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PubMedDate not supplied

Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To evaluate the effect of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) on corneal sensation. SETTING: Eye Institute, Medical School of the University of Crete, Heraklion, Greece, and Orasis, Hellenic Eye Center of Athens, Greece. METHODS: In a masked study, corneal sensation was measured with the Cochet-Bonnet aesthesiometer in 40 consecutive patients 6 to 12 months following PRK and LASIK (60 mm constitutes normal reading and < 40 mm, abnormal). RESULTS: After 6 to 12 months, the mean corneal sensation following PRK was 39.2 mm (range 30 to 55 mm) (mean 9.5 months) and after LASIK, 53.6 mm (range 40 to 60 mm) (mean 9.3 months). The mean correction attempted for PRK was 7.05 diopters (D) (range 2.5 to 12.0 D) and for LASIK, 11.71 D (range 6.0 to 20.0 D). CONCLUSION: In this group of patients, with correction of primarily severe myopia, corneal sensation was significantly greater after LASIK than after PRK.

Adult↗
PubMedDate not supplied

Selective attention for hyperventilatory sensations in panic disorder.

According to cognitive theories, panic patients are assumed to display selective attention for feared bodily sensations. To date there has only been indirect evidence for this based on performance on reaction time tasks such as the modified Stroop task and the dot probe detection task. In the present study a more direct attempt was made to investigate whether panic patients show selective attention for feared sensations, in particular hyperventilatory sensations. A group of patients with panic disorder and a group of normal controls were compared on their performance on a reaction time task in which tones of different length had to be discriminated. During the task subjects were asked either to hyperventilate, to overbreathe under isocapnic conditions, or to make a neutral movement. No evidence for selective attention for hyperventilatory sensations was found. The article also discusses whether lack of finding interference during hyperventilation might be due to methodological issues.

Adult↗
PubMed1997

The genetic correlation between impulsivity and sensation seeking traits.

A number of studies have demonstrated associations between sensation seeking traits and measures of impulsivity. This study examined contributions to the observed correlations between imupulsivity and sensation seeking traits. Fifty-seven pairs of identical and 49 pairs of fraternal twins who were reared apart and 90 individuals who also participated in the Minnesota Study of Twins Reared Apart completed the Control scale of the Multidimensional Personality Questionnaire (MPQ; Tellegen, 1982) and the four subscales of the Sensation Seeking Scale (SSS; Zuckerman, 1979). Consistent with previous studies, the Control scale was significantly correlated with the SSS. A Cholesky decomposition of the data indicated that the phenotypic correlations between the Control scale and the four subscales of the SSS were mediated almost entirely by genetic factors. In the final reduced model the proportion of the genetic variance of the Control scale in common with the SSS was estimated as 55%, and the rest of the genetic variance (45%) was attributed to the genetic variance specific to the Control scale. The results emphasize the importance of common biological mechanisms underlying associations between impulsivity and sensation seeking traits.

Adolescent↗
PubMed2000

Greater sensitivity to subjective effects of nicotine in nonsmokers high in sensation seeking.

The personality characteristic of sensation seeking is associated with risk of smoking, perhaps because of greater initial sensitivity to nicotine. Young healthy nonsmokers (N = 37) were administered 0, 10, and 20 microg/kg nicotine by nasal spray in 3 separate sessions, and subjective responses were assessed. Sensation-Seeking Scale (SSS) scores were then correlated with these responses. A comparison group of smokers (N = 55) was included to determine whether sensation seeking was associated specifically with initial sensitivity to nicotine or with general sensitivity regardless of past nicotine exposure. SSS subscales, particularly Experience Seeking and Disinhibition, were correlated with subjective responses to nicotine in nonsmokers but generally not in smokers. These findings indicate that sensation seeking is associated with greater initial sensitivity to nicotine's subjective effects and may provide directions for further study of individual-differences characteristics that predispose people to the risk of becoming smokers.

Adult↗
PubMed1999

Physiological arousal and sensation-seeking in female fruit machine gamblers.

AIMS: To examine changes in physiological arousal, as indexed by heart rate, during fruit machine gambling while controlling for the confounding effect of movement and as a function of winning and losing, and to examine relationships between sensation-seeking, self-reported arousal during gambling, heart rate during gambling and frequency of gambling. SAMPLE, DESIGN AND MEASUREMENTS: Heart rate and subjective arousal were recorded in a sample of 32 female fruit machine players before, during and after the gambling process. At baseline measures were taken of sensation-seeking, self-reported arousal during gambling and frequency of gambling. A simulation of the behaviour used to operate fruit machines was used during baseline measurement. FINDINGS: Significant increases in heart-rate over movement controlled baselines were observed within participants during gambling, but only in those who won during play. No correlations between HR levels and subjective arousal were found. However, striking negative correlations between sensation-seeking and frequency of gambling, and between subjective arousal and frequency were present. CONCLUSIONS: Gambling alone is not enough to induce increases in HR levels for female fruit machine gamblers; the experience of winning or the anticipation of that experience is necessary to increase HR levels. In addition sensation-seeking appears to be negatively associated with this kind of gambling behaviour.

Adult↗
PubMed1981

Wundt's views on sensations of innervation: a reevaluation.

It is sometimes stated that Wundt believed in the primacy of 'sensations of innervation' in the control of eye and limb position, to the exclusion of afferent feedback. Wundt's own statements on the subject are traced through the six editions of the Grundzüge: he believed that sensations of innervation were a contributory factor along with peripheral feedback; but in the fourth edition he dropped the term and subsumed them under 'central sensations of senses', because increased neurophysiological knowledge made a literal interpretation of the original term impossible. In the fifth edition he developed a more precise model of central processes, described as 'sensory costimulation', and an additional idea of 'reproduced' or conditioned sensations. He mentions clinical evidence on the perception of eye and limb position of weight by paralysed and other subjects. This evidence is discussed in relation to modern theories. It is concluded that Wundt's later theories have some similarities with modern "hybrid' theories of efference-contingent afference.

Afferent Pathways↗
PubMed2001

Changes in postural control in healthy elderly subjects are related to vibration sensation, vision and vestibular asymmetry.

The aim of this study was to analyze the composition of sway in adults and "healthy" elderly people and to evaluate the influence of vibration sensation and asymmetric vestibular function on the sway pattern. Ten adults with a mean age of 37.5 years and 40 healthy senior citizens with a mean age of 74.6 years living independently in the community were studied. Vibration-induced body sway was measured on a force platform. The sway was analyzed and separated into its high and low frequency components above and below 0.1 Hz, respectively. Additionally the elderly subjects were observed for the occurrence of spontaneous gaze and head shake-induced nystagmus using infrared charge-coupled device cameras and the vibration perception in the lower limbs was tested with a tuning fork. Vibration perception was the major determinant for postural control in the elderly subjects. Postural control among the elderly subjects with intact vibration perception in their lower limbs was very similar to that of the adults. The elderly subjects with impaired vibration sensation had increased high frequency sway compared to adults and the elderly subjects with intact sensation. Regardless of the strong influence of vibration sensation on postural control, asymmetric vestibular function might also be a contributing factor to postural instability in the elderly. Age per se had little effect on the outcome of the tests except that the elderly subjects had diminished ability to use visual cues to reduce postural sway. We concluded that sensory status in the lower limbs is of utmost importance for postural control in the elderly. Rehabilitation programs for senior citizens should therefore include exercises to preserve recognition of body motion by the lower limbs. Exercises to facilitate vestibular compensation could be useful for elderly people with vestibular dysfunction.

Adult↗
PubMed2002

Intramuscular sensation in conscious human subjects: a qualitative and quantitative study utilizing signal detection theory methodology.

To investigate whether human subjects could consciously perceive different levels of intramuscular sensation, EMG needle electrodes were inserted into the forearm extensor musculature. Qualitative descriptions of the types of sensations evoked at various current intensities were recorded. A series of preliminary experiments was performed in order to determine the optimum waveform, current intensity, duration and separation between adjacent current pairs that could reliably be discriminated by conscious human subjects. The methodology of signal detection theory was utilized to obtain the discrimination measure, d' (d prime). Values of d' were obtained for sequential blocks of trials consisting of randomly delivered blocks of 50 "strong" and 50 "weak" stimuli. The ability to discriminate both noxious and non-noxious stimuli was determined using d'. It was demonstrated that human subjects are able to qualitatively describe non-nociceptive sensations elicited by low levels of intramuscular stimulation. Subjects were able to reliably discriminate pairs of electrical stimuli separated in intensity by 0.4 dB over four sequential blocks of trials on the same day and on different days. This work demonstrates that signal detection theory methods can reliably measure sensory discrimination in skeletal muscle, for both noxious and non-noxious levels of electrical stimulation. A protocol is proposed for appropriate future use of this methodology to investigate alterations in muscle sensation following experimental interventions.

Adult↗
PubMed1991

Sensitivity, specificity and predictive value of the sensation of warmth as a method of detecting inadvertent subarachnoid injection of local anaesthetic when performing extradural blocks.

In order to test if the rate of onset of sensation of warmth in the legs after the injection of 0.5% bupivacaine might discriminate between subarachnoid and extradural injection, 150 urological patients were allocated randomly to receive either spinal anaesthesia with isobaric (IS) or hyperbaric (HS) 0.5% bupivacaine, or extradural anaesthesia with isobaric 0.5% bupivacaine. The volume of the local anaesthetic for spinal anaesthesia and for the extradural test dose was 3-4 ml. The patients were asked to report at once if they had a sensation of warmth in the legs during or after injection of local anaesthetic. The mean time to the sensation of warmth was significantly shorter in the spinal groups (80 (SEM 10) s in IS and 76 (8.0) s in HS) than in the extradural group (558 (38) s). However, six patients in the IS and two in the HS group had no sensation of warmth.

Adult↗
PubMed1985

Tympanic membrane sensation.

Sensation from the tympanic membrane is generally believed to be mediated via at least four cranial nerves, some authors describing discrete territories for each of these nerves. The lack of critical evidence for independent sensory areas prompted a clinical study of tympanic membrane sensation in 32 patients having known cranial nerve deficits. Tympanic membrane sensation was tested in four quadrants using a 300 mg bristle under a Zeiss operating microscope. The findings were highly suggestive of a predominantly nociceptive system. Any change relative to the opposite tympanum was usually anaesthesia. No complete trigeminal deficit retained perception in all tympanic quadrants. Facial, glossopharyngeal and vagal deficits alone never affected tympanic sensation. These findings support the trigeminal nerve as the principal sensory nerve to the tympanic membrane, supplemented only inconstantly and incompletely by the other cranial nerves.

Adolescent↗
PubMed1987

Intraneural microstimulation in man. Its relation to specificity of tactile sensations.

Recent advances in knowledge, and controversy, concerning cutaneous mechanoreception are reviewed. In particular, the question of perceptive specificity is discussed in the light of new experimental approaches, namely microneurography and microstimulation of identified tactile units from the glabrous skin of the human hand. Additional data are also presented. It is concluded that the human brain has an exquisite capacity to detect, localize, delineate, and classify sensations from the input of individual tactile units in the glabrous skin of the hand. The physiological specificity of low-threshold mechanoreceptors in the hand, which has been well documented in previous studies, can now be linked to distinct attributes of very simple tactile sensations which subjects report when a single afferent is stimulated electrically through an intraneural microelectrode. This conclusion does not conflict with the concept that the brain normally makes use of temporal and spatial patterns of impulses from a large number of receptors of various types to form more complex tactile percepts, such as in the recognition of texture, but the microstimulation data demonstrate that particular patterns of nerve impulses are not a necessary determinant of the subjective quality attribute of a simple tactile sensation. On the contrary, the sensations elicited by a train of impulses in a single afferent unit are remarkably distinct and well characterized in a number of respects. A further conclusion is that the afferent inputs are processed differently in tactile subsystems. This observation warrants caution in generalizing results from one system into a common theory of the origin of sensory modality.

Electric Stimulation↗
PubMed2002

Representation of pain and somatic sensation in the human insula: a study of responses to direct electrical cortical stimulation.

We studied painful and non-painful somaesthetic sensations elicited by direct electrical stimulations of the insular cortex performed in 43 patients with drug refractory temporal lobe epilepsy, using stereotactically implanted depth electrodes. Painful sensations were evoked in the upper posterior part of the insular cortex in 14 patients, mostly in the right hemisphere. Non-painful sensations were elicited in the posterior part of the insular cortex in 16 patients, in both hemispheres. Thus, painful and non-painful somaesthetic representations in the human insula overlap. Both types of responses showed a trend toward a somatotopic organization. These results agree with previous anatomical and unit recording studies in monkeys indicating a participation of the posterior part of the insular cortex in processing both noxious and innocuous somaesthetic stimuli. In humans, both a posterior and an anterior pain-related cortical area have been described within the insular cortex using functional imaging. Our results help to define the respective functional roles of these two insular areas. Finally, lateralization in the right hemisphere of sites where painful sensations were evoked is coherent with the hypothesis of a preponderant role of this hemisphere in species survival.

Adult↗
PubMed1976

Breast sensation before and after plastic surgery.

Patients undergoing various plastic surgical procedures on their breasts were studied before and after operations with respect to sensation from crude touch, light pressure, and pain. The more extensive the operation on the breast (the more skin and breast tissue removed) the greater the postoperative decrease in sensation. Reduction mammaplasty and subcutaneous mastectomy were associated with decreased sensation in a significant number of patients. An unexpected finding was that patients having augmentation mammaplasty by either the inframammary or areola route showed a significant decrease in sensation to the nipple and apeola. At two years, 15 percent of the patients still had impaired sensory perception, although crude touch and light pressure appreciation had returned. Many of these patients had normal erectility with normal, and even enhanced, sensuality.

Breast↗
PubMed1978

Use of an innervated skin graft to provide sensation to the reconstructed heel.

An innervated skin graft--a full-thickness skin graft with its nerve supply intact--is presented. In the case described, the sural nerve was preserved and an island of skin supplied by it was transposed to provide sensation to a heel pad, which had first been reconstructed by a cross-thigh flap. This transposed sensation has allowed full activity for 3 years in a young boy wearing normal footwear. This suggests that ulceration of all, or most, heel reconstructions is due to lack of sensation and, further, that the necessary sensation can be provided by this technically simple transposition of an innervated skin graft.

Child↗
PubMed2005

Sensory recovery in the sensate free transverse rectus abdominis myocutaneous flap.

BACKGROUND: Preservation and restoration of sensation to improve the quality of the reconstruction have not always been considered a priority in efforts to reconstruct the breast. Studies have documented spontaneous recovery of sensation in reconstructed breasts, but this recovery was variable and unpredictable. The authors conducted a pilot study to compare sensory recovery in innervated versus noninnervated microsurgical breast reconstruction patients. METHODS: The authors investigated a group of 14 patients who had undergone microsurgical breast reconstruction with a muscle-sparing free transverse rectus abdominis myocutaneous flap. Seven patients had reinnervation of their flaps, and seven did not. The two patient groups were similar in age (mean age, 46 years for the innervated group and 51 years for the noninnervated group) and length of follow-up (mean duration of follow-up, 39 months for the innervated group and 40 months for the noninnervated group). Sensitivity to fine touch was assessed using Semmes-Weinstein monofilaments. By testing over a defined grid and over the entire reconstructed breast, it was possible to develop color maps, or sensory topograms, of the areas sensing different levels of pressure for each patient. The patient's ability to differentiate between hot (60 degrees C) and cold (5 degrees C) was recorded. RESULTS: In a comparison of sensation in flap skin (skin paddle of rectus abdominis myocutaneous flap) with nonflap skin (native breast skin), sensitivity to fine touch was statistically better in (1) innervated flap skin compared with noninnervated flap skin (p = 0.003), (2) innervated nonflap skin compared with noninnervated flap skin (p = 0.006), (3) innervated nonflap skin compared with noninnervated nonflap skin (p = 0.037), and (4) innervated flap skin compared with noninnervated nonflap skin (p = 0.006). Temperature differentiation was significantly better in patients with innervated flaps than in patients with noninnervated flaps in all zones (p = 0.02). These differences persisted beyond a follow-up period of 3 years. CONCLUSIONS: The authors' findings confirm that reinnervation of microsurgically reconstructed breasts achieves sensory recovery that is superior to that in breasts reconstructed without reinnervation. If sensation is important and the anatomical factors are favorable, reinnervation may represent a worthwhile refinement in attempts to achieve normality for patients undergoing breast reconstruction.

Adult↗
PubMed1983

Electrovibration, cutaneous sensation of microampere current.

The human threshold of sensation of 50 Hz current has hitherto been considered to be around 1 mA. A new sensing mechanism is reported which lowers the threshold about 3 decades. It is elicited when the skin slides on the current carrying conductor, and the sensation disappears when the skin is wet. The sensation is a feeling of vibration or increased surface roughness. The sensing mechanism has been shown to be due to electrostatic forces in the skin caused by the electric field in a poorly conducting stratum corneum. The mechanism is primarily potential dependent, and the absolute threshold of sensation has been found to be about 1.5 volt or 0.15 mu A rms at 50 Hz. In practical daily-life situations it is shown that 82% of 40 test subjects were able to sense a current of 2 mu A rms, 50 Hz.

Electrodes↗
PubMed1982

Role of anorectal sensation in preserving continence.

The role of anal sensation in preserving continence was studied in nine healthy volunteers. Objective assessment of sphincter function by manometry and rectal saline infusion was carried out during topical anaesthesia of the anal canal using 5% lignocaine gel and during lubrication with the same amount of inert gel. Anaesthesia successfully abolished anal sensation and reduced both the amplitude and duration of the voluntary squeeze. Basal pressure was unaffected, but the rectal volume required to produce a sustained internal sphincter relaxation was increased. Saline continence was not impaired. Indeed, two subjects, who were previously unable to retain the full 1500 ml of rectally infused saline, did so when the anal canal was anaesthetised. Our findings suggest that anal sensation is not a critical factor in preserving continence. This implies that the incontinence experienced after anorectal surgery or neuropathy cannot be explained by lack of anal sensation alone.

Adult↗
PubMed2003

Cognitive modulation of the cerebral processing of human oesophageal sensation using functional magnetic resonance imaging.

BACKGROUND: While cortical processing of visceral sensation has been described, the role that cognitive factors play in modulating this processing remains unclear. AIM: To investigate how selective and divided attention modulate the cerebral processing of oesophageal sensation. METHODS: In seven healthy volunteers (six males, mean age 33 years; ranging from 24 to 41 years old) from the general community, phasic visual and oesophageal (non-painful balloon distension) stimuli were presented simultaneously. During the selective attention task, subjects were instructed to press a button either to a change in frequency of oesophageal or visual stimuli. During a divided attention task, subjects received simultaneous visual and oesophageal stimuli and were instructed to press a button in response to a change in frequency of both stimuli. RESULTS: Selectively focussing attention on oesophageal stimuli activated the visceral sensory and cognitive neural networks (primary and secondary sensory cortices and anterior cingulate cortex respectively) while selective attention to visual stimuli primarily activated the visual cortex. When attention was divided between the two sensory modalities, more brain regions in the sensory and cognitive domains were utilised to process oesophageal stimuli in comparison to those employed to process visual stimuli (p=0.003). CONCLUSION: Selective and divided attention to visceral stimuli recruits more neural resources in both the sensory and cognitive domains than attention to visual stimuli. We provide neurobiological evidence that demonstrates the biological importance placed on visceral sensations and demonstrate the influence of cognitive factors such as attention on the cerebral processing of visceral sensation.

Adult↗