Perception Exam 1 Study Guide

What is the main difference between sensation and perception?

-Sensation is the conversion of physical parameters through specialized neurons (external, bottom-up)

-Perception is the internal interpretation of the sensory information (internal, top-down).

Which part of the brain deals with sensory integration?

The thalamus

What part of the brain deals with basic functions such as breathing and heart rate?

The brain stem

What are the 4 lobes of the brain?

-The frontal lobe

-The occipital lobe

-The temporal lobe

-The parietal lobe

What is the frontal lobe responsible for?

Reasoning

What is the occipital lobe responsible for?

Vision

What is the temporal lobe responsible for?

Auditory and Memory

What is the parietal lobe responsible for?

Bodily sensations

What is meant by the term cerebral cortex?

-The cerebrum is the outlet layer of the brain and the cortex is latin for surface.

-It essentially means the 4 lobes

Where is the cerebellum located?

Behind the brain stem (considered the little brain)

What does the cerebellum do?

It controls balance and movement

What is synthesia?

-Synesthesia is the crossing and combination of sensory perceptions.

-For instance, a person may hear someone’s name and see a specific color.

How does brain damage key us into what functions occur in the brain?

-Due to brain localization

-Specific functions of the brain can be found in specific areas; brain damage and its side effects can show this.

-For example, damage to the Wernicke’s area causes a person to speak nonsensical phrases. This indicates that this area is responsible for language control.

What is the resting potential of neurons?

-70 mV

What is an action potential?

Action potential is when a neuron fires due to an influx of sodium and the expelling of potassium.

What voltage triggers action potential?

-45mV

What voltage is seen at the top of an action potential?

+30mV

What part of the neuron is responsible for collecting neuro-chemical information?

Dendrites

Which part of the neuron carries the action potential travel?

Axons

What are the 2 main methods for objective information on the brain?

-Electro-Encephalogram (EEG)

-Functional Magnetic Resonance Imaging (fMRI)

How does an EEG operate?

By placing receptors on the surface of the scalp. Brain waves are then recorded as electromagnetic changes occur

How does an fMRI operate?

It records blood flow changes in the brain through the magnetization of iron to see the movement.

Absolute threshold

Minimal perceptible amount for stimulus to be registered by the nervous system (limits to perceiving sound or light)

Distance threshold

Smallest discernable changer between two stimuli (sound or color)

Corpus Callosum

The large bundle of nerve fibers that connects the left and right hemispheres of the brain, allowing for communication between them.

Gray Matter

The outer cortical layer of the brain made up of neuronal cell bodies

White Matter

Connecting axons and connecting fibers of neurons that extend throughout the brain

What is the range of the visual spectrum?

370 nm to 730 nm.

Name 2 kinds of light that is below the visible spectrum?

Microwaves and radio waves

Name 2 kinds of light above the visible spectrum?

UV rays and X-rays

As a waveform gets larger, what happens to its frequency?

Frequency decreases

Why does a leaf appear green to the eye?

A leaf appears green to the eye because it is the only color that is reflected instead of absorbed.

What part of the eye contains the largest amount of cones?

Fovea

If something is in your right visual field, which part of the retina does it hit?

Left side of the retina

How does the field of vision change among prey animals or predators?

-In animals that are prey, their field of vision is more horizontal which increases environmental awareness and field of vision.

-Animals that are predators have a better field of vision for hunting prey and forward facing eyes: with increased depth perception and a better ability to track motion.

What muscle is responsible for contracting and restricting the pupil?

The iris

Why does the pupil contract? What purpose does it serve for vision?

-The pupil is the opening of the eye and is responsible for the amount of light that enters the eye.

- If a pupil contracts, it is letting in less light to adjust to a brighter environment.

What muscle changes the focal length of the lens?

The ciliary muscles

How does the process of refraction aid in vision?

Refraction changes the direction of light. The cornea is also curved and able to refract light.

Which photoreceptor is responsible for daylight acuity?

Cones

Which photoreceptor is responsible for detection in low light?

Rods

Which cell in the eye is responsible for edge detection or detecting luminance contrast?

Horizontal cells

Describe the through pathway

It goes from the rods and cones to the bipolar cells to the retinal ganglion cells.

Describe the lateral pathway

Horizontal cells to and from photoreceptors

Amacrine cells to and from bipolar cells and to RGCs

Amacrin (motion and visual blur) and horizontal cells (edge detection)

What is photoisomerization?

The change in shape in a photopigment

How does photoisomerization help the photoreceptor activate?

When enough photopigment change shape, photoreceptors fire

What are the 3 types of cone cells? What is distinct about their function?

The three types of cone cells are the L-cones, M-cones, and S-cones.

L-cones deal with reds, M-cones deal with greens, and S-cones deal with blue and violet

Describe the rod-cone break?

The rod-cone break is when the rods increase its sensitivity at around 8 minutes. This is the point at which the cones and rods meet during the process of dark adaptation.

What is the operating range of the retinal ganglion cell in terms of firing rate?

1 to 100 times per second

What occurs if a light source is below the RGCs operating range?

If a light source is below the RGC’s operating range, it may not active the receptors.

What does the term convergence refer to when discussing the RGCs?

-Convergence is the distance of retinal ganglion cells from the center of vision to the outer part of vision.

-High convergence means there are a lot of RGCs, meaning they are getting a lot of information. The reverse goes for low convergence.

Describe the role of simple cells in the visual cortex.

Simple cells respond to preferred orientation and luminance contrast in selective areas in the visual field. They also account for the minimal processing of parameters like color or motion.

*ORIENTATION TUNING CURVE

How do complex cells differ from simple cells (2 ways)

-Luminance contrasts in both the dark bar in a light background and the light bar in a dark background

-Respond anywhere instead of selective activation

What is meant by retinotopic organization in the visual cortex?

The similar mapping of the visual field covered by RGC that is mirrored in the primary visual cortex of the brain

What is the main difference between the optic nerve and the optic track?

-The optic nerve has information from both eyes and occurs before the optic chiasm

-The optic nerve has information from one eye and occurs after the optic chiasm

Why is the optic chiasm important?

The optic chiasm is important because it is where the RGC neural fibers meet and signals are split to the other side of the brain.

What is meant by contralateral representation?

When the right visual field is being interpreted by the left side of the brain while the left visual field is being interpreted by the right side of the brain.

Describe the term ocular dominance and how it applies to the LGN?

Ocular dominance is when the brain receives information from one eye.

This applies to the LGN as it occurs for layers 1, 4, and 6 for the contralateral eye and layers 2, 3, and 5 for the ipsilateral eye.

What is the difference between the parvocellular and magnocellular layers of the LGN?

-The magnocellular layers of the LGN deal with motion

-The parvocellular layers deal with pattern, color, shape, and depth.

Describe the Orientation Tuning Curve and what it means in terms of visual recognition?

The orientation tuning curve is when simple cells have different preferred orientations. The visual field is a bunch of lines that cells are aware of. Our brain responds to the orientation of lines and bars of light and fires more or less cells depending on on its preferred orientation.

What is Cortical Magnification and how does it apply to processing the retinal image in the cortex?

When there’s more cortex for the center of vision and the fovea has more RGCs therefore, more information processing occurs at the center of vision than any other part of the eye. 

Which two lobes of the brain are involved in the "what-pathway" of visual processing?

Occipital and temporal

Which parts of the lateral geniculate nucleus are involved in the "what-pathway"?

Parvocellular layers

What is the main purpose of the what pathway?

Perceiving visual information and categorizing, organizing, or identifying (like color)

Which two lobes of the brain are involved in the "where-pathway" for visual processing?

Occipital and parietal

Which parts of the lateral geniculate nucleus are involved in the "where-pathway"?

Magnocellular

What is the main purpose of the where pathway?

 Processing of motion and spatial recognition.

What is perceptual inference? How does it affect our perception of the environment?

Perceptual inference is when the brain fills in the scene due to expectations from the environment.

Perception is affected as there is more interpolation and activity when this occurs. 

Does neural activation increase or decrease during moments of perceptual inference?

Increases

How does the brain encode similarities in visual processing?

Neural synchronization (similar firing rates of neural groups)

Name 2 ways that the brain makes sense of stimuli in terms of perceptual grouping?

Common motion and proximity

What is the main role of the V4 neuron?

The main role is to gather information from V1 cells and condense it to give to infrotemporal neurons.

Color, pattern, etc.

Where do V4 neurons source its information from?

V1 cells

What do V4 neurons respond to?

Particular shapes or contours.

What is the main role of the Inferotemporal neurons?

Inferotemporal neurons represent and recognize whole objects.

Where does the inferotemporal neuron source its information from?

It combines information from V4 cells.

What is meant by James Letvin's idea of the grandmother neuron?

It means that one cell represents and fires to one particular object or idea.

Why is the distributed model of representation important?

It shows that memory connects to other different parts of the brain to be able to identify objects

What does the distributed model of representation tell us about visual processing?

It tells us that the infratemporal lobe identifies the stimuli but other areas are responsible for things like language

Describe visual agnosia. What it means for an individual diagnosed with it?

Visual agnosia is when a person can identify the color and shape of objects but cannot identify them visually. This means a person has to identify things through touch.

Damage to the “what” pathway

What is the top-down model of information processing?

The top-down model of information processing is when the brain identifies stimuli based on context. This includes individual attention, knowledge, and goals.

How does top-down information influence our perceptual representation?

Inferences are made based on comparing memory to current perceptions.

Which part of the eye contains photoreceptors, responsible for converting light into electrical signals?

The Retina

Which part of the eye is the white outer protective layer?

Sclera

Which part of the eye is connected to ciliary fibers to change the point of focus?

The lens

What is the process of visual processing

1. Retinal pathway (through and lateral)

2. Lateral Genicular Nucleus (Magno levels 1&2 for motion, Parvo 3—6 for pattern)

3. V1 (orientation!)

4. V4 (Shape, contour, color)

5. Inferotemporal cortex