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57-559: Mechanosensory information includes that of light touch, vibration, pressure and tension in the skin. Much of this information belongs to the sense of touch which is a general somatic sense in contrast to the special senses of sight , smell , taste , hearing and balance . Nociceptory information is that received from pain and temperature that is deemed as harmful (noxious). Thermoreceptors relay temperature information in normal circumstances. Nociceptors are specialised receptors for signals of pain. The sense of touch in perceiving

114-454: A peripheral neuropathy involving peripheral nerves of the somatosensory system. This may present as numbness or paresthesia . Haptic technology can provide touch sensation in virtual and real environments. In the field of speech therapy , tactile feedback can be used to treat speech disorders . Affectionate touch is present in everyday life and can take multiple forms. These actions, however, seem to carry specific functions even though

171-486: A small receptive field (extremely detailed information), they are used in areas like fingertips the most; they are not covered (shelled) and thus respond to pressures over long periods. Tactile corpuscles react to moderate vibration (10–50 Hz) and light touch. They are located in the dermal papillae ; due to their reactivity, they are primarily located in fingertips and lips. They respond in quick action potentials , unlike Merkel nerve endings. They are responsible for

228-402: A substance in the mouth reacts chemically with taste receptor cells located on taste buds in the oral cavity , mostly on the tongue . Taste, along with smell ( olfaction ) and trigeminal nerve stimulation (registering texture, pain, and temperature), determines flavors of food or other substances. Humans have taste receptors on taste buds (gustatory calyculi) and other areas including

285-451: A variety of mechanoreceptors , muscle nerves, etc.; temperature, detected by thermoreceptors ; and "coolness" (such as of menthol ) and "hotness" ( pungency ), through chemesthesis . As taste senses both harmful and beneficial things, all basic tastes are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies. Sweetness helps to identify energy-rich foods, while bitterness serves as

342-491: A warning sign of poisons. Among humans , taste perception begins to fade around 50 years of age because of loss of tongue papillae and a general decrease in saliva production. Humans can also have distortion of tastes through dysgeusia . Not all mammals share the same taste senses: some rodents can taste starch (which humans cannot), cats cannot taste sweetness but can taste ATP , and several other carnivores including hyenas , dolphins , and sea lions , have lost

399-418: Is a chemoreception that forms the sense of smell. Olfaction has many purposes, such as the detection of hazards, pheromones , and food. It integrates with other senses to form the sense of flavor . Olfaction occurs when odorants bind to specific sites on olfactory receptors located in the nasal cavity . Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb , where

456-430: Is a type of sensory information that elicits an emotional reaction and is usually social in nature, such as a physical human touch. This type of information is actually coded differently than other sensory information. Intensity of affective touch is still encoded in the primary somatosensory cortex and is processed in a similar way to emotions invoked by sight and sound, as exemplified by the increase of adrenaline caused by

513-409: Is also considerably more densely innervated, with a hundred times more receptors per square centimeter. Molecules of odorants passing through the superior nasal concha of the nasal passages dissolve in the mucus that lines the superior portion of the cavity and are detected by olfactory receptors on the dendrites of the olfactory sensory neurons. This may occur by diffusion or by the binding of

570-449: Is better among adults with smaller index fingertips; this effect of finger size has been shown to underlie the better passive tactile spatial acuity of women, on average, compared to men. The density of tactile corpuscles , a type of mechanoreceptor that detects low-frequency vibrations, is greater in smaller fingers; the same may hold for Merkel cells , which detect the static indentations important for fine spatial acuity. Among children of

627-466: Is carried in general somatic afferents and general visceral afferents . Visual perception is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment. The resulting perception is also known as visual perception, eyesight, sight, or vision ( adjectival form : visual , optical , or ocular ). The various physiological components involved in vision are referred to collectively as

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684-470: Is important amongst some animals. Usually, tactile contact between two animals occurs through stroking, licking, or grooming. These behaviours are essential for the individual's social healthcare, as in the hypothalamus they induce the release of oxytocin, a hormone that decreases stress and anxiety and increases social bonding between animals. More precisely, the consistency of oxytocin neuron activation in rats stroked by humans has been observed, especially in

741-577: Is in the parietal lobe and its cortex is the primary somatosensory cortex ( Brodmann areas 3, 2 and 1 ) collectively referred to as S1. BA3 receives the densest projections from the thalamus . BA3a is involved with the sense of relative position of neighboring body parts and amount of effort being used during movement. BA3b is responsible for distributing somatosensory information, it projects texture information to BA1 and shape and size information to BA2. Region S2 ( secondary somatosensory cortex ) divides into Area S2 and parietal ventral area. Area S2

798-493: Is involved in numerous functions. The somatosensory system is spread through all major parts of the vertebrate body. It consists both of sensory receptors and sensory neurons in the periphery (skin, muscle and organs for example), to deeper neurons within the central nervous system . All afferent touch/vibration information ascends the spinal cord via the dorsal column-medial lemniscus pathway via gracilis (T7 and below) or cuneatus (T6 and above). Cuneatus sends signals to

855-508: Is involved with specific touch perception and is thus integrally linked with the amygdala and hippocampus to encode and reinforce memories. Parietal ventral area is the somatosensory relay to the premotor cortex and somatosensory memory hub, BA5. BA5 is the topographically organized somato memory field and association area. BA1 processes texture info while BA2 processes size and shape information. Area S2 processes light touch, pain, visceral sensation, and tactile attention. S1 processes

912-424: Is made up of at least six morphologically and biochemically different cell types. The proportion of olfactory epithelium compared to respiratory epithelium (not innervated, or supplied with nerves) gives an indication of the animal's olfactory sensitivity. Humans have about 10 cm (1.6 sq in) of olfactory epithelium, whereas some dogs have 170 cm (26 sq in). A dog's olfactory epithelium

969-409: Is the pathway responsible for the sending of fine touch information to the cerebral cortex of the brain. Crude touch (non-discriminating) is a sensory modality that allows the subject to sense that something has touched them, without being able to localize where they were touched (contrasting "fine touch"). Its fibres are carried in the spinothalamic tract , unlike the fine touch, which is carried in

1026-468: The sensory homunculus . The primary somatosensory cortex was initially defined from surface stimulation studies of Wilder Penfield , and parallel surface potential studies of Bard, Woolsey, and Marshall. Although initially defined to be roughly the same as Brodmann areas 3 , 1 , and 2 , more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as "primary somatosensory cortex", as it receives

1083-489: The central nervous system – information from special senses is carried in special somatic afferents and special visceral afferents . In contrast, the other sense, touch , is a somatic sense which does not have a specialized organ but comes from all over the body, most noticeably the skin but also the internal organs ( viscera ). Touch includes mechanoreception (pressure, vibration and proprioception ), pain ( nociception ) and heat ( thermoception ), and such information

1140-413: The ear and transduced into nerve impulses that are perceived by the brain (primarily in the temporal lobe ). Like touch , audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation . There are three main components of the human ear: the outer ear , the middle ear , and the inner ear . Smell, or olfaction,

1197-496: The lateral geniculate nucleus , to the primary and secondary visual cortex of the brain . Signals from the retina can also travel directly from the retina to the superior colliculus . The perception of objects and the totality of the visual scene is accomplished by the visual association cortex . The visual association cortex combines all sensory information perceived by the striate cortex which contains thousands of modules that are part of modular neural networks . The neurons in

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1254-404: The ability of touch to have an unconscious influence on such higher-order thoughts may provide a novel tool for marketing and communication strategies. Special senses In medicine and anatomy , the special senses are the senses that have specialized organs devoted to them: The distinction between special and general senses is used to classify nerve fibers running to and from

1311-509: The ability to read Braille and feel gentle stimuli. Pacinian corpuscles determine gross touch and distinguish rough and soft substances. They react in quick action potentials, especially to vibrations around 250 Hz (even up to centimeters away). They are the most sensitive to vibrations and have large receptor fields. Pacinian corpuscles react only to sudden stimuli so pressures like clothes that are always compressing their shape are quickly ignored. They have also been implicated in detecting

1368-417: The ability to sense up to four of their ancestral five taste senses. Postcentral gyrus In neuroanatomy , the postcentral gyrus is a prominent gyrus in the lateral parietal lobe of the human brain . It is the location of the primary somatosensory cortex , the main sensory receptive area for the sense of touch . Like other sensory areas, there is a map of sensory space in this location, called

1425-576: The back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. Each taste bud contains 50 to 100 taste receptor cells. The sensation of taste includes five established basic tastes: sweetness , sourness , saltiness , bitterness , and umami . Scientific experiments have proven that these five tastes exist and are distinct from one another. Taste buds are able to differentiate among different tastes through detecting interaction with different molecules or ions. Sweet, umami, and bitter tastes are triggered by

1482-415: The binding of molecules to G protein-coupled receptors on the cell membranes of taste buds. Saltiness and sourness are perceived when alkali metal or hydrogen ions enter taste buds, respectively. The basic tastes contribute only partially to the sensation and flavor of food in the mouth—other factors include smell , detected by the olfactory epithelium of the nose; texture , detected through

1539-435: The body, creating a map or sensory homunculus . Tactile signing is a common means of communication used by people with deafblindness . It is based on a sign language or another system of manual communication. Humans can communicate specific emotions through touch alone including anger, fear, disgust, love, gratitude, and sympathy via touch at much-better-than-chance levels. The two different types of mechanoreceptor in

1596-399: The brain for conscious perception. Somatosensory information from the face and head enter the brain via cranial nerves such as the trigeminal nerve . The neural pathways that go to the brain are structured such that information about the location of the physical stimulus is preserved. In this way, neighboring neurons in the somatosensory cortex represent nearby locations on the skin or in

1653-459: The brain, from the retina upstream to central ganglia in the brain . Note that up until now much of the above paragraph could apply to octopuses , mollusks , worms , insects and things more primitive; anything with a more concentrated nervous system and better eyes than say a jellyfish . However, the following applies to mammals generally and birds (in modified form): The retina in these more complex animals sends fibers (the optic nerve ) to

1710-407: The caudal paraventricular nucleus. It was found that this affiliative relationship induced by tactile contact is common no matter the relationship between the two individuals (mother-infant, male-female, human-animal). It has also been discovered that the level of oxytocin release through this behaviour correlates with the time course of social interaction as longer stroking induced a greater release of

1767-548: The cochlear nucleus indirectly via spinal grey matter, this info is used in determining if a perceived sound is just villi noise/irritation. All fibers cross (left becomes right) in the medulla. A somatosensory pathway will typically have three neurons: first-order, second-order, and third-order. Photoreceptors, similar to those found in the retina of the eye , detect potentially damaging ultraviolet radiation ( ultraviolet A specifically), inducing increased production of melanin by melanocytes . Thus tanning potentially offers

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1824-401: The conversion of light into neuronal signals. Based on feedback from the visual system, the lens of the eye adjusts its thickness to focus light on the photoreceptive cells of the retina, also known as the rods and cones, which detect the photons of light and respond by producing neural impulses . These signals are processed via complex feedforward and feedback processes by different parts of

1881-420: The dorsal column. As fine touch normally works in parallel to crude touch, a person will be able to localize touch until fibres carrying fine touch (in the dorsal column–medial lemniscus pathway) have been disrupted. Then the subject will feel the touch, but be unable to identify where they were touched. The somatosensory cortex encodes incoming sensory information from receptors all over the body. Affective touch

1938-443: The environment uses special sensory receptors in the skin called cutaneous receptors . They include mechanoreceptors such as tactile corpuscles that relay information about pressure and vibration; nociceptors, and thermoreceptors for temperature perception. Stimulation of the receptors activate peripheral sensory neurons that convey signals to the spinal cord that may drive a responsive reflex , and may also be conveyed to

1995-474: The evaluation of risks that occur during conducting such behaviours in the wild life, and further research is required to unveil the connection between tactile caring and fitness level. Studies show a correlation between touching a soft or hard object and how a person thinks or even makes decisions. Further, between the firmness of a touch and the evoking of gender stereotyping. Tactile memories as part of haptic memory , are organized somatotopically , following

2052-467: The evolutionary benefit from such a wide range of behaviours is not entirely understood. Researchers investigated the expression patterns and characteristics of 8 different affectionate touch actions - embracing, holding, kissing, leaning, petting, squeezing, stroking, and tickling - in a self-report study. It was found that the affectionate touch has distinct target areas on the body, different associated affect, comfort-value, and expression frequency based on

2109-400: The hormone. The importance of somatosensory stimulation in social animals such as primates has also been observed. Grooming is part of the social interaction primates exert on their conspecifics. This interaction is required between individuals to maintain the affiliative relationship within the group, avoid internal conflict and increase group bonding. However, such social interaction requires

2166-428: The location of objects which are sensed by the visual system (which provides confirmation of the place of those objects relative to the body), as input to the mechanical reflexes of the body. Fine touch (or discriminative touch) is a sensory modality that allows a subject to sense and localize touch. The form of touch where localization is not possible is known as crude touch. The dorsal column–medial lemniscus pathway

2223-504: The location of touch sensations on handheld tools. Bulbous corpuscles react slowly and respond to sustained skin stretch. They are responsible for the feeling of object slippage and play a major role in the kinesthetic sense and control of finger position and movement. Merkel and bulbous cells - slow-response - are myelinated ; the rest - fast-response - are not. All of these receptors are activated upon pressures that distort their shape causing an action potential. The postcentral gyrus

2280-460: The most rigorous being the grating orientation task. In this task subjects identify the orientation of a grooved surface presented in two different orientations, which can be applied manually or with automated equipment. Many studies have shown a decline in passive tactile spatial acuity with age; the reasons for this decline are unknown, but may include loss of tactile receptors during normal aging. Remarkably, index finger passive tactile spatial acuity

2337-417: The odorant to odorant-binding proteins . The mucus overlying the epithelium contains mucopolysaccharides , salts, enzymes , and antibodies (these are highly important, as the olfactory neurons provide a direct passage for infection to pass to the brain ). This mucus acts as a solvent for odor molecules, flows constantly, and is replaced approximately every ten minutes. Taste is the sensation produced when

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2394-416: The organization of the somatosensory cortex. A variety of studies have measured and investigated the causes for differences between individuals in the sense of fine touch. One well-studied area is passive tactile spatial acuity, the ability to resolve the fine spatial details of an object pressed against the stationary skin. A variety of methods have been used to measure passive tactile spatial acuity, perhaps

2451-417: The physical sensation to its related conceptual processing. Indeed, it was found that different physical properties - weight, texture, and hardness - of a touched object can influence social judgement and decision-making. For example, participants described a passage of a social interaction to be harsher when they touched a hard wooden block instead of a soft blanket prior to the task. Building on these findings,

2508-505: The prefrontal cortex is highly correlated with pleasantness scores of an affective touch. Inhibitory transcranial magnetic stimulation (TMS) of the primary somatosensory cortex inhibits the perception of affective touch intensity, but not affective touch pleasantness. Therefore, the S1 is not directly involved in processing socially affective touch pleasantness, but still plays a role in discriminating touch location and intensity. Tactile interaction

2565-409: The pressure of the surrounding medium through time, through an organ such as the ear . Sound may be heard through solid , liquid , or gaseous matter. It is one of the traditional five senses ; partial or total inability to hear is called hearing loss . In humans and other vertebrates, hearing is performed primarily by the auditory system : mechanical waves , known as vibrations are detected by

2622-418: The proprioceptors in the skin, muscles, and joints. The receptor for the sense of balance resides in the vestibular system in the ear (for the three-dimensional orientation of the head, and by inference, the rest of the body). Balance is also mediated by the kinesthetic reflex fed by proprioception (which senses the relative location of the rest of the body to the head). In addition, proprioception estimates

2679-504: The recognition of every member in the group. As such, it has been observed that the size of the neocortex is positively correlated with the size of the group, reflecting a limit to the number of recognizable members amongst which grooming can occur. Furthermore, the time course of grooming is related to vulnerability due to predation to which animals are exposed to whilst performing such social interaction. The relationship between tactile interaction, stress reduction and social bonding depends on

2736-406: The remaining info (crude touch, pain, temperature). BA7 integrates visual and proprioceptive info to locate objects in space. The insular cortex (insula) plays a role in the sense of bodily-ownership, bodily self-awareness, and perception. Insula also plays a role in conveying info about sensual touch, pain, temperature, itch, and local oxygen status. Insula is a highly connected relay and thus

2793-524: The same age, those with smaller fingers also tend to have better tactile acuity. Many studies have shown that passive tactile spatial acuity is enhanced among blind individuals compared to sighted individuals of the same age, possibly because of cross modal plasticity in the cerebral cortex of blind individuals. Perhaps also due to cortical plasticity, individuals who have been blind since birth reportedly consolidate tactile information more rapidly than sighted people. A somatosensory deficiency may be caused by

2850-435: The sensory input will start to interact with parts of the brain responsible for smell identification, memory , and emotion . Often, land organisms will have separate olfaction systems for smell and taste ( orthonasal smell and retronasal smell ), but water-dwelling organisms usually have only one system. In vertebrates, smells are sensed by olfactory sensory neurons in the olfactory epithelium . The olfactory epithelium

2907-503: The skin are termed low-threshold mechanoreceptors , and high threshold mechanoreceptors . The four mechanoreceptors in glabrous skin are low-threshold that respond to harmless stimuli. They are innervated by four different afferent fibers. High-threshold mechanoreceptors, respond to harmful stimuli . Merkel cell nerve endings are found in the basal epidermis and hair follicles ; they react to low vibrations (5–15  Hz ) and deep static touch such as shapes and edges. Due to having

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2964-408: The skin rapid protection from DNA damage and sunburn caused by ultraviolet radiation (DNA damage caused by ultraviolet B ). However, whether this offers protection is debatable, because the amount of melanin released by this process is modest in comparison to the amounts released in response to DNA damage caused by ultraviolet B radiation. The tactile feedback from proprioception is derived from

3021-419: The social touch of a loved one, as opposed to the physical inability to touch someone you do not love. Meanwhile, the feeling of pleasantness associated with affective touch activates the anterior cingulate cortex more than the primary somatosensory cortex. Functional magnetic resonance imaging (fMRI) data shows that increased blood-oxygen-level contrast (BOLD) signal in the anterior cingulate cortex as well as

3078-427: The striate cortex send axons to the extrastriate cortex , a region in the visual association cortex that surrounds the striate cortex. The human visual system perceives visible light in the range of wavelengths between 370 and 730 nanometers (0.00000037 to 0.00000073 meters) of the electromagnetic spectrum . Hearing, or auditory perception, is the ability to perceive sound by detecting vibrations , changes in

3135-465: The type of touch action that is performed. Besides the rather obvious sensory consequences of touch, it can also affect higher-level aspects of cognition such as social judgements and decision-making. This effect might arise due to a physical-to-mental scaffolding process in early development, whereby sensorimotor experiences are linked to the emergence of conceptual knowledge. Such links might be maintained throughout life, and so touching an object may cue

3192-428: The upper surface of the tongue and the epiglottis . The gustatory cortex is responsible for the perception of taste. The tongue is covered with thousands of small bumps called papillae , which are visible to the naked eye. Within each papilla are hundreds of taste buds. The exception to this is the filiform papillae that do not contain taste buds. There are between 2000 and 5000 taste buds that are located on

3249-399: The visual system. The visual system in animals allows individuals to assimilate information from their surroundings. The act of seeing starts when the cornea and then the lens of the eye focuses light from its surroundings onto a light-sensitive membrane in the back of the eye, called the retina . The retina is actually part of the brain that is isolated to serve as a transducer for

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