Week 4 Flashcards
(25 cards)
T/F: Rats have worse peripheral vision than humans, but better binocular vision.
- FALSE
- Rats have better peripheral vision, but worse binocular vision
What’s the benefit of rats being able to see more height-wise?
- Better at identifying predators from above
What are some of the major characteristics of rat eyes?
- Dichromates (don’t have red cones, see limited colour)
- Cone density is also lower compared to humans
- No fovea
- Also contain an LGN and a V1
T/F: Rats don’t have ocular dominance columns.
- TRUE
What are the three potential uses of having rats tuned to identify UV light?
- Can be used for urine detection. Can detect conspecifics with UV light
- Can also be used for body detection as the underbelly of rats can reflect UV light, but predators wouldn’t identify it
- Can be used for twilight vision as there is an abundance relative to visible light in the twilight hours
What’s the measure of visual acuity that is drastically different between rats and humans?
- Cycles per degree = How many lines you can distinguish in a single degree of your visual field
- Humans have 30 cpd
- Rats have 1.0-1.1 cpd
What was the purpose of the virtual optomotor system?
- A non-invasive way of assessing the visual acuity of rats
- Place rats in cube surrounded by monitors, simulates the presence of a cylinder around them
- Project a sign grading on the cylinder with variation in the cpd
- Virtually spin the cylinder and the rat will start to track the sign grading
- At a certain point when the bars are very close together and the rat stops tracking at which point you can determine the rat’s visual acuity.
What’s the physiology of rat hands that allow them to perform skilled movements?
- Have four digits
- The first digit (thumb) has a nail
- This one can be moved medially to aid in precision grasping (ex. a scissor grasp)
What is the skilled reaching task?
- Used to assess skilled movement
- Can be broken down into 10 different steps
What regions underlie skilled movement?
- Dorsal stream (action path)
- Prefrontal cortex (planning)
- Premotor cortex
- Primary motor cortex (high degree of plasticity)
- Spinal cord (relays info between top and bottom)
- Basal ganglia (adjusts force of movement)
- Cerebellum (error correction)
- Somatosensory cortex (indicates if task successful)
What are the general steps involved in skilled movement?
- Visual info required to locate the target
- Frontal lobe motor areas plan the reach and command of the movement
- Spinal cord carries info to the hand
- Motor neurons carry message to muscles of the hand and forearm
- Sensory receptors on the fingers send message to sensory cortex saying that the cup has been grasped
- Spinal cord carries sensory info to the brain
- Basal ganglia judge grasp forces, and cerebellum corrects movement
- Sensory cortex receives message that the cup has been grasped
What did Fritsch and Hitzig demonstrate in 1870?
- “On the electrical excitability of the cerebrum”
- Demonstration of a region of the cerebral cortex involved in motor function
- Cortex is electrically excitable
- Topographically organized representation of the body in the brain
- Experimental evidence for localization of function in the cerebral cortex
- Prior to this, people thought cerebrum was inhibitory
What was the contribution of John Hughlings Jackson?
- Termed the Jacksonian March which is a simple, partial seizure
- Occurs on one side of the body and progresses in a predictable pattern
- Believed that behaviour should give insight into human brain structure
- From observing the pattern on one side, determined there must be a pattern in brain activity as well (i.e., fingers and hands must be mapped close together)
What was Wilder Penfield responsible for?
- Canadian neurosurgeon who used select stimulation on cerebrum to determine areas of function
- Developed sensory and motor homunculus (i.e., packing density of receptors)
- Sensation and movement very connected (high degree of sensation corresponds to good, fine movements)
What are the functions of the 6 different layers of the motor cortex?
- Layer 4 - where info travels to first
- Layers 1-3 - Process incoming info
- Layers 5 and 6 - Send info out to adjacent neocortical areas (i.e., brainstem and spinal cord)
Which motor cortex layer specifically sends info to the brainstem and spinal cord?
- Layer 5
- Main efferent pathways from layer 5
- These are often referred to as pyramidal tracts
What are the names of the tracts where the axons cross and the axons that do not cross?
- Lateral corticospinal tract (i.e., limbs and digits on the opposite side) - These axons cross
- Ventral corticospinal tract (i.e., midline muscles) - These axons do not cross
What method is used to stimulate layer 5 in the motor cortex?
- Intracortical microstimulation (ICMS)
What type of cortical maps were developed using short-duration ICMS?
- Able to map forelimb movements like digit flexion, elbow extension, elbow flexion, wrist extension, etc.)
What’s the issue with short-duration ICMS?
- These short stimulations do not reflect well in the real world, stimulation is often much longer
- Discovered that longer stimulation paradigms produce complex movements
- This was observed in the M1 of monkeys
- M1 may be controlling groups of muscles, which changes the cortical map
What was the initial theory regarding the control of complex movement? Who disagreed with this theory?
- Action > Feedback > Action > Feedback > Action
- Karl Lashley thought the speed limits in the CNS are too slow for feedback to regulate movements
What did Lashley propose for explaining the behaviours produced by longer stimulation?
- Proposed motor sequences - movement modules that are pre-programmed by the brain and produced as a unit, while the next sequence is held in readiness
- This way there isn’t feedback adjusting every muscle
What can alter these movement maps?
- Experience can alter these motor maps
- Ex. Playing the piano at a young age
- M1 is incredibly plastic
Which area has a significant increase/change in synapses and neurons when learning the skilled reaching task?
- The caudal forelimb area
