Week 7: Introduction to Sensation and Perception Flashcards
Sensation and Perception, Hearing, Touch and Pain,
Sensation
The physical processing of environmental stimuli by the sense organs
During sensation, our sense organs are engaging in TRANSDUCTION; After our brain receives the electrical signals, we make sense of all this stimulation and begin to appreciate the complex world around us (PERCEPTION)
Transduction
A process in which physical energy converts into neural energy
Perception
The psychological process of interpreting sensory information
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 (the way we measure absolute thresholds)
Method of limits - effort to determine the point, or threshold, at which a person begins to hear a stimulus
Ascending/Descending trials
Hit - correct identification
Miss - incorrect identification
Additionally, indicating that a sound was heard when one wasn’t played is called a FALSE ALARM, and correctly identifying when a sound wasn’t played is a CORRECT REJECTION.
Differential Threshold
The smallest difference needed in order to differentiate two stimuli
Just Noticeable Difference (JND)
The smallest differenced needed in order to differentiate two stimuli
Weber’s Law
States that just noticeable difference is proportional to the magnitude of the initial stimulus
Bottom-up Processing
Building up to perceptual experience from individual pieces
Top-down Processing
Experience influencing the perception of stimuli
Sensory Adaptation
Decrease in sensitivity of a receptor to a stimulus after constant stimulation
Retina
Cell layer in the back of the eye containing photoreceptors
Once past the pupil, light passed through the lens, which focuses an image on a thin layer of cells in the back of the eye (the retina)
It is in the retina that light is transduced, or converted into electrical signals, by specialized cells called photoreceptors - RODS and CONES
Binocular Disparity
Difference in images processed by the 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
Agnosia
Loss of the ability to perceive stimuli
Ventral Pathway
Pathway of visual processing; the “What” pathway (processing visual recognition)
Dorsal Pathway
Pathway of visual processing; the “where” pathway (processing location and movement)
Dark Adaptation
Adjustment of eye to low levels of light
Light Adaptation
Adjustment of eye to high levels of light
Opponent-Process-Theory
Theory proposing colour vision as influenced by cells responsive to pairs of colours
Colour deficient vision can result from issues with the cones/retinal ganglion cells involved in colour vision
Someone stares at a yellow piece of paper for 30 seconds, and then he quickly looks at a white wall. The blue afterimage he sees supports OPT
The Trichromatic Theory
Theory proposing colour vision as influenced by three different cones responding preferentially to red, green, and blue
Sound Waves
Changes in air; physical stimulus for audition
the AMPLITUDE of a sound wave codes for the loudness of a stimulus (higher amplitude sound waves result in louder sounds)
the PITCH of a stimulus is coded in the FREQUENCY of the sound wave (higher frequency sounds are higher pitched)
allows us to tell difference between bright and dull sounds as well as natural and synthesized instruments
Audition
Ability to process auditory stimuli; also called hearing
Pinna
Outermost portion the ear
Auditory Canal
Tube running from the outer ear to the middle ear
Tympanic Membrane
Thin, stretched membrane in the middle ear that vibrates in response to sound; also called the eardrum
Ossicles
A collection of three small bones in the middle ear that vibrate against the tympanic membrane
Cochlea
Spiral bone structure in the inner ear containing auditory hair cells
Primary Auditory Cortex
Area of the cortex involved in processing auditory stimuli
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) - info from vestibular system sent through vestibular nerve to muscles involved in movement of parts of body
Info allows us to maintain our gaze on an object while we are in motion - disturbances in the system can result in issues w balance including vertigo
Somatosensation
Ability to sense touch, pain and temperature
Mechanoreceptors
Mechanical sensory receptors in the skin that respond to tactile stimulation - allow for conversion of one kind of energy into a form the brain can understand
Primary Somatosensory Cortex
A strip of cerebral tissue just behind the central sulcus engaged in sensory reception of bodily sensations
Somatotopic Map
Organization of the primary somatosensory cortex maintaining a representation of the arrangement of the body
Put simply, various areas of the skin, such as lips/fingertips, are more sensitive than others, such as shoulders/ankles
Nociception
Our ability to sense pain
Phantom Limbs
The perception that a missing limb still exists - after amputations
Phantom Limb Pain
Pain in a limb that no longer exists - there’s evidence to support that the damaged nerves from the amputation site are still sending info to the brain/that the brain is reacting to the info
Chemical Senses
Our ability to process the environmental stimuli of smell/taste
Both olfaction/gustation require the transduction of chemical stimuli into electrical potentials
Olfaction (smell)
Ability to process olfactory stimuli; also called smell
Gustation (taste)
Ability to process gustatory stimuli; also called taste
Odorants
Chemicals transduced by olfactory receptors
Olfactory Epithelium
Organ containing olfactory receptors
Shape Theory of Olfaction
Theory proposing that odorants of different size/shape correspond to different smells - not universally accepted
Anosmia
Loss of the ability to smell - head trauma has potential to cause it due to severing of connections in the brain (cribiform plate)
Taste Receptor Cells
Receptors that transduce gustatory information; found in the taste buds of the tongue
Tastants
Chemicals transduced by taste receptors cells; contained in the food we eat
Binding of these chemicals w taste receptor cells result in our perception of the five basic tastes: sweet, sour, bitter, salty, and umami (savoury)
Flavour
The combo of smell and taste
Mulitmodal Perception
The effects that concurrent stimulation in more than one sensory modality has on the perception of events and objects in the world - basically info from one sense has the potential to influence how we perceive info from another
Superadditive effect of multisensory integration
The finding that responses to multimodial stimuli are typically greater than the sum of the independent responses to each unimodial component if it were presented on its own - basically we respond more strongly to mulitmodal stimuli compared to the sum of each single modality together
Can explain how you’re still able to understand what friends are saying to you at a loud concert, as long as you can get visual cues from watching them speak
Principle of Inverse Effectiveness
States you are LESS likely to benefit from additional cues from other modalities if the initial unimodial stimulus is strong enough
The finding that, in general, for a multimodal stimulus, if the response to each unimodal component (on its own) 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
If it’s quiet in a cafe, you benefit more just from hearing rather than also looking for other cues like watching them speak
Perceptional Attributes of Sound
Ways to describe a sound - Loudness, pitch, and timbre
Loudness
The most direct physical correlate of loudness is sound intensity (or sound pressure) measured close to the eardrum; many other factors influence the loudness (frequency content, its duration, context in which it presented)
Pitch
Plays a crucial role in acoustic communication; pitch variations over time provide the basis of melody for most types of music; pitch contours in speech provide us with important prosodic info in non-tone languages (english) and help define the meaning of words in tone languages (mandarin)
Pitch is essentially the perceptual correlate of waveform periodicity, or repetition rate: The faster a waveform repeats over time, the higher is its perceived pitch.
Timbre
Refers to the quality of sound, and is often described using words such as bright, dull, harsh, and hollow; technically timbre includes anything that allows us to distinguish two sounds that have the same loudness, pitch, and duration
Ex. a violin and piano playing same note sound VERY different, based on sound quality (timbre)
Important aspect of timbre is the SPECTRAL CONTENT of a sound - sounds w more high frequency energy tend to sound brighter/tinnier/harsher than sounds w more low frequency content that are deep/rich/dull
Temporal envelope - outline of the sound (especially how it begins/ends)
In general, the overall spectral content and the temporal envelope can provide a good first approximation to any sound, but subtle changes in the spectrum over time (or spectro-temporal variations) are crucial in creating plausible imitations of natural musical instruments
Overview of Auditory System
Outer Ear: consists of PINNA, ear canal, TYMPANNIC MEMBRANE
The primary function of the outer ear is to collect and funnel sound waves toward the eardrum (tympanic membrane). The pinna (the visible part of the ear) helps gather sound and can also assist in determining the direction from which the sound is coming. Additionally, the ear canal amplifies certain frequencies of sound, especially those important for speech. Together, these parts help transmit sound efficiently to the middle ear for further processing.
Middle Ear: consists of an air-filled cavity, which contains the middle-ear bones, known as the incus, malleus, and stapes (anvil, hammer, sitrrup) - They act like little levers to help the sound move smoothly from the air in the ear to the fluid in the inner ear, making it easier for us to hear.
Inner Ear: includes cochlea - in which the mechanical vibrations of sound are transduced into neural signals that are processed by the brain
Frequency Analysis
One of the most important principles of hearing - frequency analysis
The cochlea is like a tool that separates sound into different parts, similar to how a prism splits light into colours. When a sound comes in, the cochlea breaks it down into its different frequencies (or pitches). Low-pitched sounds make the top of the cochlea vibrate the most, while high-pitched sounds make the base vibrate more. This helps the brain understand the different parts of the sound, and this organization continues all the way from the ear to the brain’s hearing center.
This process of separating sounds into different frequencies is what lets us hear more than one sound at a time. In addition to this frequency separation, the timing of signals sent through the auditory nerve also plays a role. The ear can detect small differences in when sound reaches each ear (a process called “phase locking”), which helps us figure out where the sound is coming from.
Masking
Masking is the process by which the presence of one sound makes another sound more difficult to hear.
We all encounter masking in our everyday lives, when we fail to hear the phone ring while we are taking a shower, or when we struggle to follow a conversation in a noisy restaurant.
In general, a MORE intense sound will mask a LESS intense sound, provided certain conditions are met. The most important condition is that the frequency content of the sounds overlap, such that the activity in the cochlea produced by a masking sound “SWAMPS” that produced by the target sound. Another type of masking, known as “SUPPRESSION,” occurs when the response to the masker reduces the neural (and in some cases, the mechanical) response to the target sound.
Low-frequency sounds are more likely to mask high frequencies than vice versa, particularly at high sound intensities. This asymmetric aspect of masking is known as the “upward spread of masking.”
On this scale, 0 dB sound pressure level (SPL) is defined as 20 micro-Pascals (μPa), which corresponds roughly to the quietest perceptible sound level, and 120 dB SPL is considered dangerously loud.
Interaural Time Difference (ITD)
Differences in time of hearing between the two ears
Spatial Hearing
We have a 360° field of hearing. Our auditory acuity is, however, at least an order of magnitude poorer than vision in locating an object in space. Consequently, our auditory localization abilities are most useful in alerting us and allowing us to orient towards sources,
The two main sources of information both come from a comparison of the sounds at the two ears - ITDs and ILDs
Interaural Time Differences (ITD)
Differences (usually in time or intensity) between the two ears
In general, we are most sensitive to ITDs at low frequencies (below about 1.5 kHz).
Interaural Level Differences (ILD)
Differences in sound intensity between the two ears
Pain
Defined as “an unpleasant sensory and emotional experience associated w actual or potential tissue damage, or described in terms of such damage,” according to the International Association for the Study of Pain
Interoception
The sense of the physiological state of the body; hunger, thirst, temperature, pain and other sensations relevant to homeostasis; visceral input such as heart rate, blood pressure, and digestive activity give rise to an experience of the body’s internal states and physiological reactions to external stimulation; this experience has been described as a representation of “the material me” and is hypothesized to be the foundation of subjective feelings, emotion, and self-awareness
Cutaneous Senses
The senses of the skin: tactile, thermal, pruritic (itchy), painful and pleasant
Transduction
A process in which physical energy converts into neural energy
A-fibers
Fast-conducting sensory nerves with myelinated axons. Larger diameter and thicker myelin sheaths increases conduction speed. Aβ-fibers conduct touch signals from low-threshold mechanoreceptors with a velocity of 80 m/s and a diameter of 10 μm; Aδ-fibers have a diameter of 2.5 μm and conduct cold, noxious, and thermal signals at 12 m/s. The third and fastest conducting A-fiber is the Aα, which conducts proprioceptive information with a velocity of 120 m/s and a diameter of 20 μm.
Somatosensory Cortex
Consists of primary sensory cortex (S1) in the postcentral gyrus in the parietal lobes and secondary somatosensory cortex (S2) which is defined functionally and found in the upper bank of the lateral sulcus, called the parietal operculum; somatosensory cortex also includes parts of the insular cortex
Somatotopically organized
When the parts of the body that are represented in a particular brain region are organized and topographically according to their physical location in the body
C-pain fibers
C-pain fibers convey noxious, thermal, and heat signals
C-fibers
C-fibers: Slow-conducting unmyelinated thin sensory afferents with a diameter of 1 μm and a conduction velocity of approximately 1 m/s. C-pain fibers convey noxious, thermal, and heat signals; C-tactile fibers convey gentle touch, light stroking.
c-tactile fibers
C-tactile fibers convey gentle touch, light stroking
Social touch hypothesis
Proposes that social touch is a distinct domain of touch; c-tactile afferents form a special pathway that distinguishes social touch from other types of touch by selectively firing in response to touch of social affective relevance; thus sending affective info parallel to the discriminatory info from the Ab-fibers; in this way, the socially relevant touch stands out from the rest as having special positive emotional value and is processed further in affect-related brain areas such as the insula
Analgesics
Pain relief
Endorphin
An endogenous morphine-like peptide that binds to the opiod receptors in the brain and body; synthesized in the body’s nervous system
Allodynia
Pain due to a stimulus that does not normally provoke pain, e.g., when a light, stroking 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
Sensitization
Occurs when the response to a stimulus increases w exposure
Placebo Effect
Effects from a treatment that are not caused by the physical properties of a treatment but by the meaning ascribed to it. These effects reflect the brain’s own activation of modulatory systems, which is triggered by positive expectation or desire for a successful treatment. Placebo analgesia is the most well-studied placebo effect and has been shown to depend, to a large degree, on opioid mechanisms. Placebo analgesia can be reversed by the pharmacological blocking of opioid receptors. The word “placebo” is probably derived from the Latin word “placebit” (“it will please”).
Descending pain modulatory system
top-down system involving several parts of the brain and brainstem, which inhibits nociceptive signaling so that the more important actions can be attended to
A top-down pain-modulating system able to inhibit or facilitate pain. The pathway produces analgesia by the release of endogenous opioids. Several brain structures and nuclei are part of this circuit, such as the frontal lobe areas of the anterior cingulate cortex, orbitofrontal cortex, and insular cortex; and nuclei in the amygdala and the hypothalamus, which all project to a structure in the midbrain called the periaqueductal grey (PAG). The PAG then controls ascending pain transmission from the afferent pain system indirectly through the rostral ventromedial medulla (RVM) in the brainstem, which uses ON- and OFF-cells to inhibit or facilitate nociceptive signals at the spinal dorsal horn.
Nociceptors
High-threshold sensory receptors of the peripheral somatosensory nervous system that are capable of transducing and encoding noxious stimuli; nociceptors send info abt actual/impending tissued damage to the brain; these signals can often lead to pain, but nociception and pain are not the same
Nociception
Our ability to sense pain (pain, discomfort)
Exteroception
The sense of the external world, of all stimulation originating from outside our own bodies
Cochlea
Spiral bone structure in the inner ear containing auditory hair cells
Rods
Photoreceptors of the retina sensitive to low levels of light; located around the fovea
