Touch Discrimination Research Articles

Training of Somatosensory Discrimination After Stroke

Task-specific learning typifies perceptual training but limits rehabilitation of sensory deficit after stroke. We therefore investigated spontaneous and procedurally facilitated transfer of training effects within the somatosensory domain after stroke. Ten single-case, multiple-baseline experiments were conducted with stroke participants who had impaired discrimination of touch or limb-position sense. Each experiment comprised three phases: baseline, stimulus-specific training of the primary discrimination stimulus, and either stimulus-specific training of the transfer stimulus or stimulus-generalization training. Both the trained and transfer stimuli were monitored throughout using quantitative, norm-referenced measures. Data were analyzed using individual time-series analysis and meta-analysis of intervention effects across case experiments. Stimulus-specific training was successful for trained texture and proprioceptive discriminations, but it failed to show spontaneous transfer to related untrained stimuli in the same modality in seven of eight experiments in which this was possible. In contrast, intramodality transfer was obtained with stimulus-generalization training in four of five experiments that investigated stimulus-generalization training of texture discrimination. Findings were confirmed by meta-analysis. Our findings demonstrate generalization of training within a somatosensory modality poststroke, provided that a program designed to enhance transfer is used. This has implications for the design of efficient rehabilitation programs.

Specific changes in somatosensory evoked magnetic fields during recovery from sensorimotor stroke

We studied recovery-induced changes in the responsiveness of the primary somatosensory cortex in stroke patients with sensory and/or motor symptoms. Somatosensory evoked magnetic fields, in response to median nerve stimulation, were recorded in 14 patients with their first symptomatic unilateral stroke 1 to 15 days from the first symptoms and again 2 to 3 months later. Neuronal activity at the contralateral primary somatosensory cortex was modeled with equivalent current dipoles at the peak latencies of the first two cortical deflections at about 20 msec (N1m) and at 28 to 91 msec (P1m). Twenty-three age-matched healthy volunteers, 9 of whom were tested also in serial recordings, served as control subjects. At follow-up, 6 patients showed a significant increase of P1m amplitude, whereas N1m increased only in 1. Clinical improvement of two-point discrimination ability, but not of other basic somatosensory skills, was significantly correlated with the increase of P1m. We conclude that the recovery of discriminative touch after stroke is paralleled by the growth of the P1m somatosensory evoked magnetic field deflection, and we propose that this may reflect re-establishment of lateral inhibitory functions at the primary somatosensory cortex.

Impaired Touch Discrimination After Stroke: A Quantiative Test

The ability to discriminate differences in tactile stimuli, such as textures, is commonly and characteristically impaired after stroke. Assessment of tactile discrimination is cur rently compromised by measures that are not quantitative and standardized, do not as sess active touch sensibility, or are not suitable for use in clinical settings with stroke patients. Therefore, a test that addressed these limitations was developed. The Tac tile Discrimination Test required subjects to discriminate differences in finely graded plastic ridged surfaces using a three-alternative forced choice design. Test-retest reli ability, based on a sample of 35 stroke patients, was high (r = 0.92), and changes of the magnitude of 27 percent spatial increase (PSI) can be detected with 95 percent confidence, which is sufficiently accurate for clinical monitoring. A matched pairs study of 50 stroke and 50 unimpaired subjects found that normal performance scores were contained within the 3-46 PSI range. The conservative criterion of abnormal ity was defined as 46 PSI, with a zone of uncertainty from 31 to 61 PSI. The test dif ferentiated well impaired performance relative to normal standards. These results sup port the application of the Tactile Discrimination Test as a quantitative, standardized measure appropriate for testing stroke patients in clinical settings. Key Words: Cere brovascular disorders—Standardized assessment—Somsatosensory—Tactile—Hand.

Two-point discrimination of itch in patients with atopic dermatitis and healthy subjects.

The ability to perceive two pruritic stimuli as separate depending on the distance between them (two-point discrimination of itch) was determined in a single-blind study of 20 patients with atopic dermatitis and 20 healthy subjects. Itch was induced with pairs of histamine injections (0.1 micrograms each) given on the upper arm, either along its axis (longitudinally within a dermatome) or at right angles to it (transversally involving more than one dermatome). The interinjection distances were varied in 3-cm steps until the shortest distance at which the two itching stimuli could be perceived as separate was found. Pairs consisting of one injection of histamine (0.1 micrograms) and one of saline served as controls. The two-point discrimination of itch was significantly better in the atopic dermatitis patients than in the healthy controls, both longitudinally (atopic dermatitis: median 12 cm, range 3-21 cm; healthy controls: 15 cm, range 9-21; p < 0.01) and transversally (atopic dermatitis: median 6 cm, range 3-18; healthy controls: 12 cm, range 6-21; p < 0.001). The two-point discrimination of itch did not correlate with the subject's age, two-point discrimination of touch, or, for the atopic dermatitis patients, with their eczema scores or serum IgE levels. The quality, intensity or spatial summation of itch did not differ significantly between the two groups of subjects.

Computer-assisted measurement in diabetic patients with and without foot ulceration

Computer-assisted measurement of sensibility was done at four anatomical sites of the foot of patients with diabetes with (19) and without (40) foot ulceration. Cutaneous pressure threshold measurements of patients with diabetes were compared with measurements on 30 patients without diabetes who had nonulcerated feet. Both groups had mean one-point static and moving touch, and two-point discrimination thresholds significantly different from the general population. Computer-assisted sensibility testing demonstrated significantly higher pressure thresholds for one-point static and moving touch and two-point discrimination in the ulcerated compared with the nonulcerated foot of patients with diabetes. This measurement technique is valid for documenting diminished sensation in the foot.

Layer I of primary sensory neocortex: where top-down converges upon bottom-up

A fundamental paradigm shift is underway in the behavioural neurosciences which promotes renewed discussion of neural correlates of conscious sensation. A growing body of evidence that the primary sensory areas are central to conscious processing is inconsistent with conventional bottom-up models of passive sensory transformation. The new paradigm emphasizes the interaction of top-down corticocortical influences with bottom-up sensory feedback. This review develops the new interactive paradigm with respect to the behaviourally relevant N1 component of the somatosensory evoked response in primary somatosensory neocortex which is only observed during conscious states and predicts touch discrimination behaviour. N1 is generated by layer I excitation apparently in response to backward projections from higher order cortical areas. The backward corticocortical projections mediating top-down influences are anatomically concentrated in layer I where they strongly excite the subpopulation of pyramidal neurons with extensive distal apical dendrites. This subpopulation includes the forward-projecting pyramids subserving corticocortical reentrance as well as the corticobulbar projections mediating cortical control over fine sensory-oriented movements. This interactive paradigm views conscious sensation as an active behaviour with the optimal spatial resolution of primary areas serving as the sensory-motor interface at the major convergence point between reentrant bottom-up and top-down pathways. A device is proposed for the reconstruction of cortical sensory processing based upon the central importance of the primary area as the focus of convergent top-down cortical projections.

Neurosensory recovery following the mandibular bilateral sagittal split osteotomy

Purpose: This prospective study evaluated the neurosensory recovery pattern of the inferior alveolar nerve following the bilateral sagittal split osteotomy (BSSO). Patients and Methods: Forty-two consecutive patients undergoing BSSO were studied using five neurosensory tests: 1) static light touch, 2) moving touch discrimination, 3) two-point discrimination, 4) nociception, and 5) thermoreception. Intraoperative assessment of inferior alveolar nerve damage was made; other variables recorded included type of fixation, age, concomitant procedures, advancement vs setback, and magnitude of the movement. A subjective questionnaire was completed by the patient. Results: The variables that affected neurosensory function following BSSO were degree of nerve damage and the amount of time elapsed following surgery. Larger myelinated fibers (A-α) recovered slower and to a lesser degree at all time intervals up to 2 years when compared with small myelinated and unmyelinated nerve fibers. The magnitude of nerve damage directly correlated with early neurosensory deficit, but equalized over time. Conclusion: The long term (6 months and greater) chance for neurosensory recovery is good despite intraoperative nerve manipulation. Patients seem to adapt and report normal neurosensory function even though objective testing indicates continued neurosensory deficit.

Development of locomotion in the rat— Spatiotemporal footfall patterns

Footfall patterns during locomotor ontogeny have been observed in Wistar rats 10–30 days old. These reveal that, even at 22 days, the paw contacts are both spatially and temporally unlike those of the adult. In the adult there is a precise presentation sequence involving early soft contact of tactile sensitive forepaw parts that may be important in tactile locomotor guidance and which is not fully established even at 22–30 days. The hindpaw contact pattern is also not yet adult-like involving a greater incidence of early toe contact. It is suggested that, only after day 15, when the forelimb is no longer the major weight-bearing limb, can it start to be developed for the fine discriminative touch required for tactile guidance of limb placement. Some further time is necessary for adult patterns to be achieved.

Touch Discrimination Ability for Fine Surface Textures and Mechanoreceptor Density

Touch Discrimination Ability for Fine Surface Textures and Mechanoreceptor Density

Touch Discrimination Ability of Humans for Fine Surface Textures

Touch Discrimination Ability of Humans for Fine Surface Textures

The Touch Discrimination Component of Sexual Abuse Prevention Training

The potential negative impact of sexual abuse prevention programs on children remains a central concern in the field of sexual abuse prevention. The purpose of this study was to examine the effectiveness of two prevention programs in improving children's abilities to discriminate between appropriate and inappropriate types of touching. Two hundred sixty-four kindergarten through third-grade children from three public schools in San Diego were randomly assigned by classroom to one of three treatments: (1) a role-play-based sexual abuse prevention program, (2) a multimedia child abuse prevention program, or (3) a control group receiving fire prevention training. The results indicated greater pre- to posttest improvement for the role-play group than for the control group on total correct touch discriminations. Although there is concern that sexual abuse prevention programs may make children suspicious of appropriate touch, the present study found children in the role-play group better able to discriminate appropriate touch after training than before. The results are discussed in light of current findings in the child sexual abuse prevention literature.

Recovery of neurosensory function following orthognathic surgery

The purpose of this study was to prospectively define the recovery of touch discrimination following four commonly performed surgical procedures in 22 consecutive patients with no previous maxillofacial surgery. The surgical groups studied were Le Fort I osteotomy (LEFORT; n = 13), sagittal split ramus osteotomy (SSRO; n = 6), intraoral vertical ramus osteotomy (IVRO; n = 9), and isolated genioplasty (GENIO; n = 5). Neurosensory function was assessed by three different testing modalities which included static light touch (SLT), moving touch discrimination (MTD), and two-point discrimination (TPD). Cutaneous sensation of the lower lip and chin were examined for the mandibular procedures, whereas the infraorbital and upper lip regions were evaluated following maxillary surgery. Immediately following surgery, each group varied in both the incidence and magnitude of neurosensory deficits (NSD). The SSRO group had the highest percentage of sites with immediate postsurgical NSD to both SLT (72%) and MTD (67%), followed by the LEFORT (SLT = 50%, MDT = 58%), GENIO (SLT = 27%, MTD = 6%), and IVRO groups (SLT = 11%, MTD = 18%), respectively. Each group also varied in the severity of the initial postoperative deficit as measured by SLT, with the SSRO group showing the greatest deficit followed by the LEFORT, GENIO, and IVRO groups. During the 6-month recovery period each group approached preoperative levels of sensation at a different rate. The LEFORT group recovered most rapidly, with few anatomic sites showing NSD (SLT = 20%, MTD = 5%) at the 1-month postoperative examination, and the majority of the group (96%) returned to preoperative sensation by 3 months following surgery. The SSRO group recovered more slowly, with approximately half of the group demonstrating a deficit (SLT = 50%, MTD = 59%) at 1 month, which diminished to about one fourth of the sites (SLT = 25%, MTD = 5%) by 3 months. Most of the SSRO group (90%) exhibited no residual deficit 6 months following surgery. The IVRO group had few sites with immediate NSD (SLT = 11%, MTD = 15%). In none of the surgical groups was a statistically significant correlation found between the severity of the initial NSD and length of time to complete recovery.

Group rotation from the bottom up

<h3>ABSTRACT</h3> The somatosensory system decodes a range of tactile stimuli to generate a coherent sense of touch. Discriminative touch of the body depends on signals conveyed from peripheral mechanoreceptors to the brain via the spinal cord dorsal column and its brainstem target the dorsal column nuclei (DCN)^{1, 2}. Models of somatosensation emphasize that fast-conducting low- threshold mechanoreceptors (LTMRs) innervating the skin drive the DCN^{3, 4}. However, post- synaptic dorsal column neurons (PSDCs) within the spinal cord dorsal horn also collect mechanoreceptor signals and form a second major input to the DCN^5–7. The significance of PSDCs and their contributions to the coding of touch have remained unclear since their discovery. Here, we show that direct LTMR inputs to the DCN convey vibrotactile stimuli with high temporal precision, whereas PSDCs primarily encode touch onset and the intensity of sustained contact into the high force range. LTMR and PSDC signals topographically re-align in the DCN to preserve precise spatial detail. Different DCN neuron subtypes have specialized responses that are generated by unique combinations of LTMR and PSDC inputs. Thus, LTMR and PSDC subdivisions of the dorsal column encode different tactile features and differentially converge in the DCN to generate unique ascending sensory processing streams.

Peripheral nerve injuries. Sensation.

The Journal of Bone and Joint Surgery. British volumeVol. 68-B, No. 1 ArticlesFree AccessPeripheral nerve injuries. SensationCB ParryCB ParrySearch for more papers by this authorPublished Online:21 Feb 2018https://doi.org/10.1302/0301-620X.68B1.3941133AboutSectionsPDF/EPUB ToolsAdd to FavouritesDownload CitationsTrack CitationsPermissions ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited ByDifferential recovery of touch thresholds and discriminative touch following nerve repair with focus on time dynamics19 June 2014 | Hand Therapy, Vol. 19, No. 3Periphere NervenläsionenPlaies des nerfs et rééducation de la sensibilitéLong-term results after primary microsurgical repair of ulnar and median nerve injuriesClinical Neurology and Neurosurgery, Vol. 109, No. 3Improved Sensory Relearning after nerve Repair Induced by Selective Temporary Anaesthesia – A New Concept in Hand Rehabilitation29 August 2016 | Journal of Hand Surgery, Vol. 31, No. 2Clinical Nerve Repair and ReconstructionSensory Relearning and Sensory Re-educationAssessment of Outcome After Nerve RepairA new model instrument for outcome after nerve repairHand Clinics, Vol. 19, No. 3Sensory Re-education Today and Tomorrow: A Review of Evolving Concepts26 September 2016 | The British Journal of Hand Therapy, Vol. 8, No. 2A model instrument for the documentation of outcome after nerve repairThe Journal of Hand Surgery, Vol. 25, No. 3Recovery of Sensory and Motor Function After Nerve RepairJournal of Hand Therapy, Vol. 9, No. 4Sensory recovery after median nerve graftingThe Journal of Hand Surgery, Vol. 17, No. 1The assessment of hand function: A critical review of techniquesThe Journal of Hand Surgery, Vol. 14, No. 2 Vol. 68-B, No. 1 Metrics Downloaded 65 times History Published online 21 February 2018 Published in print 1 January 1986 InformationCopyright © 1986, The British Editorial Society of Bone and Joint Surgery: All rights reservedPDF download

Peripheral projections of nerve fibres in the human median nerve

Elementary sensations of definable quality were evoked by intraneural electrical stimulation of sensory units through tungsten microelectrodes inserted in the median nerve of awake human subjects. The most commonly reported sensations were tapping, pressure, dull pain and sharp pain, which correlated with recording from RA units, SA I units, C nociceptors and Aδ nociceptos, respectively. All sensations were projected more often to the fingertips than to the palm. The multifocal projections of sensations recruited by excitation of small groups of neighbouring nerve fibres were significantly more scattered in space than anticipated if these fibres had preserved an orderly intraneural map, implying lack of somatotopy in the nerve. Mean projected field sizes were 3.4 mm 2 for sharp pain, 9.2 mm 2 for tapping/vibration, 29.3 mm 2 for pressure and 35.4 mm 2 for dull pain, and in addition the latter two showed a rising size gradient from fingertip to palm. Consideration of projected field size as a variable in discriminative touch suggests that input from RA units and Aδ nociceptors may be of importance in stimulus localization, while SA I units may play an additional role in two point discrimination.

Somatesthetic recovery following primary somatosensory projection cortex ablations.

Seven rhesus macaque monkeys were trained to discriminate proprioception, vibration, light touch, and two-point discrimination. They then underwent removal of the classical somatosensory lemniscal cortex, areas SI and SII. There was complete loss of proprioceptive and two-point discriminatory ability immediately following surgery, with minimal loss of vibratory discrimination and light touch sensitivity. Following extensive retraining, the animals regained all fine discriminatory ability except for a slight increase of proprioception and two-point discrimination thresholds.

The comparison of two methods of assessing fear and avoidance behavior

The present study evaluated: (a) the reliability of two fear-assessment techniques [Lang and Lazovik's (1963) approach test and Levis' (1969) phobic test apparatus]; (b) test-retest changes in those measures; and, (c) the sensitivity of response latency as a fear measure, as a function of the two methods of assessing fear. Forty-eight college females were exposed to one of four test-retest snake-exposure conditions: repeated testing on the phobic test apparatus, repeated testing on the traditional approach test, and counterbalanced testing on both test methods. The results indicated (a) equally reliable measurements in all four groups on approach and pulse rate scores, (b) equivalent repeated-testing changes in avoidance behavior, pulse rate, and self-reported fear, and (c) discrimination of touch and no-touch Ss on the basis of response latency in both test methods.

Proprioception and vibration sensibility discrimination in the absence of the posterior columns.

THE SENSORY system carried in the dorsal columns and medial lemniscus has been clearly shown by Mountcastle and others 1,2 to have the neurophysiological attributes essential for discriminative touch: its neurons are somatotopically organized at each successive level and subtend small contralateral peripheral receptive fields that are activated by mode specific mechanoreceptive stimuli. The security of synaptic transmission of this afferent information concerning the spatial and temporal sequence of stimuli is its most distinguishing feature. The ability to detect a change in the position of a limb and the ability to detect vibration have been considered functions of this sensory system. 3,4 Pathological lesions confined solely to the dorsal columns are believed to affect both modalities. However, there have been numerous reports of patients with dorsal funicular lesions in whom vibration sensibility and proprioception were not affected to the same degree, and many in whom no clinical deficit was