Week 12: (Nov. 20, Thanksgiving): Intro to sensation & perception & the eye
- Sensation – detection of external stimulus energy.
- Perception – brain’s further processing of these detected signals.
- Transduction – translation of the stimuli into chemical and electrical signals.
- Qualitative info – deals with differentiating between diff taste, smells, and sights.
- Quantitative info – deals with differentiating the intensity of the senses.
- Signal detection theory – getting the sensation but judging your senses. Sometimes you can
be wrong when you someone ask if you see something. You might convince yourself that you
- Sensory adaption – to be adapted to something. Hearing cars go by while you study, you tend
to ignore the sounds of the cars going by.
o Other terms for this is gustation
o Taste receptors are located in the taste buds.
o Some are supertasters.
o Babies tend to be fonder of whatever the mom indulges herself with when pregnant
and after pregnancy.
o The only sense that does not go through the thalamus first.
o Odors go to the olfactory epithelium (thin layer with receptors)
o These receptors transmit the info the olfactory bulb (the brain center for smell)
o It is interpreted in the prefrontal cortex (related to memory and emotions)
o Haptic sense
o Two types of pain:
Fast fibers: sharp pains, myelinated
Slow fibers: dull, steady pain. Non-myelinated
o Comes from sound waves.
o Comes into the eardrum; shakes the other systems in the ear.
o Cochlear implants stimulate the auditory nerves rather than amplifying the sound.
Week 13 (Nov. 27, 29) Color vision, brightness, depth perception, & illusions
Text: Ch.4, 150-179
Anatomy of the Eye:
- Our eyes are the most important source of knowledge.
- Procedure of sensation and perception so the sense of sight
o Light goes through the cornea which focuses the light
o Then the light enters the lens
o The lens bend the light inwards to the retina
o Signals sent to the ganglion cells down the axons.
o Axons bundle together through the optic nerve (blind spot)
o At the optic chiasm, the bundle splits into two (left eye & right eye)
o Reaches the thalamus and travels to the primary visual cortex
- The retina contains photoreceptors that transduce light into neural signal.
- The pupil is the small opening in front of the lens.
o It determines how much light enters the eye. - The iris is the eye color and controls the pupil size.
- Muscles in the eye flatten to see distant objects; thickens to see close objects –
- Image on the retina is projected upside down.
- In the retina:
o Rods – night vision; about 120million
o Cones – daytime vision; about 6 million. Mostly located in the middle – fovea
- Color of light is determined by the wavelength of the electromagnetic waves.
- In Trichromatic Theory, cones are separated in three types: one is sensitive to short
wavelengths (blue-violet), two and med wavelength (yellow-green), and three is long
- In the opponent process theory, we see color opposites as an afterimage after looking at a
color for long enough.
- We categorize color along the dimensions: hue (the color), Saturation (specific color),
Brightness (total light reaching eye).
- Subtractive color mixing: process of color mixing; physical process. Whatever
wavelength not absorbed is the color you will see; “left-overs”
- Any color can be created with the presence of the three wavelength types.
- Kinesthetic sense – perception of the positions in space and movements of our bodies and
- Vestibular sense – perception of balance. Receptors in the ear.
- Info is projected to the primary somatosensory cortex located in the parietal lobe.
- Gate control theory of pain – the closing of the neural “gate” in the spinal cord to reduce
the perception of pain.
- When distracted, the gate closes diminishing the intensity of the pain.
- When anxious and worried about the pain, the gate opens wider.
- Info is projected to the primary auditory cortex located in the temporal lobe.
- We perceive where the sound is coming from by which ear hears the sound first.
- Info is projected to the primary visual cortex located in the occipital lobe.
- The visual cortex has two streams:
o Ventral stream: perceiving shapes and color; “what” stream.
o Dorsal stream: perceiving spatial whereabouts; “where” stream.
- People suffering from carbon monoxide poisoning lose their ventral stream; object
- Blindsight – losing only a portion of one’s vision.
- Gestalt principle:
o Proximity: we group things that are close to each other.
o Similarity: we group things by how closely they resemble each other.
- Good continuation – tendency to interpret intersecting lines as continuous lines.
- Bottom-up processing – data relayed in brain from lower to higher levels of processing. - Top-down processing – info at higher levels of mental processing can influence lower
o What we expect to see can influence what we perceive
- Perceiving face is important because it tells a person’s sex, mood, ethnicity, age, etc…
- Perceiving face is specialized in the fusiform gyrus, located in the right hemisphere.
- People have a hard time recognizing face upside down.
- The amygdala detects emotional significance on the face.
- Binocular depth cues – are in both eyes and contribute to bottom-up processing
- Monocular depth cues – contribute to the top-down processing.
- For images close to us:
o Binocular disparity – cue is caused by distance between the two eyes. The brain
uses the disparity (difference) between the two images from each eye to compute
the distances to nearby objects.
- Convergence – refers to the way our eye turns inwards when we view nearby objects.
- Size perception:
o Ames box – far away as small and closers as bigger image.
o Ponzo illusion – shows how the brain uses depth cues when depth is absent. (the
one line is bigger than the oth