Foundations of Perception

Foundations of Perception

• Humans can only detect a small amount of information from the world through senses.
• Sensory education begins in the womb, influencing a baby's preferences.
• Experiences shape how we interpret new information.
• Sensations are features of the environment used to understand the world, such as light wavelengths or air pressure changes.
• Sensations are translated into brain language by the sensory system.
• The brain combines sensory messages with past experiences to create perception.
• The perceptual world combines bottom-up and top-down processes.
• Bottom-up processing starts with physical messages or sensations.
• Top-down processing combines incoming messages with existing knowledge for interpretation.
• Different experiences lead to different perceptions.
• The Masuba and Nisbett study (2001) revealed differences in visual perception between Americans and Japanese. Americans focused on fish first, while Japanese described the animate objects.

Gestalt Principles

• Gestalt psychologists believed perception is more than just assembling messages.
• Individuals are predisposed to organize information in specific ways.
• The figure-ground principle organizes information by prioritizing certain elements over the background.
• Gestalt principles of organization outline how the world is seen.
• Proximity: objects close together are grouped together.
• Similarity: objects that look alike are grouped together.
• Closure: people perceive whole objects even with missing parts.
• Good continuation: lines are seen as continuous even when interrupted.
• Common fate: objects moving together are grouped together.

Vision - From Light to Sight

• 20% of the cortex interprets visual information.
• Light is a form of electromagnetic radiation.
• The eye adjusts to maximize light quality reaching sensory cells in the retina.
• The cornea is the eye's outermost, transparent, protective layer and assists with focus.
• The pupil, a hole that expands and contracts, allows refracted light to enter.
• Pupil size is controlled by muscles attached to the iris.
• The iris gives eyes their color but has no role in vision.
• The lens, behind the pupil, helps focus light on sensory cells in the retina and its flexibility is layered
• Accommodation, the process in which the distance between the lens and object determines thickness and roundnesss
  • closer objects = thicker,rounder lens
  • farther objects = relaxed,elongates lens.relaxes and elongates

Myopia and Hyperopia

• Myopia (nearsightedness): lens focuses object before it reaches retina, by the time reaches photoreceptors image is blurry.
• Hyperopia (farsightedness): when the image arrives at the retina, its not yet focused close objects = blurry

Photoreceptors and Visual Acuity

• Photoreceptors transduce light into cellular activity but arrives after 5 layers of cells in the retina .
• Rods and cones transduce energy into neural language.
• The fovea, in the center of the retina, has a dense cluster of cones for high-light response.
• Visual acuity results from only a few cells connecting to adjacent ganglion cells, transmitting fine detail.
• there are 120 million rods act as the primary cell in the periphery of the retina, more sensitive at lower levels of light for night vision .

Dark Adaptation

• Dark adaptation occurs as rods and cones adjust to light changes in two stages.
• Cones rapidly respond to light changes, but their sensitivity plateaus after 8 minutes.
• Rods continue increasing sensitivity for an additional 20 minutes.
• Cones communicate information about wavelength (color), while rods respond to the amount of light, without communicating quality.

Image Reception and Processing

• Refraction inverts the light which causes inverted images .
• Middle of the image is focused (cones), and the outside is blurred (rods).
• Rods don't process wavelength, so the outside is black and white.
• After reacting to light, rods and cones send messages to bipolar cells.
• Bipolar cells combine photoreceptor firings and send different messages to ganglion cells.
• Diffuse bipolar cells receive messages from as many as 50 rods in peripheral vision.
• Midget bipolar cells receive input from only 1 cone.
• Small ganglion cells (P-cells) receive information from midget bipolar cells and send signals about color and detail (70% of ganglion cells in retina).
• Large ganglion cells (M-cells) are found in the periphery and send signals about motion and visual stimuli.
• 70% of the message is created by cones, and 30% by rods.
• Ganglion cells have receptive fields that respond to light in specific portions of the eye.
• The receptive field is center-surround, with cells responding more quickly to light in the center.
• The message leaves the eye via the optic nerves (axons of M- and P-cells).
• The blind spot is where there are no photoreceptors, and the brain fills in the blank.

Visual Cortex and Color Vision

• The optic nerve message travels to the optic chiasm, reorganizing axons from both eyes.
• Information from the right side goes to the left hemisphere.
• Information from the left side goes to the right hemisphere.
• The first interaction with the image occurs in the lateral geniculate nucleus (LGN) of the thalamus.
• The LGN is organized into 6 sublayers, each with specific information types, corresponding to M- and P-cells.
• Information is combined and consolidated before reaching the visual striate cortex in the occipital lobe.
• The visual striate cortex assembles and identifies important visual features.
• Over 30 areas in the back of the brain analyze and organize visual information.
• Retinotopic organization maintains information origination in the retina throughout processing.
• Feature detectors are specialized cells in the visual cortex that respond to specific stimuli.
• Hubel and Wiesel (1962) discovered feature detectors by examining the cortex of cats and monkeys.
• Simple cells respond to stationary light bars at specific angles.
• Complex cells respond vigorously to vertical lines in motion.
• The cell decreases its firing rate as the line moves further from a vertical orientation.
• Information about what is being seen goes to the temporal lobe via the ventral stream (what stream).
• The dorsal stream (where pathway) carries information to the parietal lobe.
• Visual information also goes to the limbic system, helping provide feeling to what is being seen.
• Color perception originates in the cones and is processed at every step along the visual pathway.
• Color is the perception of wavelengths, where longer is red, medium is green, and shorter is blue.
• White equals equal representation of all wavelengths.
• Rainbows show light refracting through water in the air, creating color.
• Ancestors evolved to perceive light for useful information.
• Eyes have three cone types: short, medium, and long.

Trichromatic Theory and Color Blindness

• Trichromatic theory states that color info is identified by comparing the activation of the different cones.
• Color blindness occurs when someone is born without one type of cone.
• Deuteranopia stems from green cones containing red photopigment.
• Protanopia caused when the red cones have green photopigment.
• The level of activity in each cone results from the amount of photopigment in the cell.

Opponent Process of Color Vision and Depth

• The opponent process of color vision is that the cones send their message to the midget bipolar cells then to the P-cells.
• P-cells respond vigorously to one wavelength and reduce firing when receiving a signal indicating a different color.
• Colors are paired which if they are received and sent on either side causes reaction increase or decrease by one another
  • ex: red+green, blue+yellow, and black+white
• Image after effect: after focusing on one color, the cells signaling that color reduce firing, causing brain to detect reduced signal as opposite color when you look away.
• Perceiving depth combines both top-down processing to interpret retinal images about depth(or to the lack thereof)
• Human brains utilizes depth cues to infer information about the depth of a said image.

Types of Depth Cues

• Monocular depth cues: require only 1 eye

  • Aka pictorial cues.
  • Occlusion: When one image partially blocks the view of another, the hidden object appears further away.
  • Relative height: Objects closer to horizon appear farther away, relies on world knowledge and perception in distance.

• Binocular depth cues: require 2 eyes for comparisons to understand depth

  • Retinal disparity: Since eyes are locataed in different locations, each eye has slightly.diff images of the world.
  • Human brain makes comparisons to understand depth using binocular cues
  • Retinal disparity: eyes being in different locations leads to unique images of the world
  • Useful cues include: images that appear farther away have smaller degrees of disparity of the 2 retinas.
  • Turns eyes inward to focus on an object to process depth info.
  • Can also use the tension in the eye muscles to make determinations about depth.

Hearing Senses

• Hearing is one of the most important senses.
• Physical message of sound: energy travels that requires a medium to travel through such as air or water
• Frequency:is the vibrations rate , pitch also
  • Can hear between 20-20000Hz
  • Best hearing between = 1000-5000Hz
• 2D(or rather 2 dimension) of sound = waves intensity; loudness.
  • Increase in waves intensity= high amplitude = increased force.
  • Amplitudes measured using dB .
  • If amps are above 100dB structures are damaged in both middle/ inner ear .
  • the Ear = pressure sensor

When Sounds enter the Ear

• Sound filtrated by the pinna toward the tympanic membrane (eardrum)
• Eardrum is the energy transferred to and from; works like a drum to transfer its smallest bones the
• Ossicles: ossicles of/in the middle ear help vibrations get further into inner ear.
• Malleus, incus, stapes
• Sound waves now connected to small mb now go to Oval window
• Oval window: now bony sound processor= inner ear. =cochlea.
• Inside of the cochlea lies the Basilar mb
• Transduction happens with vibrations against the oval window and the liquid now causes the cochlea
• The liquid is causing the cilia to push against thing fibers The Auditory Nerve=Excitory message.
• Causes the mb to “ripple effect” and causes action from the ear to the brain. Loc of neural firing = sounds- We now hear sound from cell/ mb which now fire Hear specific pitch
• hair often don’t operate independently
• the Frequency theory states that it causes more info related to the cells to fire.= higher pitch/ faster firing

Auditory Cortex+ Sound localization

• The AC or Auditory complex : primarily temporal lobe.
• Components: organized then analyzed in the MGN or, Medial geniculate nucles . The network +MG has but the majority of components are relayed onto the auditory complex
• Similar to retro topic organization now Auditory system to tonal topic organization
• spatial organization or mb is maintained: auditory pathway Auditory system has the both what/ where in streams Timing is very Important to understand sound Simple sound processed: lower region Hard: human speech/ higher regions
• Sound localizing
• can be used as good the loc cue= cue that sound can be localized.
• binaural cues of sound
• the comparisons between sound incoming- 2 Types of sound
• inter inter time arrival differences now arrive at our ears from time difference.
• inter arrival =sound from ear Sounds louder=wave travel sound of head now reach inner ear with less intense sound because Sound closer: less intense
• Music/speech recognition+
• Has shows that have deeper effect of the body the most Oliver s& sticky: Can not have particular/ certain not song out of head.
• Involuntary musical imagery: defined as (the experience of head from prevent sound from repeating or “Earworm Speech, sound; Production: 3 components: parts Respotation, record.
• Correct Fluency required: lots of coordinating
• SPEECH HAPPENS RAPID INFLECTIONS/variation. Meaning

Smell and Taste Senses

• Smell
  • only does not go through the thalamus first
  • Old evolution plays to our behave / how we behave
• We as humans: poor at, need the the high conc of other scent. Smell
• Airborne interactions of mouth to nose draw to chamber Receptors bound to Smell= cilia on the olfactory/ odor/neurons
• Receptor messages: the ORN’s ( or nose sending messages to smell bud.
• Receptors=sensitive to smell +odor.
• ORN’s-sending signal: a mix of analyzing helps the odor