Brain and Behavior Unit 3

Sensory Systems

Proprioception

Being able to detect where our bodies are in space, the information goes from joints to muscles.

Ex. Gymnasts and atheletes typically have better perceptions of where they are in space.

Thermoreceptors

These receptors tell the difference between warm and cold. They do not overlap on the skin surface.

They share the same pathway as pain (ascending.)

Some receptors are better at detecting warm or cold.

What are the two pathways from the brain to the spinal column?

1. Dorsal Columns
2. Anterolateral System (AKA. Spinothalamic)

Dorsal Columns

This pathway to the brain and spine, this column has a large diameter, is well-myelinated (for sending information), has well localized touch sensation, travels ipsilaterally and then crosses contralaterally at the medulla.

Anterolateral System (Spinothalamic System)

Compared to the other pathway, this has a small diameter, is not well myelinated, and travels contralaterally.

“Sensory Space“

* The zone (specific area)
* The modality (pressure, temperature)

Plasticity of Touch

Whenever something changes significantly or a certain stimuli happens repeatedly, the brain rearranges itself in response.

* Ex. Musicians, rats and when their whiskers are removed, loss of limbs.

Why do we need pain?

It informs the brain that there is possible tissue damage.

* Their are sensory and emotion responses to pain
* Emotional pain can be short term, or long term.

Nociceptors

These are receptors that are specialized to feel pain.

Congenital Insensitivity to Pain (CIP)

* Genetic, autosomal dominant
* Very vulnerable to injuries, leading to a shorter life expectancy.
* Typically, more mundane tasks will cause more wear on their joints, and they will not notice. (This includes when they are asleep.)
* This is a mutation of sodium channels in the nociceptors.

Where is pain processed?

* Anterior Cingulate Cortex
* emotional response and anticipation
* Prefrontal Cortex
* chronic pain, which may cause depressive symptoms.

Labeled Lines

These are particular neurons that are labeled for distinctive sensory experiences.

Meissner’s Corpuscle (Lamellate corpuscle)

A type of skin recepetor calls that detects light touch.

Merkel’s disc

This also detects light touches along the edges of surfaces.

Ruffini Corpuscle

These cells are sparsley distributed across the skin. These neurons detect stretching.

Free Nerve Endings

These cells are not specialized, but these cells typically detect pain and change in temperature.

Receptive Field

A specific sensory region that affects the activity of a cell in a sensory system. They are shaped like a donut, though they vary in shape and size.

Sensory Adaptation

Decrease in a receptor’s response to sustained stimulation.

phasic receptors

receptors in which the frequency of action potentials decrease rapidly as stimulus in maintained.

Tonic Receptors

Not as adaptable, declines slowly or not at all.

Central Modulation of Sensory Information. (CMSI)

The higher brain regions (the frontal cortex, thalamus) chooses to suppress some sources of sensory information and amplify others.

Polymodal Neurons

A neuron where more than one sensory modality converges.

Ex. A “visual“ neuron can also process sound or touch.

What are the 3 dimensions of pain?

1. Sensory-Discriminative Dimension
2. Motivational-Affective Dimension (emotional)
3. Cognitive-Evaluation (Mild or Agonizing pain)

Substance P

A peptide that boosts the pain response, and can remodel pain pathways. Without this peptide, we would only be able to feel mild pain.

Cingulate Cortex

A part of the limbic system that integrates pain, and activation correlates to discomfort. This cortex also activated when empathizing with someone.

Neuropathic Pain

This is after an injury has been healed for a long time, where the pain persists. An example of this is phantom pain.

Why is pain necessary?

It is necessary because it tells our body when tissue is being damaged so we can prevent further damage.

What are the 2 Fibers that carry pain info?

* A Delta fibers
* C fibers

Anterograde Amnesia

A type of memory loss that occurs when an individual can’t form new memories. Typically it is a temporary condition, but extreme cases can occur.

An example would be patient H.M.

Retrograde Amnesia

A type of memory loss that refers to the loss of information prior to the onset of amnesia.

Mnemonic Device: Think of retro as in the 80’s. 80’s is older, so that would be the key part to remember.

Semicircular canals

Relating to the vestibular system, these three fluid filled canals allow the body and brain to interpret where the head is in space. The three exist on a horizontal. superior, and posterior axis.

Ex. Think of these canals as a gyroscope, it can detext x, y, or x movement.

Synesthesia

This phenomenon is when one stimulation with one pathway activates another unrelated pathway. This stimulation is completely involuntary and can appear in several different forms.

Ex. projective and associative.

A projector synesthete may see an orange triangle when hearing a trumpet sound

A associator may strongly feel as though the trumpet sound is orange.

What are the 5 Modalities of Taste?

Sweet

Sour

Salty

Bitter

Umami

Are there taste regions on the tongue? For example, the back of the tongue tastes only bitter.

No, the entire mouth has capabilities to taste all modalities, no part of the tongue has specified modalities.

Hyperguesia

Also known as “supertasters,“ thes individuals have a heightened sensitivity to taste.

ex. Some people with this condition may find that overly seasoned food may overwhelm them.

These people, contrary to popular belief, do NOT have more taste receptors.

Anosmia

People with this condition experience a partial or total loss of smell. This condition can be temporary or permanent, depending on the cause.

ex. People who smoke may experience a total loss of smell.

Photoreceptors

These are found in the retina and detect light. Important for processing sensory information.

What are the two main types of photopigments?

Rhodopsin and Coneopsin/Photopsin

Rhodopsin

This photopigment is found in rods. They are more sensitive in low-light and do not detect color very well - if at all.

Coneopsin/Photopsin

There are three main types that respond to three different colors:

* Blue
* Green
* Red

Unlike rhodopsin, these photopigments require bright light in order to be able to break down.

Ganglion Cells

These cells form the optic nerve and send action potentials back to the brain. There are three main types of ganglion cells:

* Magnocellular
* Parvocellular
* Koniocellular

Information stays divided until it goes back into the cortex.

M Cells

Stands for Magnocellular cells, these are bigger cells that only process black/white color information BUT they are important to processing movement.

These ganglion cells only make up about 5% of the ganglion cells in our eyes.

P Cells

Stands for Parvocellular cells. These cells are much smaller than M cells, but they make up the majority of ganglion cells at around 90%. They process Red and Green information.

K Cells

Stands for Koniocellular cells, these ganglion cells take up the last 5%. They process blue and yellow information.

Cones

These visual receptors are able to detect color via wavelength. They are highly concentrated in the fovea, which means they have high visual acuity. Unlike rods, cones do not adapt well in low-light environments, as they need light in order to break down photopigments.

Cones are specified by what wavelength they detect, and not color.

For example: Short cones detect the color blue, and long cones detect red.

Rods

These visual receptors are concentrated in the peripheral retina, allowing us to detect movement and edges. They can only process information through black and white - but unlike cones, they can adapt to low-light situations.

For example: when you turn off the lights in your room, initially it is hard to see, but as your eyes adjust, you can make out shapes in your room.

Fovea

This is the very center of our retina, and only has cones. This allows us to detect color, and allows us to percieve details.

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Think of the fovea as a focal point when taking pictures. High detail on one part of the image, but everything else is blurry because it’s peripheral.

Blind spot

Otherwise known as the optic disk, this is where the optic nerve leaves the eye. This leaves a spot in our visual field where there are no photoreceptors.

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There are many optical illusions that can allow a person to find their blind spot.

Optic Chiasm

This is where half of the fibers of the optic nerve cross.

* The right visual field travels to the left hemisphere
* The left visual field travels to the right hemisphere

The part that crosses is called the nasal hemiretina.

Lateral Geniculate Nucleus (LGN)

* Most axons terminate on this tract
* This area of the thalamus recieves the majority (90%) of optic tract axons.
* The rest go to the superior colliculi or hypothalamus
* When this part of the thalamus recieves optic information, it directs the information to visual areas of the occipital lobe.
* information from both visual fields stay separated, we do not combine them.

Ex. When you cover one eye, you can see out of one eye, but you can also see that you are covering that eye.

Striate Cortex

Also known at the Primary visual cortex, this is where the majority of visual information first routes to. The organization is columnal.

Scotoma

This is the loss of vision in a specific part of the visual field. Typically, if you damage your eye in a specific spot, your eyes will still function properly, but the area corresponding to the damage in V1 will be unable to process incoming visual information.

Visual Agnosia

This is caused by damage from the ventral stream, where the individual fails to recognize objects based off of sight.

Ex. A person with this condition may not be able to recognize an apple by looking at it, but can still tells it’s an apple from other senses such as taste.

Achromatopsia

This condition is NOT due to eye damage - rather it is due to cortical damage. These individuals can no longer process color, and can only process black and white visual information.

Prosopagnosia

This is another condition that occurs due to ventral stream damage. Specifically, it is damage to the Fusiform Face Area. When an individual has this condition, they are unable to recognize faces. This can make discerning individuals from each other incredibly difficult.

Fusiform Face Area (FFA)

This area of the brain is located in the temporal lobe, and is activated when looking at someone’s face. This area is important for facial recognition.

Akinetopsia

This is the inability to process objects that are moving. This is caused by damage to a specific area of the dorsal stream.

* Someone with this condition would experience the world as a ‘stop motion‘ animation.

Optic Ataxia (Balint’s Syndrome)

A person with this condition would have difficulty interacting with objects, orienting around objects, etc. This is caused by specific damage to the dorsal stream.

Visual Reflex

This is when you detect something moving in your peripheral vision, and you turn to look at it.

What are the major pathways of visual processing?

* Ventral Stream
* Identifies Objects
* Facial information
* Dorsal Stream
* Guides our movement towards objects

How is pitch detected in the cochlea?

Certain pitches hit certain parts of the cochlea.

Ex. high pitches are at the start of the cochlea, and vice versa.

hair cells vibrate on a certain portion of the cochlea depending on pitch. (signal transduction)

* Sound is funneled
* Ear drum vibrates and causes ossicles to vibrate
* Fluid in cochlea vibrates, vibrating hair cells, which triggers action potentials
* Signal sent to the brain

How does the auditory system localize sound?