Biomedical subjects

P F Kent

Publications and source records attributed to P F Kent.

12 recordsLinked to original sources

PubMed2000

Odorant quality perception: a metric individual differences approach.

Perceptual spaces, in which similar stimuli are located close to each other and dissimilar stimuli are located far apart, have aided in the understanding of the physiological and psychological bases for sensory quality coding. Differences in perception between individuals should be reflected by differences in the spatial relationships between stimuli. If the dimensionality of the perceptual space is small (e.g., color space), individual differences that reflect specific pathologies are readily apparent from visual inspection. On the other hand, if the dimensionality of the perceptual space is large (as is proposed for odor space), visual inspection alone may not reveal individual differences in quality perception. The present work presents an information-theory-based method for quantifying individual differences in quality perception from perceptual confusion matrices. The ability of this method to quantify individual differences in quality perception is shown in a hypothetical example of specific anosmia. Finally, the method is applied to the examination of intrasubject consistency of odorant quality perception.

Adult↗

PubMed1998

The olfactory loss that accompanies an HIV infection.

A number of studies have shown that HIV infection is associated with decreased olfactory ability. Additionally, it has been hypothesized that a reduced odorant identification may precede the advent of AIDS Dementia Complex (ADC). However, it is not known whether changes in olfactory ability are a manifestation of neurocognitive decline which may precede the appearance of AIDS Dementia Complex, damage to the peripheral olfactory system from opportunistic infection, or whether olfactory structures have a particular sensitivity to HIV. These issues were addressed in a cross-sectional study examining variability in the neuropsychological, neurological, otolaryngological, auditory, and olfactory status in HIV-positive subjects. A stepwise regression provided evidence that the ability to identify odorants was influenced by age, nasal structure and pathology, neurocognitive ability, and level of AIDS Dementia Complex. On the other hand, only nasal pathologies accounted for the variability in olfactory thresholds. These data suggest that identification and thresholds tests may reflect different olfactory pathologies. Additionally, these data suggest at least part of the decline in olfactory ability accompanying an HIV infection may be secondary to nasal pathologies. Because of their rapidly changing neurocognitive status, HIV-positive patients represent an excellent group in which to study the determinants of olfactory ability.

Adult↗

PubMed1997

Effect of nasal dilators on perceived odor intensity.

Subjects wearing nasal dilators rated olfactory stimuli as being more intense compared with ratings done without nasal expansion. The results support a perceptual constancy model in olfaction.

Administration, Intranasal↗

PubMed1996

The aging olfactory epithelium: neurogenesis, response to damage, and odorant-induced activity.

Olfactory epithelium retains the capacity to recover anatomically after damage well into adult life and perhaps throughout its duration. None the less, olfactory dysfunctions have been reported widely for elderly humans. The present study investigates the effects of aging on the neurophysiological and anatomical status of the olfactory epithelium in barrier-raised Fischer 344X Brown Norway F1 hybrid rats at 7, 10, 25 and 32/35 months old. The posterior part of the olfactory epithelium in 32/35-month-old rats is well preserved. Globose basal cells are dividing, and new neurons are being born even at this advanced age. None the less, the numbers of proliferating basal cells and immature, GAP-43 (+) neurons are significantly decreased. Neurophysiological status was evaluated using voltage-sensitive dye techniques to assess inherent patterns of odorant-induced activity in the epithelium lining the septum and the medial surface of the turbinates. In middle and posterior zones of the epithelium, there were neither age-related changes in overall responsivity of this part of the olfactory epithelium to any of five odorants, nor shifts in the location of the odorant-induced hotspots. The inherent activity patterns elicited by the different odorants do become more distinct as a function of age, which probably reflects the decline in immature neurons and a slight, but not statistically significant, increase in mature neurons as a function of age. In contrast with the excellent preservation of posterior epithelium, the epithelium lining the anterodorsal septum and the corresponding face of the turbinates is damaged in the 32/35-month-old animals: in this part, horizontal basal cells are reactive, more basal cells and sustentacular cells are proliferating than in younger animals or in posterior epithelium of the same animals, and the neuronal population is less mature on average. Our findings indicate that degeneration of the olfactory epithelium is not an inevitable or pre-programmed consequence of the aging process, since the posterior zone of the epithelium is very well preserved in these barrier-protected animals. However, the deterioration in the anterior epithelium suggests that environmental insults can accumulate or become more severe with age and overwhelm the regenerative capacity of the epithelium. Alternatively, the regenerative capacity of the epithelium may wane somewhat with age. Either of these mechanisms or some combination of them can account for the functional and anatomical deterioration of the sense of smell associated with senescence in humans.

Action Potentials↗

PubMed1996

The interaction of imposed and inherent olfactory mucosal activity patterns and their composite representation in a mammalian species using voltage-sensitive dyes.

From amphibian data, two mechanisms that could underlie the encoding of odorants by the mucosal activity patterns they engender are as follows (1) receptors with similar odorant selectivities could be aggregated spatially on the mucosa (inherent patterns); (2) in analogy to gas chromatography, as odorants are drawn along the surface of the mucosa the strongly sorbed ones could be deposited preferentially upstream, whereas the weakly sorbed ones could be distributed more evenly (imposed patterns). Do both of these possible coding mechanisms operate in mammals and, if so, how do they interact in giving composite patterns (imposed + inherent)? Fluorescence changes in di-4-ANEPPS applied to rat mucosas were monitored by a 10 x 10 pixel photodiode array. To observe the inherent patterns, three odorants of varying sorbabilities first were puffed uniformly onto the entire mucosa mounted in a Delrin chamber. To bring out the imposed patterns, the chamber was then sealed to replicate anatomically the rat's nasal cavity, and these same odorants were drawn at three flow rates along the mucosal flow path. The results demonstrated for the first time the existence of imposed patterns in a mammal. The strongly sorbed odorants, unlike the weakly sorbed one, showed marked imposed patterns. Within physiological limits, increasing the flow rate decreased the magnitude of the imposed patterns. One might consider strategies that the olfactory process could use either to negate or to take advantage of the chromatographic effect, because the lability of the composite patterns with changing stimulus conditions raises questions about their role in odorant encoding.

Animals↗

PubMed1995

Enhancement of odorant-induced mucosal activity patterns in rats trained on an odorant identification task.

Previous studies have demonstrated that there are intrinsic spatial patterns of odorant sensitivity across the rat olfactory mucosa. The question of how these patterns are determined and whether they are modifiable with experience remains open. Therefore, the present study examined whether the odorant-induced spatial activity patterns which are characteristic of different odorants would be altered by experience. Odorant exposure was achieved as a consequence of training and testing on a five odorant identification task in which rats were trained to differentially report (i.e. identify) the odorants propanol, ehtylacetoacetate, carvone, citral, and propyl acetate. At the completion of testing, each animal was sacrificed and their mucosal activity patterns recorded using optical techniques and a voltage-sensitive dye. Using the dye, di-4-ANEPPS, we monitored the fluorescence changes at 100 contiguous sites with a 10 x 10 photodiode array on the olfactory mucosa of each rat's septum and medial surface of the turbinates in response to the same five odorants. The recorded spatial activity patterns of trained animals were compared to those of age-matched controls. For the trained animals, both mucosal surfaces showed a significant increase in the average response magnitude. Furthermore, for the septal mucosa only, there was a significant increase in the distinctiveness of an odorant's characteristic 'hot spot'.

1-Propanol↗

PubMed1995

Mucosal inherent activity patterns in the rat: evidence from voltage-sensitive dyes.

1. Fluorescence changes in the dye di-4-ANEPPS were monitored on the rat's nasal septum and medial surface of the turbinates in response to odorant stimuli. For each mucosal surface a 6.0 x 6.0-mm area was sampled at 100 contiguous sites with a 10 x 10 photodiode array. The odorants were propyl acetate, 2-propanol, citral, L-carvone and ethylacetoacetate, each presented at a low and high concentration. 2. Like previous work using optical recording techniques and potential-sensitive dyes on the amphibian epithelium, the fluorescence signals elicited by odorant stimuli in the rat preparation were nearly identical in shape, time course, and response characteristics as the electroolfactogram (EOG). As with the EOG, a response could only be recorded in the presence of odorant stimuli (that is, no response was detected when nonodorized, humidified air was presented as the stimulus); the amplitude depended on odorant concentration, and the response was abolished both by ether and Triton X-100. 3. Although the entire expanse of each sampled tissue (i.e., septum and medial surface of the turbinates) responded to stimulation with each odorant, each stimulus induced a distinct spatial pattern of activity that was independent of odorant concentration and consistent from animal to animal. Furthermore, the spatial activity patterns recorded for the septum were mirror images of those recorded from the medial surface of the turbinates. 4. Formal statistical analysis of the loci of maximal activity or "hot spot" indicated highly significant effects of the odorants for both the septum and medial surface of the turbinates. 5. The results of these studies give further support to the hypothesis that odorant quality is encoded by differential spatial activity patterns in the olfactory epithelium that are characteristic of different odorants.

Animals↗

PubMed1995

Odorant-specific spatial patterns in mucosal activity predict perceptual differences among odorants.

1. Using operant techniques, rats were trained to differentially report (i.e., identify) the odorants propanol, carvone, citral, propyl acetate, and ethylacetoacetate. After acquisition training, the animals were tested using a 5 x 5 confusion matrix design. The results of the behavioral tests were used to measure the degree of perceptual dissimilarity between any pair of odorants. These dissimilarity measures were then subjected to multidimensional scaling analysis to establish a two-dimensional perceptual odor space for each rat. 2. At the completion of behavioral testing, the fluorescence changes in the dye di-4-ANEPPS were monitored on the rat's nasal septum and medial surface of the turbinates in response to the same odorants. For each mucosal surface a 6.0 x 6.0 mm area was sampled at 100 contiguous sites with a 10 x 10 photodiode array. 3. Formal statistical analysis indicated a highly significant predictive relationship between the relative position of an odorant's mucosal loci of maximal activity or "hot spot" and the relative position of the same odorant in a psychophysically determined perceptual odor space (F = 15.6, P < 0.001). 4. The results of this study suggest for the first time that odorant-induced mucosal activity patterns serve as the substrate for the perception of odorant quality.

Animals↗

PubMed1993

Headache caused by a single lesion of multiple sclerosis in the periaqueductal gray area.

We report a severe acute headache that occurred in conjunction with a solitary fresh lesion of multiple sclerosis in the periaqueductal gray region of a 16-year-old girl. This unique natural event supports the recent proposition, based on observations of patients with implanted electrodes, that perturbations of the periaqueductal gray region can produce headache. It also suggests that headaches accompanying attacks of multiple sclerosis are due to disturbances in particular regions of the brain.

Adolescent↗

PubMed1992

The recording of odorant-induced mucosal activity patterns with a voltage-sensitive dye.

1. Fluorescence changes in the dye (WW 781) were monitored at 100 contiguous sites in a 10 x 10-pixel array on the bullfrog and salamander olfactory mucosas every 10 ms in response to odorous stimuli. The odorants were d-limonene, butanol, and amyl acetate, each presented at two concentrations with a 3:1 ratio. 2. The fluorescence signals elicited by these odorous stimuli were nearly identical in shape and time course to the electro-olfactograms (EOGs) recorded from the same animal under identical conditions. Like the EOGs, the fluorescence signals exhibited adaptation and were abolished by both Triton X-100 and ether. There was no measurable fluorescence when the tissue was not stained with the dye, and there was no change in fluorescence when, for stained tissue, nonodorized, humidified air was presented as the stimulus. 3. This technique presumably monitors the same events as the EOG, but has the advantage of simultaneously recording the odorant-induced activity from multiple sites across most of the mucosa. Thus this technique preserves subtle differences heretofore lost by other techniques both in the coarseness of their matrices and in the variability generated by trying to piece together, into one collage, results from numerous presentations given at different times. 4. In all preparations, there was a larger difference in the inherent activity patterns (derived from response magnitudes) between different odorants than between different concentrations of the same odorant. These differences were largest on the mucosa lining the floor of salamander's olfactory sac. d-limonene and butanol gave their largest responses near the internal and external nares, respectively, whereas the responses for amyl acetate were more uniform across the mucosal sheet. In contrast to the salamander, smaller differences were observed for both the roof and the floor of the bullfrog's olfactory sac. For the floor, both amyl acetate and d-limonene elicited similar patterns of response magnitude, whereas butanol differed from each of these odorants by eliciting a larger response on the anteriolateral aspect of the mucosa and a lesser response on the remainder. For the roof, different odorants produced different activity patterns, which had profiles not simply described as regions of maximal and minimal responsiveness. 5. Different inherent activity patterns based on temporal characteristics of the fluorescence responses were also observed for different odorants. Each odorant produced a different pixel-by-pixel pattern for the times at which the responses started and ended. For any given odorant, these temporal patterns paralleled the patterns given by response magnitudes.(ABSTRACT TRUNCATED AT 400 WORDS)

Ambystoma↗

PubMed1990

Sustained vortex-like waves in normal isolated ventricular muscle.

Sustained reentrant excitation may be initiated in small (20 x 20 x less than 0.6 mm) preparations of normal ventricular muscle. A single appropriately timed premature electrical stimulus applied perpendicularly to the wake of a propagating quasiplanar wavefront gives rise to circulation of self-sustaining excitation waves, which pivot at high frequency (5-7 Hz) around a relatively small "phaseless" region. Such a region develops only very low amplitude depolarizations. Once initiated, most episodes of reentrant activity last indefinitely but can be interrupted by the application of an appropriately timed electrical stimulus. The entire course of the electrical activity is visualized with high temporal and spatial resolution, as well as high signal-to-noise ratio, using voltage-sensitive dyes and optical mapping. Two- and three-dimensional graphics of the fluorescence changes recorded by a 10 x 10 photodiode array from a surface of 12 x 12 mm provide sequential images (every msec) of voltage distribution during a reentrant vortex. The results suggest that two-dimensional vortex-like reentry in cardiac muscle is analogous to spiral waves in other biological and chemical excitable media.

Animals↗

PubMed1987

"Imposed" and "inherent" mucosal activity patterns. Their composite representation of olfactory stimuli.

Both regional differences in mucosal sensitivity and a gas chromatography-like process along the mucosal sheet have been separately proposed in two sets of earlier studies to produce different odorant-dependent activity patterns across the olfactory mucosa. This investigation evaluated, in one study, whether and to what degree these two mechanisms contribute to the generation of these activity patterns. Summated multiunit discharges were simultaneously recorded from lateral (LN) and medial (MN) sites on the bullfrog's olfactory nerve to sample the mucosal activity occurring near the internal and external nares, respectively. Precisely controlled sniffs of four odorants (benzaldehyde, butanol, geraniol, and octane) were drawn through the frog's olfactory sac in both the forward (H1) and reverse (H2) hale directions. By combining the four resulting measurements, LNH1, LNH2, MNH1, and MNH2, in different mathematical expressions, indexes reflecting the relative effects of the chromatographic process, regional sensitivity, and hale direction could be calculated. Most importantly, the chromatographic process and the regional sensitivity differences both contributed significantly to the mucosal activity patterns. However, their relative roles varied markedly among the four odorants, ranging from complete dominance by either one to substantial contributions from each. In general, the more strongly an odorant was sorbed by the mucosa, the greater was the relative effect of the chromatographic process; the weaker the sorption, the greater the relative effect of regional sensitivity. Similarly, the greater an odorant's sorption, the greater was the effect of hale direction. Other stimulus variables (sniff volume, sniff duration, and the number of molecules within the sniff) had marked effects upon the overall size of the response. For strongly sorbed odorants, the effect of increasing volume was positive; for a weakly sorbed odorant, it was negative. The reverse may be true for duration. In contrast, the effect of increasing the number of molecules was uniformly positive for all four odorants. However, there was little evidence that these other stimulus variables had a major influence upon the effects of the chromatographic process and regional sensitivity differences in their generation of mucosal activity patterns.

Acyclic Monoterpenes↗