sens1

the initial process of detecting and encoding environmental energy

the process of organizing and interpreting sensations into meaningful experiences

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

condition in which stimulation of one sense evokes an involuntary experience in another sense

the study of the relationship between the physical properties of a stimulus and the subject's experience of the stimulus

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

a measure of how sensitive a subject is to a stimulus in a Signal Detection Theory (SDT) experiment

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

• Emanation Theory
• an inner fire sends out rays through the eyes that bring back information about the world

• Eye works like pinhole camera
• Eye pupil is much too large to work this way
• Alhazen thought he was wrong because pinhole camera image is upside down but this refutation of his own theory is also wrong; our eye does create an upside down image on our retina

• demonstrated that eye uses lenses to create an image
• cut back off of cat's eye and used it as projector

• developed Doctrine of Specific Nerve Energies
• suggested, incorrectly, that mechanical stimulation of the optic nerve is what produces image (it is actually chemical reaction)

• Founder of psychophysics
• First to study the Difference Threshold

• developed 3 methods for determining Absolute Threshold
• Magnitude Scaling - determining relationship between perceived magnitude and stimulus intensity

Developed most accurate law of magnitude scaling

• /\I / I = k
• I = magnitude of original stimulus
• /\I = increment in intensity that can just be discriminated from I
• k = constant depending on the sense being measured

• p = k[log(I)]
• p = perceived magnitude
• k = constant depending on sense being measured
• I = stimulus intensity

• p=kI^b
• p = perceived magnitude
• k = constant depending on sense being measured
• b = constant depending on sense being measured
• I = stimulus intensity

• Method of Constant Stimuli - number of stimulus intensities selected beforehand, stimuli presented numerous times in random order and subject reports whether each stimulus is detected, graph plotted showing detection and intensity, point at which stimulus detected 50% of time is absolute threshold
• Method of Limits - researcher starts with stimulus clearly above threshold, adjusts stimulus intensity down in fixed increment until subject cannot detect, repeated several times sometimes ascending sometimes descending, average of crossover points is absolute threshold
• Method of Adjustment - intensity of stimulus is adjusted by observer until they can barely detect it

• Observer's criteria for responding greatly affects results
• Observer could be lying

• Weber's law is correct
• All JND's are subjectively equal

• Subjects presented with stimulus and given arbitrary number distinguishing its intensity (shown light with brightness of "10")
• Stimuli of various intensities presented to subject and subject assigns number to each, relative to standard (shown brighter light and responds with "30")
• Reported number is perceived intensity; actual measure (wattage, pounds, etc.) is stimulus intensity

• b<1 - doubling of stimulus intensity leads to less than doubling of perceived magnitude
• b=1 - doubling of stimulus intensity leads to doubling of perceived magnitude
• b>1 - doubling of stimulus intensity leads to more than doubling of perceived magnitude

It eliminates the possibility for subjects to be lying and measures a subject's sensitivity independent of their response bias.

• On each trial, subject is presented with either very faint stimulus or no stimulus.
• Subject reports whether or not the stimulus was present.
• Sequence is repeated many times.

• Subject's response - stimulus present
• Actual state - stimulus present

• Subject's response - stimulus absent
• Actual state - stimulus present

• Subject's response - stimulus present
• Actual state - stimulus absent

• Subject's response - stimulus absent
• Actual state - stimulus absent

• Dendrites - receive information from presynaptic neuron
• Soma - cell body
• Axon - site of action potential, transports electrical impulse to terminal buttons
• Terminal buttons - send information to postsynaptic neuron

-70

the brief period in which a neuron cannot fire again after generating an action potential

the brief period in which a neuron is less likely to fire again after generating an action potential

Their rate of fire

Showed that perceived magnitude is due to firing rate of sensory neurons.

• Enhanced depth perception
• Increased peripheral vision
• Enhanced vision in dark or dim light
• One eye covers the other's blind spot
• Spare

Keep sweat out of our eyes

primary refractive surface of the eye

• Controls amount of light entering eye
• Absorbs light

allows adjustments in focus of eyes

• Bends light rays to focus many on single spot on retina
• Advantage - creates bright image
• Disadvantage - can be out of focus

• uses very small hole to let in one light particle for each spot in space
• Advantage - no focusing problems
• Disadvantage - image is very dim

• eye is too long
• creates near-sightedness

• eye is too short
• creates far-sightedness

• Contain light-sensitive chemicals called photopigments
• Hyperpolarize in response to light (resting potential is -30 and this decreases when exposed to light)
• Do not have action potentials
• Synapse with bipolar cells
• At BACK of retina

• Rods are more sensitive to light than cones
• Rod are larger than cones
• There are many more rods than cones (120M/6M)
• Rods' pigment is not as sensitive to wavelenght as cones (this is why cones detect color)
• Rods are found only in the periphery, but Cones are concentrated in Fovea
• Rods' pigment reginerates in 30 min, Cones' pigment reginerates in 6 min.

carry output of photoreceptors to ganglion cells

• Modulate connection between photoreceptors and bipolar cells
• Allow photoreceptors to communicate with eachother

Modulate connection between bipolar cells and ganglion cells

generate the action potentials that are carried to the brain

Edge enhancement

• P cells (parvo) - color and form perception, center-surround
• M cells (magno) - motion perception, depth perception, simple detection of light, center-surround
• K cells (dust) - code overall level of illumination, no center-surround