Chapter 6: How the Cortex Works

• Cortical columns: upward flow is direct, downward flow is less so.
• Up information: synapses are close to cell bodies.
• Down information: synapses are typically farther from cell bodies.
• Figure 12 (Dalmation) illustrates the up and down flow.
• Perception and behavior are closely related. Motor behavior also is a hierarchy of invariant representations.

Other Brain Components

• Thalamus: allows delayed feedback which enables sequences to be learned, perhaps provides an alternate pathway to allow us to attend to details that we normally wouldn't. The thalamus is essential to living.
• Hippocampus: stores memories of events and places. The hippocampus is essential to the formation of new memories. It sits "above" the cortex at the top of the pyramid.
• Basel Ganglia: a primitive motor system. Somewhat superceded by cortex.
• Cerebellum: learns relationships of events. Somewhat superceded by cortex.

Brain Processing (e.g. L1)

• Track where we are in a song: thalamus delay, column inputs.
• Know name of song: internal L1 activiation.

Questions About Cortex Operation (p. 147)

1. How does a region of cortex classify its inputs? A column inhibits nearby columns.
2. How does it learn sequences of patterns? Layers can be activated via learning from above to enable predictions.
3. How does it form a constant pattern or name for a sequence? Send changing data up if you don't have a name. Send constant data up via inhibition if you do.
4. How does it make specific predictions? Combination of bottom-up inputs and top-down predictions.

Learning

• Hebbian Learning: when 2 neurons fire, strengthen the synapses between them.
• Learning tasks: classification and sequence building. A sequence is a pattern that is contiguous in space or time.
• Over time, simple representations move down, enabling higher regions to learn more complex and subtle patterns.
• Expertise. The more you know, the less you remember.