Oct21

bundle of axons

The ________ that form the optic nerve creates a blind spot where it exits the eye because there are no photorecepors ther.

Humans

________ can percieve a small part of the lectromagnetic (EM) energy spectrum from 400 nm to 700 nm.

high illumination

Cones: photoreceptor, contributes to perception of colour and detail, functions best in ________, fovea contains only cines, less numberous than rods.

human visual system

The ________ is adapted for both low and high light conditions.

Signal detection theory

________: addresses the question of what factors influence sensory judgments.

Standard SDT experiment

________: series of trials asking is stimulus is present, varying presence /intensity.

Pupil

________: adjustable opening behind cornea that controls amount of light entering the eye, the ________ dilates /constricts to allow more /less light into the eye depending on lighting conditions in the environment.

Lens

________: elastic structure that changes form to help focus, becomes thinner to focus on more distant objects and thicker to focus on nearby objects.

Hyperopia

________: farsightedness, difficulty seeing close up objects, light focused too far behind retina.

Cameras

________ work very similarily to the eye and can be a useful point of comparison (particularily if you already know the parts of a(n) ________)

Psychophysics

________ refers to study of the relationship between the physical characteristics of stimuli and sensory experience.

Retina

________: multi layered structure at the back of the eyes that contains light- sensitive photoreceptors which transduce light energy into electrical impulses.

Stimulus

________ for vision is electromagnetic energy, or light waves (measured in nanometers or billionths of a meter)

Sensory neurons

________ in all modalities respond to constant level of stimulation by decreasing their activity This is adaptive and frees senses to be more sensitive to changes in environment.

Rods

________: a photoreceptor, contributes to black /white vision, functions best in low illumination, 500 times more sensitive to light than cones, found throughout the eye but not in the fovea, increasing in concentration towards periphery of retina.

Cornea

________: transparent protective structure at front of eye.

Decision criteria

________: refers to the standard of how certain we must be before deciding whether or not we believe a stimulus is present.

Myopia

________: nearsightedness, difficulty seeing far away objects, light focused too far in front of retina.

Sensory adaptation

________ refers to this diminishing sensitivity to an unchanging stimulus (sometimes also refered to as habituation)

Absolute threshold

Intensity at which stimulus can be detected 50% of the time

Threshold and sensitivity have an inverse relationship

the lower the threshold the higher the sensitivity

Signal detection theory

addresses the question of what factors influence sensory judgments

Decision criteria

refers to the standard of how certain we must be before deciding whether or not we believe a stimulus is present

Standard SDT experiment

series of trials asking is stimulus is present, varying presence/intensity

4 possible outcomes

hit, miss, false alarm, correct rejection

Present and perceived

hit

Present and not perceived

miss

Absent and perceived

false alarm

Absent and not perceived

correct rejection

Difference threshold

can be called just noticeable difference or JND, the smallest difference between two stimuli that can be detected 50% of the time

Weber's law

difference threshold is directly proportional to the magnitude of the stimulus with which the comparison is being made, which can be expressed as a Weber fraction

Weber fraction

can differ depending on the modality, eg this fraction for weight is about 1/50

Light

the stimulus for vision

Lens

elastic structure that changes form to help focus, becomes thinner to focus on more distant objects and thicker to focus on nearby objects

Retina

multi layered structure at the back of the eyes that contains light-sensitive photoreceptors which transduce light energy into electrical impulses

Cornea

transparent protective structure at front of eye

Pupil

adjustable opening behind cornea that controls amount of light entering the eye, the pupil dilates/constricts to allow more/less light into the eye depending on lighting conditions in the environment

Myopia

nearsightedness, difficulty seeing far away objects, light focused too far in front of retina

Hyperopia

farsightedness, difficulty seeing close up objects, light focused too far behind retina

Rods

a photoreceptor, contributes to black/white vision, functions best in low illumination, 500 times more sensitive to light than cones, found throughout the eye but not in the fovea, increasing in concentration towards periphery of retina

Fovea

center of retina

Cones

photoreceptor, contributes to perception of colour and detail, functions best in high illumination, fovea contains only cines, less numberous than rods

Bipolar cells

recieve signal from the rods and cones, more rods are typically connected to a given bipolar cells as compared to cone which contributes to their greater sensitivity to light on account of being able to funnel more info/signal through

Ganglion cell

synapse with the bipolar cells, 1 million in total, the axons of these cells form a bundle called theoptice nerve