Lecture 8 - vision and the visual cortex Flashcards
Where do signals from the retina of your left eye project to in the visual cortex?
signals from the retina of the left eye project to both the left and right hemispheres of the visual cortex
What does retinotopic mapping of V1 (primary visual cortex) mean?
retinotopic mapping means that adjacent V1 neurons respond to images falling onto adjacent positions on the retinae
What does retinotopic mapping of V1 (primary visual cortex) mean?
Retinotopic mapping means that adjacent V1 neurons respond to images falling onto adjacent positions on the retinae
What characterizes the functional architecture of human vision?
The functional architecture of human vision is characterized by:
- specialization: cells respond selectively to specific stimulus characteristics
- modularity: cells that respond to similar stimulus characteristics are clustered into specific brain regions
- Hierarchy of processing structures: Cells respond to progressively complex stimulus characteristics as we follow the anatomical connections from the retina through higher-level visual brain regions
What is the receptive field of a retinal ganglion cell?
- The receptive field of a retinal ganglion cell is the region of the retina to which the visual cell is responsive.
- retinal ganglion cells can have circular receptive fields, responding positively to input from a central region and negatively to input from a surrounding region (on center/ off surround) or vice versa (Off center / on surround)
How do visual signals get to the brain from the retina?
Visual signals exit the eye via the optic nerve, propagate to the optic chiasma where they cross to the opposite side, and then travel to the lateral geniculate nucleus (LGN) before reaching the primary visual cortex (V1) at the back of the brain
What types of response selectivity are found in V1 cells?
V1 cells show complex response selectivity, including:
- simple cells: Response to oriented stripes of contrast in a specific subfield
- end-stopped cells: responsive to oriented stripes of a specific length
- complex cells: Response to oriented stripes of contrast anywhere within their receptive field
- direction-selective cells: responsive to oriented striped of contrast moving in a particular direction
What is blindsight and what does it suggest about visual pathways?
Blindsight is the ability to respond to visual stimuli without conscious perception, often due to damage to V1. It suggests the existence of a secondary visual pathway involving the superior colliculus and pulvinar to the medial temporal lobe (MT or V5), which supports some visual sensitivity but not conscious perception.
What does the dual visual streams hypothesis propose?
The dual visual streams hypothesis proposes that there are two visual systems: the ventral stream (important for generating conscious visual sensations) and the dorsal stream (important for vision-for-action)
What is functional modularity in the visual brain?
Functional modularity refers to the specialization of different brain regions for processing different types of visual information, such as V5 for motion, V4 for color, and the occipital face area (OGA) for human faces
What is the binding problem in visual perception?
The binding problem refers to the challenge of how the brain integrates activity spread across different regions and times to form coherent perceptions.
This includes spatial and temporal binding problems, where features of objects need to be correctly combined across space and time .
How might the brain solve the binding problem?
Potential solutions to the binding problem include synchronous neural activity, feedback mechanisms, and attention-based processes, although the exact solution remains a mystery.
