Stimulus Localisation Flashcards
Examples of object localisation
Orientating reflex, smooth pursuit, prediction of motion, saccadic movement during object inspection
What are the important areas involved in stimulus localisation?
The retina, dorsal stream and inferior/superior colliculus
What is the importance of the superior colliculus in stimulus localisation?
It receives input from the somatosensory cortex, the auditory cortex and ganglion cells
Regulates saccadic movements
Integrates information from different sensory modalities
Which Brodmann area is the somatosensory cortex?
1
What is retinotopic mapping?
Organisation whereby neighbouring cells in the retina feed into neighbouring cells in their target structures (e.g. LGN)
Example of cells that have retinotopic organisation
Command neurons - organised in maps and send projections in layers (these layers are aligned)
What is the foveation hypothesis?
Interaction between these maps initiates the orientating reflex
Is the foveation hypothesis correct? Why/why not?
No - the interaction between these maps is indirect, therefore the foveation hypothesis is invalid. The indirect interaction does however initiate the orientating reflex
Pathway of the dorsal stream
M-ganglion - LGN magno - V1 - V2 - V3 - MT - Parietal
What cell type is involved in motion perception?
Direction selective ganglion cells
How are DSRGs involved in motion perception?
They are highly asymmetric and are comprised of different subtypes with different preferred directions. Moving visual stimuli that cross the cells receptive field elicited strong spiking when moving in a ‘preferred’ direction but little to no response when moving in the ‘null’ direction
Which cells do excitatory and inhibitory inputs come from?
Bipolar cells - excitiatory (glutamate)
Amacrine cells - inhibitory (GABA)
Where do bipolar and amacrine cells input to?
Direction selective on-off cells
Describe what happens in RGCs when in the preferred direction
Excitation is larger and inhibition is smaller and delayed
Describe what happens in RGCs when in the null direction
Inhibition is larger and excitation is smaller and delayed
