文档介绍：会计学
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视觉与大脑2VisualBrain2017s
Outline (Ch. 3 and Ch. 4)
Neurons, Receptive Fields & Human Brain
From Retina to Visual Cortex
Primary Visual Cortex (V1)
Secondary Visual Cortex (V2) - optional
Outline (Ch. 3 and Ch. 4)
Neurons, Receptive Fields & Human Brain
From Retina to Visual Cortex
Primary Visual Cortex (V1)
Secondary Visual Cortex (V2)
Major Division of Human Brain
Neurons and Synapses -optional
Receptive Fields
Major Division of Human Brain
Visual Cortex
Neurons
While the fundamental structural unit of the brain is the neuron, the currency
of the brain is the action potential or spike, which travels at conduction
velocities from 1 to 120 meters (3 to 380 feet) per second. If an insulating myelin sheath (signal booster) is wrapped around the axon then the action potential propagates by “jumping” between gaps in the myelin sheath, otherwise the action potential decays exponentially.
Synapses
Synapse. Each neuron receives inputs via its dendrites. If these inputs are sufficiently large then an output in the form of an action potential appears in the neuron’s axon. This causes chemical neurotransmitter to be released at the synapses to other neurons. Courtesy Creative Commons.
Backward retina
The light rays that contribute to the retinal image have to pass through layer of nerve fibers and the blood vessels before reaching the light-sensitive photoreceptors.
Receptive Fields -Tilting the Retina
Photoreceptors
(pixel array)
This receptor is
shared by two
ganglion cells
Cables show connections for
only three receptive fields
Ganglion cells
each photoreceptor can belong to about ten receptive fields
Receptive Fields –Mexican Hat?
Ganglion cell receptive fields. (a) On-center/off-surround. (b) Off-center/on-surround. (c) Three-dimensional graph showing the sensitivity to light spots placed in different regions of the receptive field of a cell with an on-center receptive field. The spike in the middle shows where light excites the c