10 Questions
Backpropagation. Is backpropagation considered biologically plausible? If so, why, if not, why not?
No. Backpropagation requires identical feedback connections for all feedforward connections.
Grid Coding. We can use fMRI to find grid-like coding in the human brain, because:
Depending on your direction (modulo 60 degrees) in a space, you will either traverse the activations or silences of all grid cells. So, we analyze fMRI responses contingent on movement direction.
Divisive Normalization population receptive field modeling. There are multiple parameters in the DN pRF model that represent constants in the numerator and denominator in its division:
Normalization constant (D), in the denominator, determines the amount of response compression. Activation constant (B), in the numerator, determines the amount of surround inhibition.
About divisive normalization: DN allows responses to be scaled to some background, for example it can rescale local neural responses to light based on the mean light level across the retina
True
About divisive normalization: DN can create winner-take-all suppression between neurons that represent different visual orientations, for example.
True
About divisize normalization: DN can implement the temporal difference learning algorithm for reinforcement learning, but fails to capture the dynamics of the Rescorla-Wagner model
False
About divisive normalization: DN is one of the basic ingredients of recurrent neural network architectures, without which backpropagation-through-time cannot be performed.
False
Single-layer perceptron. There is a specific operation that a single-layer perceptron cannot perform. Which?
The XOR operation
Grid Coding. How do responses in Entorhinal cortex (EC) lead to place cell responses in Hippocampus?
Grid cells form a Fourier basis for the representation of space: place cells could be created through a linear combination of grid cell responses.
Replay. A population of place cells:
Can replay a sequence of events (a route) faster than it happened in actual life so that memory consolidation processes connect distant cortical representations.
Study Notes
Backpropagation and Biological Plausibility
- Backpropagation's biological plausibility is a topic of debate, with some arguing for or against it.
Grid Coding
- fMRI can be used to find grid-like coding in the human brain.
- Grid coding in the Entorhinal cortex (EC) leads to place cell responses in the Hippocampus.
Divisive Normalization
- DN is a mechanism that allows responses to be scaled to a background, such as rescaling local neural responses to light based on the mean light level across the retina.
- DN can create winner-take-all suppression between neurons that represent different visual orientations.
- DN can implement the temporal difference learning algorithm for reinforcement learning, but fails to capture the dynamics of the Rescorla-Wagner model.
- DN is a crucial component of recurrent neural network architectures, enabling backpropagation-through-time.
Single-Layer Perceptron
- There is a specific operation that a single-layer perceptron cannot perform.
Replay
- A population of place cells is involved in the replay process.
Explore the concept of backpropagation and whether it is considered biologically plausible. Learn about the reasons why backpropagation might be seen as biologically plausible or not.
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