Neuropsychology Test 2

Chapters 8,9,13,14 (need to add 15 and 16)

Sensation and perception are related

But they are also distinct

Sensation

Changes in the sensory system in response to the environment

perception

interpretation of the changes to the environment

Sensory receptors are sensitive to a particular stimulation in the environment

sensory receptors only respond to that specific part of the environment

In the case of vision, people who are color deficient have a different experience than

people who are not color blind

In the auditory system, humans can detect sound between

20 and 20,000 Hz, whereas some animals can hear up to 120,000 Hz

Most common form of color deficiency

red-green deficient

The long wavelength cone is encoded by a gene on the X chromosome, so a mutation in this gene is more likely to impact

males than females, making this red-green deficiency more common in men than in women

Electromagnetic Spectrum

The human eye sees only a slice of electromagnetic energy from about 400 nanometers (violet) to 700 nanometers (red).

Butterflies and honeybees can detect light in the

ultraviolet range

Night vision devices make use of

infrared light waves

A nanometer (nm) is

one-billionth of a meter

Receptors in each system are specialized to

convert a particular stimulus into electrochemical signals in the nervous system

Vision uses photoreceptors to

convert light

Audition uses vibration frequency to

convert sound

Somatosensory systems use mechanical pressure to

convert touch

Taste and olfaction use molecular shape to

activate specific receptors

Stretch-Sensitive Channels

Tactile stimulation of a hair activates stretch-sensitive Na⁺ channels, which then activate voltage-sensitive channels to produce an action potential.

Stretch-Sensitive Channels Process

1) displacement of hair 2) causes stretch sensitive channels on dendrite to open, allowing an influx of Na+ 3) Na+ influx causes voltage-sensitive Na+ and K+ channels to open, producing a nerve impluse

Receptive Fields Locate

Sensory Events

Every receptor has a

receptive fieldre

The receptive field defines

what part of the external world the receptor responds to

In vision, a particular photoreceptor receives information from

a particular part of the image in front of you

For somatosensation, different receptors convey information about

touches to a specific part of the body

Receptive fields for taste, smell, and audition are less clear.

For the auditory system, those are likely the specific frequencies of sounds. For taste and smell, the receptive fields may be the physical properties (shapes) of the molecules the receptors respond to.

Receptors Identify

Constancy and Change

Some receptors remain stimulated for as long as the stimulus is present

others respond only when there is a change in the stimulus

Rapidly adapting receptors detect the change, and then adapt to

the stimulation by returning to their baseline firing rate

Slowly adapting receptors respond to the stimulus and keep responding

for as long as the stimulus is present

Receptors Distinguish

self from other

Exteroceptive receptors respond to

events outside of your body

Interoceptive receptors respond to

stimuli inside our body

Information from both types of receptors (exteroceptive and interoceptive)

is combined to create our understanding of the world

Imagine looking at the scene while you are walking along. Your exteroceptors in your eyes see the world around you, but that image on your retina is constantly changing as you move

The interoceptors account for your movements and essentially remove it from what you see in the world, so the world appears to remain stable, even though the stimulation to the photoreceptors in the eye is constantly changing

Receptor density determines

Sensitivity

The sensitivity of the system is related to

how closely together the receptors are

If the receptors are closer together, you can differentiate between

a stimulus that activates one receptor and a stimulus that activates a nearby receptor

If receptors are wide apart and have large receptive fields

stimulation anywhere in that receptive field will be perceived in the same way

Two-point sensitivity measures

how closely two stimuli can be placed and still identified as different

The tight clustering of cone cells with small receptive fields in the fovea give us

detailed color vision at the center of our visual field. The rod cells found in the rest of the retina provide less detail

Neural relays determine

motor responses

Sensory information is relayed to the brain through how many steps?

3-4 steps

The signal can be modified or behavior can be evoked at

any of the relay points

Reflexive movements away from painful stimuli are coordinated at the level of?

The spinal cord

Understanding what and where the pain is requires

requires involvement of the brainstem and cortex

Some auditory and visual processing take place in the brainstem

whereas recognizing patterns requires the cortex

Descending signals from the cortex can alter how likely it is

for sensory information to be passed on at each relay point

When engaged in an activity, such as a sporting event, you might not notice an injury.

It may be after the play or after the game that you notice a bruise or a sprain.

Central Organization of the Sensory Systems

All sensory information, regardless of the system, is encoded as action potentials

The nervous system and brain segregate sensory information into

different pathways

Different populations of neurons might encode

qualitative difference such as red vs. green

The frequency of action potentials might encode

quantitative differences such as a louder or quieter sound

Different types of sensory information are directed to

different parts of the cortex

People with synesthesia seem to have increased connections between different sensory areas

the number 1 may always be tinged blue or the number 2 may be orange. A chef with synesthesia reports that tastes are associated with shapes, so he describes one dish as “spikey” or another dish as “round”.

Visual Subsystems

Each pathway from eye to brain, numbered 1 through 7 here, traces a sensory subsystem that culminates in a neural visual center.

Frontal eye fields

eye movements

suprachiasmatic nucleus

daily rhythms (sleep, feeding, etc)

Pretectum

changes in pupil size in response to light

pineal gland

long-term circadian rhythms

superior colliculus

head orienting

accessory optic nucleus

eye movement to compensate for head movement

visual cortex

pattern perception, depth perception, color vision

visual subsystems 1-7

frontal eye fields, suprachiasmatic nucleus, pretectum, pineal gland, superior colliculus, accessory optic nucleus, visual cortex

Sensory systems represent

the external world within the brain

For each sense, there are multiple

topocographic maps

Greater number of representations is associated with

greater behavioral complexity

The primary sensory area initially processes the information

Secondary (and higher) areas perform more elaborate processing or focus on specific aspects of the stimulus

Anatomy of the Eye

Light reflected from an object is focused by the lens on the fovea of the retina

Light enters the eye through X and X and is focused on these X at the back of the eye

Light enters the eye through the cornea and lens and is focused on the photoreceptors at the back of the eye

Passing through the lens, the resulting
image is

upside down and
left-right reversed on the retina

On most of the retina, light must pass through

several layers of translucent cells to reach the photoreceptors

In the fovea, these overlying cells are shifted aside to

allow light more direct access without as much scattering

The fovea

(A) The fovea of the retina features densely packed cones. The relay cells to which the receptors connect are pushed to one side to reduce the interference to light making its way to the cones.

The retina contains two types of photoreceptors

rods and cones

Rods

Sensitive to broad spectrum of light

Sensitive to low levels of light

Found throughout the retina

Cones

Short, middle, and long wavelength cones are sensitive to specific wavelengths of light, which we perceive as color

Sensitive to higher intensities of light

Found in the retina

All photoreceptors synapse on

bipolar cells and ultimately onto retinal ganglion cells, which form the optic nerve

In bright light, looking directly at an object will provide

the highest-resolution image

Under dim light conditions, such as when looking at the stars, looking directly at an object can make it

disappear because the cones are not as sensitive in low-light conditions. To see dim stars, you are better looking off to the side of the star and seeing the star of interest with your peripheral (rod-based) vision.

The axons of the retinal ganglion cells come together to form

form the optic nerve, which exits the eye through the “blind spot”

the optic nerves from the two eyes combine

At the optic chiasm

Information from the right half of each retina, which perceives the left side of the visual field, projects to

the right hemisphere of the brain

Information from the left half of each retina, which perceives the right visual field, projects to

the left hemisphere of the brain

Crossing the Optic Chiasm

Dorsal view of the visual pathways from each eye to region V1 in each occipital hemisphere. Information from the right (blue) side of the visual field falls on the left halves of the retinas and ends up in the left  hemisphere. Information from the left (red) side of the visual field falls on the right halves of the retinas and travels to the right hemisphere. In animals such as humans, with eyes at the front of the head, about half of the optic fibers cross at the optic chiasm.

The main visual pathway leads from the eye to

the lateral geniculate nucleus (LGN) of the thalamus to the primary visual cortex

Main visual pathway is also called the

striate cortex

The LGN is divided into six layers, and the topographic mapping of the information on the retina is

maintained in the LGN

Ipsilateral eye projects to

layers 2, 3, and 5

Contralateral eye projects to

layers 1, 4, and 6

LGN projects to layer IV of the primary visual cortex, with input from

the left eye alternating with input from the right eye, resulting in a striped appearance

The geniculostriate pathway is the name for the primary visual pathway

Damage to this pathway results in impairments in the ability to recognize form, color, or motion

Geniculostriate Pathway

Next pathway relays through the lateral geniculate nucleus (LGN) of the thalamus

In the Geniculostriate Pathway, LGN projects to

the primary visual cortex or striate cortex or V1

V1contains a retinoptic map of the visual field

Map is upside down, inverted, and reversed

Geniculostriate Pathway takes part in

pattern recognition and conscious visual functions

Tectopulvinar Pathway 

Optic nerve leaves the eye and projects to the superior colliculus (optic tectum)

In the Tectopulvinar Pathway, the optic nerve projection reaches

visual areas in the temporal and parietal lobes through relays in the lateral posterior-pulvinar complex of the thalamus. It also detects stimuli and helps orient us to stimuli.

This pathway is sufficient to locate objects in space, but does not provide as much detailed information about the object viewed

Tectopulvinar Pathway 

Sound is made up of

pressure variations in the air

audition can be used for

sound localization, echolocation, spoken communication, and music