PSY 280: Final Exam

Sensation

The result of the physical interaction between the world and our bodies

Sensory Transducer

A receptor that converts physical energy from the environment into neural energy

Perception

The processing and interpretation of neural energy from sensations

The Senses

* Touch
* Balance
* Vision
* Taste
* Hearing
* Smell

Events Leading to Perception

1. Capturing physical energy
2. Physical Stimulation
3. Transduction into Neural Signals: Sensation
4. Transmission of neural signal to the brain
5. Cortical Processing: Perception
6. Active Feedback

Nativism

The idea that the mind produces ideas that are not derived from external sources, and that we have abilities that are innate and not learned.

Empiricism

* The idea that all knowledge comes through the senses.
* According to this view, perception is the source of all knowledge about the world
* Modern science largely subscribes to this view.

Dualism

The idea that mind has an existence separate from the material world of the body

Materialism

The idea that the only thing that exists is matter, and that all things, including the mind and consciousness, are the results of interaction between bits of matter

Panpsychism

The idea that the mind exists as a property of all matter, that is, that all matter has consciousness (i.e. the whole is somehow more than the sum of its parts).

Psychophysics

* Invented by Gustav Fechner.
* The idea that we can learn about the perceptual process through the empirical measurement of organism's behavioral responses to stimuli
* The science of defining quantitative relationships between physical and psychological (subjective) events.

Weber's Law

The law that states that as a stimulus intensity grows, larger changes are needed to be detectable (i.e. the requirements for a just noticeable difference increase as the physical intensity increases).

Affordances

* The opportunities for action provided by a particular object or environment.
* Essentially used to describe the relationship between an object and a person.

Absolute Threshold

The minimum stimulation needed to detect a particular stimulus 50 percent of the time

Two-Point Threshold

* Minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli
* Depends on the part of the body

Just Noticeable Difference (JND)

The smallest detectable difference between two stimuli, or the minimum change in a stimulus that can be correctly judged as difference from a reference stimulus.

Signal Detection Theory

* A psychophysical theory that quantifies the response of an observer to the presentation of a signal in the presence of *noise* (i.e. how likely are the able to distinguish a stimuli among background noise).
* Distinguishing calls are dependent on sensitivity (d') and criterion.

Criterion

* An internal threshold set by the observer (the vertical dotted line in SDT graphs) for determining if a specific sound is present among noise.
* If the perceived stimulus intensity passes the threshold, then we guess 'yes'.
* There is usually potential for a false alarm as some instances of 'noise alone' may occur past the threshold.

Sensitivity (d')

* The ease with which an observer can tell the difference between two stimuli
* This means less overlap, which means less potential for false alarms and misses
* Ultimately, greater is better

Patch Clamp

Measurement Technique used to study individual ion channels

Electroencephalography (EEG)

Measures electrical activity from population of many neurons using many electrodes on the scalp

Event-Related Potential (ERP)

A measure of electrical activity from a subpopulation of neurons in response to particular stimuli that requires averaging many EEG recordings

Electrocorticography (ECoG)

A type of EEG that is recorded through electrodes placed directly on top of the brain (invasive surgery)

Magnetoencephalography (MEG)

Measures changes in magnetic activity across populations of many neutrons in the brain

* Better localization than EEG

Magnetic Resonance Imaging (MRI)

Measurement that uses the responses of atoms to strong magnetic fields and radio frequency pulses to form images of structures like the brain

Functional Magnetic Resonance Imaging (fMRI)

* Measures localized patterns of activity in the brain
* Activates neurons provoke increased blood flood which are quantified by measuring the changes in oxygenated and deoxygenated blood

Positron Emission Tomography (PET)

Identifies neural activity by measuring the metabolism of brain cells using safe radioactive isotopes

Transverse Waves

* Waves in which the particles move perpendicular to the direction of motion (like an ocean wave).
* Light is composed of two perpendicular waves of this type (electric and magnetic).

Longitudinal Waves

* Waves in which the particles move parallel to the direction of motion (like an accordion)
* Sound waves are this type. In open air, they travel radially outward from the source, whereas in a closed space (like a tube) they travel in one direction

Absorption

Energy that is taken up, and is not transmitted at all

Diffraction

* Waves encounter an obstacle and bend around it.
* This effect is more pronounced on long wavelengths than short wavelengths.

Reflection

Energy that is redirected when it strikes a surface

Transmission

Energy that is passed on through a surface (when it is neither reflected nor absorbed by the surface)

Refraction

Energy that is altered as it passes into another medium

Cornea

* The transparent “window” into the eyeball
* One of the major players in the refraction of light as it enters the eye

Aqueous Humor

* The watery fluid in the anterior chamber
* Delivers oxygen to parts of the eye

Pupil

* The dark circular opening at the center of the iris in the eye, where light enters the eye
* The first place where light is manipulated

Crystalline Lens

The lens inside the eye that enables changing focus

Ciliary Muscle

The muscle responsible for changing the shape (focus) of the lens; responsible for *accommodation*

Vitreous Humor

The transparent fluid that fills the vitreous chamber in the posterior part of the eye

Retina

* A light-sensitive membrane on the back of the eye that contains rods and cones
* Where transduction occurs

Fovea

* Part of the retina where the focus of our vision is directed
* Has the highest concentration of cones out of anywhere on the retina, which enables very high visual acuity

Optic Disc

* The gateway where neural information leaves the eye and travels to the thalamus
* There are no rods and cones here, creating a blindspot

Accomodation

Alteration of the refractive power through the change of the lens to focus light rays

Emmetropia

The happy condition of no refractive error

Myopia

Light is focused in front of the retina and distant objects cannot be seen sharply; *nearsightedness*.

Hyperopia

Light is focused behind the retina, near objects cannot be seen sharply; *farsightedness*.

Astigmatism

* A visual defect caused by the unequal curving of one or more of the refractive surfaces in the eye
* Usually the cornea

Cataracts

Loss of transparency in lens

Presbyopia

* Inability to accommodate nearby objects due to the decreased effectiveness of their ciliary muscle
* “Old Sight”

Photoreceptors

Cells in the retina that initially transduce light energy into neural energy

Photoreceptors that are specialized for night vision

Rods

Cones

Photoreceptors that are specialized for daylight vision, fine acuity and color

Visual Pigments

Light absorbing molecules created and used by photoreceptors

Chromophore

Light-catching part of pigment

Graded Potentials

The more photons, less neurotransmitters

Degrees of Visual Angle

* Measure size by how large an image appears on the retina
* The width of your thumbnail is about 2° of visual angle at arms length

Lateral Inhibition

* The pattern of interaction among neurons in the visual system in which activity in one neuron inhibits adjacent neurons' responses
* Helps the retina better localize edges/where the signal is coming from

Diffuse Bipolar Cells

Receive input from multiple rods

Midget Bipolar Cells

* Receive input from a single cone
* On: Responds to increases in light
* Off: Responds to decreases in light

Bipolar Cells

Neurons in the middle layer of the retina that transfer information from the photoreceptors to the ganglion cells

Ganglion Cells

* Cells at the front of the retina that take input from bipolar cells
* The last stage before information leaves the eye

P Ganglion Cells

* Small Cells
* Involved in fine visual acuity, colour, and shape processing
* Have good spatial resolution and poor temporal resolution
* Connected to parvocellular pathway

M Ganglion Cells

* Large Cells
* Involved in motion processing
* Good temporal resolution but poor spatial resolution
* Connected to magnocellular pathway

Receptive Field

The region in space in which stimuli will activate a neuron

The 4 Mechanism for Dark and Light Adaptation

* Pupils regulate the amount of light entering the eye
* Photopigment Regeneration limits amount of captured light
* Photoreceptors different sensitivity to light
* Ganglion Cells ignore variation in overall light level via centre-surround contrasts

Retinis Pigmentosa

A family of hereditary diseases that involve the progressive death of photoreceptors and degeneration of the pigment epithelium

Macular Degeneration

* Type of disease that results in the progressive degeneration of the macula (fovea)
* Impairs central vision and sharp details

Acuity

The smallest spatial detail that can be resolved

Snellan Chart

* A chart used to test visual acuity
* At 20 feet away, subjects are asked to read various lines of text with differing sizes

Landolt Rings

* A chart used to test visual acuity
* Consists of "C's" oriented in different ways at different sizes. Subjects asked to identify which side of the ring has the gap.

Spatial Frequency

The number of cycles of a grating per unit of visual angle (usually specified in degrees)

Contrast

The difference in illumination between a figure and its background

Contrast Threshold

* The minimum contrast to detect a pattern at a specific spatial frequency
* Smaller values = higher visual acuity

Contrast Sensitivity

* The inverse of contrast threshold
* Describes at what contrast we can still make out gratings given a specific spatial frequency
* Higher values = higher visual acuity

Photopic

* Daylight vision
* This is when we experience the best contrast sensitivity
* Light intensities are bright enough to stimulate cone receptors and bring enough to saturate rod receptors

Mesopic

* Twilight Vision
* Worse contrast sensitivity that photopic but better than scotopic

Scotopic

* Nighttime Vision
* Experience the worst contrast sensitivity
* Rods are sensitive to these light conditions

Phase

* Position of a grating relative to a receptive field
* Even if gratings align with receptive fields, the positioning may produce different responses, this changing how we interpret the gratings.

Lateral Geniculate Nucleus (LGN)

* Part of the thalamus, a structure that visual information hits on the way to the striate cortex
* Axons of ganglion cells synapse here

Parvocellular Layer

* Midget System
* Details in static objects
* Where P Ganglion Cells Synapse

Magnocellular Layer

* Parasol System
* Fast, large moving objects
* Where M ganglion cells synapse

Topographical Mapping

Neural basis for knowing where things are located in space (i.e. specific neural architecture for distinct location in our visual field)

Striate Cortex (V1)

* Where major transformation of visual information takes place
* Takes input outputs from ganglion cells in LGN and builds them in many different ways, enabling more complex processing

Cortical Magnification

* The amount of cortical area in V1 devoted to a specific region in the visual field
* Fovea has 15 times more respective neurons processing information than the periphery

Visual Crowding

* Deleterious effect of clutter on peripheral object detection
* An object is alone in our periphery, we can dedicate more neurons to discerning it
* When its surrounded by clutter, our neurons are spread thin, making it much harder to discern

Tendency of neurons in striate cortex to respond optimally to certain orientation and less to others

Orientation Tuning

Ocular Dominance

* The property of the receptive fields of striate cortex neurons by which they demonstrate a preference, responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other
* Key takeaway is that cortical cells can respond to input from both eyes while LGN cells only respond to input from one eye.

Simple Cells

Type of neuron which fires most rapidly when a line is presented at a specific angle in a specific part of the visual field

Complex Cells

Type of neuron that responds to lines of a specific orientation regardless of their position in the receptive field

End Stopping

Increased firing rate as bar length increases, but once longer than receptive field, firing rate decreases

Column

* A vertical arrangement of neurons
* Systematic, progressive change in preferred orientation

Hypercolumn

* 1x1mm block of striate cortex
* Many columns with preference for range or orientations

Method of Adaption

Measuring the diminishing response of a sense organ to a sustained stimulus

Selective Adaptation

* The effect that occurs when V1 neurons that fire in response to a specific orientation begin to tire out
* When this happens, cells that respond to other similar orientations begin to take over
* Evidence that human visual system contains neurons selective for spatial frequency

Tilt Aftereffect

Perceptual illusion of tilt, provided by adapting to a pattern of a given orientation

Strabismus

Misalignment of eyes such that single object in space is imaged on fovea of one eye and non-foveal area of the other (turned) eye

Anisometropia

The two eyes have different refractive errors

Amblyopia

A developmental disorder characterized by reduced spatial vision in an otherwise healthy eye

Middle Vision

* A loosely defined stage of visual processing that comes after basic features have been extracted from the image and before object recognition and scene understanding
* Involves the perception of edges and surfaces
* Where we start to build features of objects rather than features of visual stimulation
* Determining which edges/lines go together in an object-based sense