Visual Perception and Distortions

Visual Perception and Distortions

Unit 2: AOS 1 Chapter 7

Sensation and Perception

• Sensation is the process by which our sensory receptors and sense organs detect and respond to sensory information that stimulates them. The information at this stage is simply raw sensory data. 

• Perception refers to the process by which we give meaning to sensory information. This processing results in the conscious experience of our external (and internal) environments. 

Sensation and Perception: Reception

• Reception is the process of detecting and responding to incoming sensory information. 

• A receptive field is the area of space in which a receptor can respond to a stimulus. For example, when you look directly in front of you, everything you see is the receptive field of your eyes.

Sensation and Perception: Transduction

• The brain can not process many of the energy that is received by the body, therefore a process of conversion needs to occur.

• Transduction is the process by which the receptors change the energy of the detected sensory information into a form which can travel along neural pathways to the brain as action potentials (which are also called neural impulses).

• With vision this involves converting light into neural impulses

Sensation and Perception: Transmission

• Transmission is the process of sending the sensory information (as action potentials) to relevant areas of the brain. 

• The area for visual transmission is the primary visual cortex in the occipital lobe

Sensation and Perception: Interpretation

• Interpretation is the process in which incoming sensory information is given meaning so that it can be understood.

• Interpretation involves bringing together incoming sensory information and using existing knowledge (eg memories) to make sense of sensory input.

Multiple Choice

Reception involves

• making meaning and perception

• changing energy to a different form

• sending messages in the form of neural messages

• detecting and responding to sensory information

Multiple Select

Without transduction, neural messages can not be sent to the brain.

• True

• False

Multiple Select

There is a clear point in the process, when sensation ends and perception begins.

• True

• False

Multiple Select

The correct order is:

• Transduction; Transmission;

  Reception; Interpretation

• Transduction; Reception;

  Transmission; Interpretation

• Reception; Transduction; Transmission; Interpretation

• Reception; Interpretation;

  Transduction; Transmission;

How we see

• The visual sensory system consists of a complete network of physiological structures involved in vision

• Stimulus: light is reflected, or given out by, a visual image and enters the eye.

• Let's take a closer look at the eye.

The eye

• CORNEA: Transparent, convex-shaped (curved outwards) covering which protects the eye and helps to focus light rays onto the retina at the back of the eye

• AQUEOUS HUMOR: A watery fluid which helps to maintain the shape of the eyeball and provides nutrients and oxygen to the eye, as well as carrying away waste products

• PUPIL: An opening in the iris that helps to control the amount of light entering the eye.

• 
  

The eye

• IRIS: The coloured part of the eye consisting of a ring of muscles that expand or contract to change the size of the pupil and control the amount of light entering the eye

• šLENS: A transparent, flexible, convex structure located immediately behind the pupil which plays a major role in focusing light onto the retina

The eye

šCILIARY MUSCLES: These muscles expand and contract, enabling the lens to automatically bulge to focus nearby objects onto the retina and flatten to focus distant objects onto the retina

šVITRIOUS HUMOR: a jelly-like substance which helps to maintain the shape of the eyeball and also helps focus light

The eye

• šRETINA: Layer of neural tissue at the back of the eye that receives and absorbs light, and processes images for transmission to the brain (reception and transduction occurs here)

  šPHOTORECEPTORS: A light-sensitive visual receptor cell in the eye; see rods and cones

Photoreceptors:

• šRODS: Photoreceptor in the eye’s retina that responds to very low levels of light; primarily responsible for night vision

  šCONES: Photoreceptor in the retina of the eye that responds to high levels of light and is primarily responsible for vision in light / bright conditions , colour vision and detecting fine details.

The eye

• šOPTIC NERVE: Carries visual information from the retina to the primary visual cortex.

  šBLIND SPOT: A small area on the retina at the back of the eye where there are no photoreceptors so light cannot be detected.

  šOPTIC CHIASM: Point where the axons of ganglion cells in the optic nerve cross.

_{Reception & transduction}

• Electromagnetic energy in the form of light enters the eye

• Photoreceptors rods & cones detect and respond (reception) AND change (transduce) the electromagnetic energy (light) into the electrochemical energy (a nerve impulse)

• The electromagnetic energy has now been changed into electrochemical energy

  
  

Transmission

• Neural messages are sent or transmitted via the optic nerve (from the photoreceptors to the thalamus and then visual cortext in the occipital lobe

• Transmission can not occur without transduction

• Neural message are also called action potentials

Interpretation

• When neural messages (or action potentials) are received by the primary visual cortex (in the occipital lobe), interpretation occurs.

• Other lobes in the brain will also play a role. For example interpretation (or perception) will occur by drawing on memories.

Multiple Choice

Without this structure, the lens would not be able to function (bulge and flatten) as it does.

• Pupil

• Retina

• Ciliary muscles

• Rods and Cones

Multiple Choice

Which structure of the eye "protects the eye"?

• lens

• cornea

• aqueous humour

• virtious humour

Multiple Choice

The amount of light entering the entire eye is controlled by the:

• iris

• cornea

• retina

• lens

Multiple Choice

Which statement about rods is false:

• Rods are photoreptors

• Rods respond in low light conditions

• Rods respond in bright and light conditions

• Rods detect fine details and colour

Multiple Choice

The primary visual cortex (which plays an important role in interpretation of a visual stimuli) is located in the

• frontal lobe

• parietal lobe

• thalamus

• occipital lobe

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Multiple Choice

The occipital lobe is the ___ section of the brain.

• purple

• pink

• blue

• green