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dorsal and ventral stream of image recognition

3a. “it is moving toward me at high speed”. 2. impulse travels to occipital lobe. 3b. “it is a baseball”. dorsal and ventral stream of image recognition. dorsal stream. 3. “it is a spherical white object.”. 1. image enters from eyes. ventral stream. dorsal and ventral stream.

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dorsal and ventral stream of image recognition

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  1. 3a. “it is moving toward me at high speed” 2. impulse travels to occipital lobe 3b. “it is a baseball” dorsal and ventral stream of image recognition dorsal stream 3. “it is a spherical white object.” 1. image enters from eyes ventral stream

  2. dorsal and ventral stream • in occipital lobe, image is formed. • “It is a spherical white object.” • message then separates and moves to different areas for further interpretation • dorsal stream: (green area on diagram): interpret position and motion of object • “the object is moving towards me at high speed.” • the ventral stream (purple area) is in the temporal lobe • this is for object recognition • “it is a baseball.” • purple area also called fusiform gyrus • note that our labelling of the different lobes is artificial – many functions cross over these “boundaries” between the lobes

  3. Neuron Structure Dendrites(receive impulse) Cell Body(metabolic functions and “decisions”) Axon(carries impulse Away from cell body toward target) Schwann Cell(Insulates, protects, nourishes) Node of Ranvier(between Schwann cells; place for signal to jump) Synaptic Terminal(signal converted to chemical)

  4. Myelination and the Schwann Cells • Schwann cells wrap around the axon. They: • protect • nourish • insulate (electrically) the nerve cell. • They are full of myelin (fatty substance) • there are various demyelinating diseases….

  5. Myelination and the Schwann Cells • The myelin acts as electricial insulator. • As the cells grow, they wrap around the axon. • The more insulation there is, the faster the impulse will travel down the axon. • The more often a nerve is used, the more myelination occurs. • Therefore, the more you use it, the faster it becomes.

  6. Nodes of Ranvier • The areas BETWEEN the Schwann cells are called Nodes of Ranvier. • Insulation means action potential needs to be generated ONLY AT THE NODES (instead of along the entire length of the axon).

  7. Saltation (transmission by jumping) • The impulse can “jump” from one node to the next. This greatly increases transmission speed! This is called SALTATION -- (transmission by jumping)

  8. Saltation (transmission by jumping) transmission speed with NO Schwann cells: 0.5 m/s = 1.1 mph = about 3 seconds from big toe to brain transmission speed WITH Schwann cells: 120 m/s = 260 mph = about 0.0125 seconds from big toe to brain This is called SALTATION -- (transmission by jumping)

  9. axon terminals axon cell body dendrites

  10. 1 millisecond? probably less?

  11. 1 millisecond? probably less?

  12. water will carve grooves • next rainfall – water will tend to flow in the grooves ALREADY CARVED • this will make these grooves deeper • this will make it MORE LIKELY that water will flow here • the more times water flows in THESE grooves, the deeper they will become • this is like myelination • the more often a nerve is used -- • the more it gets myelinated and • the faster it transmits signals

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