L5, Learning Neural Code

Question 1

What are the three different types of brain networks? How do they work?

Answer 1

Local: small generic processing units
Global: aggregate related processes in units
Large-scale connectivity: intra-cortical pathways (an information highway

Question 2

How does encoding in the brain work?

Answer 2

It is task-specific (distinguishes differences by finding identities). Extract categories identify and encode essence using identifying properties (filters), measuring amount is mainly checked through the eyes. Managing capacity refers to compression the distribution of code.

Question 3

How does light get processed in the retina?

Answer 3

The sparkle of light enters the retinas photoreceptors, either rods (luminance selectivity) or cones (colour selectivity). the information is collected from the photoreceptors by interneurons such as bipolar, horizontal and amacrine cells.

Question 4

How does neural computation work?

Answer 4

It can be done through summation or subtraction. Summation: Information from sensors being combined through one-to-one (direct representation) or many-to-one (convergence). There is a graded response, resolution is decreased but sensitivity is increased.

Subtraction: integration with different signs where responses from neighbouring regions are subtracted (lateral inhibition), creating opponency between different signals

Question 5

What is excitatory and inhibitory?

Answer 5

Excitatory: Activation
Inhibitory: deactivation

Question 6

What is a receptive field?

Answer 6

The location in time and space where the presence of a stimulus can produce a change in the response of a neuron. Two-dimensional receptive fields are neural computations in 2 dimensions.

Question 7

What is contrast?

Answer 7

Relative difference in stimulus intensity between a bright and a dark region of visual stimulus.

Question 8

What is luminance?

Answer 8

in terms of encoding, luminance borders are where opponency enhances perceived contrast since information is transmitted at the border. Equal luminance is when excitation and inhibition cancel each other out

Question 9

What are spatial filters?

Answer 9

size tuning. In general, filters are responsible for merging properties.

Question 10

What is spatial frequency?

Answer 10

the number of cycles of a periodic pattern per degree of visual angle