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Sensation and Perception-what in the world is real?

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Mark White

on 18 March 2016

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Transcript of Sensation and Perception-what in the world is real?

Sensation and Perception
Somatosensory Perception
Pain
+
Gustatory Perception
Pain
touch
proprioception
Sense of
temperature and pain
Neural Pathways
of Somatosensation
receptors @ skin & musculoskeletal junctions
corpuscles(touch&pressure), nociceptor(pain)
Regular touch
Deep touch
Temperature information
Light touch
Myelinated or not?
Yes!
conduct information about pain
Quickly

No!
duller, longer-lasting pain that follows the initial pain
via the spinal cord to the brain
Samatosensory Processing
Primary somatosensroy Cortex
Secondary somatosensroy cortex
Sensory homunculus
somatosensory information for that part of body
Contains a somatotopic representation of the body:
More complex representations
projections across the corpus callosum
S2 in each hemisphere receives information from both sides of the body

Secondary somatosensory cortex
Primary somatosensroy Cortex
Taste
Smell
Stimulation by chemicals
-odorants
-tastants
Smell

-Chemical senses

Neural Pathways of Gustation
food molecule/ tastant
receptor in a taste cell

taste buds (tongue, cheeks, others)
gustatory nucleus @ dorsal medulla
VPM(Ventral posterior medial nucleus) @ thalamus
primary gustatory cortex
Basic tastes
Gustartory Processing
Humans can readily learn to discriminate similar tastes.
Insula cortex

dorsolateral prefrontal cortex
Orbitofrontal cortex
pleasantness and reward value of eating food
posteromedial:
highly rewarding
eat more
posterolateral:
unrewarding
don’t want to eat



The Direct connectivity Of Olfactory Cortex
—Limbic Cortex
(memory& emotion)
Olfactory Perception
Odors activate the limbic system more robustly than a related visual stimulus does when the stimuli are used to trigger meaningful personal memory.
Detecting a change in the external odor (the rate of sniffing)
The primary olfactory cortex
The Role of Sniffing
The Role of Sniffing
Identifying the smell itself (the presence of odor)
The secondary olfactory
Neural Pathway of Olfaction
Neural Pathways of Vision
Photorecepters
From the Eye to the Central Nervous System
Vision
Vision enables us to perceive information at a distance.
Vision information is contained in the light reflected from objects
Retina
Rods:
Sensitive to low levels of stimulation.

Most useful
at night
Cones:
Most active during
daytime
vision

Essential for
color
vision

Cones do not respond to colors per se
They differ in the sensitivity of their photopigments to different wavelengths of visible light
Rods and cones are
not
distributed
equally
across the retina
LG
N
V1
Axons of the ganglion cells

a bundle(the optic nerve)

central nerves system

Cortical Visual Areas
Area MT (V5)
Sensitive to

movement

and

direction
Do not show specificity in terms of the color of the stimulus
Cellular properties vary across cortical visual area
Clear evidence that the two tasks activated distinct brain regions
Neural Pathways of Audition
Cochlea
Hair cells
Primary Auditory Receptors
Receptive fields: Sound frequency
Human Auditory sensitivity: 20~20000 Hz.
(Best tuned 1000~4000 Hz)
High-frequency sounds Thick (base) end
Low-frequency sounds Apex end
The Cochlear Implant
Auditory Perception
What happens as sound waves enter the ear?
How does the brain process sound?
How does our brain interpret those waves?

vibration
vibration
vibration
inner ear
Inner ear’s fluid
Hair cells
Action potential
Mechanical signal Neural Signal
Partially
Restored Hearing
Sound Waves
Neuronal Impulses
Deficits in visual perception
Visual Deficits
Visual cortex is made up of many distinct regions,
which carry out specialized processing functions.
V4-color
V5-motion
Deficits in visual perception
In primary visual cortex
Achromatopsia-color-V4
Akinetopsia-motion-V5

Under the cortex (subcortical visual pathways)
Hemianopia
Scotomas
Blindsight

Other aspects
Depth perception
Deficits in color perception
1.Color-blind
2.Achromatopsia
3.Dichromats
4.Anomalous trichromats
Color-blind:
a person who has inherited a
gene
that produces an abnormality in the photoreceptor system.
Patients see the world without color.
Everything looked black, grey, or white.

People with only two photopigments.
It can be classified as red-green color blind and blue-yellow color-blind.
Dichromats
Anomalous trichromats
People have all three photopigments, but one has abnormal sensitivity.
74(normal)
21(abnormal)
Deficits in motion perception
Akinetopsia
A selective loss of motion perception.
Perception without a visual cortex
Sperior colliculus lesions
-spatial orientation

Visual cortex lesions
-object identification
Hemianopia
The lesion is restricted to the contralateral side of space.
Scotomas
Smaller lesions may produce more discrete regions blindness.
Blindsight
cross over to the thalamus on the opposite side before being projected to the cerebral cortex
Sensory Thresholds-What are they?
Each of the sense organs
that we have discussed and more have a threshold:

What is the smallest detectable difference between two weights

Ernst Weber: Law of Just noticeable differences and
difference threshold
What is the lowest amount sensed.....the "absolute threshold" that can be detected 50% of the time.

http://education-portal.com/academy/lesson/intro-to-sensation-and-perception.html#lesson



Extreme Enhanced Sensory Skills
These skills are a combination
of brain and senses-
Sensory or Perception.
Full transcript