Chapter 5

Bipolar Cells

Definition: Neurons in the retina that transmit signals from photoreceptors (rods and cones) to ganglion cells.

Blind Spot

Definition: The area in the retina where the optic nerve exits; it lacks photoreceptors, resulting in a gap in visual perception.

Color Constancy

Definition: The perception of colors as relatively constant under varying lighting conditions.

Color Vision Deficiency

Definition: A condition where individuals perceive colors differently than those with normal vision, often referred to as color blindness.

Cones

Definition: Photoreceptor cells in the retina responsible for color vision and visual acuity in bright light.

Fovea

Definition: The central part of the retina with the highest concentration of cones, crucial for sharp central vision.

Ganglion Cells

Definition: Neurons in the retina that receive input from bipolar cells and transmit visual information to the brain via the optic nerve.

Law of Specific Nerve Energies

Definition: A principle stating that the perception of a stimulus depends on the type of nerve fiber activated, not the stimulus itself.

Midget Ganglion Cells

Definition: A type of ganglion cell that has a small receptive field and is involved in high-acuity vision and color processing.

Negative Color Afterimage

Definition: An optical illusion where staring at a colored image causes a complementary color to appear when looking away.

Opponent-Process Theory

Definition: A theory of color vision that proposes color perception is controlled by opposing pairs of colors (red-green, blue-yellow).

Optic Nerve

Definition: The nerve that transmits visual information from the retina to the brain.

Photopigments

Definition: Light-sensitive molecules in photoreceptors that initiate the process of vision by changing shape in response to light.

Pupil

Definition: The adjustable opening in the eye that regulates the amount of light entering the retina.

Retina

Definition: The light-sensitive layer at the back of the eye that contains photoreceptors (rods and cones) and processes visual information.

Retinex Theory

Definition: A theory that explains color perception based on the brain's interpretation of light and color in relation to surrounding colors.

Rods

Definition: Photoreceptor cells in the retina that are sensitive to low light levels and are responsible for night vision.

Trichromatic Theory (or Young-Helmholtz Theory)

Definition: A theory that proposes color vision is based on three types of cones sensitive to red, green, and blue light.

Visual Field

Definition: The entire area that can be seen when the eyes are focused on a central point, including peripheral vision.

Aphantasia

Definition: A condition where individuals are unable to visualize images in their mind, affecting their ability to form mental imagery.

Astigmatism

Definition: A common vision condition caused by an irregular shape of the cornea or lens, leading to blurred vision at all distances.

Blindsight

Definition: A phenomenon where individuals with damage to the primary visual cortex can respond to visual stimuli without conscious visual perception.

Complex Cells

Definition: Neurons in the visual cortex that respond to specific orientations and movements of visual stimuli.

End-Stopped (or Hypercomplex) Cells

Definition: Neurons in the visual cortex that respond to particular lengths of stimuli and are sensitive to their endpoints.

Feature Detectors

Definition: Neurons that respond selectively to specific features of a stimulus, such as edges, angles, or movement.

Horizontal Cells

Definition: Neurons in the retina that facilitate lateral communication between photoreceptors and bipolar cells, enhancing contrast.

Hyperphantasia

Definition: An extreme ability to create vivid mental imagery, often described as having a "photographic memory" for images.

Koniocellular Neurons

Definition: Neurons located in the lateral geniculate nucleus that process color information and contribute to visual perception.

Lateral Geniculate Nucleus (LGN)

Definition: A relay center in the thalamus that receives input from the optic nerve and transmits visual information to the primary visual cortex.

Lateral Inhibition

Definition: A process where excited neurons inhibit the activity of neighboring neurons, enhancing contrast in visual perception.

Magnocellular Neurons

Definition: Large ganglion cells in the retina that are sensitive to motion and low-contrast stimuli, playing a role in detecting movement.

Parvocellular Neurons

Definition: Smaller ganglion cells in the retina that are involved in processing color and fine detail in visual stimuli.

Primary Visual Cortex (V1)

Definition: The area of the brain responsible for processing visual information, located in the occipital lobe.

Receptive Field

Definition: The specific region of sensory space in which a stimulus will affect the firing of a neuron.

Retinal Disparity

Definition: The difference in images between the two eyes, which contributes to depth perception.

Sensitive Period

Definition: A critical time frame during development when the brain is particularly receptive to certain stimuli, affecting learning and development.

Simple Cell

Definition: Neurons in the primary visual cortex that respond to specific orientations of edges and bars of light.

Strabismus

Definition: A condition where the eyes do not properly align with each other, often resulting in double vision or loss of depth perception.

V1 (Primary Visual Cortex)

Definition: The initial cortical area that processes visual information received from the lateral geniculate nucleus.

Dorsal Stream

Definition: The pathway in the brain responsible for processing the spatial location of objects and motion, often referred to as the "where" pathway.

Fusiform Gyrus

Definition: A region of the brain located in the temporal lobe, crucial for face recognition and processing complex visual stimuli.

Inferior Temporal Cortex

Definition: A part of the temporal lobe involved in the processing of complex visual patterns, including object and face recognition.

Motion Blindness

Definition: A condition where individuals cannot perceive motion, despite having intact visual acuity and perception of stationary objects.

MST (Medial Superior Temporal Area)

Definition: A region in the brain that is involved in processing visual motion and spatial awareness.

MT (Middle Temporal Area)

Definition: A brain region involved in the perception of motion and speed, playing a key role in the dorsal stream.

Prosopagnosia

Definition: A neurological condition characterized by the inability to recognize faces, often due to damage in the fusiform gyrus.

Saccades

Definition: Rapid, simultaneous movements of both eyes in the same direction, used to quickly shift focus from one point to another.

Secondary Visual Cortex

Definition: Areas of the brain that process visual information beyond the primary visual cortex, involved in higher-order visual processing.

Ventral Stream

Definition: The pathway in the brain responsible for object recognition and form representation, often referred to as the "what" pathway.

Visual Agnosia

Definition: A condition where individuals can see objects but cannot recognize or interpret them, often due to damage in the ventral stream.