Perception

Definitions:

sensation – simple awareness due to the stimulus of a sense organ

perception – in order to form a mental representation the organization, identification and interpretation of a sensation needs to occur 

transduction – the action of converting energy or messages into a different form

receptive field – the regions of a sensory surface, that when stimulated it causes the change in the firing rate of the certain neuron

object agnosia – when an individual loses the power to recognize familiar objects or people

optic ataxia – lack of muscular coordination

binocular disparity – the differences in the retinal images that provide the information about depth to the two eyes

monocular depth cues – the aspects of a scene that sends information about depth when viewed by one eye

pitch - how high or low a sound is in frequency

loudness - a sound's intensity

timbre - the character of a sound (for example, a C note played by a guitar is rather different than one played by a flute)

phoneme - the smallest unit of sound that is recognizable by speech

morpheme – the smallest meaningful units of language

pain gate – part of the central nervous system that opens and closes to allow pain messages through to the brain or to block them

Learning Objectives:

Describe components of perception (external stimulus, sensory receptor, sensory neurons, CNS) as they relate to vision, hearing, and pain

• vision -light -rods and cones -bipolar cells -retinal ganglion cells -optic nerve -optic chiasm -lateral geniculate body of the thalamus -occipital lobe -dorsal (to parietal lobe) and ventral (to temporal lobe) streams
• hearing -sound waves -hair cells on basilar membrane in cochlea -auditory nerve -some cross in brain stem -medial geniculate body of the thalamus -temporal lobe -frontal lobe -parietal lobe
• pain - composed of somatosensory pathway (A beta fibers -thalamus -cortex) and pain pathway (A beta fibers -cross over in spinal cord -thalamus -cortex -limbic system). Also remember that C fibers, which are slow, large, and unmyelinated, continue sending signals to remind you of the pain after the initial stimulus.

Identify the functions of the cornea, iris, lens, retina, rods, and cones.\

• cornea - focus light on the retina, protect lens and hold in eye fluids
• iris - control amount of light hitting retina
• lens - refract light on retina
• retina - transduce light into electrical impulses to be read by the nervous system
• rods - low light transduction mechanism, allows for grayscale perception in the dark
• cones - high light transduction mechanism, allows for color perception

Contrast the trichromatic and opponent-process theories of color vision

• Trichromatic color representation calls for the three types of cones having a unique code for each color, whilst the color-opponent system calls for a pairing of neurons that work in opposition to each other.

Describe deficits and pathways associated with object agnosia and optic ataxia

• Object agnosia is not being able to recognize familiar objects or faces
• Optic ataxia is the lack of muscular coordination

Apply monocular cues to describe perception of depth

• monocular cues are also know as pictorial depth cues, due to the fact that they are also present in two dimensions, when the third dimension depth is not really there
• This allows us to view the third dimension

Gestalts Principle

• The many aspects of human perception include:
• Simplicity- when confronted with two or more interpretations of the objects shape, the visual system tend to choose the simplest or more likely interpretation
• Closure- tending to fill in the missing elements of a scene, allowing us to perceive the edges that are separated by the gaps as they belong to the complete whole object
• Continuity- the edges or contours that have the same orientation, and we also tend to group them together perceptually
• Similarity- objects that are similar in color, lightness, shape, or texture perceived to belong  to the same group
• Proximity- objects seen close together are tended to be grouped together
• Common fate- elements of a visual image that move together are seen as part of a single moving object
• Figure 4.18 within the text book for images
• Figure- ground – separating an object from its surroundings

• Identifying the figure apart from the background

Identify the functions of the outer, middle, and inner ear

• The outer ear collects the sound waves and sends them towards the middle ear
• The middle ear transmits the vibrations to the inner ear
• The inner ear changes which is embedded into the skull, changes the vibrations into neural impulses

Apply the fuzzy logic model of speech perception to understanding spelling errors

• learning new words, there are several spellings to produce morphemes and phonemes. This leads to spelling errors.

Compare/ contrast the structures and functions of C, A-delta, and A- beta fibres

• C fibres are unmyelinated, and cause a long term throbbing pain
• A-delta fibres are myelinated, small, fast, sharp immediate pain. These are impaired sometimes due to the PAG (periaqueductal gray)
• A-beta fibres, in the somatosensory pathway, are myelinated, very small, and deliver immediate pain very quickly.

Describe the sensation of and responses to pain

• It hurts and it causes us to react really fast to that pain, and continues to hurt in order to remind us that we have recently had an injury (or still do)

Describe the gate-control theory of pain

• The interneurons in the spinal cord are able to stop the signals arriving from the pain receptors from the body, also feedback from two directions
• Melzack and Wall, 1960’s
• Immediate pain -interneurons -CNS -frontal cortex -PAG -gate closed

Recognize examples of top-down and bottom-up processes in pain perception

• top-down processes means that cognition is activating the PAG and preventing pain perception (or creating phantom pain through the self-activation of pain pathways)
• bottom-up processes are the regular somatosensory and pain pathways that reach the brain

Apply the gate-control theory of pain to understand the nature, origin, and treatment of phantom limb pain

• this is a top-down process of creating pain. Phantom limb pain is completely caused by the unconscious brain. It can be treated through drugs (opiates and antidepressants), accupuncture, accupressure, electrical stimulation (the last three stimulate A-beta fibers to release endorphins), surgical cordotomy (sever the nerves), or cognitive modulation (to trick the brain).

Thought Question:

The pain gate has both bottom-up and top-down components. This is why it is so difficult to treat pain. Describe how and where in the pain gate drugs, acupuncture/acupressure/electrical stimulation, surgery, and cognitive/affective therapy work.

• Drugs
• Opiates: Opiate receptors in thalamus and PAG: affected whether it opens or closes
• Antidepressants: Increase serotonin
• Accupuncture/Accupressure/Electrical Stimulation
• Stimulate large A beta fibers
• Release endorphins (endogenous opiates)
• Surgery
• Cordotomy (sever the neurons)
• Cognitive and affective modulation of pain
• “Trick” the brain