Synthesizing complex sensations from simple components

The target article suggests that taste is not based on the traditional four basic tastes, but rather is a continuum subserved by cross-fiber integration. This commentary describes evidence indicating that the traditional concept is valid, and that with suitable precautions, it is possible to match natural substances using mixtures representing fundamental tastes.     

The effect of stimulus delivery technique on perceived intensity functions for taste stimuli: Implications for fMRI studies

Classic psychophysical studies have provided significant information on the psychophysical functions for taste stimuli. With the advent of fMRI, studies are being conducted that provide insight into central processing of gustation in humans. However, fMRI experiments impose physical limitations on stimulus delivery. In the present study, we compared psychophysical functions relating perceived intensity to concentration, derived from previous studies that used the traditional sip-and-spit and dorsal flow delivery techniques, to psychophysical functions generated in this study using a simulated stimulus delivery technique (SSDT). The SSDT delivered minute quantities of taste stimuli to the dorsal surface of the tongue, just as in an fMRI scanner. As was hypothesized, the results indicated that slopes of intensity functions were dependent on the type of stimulus delivery technique. The SSDT resulted in slopes that were more similar to those generated by dorsal flow than by sip-andspit stimulus delivery techniques, suggesting the importance of considering the influence of stimulus delivery on psychophysical response in designing and interpreting experiments.     

Impairments in the perception of odor-induced tastes and their relationship to impairments in taste perception

Certain odors have tastelike qualities when sniffed. To the extent that these qualities are akin to real taste experiences, impairment in perception of odor-induced tastes should be accompanied by taste impairment, and vice versa. Twelve patients were selected with possible odor-induced taste impairments or general taste impairments via a screening test, along with a further 6 patients with a probable taste impairment (insular lesion). These 18 patients, along with 19 normal controls, completed a battery of odor, taste, visual control, and neuropsychological tests to assess impairments in odor-induced taste perception and general taste perception. Four patients had an odor-induced taste impairment and were also impaired on taste perception. A further analysis, using regression on the whole sample, indicated that taste impairments were associated with odor-induced taste abnormalities independent of other predictors. This pattern also held for the patient group alone. The insular patients also exhibited both taste and odor-induced taste impairments. This study is the first to demonstrate a relationship between impaired taste perception and the perception of odor-induced tastes and suggests that both may rely on certain common neural substrates.     

An application of the τ scale of taste: Interaction among the four qualities of taste

A series of 10 standard solutions, spaced equidistant on the τ scale, were prepared for each of the basic tastes, sweet, bitter, sour, and salty. In addition, four other concentrations of each basic taste, plus 96 compound solutions of two different solutes, were prepared as test stimuli. The Ss, four specialists in taste testing and four laymen, were asked to specify the taste of each test stimulus by matching it with the standard series. In this way, both the precision of the matching procedure and the enhancement or masking of one taste by another were measured in terms of τ, which is a nearly logarithmic function of concentration. The average standard deviations of the matchings among the Ss were in the order of 0.3 to 0.5 units on the τ scale, which corresponds to a value between 1 and 2 decilogs of concentration. Among the interactions observed was the mutual masking of sucrose and quinine sulfate.     

Psychophysics of taste lateralization on anterior tongue

There have been very few investigations of the spatial properties of taste stimuli localized to specific areas of the oral cavity. This is surprising, since the spatial localization of taste sensations may contribute to the overall taste percept, much as do quality, intensity, and the temporal characteristics of tastes. The difficulty in eliminating the confounding factor of a tactile sensation may partially account for the paucity of such studies, since a gustatory stimulus cannot be presented as a liquid without a tactile component. As a step toward understanding the localizability of gustatory sensations, we designed a yoked stimulator and an experimental procedure to control for tactile cues. Lateral discrimination was evaluated at the tip of the tongue with four taste stimuli (sodium saccharin, sodium chloride, citric acid, and quinine hydrochloride) by presenting a taste and a blank solution simultaneously at two locations on the tongue. We found that subjects could lateralize all four taste stimuli in the absence of any discriminative tactile cues. Subjects' ability to lateralize varied as a psychometric function of the stimulus concentration. Detection thresholds, measured in a forced-choice two-interval staircase procedure with the same yoked stimulator that was used in the lateralization task, were always lower than lateralization thresholds, and both lateralization and detection thresholds were correlated within subjects. Subjects were unable to lateralize taste cues on a nongustatory surface under the upper lip at the highest tested concentrations, at which performance was 100% on a gustatory surface (dorsal anterior tongue). These results show that (1) taste compounds can be lateralized in the absence of any discriminative mechanical cue (but only on the gustatory epithelium) and (2) although the localization of a compound does not logically require conscious detection of the taste (cf. blind sight), subjects always detected a taste when they were able to lateralize.     

Taste perceptual circuit for the generation of autonomous responses in virtual creatures

BraLearning is one of the most complex cognitive processes that living beings have. This process is distributed within the brain and each independent cognitive function contributes to a small or large extent to it. Particularly, affective learning is a process that allows us to identify stimuli in the environment and discriminate them based on our tastes or preferences. Within this work we will address a type of affective evaluation generated by the perceptual circuit of taste that allows us to determine flavors from the environment and how this information becomes part of the perceptual affective evaluation. We will start this work by identifying other computational works that address affective processes oriented to taste or that involve some other affective evaluation. Subsequently, we analyze of neuroscientific information that allows us to build an informal model of the perceptual circuit of taste. Finally, we propose a cognitive architecture for the generation of autonomous responses oriented to taste in virtual creatures and we will demonstrate its functionality through an implementation of this model in some case studies through distributed modules and discuss the results obtained.     

Do infusion-related tastes and odors facilitate the development of anticipatory nausea? A failure to support hypothesis

Distinctive tastes and odors have been identified as potent nausea-eliciting stimuli in cancer chemotherapy patients who develop anticipatory nausea or vomiting (ANV). Based on the experimental research on illness-aversion learning and based on previous clinical research with chemotherapy patients, it was hypothesized that the presence of tastes and odors during infusions should increase the likelihood that a patient will subsequently develop ANV. Seventy-eight new chemotherapy outpatients were interviewed immediately following each of their infusions with regard to the experience of infusion-related tastes, odors, and body sensations. Results failed to support the hypothesis. The subsequent development of ANV was unrelated to reports of tastes and odors both during patients' initial two chemotherapy infusions and during the two infusions preceding their initial report of ANV. Furthermore, reports of tastes and odors were surprisingly infrequent relative to previous research. Methodological and environmental explanations for this difference in taste and odor prevalence are considered. It is concluded that, when present, infusion-related tastes and odors may indeed increase the likelihood of subsequent development of ANV. However, future research should examine the extent to which the physical characteristics of chemotherapy clinics might affect the prevalence of infusion-related tastes and odors.     

The limited capacity of humans to identify the components of taste mixtures and taste-odour mixtures

The capacity of humans to identify the components of taste mixtures and odour-taste mixtures was investigated in two experiments. Subjects were trained to identify the components presented alone and to use a 'yes/no' procedure to identify them in mixtures. All stimuli were presented with a retronasal (by mouth) technique. A maximum of three tastants were identified in both types of mixtures, only one tastant was identified in five-component taste mixtures, and no component was identified in four-component odour-taste mixtures. Importantly, in no instance was the olfactory stimulus identified in any mixture with tastes, including binary mixtures. Loss of identity of the odorant in binary and ternary mixtures may have been due to suppression as a consequence of temporal processing, or to the absence of an association between the odorant and tastants that had established an identifiable percept. In contrast, poor identification of the components of the quaternary odour-taste mixture and quinternary taste mixture is attributed to the limited capacity of working memory. Overall, the poorer ability to identify components in odour-taste mixtures than in taste mixtures indicates that interactions occurred between the two senses, challenging the proposal that odours and tastes are processed independently when present in complex chemosensory stimuli.     

Gastrointestinal reactivity in rats lacking anterior insular neocortex

Behavioral and physiological studies have shown that the insular neocortex participates in a wide variety of special visceral processes, in particular, the higher-order integration of taste stimuli and the regulation of autonomic activity. The present experiment examined the involvement of the anterior insular (gustatory) neocortex (AIGN) in gastrointestinal reactivity and taste learning in rats by the use of a modified taste aversion training procedure. Normal rats and rats lacking AIGN demonstrated similar "illness thresholds" to the early onset symptoms of ingested LiCl. Conversely, animals lacking AIGN showed significant impairments in taste aversion learning ability. From a consideration of several research findings it is concluded that animals lacking AIGN can normally perceive tastes and illness, but these animals experience reliable impairments in taste aversion learning ability.     

A computer-controlled electrogustometer for the estimation of evoked taste thresholds

Reliable taste detection thresholds in humans are difficult to obtain for either research or clinical purposes because ordinary taste stimuli cannot be generated and presented by means of a computer. However, in investigations of taste dysfunction, electrical taste stimulation (electrogustometry) is sometimes employed. Minute anodal direct currents are applied manually to the tongue, giving rise to an acid taste experience through the liberation of protons into the saliva. This experience accords with recent findings on the mechanisms underlying sour taste perception. The device described here is a safe and accurate constant-current device, operating under computer control at very low amperages, making it possible to apply modern psychophysical procedures to the measurement of evoked taste thresholds.     

Differential context effects between sweet tastes and smells

"Sweet" smells and tastes are perceptually similar, and physiological data indicate some commonality of central processing. However, sweet tastes and sweet smells do not provide interchangeable contexts in psychophysical experiments. The same sweet tastes are perceived as less intense when stronger sweet tastes are present, and they are perceived as more intense when weaker sweet tastes are present, as with sweet smells. However, complementary sets of sweet tastes and smells (e.g., weak sweet tastes, strong sweet smells) do not eliminate these differential context effects (DCEs). The present experiments examined, first, whether DCEs between sweet tastes and smells arise because of differences between odors and tastes in the way that sweetness scales with intensity as concentration rises, and, second, whether DCEs may be smaller for sweet tastes and smells, when contrasted with sweet tastes and nonsweet smells. The findings were clear: DCEs were consistently present, suggesting they are independent of perceptual similarity. These results imply that DCEs are probably not psychological in origin or centrally based; rather, they may have a subcortical locus.     

大众与个人审美品位的认知与神经机制

大众与个人的审美品位分别代表了审美活动在个体间的一致性和差异性。将大众品位和个人品位相结合的新趋势正在挑战传统的"普遍性"审美法则,并日益凸显审美反应的个体差异。存在诸多因素可以调节大众和个人审美品位的相对比例,包括刺激类型、专业性、文化背景、先前经验和年龄等。大众与个人审美品位的神经机制中,奖赏系统和默认模式网络扮演重要角色。目前,审美品位与审美加工模型的理论关系有待进一步厘清和验证。未来相关研究可以在拓展审美对象领域、完善大众与个人审美品位与不同审美加工阶段的对应关系等方向上继续开展。     

Sequential ideal-observer analysis of visual discriminations

Visual stimuli contain a limited amount of information that could potentially be used to perform a given visual task. At successive stages of visual processing, some of this information is lost and some is transmitted to higher stages. This article describes a new analysis, based on the concept of the ideal observer in signal detection theory, that allows one to trace the flow of discrimination information through the initial physiological stages of visual processing, for arbitrary spatio-chromatic stimuli. This ideal-observer analysis provides a rigorous means of measuring the information content of visual stimuli and of assessing the contribution of specific physiological mechanisms to discrimination performance. Here, the analysis is developed for the physiological mechanisms up to the level of the photoreceptor. It is shown that many psychophysical phenomena previously attributed to neural mechanisms may be explained by variations in the information content of the stimuli and by preneural mechanisms.     

Perception of the form of stimulus increment as a method in assessment of the psychophysical relationship

Among numerous procedures for determination of the psychophysical relation, one approach has seldom been applied. Essential in this method is to present a set of stimuli whose intensity increases in fixed time following different forms. The objective stimulus increment, which the subjects perceive as linear growth directly, represents the inverse psychophysical relation. In this paper the method was tested in the fields of click frequency and sound pressure. This procedure was named "Perception of the Form of Stimulus Increment in Time". In comparison to other psychophysical approaches, this one has several advantages. The principal ones are the following: (1) In assessing the psychophysical relation it is not necessary to try to measure the perceptual magnitude; and (2) the psychophysical relation is directly determined by its dynamic pattern. In this paper modifications to the method are reported which facilitate the subject's task and avoid some differences in subjects' individual approaches to the task. The modified procedure leads to results satisfactory independent of the influence of the factors irrelevant to the psychophysical relationship.     

Amplitude spectra of line-motion stimuli

The line-motion illusion has been regarded as the result of attention. An alternative interpretation is that the illusion is related to apparent motion which would predict the stimuli to contain motion energy associated with the direction of the illusory motion. In order to examine this possibility Fourier transforms of x-t plots of line-motion stimuli were generated under a variety of conditions. The sums of amplitudes associated with movement in the directions away from the cue relative to that towards the cue were compared to previously published psychophysical observations. It was found that the amplitude sums are largely consistent with the psychophysical results. In the few cases where there were discrepancies between results based on amplitude spectra and psychophysical findings, these discrepancies could be accounted for by making relatively simple and plausible assumptions. The present observations suggest that motion energy may be sufficient to account for the line-motion illusion.     

Neural representation of consciously imperceptible speech sound differences

The concept of subliminal perception has been a subject of interest and controversy for decades. Of interest in the present investigation was whether a neurophysiologic index of stimulus change could be elicited to speech sound contrasts that were consciously indiscriminable. The stimuli were chosen on the basis of each individual subject's discrimination threshold. The speech stimuli (which varied along an F3 onset frequency continuum from /da/ to /ga/) were synthesized so that the acoustical properties of the stimuli could be tightly controlled. Subthreshold and suprathreshold stimuli were chosen on the basis of behavioral ability demonstrated during psychophysical testing. A significant neural representation of stimulus change, reflected by the mismatch negativity response, was obtained in all but 1 subject in response to subthreshold stimuli. Grand average responses differed significantly from responses obtained in a control condition consisting of physiologic responses elicited by physically identical stimuli. Furthermore, responses to suprathreshold stimuli (close to threshold) did not differ significantly from subthreshold responses with respect to latency, amplitude, or area. These results suggest that neural representation of consciously imperceptible stimulus differences occurs and that this representation occurs at a preattentive level.     

Individual gustatory reaction times to various groups of chemicals that provoke basic taste qualities

Reaction times (RTs) to four groups of substances that provoke different taste qualities were measured. Measurements for all substances with the same taste, equalized in perceived intensity and provoking a very strong taste, were made concurrently for each subject. The comparisons were made on the individual level. No significant differences in RTs to substances with the same taste quality were found. When the factor of perceived intensity is kept constant, no effect of the stimulus chemical composition on RTs seems to be present. RTs to stimuli with different tastes differ significantly, the shortest being to salt and the longest to bitter. The difference in RTs for sour and sweet substances is small, and the subjects were not all alike in terms of the order of RTs with respect to these stimuli.     

Taste and water taste of twenty-six compounds for man

Taste profiles were obtained for 26 compounds after adaptation to distilled water and also for water after adaptation to each of the 26 compounds. Each of the four “basic tastes” was induced in water by adaptation to certain of the compounds. Compounds having similar tastes did not necessarily have similar water tastes. The results imply a peripheral locus of the water taste mechanism(s).     

Hedonic integration: Test of a linear model

A simple adding model was tested for the integration of the hedonic component of taste stimuli. Subjects tasted mixtures of quinine sulfate and apple juice and rated the pleasantness of the composite taste, The rating data showed significant nonadditivity, which could reflect failure of the model itself or merely a nonlinear response output function. Since the rating data could be transformed to additivity, justification for such transformation was sought through a second task based on the logic of two-stage integration. In this task, subjects rated the difference between taste mixtures. The subtracting model underlying this judgment provided functional scale values for the taste mixtures on validated interval scales. These functional scale values were consistent with the predictions of the simple adding model, and thus justified the transformation of the single rating data to additivity. The application of functional measurement to obtain the psychophysical functions of the two taste components is also illustrated.