Exam2 neuro 305

is eye part of central nervous system

Yup

What controls amount of light allowed to enter eye

Iris and pupil, iris adjusts size of pupil

how is retina organized?

light -\> ganglion cells -\> interneurons -\> photoreceptors

most distal part of retina

photoreceptors

what are the types of interneurons in the retina

horizontal
bipolar
amacrine

which photoreceptor for scotopic (low light) vision

Rods

which photoreceptor for phototopic (high light) vision

Cones

Are Rods or are Cones for color vision

Cones

Do Rods or Cones have higher spatial acuity

Cones

Do photoreceptors fire action potentials?

No.

- When light hits them, they change the amount of NT released (Glu) and release the signal off to ganglion cells.

Where are cones located?

fovea (center of retina)

Does distribution of cones from person to person vary?

Yees

The types of Ganglion receptive fields

On-center or Off-center

what do center-surround receptive fields create sensitivity to?

Edges

does a center-surround receptive field connect to just one horizontal neuron

Yes

lateral inhibition

The pattern of interaction among neurons in the visual system in which activity in one neuron inhibits adjacent neurons' responses.

three types of ganglion cells

Magnocellular cell
Parvocellular cell
Koniocellular

What is a midget cell

Parvocellular cell

What is parasol cell

Magnocellular cell

Which ganglion cell has better spatial acuity

Midget/Parvocellular cell

Which ganglion cell exists in higher numbers

Midget/Parvocellular cells

Color opponent process theory

There may be color-sensitive ganglion cells (e.g. red/green, blue/yellow on/off center)

Ganglion cells projecting to LGN (Lateral Geniculate Nucleus) control what

Perception

Ganglion cells projecting to Superior colliculus control what

Orientation

Ganglion cells projecting to Pretectum control what

Light reflexes

Ganglion cells projecting to HYPOTHALAMUS control what

Diurnal cycles

What are the ganglion cells projecting to hypothalamus

ipRGCs (intrisically photosensitive), express melanopsin

Lateral Geniculate Nucleus layers

Koniocellular pathway

For COLOR
a pathway that starts with bistratified retinal ganglion cells and projects to the koniocellular layers of the lateral geniculate nucleus

What is a bistratified ganglion cell?

Koniocellular

where do synapses from LGN terminate?

Layer 4 of V1

What do simple cells of V1 do

Sum LGN inputs

How are V1 orientation clumps organized?

"Pinwheel"

Anatomical ocular dominance columns

neurons in V1 form these columns due to preference for one visual field for one eye
LGN has left/right stripes

Ocular dominance columns: where does right visual field information go?

From both eyes, goes to left side of brain

Layer 2/3 of V1

INTERBLOBS: Left and right visual field neurons from V4 synapse to "Disparity-selective" cells to understand DEPTH (pinwheel spaces)

BLOBS: Color-sensitive

V1-\> V2: where do BLOBS synapse to? And for what

Thin Stripes (color specific)

V1-\> V2: where do INTERBLOBS synapse to? And for what

Pale Stripes/Interstripes (spatial/orientation info)

describe how large receptive field motion specific parasol cells go to dorsal stream

Go through magnocellular stripes of LGN
Go from V1 to thick stripe of V2, then goes to DORSAL stream

describe how high resolution midget cells go to ventral stream

Go through parvocellular stripes of LGN
Go from V1 to pale or thin (depending on if color or spatial acuity used) stripe of V2, then goes to ventral stream

What is use of dorsal stream

Spatiotemporal info
Sends info to motor areas of frontal lobe

Striate to Extrastriate Cortex

Striate: V1
Extrastriate Cortex: V2, V4, etc.

Role of V4

Complex Shape perception (contours)

What is akinetopsia, what causes it

"Motion blindness" view world in snapshots
Due to lesions in V5/MT, deficit in motion perception
Normal spatial acuity, color vision

What path allows object recognition

Inferior temporal stream!!!
V2 -\> V4 -\> IT

Result of inferior temporal stream for object recognition

Object Constancy
ability to recognize object in variety of orientations

Orientation related matching tasks: which stream for perception, which for action?

VENTRAL for perception
DORSAL for action

What is Lateral Occipital Cortex important for, and which stream?

object shape perception
Ventral

What area is important for face recognition, and which stream?

Fusiform Face Area
Ventral

Describe reasons why FFA may be considered an area of expertise?

Activated when blind ppl touch faces
Activated in chess players, radiologists, birdwatchers, etc. for non human faces

What is sensation and perception?

sensation\=the process of receiving and representing stimulus by the nervous system
Perception\= the sensory input that is organized and interpreted
(hearing vs knowing sound)

What is a percept in nervous system

Mental representation of sensed stimulus

How are sensory systems "modality-specific"

Each subtype of sensory receptors responsive to single type of stimulus energy

sensory transduction

process of converting sensory signal to electrical signal

Describe general path of sensory transduction

Stimulus -\> Electrical signal (graded potentials or action potentials) -\> ganglion cells -\> thalamus -\> primary cortex -\> sensory cortices

What is a receptive field

deLimited medium where the stimuli can evoke sensory neuronal response

Better spatial resolution corresponds to Larger receptive fields or Smaller receptive fields

Smaller!

What is "valence" in chemical sensing

classification of odors as pleasant/attractive or unpleasant/repulsive

Why is it thought that olfactory pathway skips thalamus?

pyriform (olfactory) cortex

What kind of neuron are ORNs?

Bipolar

Are ORNs mylenated?

No, because they are so small don't have to travel far

What makes ORNs (Olfactory Receptor Neurons) special?

Are regenerated, because some get damaged

Describe apical surface of ORNs

Olfactory cilia (Microvilli) protrude into mucous

Where are odorant receptors embedded

Olfactory epithelium

With increasing receptor convergence you get \________ resolution and \_________ sensitivity

DECREASING resolution
INCREASING sensitivity

Olfactory system: Bipolar cell -\> Glomerulus
Is it convergence or divergence?

There is a mix of both.
1 bipolar cell may activate 8,000 glomeruli
1 glomerulus may receive info from up to 750 bipolar cells

Where are glomeruli found?

olfactory bulb

what forms olfactory nerve?

axons of glomeruli

Patterns of activation of olfactory receptors

COMBINATORIAL

Where is the pyriform (olfactory) cortex?

What is the pyriform cortex (PC)?

Primary Olfactory Cortex
Involved in processing/coding of olfactory info

What does pyriform cortex receive? (inputs)

highly converged inputs from glomeruli
extensive inputs from cortical/limbic systems

Where else does olfactory bulb target besides PC

Olfactory tubercle
Amygdala
Entorhinal cortex

Where does the entorhinal cortex project to?

hippocampal formation (memory)

vomeronasal organ

a portion of the mammalian olfactory system that is sensitive to pheromones

What is a pheromone

a chemical substance produced and released into the environment by an animal, especially a mammal or an insect, affecting the behavior or physiology of others of its species.

are there many pheromones compared to odorants?

No, few pheromones

Development of human vomeronasal organ

all embryos develop it, but is displaced during embryogenesis

Do adult humans have vomeronasal organs

Debated
Sweat pheromones exist though

Where are taste buds located?

Along the side of the papillae of tongue

what are taste cells

Specialized epithelial cells within taste bud, microvilli in saliva to contact tastants

Gustatory Pathway

Taste receptor cells -\> Ventral Posterior Medial Nucleus of thalamus -\> primary gustatory cortex

Does gustatory cortex have a map?

Yes, e.g. sweet tastes clustered together

What is sound?

Pressure waves through air evoked by quickly moving/vibrating objects

Physical Dimension of sound: Intensity

What is corresponding perceptual dimension?

Volume

Physical Dimension of sound: Frequency

What is corresponding perceptual dimension?

Pitch

Physical Dimension of sound: Complexity

What is corresponding perceptual dimension?

Timbre

What is range of sound for amplification by human ear (range of human speech)

3 kHz range

What do ridges of outer ear do?

Create frequency dependent sound level differences, we use for localization

What is the ossicle chain?

Joints of the middle ear:
- Tympanic Membrane
- Malleus
- Incus
- Stapes

Tympanic Membrane function

vibrates in response to sound waves
"Impedance matching" transfers signal in air to signal in aqueous fluid

Eventually causes stapes to push air into oval window

what is impedance matching in inner ear?

\>99% of sounds outside of water is reflected off water, does not pass thru
Same thing happens with air filled middle ear to fluid filled inner ear

How does middle ear deal with impedance?

Ratio between tympanic membrane (LARGE) and oval window (small) focuses the force
Mechanical advantage

How do waves enter inner ear

Scala Vestibuli, in through oval window

How do waves exit inner ear

Scala tympani, out through round window

What is function of cochlea?

It converts mechanical energy of the ear ossicles into electrical signals

What do hair cells do?

Detect traveling wave motion, tranduce cilia motion into neurotransmitter release

What forms the cochlear nerve?

Spiral ganglion cell axons

What vibrates in response to sound, and how does this create graded potentials?

Basilar membrane vibrates in response to sound, hair cells brush against tectorial membrane opening tip links and channels for ion influx

Does the basilar membrane have map?

Yes
TONOTOPIC map!