Chapter 8: The Tools of Thought

• Feedback and hierarchies of cortical circuits
• If our brains is the same as a mammal brain, just larger, how does it gain new abilities?
• Feedback Circuits
• The cortex is wired both from sensory systems to something else and from the cortex to the sensory systems.
• Can re-experience sensations without the actual stimulation.
• Can rearrange and examine the steps that are taken.
• Steps of Recognition
1. Initial Activation
• The flower example
• Sensory impression
• Contains more data than the brain can process
2. Learning
• Group different flowers into categories
• Group all flowers into plants
• Generalizing and differentiating
• Generalizing: flowers, plants, commonalities
• Differentiating: what makes a rose different from a daisy
3. Feedback
• Once a category is established, feedback suppresses differences
• Thalamus is involved in suppression
• Effect is that the cortex only sees the common aspects in the first sensation.
• Next sessions, the differences start to arise.
• Thus an instantaneous experience becomes a sequence of experiences.
• Sequences
• In addition to breaking a single sensation into multiple steps as per categories.
• Flower petal example: start with one petal, look for the next.
• Validate a possibility
• What One Brain Area Tells Another Brain Area
• Old tools are relatively crude
• EEG, PET scan, CAT scan
• Includes fMRI
• What's in an Image?
• Description of how fMRI works.
• Putting it Together: From Generalists to Specialists
• Fallacy: the wheels moving the car
• Something else actually turns the wheels
• Controversy over recognition
• Grandmother cells
• Specific cells encode information.
• Distributed
• populations of cooperating neurons represent information
• Memory Construction
• They advocate a hybrid approach between Grandmother cells an a distributed system.
• Distributed in the sense that no one neuron encodes a particular memory
• "Grandmother" like in that neurons do exist that are very highly tuned to a particular type of image
• A sort of "shared grandmother cell" approach.
• Building High-Level Cognition
• Large brains lead to long cortical processing areas.
• Libraries and Labyrinths
• Memories are stored as routes through the brain instead of one location that has all the data.
• Scavenger hunt analogy
• Grammars of the Brain
• The way the brain works is similar to a linguistic grammar
• There are rules that govern what sequences of thoughts are allowable
• Specific pathways store individual memories.