Psych 175 Midterm 2

retinal information processing

- Light passes through several layers of cells before reaching the rods and cones - Light activates a photoreceptor, which then signals the horizontal and bipolar cells that synapse with it ---> - Bipolar cells are connected to amacrine and ganglion cells - Ganglion cells have axons that leave the retina through the optic disc (blind spot), only source of output , only that fire action potientals beside amacrine cell

Transduction of light by rods *

1. light activates (bleaches) rhodopsin 2. Transduction, the G-protein is stimulated 3. Phosphodiesterase (PDE), the efctror enzyme is activated 4. PDE actvity reduced cGMP level 5. Na + channels close, and cell memebrane hyperpolizas similar to cone but requires more bleaching red (long) , green, and blue (short) opsin

Describe the differences between receptive field center and receptive field surround

Bipolar ON: light shined will depolarize, ionotropic OFF: light shine will hyper polarize some bipolar cells, metabotropic Ganglion ON: depolarized OFF: fewer action potentials stimulation of center is cancelled by the surround. and respond to difference in illumination M: gradully slows down there firing, low contrast stimuli P: constanly fire, sensitive to diff wavelength of light receptive field surround direct photo receptor input form horizontal cells receptive field center: direct photo receptor input

Describe the inputs and outputs of the striate cortex ****

Inputs Outputs: in layer IVC magnocellular in layer a parvocellular in layer beta, 1-2 mango, 3,6 para --> layer 4c sublayer, man 4c alpha para 4 c beta, --> koniocellular layer 1 and 3, most in 4c, projects 4c alpha goes to 4 B, beta goes up 2 into layer para between layer and goes to other cortical area, 2,3,4b other cortical area, 5 super col and pons, layer g back to lgn, with each visual cortex, layer 2 and 3 most visual input

Explain the cellular mechanisms for each of the five tastes

Ion channels: allow positive ions to flow in and depolarize salt : Na+ --> sour: Glucose H+ G-protein coupled receptors: interreceptor protein and when a ligand binds to it receptor undergoes a change that causes a G-protein to disassociate and go off and opens ion channels --> depolarization sweet: bitter: umani (savory):

Describe the role of population coding in taste perception

Population coding are the responses of a large number of broadly tuned neurons that are used to specific the properties of a particular taste

Describe the organization of retinal inputs to the LGN Figure 10.9 *

arranged in 6 layers (1 is closest to the eye and 6 is farthest away) , lie like a stack of pancake staht are bent around the optic tract diff type of rentinal info is being kept separate Right goes to left LGN 2,3,5 Left goes to right LGN 1,4,6

Explain the characteristics of receptive fields in the striate cortex ****

binocularity: two receptive fiels one in the ipsilateral eye and the contralateral eye, helps use form a single vision orientational selectivity: bar if light has to fit exactly on the receptive field or won't fire effectively directional selectivity: the respond to the movement of light in on direction and not the other, right ward simple and complex: smaller spot more response than larger spot blob: blobs are generally wavelength sensitive and monocular, lack orientation and direction selective interblob

Identify and describe the cells of the retina, and discuss the pattern of their interconnections *

bipolar cells: direct pathway from photoreceptor to gangliion cells horizontal cells: feed info laterally into outer plexiform layer to influence actvity of biploar and photoreceptors

Describe the functional differences between the dorsal stream and the ventral stream *

dorsal stream: Area MT: process objects motion receives V2 and V3, large receptive fields, directional sensitive MST: specialized sensitive movement, navigation, directing eye movement, motion perections, where ventral stream: color processind V1, V2, V3 Area V4: input from blob and interblob regions achromatopsia: partial or complete loss of color vision despite normal function, what Area IT why both

Discuss the genetics of odor receptors

each receptor gene has a unique structure

Describe how taste represents a labeled line

each taste has its own axon to a particular part of the gustatory cortex in the brain and goes to a specific region there.

Describe the hierarchy of receptive fields in the visual system***** figure 10.30

figure 10.30 ON-center in retinal ganglion --> simple cell in V1 --> inferotemporal visual cortex

Describe how structures of the eye refract light to focus an image on the retina

light enter perpendicular to cornea passes straight through retina --> light that strikes nor in a perpen fashion are angles towrd the retina distance from refractive surface to point light light ray converge = focal distance tigher curve of corena --> shorter focal distance

Describe how you would find the receptive field of a ganglion cell

loacted by recording from the nreorn's axon in teh optic nerve. light is projected unto the retina. locations that increase or decrease the ganglion firing rate

Describe the major components of the olfactory epithelium

mucus layer: made of water with mucopolysaccarides, proteins, and salt cilia of olfactory cells supporting cell: help produce mucus olfactory receptor cell: site of transduction bascal cell: source of new receptor cell cribriform plate olfactory nerve

Explain retinotopy *

neighboring cells in retina feed info to neighboring places is target stucture: LGN and straited cortex 1. mapping of stcure is distorted b/c visual space not uniform, magnified 2. decsrte pont of ligth can activate many cells in the retina 3. perception is abse on brain interpretaion of distrubted pattern's of actvity, mapping of info

Cells in striate cortex

only pydmaid cells send axon out over straite cortex

List the structures of the retinofugal pathway

optic nerve: exit left and right eye at the optic disk optic chiasm: optic never from both eyes form, base of the brain optic tract: un under pia along lateral surface

Discuss the role of temporal coding in the olfactory system

rapid timing of action potentials, encode the quality of ordors

Describe the pathway that olfactory information takes, from receptor to primary olfactory cortex

receptor --> bulb --> olfactory tract --> olfactory tubercle -->medial dorsal nucleus --> orbitofrontal cortex

Compare the similarities and differences between cones and rods

rods: can see in dim light, no color, long and cylindrical, many disks, more sensitive to light, scotopic: night time lighting, rhodopsin cones: can see in regular light, shows color, short cone shaped, fewer disks, photopic: day time lighting, three pigments (red, green, and blue) mesopic: both rods and cones

Describe the five basic tastes

salt: side of tongue sour: side of tongue sweet: tip of the tongue bitter: the back of tongue umani (savory): glutamate

Describe the function of area IT *

see color and abstract shapes, learning, memory, visual perception and memory, respond to faces prosopagnosia: difficulty recognizing faces

Describe the main differences between simple and complex cortical cells *

simple: receive converging input from LGN cells with receptive fields that are aligned at one axis, response when light is on only complex: do not have distinct ON and OFF regions, response when light is off or on

Compare and contrast: rapidly-adapting and slowly-adapting receptors

slow is more sustained reposne during long stomuli rapid: fire quickly but stop even as stimuli continues

List nonthalamic targets of the optic tract *

superior colliculus (optic tectum) command eye and head movement, midbrain- pupils, hypothalamus

Compare and contrast taste buds and papillae

taste buds: each taste bud has 50-150 taste receptors, have bascal cells that surround the taste cells, gustatory afferent axons papillae: small projections, shaped like ridges (folaite), pimples (vallate), or mushroom (fungiform); has one to sevral hundred taste buds

Describe the pathway that gustatory information takes, from receptor to primary gustatory cortex

taste info --> cranial nerves (7,9,10) --> medulla --> gustatory axons enter gustatory nucleus w/i medulla --> Thalamus -->primary gustatory cortex region of post central gyrus and insular cortex

Explain why our vision is much better at the fovea than elsewhere

there is a bunch of cones and no rods in that area

parallel pathways

three channels or pathways process visual input: magnocellular, parvocellular-interblob, blob

Describe the role of population coding in olfaction

use response of a large pop of receptor to encode a specific stimulus, combination of stimulus --> smell

Draw a diagram to help you describe the path of information from the left visual field to the right side of the brain

viewing from left hemifield projected onto the right optic tract nasal crosses at the optic chiasm