Greg K. Essick

Tactile motion activates the human middle temporal/V5 (MT/V5) complex.

The human middle temporal/V5 complex (hMT/V5) plays a central role in the perception of visual motion. This region is considered a unimodal visual area with little direct involvement of other sensory modalities. The current study uses H215O PET to test whether tactile motion influences the activity of hMT/V5. Regional cerebral blood flow (rCBF) within hMT/V5 was estimated in eight subjects in separate tactile motion and visual motion conditions, each contrasted with a resting, control. The tactile motion condition involved a brush stroked proximal‐to‐distal along the volar forearm and palm, while the subject attended to the stimulus with closed eyes. The visual motion condition consisted of low contrast, grey‐scale rings radiating at 15°/s from a central point, upon which the subject was instructed to fixate. The location of hMT/V5 was defined for each subject separately as the local maximum of rCBF change during the visual motion condition (vs. control). The average change in rCBF within spherical regions of interest at each peak revealed significant bilateral activation of hMT/V5 in the tactile motion condition contrasted with a second, independent set of control scans. Additionally, a single subject received a sufficient number of scans to perform a pixel‐wise, within‐subject analysis. His functional images were coregistered to his anatomical MRI. In this subject, tactile motion produced a significant increase in rCBF that directly overlapped a region activated by visual motion at the posterior continuance of the inferior temporal sulcus, consistent with the known location of hMT/V5. These results suggest involvement of the hMT/V5 complex in tactile motion processing.

Quantitative assessment of pleasant touch

The hedonic attributes of tactile stimulation are important to ones quality of life, yet they have rarely been studied scientifically. The earliest experimental investigations suggested soft and smooth materials as pleasant, those that were stiff, rough, or coarse as unpleasant. More recent studies conducted by the authors and described herein obtained ratings of pleasantness of different textured materials stroked across the skin of multiple body sites at controlled velocities and forces of application. Statistically significant interactions between materials, sites, velocities, forces and subject sex attest to the complexity of the percept. Less pleasant percepts arose from stimuli that were rougher. However, the difficulty in making further general statements regarding hedonic touch raises questions as to whether the body surface can be mapped affectively in a meaningful manner with a single stimulus and indeed whether pleasantness-to-touch can be viewed as a unidimensional construct.

Psychophysical assessment of the affective components of non-painful touch.

A novel psychophysical procedure for the evaluation of the affective components of touch was developed. A fabric material was stroked across the test site at a controlled direction and velocity, after which the subject provided a numerical estimate of pleasantness. Significant differences were detected for the sites tested (FACE vs ARM), the fabric materials used (VELVET, COTTON and PLASTIC MESH), and the velocity of motion (0.5, 5 and 50 cm/s). Attesting to their validity, estimates of pleasantness correlated negatively with estimates of unpleasantness obtained for the same stimuli. Moreover, subjects were reasonably consistent in their ratings upon stimulus replication. These findings demonstrate that the hedonic qualities of touch can be psychophysically evaluated, and that valid and reliable estimates are obtained.

Human cortical representation of oral temperature

The temperature of foods and fluids is a major factor that determines their pleasantness and acceptability. Studies of nonhuman primates have shown that many neurons in cortical taste areas receive and process not only chemosensory inputs, but oral thermosensory (temperature) inputs as well. We investigated whether changes in oral temperature activate these areas in humans, or middle or posterior insular cortex, the areas most frequently identified for the encoding of temperature information from the human hand. In the fMRI study we identified areas of activation in response to innocuous, temperature-controlled (cooled and warmed, 5, 20 and 50 degrees C) liquid introduced into the mouth. The oral temperature stimuli activated the insular taste cortex (identified by glucose taste stimuli), a part of the somatosensory cortex, the orbitofrontal cortex, the anterior cingulate cortex, and the ventral striatum. Brain regions where activations correlated with the pleasantness ratings of the oral temperature stimuli included the orbitofrontal cortex and pregenual cingulate cortex. We conclude that a network of taste- and reward-responsive regions of the human brain is also activated by intra-oral thermal stimulation, and that the pleasant subjective states elicited by oral thermal stimuli are correlated with the activations in the orbitofrontal cortex and pregenual cingulate cortex. Thus the pleasantness of oral temperature is represented in brain regions shown in previous studies to represent the pleasantness of the taste and flavour of food. Bringing together these different oral representations in the same brain regions may enable particular combinations to influence the pleasantness of foods.

The development and validation of sensory and emotional scales of touch perception

No comprehensive language exists that describes the experience of touch. Three experiments were conducted to take steps toward establishing a touch lexicon. In Experiment I, 49 participants rated how well 262 adjectives described sensory, emotional and evaluative aspects of touch. In Experiment II, participants rated pairwise dissimilarities of the most descriptive words of the set. Multidimensional scaling (MDS) solutions representing semantic–perceptual spaces underlying the words resulted in a touch perception task (TPT) consisting of 26 ‘sensory’ attributes (e.g., bumpiness) and 14 ‘emotional’ attributes (e.g., pleasurable). In Experiment III, 40 participants used the TPT to rate unseen textured materials that were moved actively or received passively against the index fingerpad, volar forearm, and two underarm sites. MDS confirmed similar semantic–perceptual structures in Experiments II and III. Factor analysis of Experiment III data decomposed the sensory attribute ratings into factors labeled Roughness, Slip, Pile and Firmness, and the emotional attribute ratings into Comfort and Arousal factors. Factor scores varied among materials and sites. Greater intensity of sensory and emotional responses were reported when participants passively, as opposed to actively, received stimuli. The sensitivity of the TPT in identifying body site and mode of touch-related perceptual differences affirms the validity and utility of this novel linguistic/perceptual tool.

Perioral somesthetic sensibility : do the skin of the lower face and the midface exhibit comparable sensitivity ?

Studies of the perioral somatosensory capacities of neurologically normal adults were reviewed to determine whether sensitivities within the mental and infraorbital nerve distributions are comparable. It was found that tactile detection sensitivity, spatial acuity, and sensitivity to warmth are greater on skin sites located on the midface than on the lower face. In contrast, sensitivity to direction of motion and to differences in surface texture may be greater on skin sites located on the lower face. The literature further suggests that sensitivity within the distribution of each nerve varies appreciably. For example, the vermilion of the lips exhibits considerably greater vibrotactile detection sensitivity, spatial acuity, and sensitivity to direction of motion than does the perioral hairy skin. In addition, spatial acuity is notably greater on midline structures. These findings suggest that knowledge of the patterns of spatial variations in perioral tactile sensibilities can be effectively used during neurosensory examination to select control skin sites for comparison with areas of suspected neurosensory impairment and to distinguish apparent pathological alterations in tactile sensitivity from normal regional differences that characterize the perioral complex.

Three-dimensional nasolabial displacement during movement in repaired cleft lip and palate patients

The objective of this study was two‐fold: (1) to explore the suitability of a novel modified Procrustes fit method to adjust data for head motion during instructed facial movements, and (2) to compare the adjusted data among repaired unilateral (n = 4) and bilateral (n = 5) cleft lip and palate patients and noncleft control subjects (n = 50). Using a video‐based tracking system, three‐dimensional displacement of 14 well‐defined nasolabial landmarks was measured during four set facial animations without controlling for head motion. The modified Procrustes fit method eliminated the contributions of head motion by matching the most stable landmarks of each video‐recorded frame of the face during function to frames at rest. Its effectiveness was found to approximate that of a previous method (i.e., use of a maxillary occlusal splint to which stable dentition‐based markers were attached). Data from both the unilateral and bilateral cleft lip and palate patients fell outside the normal range of maximum displacements and of asymmetry, and individual patients demonstrated greater right‐versus‐left asymmetry in maximum displacement than did individual noncleft subjects. It is concluded that the modified Procrustes fit method is fast, is easy to apply, and allows subjects to move the head naturally without the inconvenience of a splint while facial movement data are being collected. Results obtained using this method support the view that facial movements in cleft patients may be severely hampered and that assessment of facial animation should be strongly considered when contemplating surgical lip revisions. (Plast. Reconstr. Surg. 105: 1273, 2000.)

Functional Outcomes of Cleft Lip Surgery. Part I: Study Design and Surgeon Ratings of Lip Disability and Need for Lip Revision

Objective: Children with a cleft of the upper lip exhibit obvious facial disfigurement. Many require multiple lip surgeries for an optimal esthetic result. However, because the decision for lip revision is based on subjective clinical criteria, clinicians may disagree on whether these surgeries should be performed. To establish more reliable, functionally relevant outcome criteria for evaluation and treatment planning, a clinical trial currently is in progress. In this article, the design of the clinical trial is described and results of a study on subjective evaluations of facial form by surgeons for or against the need for lip revision surgery are presented. Design: Parallel, three-group, nonrandomized clinical trial and subjective evaluations/ratings of facial views by surgeons. Subjects: For the clinical trial, children with repaired cleft lip and palate scheduled for a secondary lip revision, children with repaired cleft lip and palate who did not have lip revision, and noncleft children. For the subjective evaluations, surgeons’ facial ratings of 21 children with repaired cleft lip. Analysis: Descriptive and Kappa statistics assessing the concordance of surgeons’ ratings of (a) repeated facial views and (b) a recommendation of revision on viewing the prerevision and postrevision views. Results: The surgeons’ consistency in rating repeated views was moderate to excellent; however, agreement among the surgeons when rating individual participants was low to moderate. Conclusions: The findings suggest that the agreement among surgeons was poor and support the need for more objective measures to assess the need for revision surgery.

Site-dependent and subject-related variations in perioral thermal sensitivity.

The Marstock method of limits was used to obtain thresholds for detection of cooling, warming, cold pain and heat pain for 34 young adults, upon eight spatially matched sites on the left and right sides of the face, the right ventral forearm and the scalp. Male and female subjects were tested by both a male and a female experimenter. Neither the experimenter nor the gender of the subject individually influenced the thresholds. The thermal thresholds varied greatly across facial sites: sixfold and tenfold for cool and warmth, respectively, from the most sensitive sites on the vermilion to the least sensitive facial site, the preauricular skin. Warm thresholds were 68% higher than cool thresholds, on average, and 12% higher on the left compared to the right side of the face. The mean cold pain threshold increased from 21.0°C on the hairy upper lip to 17.8°C on the preauricular skin. Sites on the upper lip were also most sensitive to noxious heat with pain thresholds of 42–43°C. The scalp was notably insensitive to innocuous and noxious changes in temperature. For the sensations of nonpainful cool and warmth, the more sensitive a site, the less the estimates of the thresholds differed between subjects. In contrast, for heat pain, the more sensitive a site, the more the estimates differed between subjects. Subjects who were relatively more sensitive to cool tended to be relatively more sensitive to warmth. Subjects’ sensitivities to nonpainful cool and warmth were less predictive of their sensitivities to painful cold and heat, respectively. Short-term within-subject variability increased with the magnitude of the thresholds. The lower the threshold, the more similar were repeated measurements of it, within a 5–25 s period.

Sleep apnea symptoms and risk of temporomandibular disorder: OPPERA cohort

The authors tested the hypothesis that obstructive sleep apnea (OSA) signs/symptoms are associated with the occurrence of temporomandibular disorder (TMD), using the OPPERA prospective cohort study of adults aged 18 to 44 years at enrollment (n = 2,604) and the OPPERA case-control study of chronic TMD (n = 1,716). In both the OPPERA cohort and case-control studies, TMD was examiner determined according to established research diagnostic criteria. People were considered to have high likelihood of OSA if they reported a history of sleep apnea or ≥ 2 hallmarks of OSA: loud snoring, daytime sleepiness, witnessed apnea, and hypertension. Cox proportional hazards regression estimated hazard ratios (HRs) and 95% confidence limits (CL) for first-onset TMD. Logistic regression estimated odds ratios (OR) and 95% CL for chronic TMD. In the cohort, 248 individuals developed first-onset TMD during the median 2.8-year follow-up. High likelihood of OSA was associated with greater incidence of first-onset TMD (adjusted HR = 1.73; 95% CL, 1.14, 2.62). In the case-control study, high likelihood of OSA was associated with higher odds of chronic TMD (adjusted OR = 3.63; 95% CL, 2.03, 6.52). Both studies supported a significant association of OSA symptoms and TMD, with prospective cohort evidence finding that OSA symptoms preceded first-onset TMD.