Brain and Behavior (Ch. 9)

What is a Blind Spot?

The area of the retina where no photoreceptors are present, causing a gap in vision.

What are Blobs in the visual cortex?

Regions in the visual cortex that are sensitive to color.

What is Color Constancy?

The brain’s ability to perceive colors as stable despite changes in lighting.

What is a Cone?

A type of photoreceptor in the retina responsible for color vision.

What is a Cortical Column?

A vertical arrangement of neurons in the cortex that process similar sensory information.

What is the Dorsal Stream?

The 'where' pathway in the brain, responsible for processing motion and spatial information.

What are the Extrastriate Cortical Areas (V2–V5)?

Brain regions involved in higher-level visual processing, such as motion and form.

What is Facial Agnosia?

The inability to recognize faces, also called prosopagnosia.

What is the Fovea?

The central part of the retina, packed with cones, responsible for sharp vision.

What is the Geniculostriate System?

The visual pathway from the eye to the primary visual cortex, crucial for processing detailed visual information.

What is Homonymous Hemianopia?

Loss of vision in the same side of both eyes.

What is Luminance Contrast?

The difference in light intensity that makes an object stand out from its background.

What is a Magnocellular (M) Cell?

A type of retinal ganglion cell involved in detecting motion and broad outlines.

What are Ocular Dominance Columns?

Columns in the visual cortex that respond primarily to input from one eye.

What is the Opponent Process theory of color vision?

A theory explaining color vision where opposing colors (e.g., red-green) are processed together.

What is Optic Ataxia?

A condition where someone has difficulty using vision to guide their hand movements.

What is the Optic Chiasm?

The point where the optic nerves from both eyes cross over in the brain.

What is a Parvocellular (P) Cell?

A retinal ganglion cell responsible for detecting color and fine details.

What is Perception?

The brain’s interpretation of sensory information to form an understanding of the environment.

What is a Photoreceptor?

Cells in the retina (rods and cones) that detect light.

What is the Primary Visual Cortex (V1)?

The first area in the cortex to receive and process visual information from the eyes.

What is Quadrantanopia?

Loss of vision in a quarter of the visual field.

What is a Receptive Field?

The specific part of the visual field that a neuron in the visual system responds to.

What is the Retina?

The layer at the back of the eye containing photoreceptors that convert light into neural signals.

What is a Retinal Ganglion Cell (RGC)?

Cells in the retina that send visual information to the brain.

What is the Retinohypothalamic Tract?

A pathway that carries information about light to the hypothalamus, helping regulate circadian rhythms.

What is a Rod?

A type of photoreceptor in the retina responsible for vision in low light conditions.

What is a Scotoma?

A small area of partial or complete blindness in the visual field.

What is Sensation?

The raw data received by sensory organs from the environment.

What is the Striate (Striped) Cortex?

Another name for the primary visual cortex (V1), known for its striped appearance.

What is the Tectopulvinar System?

A visual pathway involved in detecting motion and guiding eye movements.

What is a Topographic Map?

A neural map in the brain that represents spatial relationships in the visual field.

What is the Trichromatic Theory?

A theory of color vision based on three types of cone cells sensitive to red, green, and blue light.

What is the Ventral Stream?

The 'what' pathway in the brain, responsible for identifying objects and form.

What is a Visual Field?

The entire area a person can see without moving their eyes.

What is Visual-Form Agnosia?

The inability to recognize objects based on their shape or form.

What is the function of rods in the retina?

Rods detect low light and are responsible for night vision.

What is the function of cones in the retina?

Cones provide high acuity and color vision, especially concentrated in the fovea.

What are the two visual pathways in the brain?

The dorsal stream processes motion and location ('where' pathway), while the ventral stream processes object recognition ('what' pathway).

What is the function of retinal ganglion cells (RGCs)?

RGCs receive signals from photoreceptors via intermediate neurons and send visual information to the brain via the optic nerve.

What are M cells responsible for?

M cells (magnocellular) receive input from rods and are sensitive to movement but not color.

What is the geniculostriate pathway responsible for?

It processes color, form, and movement, sending signals from the retina to the lateral geniculate nucleus (LGN) and then to the striate cortex (V1).

What does the tectopulvinar pathway do?

It processes movement detection by sending signals from retinal ganglion cells to the superior colliculus in the midbrain and then to the pulvinar and parietal and temporal lobes.

What is the retinohypothalamic tract’s role?

It regulates circadian rhythms and pupillary reflexes by sending signals from photosensitive retinal ganglion cells to the hypothalamus.

What does the dorsal stream process?

The dorsal stream processes spatial information, guiding movements and spatial relationships.

What does the ventral stream process?

The ventral stream is involved in object recognition, including faces, and processes color, form, and fine details.

What principle explains why more neural tissue is dedicated to processing the fovea?

The principle of proper mass states that more neural tissue is needed for more complex processing.

What are on-center and off-center receptive fields in RGCs?

On-center cells are excited by light in the center and inhibited by light in the surrounding area, while off-center cells behave oppositely.

How do retinal ganglion cells detect visual shapes?

RGCs do not directly detect shapes but respond to luminance contrast, emphasizing edges in visual input.

What are simple cells in the primary visual cortex (V1)?

Simple cells respond to bars of light in a particular orientation.

What are complex cells in the primary visual cortex (V1)?

Complex cells respond to moving bars of light in a specific direction.

What are hypercomplex cells in the primary visual cortex (V1)?

Hypercomplex cells respond to moving bars of light with inhibitory regions, detecting the ends of lines and edges.

What is the opponent-process theory of color vision?

Opponent-process theory explains color perception by pairing opposing colors, such as red-green and blue-yellow, in RGCs and V1 cells.

What happens in color vision deficiencies like protanopia or deuteranopia?

In color deficiencies, one type of cone is missing or dysfunctional, impairing the ability to perceive certain colors.

What is monocular blindness?

Monocular blindness is the loss of sight in one eye due to damage to the retina or optic nerve.

What is homonymous hemianopia?

Homonymous hemianopia is blindness in one side of the visual field, often due to cuts to the optic tract, LGN, or V1.

What is quadrantanopia?

Quadrantanopia is the loss of vision in a quarter of the visual field due to damage in the visual cortex.

What is scotoma?

Scotomas are small blind spots caused by minor lesions in V1, often compensated for by the brain through pattern completion.

What is achromatopsia?

Achromatopsia is a form of color blindness resulting from damage in specific areas of the brain.

What is akinetopsia?

Akinetopsia is the inability to perceive movement, resulting from damage to areas involved in motion processing.

What is optic ataxia?

Optic ataxia is the inability to guide hand movements toward objects based on visual information, despite recognizing the objects.

What is the function of the dorsal stream?

The dorsal stream is responsible for processing spatial information and guiding visually-guided movements.

What is the function of the ventral stream?

The ventral stream processes object recognition, including recognizing faces and detailed object features.

How does visual experience in early life shape brain development?

Visual experience in early life is crucial for shaping the brain’s development, and lack of stimulation can lead to long-term perceptual deficits.

What did the studies by Wiesel and Hubel demonstrate about visual deprivation?

Their studies showed that depriving one eye of visual input in early development leads to amblyopia (poor vision in the deprived eye), while cortical areas for the non-deprived eye expand.

What is the brain’s plasticity after stroke or occipital cortex injury?

The brain can recover visual abilities after injury, aided by rehabilitation, even if it occurs long after the injury, by rewiring and strengthening alternative pathways.

What role do the pulvinar-V5 and LGN-V5 pathways play in visual recovery?

These pathways can help individuals with severe damage to V1 recover some visual abilities through rewiring of alternative visual pathways.

How can blind individuals develop echolocation?

Blind people can develop echolocation by using auditory inputs to create spatial maps, as the visual cortex adapts to process sounds.

What is the importance of experience-dependent neural tuning in the ventral stream?

Neurons in the ventral stream can become more selective with experience, improving the ability to recognize and discriminate objects.

How does visual plasticity demonstrate that visual abilities are shaped by experience?

Visual abilities are shaped by experience and learning, not just genetics, as shown by how the brain can adapt to injury or sensory changes.

What happens when visual input is deprived early in life?

Early deprivation of visual input can lead to long-term deficits, but recovery is possible through rehabilitation and neural reorganization.

How do blind individuals repurpose brain areas traditionally used for sight?

Blind individuals can repurpose visual cortex areas to process other sensory inputs like sounds, forming spatial maps from auditory information.

What is the role of neural plasticity in visual development?

Neural plasticity allows the brain to adapt to both experience (e.g., object recognition) and injury (e.g., rewiring after damage).

What is the primary function of the primary visual cortex (striate cortex)?

The primary visual cortex processes visual information by organizing it spatially and integrating input from both eyes to form a unified image.

What are ocular dominance columns?

Ocular dominance columns are regions in the striate cortex that respond to stimulation from either the left or right eye.

What is the difference between structural and functional brain imaging?

Structural imaging shows static anatomical structures, while functional imaging measures dynamic neural activity.

What are the three types of cones responsible for color vision?

The three types of cones are sensitive to short (blue), medium (green), and long (red) wavelengths.

How does opponent processing in color vision work?

Opponent processing at the ganglion cell level distinguishes between color pairs such as red-green and blue-yellow.

What role does the lateral geniculate nucleus (LGN) play in visual processing?

The LGN receives input from the retina and sends signals to the visual cortex for further processing.

What is the difference between magnocellular and parvocellular systems in the LGN?

The magnocellular system processes movement and large receptive fields, while the parvocellular system processes fine detail and color.

What pathways from the retina to the brain are involved in visual processing?

Pathways include the geniculostriate system (to the visual cortex), retinohypothalamic tract (circadian rhythms), and tectopulvinar system (movement detection).

What do feature detectors in the primary visual cortex do?

Feature detectors process edges, textures, and shapes, allowing the brain to identify objects and navigate the environment.

How do small lesions in the occipital cortex affect vision?

Small lesions in the occipital cortex can lead to scotomas, which are small blind spots in the visual field.

How does the brain process stimuli with no response from cells in the primary visual cortex?

The brain can still process some information through other neural pathways, though perception may be incomplete.

What role does the visual cortex play in integrating input from both eyes?

The visual cortex integrates input from both eyes to create a cohesive visual experience, contributing to depth perception and unified vision.