Psych 301 Sensation and Perception

What age-related macular degeneration (AMD) and retinitis pigmentosa (RP)? How are they similar and how are they different?

AMD is a disease associated with aging that affects the macula. Destroying the sharp central vision, making it difficult to read, drive and recognize faces. While RP is a hereditary disease that progressively kill off photoreceptors and degeneration of the pigment epithelium. Patients usually first notice problems with the peripheral vision under lowlight conditions. So the difference here is that AMD attacks the central vision while RP attacks ones periphal vision.

Describe the development of contrast sensitivity in infants and how it might be affected by developmental disorders such as amblyopia, strabismus or anisometropia.

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Describe the receptive field properties of retinal ganglion cells, LGN cells and V1 cells. In what ways are they similar and in what ways are they different? How do the response properties of the cells change from retina to LGN to V1?

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In what ways is the human eye similar to a camera? In what ways does it differ from a camera? Compare and contrast the functions to the physiology of the human eye.

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What are the similarities and differences between the trichromatic and color opponent theories of color perception?

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What is a hypercolumn in the primary visual cortex?

A hypercolumn is a 1 millimeter block of striated cortex containing two sets of columns, each covering every possible orientation (0-180 degrees) with one set preferring input from the left eye and one set preferring input from the right eye.

What is the Fourier analysis and why is it used for understanding perception? How is Fourier analysis related to the types of stimulus that psychophysicits use?

A mathematical procedure by which any signal can be separated into component sine waves at different frequencies; combining these component sine waves will reproduce the original signal. This analysis is use to understand perception because it allows scientists to better understand how very complex signals could be more easily as a combination of simple sine wave components. This relates to the other types stimuli

What is the difference between additive and subtractive color mixing?

Additive color mixing I'd a mixture of lights. Of light A and light B both reflected from a surface to the eye, in perception of color the effects of those two lights add togther. While subtractive color mixing is a mixture of pigments. If pigments A and B mix some of the light shinning on the surface will be subtracted by A and some by B. Only the remainder contributes to the perception of color.

What is an after image and what does it reveal about how color perception works?

Afterimage is a visual image seen after stimulus has been removed. This reveals that color contrast shown how the spatial relations between colors can influence color appearance. What you saw before has an influence on what you see now.

What is a unique hue?

Any of four colors that can be described with only a single color term: red,yellow, green, blue. Other colors e.g., orange and purple can be described as compounds (redish blue, reddish yellow)

Name three steps in color perecetiop as discussed in the textbook. And briefly discuss each one.

Detection, wavelengths must be detected. Discrimination, we must be able to tell the difference between one wavelength or mixture of wavelengths and another. And appearance we want to assign perceived colors to light and surfaces in the world and have those perceived colors be stable over time,regardless of different lighting conditions.

What is unique about face perception and how is it different than object pereception?

Fave perception is unique because viewpoint is very important for example upright faces are more recognizable than inverted faces. As to object reception, no matter the viewpoint of the the object one can recognize it.

Describe the concept of perceptual commitees.

It is a metaphor for how perception works. Commitees must integrate conflicting opinions and reach a consensus. Many different and sometimes competing principles are involved in percpetion. And perception results from the consensus that emerges.

What is the doctrine of specific nerve energies?

It states the nature of a sensation depending on which sensory fibers are stimulated, not on how the fibers are stimulated. Formulated by Johannes Müller.

What is the difference between MRI and fMRI?

MRI is an image technology that uses responses of atoms to strong magnetic fields to form images of structures like the brain. While fMRI is measures localized patterns of brain activity associated with blood flow.

Describe the following psychophysical methods: method of constant stimuli, method of limits, and method of adjustment.

Method of constant stimuli are many stimuli ranging from rarely to almost always precievable that are presented at one time. Method of limits is the magnitude of a single stimulus or the difference between two stimuli is varied increasingly until the participant responds differently. Method of adjustment is a method of limits in which the subject controls the change in the stimulus.

What kinds of processes happen in middle vision?

Middle vision involves with the perception of edges and surfaces. It also determines which regions of an image should be grouped together into objects.

Why do vision scientist study sine wave grating?

Scientists study sine wave gratings because patterns of stripes with fizzy boundaries are quite common. The edge of any object produces a single strip, often blurred by a shadow in the retinal image. The visual system breaks down images into vast number of components.

Describe how selective adaptation works and why is it useful for studying visual perception?

Selective adaptation is a reduction in response caused by prior or continuing stimulation. It is useful because it provides a powerful, noninvasive tool for learning about the stimulus specificity in human vision.

What is the difference between sensitivity and criterion in signal detection theory?

The difference is that sensitivity is a value defining the way an observer can tell the difference between the presence and the absence of a stimulus or the difference between two stimulus. While the criterion is an internal threshold that is set by observer.

Compare and contrast the structural description and view based approaches to understanding object recognition.

Structural description is a description of an obegct in terms of its parts and the relationship with those parts. While view based approaches suggest that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same shape in the brain.

What are the "What" and "Where" pathways?

The "where" pathway leads up to the parietal lobe. With visual areas seemingly important for processing information relating to the location of objects in space and the actions required to interact with them. Like hands and eyes. The "What" pathway heads down to the temporal lobe. This pathway appears to be the locus for the explicit acts of object recognition.

Explain the Gestalt grouping principles of good continuation, similarity, proximity, and surroundedness.

The Gestalt grouping principles of good continuation is a rule stating that two elements will tend to group together if they seem to lie on the same contour. In similarity it's a rule that the tendency of two features to group to water will increase as the similarity between them increases. Proximity is a rule that the tendency of two features to group together will increase ad the distance between them decreases. Finally in surroundness is a rule for figure ground assignment stating that if one region is entirely surrounded by another, it is likely that the surrounded region is the figure.

What is the difference between sensation and perception?

The difference between these two is that sensation is the ability to detect a stimuli and turn that detection into a personal and individual experience. While perception is when you give meaning to the detected sensation.

Describe the journey of light from the time it is emitted by the sun to the time it is registered by our eyes. In what ways is light reflected, refracted, transmitted and absorbed?

The journey starts by first encountering the cornea l, it is the window to the world. The light passes through the aqueous humor a fluid derived from blood behind the cornea. The light then passes through the pupil the hole in the structure of the iris to get to the lens. Then going through the vitreous humor which is another fluid that fills the vitreous chamber. Finally the light is brought to focus at the retina. The retina detects the light and tells the brain about the light and it's relation to objects in the world. Light is reflected by being redirected to something that strikes a surface usually back to its point of origin. Light is refracted by altering the wave of energy that passes into something from another medium. Light is transmitted by conveying something from one place or thing to another. Light is absorbed by taking up energy that is not transmitted at all.

What is the principle of univariance and what are the implications of the principle for color perception?

The principle of univariance is an infinite set of different wavelength intensity combinations can elicit exactly the same response from a single type of photoreceptor. This makes it impossible for the discrimination of colors. Color is psychophysical and not physical.

We all have a blind spot in each eye. In normal circumstances, why is it that we do not experience large black empty regions in our visual field?

The reason we don't experience large black empty regions in our visual field is because of the visual system, it fill it in with infraction from the surrounding area.

What is the difference between simple and complex cortical neurons in the primary visual cortex?

The simple cell is a cortical neuron whose receptive field has clearly defined excitatory and inhibitory regions. While the complex cell is another cortical neuron whose receptive field does not have cearly defined excitatory and inhibitory regions.

Describe various ways that our visual system adapts to darkness and allows us to see in low lighting conditions. Why are we said to have a duplex retina?

There are four main ways as to why our visual system allows us to see in low lighting. There are photopigment regeneration, the duplex retina and neural circuitry. It is said that we have a duplex retina because rods and cones work together in the retina to control our visual system when there's too much light and when there is low light.

What is the notion of reentrant processing in perception?

This processing involves wit the initial object recognition occurring very quickly. Then the brain continues to process information design signals up and down the "where" pathway. Object recognition should be seen as a conversations with many parts of the brain rather than a one way progression.

Describe two ways that visual acuity is measured.

Visual acuity can be measure by terms like 20/20 vision, your distance/normal distance and by Smallest visual angle of a cycle grating.

Describe the transmission of information in the retina from photoreceptors to the optic nerve. What cells are functioning in what order, and how do they transform visual information on the way to the brain?

When the signal reaches the final layer of the retina which are the ganglion cells the visual information has been received from photoreceptors via two neurons the bipolar cells ad amacrine cells transmitting the info to the brain via their axons that gather in the back of the eyeball emerging as the optic nerve.

Describe how the shape of the human lens and eyeball can cause blurry vision that requires correction. What are the differences between emmetropia, myopia, hyperopia, and astigmatism?

With different shapes of the human eyeball light rays entering the eye may not enter bent at a precise point of of focus on the retina creating blurred vision. Therefore people need glasses to correct the way light rays enters the eye to create a focus. Emmetropia is the condition where there is no refractive error, do there is no need for correction. Myopia is when light is focused in front of the retina and distant objects cannot be seen sharply. Hyperopia is when light is focused behind the retina and nervous objects cannot be seen sharply. And astigmatism is the unequal curving of one ore more of the refractive surfaces of the eye, usually the cornea.