Sensory and Perceptual Processing

EYE

Cornea is the only part that is in the outer layer.

Cornea: Refracts the light and protects from accidents.

Iris: Controls amount of wanted light to enter through pupil.

Convex Lens: Focuses all light at one point in the eye called the Retina.

Retina: Back of the eye which contains nerve cells.

  • Cones Sensitive to Bright Light
  • Rods Are sensitive to dim light.

Photoreceptors: Cones and Rods.

Messages from the Retina are transferred on the optic nerve.

Retina Explained

%%When light reaches back of the eye the nerve cells are triggered.%%

Rods: Allow to see in dim light.

Cons: Allow us to perceive color.

The Fovea has no rods.

%%Light hits the photoreceptors (rods and cones) and interacts with a molecule called photopigment.%%

Photopigment: Light hits this and begins a chain of events that propagates visual signals.

  • Transmitted to Bipolar Cells.   * Bipolar Cells are connected to rod and cone detectors.   * Ganglion Cell Fibers are optic Nerves.

Optic Nerve

Optic Disc has no photoreceptors.

  • Can’t process visual information.

TheGanglioncellfibersmakeuptheopticnerve.The Ganglion cell fibers make up the optic nerve.

TheopticnervecarriesVISUALINFORMATIONtothebraintobeprocessed.The optic nerve carries VISUAL INFORMATION to the brain to be processed.

Horizontal Cells: Receive stimuli from multiple photoreceptor cells and adjusts signals that will be sent to bipolar cells.

Amacrine Cells: Receives signals from bipolar cells and is responsible for regulation/integration of activity in bipolar and ganglion cells.

Perceive Color

Color is not simply light hitting the eye.

Color Contrast: When painting a mark, the color will change when painted around.

Lightisawave.Differentcolorshavedifferentwaves.Consideringlightisawave,colorsshouldnotcombine,buttheyco−existinharmony.Light is a wave. Different colors have different waves. Considering light is a wave, colors should not combine, but they co-exist in harmony.

Rodsarejustresponsibleforlowlightsight.Rods are just responsible for low light sight.

Therearethreetypesofcones…red,green,andblue.There are three types of cones… red, green, and blue.

When a color is processed, each cone sends a direct signal to the brain. Rod cells only send light or no light signals in the dark.

Class Notes on Eye’s

Short Waves are blue in color and high in pitch.

Long Waves are red in color and low in pitch.

Great amplitude waves are bright in color and loud sounding.

Small amplitude waves are dull in color and soft sounding.

Recap of Pupil to Occipital Lobe

{{Pupil is a hole in your eye. When open wide more light comes in. Retina has rods and cones. It sends messages through optic nerve to occipital lobe.{{

  • {{The Cones send color to a single bipolar cell.{{
  • {{The rods detect peripheral vision.{{

Theories

Trichromatic Stage: Trichromatic cone cells respond positively to one of the frequencies exhibit by photons arriving on their surface.

^^Opponent Process Stage is when three color channels are discovered by opponent cells.^^

Opponent cells tuned to luminosity are excited by the ==red==, %%green%%, and ^^blue^^ color signals.

Cg cells are excited by red and blue and inhibited by green. Cb cells are excited by red and green and inhibited by blue.

Hubel and Wiesel

  • Showed Brain’s Computing system deconstructs and then reassembles visual images.
  • Specialized occipital lobe neuron cells.

Ganglion → Neuron → Supercell Clusters

Feature Detection: Brain’s detector cells respond to specific features like edges and angles.

Parallel Processing: Brain cell teams process combined information about color, movement, form, and depth.

Opponent Processing Theory: Looking at one color for too long causes receptor cells to become weaker and send weaker signals.