sens4

the initial process of detecting and encoding environmental energy

the process of organzing and iterpreting sensations into meaningful experiences

smallest amount of stimulus energy necessary for an observer to reliably detect a stimulus

the quality of the sensation elicited by a stimulus depends primarily on the nerve stimulated and only secondarily on the stimulus itself

the region on the receptor surface that, when stimulated, influences the firing rate of the cell

refers to increased intensity difference observed on either side of a dark-light broder

deficit in which the subjects visual accuity is normal but their shape perception is distorted

deficit in which subject has no distortion in shape percetption but still cannot recognize objects

properties of a 2D image that, in general, do not change as a viewer's perspective of an object changes

inability to recognize faces

refers to the fact that any 2D image can be created by an infinite number of 3D environments

as one moves through the environment, nearer stationary objects appear to move faster than further stationary objects

imaginary arc passing through point of fixation; objects on horopter fall on corresponding points on the two retinas

the retinal image on the two eyes is slightly different and this difference provides an absolute depth cue

two lights blinking on and off will, at the proper frequency, appear to be one light that is moving

a period of neural plasiticity when certain environmental stimuli must be present for normal brain development to occur

pressure changes in a medium that can be detected by auditory organs

the set of all points that could produce a particular time and intensity difference between the two ears

if someone says Ba, but they're moth movements are those of Ga, then Da is perceived

auditory system fills in phonemes that are obscured by noise

the shortest segment of speech that, if changed, would change the meaning of a word

after being rotated, people experience paradoxical motion, in which the world seems to be spinning but visually remains in the same place

a reflexive eye movement that begins when the vestibular organs signal rotation about the body axis

skin temperature at which no thermal sesations are elicited

naturally occuring opiate-like chemcials that suppress pain

sensory system that responds to chemical irritants

inability to detect certain smells

chemicals released by one animal that cause behavioral reactions in other animals of the species

women who live together eventually have menstrual periods that all begin at approximately the same time

a number of stimulus intensities are selected beforehand by researcher. the stimuli are presented numerous times in random order and subject reports whether each stimulus is detected. a graph is plotted showing percentage detected as a function of stimulus intensity. the point at which stimulus was detected 50% of the time is absolute threshold.

researcher starts with stimulus clearly above threshold and asks subject if they can detect it. researcher adjusts stimulus intensity down in fixed increment until subject cannot detect it. process repeated several times, sometimes ascending, sometimes descending. crossover point is deemed absolute threshold.

the intensity of stimulus is adjusted by observer until they can just barely detect it

• Observers' criteria for responding greatly affect the results
• The observer could be lying

• Soma: contains nucleus of cell and provides for the life processes
• Axon: transmits information from cell body to terminal buttons
• Dendrites: receive messages from other neurons
• Terminal Buttons: pass information to next neuron in the chain

showed that perceived magnitude is due to firing rate of sensory neurons

primary refractive surface of the eye

can change size of pupil to control amount of light entering eye

allows adjustments in focus of eye

• Lens System: focuses many light rays on a single point
• Advantage: image is very bright
• Disadvantage: can be out of focus
• Pinhole Camera: uses very small hole to allow very small number of light rays from each point in the visual field to enter
• Advantage: never out of focus
• Disadvantage: image is very dim

• Rods:
• Sensitive to Light
• Larger
• Many Rods
• Many connect to each bipolar cell
• Pigment is relatively insensitive to wavelength
• Found only in the periphery
• Pigment regenerates in 30 min.
• Cones:
• Less sensitive
• Smaller
• Fewer
• Few connect to each bipolar cell
• Have differential sensitivities to wavelength
• Concentrated in Fovea
• Pigment regenerates in 6 min.

• P Cells: color and form perception
• M Cells: motion perception, depth perception, simple detection of light
• K Cells: code overall level of illumination

• Simple Cells: bars in a particular location of a particular orientation
• Complex Cells: bars in a particular location of a particular orientation that are moving in a particular direcction
• End-Stopped Cells: bars in a particular location of a particular orientation and particular length

there are three different types of color receptor, each responding maximally to a different wavelength, but having some response to every wavelength

there are three different types of color receptor that respond to pairs of colors (red-green, blue-yellow, black-white). each receptor is excited by one of the pair and inhibited by the other

the cones respond as the Young-Helmholtz theory predicts while ganglion cells respond as the Herring Opponent Process theory predicts

• Dichromatism: need only two colors to match the pure wavelength light, but their match would not look correct to normals
• Anomalous Trichromatism: need three colors to match the pure wavelength light, but their match would not look correct to normals

enhances edges

• Procedure: researchers ablated cells of interior temporal lobe in one group of monkeys and the posterior parietal lobe in another group of monkeys. monkeys were then trained to do an object recognition task, as well as an object location task
• Results: monkeys with IT ablated cells could not perform the object recognition task, but could perform the object location task. monkeys with PP ablated cells showed reciprocal results.
• Significance: the IT (ventral) pathway codes identity of an object. The PP (dorsal) pathway codes location of an object

• 1. Edges are extracted from an image.
• 2. Image edges are parsed into parts and non-accidental properties are determined.
• 3. The identity of the geons is determined.
• 4. The relations among the geons are determined.
• 5. The best match in memory is found.

• Occulomotor
• Pictorial
• Motion Produced
• Binocular Disparity

• Inwardly Displaced: object is closer than the horopter
• Outwardly Displace: object is further than the horopter
• Corresponding: object is on the horopter

• Infantile Strabismus: the eyes did not have coordinated movement during infancy and thus disperity-tuned cells never developed
• Genetic Disorder

• People who are stereoblind often don't realize it
• Stereo vision is not useful at long distances
• Stereo vision does not aid in identifying an object

objects appear smaller when the head is tilted up than when held parallel to the ground

earth's terrain causes the moon to appear further away and thus bigger at the horizon

• Phi Effect: cells some distance apart on the retina can be wired to excite another cell (indicating motion in a particular direction) when they are stimulated with a particular delay between them. the Phi Effect simulates this pattern of stimulation
• Autokinetic Effect: to compensate for muscular fatigue, the eyes require abnormally strong signals from the brain. these abnormal signals are the same as would be required to track a moving object so the brain assumes the light is moving

blur by the optic media, lateral inhibition in the retina and processing strategies all affect this illusion

a large number of small Poggendorf Illusions

linear perspective and texture gradients make the top bar appear further away and thus bigger than the bottom bar

the image on the retina is consistent with both a trapezoidal window rotating completely and a rectangular window switching directions every 180. since we are used to seeing rectangular windows, our visual system prefers this interpretation

• Myopia: eyeball is too short
• Hypermetropia: eyeball is too long
• Astigmatism: lack of spherical cornea
• Presbyopia: weakening of ciliary muscles and hardening of the lens

• Numerator: distance, in feet, at which the test was administered
• Denomenator: distance, in feet, at which the critical feature of the test symbol covers one minute of visual angle

• Cause:
• 1. congenital and inherited at birth
• 2. acquired by injury or disease
• 3. old age
• Treatment: artificial lens implants or removing the lens and using spectacles to correct vision

• Cause: photoreceptors become detatched from the pigment epitheliam
• Treatment: cryotherapy-eye is purposefully injured to create scar tissue that locks retina into place

• Cause: problems draining the aqueous humor cause an increase in intraocular pressure. the increased pressure compresses the blood vessels serving the optic nerve and the optic nerve fibers die
• Treatment: drugs are available that decrease the production of aqueous humor or remove blockage

• Frequency: Hertz (Hz)
• Amplitude: Decibels (dB)

• Frequency: pitch
• Amplitude: loudness

• Pinna
• Meatus
• Tympanic Membrane

• Amplify vibrations from the tympanic membrane
• Protect the ear from loud sounds

different places on the basilar membrane vibrate in response to different frequencies. the hair cells being stimulated by the region with the greatest amount of vibration indicate the frequency that is present

the basilar membrane vibrates at the same frequency as the stimulus. every time the basilar membrane vibrates, it causes an action potential in the Auditory Nerve. Thus, the rate at which the auditory nerve fires codes the frequency of the stimulus

below 1000 Hz, firing rate determines pitch (Rutherford). above 5000 Hz, place of greatest basilar membrane stimulation determines pitch (von Bekesy). between 1000 and 5000 Hz, both mechanisms operate

• 1 to 15 Hz: a tone midway in frequency between the two tones is perceived that ossilates in loudness at the same frequency as the difference between the two tones
• 15 Hz: a tone midway in frequency between the tones is perceived that sounds rough
• Critical Bandwidth: two separate tones are perceived

• Intensity
• Doppler Shift

• Interocular Intensity Difference
• Interocular Time Difference

high frequency sounds

by moving our head

• 1. Speech is perceived more categorically than other sounds
• 2. Visual stimulation effects speech perception
• 3. Top-Down information affects speech perception

In speech recogntion, a few phonetic features (non-accidental properties in object recognition) combine to create phonemes (geons). Then phonemes, in their proper relations, are used to recognize words (objects).

register the direction and extent of rotary acceleration

dissociation between visual and vestibular information

prevents food poisoning, which causes dissociatin between vestibular system and vision

• 1. Sensitive areas have a higher density of pressure sensitive neurons
• 2. Receptors in more sensitive areas have smaller receptive fields than those in less sensitive areas
• 3. Sensitive areas receive relatively more area in the somatosensory cortex

• severe childhood injuries
• massive injuries to their joints

• S fibers: sustained (aching) pain
• L fibers: sharp pain and pressure

stimulate L fibers

61-108 F (in water)

a very warm stimulus can elicit a cold sensation when applied to an area of the skin that has no warm receptors

Oral cavity, nasal cavity, and cornea

no adequate system of describing smells

olfactory receptors respond to molecules of a particular shape and size

• 1. Each olfactory cell responds to chemicals of a variety of shapes and sizes
• 2. the relationship between molecule shape and odor is not as strong as the theory predicts

different chemicals spread accross the mucosa in different ways. the regions of the mucosa the chemical is activating can therefore be used as a code for odor quality.

smells appear to be difficult to learn but easy to remember

• Sweet: complex organic molecules, sweet foods provide energy
• Salt: simple inorganic molecules that are not acids or bases, detects sodium
• Sour: substances containing acids, bacterial decomposition
• Bitter: alkaloid substances, poison detector

tongue, inner cheeks, throat and palate

respond somewhat to all 4 primary tastes, but respond with preferential vigor to one

• MSG: increases sensitivity to both salt and sweet
• Sodium Lauryl Sulfate: decrease sweet sensitivity, increase bitter sensitivity

smell deteriorates before taste; sensitivity to salt and sweet decrease more than sensitivity to sour and bitter. foods with a pleasant smell, but bitter taste are less enjoyable

70-75F