Biomedical subjects

Greg Essick

Publications and source records attributed to Greg Essick.

6 recordsLinked to original sources

PubMed2006

Oral hydration, parotid salivation and the perceived pleasantness of small water volumes.

Previous studies have suggested that the preference for drinking cold water is increased when the drinker has a dry mouth. In a first experiment, we investigated whether a positive shift in preference would occur for small water volumes (0.75 ml and 1.5 ml) at 8, 16 or 25 degrees C, delivered into a mouth that had been dried using a warmed airflow, versus a normally hydrated mouth. Subjects rated the perceived wetness (or dryness) of their mouth, and the perceived pleasantness (or unpleasantness) of the water samples, using a labeled magnitude scale. Cooler water samples were preferred, and consistent with previous research, this preference was slightly enhanced when the subject's mouth was dried. The coldest water sample led to significantly wetter mouthfeel than the other two less cold samples, consistent with the possibility that the coldest water increased the rate of salivation. However, a second experiment found that although the rate of parotid salivation was increased if the mouth had been dried using a warm airflow, the different water temperatures did not induce different rates of parotid salivation. This indicates that enhanced preference for cold water when the mouth is dry is not invariably based in the reward gained from mouth rewetting via increased parotid saliva flow.

Adult↗

PubMed2006

Validation of a handheld display device for an expandable labeled magnitude scale (LMS).

Palmtop computers provide a possible avenue for the convenient collection of subjective ratings from individuals outside of a fixed laboratory setting. One disadvantage of these computers is the small size of their display screens, which may reduce the resolution of responses available as compared with standard display screens. One plausible solution to this problem is to use a scale that expands contingent on an initial response made by the subject, so that the final response is made from a scale with finer resolution. To validate this approach, we compared taste intensity judgments of six sucrose solutions (0.03, 0.06, 0.12, 0.24, 0.48, and 0.96 M), using a labeled magnitude scale either presented in expandable form on a palmtop computer (Palm scale) or in conventional (nonexpandable) form on a standard 17'' PC monitor (PC scale). Twenty-four subjects rated all six sucrose solutions thrice, using both scale types, the different scales being used on different days of testing. The scales led to very similar taste intensity ratings at all but the lowest concentration, which was rated less intense on the Palm scale. The Palm scale was used with slightly less precision than the PC scale for the weakest solution concentrations. In summary, the responses of the two scales were similar enough to validate the use of the expandable scale on the palmtop computer outside the laboratory setting.

Adult↗

PubMed2006

Thermally evoked parotid salivation.

Parotid salivation is known to be influenced by the temperature of liquids moved around the mouth. Here we investigated the ability of non-liquid thermal stimuli to change the rate of salivation. Unilateral parotid saliva was collected using a Lashley Cup from 12 normally hydrated subjects. Thermal stimuli were delivered through a copper tube, in which temperature-controlled water flowed, resting statically on the anterior tongue. During separate trials, the tube was 10, 22, or 44 degrees C, or the resting temperature of the tongue (or hypothenar of the hand, the control site). On each trial, the unstimulated salivation rate was first measured for 6 min while the subject remained seated with the mouth closed. Subsequently, salivation was measured for 6 min during application of the thermal stimulus. The tube was then removed for 1-2 min before the next trial. During the trials, subjects repeatedly rated the subjective temperature of the tongue (or hypothenar) and its perceived wetness/dryness. Stimulated salivation, expressed as a proportion of the previously measured unstimulated salivation, differed among body sites and temperatures (P<0.03). A significant increase in salivation was seen only for the 10 degrees C stimulus applied to the tongue. Wetness ratings and salivation rates were positively correlated, albeit weakly. These results demonstrate that temperature-evoked changes in parotid salivation do not require the unique spatiotemporal dynamics of the tongue and jaw movements in wetting the oral mucosa.

Adult↗

PubMed2006

Qualitative descriptors used by patients following orthognathic surgery to portray altered sensation.

PURPOSE: Following orthognathic surgery, patients use qualitatively different words to describe the altered sensation on their face that results from tissue inflammation and nerve injury. These words indicate normal, hypoesthetic, paresthetic, and dysesthetic sensations, and reflect the intrusiveness of the alteration. Our intent was to study the words chosen by patients from a standardized list to characterize sensory recovery during the first 6 months after surgery and to examine whether patients who underwent different surgical procedures tended to choose different sets of words. PATIENTS AND METHODS: Patients' selections from a list of 27 words that described their assessment of spontaneous and evoked facial sensations were obtained before surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. Data were obtained from 146 patients enrolled in a randomized controlled clinical trial designed to evaluate the potential of sensory retraining in the rehabilitation of patients who experience impairment in sensory function after nerve injury. Mantel Haenszel general correlation and row mean score statistics were used to assess the association between time and word choice and to compare the word choice categories of 4 surgical groups: bilateral sagittal split osteotomy (BSSO) only, with or without genioplasty; BSSO + Le Fort I, with or without genioplasty. RESULTS: In general, the number of words selected to describe the alteration in sensation decreased over time, as did the intrusiveness of the category of words chosen. However, the intrusiveness remained the same or worsened from 1 week to 6 months for 32% of patients. With increased time after surgery, the percentage of patients who reported altered evoked sensations exceeded the percentage who reported spontaneous sensations. For example, at 6 months the altered sensation of 66% of the patients was classified in the paresthesia and dysesthesia categories by the evoked assessment of sensation; whereas, that of only 47% of the patients were classified as such by the spontaneous assessment. The addition of Le Fort I to BSSO did not affect the way patients reported altered sensation on their lower face. Hypoesthesia and paresthesia, but not dysesthesia, were less of a problem on the midface than on the lower face after BSSO + Le Fort I. Patients who had genioplasty more frequently chose descriptors for the lower face that reflected soft tissue trauma and inflammation ("swollen," "tender," and "burning") than patients without genioplasty; however, this difference decreased with time after surgery. CONCLUSION: The current findings indicate that patients' selection of words differentiates individuals who experienced only a simple loss in sensation (ie, present negative symptoms), those who experienced active sensations that are not normally present (ie, present positive symptoms), and those whose active sensations are additionally uncomfortable or painful. It is possible that continued study of the latter group of patients will reveal patterns of word usage that predict poor long-term recovery and disabling sensory disorders.

Adolescent↗

PubMed2002

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 degrees /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.

Adult↗

PubMedDate not supplied

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 degrees C on the hairy upper lip to 17.8 degrees C on the preauricular skin. Sites on the upper lip were also most sensitive to noxious heat with pain thresholds of 42-43 degrees 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.

Adult↗