https://vimeo.com/117815404

• Wrap-up on vision
• Biological basis of learning & memory
• Blog post 3/papers due today

• Quiz 4, review Exam 3 on Fri
• In-class lab next Mon
• Review for Exam 4 next Wed
• Exam 4, Mon 12/11, 12:20-2:10 pm in 302 Boucke

• Retinal ganglion cells
• 2nd/II cranial (optic) nerve
  • Optic chiasm
• Lateral Geniculate Nucleus (LGN) of thalamus (90% of projections)

• Hypothalamus
  • Suprachiasmatic n.
• Superior colliculus & brainstem

• 6 layers + intralaminar zone
  • Parvocellular (small cells): chromatic
  • Magnocellular (big cells): achromatic
  • Koniocellular (chromatic - short wavelength?)
• Retinotopic map of opposite visual field

• Via optic radiations
• Primary visual cortex (V1) in occipital lobe

• Fovea overrepresented
  • Analogous to somatosensation
  • High acuity in fovea vs. lower outside it
• Upper visual field/lower (ventral) V1 and vice versa

• 6 laminae (layers)
  • Input: Layer 4
    • ~80% is from other cortical areas!
  • Output:
    • Layers 2-3 (to cortex)
    • Layer 5 (to brainstem)
    • Layer 6 (to LGN)

• Columns
  • Orientation/angle
  • Spatial frequency

• Columns
  • Color/wavelength
  • Eye of origin, ocular dominance

• Larger, more complex receptive fields
• Dorsal stream (where/how)
  • Toward parietal lobe
• Ventral stream (what)
  • Toward temporal lobe

• What is it? (form perception)
• Where is it? (space perception)
• How do I get from here to there (action control)
• What time (or time of year) is it?

• Functional segregation/specificity
• Topographic maps
• Variable resolution

• 1e11 neurons
• 1e3 synapses/neuron
• 1e14 synapses or 1.25e13 bytes
• 1e9 gigabyte, 1e12 terabyte, 1e15 petabyte

http://www.scientificamerican.com/article.cfm?id=what-is-the-memory-capacity

• Learning
  • ?
• Memory
  • ?

• Learned?
• Remembered?

• Learning
  • Change in perception, thought, behavior, emotion over time
• Memory
  • Information derived from past experience that influences current behavior

• Stored in sequences of binary digits (bits): {0,1}
• Stored by address: "011000" stored in "1110000"
• Single characters, images, sounds, data stored as sequences of bits.
• Volatile vs. non-volatile
• Computers have separate memory stores; brains store info everywhere

• Changes in patterns of neural activity
• Changes in patterns of connectivity
  • New synapses
  • Changes in synaptic strength (+/-)

When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficacy, as on of the cells firing B, is increased. (Hebb, 1949, p. 62)

Neurons that fire together wire together. (Lowell & Singer, 1992, p. 211).

• N-methyl-D-aspartate receptor (NMDAR)
• 'Coincidence' detector
  • Sending cell has released NT
  • Receiving cell is/has been recently active

• Chemically-gated AND
  • Ligand- (glutamate/aspartate + glycine) gated
  • Sending cell active
• Voltage-gated
  • \(Zn^{++}\) or \(Mg^{++}\) ion 'plug' removed under depolarization
  • \(Na^+\) & \(Ca^{++}\) influx; \(K^+\) outflux
  • Receiving cell responds

• Associate (link)
  • Concept A -> Concept B
  • Neuron A -> Neuron B

• Trump
• Duck
• Draper

• Memantine (Alzheimer's Disease treatment) blocks NMDAR
  • Controls over-activation and \(Ca^{++}\) excitotoxicity?
• Implicated in effects of phencylidine (PCP)
  • Link to glu hypothesis of schizophrenia?

• Ketamine is NMDA receptor antagonist
  • anesthesia, sedation pain relief
  • possible short-term relief for depression
• Analgesic effects of nitrous oxide (laughing gas; NO)
• Ethanol inhibits (Ron et al., 2011)

• Long-term potentiation/depression
• Disorders of learning & memory