Visual System and Visual Pathways

Vocabulary flashcards covering key terms, anatomical structures, cell types, and visual pathways from the sensory psychology lecture notes.

Receptive Field

An area of sensory space where a particular stimulus can activate a sensory neuron or cell, helping the nervous system locate stimuli, sample environmental information, and accurately identify visual information.

Rods

Photoreceptors in the retina that are highly sensitive to light, work best in dim or low-light conditions, can be triggered by a single photon, do not provide colour vision, and send input to M cells.

Cones

Photoreceptors in the retina that work best in bright light conditions, require significantly brighter light than rods, provide colour vision, and offer greater visual detail.

S-cones

A type of cone photoreceptor responsible for detecting short wavelengths of light.

M-cones

A type of cone photoreceptor responsible for detecting medium wavelengths of light.

L-cones

A type of cone photoreceptor responsible for detecting long wavelengths of light.

Cornea

The transparent front surface of the eye that helps focus incoming light.

Iris

The structure in the eye that controls the amount of light entering.

Pupil

The opening in the iris through which light enters the eye.

Crystalline Lens

The structure in the eye that further focuses light onto the retina.

Ciliary Muscles

Muscles that change the shape of the lens to focus on objects at different distances, relaxing for far objects and contracting for close objects.

Vitreous Humour

A jelly-like substance inside the eye that helps maintain its spherical shape.

Retina

The light-sensitive tissue at the back of the eye that contains photoreceptors.

Optic Nerve

The structure that carries visual information from the retina toward the brain.

Optic Disc

The region on the retina where retinal ganglion cell axons collect to form the optic nerve.

Accommodation

The process by which ciliary muscles relax to flatten the lens when looking at far objects, or contract to thicken the lens when looking at close objects.

Horizontal Cells

Retinal neurons located in the first neuron layer that link photoreceptors directly with bipolar cells.

Amacrine Cells

Retinal neurons that link bipolar cells with retinal ganglion cells.

Parvocellular (P) Cells

Smaller retinal ganglion/LGN cells sensitive to colour and fine details, characterized by high spatial resolution and lower temporal resolution.

Magnocellular (M) Cells

Larger retinal ganglion/LGN cells that receive rod input, detect low-light information and motion, possess higher temporal resolution, and convey 'where' properties.

Spatial Resolution

The visual system's ability to distinguish fine details.

Temporal Resolution

The visual system's ability to detect changes or movement over time.

Visible Spectrum

The range of light wavelengths visible to humans, spanning approximately $390\text{--}700\text{ nm}$.

Ventral Stream

The 'WHAT' pathway travelling from V1 to the temporal lobe, responsible for object recognition, shape perception, and form representation.

Dorsal Stream

The 'WHERE' pathway travelling from V1 to the parietal lobe, involved in determining spatial location, detecting movement, guiding physical actions, and orienting behavior.

Visual-form Agnosia

An inability to recognize objects or drawings based on their visual appearance or form, resulting from damage to the ventral pathway.

Patient DF

A patient with ventral stream damage who could not recognize objects by shape or appearance, but retained the ability to reach for and interact with objects properly due to an intact dorsal stream.

Phototransduction

The physiological process where photoreceptors convert light energy into chemical energy and ultimately into neural/electrical signals.

Retinal Ganglion Cells

Cells in the human visual system (numbering approximately 3 million) whose axons collect at the optic disc to form the optic nerve.

Geniculostriate Pathway

The main visual pathway transmitting visual information from the retina to the lateral geniculate nucleus (LGN) and on to the primary visual cortex.

Tectopulvinar Pathway

A visual pathway involved in spatial orientation, orienting responses, eye movements, and directing attention.

Retinohypothalamic Tract

A visual pathway essential for maintaining circadian rhythms, regulating the body's biological clock, and conveying light/dark environmental information.

Nasal Fibres

Retinal ganglion cell axons located on the inner side of the retina that cross over to the opposite hemisphere of the brain at the optic chiasm.

Temporal Fibres

Retinal ganglion cell axons located on the outer side of the retina that remain on the same side of the brain.

Primary Visual Cortex (V1)

The initial visual processing cortical region located in the occipital lobe that receives thalamic input.