Ch 2: Sensation and Perception Flashcards
Explain the structure and function of the organ of Corti.
The hearing apparatus
Housed in the middle scala of the cochlea, it rests on a thin flexible membrane (basilar membrane). It is composed of thousands of hair cells bathed in endolymph
What happens in the cochlea to allow us to hear?
Sound enters the cochlea through the oval window, causing vibrations in perilymph, which are transmitted to the basilar membrane. The round window permits perilymph to move around. The hair cells on organ of Corti convert the physical stimulus into an electrical signal to be carried to CNS
vestibule
the portion of the bony labyrinth containing the utricle and saccule. Used as part of the balancing apparatus and to determine orientation in 3D space
otoliths
resist motion of acceleration, bending and stimulating the underlying hair cells, which send a signal to the brain
semicircular canals
sensitive to rotational acceleration
Which cochlear structure is sensitive to linear acceleration?
vestibule
Which cochlear structure is sensitive to rotational acceleration?
semicircular canals
When you rotate your head, what is resisting this motion in the cochlea, bending the underlying hair cells?
ampulla
What is the role of inferior colliculus in the auditory pathway?
it is involved in the startle reflex and helps keep the eyes fixed on a point while the head is turned (vestibulo-ocular reflex)
What is the role of superior colliculus in the visual pathway?
it controls some responses to visual stimuli and reflexive eye movements
Describe the auditory pathway
hair cells < vestibulocochlear nerve < medial geniculate nucleus (MGN) of the thalamus < auditory cortex in temporal lobe for sound processing
some information sent to superior olive (localizes sound) and inferior colliculus (startle reflex, vestibulo-ocular reflex)
How do hair cells in the organ of Corti convert the physical stimulus into electrical signal?
When vibrations reach the basilar membrane, hair cells start swaying back and forth. This swaying causes the opening of ion channels, causing a receptor potential
Where in the cochlea would you most typically find vibrations of the basilar membrane if a high-frequency pitch was encountered?
close to the oval window
Where in the cochlea would you most typically find vibrations from low-frequency pitches?
at the apex, away from the oval window
how would the brain differentiate between pitches of sounds?
cochlea is tonotopically organized; high frequency pitches stimulate hair cells closer to the oval window, while high frequency pitches stimulate hair cells farther from the oval window (at the apex)
What is sensation
a raw signal from the receptors in the PNS forwarded to the CNS in the form of action potentials and neurotransmitters
what is transduction
the conversion of physical, electromagnetic auditory, and other information from our internal and external environment to electrical signals in the nervous system
aligns with sensation
What is perception
the processing of external sensory information and internal activities of CNS to make sense of its significance.
Helps us make sense of the world
What is the general sensory pathway in which a stimulus undergoes to be processed?
stimulus < receptors (sensory cells or nerve endings) < ganglia (transmits data from receptors to CNS) < projection areas, which further analyzes the sensory input
what is threshold
the minimum amount of a stimulus that renders a difference in perception
what is absolute threshold
the minimum of stimulus energy that is needed to activate a sensory system (a threshold in sensation, not perception). A stimulus below this threshold never reaches the CNS
how BRIGHT, how LOUD, how INTENSE a stimulus must be before it is sensed
What is the threshold of conscious perception
the minimum of stimulus energy needed for it to reach higher order brain regions that control attention and consciousness
a stimulus below this threshold arrives at the CNS, but are not perceived (subliminal perception)
What is the difference threshold or “just-noticeable difference”
the minimum difference in magnitude between two stimuli before one can perceive this difference
more important to focus on the ratio between change in stimulus and the original value rather than the actual difference (formalized by Weber’s Law)
What is Weber’s Law?
states that there is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
for higher magnitude stimuli, actual difference must be larger to produce a jnd
Signal detection theory
changes in perception of the same stimuli depending on both internal (psychological) and external (environmental) context
response bias
tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors
what is adaptation wrt stimulus detection
detection of a stimulus changes over time. A way for our mind and body to try and focus attention on only the most relevant stimuli (changes in environment)
The eye is _____ by choroidal/retinal vessels, _____ by sclera, and _____ via retina
The eye is nourished by choroidal and retinal vessels, protected by the sclera, and sees via retina
under sympathetic stimulation, what happens to the iris and pupil? Under parasympathetic stimulation?
Sympathetic: the dilator pupillae opens the pupil
Parasympathetic: the constrictor pupillae constricts the pupil
what does the ciliary body produce?
aqueous humor
Contraction of the ciliary muscle is under what autonomic control?
Parasympathetic
what happens during the phenomenon called accommodation
the lens change shape as muscle contraction pulls on the suspensory ligaments
duplexity or duplicity theory of vision
the theory that states that the retina contains 2 kinds of photoreceptors: one for light/dark detection and one for color detection
What is the correlation between resolution and the number of receptors converging through the bipolar neurons onto one ganglion cell?
An increase in number of receptors converging through bipolar neurons onto one ganglion, decreases the (loss of detail)
cones have less convergence onto one ganglion than rods, thus color vision has greater sensitivity to fine detail
What are amacrine and horizontal cells important for?
edge detection and increase perception of contrasts
what event occurs at the optic chiasm
the nasal fibers (which carry temporal visual field) of each retina cross paths
parallel processing
the ability to simultaneously analyze and combine information regarding color, shape, and motion. Then these features can be compared to memories to determine what is being viewed
feature detection
assert that visual pathways contain cells specialized in detection of color, shape, or motion
shape detected by parvocellular cells, has high spatial resolution (rich in detail), low temporal resolution (slow)
motion detected by magnocellular cells; has high temporal resolution (fast), low spatial resolution
what are olfactory chemoreceptors (olfactory nerves)
located in olfactory epithelium in the upper part of the nasal cavity, specific types allow us to recognize subtle differences in similar scents.
Chemical stimuli bind to these chemoreceptors to stimulate a signal
pheromones
secreted by one person or animal, and once bonded with chemoreceptors, compel or urge another to behave in a specific way
Describe the olfactory pathway
odor mlcs inhaled and make contact with olfactory nerves in olfactory epithelium < receptor cells activated < signal sent to olfactory bulb < signals relayed via olfactory tract to higher regions of brain
***only sense that does not pass through thalamus; travels unfiltered
Pacinian corpuscles
respond to deep pressure and vibration
Meissner corpuscles
respond to light touch
Merkle cells (discs)
respond to deep pressure and texture
Ruffini endings
responds to stretch
Free nerve endings
respond to pain and temperature
two-point threshold
the minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli
the size of the two point threshold depends on the density of nerves in the particular area of skin being tested
physiological zero
the normal temperature of the skin (between 86 and 97 deg F)
object feels cold when under; feels warm when over
Gate theory of pain
proposes that there is a special “gating” mechanism that can turn pain signals on or off, affecting whether or not we perceive pain. The spinal cord is able to preferentially forward the signals from other touch modalities to the brain, reducing the sensation of pain
e.g., explains why rubbing an injury seems to reduce the pain of the injury
proprioception (kinesthetic sense)
the ability to tell where one’s body is in space
receptors mostly found in muscle and joints
Bottom-up (data-driven) processing
object recognition by parallel processing and feature detection
brain takes individual sensory stimuli and combines them together to create a cohesive image before determining what object is
top-down (conceptually driven) processing
driven by memories and expectations that allow brain to recognize the whole object and then recognize the components based on expectations
allows for quick recognition of objects without needing to analyze specific parts
perceptual organization
the ability to use bottom-up and top-down processing in tandem with all of the other sensory clues about an object, to create a complete picture or idea (although most of the images we see in everyday life are incomplete, we fill in gaps using Gestalt principles)
Depth perception
can rely on both monocular and binocular cues (one or both eyes)
monocular include relative size of objects, partial obscuring of one object by another, convergence of parallel lines at a distance, position of an object in visual field, and lighting and shadowing
binocular cues are slight differences in images projected on the two retinas and the angle required between the 2 eyes to bring an object into focus
Gestalt principles
ways for the brain to infer missing parts of a picture when a picture is incomplete
- proximity
- similarity
- good continuation
- subjective contours
- closure
Taken altogether, Gestalt principles governed by law of pragnanz
Law of proximity
elements close together perceived as one unit
Law of similarity
similar objects grouped together
Law of good continuation
elements that appear to follow in same pathway grouped together
Law of subjective contours
perceive contours and shapes not actually present
Law of closure
when space is enclosed by a contour, it tends to be perceived as a complete figure
Law of pragnanz
perceptual organization will always be as regular, simple, and symmetric as possible
