Visual Sensation and Perception Lecture Notes

Flashcards covering visual sensation, eye anatomy, retinal circuitry, visual pathways, cortical feature detection, and color vision theories based on the lecture notes.

Transduction

The stage one sensory process where receptor cells convert physical environmental energy (such as light waves) into electrical action potentials that neurons can process.

Accommodation

The process by which the lens behind the cornea changes its shape—stretching flat or thickening—to focus incoming light from close or far distances onto the retina.

Photoreceptors

The sensory receptor cells located at the back of the retina (rods and cones) that are exclusively responsible for stage one transduction in the visual system.

Rods

Photoreceptors located in the retinal periphery (approximately 120 million per eye) specialized for night vision, low light levels, basic shapes, and grayscale processing.

Cones

Photoreceptors concentrated in the center of the retina (approximately 6 million per eye) that operate under high light conditions to process color and clear, sharp details.

The Four C's of Cones

A mnemonic device highlighting the primary characteristics of cones: Color vision, Clear vision, Concise detail, and Center of the eyeball.

Bipolar Cells

Retinal interneurons that serve as the middle layer, receiving neural signals from photoreceptors and transmitting them forward to ganglion cells.

Ganglion Cells

Neurons in the front retinal layer whose cell bodies receive input from bipolar cells and whose axons bundle together to exit the back of the eye toward the brain.

Retinal Convergence

The visual wiring pattern where many rods converge onto few bipolar cells and a single ganglion cell, creating less detailed, averaged visual information compared to the direct 1-to-1 cone pathways.

Optic Disk

The hole in the back of the eye through which bundled ganglion cell axons exit toward the brain, creating a blind spot due to the complete lack of photoreceptors.

Optic Chiasm

The anatomical crossover point where visual information from the left visual field of both eyes is routed to the right hemisphere and information from the right visual field crosses to the left hemisphere.

Thalamus

The subcortical brain structure acting as a sensory triage relay station that receives visual signals and directs them to the primary visual cortex.

Lateral Geniculate Nucleus (LGN)

The specific nucleus or hub within the thalamus dedicated to processing and triaging incoming visual information from the optic tract.

Primary Visual Cortex

A specific cortical area situated in the occipital lobe at the back of the brain responsible for stage two processing by breaking down visual messages into elemental parts.

Superior Colliculus

A subcortical visual structure that receives basic light and dark information to assist in regulating circadian rhythms and states of sleep and alertness.

Feature Detectors

Specialized neurons in the visual cortex that fire only when presented with a specific visual stimulus, such as a vertical line, horizontal line, angle, corner, or movement direction.

Fusiform Face Area (FFA)

A specialized region containing feature detector cells that fire selectively when looking at human faces or objects resembling faces.

Prosopagnosia

A visual agnosia, often caused by damage or developmental differences in the fusiform face area, that prevents individuals from recognizing or distinguishing between different faces.

Trichromatic Theory of Color Vision

A theory originally developed by Thomas Young and Hermann von Helmholtz proposing that color vision relies on three cone subtypes containing different photopigment proteins sensitive to short, moderate, and long wavelengths.

Opponent-Process Theory of Color Vision

A theory explaining color processing at the ganglion cell level where colors operate in antagonistic pairs (red-green, blue-yellow, black-white) such that activation of one suppresses the other.