Neuroscience Exam 2

Retina

dots - simple selectivity

MT

direction and speed of visual motion

V1

responds to edges

V2

texture

V4

selective for the shape of particular points in an object (shapes)

IT

placing objects into specific categories (inferior temporal cortex - identifying objects) 

Side selective neurons

small receptive area fields, only responded if there was an object to their left side (objective selective)

White Light

all frequencies are equally accepted

How vision turns light into electrical current?

The eye projects light on a bed of photoreceptors 

dense packing of photoreceptors in center

fovea

periphery, low light

rods

center, color

cones

does not change shape - refracts light rays

cornea

changes its shape to find-tune that image on the retina 

lens

Myopia

• Common vision problem with young people 

• Nearsightedness - difficulty seeing distant objects 

  • Develops if the eyeball is too long

do rods, cones, bipolar cells, and horizontal cells produce action potentials?

No, only graded, local potentials

Scotopic System 

• Rod based system 

• Very sensitive, works well in low light 

  • Insensitive to color 

Photopic System 

• Cones based system 

• Less sensitive 

• Requires more light to function 

  • Differential sensitivity to wavelengths, enabling our color vision 

Cone response =

(aborption spectrum) x (light intensity) 

What is sensory transduction?

The process of converting stimulus energy into a change in electrical potential across a receptor cell membrane

What happens when a receptor potential exceeds threshold?

Action potentials are generated and travel via sensory nerves

Phasic receptors show a progressive decrease in their response to sustained stimulation. True or false?

True

What is a receptive field?

A region of space where a stimulus can alter a sensory neuron's firing rate

Which statements about sensory adaptation are supported by the notes?

It is a progressive decrease in a receptor's response to sustained stimulation

Not noticing the touch of clothes on your skin is an example

Which system carries most pain information from the body to the brain?

anterolateral, or spinothalamic, system carries most pain information from the body to the brain.

Neuropathic pain can persist long after the injury that originally caused it has healed. True or False?

True

What is the normal job of TRPV1

To detect a rise in temperature

Which methods are described in the notes as ways of relieving pain?

TENS, acupunture, placebo effects

What are polymodal neurons?

Neurons upon which information from more than one sensory system converges

• Polymodal neurons receive converging information from more than one sensory system, allowing sensory systems to interact.

Which two mechanisms are listed in the notes for determining the intensity of a stimulus?

Firing frequency + receptor recruitment

What does the dorsal column system primarily deliver to the brain?

Most touch stimuli

a strip of skin innervated by a particular spinal dorsal root.

dermatome

What is central modulation of sensory information?

Higher brain centers suppressing some sensory information and amplifying other information

Which statements about pain and nociceptors are supported by the notes?

Nociceptors respond to stimuli that produce or threaten tissue damage

• Serotonin and histamine can stimulate nociceptors

Immediate short-term pain can cause reflexive withdrawal

Placebo effects may activate the brain's ______ _____ system.

endogenous opioid

Alters the brains perception of pain

hypnosis

Uses both opioid and non-opioid mechanisms

Stress

May activate endorphin-mediated pain control system

cognitive (learning)

Bind to opioid receptors in periaqueductral gray and spinal cord

opiates

Block chemical inflammatory at the site of injury

Anti-inflammatory drugs

Act in nociceptor endings, spinal cord, and brain

cannaboids

On large fibers, blocks or alters pain signal to brain

TENS

Activates endogenous opioids and/or placebo-like effect, possibly modulating effect on activity of peripheral pain pathways

Acupuncture

Electrically activates endorphin-mediated pain control systems, blocking pain signal in spinal cord

central gray

a sensory neuron consists of a region of space in which a stimulus will alter that neuron's firing rate 

receptive field

show little or no adaptation (often pain sensors)

tonic receptors

What is a motor plan?

A complex set of muscle commands established before an act occurs

What does electromyography (EMG) measure?

EMG records muscle electrical activity to track movements involved in an act.

Muscle spindles respond primarily to muscle length.

True or False?

True

Which statements about Golgi tendon organs are supported by the notes?

They detect overloads that may threaten muscles and tendons

they are found within tendons

they monitor the force of muscle contractions

What is the primary role of the ventral visual processing stream?

identifiying objects

Rods are more numerous than cones in the fovea.

True or False?

False

What is proprioception?

Information about body position and movement

Which condition is associated with widespread destruction of the basal ganglia?

Hungtitons Disease

allows sensory systems to cover a wide range because different receptor cells specialize in different portions.

range fractionation

Photoreceptors in the periphery of the retina are mostly what type of cell?

Rods

A single cone type can uniquely determine color if no other information is available

False

Rods are most common in the fovea

false

cones are most common - rods are in the periphery

a tuning curve shows a neurons spike rate as a function of a stimulus

true

V1 neurons are commonly tuned for what feature?

Orientation

IT cortex neurons can respond selectively to faces

true

Receptive fields in the retina are larger than in cortical area IT

false

A neural rate code uses what feature of spiking?

average spikes per unit time

The labeled line hypothesis states that an action potentials meaning depends on its temporal pattern

false

Neural plasticity can cause cortical maps of body parts to reorganize only during early development

falsee

Primary motor cortex damage is most likely to cause:

paralysis

In bayesian inference, what does the prior represent

beliefs before seeing data

A likelihood function represents how proable the data are under different parameters

true

In bayesian model, less reliable measurements lead to a posterior biased away from the prior

false

Normative models are used to explain why neural systems might be non-optimal for certain tasks

false

In color vision, cone responses can be modeled as linear functions of the light spectrum

true

Many V2 neurons encoe texture statistic

true

Orientation tuning first appears strongly in the LGN

false

Complex cells in V1 are more sensitive to the exact position of an edge than simple cells

false

V4 neurons can be selective for object size only

false

IT cortex shows no selectivity for the category of objects

false

ON-center retinal ganglion cells increase firing when a bright light is in the surround

false

they decrease, and increase when light illuminates the center

Parkins disease is caused by loss of dopaminergic neurons in the:

Substantia nigra

The posterior in Bayesian inference conbines the prior with the:

Likelihood

Which area shows very large receptvie fields and category selectivity

IT cortex

Which part of the retina has the densest cone packing

Fovea

Mirror neurons respond when you perform an action and when you:

Watch someone perform the same action

Normative models attempt to explain:

how neural systems optimize behavior

As measurement noise increases, the posterior shifts:

toward the prior

The parameters of a probability distribution do not influence samples drawn from that distribution

false

Neural responses are perfectly consistence each time a stimulus is presented

false

Bipolar cells in the retina are always excited by glutamate

false

there are more rods than cones in the fovea

false

In cone space, which LMS vector is consistent with white light?

[1,1,1]

What type of neuron in the retina sends an axon in the central nervous system?

retinal ganglion cell

Typically how many cone types are there in the fovea of the human eye

3

The ____ of a sensory neuron is the region on the body that causes the cell to alter its firing rate

receptive field

Sustaiend stimulation of a sensory receptor results in a reduction in receptor sensitivity called:

sensory adaptation

The representation of the human body in the somatosensory cortex especially emphasizes the:

hands

Which statement about cones is correct?

cones provide high-acuity color vision W

What is a linear receptive field model?

a dot product between model weights and inputs

Tendency of rods and cones to adjust their light sensitivity to match current levels of illumination 

Photoreceptor Adaptation