Sensation & PerceptionDr. Amal Gamal Shehata

Associate Professor

RAK College of Dental ScienceVI Semester BDS

2011

The Cognitive Approach emphasizes that people are shaped (& differ from each other) because their perceptions & their thought processes differ. So understanding some background information on how we perceive things in our environment may help assist us in our understanding of the Cognitive approach. That is why we are now turning our attention to the topic of “Sensation & Perception,” a specialty area within Psychology that works at understanding how our senses work & how we perceive stimuli in the environment.

Introduction

SensationThe processes by which our sense organs receive information from the environment. PerceptionThe cognitive /Mental processes by which people select, organize, and interpret sensations that has been transmitted to the brain.

Definition of terms

The process by which physical energy is converted into sensory neural impulses.

Communication between the brain & the rest of the body occurs via neuron. We recently

learned how communication between neurons occurs electrochemically .

Transduction :

Sensory SystemsVision

Hearing

Smell (olfaction)

Taste (gustatory)

Touch (pressure, pain, temperature)Other senses : Vestibular sense (balance)

Kinetic sense (body movement)

How sensation and perception work together?

Sensation occurs:• Sensory organs absorb energy from a

physical stimulus in the environment.• Sensory receptors convert this energy

into neural impulses and send them to the brain.

Perception follows:• The brain organizes the information

and translates it into something meaningful.

Sensation & Perception Processes

V I S I O N

Structures of the Human Eye

Vision Visual Pathways

Optic Nerve“Visual Pathway” that carries visual information from the eyeball to the brain.

• When we see an object light reflected from the object passes through the pupil, an adjustable opening in the eye through which light enters.

• The iris is the colored structure on the surface of the eye, surrounding the pupil. When the light is dim, muscles widen the pupil to let in more light, and when the light is bright, the muscles narrow the pupil.

•  After light passes through the pupil, it strikes the retina at the back surface of the eyeball. As light passes through the eye, the cornea and the lens focus the light on the retina .

The Visual Receptors cell • The visual receptors of the eye, specialized neurons

in the retina at the back of the eyeball, are so sensitive to light .

There are 2 types of visual receptors:

Rods and Cones• Cones are receptors adapted for colors vision,

daytime vision and detailed vision.

• Rods are receptors adapted for vision in dim light.

The blind spot

It is called blind spot because there are no rods and cones on this area. So images that fall on this area of the retina are not “seen “

Hearing and vestibular senses

HearingThe Human Ear

AuditionThe sense of

hearing

The auditory receptors cell• Ear contains snail shaped organ called

cochlea, which contains the receptors for hearing.

• Any sound waves entering into the ear, strikes the eardrum and vibrates it.

• the vibration passes through these bones to cochlea. The auditory nerve transmits impulse to the brain that results in hearing.

• When these auditory nerve fibers are damaged, a person suffers nerve deafness.

The vestibular sense

In the inner ear adjacent to cochlea is a structure called vestibule.

Functions of The vestibular sense:• Maintain posture of body• Balance body• Detects head movement• Help us to keep our eyes fixated on a target

when head is moving.

Kinesthetic Sense

Receptors located in our muscles and joints.

Receptors are localized within the skin to detect physical stimuli in the outside world.Four classes of skin receptors:

• Touch: physical contact of objects with the skin.• Temperature of objects.• Pain: destruction of skin tissue.• Pressure :direct pressure on matrix ,bedsore

The Skin receptors cell

Touch Receptors are Nerve endings in the skin.

P A I N

What is pain?• PAIN is an unpleasant sensory associated

with actual or potential tissue damage.• Any stimulus that is intense enough to cause

tissue damage is a stimulus for pain.

• There are two different path ways to the brain on which pain can travel information brought from nerve endings in the skin to the brain . They are: Fast pathway and slow pathway.

• Fast pathway:

It sends the information to the cortex in a fraction of a second. e.g. (usually sharp pain) - cutting your finger with a knife.

• slow pathways It sends information through the limbic

system which takes about 1-2 seconds longer than the faster pathway. e.g. burning.

Factors in Pain Perception

• Expectations - research shows that our expectations about how much something will hurt can effect our perception.

• personality - people with negative types of personalities often have more pain.

• Mood - bad moods, angry, unhappy, etc, can lead to the experience of increased pain.

Gate control theory of pain

• According to this theory the incoming pain must pass through a "gate" located in the spinal cord which determines what information about pain will be sent to the brain.

• So, it can be opened to allow pain through or closed to prevent pain from being perceived.

Smell is the special sense that allows perception of odors through the stimulation of the olfactory nerve.

How the smell receptors cell The air passes through the nasal cavity

and though a thick layer of mucous to the olfactory bulb .The receptor cells of the olfactory bulb detect and recognizesmells.

N.BThe olfactory bulb is a region of the brain

that lies just below the frontal lobes .(

Receptor cells in the

upper nostrils

SweetSour

SaltyBitter

Taste refers to the ability to detect the flavor of substances such as food and poisons.

Traditionally, Taste sensations consisted of sweet, salty, sour, and bitter tastes.

What is Taste

The Taste receptors cell

The receptor cells for taste in humans are found on the surface of the tongue, along the soft palate, and in the epithelium of the pharynx and epiglottis.

The taste receptors occurs in clusters, called taste buds

At the ends of the taste buds are short, hair like structure that extend out and make contact with the solution in the mouth which result in an electrical impulses travels to the brain.

PerceptionThe recognition of patterns

The process of recognition means our brain needs to determine what the relevant objects are and where?

The Perceptual process include selection ,organization and interpretation.

Failure of recognitionThe general term for such breakdowns or disorders in recognition is amnesia.

What do you see in this picture?

Norris Edwards: Chapter 2: Wade02.ppt Page: 32

Revers

ible

Im

ag

es

Reversible Images

We perceive objects in the way that experience tells us

We understand the world through our senses, our “windows” on the world, Our reality,

In fact, is dependent upon two basic processes:

Sensation: Gathering informationPerception: Interpreting information

Summary

Sense Stimulus Receptors

Vision Light Energy Rods and cones in the eyes

Hearing Sound Waves Hair cells in the ears

Taste Chemical substances that contact the tongue

Taste buds on the tongue

Smell Chemical substances that enter the nose.

Receptor cells in the upper nostrils

Touch Movement of, or pressure on, the skin.

Nerve endings in the skin.

Quiz

What is the relevance of studying sensation and perception in

psychology for dental students ?

People who have suffered from certain kinds of brain damages fail in recognition. This disorder in recognition is called

AnemiaAgnosia AmnesiaAll of the above None of the above

…………..is an unpleasant sensory and emotional experience associated with actual or potential tissue damage.

Pain Cognition Behavior Attention None of the above

The receptors adapted for vision in dim light are

ConsCornea Pupil RodsNone of the above

All are the functions of the vestibular sense except

Maintain posture of bodyBalance bodyDetects head movementkeep our eyes fixated on a target when

head is movingFocus the light on the retina

The passive process of bringing information from the outside world into the body and to the brain is called:

Sensation Perception Receptors None of the above All the above

One of the visual receptors of the eye which adapted for colors vision and day time vision is :

Cones Rods Cornea Pupil None of the above

The active process of selecting ,organizing , and interpreting the information brought to the brain by the senses is called

Perception Sensation Recognition Reporting None of the above

Author Title Published Year Publisher

James W.Kalat Introduction to Psychology2008

Eighth Edition

Wadsworth/Thompson Learning,

References