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| disrodersi n sensory enrves - two types: negative symptoms- numbness- any snesory impairment loss of pain or touch. Positive sysmtpoms: Parasthesias and neuropathic pain- inesnley painful experiences= anbormal snesory phenomonem (tingling pinas and needles, burning , pricking, shotoign ,stabbing etc.). |
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| nature of sensroy loss, duration fo symtpoms (constant/episodic), onset and progression of sysmptosm (acute or progressvie) , location fo symtposm and accompanyign sypmtoms: influence of factors. |
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| subsystem for processing different kind of stimuli. |
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| simtulus - presusre, recetpro class-mechanoreceptor, receptor cell type-cutaneous mechanoreceotpros |
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| (where you are in space) stimulus- displacement, receptor class-cmechanoreceptor, muscleand join receptors. |
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| stimulus- thermal, receptor class-thremporeceptor, cell tyeps- cold and warm receptors. |
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| stimulus- chemical, thermal or mechanical (is not hyperstimuatlion of these, is its own separate patwhay). Receptor class- cehmoreceptor, thermoreceptor ro mechanorecetpro. Cell type- xxx nocireceptors. |
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| DCMSL and STT relationship |
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| compleltley sperate, but aprallel, (sensoery receptor of face enter through brain stem ratehr than spinal cord). |
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| General organization o DCMLS and Spinthoalamc tract |
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| simliar, receptors all over peripheray. Same class of receptors- dorsal cells, that go up to dorsal root ganglion and that are unipolar. |
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| fine touch, viration, prorpioception |
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| pain, temperaure and crude touch. Three neuron relay, with two relay points. Information is conveyed to contralateral convex. |
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| strength of stimulus. In mechano receptor activation is determiend by ion channeles, clsoed at erst, but when activated ( i.e. by stretch)- they open up allow sodium in and create generator potential. |
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| lowest stimiulsut strength a subject can detect- determiend by sensitivty of receptor.. Need stimulus high enough to activate threshodl and create spike potential. |
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| receptors that diferi n timign of repsoen to stimulus |
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| slowly adapting- fire slowly but contanstlyt o a constant stimulus- useful for detecting a constant stimualt lasting for a while but nto changing . Radpily adapting- fires repeptively and really fastly (at onset and offset only), but for a very short period of time, sueful for a quickly dynamic stimulus |
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| minimal interstimulus distance requried to perceive to different stimuli happening to lcoation (i.e. two prongs of a pin). Varying sensitivy depending on the body part tested |
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| spacial area to whicih a cell can respond. If touch anywhere in receptive field , stimlulus will be the same to cortex if touch just outside, get inhibitory affect on signalst to cortex. Celsl with smaller receptive fields are best for fien touch. |
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| Overlap due to several peripheral nerves going to the same dorsal root, and peripheral nerves contribuitng axosn to adjacent dorsal roots. |
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| several different types in a single DRG. |
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| large diamtera and myelianted- high conduction velocity sensory function: proprioception receoptor type : muscle spindle ( Ia), and golgi tendon organ (Ib). Aka alphas. |
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| slightly smaller but conduct reasonably fast and myelinated. Mediate touch and vibration.. Aka Abeta. Tyep: meissners corucpels, muscle spindle, merkels receptor ,pacinian orpuscle, ruffini ending ,hari receptor |
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| aka adelta. Smaller , a little bit of myelin type- free nerve endings. Job: pain temperature |
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| type: fre nerve endings, very small and unmeylinated (slowly) - mediate pain/temperature and itch. |
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| Morphology of cutaneous mechanoreceptors |
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| superficail ones have smalelr receptive fields , more ventral (deeper), ha ve larger receptive fields. |
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| located udner epidermal ridge, and are rapidly adapting ( good for touch and motion ). Rather sueprficial, found udner hairless skin. |
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| loated above epidermal ridge- they are slowly adapting, useful for detecting edges and shapes. |
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| long axis alligned in parallel with stetch lines of ksins- whe open hadn and sretch skin they are activated.- they are slowly adapting. |
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| lcoated deep in dermal and subcutaneous layer. Fluid filled baloons (concentric). Useful for detecting vibration sense- rapidly adapting (vibration is on/off/on/off |
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| DCMLS pathway (lower body) |
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| from peripehry to dorssal roto ganglion to dorsal rotos in lumbar spinal cord. o spina l cord. Ipsilaterally ascends in thengracille tract. Synapse at dorsal nuclei (specifically the gracile nucleus) in caudal memdulla. Deccusate at itnernal arcuate fibers at caudal medulla and contineu to ascend through medudlla , pons , and midbrain via medial lemnicsucs. Touch and vibration ifno contineus to get relaeyd to the ventral posterior lateral nuclus of the thalamus- and then the third order neruons go through the posterior limb of the itnernal capsule where they termiante at the somatosensory cortex |
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| DCMLS pathway upper body) |
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| enters cervical spianl cord dorsal root and then up via the cuneate tract (lateral to gracile tract). Synapse at dorsal nuclei (specifically the cuneate nucleus) in caudal memdulla. Deccusate at itnernal arcuate fibers at caudal medulla and contineu to ascend through medudlla , pons , and midbrain via medial lemnicsucs. Touch and vibration ifno contineus to get relaeyd to the ventral posterior lateral nuclus of the thalamus- and then the third order neruons go through the posterior limb of the itnernal capsule where they termiante at the somatosensory cortex |
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| white matter tract in posterior funicculus . |
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| trigeminal mechanosensorysstyem function |
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| trigeminal ganglion. contains opthalmic maxilallyr and amndibular input. Sensory from face to cortex. Pons- where facial information enters. Synapses in principle nucleus fo trigeminal complex. Primary afferent terminates- second order projection neuron deccusates in the pons to form trigeminl limnescus. Runs clsoe to medial leminiscus. Ascends up throught he midbrain to the thalamus. Goes to Ventral Posterior MEDIAL nucleus of thalamus, Third order projeciton neuron goes to somatosensory cortex. Lesion below the pons would not have loss of sensation of lsos and vibration on the face. |
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| lesion insneosry cortexes possibilties |
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| dorsal roots effected every level . Gracilis and cunuetus ( for both arms and legs loss.). Dorsal column Nuclei on right side affected, medial limnicsucs on left sie affected, lesion in thalamsu or somatosensory cortex. |
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| proprioreceptor morphology |
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| muscle spindles detec muscle lenght, alligend in parallel with msucle fibers- itnrafusal muscle fibers are susroudned by capsule of connective tissue. Have multinucelated bag neuro and single chiain fibers. Inenrvated by alpha motor neurons. Gamam motor neuron is important for ressetting msucle spindle so snesitive ot new change. Afferent axosn are inenrvated by group 11s and group IIs. Group 1s are more rapidly adapting , sensitive ot quick changes. Type II more slowly adapting for static quality of stimulus. Activated when muscle is contracted and send signa lup . Golgi tendon organ are important for detecting muscle tension, arrangedd i sneries between muscle tendons and muscle fibers. Axonal 1b afferents intercalatae amongst colalgen fibrils. When muscle is contracted they get activated and send signal out. Density of receptors depends on how much info you need about what that part of your body is doing. Extraoccular muscles have a high dnesity of musclepinldes, hands have high dnesity of msucle spindles, trunks have much lwoer density of msucle spindles. Joint proprioception tested by having patient close eyse adn ask them how it is bieng moved. |
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| spincerebelalr tract for propriorectiopn |
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| muscle spindle afferents- goes from spinal cord al the way to cerebellum. Muscle spindles send signals intto the spinal cord from the lower body through the dorsal roots. Bifurcate and go up and down one or two segments before penetrating the dorsal horn. After penetrating dorsal horn, send out colalteral branches, some of them go to other neurons of the dorsal horn, others go to neurosn of the ventral horn to mediate segmental reflexes. THey also send sbrnaches up to clarkes nuclar in teh lumbar spinal cord (lamina 7 in intermediate gray matter zone). From clarkes nucleus , they ascend in the dorsal spinocerebelalr tract ( in alteral portion fo the psinal cord). Send projections up to the ipsilateral cerebellum (IMPROTANT DOESNT CROSS) as well as to teh dorsal column nuclei, where it joins the dorsal column medial lemniscus pathway. IMPORTANT THINGS: is possible for the signals receptor ot get to more than one place in the body . Can get to both primary somatosensory cortex as wel las to the cerellum. And can send collateral axonal proejctions to mediate otehr funcitons s uch as reflex. Rhomburg test belogns here- if clsoey oru eyes adn fall to one side when standing, means that you have lesion in spinocerebelalr tract mediating proprioception. Tabes dorsalis- degeneration fo al rge axons in dorsal column that mediate proprioception |
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| look at case in powerpoint (neurological exam results 2 etc. |
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| sensory informaiton from your legs coming in through the dorsal roots and then turning in the vasiculus grassilus, it cant go any farther because the dorsal/posterior median sulcus of teh spinal cord .Axons cant cross ove rthe sulcus so they get stopped, and they turn to ascend ipsilaterally- information coming in from upper body and arms enters but gets stoped by the axons that are carrying information from the legs. THey turn adn ascend more laterally to teh leg afferents. Once you get up to teh dorsal column nuclei you have nucleus gracillus and nucleus conueatus. Dcucsiate and form medial lemniscus- soamtoropy of medial lemniscus- of man standing up (upper body trunk, and lower body). By the time it gets to teh pons leg of man have been kciekd otu ofr under him- arms are now medial and legs are more lateral. In midbrain legs have risen and legs are above teh arms, and in the thalamus- legs highest, trunk, and then arms. As you go through psoterior libm of itnernal capsule and go to somatsoensory cortex, end up with elgs more medial and upper body mroe lateral. |
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| somatosensory portion fo thalamus |
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| Thalamus- egg shaped structure- Nuclei named based on anatmoical lcoaiton- VPL- inptu from medial lemniscus (rest of the body), wherase VPM receives inpum from teh face (rigeminal). Project to priamry somatosnesory cortex, SI (behidn central sulcus). postcentral gyrus, divided into four subregions:. 3aa,3b ,1, and 2. Each one receives input from a different kidn of receptor. Area 2 receieves input from receptors involved in complex feature detection. |
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| somatotropic arangement of human primary somatosensory cortex |
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| each of hte four regions of somatosensory cortex forms stripes mapping body. Hnads and face haveh igher relative represenation. |
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| somatosensory homunculsu and motor homunculus |
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| parralel eachother. SHows hati f person ahs both arm and leg tingling unliekly that it is occurign at teh somatosensory cortex since they are o opposite sides of hte brain. |
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| muscle psindle and golgi tendon pathway |
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| via. the dorsal column and the psinocerebellar tract |
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| ability of cortical processing whcih allows braint o recognize patterns common to stimuli of particular class (i.e. recognozing a paperclip jsut by touchign) (feature detection). (this is due to oreination dpeepdnant neurons , neurosn that fire differnetly depending on way somethign is palcedi n your hand) |
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| direction dependant neurons |
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| fire only when soemthign moves alogn ahnd in certain direciton- allow us toh ave graphasthesia-- being ablet o sense a stimuli (i.e. someone drwawing letters on our han) |
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| priamry somatsensory cortex conenctiont o motor cortex |
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| primary somatic snesory cortex relays information to posterior parietl cortex 9araeas 5 and 7) and to secondary somatic senory cortex- superior to lateral fissure. Posteror paritel cortex then goest o motor cortex. Secodnary somatosensory cortex proejciton go to limbic system- thalamus and amygdala (tactile learning and memory) |
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| exticntion double simultaenous stimualtion |
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| lesion in posterior partiel cortex of one side. if you touch each leg seperately you will feel them, hwoehver if legs touchced together, your obyd will ignore the one correspodnign to the lesioned side. |
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| personal neglect syndrome |
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| also has to do with posterior parielt cortex? people cna see both side of the world, but seem to be only aware of one side. |
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| seperate receptors for hto and cold. |
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| in epidermis, fre- nerve endigns- are slowly adapting, small receptor field. Testing by seeing if patient can feel two ends of a safety pin. |
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| family of Trp channels- they have five transmembrane loops- repsodn to either cold or warm temperatures. - ecah one respodns to relatiely narrow window of sensation, above 42 degrees, you feel pain. |
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| family of Trp channels- they have five transmembrane loops- repsodn to either cold or warm temperatures. - ecah one respodns to relatiely narrow window of sensation, above 42 degrees, you feel pain. |
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| temperatuer receptor firing pattern |
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| cold and warm receptors fire constantly at room temperatuer. thermal receptors just change rate of firing when transition from one tempa to another, but are always firing vs. touch receptors which only fire to hcanges in stimui.. |
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afferents enter spian lcord via dorsal root ganglion, run briefly through lissauers tractbefore neterign dorsal hor and synape immediately , deccusates in spinal cord in anterior whtie comomsireu jsut bleow gray matter. Takes two segments for tracts to desscuate compeltely. take up position in atneriorlateral protinfo spina lcord. Spinothalamic tract then proejcts up spinal cord.
commisure jsut bleow cetnral canal . |
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| spinothalamic pathway after level of spinal cord |
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| pain/temperature/CRUDe touch, - enters through dorsal root, project 1-2 segmetns in lissauers tract, synaspes in dorsal horn, deccusate over two segments, and asceneds in spinothalamic tract, ifno form face enters in cervicospinal cord, syanspes in cervical cord decussate and join in spinothalamic tract, travels all the way upto medulla into the pons and up to the thalamus secodn relay point is in teh htalamus- second relay point in thalamus, info from the body is going to ventral posteriorlateral nucelus and posterior limb of internal capsule to the primary somatosensory cortex now on the contralateral side of where snesation was originally stimualetd |
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| trigeminal system for discriminative aspects of pain/temp in face, patwhay |
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trigemianl ganglion is in pons- enters through trigmenal nerve, information descends (even though afferent), to medulla, synapsesi ns pian lnucelsu of trigeminal complex (spinal trigeminal tract). trigmeinal complex has principle nuclus and spinal nucleus and mesecephalic nuclus. Syanpses in trigeminal nuclus of complx, deccusates in caudal medulla and ascends thorugh the trigeminal thalamic tract, up to the ventral posterior medial nucelesu of the thalamus- out to primary somatosensory cortex.
lesions in lateral side of medulla- ipsilateral face weakness. Lesions in medial side= contralateral |
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| somatotropic organization ofSTTs in spinal cord |
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nerve geos as far as
it can go post decussation, before gets stopped by alteral edge of spinal cord- so ifno from legs is going to be most lateral, and info from arm and body will ahve to be medial. Priamry afferents decussate from dorsal horn- legs lateral and upper body medial, stays this way all the way up to thalamus- projectiosn through posterior limb of itnernal capsule, until legs end up on emdial surface of somatosensory cortex and arms and body lateral |
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| mesensephalci tract of trigeminal nucleus |
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| proprioception for jaw and mouth |
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| thalmic relays of the s omatosensorystyem |
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| Thalamus- ventral posterior lateral nuculs receives input form medial leminiscus and spinothalamic tract, the ventral posteirorm edial nuculs receives inptu form the trigeminal limniscus adn triegmnothalamic tract and trigeminal elmniscus. |
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| blood supply to dcmls and stt |
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dorsal columns initially perfused by posterior spinal artery, as go up neuraxis and dorsal nuclei decussate and form medial lemniscus - then perfused by anterior spinal artery.
STT tract- initially perfused by psoterior spinal artery , as ascend gets perfused by vertebral artery and eventually by PICA (posterior inferio cerebral artery) (dont memorize necessarily) |
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| if hae lesioan t c5 wont feel loss of pain and temeprature until c7, due to decussation. |
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| DCMLS/stt/cst relationship |
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| in order to hae sypstoms on samesideo f the body need to havve lesion on above the medulla . symtposm on opposite side of body,lesion wouldh ave to be below medulla in spinal cord. In rostral medulla- they are relatively far from eachother, however as you move up pathways becoem closer. MOre likely taht in pons or midbrain that a lesion might take all of them out. |
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dissociated sensory loss- whole right half of patienst spian lcord has been affected, causing loss of pain and temperature on left side, and loss of touch and vibration on right side of body. Loss of pain and temperature two semgents elow, and loss of touch and on same level.
ipsilateral loss of motor. |
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each of ous is bornw with basci siomatotopci plan of body inrain in cortex. Een if person is bornw ithout limb there wil lbe a aprt of the cotex dedicated to that lim for somatosensory input. That basic plan can be altered by use or disusse. -
cells that wire together /fire together- if you were to fuse to of yoru digits together, representation of cortex digits would beocme melded into one single representation (in syndactytyly- congenital fusion fo teh digits)- after surgery toseperate digits- the areas start to distinguish from one another. |
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| input from that old area would be taken over by areas of the body. |
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| can still sense their arm/limb (even though amputated) being stimulated and have activity for that sensation to go away. When area of brain is taken over by other part, they feel stimulation of amputated part when invading aprt is stimualted. |
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