HOME

TheInfoList



OR:

Stimulus modality, also called sensory modality, is one aspect of a
stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...
or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include:
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
,
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...
,
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
,
taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
,
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
, and smell. The type and location of the
sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The ...
activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary.


Multimodal perception

Multimodal perception is the ability of the mammalian nervous system to combine all of the different inputs of the
sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain involved i ...
to result in an enhanced detection or identification of a particular stimulus. Combinations of all sensory modalities are done in cases where a single sensory modality results in ambiguous and incomplete result. Integration of all sensory modalities occurs when multimodal neurons receive sensory information which overlaps with different modalities. Multimodal neurons are found in the superior colliculus; they respond to the versatility of various sensory inputs. The multimodal neurons lead to change of behavior and assist in analyzing behavior responses to certain stimulus. Information from two or more
sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system re ...
s is encountered. Multimodal perception is not limited to one area of the brain: many brain regions are activated when sensory information is perceived from the environment. In fact, the hypothesis of having a centralized multisensory region is receiving continually more speculation, as several regions previously uninvestigated are now considered multimodal. The reasons behind this are currently being investigated by several research groups, but it is now understood to approach these issues from a decentralized theoretical perspective. Moreover, several labs using invertebrate model organisms will provide invaluable information to the community as these are more easily studied and are considered to have decentralized nervous systems.


Lip reading

Lip reading The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
is a multimodal process for humans. By watching movements of lips and face, humans get conditioned and practice lip reading. Silent lip reading activates the
auditory cortex The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to ...
. When sounds are matched or mismatched with the movements of the lips, temporal sulcus of the left hemisphere becomes more active.


Integration effect

Multimodal
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous syste ...
comes into effect when a unimodal stimulus fails to produce a response. Integration effect is applied when the brain detects weak unimodal signals and combines them to create a multimodal perception for the
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
. Integration effect is plausible when different stimuli are coincidental. This integration is depressed when multisensory information is not coincidentally presented.


Polymodality

''Polymodality'' is the feature of a single receptor of responding to multiple modalities, such as
free nerve endings A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. ''Afferent'' in this case means bringing information from the body's periphery toward the brain. They function as cut ...
which can respond to temperature, mechanical stimuli (touch, pressure, stretch) or pain (
nociception Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the Somatosensory system, sensory nervous system's process of encoding Noxious stimulus, noxious stimuli. It deals with a series of events and processes required for an org ...
).


Light modality


Description

The stimulus modality for vision is light; the human eye is able to access only a limited section of the
electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...
, between 380 and 760
nanometre 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...
s. Specific inhibitory responses that take place in the visual cortex help create a visual focus on a specific point rather than the entire surrounding.


Perception

To perceive a light stimulus, the eye must first refract the light so that it directly hits the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
. Refraction in the eye is completed through the combined efforts of the
cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...
,
lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
and
iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...
. The transduction of light into neural activity occurs via the
photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiat ...
s in the retina. When there is no light,
Vitamin A Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably ...
in the body attaches itself to another molecule and becomes a protein. The entire structure consisting of the two molecules becomes a
photopigment Photopigments are unstable pigments that undergo a chemical change when they absorb light. The term is generally applied to the non-protein chromophore moiety of photosensitive chromoproteins, such as the pigments involved in photosynthesis and pho ...
. When a particle of light hits the photoreceptors of the eye, the two molecules come apart from each other and a chain of chemical reactions occurs. The chemical reaction begins with the photoreceptor sending a message to a neuron called the
bipolar cell A bipolar neuron, or bipolar cell, is a type of neuron that has two extensions (one axon and one dendrite). Many bipolar cells are specialized sensory neurons for the transmission of sense. As such, they are part of the sensory pathways for smel ...
through the use of an
action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells ...
, or nerve impulse. Finally, a message is sent to the ganglion cell and then finally the brain.


Adaptation

The eye is able to detect a visual stimulus when the
photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are Massless particle, massless ...
(light packets) cause a photopigment molecule, primarily
rhodopsin Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransductio ...
, to come apart. Rhodopsin, which is usually pink, becomes bleached in the process. At high levels of light, photopigments are broken apart faster than can be regenerated. Because a low number of photopigments have been regenerated, the eyes are not sensitive to light. When entering a dark room after being in a well lit area, the eyes require time for a good quantity of rhodopsin to regenerate. As more time passes, there is a higher chance that the photons will split an unbleached photopigment because the rate of regeneration will have surpassed the rate of bleaching. This is called
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...
.


Colour stimuli

Humans are able to see an array of colours because light in the visible spectrum is made up of different wavelengths (from 380 to 760 nm). Our ability to see in colour is due to three different
cone cells Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cone ...
in the retina, containing three different photopigments. The three cones are each specialized to best pick up a certain wavelength (420, 530 and 560 nm or roughly the colours blue, green and red). The brain is able to distinguish the wavelength and colour in the field of vision by figuring out which cone has been stimulated. The physical dimensions of colour include
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
, intensity and purity while the related perceptual dimensions include
hue In color theory, hue is one of the main properties (called color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that ...
,
brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...
and saturation. Primates are the only mammals with colour vision. The Trichromatic theory was proposed in 1802 by Thomas Young. According to Young, the human visual system is able to create any colour through the collection of information from the three cones. The system will put together the information and systematize a new colour based on the amount of each hue that has been detected.


Subliminal visual stimuli

Some studies show that subliminal stimuli can affect attitude. In a 1992 study Krosnick, Betz, Jussim and Lynn conducted a study where participants were shown a series of slides in which different people were going through normal every day activities (i.e. going to the car, sitting in a restaurant). These slides were preceded by slides that caused either positive emotional arousal (i.e. bridal couple, a child with a Mickey Mouse doll) or negative emotional arousal (i.e. a bucket of snakes, a face on fire) for a period 13
milliseconds A millisecond (from ''milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds. A unit of 10 milliseconds may be called ...
that participants consciously perceived as a sudden flash of light. None of the individuals were told of the subliminal images. The experiment found that during the questionnaire round, participants were more likely to assign positive personality traits to those in the pictures that were preceded by the positive subliminal images and negative personality traits to those in the pictures that were preceded by the negative subliminal images.


Tests

Some common tests that measure visual health include
visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...
tests, refraction tests, visual field tests and colour vision tests. Visual acuity tests are the most common tests and they measure the ability to bring details into focus at different distances. Usually this test is conducted by having participants read a map of letters or symbols while one eye is covered. Refraction tests measure the eye's need for glasses or
corrective lenses A corrective lens is a lens (i.e. a transmissive optical device) that is typically worn in front of the eye to improve daily vision. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glas ...
. This test is able to detect whether a person may be nearsighted or farsighted. These conditions occur when the light rays entering the eye are unable to converge on a single spot on the
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
. Both refractive errors require corrective lenses in order to cure blurriness of vision. Visual field tests detect any gaps in peripheral vision. In healthy normal vision, an individual should be able to partially perceive objects to the left or right of their field of view using both eyes at one time. The center field of vision is seen in most detail. Colour vision tests are used to measure one's ability to distinguish colours. It is used to diagnose colour blindness. This test is also used as an important step in some job screening processes as the ability to see colour in such jobs may be crucial. Examples include military work or law enforcement.


Sound modality


Description

The stimulus modality for
hearing Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is audit ...
is sound. Sound is created through changes in the pressure of the air. As an object vibrates, it compresses the surrounding molecules of air as it moves towards a given point and expands the molecules as it moves away from the point. Periodicity in sound waves is measured in
hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that o ...
. Humans, on average, are able to detect sounds as pitched when they contain periodic or quasi-periodic variations that fall between the range of 30 to 20000 hertz.


Perception

When there are vibrations in the air, the
eardrum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the ...
is stimulated. The eardrum collects these vibrations and sends them to receptor cells. The
ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditor ...
which are connected to the eardrum pass the vibrations to the fluid-filled
cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory o ...
. Once the vibrations reach the cochlea, the
stirrup A stirrup is a light frame or ring that holds the foot of a rider, attached to the saddle by a strap, often called a ''stirrup leather''. Stirrups are usually paired and are used to aid in mounting and as a support while using a riding animal ...
(part of the ossicles) puts pressure on the
oval window The oval window (or ''fenestra vestibuli'' or ''fenestra ovalis'') is a membrane-covered opening from the middle ear to the cochlea of the inner ear. Vibrations that contact the tympanic membrane travel through the three ossicles and into the in ...
. This opening allows the vibrations to move through the liquid in the cochlea where the receptive organ is able to sense it.


Pitch, loudness and timbre

There are many different qualities in sound stimuli including
loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...
, pitch and
timbre In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musica ...
. The human ear is able to detect differences in pitch through the movement of auditory hair cells found on the
basilar membrane The basilar membrane is a stiff structural element within the cochlea of the inner ear which separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani. The basilar membrane moves up and down ...
. High frequency sounds will stimulate the auditory hair cells at the base of the basilar membrane while medium frequency sounds cause vibrations of auditory hair cells located at the middle of the basilar membrane. For frequencies that are lower than 200 Hz, the tip of the basilar membrane vibrates in sync with the sound waves. In turn, neurons are fired at the same rate as the vibrations. The brain is able to measure the vibrations and is then aware of any low frequency pitches. When a louder sound is heard, more hair cells are stimulated and the intensity of firing of
axons An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...
in the
cochlear nerve The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information ...
is increased. However, because the rate of firing also defines low pitch the brain has an alternate way of encoding for loudness of low frequency sounds. The number of hair cells that are stimulated is thought to communicate loudness in low pitch frequencies. Aside from pitch and loudness, another quality that distinguishes sound stimuli is timbre. Timbre allows us to hear the difference between two instruments that are playing at the same frequency and loudness, for example. When two simple tones are put together they create a complex tone. The simple tones of an instrument are called
harmonics A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', ...
or
overtones An overtone is any resonant frequency above the fundamental frequency of a sound. (An overtone may or may not be a harmonic) In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental i ...
. Timbre is created by putting the harmonics together with the
fundamental frequency The fundamental frequency, often referred to simply as the ''fundamental'', is defined as the lowest frequency of a periodic waveform. In music, the fundamental is the musical pitch of a note that is perceived as the lowest partial present. I ...
(a sound's basic pitch). When a complex sound is heard, it causes different parts in the basilar membrane to become simultaneously stimulated and flex. In this way, different timbres can be distinguished.


Sound stimuli and human fetuses

A number of studies have shown that a human fetus will respond to sound stimuli coming from the outside world. In a series of 214 tests conducted on 7 pregnant women, a reliable increase in fetal movement was detected in the minute directly following the application of a sound stimulus to the abdomen of the mother with a frequency of 120 per second.


Tests

Hearing tests A hearing test provides an evaluation of the sensitivity of a person's sense of hearing and is most often performed by an audiologist using an audiometer. An audiometer is used to determine a person's hearing sensitivity at different frequencies. ...
are administered to ensure optimal function of the ear and to observe whether or not sound stimuli is entering the ear drum and reaching the brain as should be. The most common hearing tests require the spoken response to words or tones. Some hearing tests include the whispered speech test,
pure tone audiometry Pure-tone audiometry is the main hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss and thus providing a basis for diagnosis and management. Pu ...
, the tuning fork test, speech reception and word recognition tests,
otoacoustic emission An otoacoustic emission (OAE) is a sound that is generated from within the inner ear. Having been predicted by Austrian astrophysicist Thomas Gold in 1948, its existence was first demonstrated experimentally by British physicist David Kemp in 197 ...
s (OAE) test and
auditory brainstem response The auditory brainstem response (ABR), also called brainstem evoked response audiometry (BERA), is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The measured ...
(ABR) test. During a whispered speech test, the participant is asked to cover the opening of one ear with a finger. The tester will then step back 1 to 2 feet behind the participant and say a series of words in a soft whisper. The participant is then asked to repeat what is heard. If the participant is unable to distinguish the word, the tester will speak progressively louder until the participant is able to understand what is being said. The other ear is then tested. In
pure tone audiometry Pure-tone audiometry is the main hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss and thus providing a basis for diagnosis and management. Pu ...
, an
audiometer An audiometer is a machine used for evaluating hearing acuity. They usually consist of an embedded hardware unit connected to a pair of headphones and a test subject feedback button, sometimes controlled by a standard PC. Such systems can also be ...
is used to play a series of tones using headphones. The participants listen to the tones which will vary in pitch and loudness. The test will play with the volume controls and the participant is asked to signal when he or she can no longer hear the tone being played. The testing is completed after listening to a range of pitches. Each ear is tested individually. During the tuning fork test, the tester will have the
tuning fork A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs ( tines) formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it agains ...
vibrate so that it makes a sound. The tuning fork is placed in a specific place around the participant and hearing is observed. In some instances, individuals will show trouble hearing in places such as behind the ear. Speech recognition and word recognition tests measure how well an individual can hear normal day-to-day conversation. The participant is told to repeat conversation being spoken at different volumes. The spondee threshold test is a related test that detects the loudness at which the participant is able to repeat half of a list of two syllable words or spondees.
Otoacoustic emission An otoacoustic emission (OAE) is a sound that is generated from within the inner ear. Having been predicted by Austrian astrophysicist Thomas Gold in 1948, its existence was first demonstrated experimentally by British physicist David Kemp in 197 ...
s test (OAE) and
auditory brainstem response The auditory brainstem response (ABR), also called brainstem evoked response audiometry (BERA), is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp. The measured ...
(ABR) testing measures the brain's response to sounds. The OAE measures hearing of newborns by placing an emitting sound into the baby's ear through a probe. A microphone placed in the baby's
ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna (anatomy), pinna to the eardrum and is about in length and in di ...
will pick up the inner ear's response to sound stimulation and allows for observation. The ABR, also known as the brainstem auditory evoked response (BAER) test or auditory brainstem evoked potential (ABEP) test measure the brain's response to clicking sounds sent through headphones.
Electrodes An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials dep ...
on the scalp and earlobes record a graph of the response.


Taste modality


Description


Taste modality in mammals

In mammals, taste stimuli are encountered by axonless receptor cells located in
taste bud Taste buds contain the taste receptor cells, which are also known as gustatory cells. The taste receptors are located around the small structures known as papillae found on the upper surface of the tongue, soft palate, upper esophagus, the c ...
s on the tongue and
pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
. Receptor cells disseminate onto different
neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa ...
s and convey the message of a particular taste in a single medullar nucleus. This
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
detection system deals with taste stimuli. The pheromone detection system is distinct from the normal taste system, and is designed like the
olfactory system The olfactory system, or sense of smell, is the sensory system used for smelling ( olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an ...
.


Taste modality in flies and mammals

In insect and mammalian taste, receptor cells changes into attractive or aversive stimulus. The number of taste receptors in a mammalian
tongue The tongue is a muscular organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive process, and is the primary organ of taste. The tongue's upper surface (dorsum) is covered by taste ...
and on the tongue of the fly ( labellum) is same in amount. Most of the receptors are dedicated to detect repulsive
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...
.


Perception

Perceptions of taste is generated by the following sensory afferents:
gustatory The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
,
olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...
, and
somatosensory In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position ( proprioception), and pain. It ...
fibers. Taste perception is created by combining multiple sensory inputs. Different modalities help determine perception of taste especially when attention is drawn to particular sensory characteristics which is different from taste.


Integration of taste and smell modality

Impression of both taste and smell occurs in heteromodal regions of the limbic and paralimbic brain. Taste–odor integration occurs at earlier stages of processing. By life experience, factors such as the physiological significance of a given stimulus is perceived. Learning and affective processing are the primary functions of limbic and paralimbic brain. Taste perception is a combination of oral somatosensation and retronasal olfaction.


Pleasure of food

The sensation of taste come from oral somatosensory stimulation and with retronasal olfaction. The perceived pleasure encountered when eating and drinking is influenced by: # sensory features, such as taste quality # experience, such as prior exposure to taste-odor mixtures # internal state # cognitive context, such as information about brand


Temperature modality


Description

Temperature modality excites or elicits a symptom through cold or hot temperature. Different mammalian species have different temperature modality.


Perception

The
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different d ...
somatosensory system detects changes in temperature. The perception begins when thermal stimuli from a
homeostatic In biology, homeostasis (British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism an ...
set-point excite temperature specific sensory nerves in the skin. Then with the help of sensing range, specific thermosensory fibers respond to warmth and to cold. Then specific cutaneous cold and warm receptors conduct units that exhibit a discharge at constant skin temperature.


Nerve fibers for temperature

Warm and cold sensitive nerve fibers differ in structure and function. The cold-sensitive and warm-sensitive nerve fibers are underneath the skin surface. Terminals of each temperature-sensitive fiber do not branch away to different organs in the body. They form a small sensitive point which are unique from neighboring fibers. Skin used by the single receptor ending of a temperature-sensitive nerve fiber is small. There are 20 cold points per square centimeter in the lips, 4 in the finger, and less than 1 cold point per square centimeter in trunk areas. There are 5 times as many cold sensitive points as warm sensitive points.


Pressure modality


Description

The sense of touch, or tactile perception, is what allows organisms to feel the world around them. The environment acts as an external stimulus, and tactile perception is the act of passively exploring the world to simply sense it. To make sense of the stimuli, an organism will undergo active exploration, or
haptic perception Haptic perception ( gr, haptόs, script=latn, italics=yes "palpable", ''haptikόs'' "suitable for touch") means literally the ability "to grasp something". Perception in this case is achieved through the active exploration of surfaces and objects b ...
, by moving their hands or other areas with environment-skin contact. This will give a sense of what is being perceived, and give information about size, shape, weight, temperature, and material. Tactile stimulation can be direct in the form of bodily contact, or indirect through the use of a tool or probe. Direct and indirect send different types messages to the brain, but both provide information regarding roughness, hardness, stickiness, and warmth. The use of a probe elicits a response based on the vibrations in the instrument rather than direct environmental information. Tactual perception gives information regarding
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different d ...
stimuli (pressure, vibration, and temperature), kinaesthetic stimuli (limb movement), and
proprioceptive Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense". Proprioception is mediated by proprioceptors, mechanosensory neurons ...
stimuli (position of the body). There are varying degrees of tactual sensitivity and thresholds, both between individuals and between different time periods in an individual's life. It has been observed that individuals have differing levels of tactile sensitivity between each hand. This may be due to callouses forming on the skin of the most used hand, creating a buffer between the stimulus and the receptor. Alternately, the difference in sensitivity may be due to a difference in the cerebral functions or ability of the
left Left may refer to: Music * ''Left'' (Hope of the States album), 2006 * ''Left'' (Monkey House album), 2016 * "Left", a song by Nickelback from the album '' Curb'', 1996 Direction * Left (direction), the relative direction opposite of right * ...
and
right hemisphere The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebr ...
. Tests have also shown that deaf children have a greater degree of tactile sensitivity than that of children with normal hearing ability, and that girls generally have a greater degree of sensitivity than that of boys. Tactile information is often used as additional stimuli to resolve a sensory ambiguity. For example, a surface can be seen as rough, but this inference can only be proven through touching the material. When sensory information from each modality involved corresponds, the ambiguity is resolved.


Somatosensory information

Touch messages, in comparison to other sensory stimuli, have a large distance to travel to get to the brain. Tactual perception is achieved through the response of
mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, a ...
s in the skin that detect physical stimuli. The response from a mechanoreceptor detecting pressure can be experienced as a touch, discomfort, or pain, and the force of pressure is measured by a pressure algometer and a dolorimeter. Mechanoreceptors are situated in highly vascularized skin, and appear in both glabrous and hairy skin. Each mechanoreceptor is tuned to a different sensitivity, and will fire its action potential only when there is enough energy. The axons of these single tactile receptors will converge into a single nerve trunk, and the signal is then sent to the spinal cord where the message makes its way to the somatosensory systems in the brain.


Mechanoreceptors

There are four types of mechanoreceptors: Meissner corpuscles and merkel cell neurite complexes, located between the epidermis and dermis, and
Pacinian Pacinian corpuscle or lamellar corpuscle or Vater-Pacini corpuscle; is one of the four major types of mechanoreceptors (specialized nerve ending with adventitious tissue for mechanical sensation) found in mammalian skin. This type of mechanorece ...
corpuscles and
Ruffini ending The Bulbous corpuscle or Ruffini ending or Ruffini corpuscle is a slowly adapting mechanoreceptor located in the cutaneous tissue between the dermal papillae and the hypodermis. It is named after Angelo Ruffini Angelo Ruffini (Pretare of Arquata ...
s, located deep within the dermis and subcutaneous tissue. Mechanoreceptors are classified in terms of their adaptation rate and the size of their receptive field. Specific mechanoreceptors and their functions include:Wolfe, J., Kluender, K., & Levi, D. (2009). Sensation and perception. (2 ed.). Sunderland: Sinauer Associates. * Thermoreceptors that detect changes in skin temperature. * Kinesthetic receptors detect our movements and the position of our limbs. * Nociceptors that have bare nerve endings that detect tissue damage and give the sensation of pain.


Tests

A common test used to measure the sensitivity of a person to tactile stimuli is measuring their two-point touch threshold. This is the smallest separation of two points at which two distinct points of contact can be sensed rather than one. Different parts of the body have different degrees of tactile acuity, with extremities such as the fingers, face, and toes being the most sensitive. When two distinct points are perceived, it means that your brain receives two different signals. The differences of acuity for different parts of the body are the result of differences in the concentration of receptors.


Use in clinical psychology

Tactile stimulation is used in clinical psychology through the method of prompting. Prompting is the use of a set of instructions designed to guide a participant through learning a behavior. A physical prompt involves stimulation in the form of physically guided behavior in the appropriate situation and environment. The physical stimulus perceived through prompting is similar to the physical stimulus that would be experienced in a real-world situation, and is makes the target behavior more likely in a real situation.


Smell modality


Sensation

The sense of smell is called
olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...
. All materials constantly shed molecules, which float into the nose or are sucked in through breathing. Inside the nasal chambers is the
neuroepithelium Neuroepithelial cells, or neuroectodermal cells, form the wall of the closed neural tube in early embryonic development. The neuroepithelial cells span the thickness of the tube's wall, connecting with the pial surface and with the ventricular or ...
, a lining deep within the nostrils that contains the receptors responsible for detecting molecules that are small enough to smell. These receptor neurons then synapse at the olfactory cranial nerve (CN I), which sends the information to the olfactory bulbs in the brain for initial processing. The signal is then sent to the remaining olfactory cortex for more complex processing.


Odors

An olfactory sensation is called an
odor An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
. For a molecule to trigger
olfactory receptor neuron An olfactory receptor neuron (ORN), also called an olfactory sensory neuron (OSN), is a sensory neuron within the olfactory system. Structure Humans have between 10 and 20 million olfactory receptor neurons (ORNs). In vertebrates, ORNs are ...
s, it must have specific properties. The molecule must be: # volatile (able to float through the air) # small (less than 5.8 x 10-22 grams) #
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, ...
(repellant to water) However, humans do not process the smell of various common molecules such as those present in the air. Our olfactory ability can vary due to different conditions. For example, our olfactory detection thresholds can change due to molecules with differing lengths of carbon chains. A molecule with a longer carbon chain is easier to detect, and has a lower detection threshold. Additionally, women generally have lower olfactory thresholds than men, and this effect is magnified during a woman's
ovulatory period Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertil ...
. People can sometimes experience a hallucination of smell, as in the case of phantosmia.


Interaction with other modalities

Olfaction interacts with other sensory modalities in significant ways. The strongest interaction is that of olfaction with taste. Studies have shown that an odor coupled with a taste increases the perceived intensity of the taste, and that an absence of a corresponding smell decreases the perceived intensity of a taste. The olfactory stimulation can occur before or during the episode of taste stimulation. The dual perception of the stimulus produces an interaction that facilitates association of the experience through an additive neural response and memorization of the stimulus. This association can also be made between olfactory and tactile stimuli during the act of swallowing. In each case, temporal synchrony is important.


Tests

A common psychophysical test of olfactory ability is the triangle test. In this test, the participant is given three odors to smell. Of these three odors, two are the same and one is different, and the participant must choose which odor is the unique one. To test the sensitivity of olfaction, the staircase method is often used. In this method, the odor's concentration is increased until the participant is able to sense it, and subsequently decreased until the participant reports no sensation.


See also

*
Autonomous sensory meridian response Autonomous sensory meridian response (ASMR) is a tingling sensation that usually begins on the scalp and moves down the back of the neck and upper spine. A pleasant form of paresthesia, it has been compared with auditory-tactile synesthesia a ...
* Crossmodal Attention *
Synesthesia Synesthesia (American English) or synaesthesia (British English) is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People who re ...
(
Ideasthesia Ideasthesia (alternative spelling ideaesthesia) is a neuropsychological phenomenon in which activations of concepts (inducers) evoke perception-like sensory experiences (concurrents). The name comes from the Ancient Greek () and (), meaning 'se ...
) *
Modality (semiotics) In semiotics, a modality is a particular way in which information is to be encoded for presentation to humans, i.e. to the type of sign and to the status of reality ascribed to or claimed by a sign, text, or genre. It is more closely associated w ...
*
Pallesthesia Pallesthesia (\ˌpal-es-ˈthē-zh(ē-)ə\), or vibratory sensation, is the ability to perceive vibration.Campbell, W. W., & DeJong, R. N. (2013). DeJong's the neurologic examination. lectronic resourceWilliam W. Campbell. Philadelphia, PA : Lipp ...


References

{{DEFAULTSORT:Stimulus Modality Sensory systems Perception