Retina
Receptive fields
Retinotopic organisation
100
The small dimp at the centre of the retina, filled with specialised photoreceptors
Fovea
100
What is a ganglion cell's receptive field?
The delimited area of the visual field where a stimulation (light/dark) will result in ganglion cell action potentials
100
What is a topographic map?
A topographic map is the ordered projection of a sensory surface or an effector system to one or more structures of the central nervous system.
(e.g.,retinotopic map of the retina in the visual cortex, somatotopic map of the skin in the somatosensory cortex, etc.)
200
The three layers of cells in the retina
(1) Ganglion cells
(2) Bipolar, Horizontal and Amacrine cells
(3) Photoreceptors
200
Describe the most and least favourite stimuli of ON-centre and OFF-centre ganglion cells
1.On-centre (off-surrounding):
most favourite: light in the centre, dark in the surrounding
least favourite: dark in the centre, light in the surrounding
2.Off-centre (on-surrounding):
most favourite: dark in the centre, light in the surrounding
least favourite: light in the centre, dark in the surrounding
200
The ____ visual field is the central portion of the visual field, captured by both eyes; the ____ visual field is the peripheral portion of the visual field, captured by one eye only.
binocular, monocular
300
Describe the main features of RODS (at least 3)
Rods:
•Scotopic vision (low light)
•More in the periphery
•Not sensitive to wavelength (no color vision)
•Low spatial acuity
•Many rods connect to a ganglion cell
300
Photoreceptors and Bipolar cells respond with a ____ potential, while Ganglion cells respond with a ____ potential.
Graded, action
300
Which portion of the retina decusset at the optic chiasm?
Nasal retina
400
Describe the main features of CONES (at least 3)
•Photopic vision (day light)
•More in the fovea/center
•Sensitive to wavelength (color vision)
•High spatial acuity
•Few cones connect to a ganglion cell (often 1:1)
400
Photoreceptors release glutamate with ____ and hyperpolarize (release less transmitter) with increasing ____. This type of activation is called ____ potential.
Dark, light, graded
400
Damage to the _____ before the optic chiasm will result in loss of input from one eye, while damage to the _____ after the optic chiasm will result in loss of input from the ____ visual field.
Optic nerve, optic tract, contralateral
500
Name the three ganglion cellular pathways
Magnocellular, Parvocellular and Koniocellular
500
What is "surround suppression", and why is it important?
Surround suppression is when we present light in the whole area of the receptive field, and the neuron activation goes back to the baseline level (the outer area is suppressing the central response).
This kind of configuration allows the neurons to spike (and so to consume energy to send information) ONLY when there is a difference between two adjacent parts of the space, and so when we are looking to something such as a shape on a background
500
What is the Columnar orientation tuning in V1? Describe the response properties of vertical and adjacent columns.
All the neurons in a vertical column across the layers respond to the same rough area and respond most strongly to the same orientations – this is called a columnar organisation.
Neurons adjacent to each other in the same layer have RFs that are organised in space to be adjacent (think retinotopic mapping here), AND there’s a logical progression of the orientations these neurons prefer.