What time scales are related to circadian timing?
endogenous (i.e. self-generated) rhythm which is about 24 h long ⇒ circadian
entrained by day-night cycle
Name the brain structure that is crucially involved in circadian timing in mammals.
in mammals: suprachiasmatic nucleus (SCN) in the hypothalamus above the optic chiasm
SCN receives direct input from retina
SCN generates circadian rhythm by gene expression cycle
Explain the principle of circadian transcriptional circuits.
Which duration ranges are relevant to interval timing?
seconds to minutes
Name psychophysical tasks for interval timing and explain briefly.
What does Weber’s law state?
discriminability between two nearby stimuli depends on the ratio between their intensities, not on their absolute magnitudes.
What is the regression effect in magnitude estimation?
systematic over/underestimation
over a range of stumuli
small stimuli overestumated, large stimuli underestimated
Time reproduction (Magnitude estimation)
The likelihood of measurement M given a stimulus S is described by the conditional probability P(M | S). How could you determine P(S | M)? Name the method you are using and give its mathematical formulation.
Bayesian explanation of magnitude estimation
What is the difference between dedicated and intrinsic models of timing?
Definition: Timing is handled by specialized neural circuits or "dedicated clocks".
Analogy: Like a stopwatch — a separate mechanism explicitly tracks time.
Definition: Timing emerges from the natural dynamics of neural networks involved in perception or action.
Analogy: Like watching sand flow in an hourglass — time is inferred from the changing state of a system.
Name models of time perception.
Bayesian inference
statistical description of the computations involved in timing
Pacemaker-accumulator
implementation of the computations; (dedicated)
Population clocks
realization in the brain; mechanistic description; (intrinsic)
Explain the pacemaker-accumulator model.
What are population clocks?
read out time based on changes in the neural population
Describe the components of a state-dependent network
A state-dependent network is a neural system whose response depends not just on external input but also on its internal state at the time the input is received. This internal state evolves over time due to the network's own dynamics — making such networks ideal models for timing, working memory, and sequence processing.
Neural trajectories track time ⇒ time as intrinsic property of network activity
⇒ Population clocks
How can a state-dependent network be used to explain time processing in the brain?
= Timing with a neural population
the brain goes through different internal states
In a state-dependent network, each moment in time corresponds to a unique configuration of neural activity (i.e., a point in high-dimensional state space).
As the network evolves, its trajectory through this state space effectively acts as a "clock", with each state marking a specific elapsed time.
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