- low-pass filter: if there are lots of fluctuations → the capacitance will smooth things
out
the voltage changes slowly: charge (delta Q) / capacitance (C)
measure the voltage channel across the membrane: Vm(t) = Im *Rin (1 – e-t/tau)
time constant: tau= RinC
3
, voltage is not uniform across the membrane:
- if electrical current is injected:
- it spreads laterally because of low cytoplasmic resistivity
- current leaks through membrane depending on specific membrane resistance
- voltage will decay with distance
Potassium conductance involved in AP:
- Grows with stronger depolarization
- Does not inactivate
- Separate effects from driving force (Vm-Ek) and conductance
Sodium conductance involved in AP:
- Grows with stronger depolarization, but levels off;
- Inactivates after ~2 msec
- 3 states postulated by Hodgkin-Huxley: Active - inactivated - de-inactivated
(activatable)
time course
1) Initial depolarization needed
2) Na+ channels open
3) Further depolarization of membrane
4) More Na+ channels open → more depolarization (positive feedback loop, regenerative)
5) K+ channels start to open: repolarizing effect
6) Na+ channels inactivate
7) K+ conductance outlasts Na+ conductance: hyperpolarization
8) Refractory period → impossible or very difficult to excite membrane
- two things need to happen at the same time to reach hyperpolarization;
- sodium (Na) channels close
- potassium (K) channels open
The neuron as a computational element: McCulloch-Pitts
- tells if a neuron is going to spike or not (use them in networks)
- Synaptic weights (strengths) from pre (1,2 or 3) to postsynaptic cell (i)
- synchronous assembly of ‘neurons’ is capable of universal computation if the
synaptic weights are chosen suitably
4
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper isisvanechtelt. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €7,49. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 62890 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen