Ch 2 - Sensation and Perception Flashcards
What is sensation?
- the conversion, or transduction, of physical, electromagnetic, auditory, and other information from our internal and external environment to electric signals in the nervous system
- performed by receptors in the PNS, which forward the stimuli to the CNS in the form of action potentials and neurotransmitters
- raw signal that is unfiltered/unprocessed until it enters the CNS
What is Perception?
- the processing of this information to make sense of its significance
What are sensory receptors?
- neurons that respond to stimuli and trigger electrical signals
What is the difference between distal and proximal stimuli?
- distal: originate outside the body
- proximal: directly interact with and affect the sensory receptors, and inform the observer about the presence of distal stimuli
What is the study of psychophysics?
the relationship between the physical nature of stimuli and the sensations and perceptions they evoke
What are ganglia?
- collections of neuron cell bodies found outside the CNS
- once transduction occurs, the electrochemical energy is sent along neural pathways to various projections areas in the brain, which further analyze the sensory input
What are the 7 most common sensory receptors?
- photoreceptors: respond to electromagnetic waves int the visible spectrum (sight)
- hair cells: respond to movement of fluid in the inner war structures (hearing, rotational/linear acceleration)
- nociceptors: respond to painful or noxious stimuli (somatosensation)
- thermoreceptors: respond to changes in temperature (theromsensation)
- osmoreceptors: respond to the osmolarity of the blood (water homeostasis)
- olfactory receptors: respond to the volatile compounds (smell)
- taste receptors: respond to dissolved compounds (taste)
What is a threshold?
- the minimum amount of a stimulus that renders a difference in perception
What is the absolute threshold?
- the minimum stimulus energy that is needed to activate a sensory system
- threshold in sensation, not in perception
- how bright, loud, or intense a stimulus must be before it is sensed
What is the threshold of conscious perception?
- when sensory systems send signals to the CNS without a person perceiving them; may be because the stimulus is too subtle to demand our attention or may last for too brief of a duration for the brain to fully process the information
What is the difference threshold?
- the minimum difference in magnitude between 2 stimuli before one can perceive this difference
- just noticeable
What is Weber’s law?
- there is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
Signal detection theory?
- focuses on the changes in our perception of the same stimuli depending on bother internal (psychological) and external (environmental) context
Response bias?
the tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors
What is the difference between catch and noise trials?
- catch: signal is presented
- noise: signal is not presented
What are the 4 possible outcomes of using catch/noise trials in response bias?
- hits: the subject correctly perceives the signal
- misses: subject fails to perceive a given signal
- false alarms: subject seems to perceive a signal when none was given
- correct negatives: subject correctly identifies that no signal was given
How does sensory adaptation affect a different threshold?
- usually raises the difference threshold for a sensory response
- as one becomes used to small fluctuations in the stimulus, the difference in stimulus required to evoke a response must be larger
What is the pathway for a stimulus to reach conscious perception?
sensory receptor –> afferent neurons –> sensory ganglia –> spinal cord –> brain
Sclera?
- provides structural support
- white part of the eye
What vessels supply the eye with nutrients?
- choroidal: a complex intermingling of blood vessels between the sclera and retina
- retinal:
Retina?
- innermost layer of eye
- convert incoming photons of light to electrical signals
- detects images
Cornea?
- clear, dome-like window in the front of the eye
- gathers and focuses the incoming light
What is the pupil and how is it divided?
- allows passage of light from anterior to posterior chamber
- anterior chamber: lies in front of the iris
- posterior chamber: between the iris and the lens
Iris?
- the colored part of the eye
- controls size of pupil
What 2 muscles compose the iris?
- dilator pupillae: opens the pupil under sympathetic stimulation
- constrictor pupillae: constricts the pupil under the parasympathetic stimulation
Ciliary body?
- produces the aqueous humor that bathes the front part of the eye before draining into the canal of Schlemm
- accommodation of the lens
Lens?
- lie right behind the iris
- help control the refraction of incoming light to focus it on the retina
What happens with the ciliary muscle contracts?
- under parasympathetic control
- it pulls on the suspensory ligaments and changes the shape of the lens (accomodation)
Vitresous?
- behind the lens
- a transparent gel that supports the retina
What is the duplicity theory of vision (duplexity)?
states that the retina contains 2 kinds of photoreceptors: those specialized for light and dark detection and those specialized for color detection
Cones?
- used for color vision and to sense fine detail
- most effective in bright light and come in 3 forms, named for the wavelength of light they best absorb
Rods?
- more functional in reduced illumination and only allow sensation of light and dark because they all contain rhodopsin
- low sensitivity to detains and are not involved in color vision, but permit night vision
- more rods than cones in eye
Macula?
- central section of the retina
- high concentration of cones
- center most point (fovea) contains only cones
How do rods and cones connect with the optic nerve?
- with bipolar cells that highlight gradients between adjacent rods and cones
- bipolar cells synapse with ganglion cells, which group together to form the optic nerve
How do amacrine and horizontal cells work together in the eye?
- receive input from multiple retinal cells in the same area before the information is passed on to ganglion cells
- can accentuate slight differences between the visual information in each bipolar cell
Visual pathways?
- refer to both the physical anatomical connections between the eyes and the brain and the flow of visual information along these connections
Optic chiasm?
- where the first significant event occurs once the signal travels through the optic nerve to the brain
- here, fibers from the nasal half of each retina cross paths and carry the temporal visual field from each eye
Where does the information go once through the optic chaism?
- lateral geniculate nucleus of the thalamus, through radiation in the temporal/parietal lobes to the visual cortex in the occipital lobe
Parallel processing?
- the ability to simultaneously analyze and combine information regarding color, shape, and motion and to integrate this information to create a cohesive image of the world
- calls on memory systems to compare visual stimulus to past experiences to help determine the object’s identity
Feature detection?
- our visual pathways contain cells specialized in detection of color, shape, or motion
How is shape detected by the eyes?
- by parvocellular cells, which have very high color spatial resolution (they permit us to see very fine detail when thoroughly examining an object)
- can only work with stationary or slow-moving objects because they have very low temporal resolution
How is motion detected by eyes?
- by magnocellular cells because they have high temporal resolution, but low spatial resolution
List the sructures in the visual pathway, from where the light enters the cornea to the visual projection areas in the brain.
cornea –> pupil –> lens –> vitreous –> retina (rods/cones –> bipolar cells –> ganglion cells) –> optic nerve –> optic chiasm –> optic tract –> LGN –> radiation through parieta/temporal lobes –> visual cortex (occipital lobe)
What are the 3 parts of the ear?
- a sound wave first reaches the cartilaginous outside part of the ear, pinnae (auricle)
- pinnae channel sound waves into the external auditory canal (middle), which directs the sound waves to the tympanic membrane (inner - eardrum)
Intensity?
corresponds to an increased amplitude of vibration
What are the 3 smallest bones in the body?
all in the middle ear
- ossicles: help transmit and amplify the vibrations from the TM to the inner ear
- malleus: affixed to the TM, acts on the incus which acts on the stapes
Eustachian tueb?
- connects the middle ear to the nasal cavity
- helps equalize pressure between the middle ear and the environment
Where does the inner ear sit and what does it contain?
- sits within the bony labyrinth
- contains the cochlea, vestibule, and semicircular canals
Cochlea?
- a spiral shaped organ divided into 3 parts called scalae
- middle scala houses the actual hearing apparatus (organ of Corti) which rests on a thin flexible membrane (basilar membrane)
- other 2 scalae, filled with perilymph, surround the hearing apparatus and are continuous with the oval and round windows of cochlea
What converts the physical stimulus into electrical signals in the organ of Corti?
hair cells
Vestibule?
- the portio of the bony labyrinth that contains the utricle and saccule (sensitive to linear acceleration)
Semicircular canals?
- sensitive to rotational acceleration
- arranged perpendicularly to each other and each ends in a swelling ampulla where hair cells are located
Medial geniculate nucleus (MGN)?
for music
What is the auditory pathway?
pinna –> external auditory canal –> TM –> malleus –> incus –> stapes –> oval window –> perilymph in cochlea –> basilar membrane –> hair cells –> vestibularcochlear nerve –> brainstem –> MGN –> auditory cortex (temporal)
Hair cells function?
- they sway back and forth as vibrations reach the basilar membrane underlying the organ of Corti
- swaying opens ion channels which cause receptor potential
What is the place theory?
- states that the location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated
How is the cochlea tonotopically organized?
- which hair cells are vibrating gives the brain an indication of the pitch of the sound
- high pitch = base of cochlea vibration
- low pitch = apex of cochlea vibration
Olfactory chemoreceptors?
- olfactory nerves
- located in the epithelium in the upper part of the nasal cavity
- chemical stimuli must bind to their respective chemoreceptors to causes a signal
Pheromones?
- debatable effects on humans, but play an enormous role in many animal social, foraging, and sexual behavior
What is the olfactory pathway?
nostril –> nasal cavity –> olfactory nerves –> olfactory bulb –> olfactory tract –> brain (limbic system)
How is taste detected?
- by chemoreceptors, which are sensitive to dissolved compounds
Taste buds?
- receptors for taste
- found in little bumps on the tongue (papillae)
What is the taste pathway?
- taste information travels from taste buds to the brainstem, and then ascends to the taste center in the thalamus before traveling to higher-order brain regions
What are the 5 receptors of Somatosensation?
- pacinian corpuscles: respond to deep pressure and vibration
- meissner 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
Two-point threshold?
- the minimum distance necessary between 2 points of stimulation on the skin such that the points will be felt as 2 distinct stimuli
Nocireceptors?
- pain perception
- can result from signals sent from a variety of sensory receptors
- relies on thresholds, which may vary from person to person
Get theory of pain?
- there is a special “gating” mechanism that can turn pain signals on or off, affecting whether or not we perceive pain
Kinesthetic sense?
- proprioception
- the ability to tell where one’s body is in space
What is the difference between the types of chemicals smell and taste can sense?
- smell is sensitive to volatile and aerosolized compounds
- taste sensitive to dissolved compounds
What are the 4 main modalities of somatosensation?
pressure, vibration, pain, temperature
Bottom-up processing?
- data-driven
- refers to object recognition by parallel processing and feature detection
- the brain takes the individual sensory stimuli and combines them together to create a cohesive image before determining what the object is
Top-down processing?
- conceptually driven
- driven by memories and expectations that allow the brain to recognize the whole object and then recognize the components based on these expectations
- allows us to quickly recognize objects without needed to analyse their specific parts
Perceptual organization?
- refers to the ability to use top down and bottom up processing in tandem with all of the other sensory clues about an object to create a complete picture or idea
Depth perception?
- can rely on both monocular (relative size of object, partial obscuring of one object by another, convergence of parallel lines at a distance, position of an object in visual field, lighting/shadowing) and binocular cues (slight differences in images projected on the 2 retinas and the angle required between the 2 eyes to bring an object into focus
How is the form of an object usually determined?
- through parallel processing and feature detection and the motion of an object is perceived through magnocellular cells
Constancy?
- the idea that we perceive certain characteristics of objects to remain the same, despite differences in the environment
Gestalt principles?
these are ways for the brain to infer missing parts of the picture when a picture is incomplete
What are the 6 elements of Gestalt principles?
- proximity: elements close to one another tend to be perceived as a unit
- similarity: objects that are similar tend to be grouped together
- good continuation: elements that appear to follow in the same pathway tend to be grouped together
- subjective contours: perceiving contours, shapes that are not actually present in the stimulus
- closure: when a space is enclosed by a contour it tends to be perceived as a complete figure
- Pragnanz: perceptual organization will always be as regular, simple, and symmetric as possible
