Week 7 Flashcards
Sensation
The physical process during which our sensory organs-those involved with hearing and taste, for example-respond to external stimuli. our sense organs are engaging in transduction, the conversion of one form of energy into another
Perception
After out brain receives the electrical signals, we make sense of all this stimulation and begin to appreciate the complex world around us
Absolute threshold
The smallest amount of stimulation needed for detection by a sense
signal detection
method for studying the ability to correctly identify sensory stimuli
How do we measure absolute thresholds
using a method called signal detection. Involves presenting stimuli of varying intensities to a research participant in order to determine the level at which someone can reliably detect stimulation in a given sense
differential threshold/ just noticeable difference
The smallest difference needed in order to differentiate two stimuli
Weber’s law
States that just noticeable different is proportional to the magnitude of the initial stimulus
How does experience influence hoe our brain processes things
stimuli we’ve experienced in our past will influence how we process new ones.
Top-down processing
Experience influencing the perception of stimuli
Why don’t we feel the weight of our clothing
When we experience a sensory stimulus that doesn’t change, we stop paying attention to it.
Bottom up processing
Building up to perceptual experience from individual pieces
Sensory adaptation
Decrease in sensitivity of a receptor to a stimulus after constant stimulation
How vision works
▪ When we see an object, we are actually seeing light bounce off that object and into our eye
▪ Light enters the eye through the pupil, a tiny opening behind the cornea
▪ The pupil regulates the amount of light entering the eye by contracting in bright light and dilating in dimmer light
▪ Once past the pupil, light passes through the lens, which focuses an image on a thin layer of cells in the back of the eye, called the retina
▪ Because we have two eyes in different locations, the image focused on each retina is from a slightly different angle (binocular disparity), providing us with our perception of 3D space (binocular vision)
Light is transduced, or converted into electrical signals in the retina by specialized cells called photoreceptors
▪ Electrical signal is sent through a layer of cells in the retina, eventually travelling down the optic nerve
* After passing through the thalamus, this signal makes it to the primary visual cortex, where information about light orientation and movement begin to come together
* Information is sent to a variety of different areas of the cortex for more complex processing
two types of photoreceptors in the retina
rods and cones
Rods
primarily responsible for our ability to see in dim light conditions, such as during the night
Cones
provide us with the ability to see colour and fine detail when the light is brighter
how are rods and cones different
differ in their distribution across the retina, with the highest concentration of cones found in the fovea (central region of focus), and rods dominating the periphery
Retina
Cell layer in the back of the eye containing photoreceptors
Binocular disparity
Difference is images processed by left and right eyes
Binocular vision
Our ability to perceive 3D and depth because of the difference between the images on each of our retinas
Primary visual cortex
Area of the cortex involved in processing visual stimuli
Ventral pathway
Pathway of visual processing. The “What pathway
dorsal pathway
Pathway of visual processing. The “where” pathway
Night vision
takes around 10 minutes to turn on, a process called dark adaption. Because our rods become bleached in normal light conditions and require time to recover
dark adaptation
Adjustment of eye to low levels of light
light adaptation
Adjustment of eye to high levels of light. Happens almost instantly compared to dark adaption
colour vision
Cones allow us to see details in normal light conditions, as well as colour. Cones respond preferentially, not exclusively, for red, green and blue
Trichromatic theory
theory proposing colour vision as influenced by three different cones responding preferentially to red, green and blue. Does not explain the odd effect that occurs when we look at a white wall after staring at a picture for 30 seconds
Opponent process theory
theory proposing colour vision as influenced by cells responsive to pairs of colours
Sound waves
changes in air pressure. The physical stimulus for audition
amplitude/ intensity of a sound wave
cods for the loudness of a stimulus; higher amplitude sound waves result in louder sounds
pitch of a stimulus
coded in the frequency of a sound wave
timbre
quality of a sound
How we sense sound waves from our environment
Sound waves are funneled by your pinna into your auditory canal. Sound waves eventually reach a thin, stretched membrane called the tympanic membrane, which vibrates against the three smallest bones in the body- the malleus, the incus, and the stapes- collectively called the ossicles.
Both the tympanic membrane and the ossicles amplify the sound waves before they enter the fluid-filled cochlea, a snail-shell like bone structure containing auditory hair cells arranged on the basilar membrane
After being processed by auditory hair cells, electrical nerves are sent through the cochlear nerve to the thalamus, and then the primary auditory cortex of the temporal lobe
vestibular system
Parts of the inner ear involved in balance. comprised of three semicircular canals-fluid filled bone structures containing cells that respond to changes in the head’s orientation in space
How are we able to maintain our gaze on an object while we are in motion?
Information from the vestibular system is sent through the vestibular nerve to muscles involved in the movement of our eyes, neck, and other parts of our body
Somatosensation
Ability to sense touch, pain, and temperature
Tactile sensation
associated with texture, transduced by special receptors in the skin
mechanoreceptors
Mechanical sensory receptors in the skin that response to tactile stimulation. Allow for the conversion of one kind of energy the brain can understand
how tactile sensation works
Information is sent through the thalamus to the primary somatosensory cortex for further processing. This region of the cortex is organized in a somatotopic map, where different regions are sized based on the sensitivity of specific parts on the opposite side of the body. Various areas of the skin, such as lips and fingertips, are more sensitive than others, such as shoulders or ankles
noiception
Our ability to sense pain
Pain
An unpleasant sensation, appears to not have obvious value. Perception of pain is our body’s way of sending us a signal that something is wrong and needs attention
Phantom limbs
Sensations such as itching seemingly coming from the missing limb
A phantom limb can also involve phantom limb pain, sometimes described as the muscles of the missing limb uncomfortably clenching
Evidence to support that the damaged nerved from the amputation site are still sending information to the brain and that the brain is reacting to this information
Chemical senses
Our ability to process the environmental stimuli of smell and taste
Olfaction
Ability to process olfactory stimuli. Also called smell
Gustation
Ability to process gustatory stimuli. Also called taste
How olfaction works
Receptors involved in our perception of both smell and taste bind directly with the stimuli they transduce
Odorants in our environment, very often mixtures of them, bind with olfactory receptors found in the olfactory epithelium
The binding of odorants to receptors is through to be similar to how a lock and key operates, with different odorants binding to different specialized receptors based on their shape
Olfactory receptors send projections to the brain through the cribriform plate of the skull, head trauma has the potential to cause anosmia, due to the severing of these connections
Shape theory of olfaction
Theory proposing that odorants of different size and shape correspond to different smells
Anosmia
loss of ability to smell
Gustation
Receptors found in the taste buds of the tongue, called taste receptor cells
Located in small divots around the bumps on your tongue
Responds to chemicals from the outside environment, except these chemicals, called tastants, are contained in the foods we eat
Binding of these chemicals with taste receptor cells results in our perception of the five basic tastes: sweet, sour, bitter, salty, and umami (savory)-although some scientists argue that there are more
Taste receptor cells
receptors that transduce gustatory information
tastants
Chemicals transduced by taste receptor cells
multimodal perception
The effects that concurrent stimulation in more than one sensory modality has on the perception of evetns and objects in the world
Superadditive effect of multi sensory integration
The finding that responses to multimodal stimuli are typically greater than the sum of the independent responses to each unimodal component if it were presented on its own
Principle of Inverse effectiveness
The finding that, in general, for a multimodal stimulus, if the response for each unimodal component is weak, then the opportunity for multisensory enhancement is very large. However, if one component-by itself- is sufficient to evoke a strong response, then the effect on the response gained by simultaneously processing the other components of the stimulus will be relatively small
Mcgurk effect
Visuals override what we hear
loudness
Most direct physical correlate of loudness is sound intensity measured close to the eardrum.
Many other factors also influence the loudness of a sound, including its frequency content, its duration, and the context in which is it presented
Pitch
Plays a crucial role is acoustic communication
Variations over time provide the basis of melody for most types of music; pitch contours in speech provide us with important prosodic information in non-tone languages, such as English, and help define the meaning of words in tone languages, such as Mandarin Chinese
Most common pitch-evoking sounds are known as harmonic complex tones
Timbre
Refers to the quality of sound, and is often described using words such as bright, dull, harsh, and hollow
Includes anything that allows us to distinguish two sounds that have the same loudness, pitch, and duration. Important aspect includes the temporal envelope of the sound, especially how it begins and ends
Pinna
The filtering produced by the pinnae helps us localize sounds and resolve potential front-back and up-down confusions
The folds and bumps of the pinna produce distinct peaks and dips in the frequency response that depend on the location of the sound source
Due to the small size of the pinna, these kinds of acoustic cues are only found is basically unchanged whether it comes from above, in front, or below
Ear canal (auditory meatus) and the tympanic membrane
Thin, stretched membrane in the middle ear that vibrates in response to sound. Also called the eardrum
Inner ear
Includes the cochlea, encased int eh temporal bone of the skull, in which the mechanical vibrations of sound are transduced into neural signals that are processed by the brain
Middle ear
Consists of an air-filled cavity, which contains the middle-ear bones, known as the incus, malleus, and stapes, or anvil, hammer, and stirrup, because of their respective shapes
Distinction of being the smallest bones in the body
Primary function is to transmit the vibrations form the tympanic membrane to the oval window of the cochlea and, via a form of lever action, to better match the impendence of the air surrounding the tympanic membrane with that of the fluid within the cochlea
cohclea
a spiral shaped structure that is filled with fluid
basilar membrane
vibrates in response to the pressure differences produced by vibrations of the oval window
Organ of Corti
runs the entire length of the basilar membrane from the base to the apex
Organ of Corti includes three rows of outer hair cells and one row of inner hair cells
The hair cells sense the vibrations by way of their tiny hairs, or stereocilia
Outer hair cells seem to function to mechanically amplify the sound-induced vibrations, whereas the inner hair cells form synapses with the auditory nerve and transduce those vibrations into action potentials, or neural spikes, which are transmitted along the auditory nerve to higher centers of the auditory pathways
Ways in which we are able to locate sounds in space
We have a 360 degree field of hearing
Our auditory acuity is, at least an order of magnitude poorer than vision in locating an object in space
Our auditory localization abilities are most useful in alerting us and allowing us to orient towards sources, with our visual sense generally providing the finer-grained analysis
Our ability to locate sound sources in space is an impressive feat of neural computation
Interaural time differences
differences between the two ears
Interaural level differences
the difference in sound pressure level between the left and right ear
Describe various acoustic cues that contribute to our ability to perceptually segregate simultaneously riving sounds
Auditory system is able to break down, or decompose, complex waveforms and allow us to make sense of our acoustic environment by forming separate auditory “objects” or “streams”, which we can follow as the sounds unfold over time
Sounds that are in close proximity, in time or frequency, tend to be grouped together
Sounds that begin and end at the same time tend to form single auditory object
Spatial location is not always a strong or reliable grouping cue, perhaps because the location from individual frequency components if often ambiguous due to the effects of reverberation
interoception
The sense of physiological state of the body. Hunger, thirst, temperature, pain, and other sensations relevant to homeostasis.
exeroception
The sense of the external world, of all stimulation originating from outside our own bodies
Cutaneous senses
The senses of the skin: tactile, thermal, pruritic (itchy), painful, and pleasant
noiciception
our ability to sense pain
Transduction
A process in which physical energy converts into neural energy
mechanoreceptors
responds to mechanical stimuli, such as stroking, stretching, or vibration of the skin. High threshold for activation
Thermoreceptors
responds to hot or cold temperatures
Chemoreceptors
responds to certain types of chemicals, either applied externally or released within the skin
nociceptors
receptors that fire specifically to potentially tissue damaging stimuli. Most are subtypes of either chemoreceptors or mechanoreceptors
A-fibers
Fast conducting sensory nerves with myelinated axons. Larger diameter and thicker myelin sheaths increases conduction speed
C-pain/ A delta fibers
convey noxious, thermal, and heat signals
How pain is signalled
Sharp pain is signalled via fast conducting A-fibers, which project to the somatosensory cortex. This part of the cortex is somatopically organized-sensory signals are represented along to where in the body they stem from
The unpleasant ache after a sharp pain is a simultaneous signal sent from the nociceptors in your foot via thin C-pain or A delta fibers to the insular cortex and other brain regions involved in processing of emotion and interoception
Social touch hypothesis
propose that C-tactile fibers form a system for touch perception that supports social bonding
what does the discovery of C-tactile system suggest
That touch is organized in a similar way to pain; fast conducting A fibres contribute to sensory discriminatory aspects, while thin C-fibers contribute to affective-motivational aspects
Motivation-decision model
The brian automatically and continuously evaluates the pros and cons of any situation-weighting impending threats and available rewards.
The brain’s descending pain modulatory system
A top down system involving several parts of the brain and brainstem, which inhibits nociceptive signalling so that the more important actions can be attended to
How the promise of a reward can be enough to relive pain
Expecting pain relief from a medical treatment contributes to the placebo effect- where pain relief is due at least partly to your brain’s descending modulation in circuit, and such relief depends on the brain’s own opioid system. Our brain can modulate the perception of how unpleasant pain is, while still retaining the ability to experience the intensity of sensation
allodynia
Pain due to a stimulus that does not normally provoke pain, e.g, when a light, stoking touch feels painful
noxious stimuli
a stimulus that is damaging or threatens damage to normal tissues
Chronic pain
Persistent or recurrent pain, beyond usual course of acute illness or injury; sometimes present without observable tissue damage or clear cause
Annual economic cost associated with chronic pain
560-635 billiion dollars
why is it difficult to treat chronic pain
Chronic pain conditions are highly diverse, and they can involve changes on peripheral, spinal, central, and psychological levels. The mechanisms are far from fully understood, and developing appropriate treatment remains a huge challenge for pain researchers.
Sensitization
Occurs when the response to a stimulus increases with exposure
