C2 - Sensation And Perception Flashcards
What is sensation
The taking of physical, electromagnetic, auditory, and other info from our internal and external environment to convert into electrical signals in the nervous system
What is perception
The process of processing information within the CNS in order to make sense of the informations significance
What is proximal and distal stimuli?
Proximal stimuli directly interacts with and affects the sensory receptors, this informs the observer about the presence of distal stimuli
What is psychophysics
The study of the relationships between the physical nature of stimuli and the sensation/perceptions they evoke
Ganglia
Collections of neurons cell bodies found outside of CNS
What are osmoreceptors?
Receptors that respond to changes in osmolarity of the blood (water homeostasis)
Sensory stimuli is transmitted where in the brain?
Projection areas, which further analyze the sensory input
All sensory information is sent to the CNS in the form of…
Action potentials
What is threshold
The minimum amount of stimuli that renders a difference in perception
What are the 3 main types of thresholds
-Absolute threshold
-Threshold of conscious perception
-Difference threshold
What is absolute threshold
The minimum intensity at which a stimulus must be to be transduced (converted into action potentials)
In other words it is about how bright, far, loud, or intense a stimulus must be before it is sensed
What does the stimulus never reach if it is below the absolute threshold
The central nervous system
What is the threshold of conscious perception
The level of intensity that a stimulus must pass in order to be consciously perceived by the brain
What is subliminal perception?
Information that is received by the CNS but does not cross the threshold of conscious perception
Main difference in being below absolute threshold vs below threshold of conscious perception
Below absolute threshold the stimulus will never be transduced and thus never reach the CNS
Below the threshold of conscious perception the stimulus arrives at the CNS but does not reach the higher-order brain regions that control attention and consciousness
What else is the difference threshold called?
The just noticeable difference (jnd)
What is the difference threshold?
The minimum change in magnitude required for an observer to perceive that two different stimulus are, in fact, different
If below the difference threshold, 2 possibly different stimuli will seem to the observer as…
The same
What happens in a common psychophysical discrimination testing experiment?
A participant is presented with a stimulus, it is then varied slightly until they report a change in stimuli, it is then recorded as the just noticeable difference
The just noticeable difference or difference threshold is usually reported or recorded as…
A fraction or percentage
Who was often credited with the observation that difference thresholds are proportional and must be computed as percentages?
Ernst Heinrich Weber
Often called the Webers Law
What does the signal detection theory study?
The effects of nonsensory factors such as experiences (memory), motives, and expectations on perception of stimuli
Both external and internal factors
Example in signal detection theory; how loud would someone have to tell your name in a crowd for you to notice? Well this comes down to what factors?
-Environmental factors
-Social factors
-Psychological factors
-Personality factors
A basic signal detection experiments consists of many trials, what is presented in these trials?
During each trial a stimulus may or may not be presented
Trials in which the signal is presented, and those without a signal are called…
-Noisy trials- are those with a presented signal
-Catch trials- are those without a presented signal
What are the 4 possible outcomes for each trial in a signal detection theory expirement?
A hit - a trial in which the signal is presented and the subject correctly perceives the signal
A miss - a trial in which the subject fails to perceive the presented signal
A false alarm - a trial in which the subject indicates perceiving the signal, even though the signal was not presented
A correct negative - a trial in which the subject correctly identifies that no signal was present
Our ability to detect a stimulus can change over time through repeated stimulation, if we start to block it out of our notice this is due to?
Sensory Adaption
Most of the exposed portion of the eye is covered by a thick structural layer known as…
The sclera
What is the colored part of the eye?
The iris
What is the white part of the eye?
The sclera
What covers the frontmost portion of the eye?
The cornea
The eye is supplied from nutrients by what 2 sets of blood vessels?
The choroidal vessels - a complex intermingling of blood vessels between the sclera and retina
Also the retinal vessels
What is the innermost layer of the eye?
The retina
What does the Retina contain?
Photoreceptors that transduce light into electrical information the brain can process
Photons of light to electrical signals
Cornea function
Gathers and focuses the light
What are the 2 chambers and there locations in the eye?
Anterior chamber - lies in front of the iris
Posterior chamber - between the iris and lens
The iris is composed of what 2 muscles?
Dilator pupillae - opens the pupil under sympathetic stimulation
Constrictor pupillae - constricts the pupil under parasympathetic stimulation
What 2 things is the iris continuous with?
The choroid, and the ciliary body
What is the choroid and it’s function?
It is a vascular layer of connective tissue that surrounds and provides nourishment to the retina
What is the ciliary body function?
Produce the aqueous humor that bathes the front part of the eye
Where does the aqueous humor drain into?
The canal of schlemm
Where is the lens and what is its function?
The lens is right behind the iris and helps control the refraction of the incoming light
What muscle is a component of the ciliary body, and what does it do?
The ciliary muscle, it is under parasympathetic control, when contracted, it pulls on the suspensory ligaments and changes the shape of the lens to focus on a image as the distance varies
A phenomenon called accommodation
What type of humor lies behind the lens?
The vitreous humor, a transparent gel that supports the retina
What is the retina considered a part of?
The CNS, as it’s a developed outgrowth of brain tissue
What is the duplicity or duplicity theory of vision?
It states that the retina contains 2 types of photoreceptors
-those specialized for light and dark detection
-those specialized for color detection
The retina is made up of approximately how many cones and rods?
6 million cones and 120 million rods
What are cones used for?
Color vision and to sense fine details, most effective in bright light
What forms do cones come in?
Cones come in 3 forms which are named for the wavelengths of light they best absorb
-Short (blue) wave
-Medium (green) wave
-Long (red) wave
When are rods most functional?
In reduced light because they are highly sensitive to photons
Only allow sensation of light and dark
All rods contain only a single pigment called
Rhodopsin
Why are rods less useful for detection of fine details?
Because rods are spread over a much larger area of the retina
What is the central location of the retina called?
The Macula
What does the macula contain?
A high concentration of cones
What is the center most region of the macula called? And what does it contain?
The Fovea, contains only cones
The further away you move from the fovea the more concentration of what?
Rods, and less of cones
Visual acuity is best at…
The Fovea
What leaves the eye?
The optic nerve
Region of the retina which is devoid of photoreceptors?
The optic disk, gives rise to a blind spot
Rods and cones do not connect directly to the optic nerve, instead what do they connect to? Describe them
Layers of neurons in between
First they synapse directly to bipolar cells, which highlight gradients between adjacent rods and cones
Then bipolar cells synapse with ganglion cells, axons of which group together to form the optic nerve
Bipolar and ganglion cells are located in front of rods and cones too, what does this mean?
That a photon must actually navigate past several layers of cells to reach the rods and cones at the back of the retina
As the number of receptors that converge through the bipolar neurons onto one ganglion cell increases, the resolution…
Decreases
multiple input signals are combined, resulting in a lower level of detail or resolution.
What do amacrine and horizontal cells do?
help enhance the contrast and highlight subtle variations in visual information by collecting input from multiple retinal cells within a specific region. This allows them to refine the signals before passing them on to ganglion cells, ultimately aiding in the perception of finer details and contrasts in the visual scene.
If an object is to your left than the photons from that object stimulate what side in each eye?
The right side of retina in each eye
An object in the nasal field of the right eye stimulates what fibers in the right eye?
The temporal retinal fibers
An object in the temporal field of the left eye would stimulate what fibers if the left eye?
The nasal retinal fibers
As the retinal fibers from each eye travel from the optic nerves what happens at the optic chiasm?
The nasal retinal fibers from the left and right eyes cross paths (only the nasal fibers)
Why do the temporal retinal fibers not need to cross?
Because they are already the fibers stimulated on the opposite side of your body from the object
After leaving the optic chiasm the reorganized pathways are called…
Optic Tracts
From the optic chiasm some nerve fibers go through where in the thalamus? After of which how do they get to the visual cortex?
Some nerve fibers pass through the lateral geniculate nucleus (LGN) in the thalamus where they synapse with nerves that pass through radiation’s in the temporal and parietal lobes to the visual cortex in the occipital lobe
Other fibers from the optic chiasm branch from the optic tract, skip the thalamus and head directly where?
The superior colliculus in the midbrain
(For reflexes)
What is visual parallel processing
The brains ability to analyze information regarding color, form, motion, and depth simultaneously
What does form refer to?
Not only the shape of an object, but also our ability to discriminate an object of interest from the background by detecting its boundaries
Neurons carrying information from the fovea and surrounding central portion of the retina synapse with what cells?
Parvocellular cells in the Lateral Geniculate nucleus
What are the attributes of Parvocellular cells?
They have very high color spatial resolution; permit us to detect very fine details when thoroughly examining an object
However these cells can only work with stationary or slow moving objects due to very low temporal resolution
What are magnocellular cells well suited for detecting?
Motion, due to very high temporal resolution
But have low spatial resolution therefore they provide a blurry but moving image of an object
Where in our vision does magnocellular cells predominately receive inputs from?
Periphery of our vision
What is depth perception?
What does it heavily rely on?
Our ability to discriminate the 3-d shape of our environment and judge the distance of objects within
Heavily dependent on discrepancies between the inputs the brain receives from both eyes
What specialized cells in the visual cortex are responsible for comparing the inputs to each hemisphere and detecting the differences?
Binocular neurons
What do feature detectors help with?
Help out brain learn to associate patterns of stimuli with expected behaviors or outcomes
Each feature detector cell type detects a very particular, individual feature of an object in the visual field
What is our vestibular sense?
Our ability to both detect rotational and linear acceleration and to use this information to inform our sense of balance and spatial orientation
Where does a sound wave first reach?
The cartilaginous outside part of the ear called the pinna or auricle
What is the auricles function?
To funnel sound waves into the external auditory canal
External auditory canal function
Directs sound waves to the tympanic membrane
What happens when the sound waves reach the tympanic membrane
The tympanic membrane vibrates in phase with the incoming sound waves
What divides the outer ear from the middle ear?
The tympanic membrane
The middle ear houses what bones?
The ossicles which are the smallest 3 bones in the body
Ossicles function
Help transmit and amplify the vibrations from the tympanic membrane to the inner ear
What is the order of ossicles following the tympanic membrane?
Malleus, incus, then stapes
What does the baseplate of the stapes rest on?
The oval window of the cochlea, which is the entrance to the inner ear
How is the middle ear connected to the nasal cavity?
Via the Eustachian tube
Eustachian tube function
Helps to equalize pressure between the middle ear and the environment
What does the inner ear sit within?
A bony labyrinth which is a hollow region of the temporal bone containing the cochlea, vestibule, and semicircular canals
Inside the bony labryinth rests a continuous collection of tubes and chambers called…
The membranous labyrinth
The membranous, and bony labyrinth is filled with what?
Membranous labyrinth is filled with potassium rich fluid called endolymph; it’s suspended within the bony labyrinth by a thin layer of fluid called perilymph
What contains the receptors for hearing? What parts does it have?
The cochlea, it’s divided into 3 parts called scalae
What does the middle scala house?
The actual hearing apparatus called the Organ of Corti
What does the organ of corti rest on?
A thin, flexible membrane called the basilar membrane
Organ of corti contains thousands of what cells?
Hair cells that are bathed in endolymph
What is on top of the organ of corti?
A relatively immobile membrane called the tectorial membrane
What are the other 2 scalae composition and location?
The other 2 are filled with perilymph, surround the hearing apparatus, and are continuous with oval window and round window
When sound enters the cochlea through the oval window what does it cause transmitions to and vibrations in?
Causes vibrations in perilymph, which are transmitted to the basilar membrane
What is the round window?
A membrane covered hole in the cochlea
Because fluids are essentially incompressible, the round window permits the perilymph to do what?
Actually move within the cochlea
What does the hair cells of the organ of corti do?
Transduce the physical stimulus into electrical signals which is carried to the central nervous system by the auditory nerve (vestibulocochlear nerve)
Where and What does the vestibule contain? What is its function?
Located in the bony labyrinth it contains the utricle and saccule, which are sensitive to linear acceleration, and used as part of the balancing apparatus, determine one’s orientation in 3-D space
Utricle and saccule contain modified hair cells covered with…
Otoliths
As the body accelerates what does the otoliths do?
Resist the motion, this bends and stimulates the underlying hair cells sending signals to brain
What does the cochlea detect?
Sound
The utricle and saccule detect?
Linear acceleration
The semicircular canals detect?
Rotational acceleration
What is the auditory pathway? (Full pathway)
Cochlea to vestibulocochlear nerve to medial geniculate nucleus (MGN) of thalamus to auditory cortex
What is the visual pathway? (Full pathway)
Retina to optic nerve to optic chiasm to optic tracts to lateral geniculate nucleus (LGN) of thalamus to visual radiations to visual cortex
The semicircular canals each end in a swelling called
An ampulla
Where the hair cells are located
In the semicircular canals how are signals sent to brain when the head rotates?
When the head rotates. Endolymph in the semicircular canals resist this motion, bends underlying hair cells, sending signals to brain
Where does most electrical stimuli from sound go to through the vestibulocochlear nerve?
The brainstem, where it ascends to the medial geniculate nucleus of the thalamus
From the medial geniculate nucleus where can some info be sent? (For sound)
To the superior olive, which localized sound
Also the inferior colliculus, involved in the startle reflex
What are stereocilia?
The long tufts on top of the hair cells surface, play a crucial role in the process of hearing by converting sound vibrations into electrical signals that the brain can interpret
As vibrations reach the basilar membrane what happens to the stereocilia?
The stereocilia begin to sway, swaying causes the opening of ion channels, causing receptor potential
Certain hair cells are directly connected to tectorial membrane, what are they involved in?
The amplifying of incoming sound
What is place theory?
The location of a hair cell on the basilar membrane determines the perception of pitch when the hair cell is vibrated
Where would high frequency and low frequency vibrations occur?
High frequency vibrations would occur at the basilar membrane very close to oval window
Low frequency vibrations would occur at apex, away from oval window
The cochlea is tonotopically organized, what does this mean?
Means that which hair cells are vibrating gives the brain an indication of the pitch of sound
What is the only sense that does not pass through the thalamus?
Smell
Where are olfactory chemoreceptors located?
In the olfactory epithelium (upper part of nasal cavity)
What are pheromones
Chemicals secreted by one animal, once bonded with chemoreceptors, compel or urge another animal to behave a certain way
Have debatable effects on humans
Olfactory pathway
Odor molecules inhaled into nasal passages — contact the olfactory nerves in the olfactory epithelium — receptors cells are activated, sending signals to olfactory bulb — signals relayed via the olfactory tract to higher regions of brain, including limbic system
Taste is detected by what receptors?
Chemoreceptors
What are the 5 basic tastes
Sweet, sour, salty, bitter, umami (savory)
What is flavor?
The complex interplay between smell and taste, can be affected by nonchemical stimuli like texture and the individuals mood
Saltiness is a reaction to…
Alkali metals, generally triggered by the sodium found in table salt
Sourness is a reaction to…
Acid
Receptors for taste are groups of cells called what? Where are they located
Taste buds, located in little bumps on the tongue called papillae
Gustatory pathway
Taste buds — brainstem — ascends to the taste center in the thalamus — higher order brain regions
Somatosensation is often reduced to touch, but has what 4 modalities?
Pressure, vibration, temperature, pain
Pacinian corpuscles respond to
Deep pressure and vibration
Meisner’s corpuscles respond to
Light touch
Merkel cells (discs) respond to
Deep pressure and texture
Ruffini endings respond to
Stretch
Free nerve endings respond to
Pain and temperature
For somatosensation where does the signals from receptors go?
It eventually gets to the somatosensory cortex in the parietal lobe
What is a 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, below threshold = felt as same stimuli
What does the size of two point thresholds depend on?
The density of nerves in the particular area of skin being tested
Temperature is judged relative to physiological zero; what is physiological zero?
Normal temperature of skin (86•-97•)
Objects feel warmer above, colder below physiological zero
What is the gate theory of pain?
It proposed that there is a special “gating” mechanism to turning pain signals on or off, affecting whether or not we perceive pain; signals can either be processed to accentuate the perceived pain or attenuate it at the spinal cord itself
What is smell, and taste sensitive to
Smell is sensitive to volatile or aerosolized compounds while taste is sensitive to dissolved compounds
Kinesthetic sense is also called
Proprioception
What is proprioception/kinesthetic sense?
Ability to tell where one’s body is in space
What are the receptors for proprioception and where are they mostly found?
Proprioceptors, mostly found in muscle, and joints
What is bottom-up processing?
Object recognition by parallel processing and feature detection
Brain takes the individual sensory stimuli and combines them together to create a cohesive image before determining what the object is
-Takes longer but less prone to mistakes
What is top-down processing?
Driven by memories and expectations that allow the brain to recognize the whole object without analyzing little details to put together
-Faster but more prone to mistakes
When is deja vu evoked?
When we have recognition without an obvious reason
What is perceptual organization?
The ability to create a complete picture or idea by combining top-down and bottom-up processing with all of the other sensory clues gathered from an object
What is relative size?
Idea that objects appear larger the closer they are
What is interposition?
When 2 objects overlap, the one in front is closer
What is linear perspective?
The convergence of parallel lines at a distance; the greater the convergence, the further the distance
What is motion parallax?
The perception that objects closer to us seem to move faster when we change our field of vision (look at something else)
What is convergence referring to a secondary binocular cue?
The brain detecting the angle between the 2 eyes required to bring and object into focus
Difference in the degree of convergence is used to perceive distance
What is constancy referring to vision?
Our ability to perceive that certain characteristics of objects remain the same, despite changes in the environment
What are Gestalt principles?
A set of general rules that account for the fact that the brain tends to view incomplete stimuli in organized, patterned ways
What is the law of proximity?
Elements close to one another tend to be perceived as a unit
What is the law of similarity?
Objects that are similar tend to be grouped together
What is the law of good continuation?
Elements that appear to follow in the same pathway tend to be grouped together
What is subjective contours?
The way we perceive contours, therefore, shapes that are not actually present in the stimulus
What is the law of closure?
When a space is enclosed by a contour, the space tends to be perceived as a complete figure
The gestalt principles are governed by?
The law of Pragnanz
What does the law of pragnanz say?
That perceptual organization will always be as regular, simple, and symmetrical as possible
