Lecture 10 See Flashcards
(43 cards)
What are the different types of photoreceptors in the human eye?
Three types of Cone:
* Short-wavelength (S) cones
* Medium-wavelength (M) cones
* Long-wavelength (L) cones
*Rod is not contribute to color vision
S cones peak at 420 nm (blue light), M cones at 530 nm (green light), and L cones at 560 nm (red light).
What is the fovea?
An area in the retina with high density of photoreceptors, crucial for sharp vision
The density of photoreceptors declines as you move away from the fovea.
What is the primary role of retinal ganglion cells?
They transmit processed visual information from the retina to the brain via the optic nerve
The signals from photoreceptors are pre-processed before reaching ganglion cells.
What is the significance of receptive fields in the retina?
They define the specific area of the visual field that influences the activity of a ganglion cell
Receptive fields often have a centre-surround organization.
What is the visual pathway responsible for conscious visual experience?
The Retinogeniculate pathway: Retina –> LGN (thalamus) –> V1
This pathway enables conscious perception and interaction with the visual world.
True or False: The rod photoreceptors contribute to color vision.
False
Rods are primarily responsible for vision in low light conditions.
What is deuteranopia?
A type of red-green color blindness characterized by the absence of green cones
It affects color perception.
Fill in the blank: The _______ is responsible for processing visual signals before they reach the cortex.
thalamus
What are the two types of cells in the receptive fields of ganglion cells?
ON cells and OFF cells
ON cells are excited by light in the center, while OFF cells are inhibited by light in the center.
What is the retinogeniculate pathway?
The pathway from the retina to the lateral geniculate nucleus (LGN) in the thalamus
It processes visual signals and sends them to the primary visual cortex.
What role do melanopsin cells play in visual processing?
They help synchronize circadian rhythms 昼夜节律 by providing light information to the suprachiasmatic nucleus (SCN)
This affects sleep, alertness, and other physiological functions.
What does the bionic eye consist of?
A camera, a receiver, and an implant with microelectrodes
It is designed for individuals with blindness due to damaged photoreceptors.
What is a characteristic of vision with a retinal implant?
The perception consists of an array of phosphenes, appearing as light dots without lines or color
It is not equivalent to normal vision.
What is the role of the primary visual cortex?
It is the first stage of conscious processing for visual input
Located in the occipital lobe, it receives about 80% of signals from the eyes.
Fill in the blank: The _______ is where visual signals are grouped by visual field rather than by the eye of origin.
thalamus
What is the function of the lateral geniculate nucleus (LGN)?
It processes visual information and has layers that specialize in motion and color
It contains 2 inner magnocellular and 4 outer parvocellular layers.
What is the non-conscious visual pathway?
A visual pathway where signals go to the Superior colliculus and pulvinar (bypass the LGN and primary visual cortex)
上丘
丘脑枕
What kind of visual functions are supported by the non-conscious visual pathway?
Non-conscious or evolutionarily older functions like motion detection and reflexive responses
What is the significance of bidirectional communication between the LGN and cortex?
It allows for feedback from the cortex to influence how visual information is processed
More feedback fibers go from the cortex to the LGN than from the retina to the LGN.
What does a retinal implant generate?
An array of phosphenes
A sense of a light flash
How do the phosphenes appear visually?
Like a picture made up of light dots
There are no lines or color
What determines the value of the percept in retinal implants?
The number of electrodes
What is the main use of retinotopic stimulation in retinal implant?
Locating hazards
Not effective for enjoying sunsets
Does a retinal implant restore previous visual experiences?
No, it helps the brain guide behaviors
