Spatial navigation Flashcards
(28 cards)
What do eye movements do?
Offer a relatively simple example of neural control
Allow an understanding of cortical subcortical interactions
Show principles of sensory maps
What do eye movement problems underlie?
Diplopia (double vision)
Drift (nystagmus)
Vital for reading (dyslexia)
Why do we move eyes?
To move the eye across the visual scene and allow parts of the image to fall onto the high resolution part of the retina
To converge the eyes at different distances
To stabilize the visual image on the retina despite motion of the eye (reafferent) or the scene (exafferent)
How do we control eye muscles?
Intra- ocular muscles control pupil diameter
Extra- ocular muscles move the eyeball within the socket
Extra- ocular muscles innervated by specific cranial nerves
What are the functional types of eye movement
Gaze stabilisation
Gaze shifting
Gaze fixation
State the Gaze stabilisation mechanisms (old system to make image sharp)
Optokinetic reflex
Vestibular- ocular reflex
What is Optokinetic reflex
driven by visual motion, assumes the world is stationary, minimizes retinal slip of the image to allow the retina to track it.
What is Vestibular- ocular reflex
driven by head motion system
State the Gaze shifting mechanisms (new system to track objects)
Vergence movements
Smooth pursuit
Saccade movements
What are vergence movements
to shift focus on near & far objects, stimulates movement of both eyes in opposite directions
What is smooth pursuit
eye movements to fixate on moving objects, stimulates movements of both eyes in same directions, requires suppression of OKR
What are saccade movements
rapid eye movements between fixation, stimulates movements of both eyes in same direction
How do you make a saccade?
built using parts of the gaze stabilization circuitry
What is Gaze fixation?
Eyes must be held stationary between movements
What two systems does spatial cognition include
Posterior parietal cortex = self to object (egocentric)
Hippocampus = object to object (allocentric)
how does Hippocampal activity increase
increases with navigation experience (spatial memory)
Neurogenesis in hippocampus persists into adulthood
What are the features of place cells?
- in dorsal (posterior) hippocampus
- have a role in consolidation of memories
- Remap when the behavioural context changes
- Have input from grid cells
What are the features of grid cells?
- In entorhinal cortex
- Fire in a grid like pattern
- Receive high level spatial information from neocortex
- Have spatial scales to activate place cells for unique locations
What is Apraxia?
- Results from damage to left parietal lobe
- Difficulty coordinating sequences of movements in the absence of paralysis or muscular weakness
What is Neglect?
- Results from damage to right parietal lobe
- Difficulty using information about objects in external space
Describe the posterior parietal cortex & spatial processing
- Right posterior parietal cortex codes both left & right visual space
- Left codes only right visual space
What does the Ventral (VIP) encode?
multimodal encoding of space & motion around the head
What does the Anterior (AIP) encode?
touch, grasping & tool use
What does the Medial (MIP) encode?
reaching & pointing
