Lecture 18 Flashcards
what is color after image
Activated by complimentary colors. Bleaching opsins in eye allows cones and cells to be activated by complementary colors
how do ventral stream and dorsal stream vary in visual information and receptive fields
ventral stream is less specific about site and more specific about shapes
dorsal stream is less specific about shape and more specific about place
v2
like v1 but illusions and textures too
v4
spatial frequencies, complex shapes with colors
v5
motion
subject df damage to ventral stream
reaching and grasping appropriately but cant name object
subject df damage to dorsal stream
can name the object but can’t grasp and use it
where are motor neurons located
ventral horn of spinal cord
what is the movement signal pathway
Movement signal from the brain goes to one segment of spinal cord to synapses in dorsal horn, sending axons out of the spinal cord into the same nerve that carries sensory information in the end on muscles, will make synapses on muscle fiber.
proprioception
sensory information about body movement and position of limbs and joints
what are the two major sensory feedback receptors
muscle spindles and golgi tendon organs
muscle spindles
in muscles to monitor stretch
golgi tendon organs
attached to tendons and monitor tension in tendons due to muscle contraction. Activated by strong force, help prevent damage to muscle or tendon
what do the tiny muscle fibers inside muscle do
report on tension on muscle. Reset to be shorter or longer due to tension
primary and secondary sensory endings
Response rate, adaptation rate, sensitive to
Primary- respond rapidly, adapt quickly, and sensitive to rate of change
secondary- respond slowly, continue to fire with stretch, sensitive to continuous force. both are adjustable
Spinal reflexes summary
ventral spinal cord axons release Ach on muscle fibers to cause contraction. Axons carry sensory information about stretch and tension from tendons to neurons in the spinal cord. From these spinal cord neurons, reflexive signals can be sent back to muscles. These neurons also send APs to the brain
the primary motor cortex
frontal cortex intention, in front of central sulcus, communicating with sending movement signals to muscles associated with predictable parts of body, lots of neurons for hands and lips
the pyramidal system
axons from motor cortex project down the pyramidal tract to connect to primary motor neurons in the spinal cord. Axons coming from left side of motor cortex cross and go to right side of spinal cord and vice versa. Info going down and coming up cross over
directional selectivity
neurons in motor cortex are broadly turned and contribute ti movement directions
population vector
the summed activity of many neurons, only movement can be coded by a population vector
What is the relevance of population vectors to human machine interface?
Picking up enough signals in motor or pre motor cortex could be used to compute a population vector (an intention) that then could feed into a robot or a prosthetic device to generate movement
explain how processing in motor cortex is plastic
short term training in a motor skill increases the ease with which motor cortex can generate the necessary movements
supplementary motor area (SMA)
initiating planned sequences of movement
premotor cortex contains
contains mirror neurons that have action potentials associated with intending to make a movement or with seeing it (much less activated by autism)
