chapter 9

off center cells receptive field

(B) In the receptive field of an RGC with an off-center and on-surround, light in the center produces inhibition, light on the surround produces excitation, and light across the entire field produces weak inhibition.

ventral stream

- "what" Visual processing pathway from V1 to the temporal lobe for object identification and perceiving related movements.

dorsal stream

- "where" Visual processing pathway from V1 to the parietal lobe; guides movements relative to objects.

Myopia

- (nearsightedness), people can not see distant objects b/c the focal point falls short (infront) of the retina - can be from excessive curve of the cornea the eyeball is to loooong

luminance contrast

- Amount of light an object reflects relative to its surroundings - Luminance is the amount of visible light reflected to the eye from a surface, and contrast is the difference in luminance between adjacent parts of that surface. The photograph in shows us two clear differences in luminance contrast. On the left, the woman's pink top contrasts sharply with her black slacks, but the sleeve on the right contrasts far less with the background. It does not appear as bright.

Cortical column

- Anatomic organization that represents a functional unit six cortical layers deep and approximately 0.5 mm square, perpendicular to the cortical surface.

quadrantanopia

- Blindness of one quadrant of the visual field - a lesion in one of these areas: the optic tract, the LGN, or cortical region V1 be partial - A large lesion of the lower lip of the calcarine fissure

auditory flow

- Change heard as a person and a source of sound move relative to one another. - useful for telling us how fast we are going, whether we are going in a straight line or up or down, and whether we or an object in the world is moving.

androgen

- Class of hormones that stimulates or controls masculine characteristics and level of sexual interest.

amblyopia

- Condition in which vision in one eye is reduced as a result of disuse; usually caused by a failure of the two eyes to look in the same direction.

optic ataxia

- Deficit in the visual control of reaching and other movements.

critical period/ sensitive period

- Developmental window during which some event has a long-lasting influence on the brain; also, sensitive period - specific sensory experiences occurring at particular times are especially important

trichromatic theory

- Explanation of color vision based on the coding of three primary colors: red, green, and blue.

opponent process

- Explanation of color vision that emphasizes the importance of the apparently opposing color pairs: red versus green and blue versus yellow.

facial agnosia/prosopagnosia

- Face blindness—the inability to recognize faces; also called prosopagnosia.

anencephaly

- Failure of the forebrain to develop.

Imprinting

- Formation of an attachment by an animal to one or more objects or animals at a critical period in development.

ocular dominance column

- Functional column in the visual cortex maximally responsive to information coming from one eye - receive input from the left or right eye

papilledema

- If intracranial pressure increases, as occurs with a tumor or brain abscess (an infection), the optic disc swells, leading to (swollen disc) - The swelling occurs in part because, like all neural tissue, the optic nerve is surrounded by cerebrospinal fluid - Pressure inside the cranium can displace CSF around the optic nerve, causing swelling at the optic disc.

visual-form agnosia

- Inability to recognize objects or drawings of objects

optic chiasm

- Junction of the optic nerves, one from each eye, at which the axons from the nasal halves of the retinas cross to the brain's opposite side.

magnocellular (M) cell

- Large visual system neuron sensitive to moving stimuli and black-white vision - receive their input primarily from rods and so are sensitive to light but not to color - also sensitive to movement - layer 1 and 2 on Lateral Geniculate nucleus (thalamus)

retina

- Light-sensitive surface at the back of the eye consisting of neurons and photoreceptor cells.

The periphery parts of the visual field is represented where in the brain?

- More anterior in the occipital lobe whereas the central parts of the visual field are more at the back of the brain + The fovea sends information to a disproportionately large part of the occipital cortex, which is why visual acuity is best in the central part of the visual field

retinal ganglion cell (RGC)

- One of a group of retinal neurons with axons that give rise to the optic nerve. - RGC axons collect in a bundle at the optic disc and leave the eye to form the optic nerve

color constancy

- Phenomenon whereby an object's perceived color tends to remain constant relative to ther colors, regardless of changes in illumination - olors appear to remain the same relative to one another despite changes in light - For instance, were you to look at a bowl of fruit through light-green glasses, the fruit would take on a greenish tinge, but bananas would still look yellow relative to red apples. If you removed all the fruit except the bananas and looked at them through the tinted glasses, the bananas would appear green because the color you perceive is isolated relative to any other

cone

- Photoreceptor specialized for color and high visual acuity - do not respond to dim light, but they are highly responsive to bright light - mediate both color vision and our ability to see fine detail (visual acuity) - the fovea has ONLY cones-> still few out of fovea to tho-> thus vision is not as sharp on the outside - cones contain three light absorbing pigments blue= short wavelength - green= medium wavelength - red= long wavelength - each cone pigment responds to light across a range of frequencies, not just to its frequency of maximum absorption - The numbers of red and green cones are approximately equal, but blue cones are fewer-> thus more sensitive to green and red wavelengths

rod

- Photoreceptor specialized for functioning at low light levels. - longer than cones and cylindrical at one end, whereas cones have a tapered end - sensitive to low levels of brightness (luminance), especially in dim light; and function mainly for night vision - all rods contain the same light absorbing pigments

striate cortex

- Primary visual cortex (V1) in the occipital lobe; shows stripes (striations) on staining

masculinization

- Process by which exposure to androgens (male sex hormones) alters the brain, rendering it identifiably male.

geniculostriate system

- Projections from the retina to the lateral geniculate nucleus to the visual cortex - then to layer IV of the primary visual cortex in the occipital lobe - bridges the thalamus (geniculate) and the striate cortex

chemoaffinity hypothesis

- Proposal that neurons or their axons and dendrites are drawn toward a signaling chemical that indicates the correct pathway - specific molecules in different cells in various midbrain regions give each cell a distinctive chemical identity - Each cell has an identifiable biochemical label. Presumably, incoming axons seek out a specific chemical such as the tropic factors discussed in, and consequently land in the correct general midbrain region. - problem is that chemical affinity directs incoming axons only to a general location, how place in correct position? simultaneous activity and with the passage of time, cells eventually line up correctly in the connections they form and become more precise as to where they fire

blob

- Region in V1 that contains color-sensitive neurons, as revealed by staining for cytochrome oxidase - the less dark regions separating them as interblobs - Neurons in the blobs take part in color perception - neurons in the interblobs participate in perception of form and motion

visual field

- Region of the visual world seen by the eyes.

sensation

- Registration by the sensory organs of physical stimuli from the environment.

blind spot

- Retinal region where axons forming the optic nerve leave the eye and blood vessels enter and leave; has no photoreceptors and is thus said to be blind - no photoreceptors in this part of the retina - visual system solves the blind spot problem: your optic disc is in a different location in each eye. The optic disc is lateral to the fovea in each eye, which means that it is left of the fovea in the left eye and right of the fovea in the right eye. Because the two eyes' visual fields overlap, the right eye can see the left eye's blind spot and vice versa.

parvocellular (P) cell

- Small visual system neuron sensitive to differences in form and color. - The smaller P cells receive their input primarily from cones and so are sensitive to color - found largely in the region of the fovea - Layers 3, 4, 5, 6 on the lateral geniculate nucleus (thalamus)

topographic map

- Spatially organized neural representation of the external world.

photoreceptor

- Specialized retinal neuron that transduces light into neural activity. - on the retina - The neurons lie in front of the photoreceptor cells, but they do not prevent incoming light from being absorbed by those receptors - the neurons are transparent and the photoreceptors are extremely sensitive to light

growth spurt

- Sporadic period of sudden growth that lasts for a finite time.

optic flow

- Streaming of visual stimuli that accompanies an observer's movement through space. - When we run, visual stimuli appear to stream by us, a stimulus configuration - useful for telling us how fast we are going, whether we are going in a straight line or up or down, and whether we or an object in the world is moving.

primary visual cortex (V1)

- Striate cortex in the occipital lobe that receives input from the lateral geniculate nucleus.

perception

- Subjective interpretation of sensations by the brain - how we interpret what we sense

tectopulvinar system

- The second pathway leading from the eye is formed by the axons of the remaining M ganglion cells - Projections from the retina to the superior colliculus through the midbrain tectum to the pulvinar (thalamus) to the parietal and temporal visual areas - bypassing the occipital visual areas

sudden infant death syndrome (SIDS)

- Unexplained death while asleep of a seemingly healthy infant less than 1 year old - babies to have a particular gene variation that makes the serotonin transporter unusually efficient - Normally, the serotoninergic system helps to stimulate a respiratory mechanism that responds to high carbon dioxide levels in the blood and acts to expel the gas - serotonin is cleared from the synapse more rapidly than normal. This action makes 5-HT less effective in regulating life-threatening events such as carbon dioxide buildup during sleep

extrastriate (secondary visual) cortex (V2-V5)

- Visual cortical areas in the occipital lobe outside the striate cortex - each occipital region has a unique cytoarchitecture (cellular structure) and unique inputs and outputs, we can infer that each must be doing something different from the others

On center cells receptive field

- center spot of light shining on the center excites the neuron, but a spot of light in the surround inhibits it. When the light in the surround is turned off, firing rate increases briefly—an offset response. A light shining in both the center and the surround would produce a weak increase in firing

Hyperopia

- farsightedness - cant focus on objects up close - eyeball is to short - or the lens may be to flat w not enough curve

Region V2

- has a pattern of thick and thin stripes intermixed with pale zones. The thick stripes receive input from the movement-sensitive neurons in region V1; the thin stripes receive input from V1's color-sensitive neurons; and the pale zones receive input from V1's form-sensitive neurons - thick stripes= movement - thin stripes= color - pale zones= form

a complex cell

- in V1 shows the same response throughout its circular receptive field, responding best to bars of light moving at a particular angle - The response is reduced or absent with the bar of light at other orientations

Spina bifida

- in which the genetic blueprint goes awry and the neural tube does not close completely, leads to an incompletely formed spinal cord. After birth, unless treated with folic acid, children with spina bifida usually have serious motor problems.

Müller cells

- special glial cells in the retina - span from the retina's inner membrane at the front to the photoreceptors at the back of the retina and act as optical fibers, channeling light to the buried photoreceptors.

Each retinal ganglion cell responds only to

- the presence or absence of light in its receptive field, not to shape. Shape is constructed by processes in the cortex from the information that those ganglion cells pass on about events in their receptive fields.

retinohypothalamic tract

- third small pathway - Neural route formed by axons of photosensitive retinal ganglion cells (pRGCs) from the retina to the suprachiasmatic nucleus; allows light to entrain the SCN's rhythmic activity - synapses in the tiny suprachiasmatic nucleus (SCN) in the hypothalamus, next to the optic chiasm - absorb blue light at a wavelength (between 460 and 480 nm) different from the wavelengths of rods or cones - participates both in regulating circadian rhythms and in the pupillary reflex that expands and contracts the pupil in response to the amount of light falling on the retina

To summarize, an organism's genetic blueprint is...

- vague in regard to exactly which connections in the brain go to exactly which neurons. Experience fine-tunes neural connectivity by modifying those details.

Retinal ganglion cells fall into two major categories, called

1. Magnocellular 2. Parvocellular

the relation between brain and behavioral development from three perspectives

1. Structural development can be correlated with emerging behaviors. 2. Behavioral development can be predicted by the underlying circuitry that must be emerging. 3. Research can focus on factors such as language, injury, or socioeconomic status (SES) that influence both brain structure and behavioral development.

First three layers of cells after light goes to the rods and cones, in the retina are....

1. bipolar 2. horizontal 3. amacrine Rod/cone-> Horizontal linking bipolar cells with amacrine cells-> amacrine cells link the bipolar cells with the retinal ganglion cells - Horizontal cells link photoreceptors with bipolar cells, whereas amacrine cells link bipolar cells with cells in the second neural layer, the retinal ganglion cells (RGCs)

scotoma

A smaller lesion of the lower lip of the calcarine fissure - Small blind spot in the visual field caused by migraine or by a small lesion of the visual cortex

Why do so many mental disorders appear during adolescence?

Adolescence is a time of rapid brain change related to pubertal hormones and psychosocial stressors, both of which make the brain vulnerable to disorders.

optic neuritis

Another cause of papilledema is inflammation of the optic nerve itself - Whatever the cause, a person with a swollen optic disc usually loses vision owing to pressure on the optic nerve - If the swelling is due to optic neuritis, probably the most common neurological visual disorder, the prognosis for recovery is good.

The auditory system has ____________ relays

Four

What can we say if the loss of vision is in both eyes versus one?

If the loss of vision is in one eye only, the problem must be in that eye or its optic nerve; if the vision loss affects both eyes, the problem most likely is in the brain - the visual field, not the eye, is represented in the brain

Describe the opponent process in the retinal ganglion cells.

RGCs are excited by one wavelength of light and inhibited by another, producing two pairs of what seem to be colour opposites—red versus green and blue versus yellow.

receptive field

Sensory region that stimulates a receptor cell or neuron. - a specific part of the world to which it responds

Recognition of complex visual stimuli such as faces is completed in the ___________ lobe.

Temporal

temporal retina

The lateral path - travels straight back on the same side (Ipsilteral) - Information from the right side of the visual field (blue) moves from the two left halves of the retinas, ending in the left hemisphere - Information from the left side of the visual field (red) hits the right halves of the retinas and travels to the right side of the brain.

nasal retina

The medial path of each retina - crosses to the opposite side - ex. right side of visual field goes to left side (counterlateral) - Information from the right side of the visual field (blue) moves from the two left halves of the retinas, ending in the left hemisphere. Information from the left side of the visual field (red) hits the right halves of the retinas and travels to the right side of the brain.

The visual and somatosensory systems have _______ relays

Three

orientation detectors (simple cells)

V1 cells respond to stimuli more complex than simply light on or light off - In particular, these cells are maximally excited by bars of light oriented in a particular direction rather than by spots of light - have an on-off receptive-field arrangement, but the arrangement is rectangular rather than circular

stimulus equivalence

an object is represented not by the activity of a single neuron but rather by the activity of many neurons with slightly varying stimulus specificity - These neurons are grouped in a column this finding is important because it provides an explanation for recognizing an object as remaining the same despite being viewed from different orientations.

Why does a cortical neuron have such a big receptive field?

cells in the cortex have much larger receptive fields than RGCs do - This large field size means that the receptive field of a cortical neuron must be composed of the receptive fields of many RGCs

achromatopsia

complete color deficiency owing to a cortical lesion presumed to be in region V4 - color agnosia

homonymous hemianopia:

complete cuts of the optic tract, the LGN, or cortical region V1 - Blindness of an entire left or right visual field - A complete lesion of V1 in the left hemisphere

protanopia

complete lack of red cones

Tritanopia

condition the lack of blue cones

What binds the two sides of vision?

corpus callosum, which binds the two sides of the visual field together at the midline.

monocular blindness

destruction of the retina or optic nerve of one eye produces monocular blindness, the loss of sight in that eye - Partial destruction of the retina or optic nerve produces a partial loss of sight in one eye, restricted to the visual field region that has severed connections to the brain

Stage III of piagets of cognitive development

is the period of concrete operations, typically 7 to 11 years. Children learn to mentally manipulate ideas about material (concrete) things such as volumes of liquid, dimensions of objects, and arithmetic problems.

List four types of cells that have visual receptive fields: ___________ , ___________ , ___________ , and ___________ .

photoreceptors; retinal ganglion cells, lateral geniculate neurons, cortical neurons

hypercomplex cell

responds to a moving bar of light in a particular orientation (horizontal, e.g.) anywhere in the excitatory (ON) part of its receptive field. If most of the bar extends into the inhibitory area (OFF), however, the response is inhibited.

A ganglion cell's receptive field is therefore the

retinal region on which it is possible to influence that cell's firing

Stage I of piagets of cognitive development

sensorimotor period, from birth to about 18 to 24 months of age. During this time, babies learn to differentiate themselves from the external world, come to realize that objects exist even when out of sight, and gain some understanding of cause and effect. - object permanence, stranger anxiety

We distinguish one sensory modality from another by its ____________.

target in the brain

The nonmatching-to-sample task is believed to measure the function of the __________; the concurrent-discrimination learning task is believed to measure the function of the __________.

temporal lobe; basal ganglia

deuteranopia

the lack of green cones

Stage IV of piagets of cognitive development

the period of formal operations, is attained sometime after age 11. Children are now able to reason in the abstract, not just in concrete terms. - abstract logic, mature moral reasoning

Stage II of piagets of cognitive development

the preoperational period, takes place at age 2 to 6 years. Children gain the ability to form mental representations of things in their world and to represent those things in words and drawings. - pretend play, egocentrism, language development

nystagmus

tiny, involuntary eye movements almost constantly - Because of this usually constant eye motion

Language development is correlated with cortical thinning related to __________ and cortical thickening related to __________.

vocabulary; sound processing