Lecture 2 Flashcards
Explain the role of rods and cones in the retina. How do they respond to different levels of light, and what types of vision are they responsible for?
Rods and cones are photoreceptor cells in the retina. Rods are highly sensitive to low levels of light and are responsible for scotopic vision, which allows us to see in dim light conditions but does not perceive color. Cones, on the other hand, are responsible for photopic vision, which provides high acuity and color vision under brighter lighting conditions.
Differentiate between photopic and scotopic vision. What are the main characteristics of each, and how do they relate to the function of rods and cones?
Photopic vision is associated with high acuity and color vision under well-lit conditions and is primarily mediated by cones. Scotopic vision is adapted for low-light conditions and is mediated by rods, which are sensitive to dim light but do not detect color.
Describe the distribution of cones and rods in the peripheral vision compared to the fovea. How does this affect color vision and light sensitivity in different parts of the visual field?
In the peripheral vision, there are fewer cones and a higher concentration of rods. This leads to reduced color discrimination in the periphery but increased light sensitivity. In contrast, the fovea contains a higher density of cones, enabling detailed color vision but lower sensitivity to light.
Explain the Mona Lisa experiment conducted by Livingstone (2002). What does it reveal about the perception of facial expressions in different visual fields?
In Livingstone’s experiment, the Mona Lisa’s half-smile was presented either in the right visual field (processed by the left hemisphere) or the left visual field (processed by the right hemisphere). Participants perceived the Mona Lisa as happier when the smile part was in their right visual field, suggesting that emotional processing, particularly positive emotions, is regulated in the left hemisphere of the brain.
What are intrinsically photosensitive retinal ganglion cells (IPRGCs), and how do they contribute to the regulation of circadian rhythms? Where are IPRGCs located in the retina?
IPRGCs are retinal ganglion cells that are maximally sensitive to blue light and play a crucial role in regulating circadian rhythms and the sleep-wake cycle. These cells receive light information from the lower half of the retina, primarily from above, which corresponds to the direction of sunlight. IPRGCs communicate with the suprachiasmatic nucleus (SCN) in the brain to synchronize the body’s internal clock with external light cues.
What is lateral inhibition, and how does it contribute to visual perception? Provide an example of lateral inhibition in visual processing.
Lateral inhibition is a neural process in which neighboring neurons inhibit each other’s activity. It enhances the contrast and sharpness of edges in visual perception. An example is simultaneous contrast, where a gray square appears darker or lighter depending on the surrounding background. This phenomenon is a result of lateral inhibition.
Explain the opponent process theory
The opponent process theory is a color vision theory that suggests that our perception of color is based on the presence of opposing pairs of color receptors or neurons in the visual system. These pairs of receptors are sensitive to pairs of complementary colors, and their interactions help us perceive a wide range of colors and explain various color-related phenomena. a blue-yellow
mechanism and a red-green mechanism.
Describe the three types of cones in human vision based on their sensitivity to different wavelengths of light.
Short (S)-Cones (Blue): These cones are primarily sensitive to shorter wavelengths of light, corresponding to the blue part of the electromagnetic spectrum.
Medium (M)-Cones (Green): Medium cones are sensitive to medium-wavelength light, which falls within the green part of the spectrum.
Long (L)-Cones (Red): Long cones are most sensitive to longer wavelengths of light, particularly in the red region of the spectrum.
Explain the differences between EPSPs and IPSPs in the context of neuron communication. Provide examples of how these potentials influence the behavior of a postsynaptic neuron. Additionally, discuss how the balance between EPSPs and IPSPs determines whether a neuron will generate an action potential.
The balance between EPSPs and IPSPs determines whether a neuron fires or not. If EPSPs outweigh IPSPs, the neuron fires and sends a signal. If IPSPs are stronger, the neuron doesn’t fire. It’s like a seesaw: whichever side is heavier decides the outcome.
This balance is crucial for regulating information flow in the nervous system.
What is the role of glutamate in the retina, and how does it contribute to the processing of visual information?
Glutamate serves as a neurotransmitter in the retina, playing a critical role in the transmission and processing of visual information. When photoreceptor cells (rods and cones) are exposed to light, they release glutamate, which acts as a signal to convey the visual input to other retinal neurons. Glutamate binds to receptors on bipolar cells and horizontal cells, initiating a cascade of electrical changes that enhance and refine visual information. Ultimately, this process helps transmit visual signals from photoreceptors to ganglion cells, which then send the information to the brain via the optic nerve. Additionally, glutamate modulation allows the retina to adapt to varying light conditions, optimizing visual perception.
What are Mach bands?
Mach bands are an optical illusion where the borders between light and dark areas look even brighter or darker than they really are. It’s like a trick your eyes play on you when you see a sharp change in brightness. This illusion helps your eyes spot edges and differences in light better. So, it’s like your eyes exaggerating the contrast to make things stand out.
What is the electromagnetic spectrum?
Explain the differences between monochromatic, dichromatic, and trichromatic vision in terms of color perception.
Monochromatic vision sees in grayscale without specific colors. Dichromatic vision perceives only two primary colors, often blues and greens. Trichromatic vision can distinguish a full range of colors, including blues, greens, and reds. These differences are based on the number of color-sensitive cones in the eyes and affect how individuals perceive colors in their surroundings.
