Psychology Brain And Mind Week 5 - Hearing And Seeing

Autonomy Of Auditory System

• Outside of the ear: Pinna

• Auditory caal

• Tympanic membrane (eardrum)

• Middle ear contains three tiny bones: Malleus, Incus and Stapes

• Inner ear contains semi-circular canals involved in balance and movement

• Cochlea: Fluid filled, snail-shaped structure that contains sensory receptor cells of auditory system

How Sound Waves Move Through Ear

1. Sound waves travel along auditory canal

2. strike tympanic membrane

3. causes vibration

4. vibration moves three osccicles

5. stapes presses into thin membrane of cochlea down as oval windows

6. fluid inside cochlea moves

7. stimulates hair cells in ears → mechanical process

Eardrum Efficiency

Sends message to the eardrum, making the eardrum vibrate

• Little bones vibrate, pushing on the oval window

• Fluid in the inner ear is moved by the little bones vibration

• Ossicles provide amplification and push sound wave into inner ear

Inner Ear: Converting mechanical Signal To Electrochemical Signal

As the hairs move back and firth, it creates an action potential that can move backwards into the brain

• moves to the auditory cortex

What Activation of hair Cells In Ear Does

Generates neural impulses that travels along auditory nerve to brain, shuttled to the inferior colliculus, medial geniculate nucleus of the thalamus, and then finally to the auditory cortex

Pitch Perception Theories

• Temporal Theory

• Place Theory

Temporal Theory

Asserts that frequency is coded by activity level of sensory neuron

• Given hair cell would fire action potentials related to frequency of sound wave

Place Theory

Suggests different portions of basilar membrane are sensitive to sounds of different frequencies

• BAse responds to high frequencies and tip responds to low frequencies

• base proprition = high-pitch receptors, top proportion = low=pitch receptors

Sound Localization

Ability to locate sounds in our environments is an important part of hearing

• Monarual cues

• Binaural cues

• Interaural level difference

• Interarual timing difference

Monaural (One-Eared) Cues

Provide information on whether information is above or below, in front or behind

Binaural (Two Eared) Cues

Provide information of location of a sound along horizontal axis by relying on differences in patterns on vibration

Interaural Level Difference

Sound coming from the right side of your body is more intense in your right eat than your left

• Due to attenuation of the sound as it passes through your head

Interaural Timing DIfference

Small difference in the time at which a given sound wave arrives at each ear

Hearing Loss Examples

• Deafness: Partial or complete inability to hear. Being born with i is congential deafmess

• Conductive hearing loss: Probelm delivering sound energy to cochlea

• Sensorineural hearing loss: Caused brom aging, head/acoustic trauma, infections and diseases

Cochlear Implant

Electronic devices that consist of a microphone, speech processor and an electrode array

• Device receives sound information and directly stimulates auditory nerve to transmit information to the brain

Sound

Motion of air molecules

• Measured by Hertz and amplitude

Pure Tone

Tone with a single frequency of vibration

Frequency

Number of cycles per second of an auditory stimulus

• high frequency are higher in pitch, whereas low frequency are lower in pitch

Cornea

Transparent covering over the eye

• Serves as barrier between inner eye and outside world

Pupil

Small opening in the eye through which light passes, and the size of the puil changes as a function of light levels as well as emotional arousal

• When light levels are high, pupils dialate

• When dark, pupils expand and allow more light into eye

Lens

Curved, transparent structure tjat serves to provide additional focus

• Can change shape to aid in focussing light that is reflected

• Focus images on small indentation at the back of the eye known as fovea, a part of the retina

Fovea

Contains photoreceptors (Cones) that are light detecting cells

• Special types of photoreceptors that work best in bright conditions

• Cones concentrated here

Rods

Photoreceptors that work well in low light conditions, involved in vision in dimly lit environments as well as in our perception of movement in the periphery visual field

Retinal Ganglion Cells

Have rods and cones connected to them

• Azons from these cells converge and exit throughout the back of the eye to form opic nerve

Optic nerve

Carries visual information from the retina to the brain, with their being a point in the visiual field called the blind spot

Merges to brain at point called optic chiasm

Colour Vision

Having three cones that mediate colour vision

• Trichromatic theory of color vision suggests all colours in the spectrum can be produced by mixing red, green and blue

Opponent-Process Theory

Colours are coded in opponent pairs - yellow/blue, green/red

• Some cells of visual system are excited by other opponent colour and prohibited by others

• Wavelengths associated with green would be inhibited by wave lengths associated with red

Three Types Of Cones

L Cones: Sensitive to long-wavelength light

• Red, organe and tellow. Little sensitivity to violet

M Cones: Sensitive to medium-wavelength light

• Most sensitive to greenlight

S Cones: Sensitive to short-wavelength light

• Most sensitive to blue cones

Depth Perception

Percieve spatial relationships in three-dimensional space. Uses:

• Bionulcate clues (both eyes)

• Binocular disparity: slgith difference of world that each eye recieves

2D Stimulus And Monocular Cues

• Linear Perspective: We receive depth when we see two parallel lines that seem to converge in an image

• Interposition, partial overlap of objects, relative size, closeness of images to horizon

Hue

Light emitted by sun has broad spectrum

• Objects either reflect, absorb or refract this light

• surface colour related to wavelengths is reflected

• Colours absorbed aren’t seen, whereas colours reflected are observed

Visual Processing Step One

Retina: Photoreceptors detect light (rods and cones). control activity of bipolar cells which connect to ganglion cells

• Ganglion cells form optic tract

Scoptic and Photopic Vision

• Scotopic system: low light conditions, rods only

• Photopic System: Higher light conditions, several different types of cone cells respond to different wave lengths - colour vision

Optic Disc

Where ganglion cells and blood vessel exit the eye

• No photo receptors on disc means there is a blind spot

Transmission From Eye To brain

• Ganglion cells sensw signals along axons via optic nerve

• At optic chiasm, hald axons cross to other hemisphere

• LEft infor goes to right and vice versa

• Visual areas of thalamus

• Primary visual cortex located in the occipital lobes

What And Where Pathways

Ventral Stream (What)

• Perception for recognition of objects. Vision for perception

Dorsal Stream (Where)

• Determining where an object is. Vision for action