Lecture 20 Flashcards
Describe the function of the pupil, iris, and cornea in the process of vision.
The pupil is the opening that allows light to enter the eye, the iris controls its size, and the cornea is a transparent surface covering the pupil and iris.
What is the primary role of the retina in the visual system?
The retina converts light energy into electrical impulses, which are then transmitted to the brain.
Differentiate between rods and cones in the retina. What are their specific functions?
Rods are specialized for low light levels and are more sensitive to light. Cones are specialized for higher light levels and color vision, with a central retinal concentration.
How does the brain compensate for the blind spot in the retina?
The brain “fills in” the perception of the blind spot, so individuals are not aware of any holes in their field of vision.
Explain the concept of the visual field for one eye. Why are images inverted on the retina?
The visual field is the total space viewed by one eye. Images are inverted on the retina due to the optical properties of the eye.
What happens at the optic chiasm, and how does it affect visual processing?
At the optic chiasm, some axons from nasal hemi-retinas cross the midline, affecting the perception of visual stimuli in the contralateral visual field.
Describe the retinotectal pathway in the visual system. What is the role of the superior colliculus?
The retinotectal pathway involves projections from the retina to the superior colliculus, which contains a retinotopic map and is involved in subcortical vision.
What is the retinogeniculostriate pathway, and which brain regions are involved?
The retinogeniculostriate pathway carries visual information from the retina to the lateral geniculate nucleus (LGN) and then to the primary visual cortex (striate cortex).
How does the primary visual cortex (V1) process visual information?
V1 processes visual information through orderly projections and contains a neural map of the retina.
What is the phosphene threshold, and how does it relate to visual cortex excitability?
The phosphene threshold is the minimum TMS intensity that evokes phosphenes. A lower threshold indicates increased visual cortex excitability
Explain the impact of ecstasy use on visual cortex excitability, as discussed in the notes.
Ecstasy use was associated with lower phosphene thresholds, suggesting increased visual cortex excitability.
How is sensory information integration achieved in the brain, and what role do subcortical structures play?
Sensory integration occurs through the transmission of sensory information to heteromodal regions of the cortex and subcortical structures. For example, the superior colliculus integrates visual and auditory information.
Describe the ventriloquist illusion and how it demonstrates the integration of visual and auditory information.
The ventriloquist illusion occurs when the brain mislocalizes sound based on synchronous but spatially discrepant visual events, illustrating the integration of visual and auditory cues.
What are some overlapping characteristics across different sensory systems
Overlapping characteristics include the relay of sensory information through the thalamus and the potential for spontaneous activity leading to perceived sensations, such as hallucinations or tinnitus.
