Biomedical subjects

Richard J Stevenson

Publications and source records attributed to Richard J Stevenson.

12 recordsLinked to original sources

PubMed2007

Age-related changes in odor discrimination.

Odor naming and recognition memory are poorer in children than in adults. This study explored whether such differences might result from poorer discriminative ability. Experiment 1 used an oddity test of discrimination with familiar odors on 6-year-olds, 11-year-olds, and adults. Six-year-olds were significantly poorer at discrimination relative to 11-year-olds and adults, who did not differ. Experiment 2 used the same procedure but with hard-to-name visual stimuli and compared only 6-year-olds with adults (as with the remaining experiments in this study). There was no difference in performance between these groups. Experiment 3 used the same procedure as Experiment 1 but with less familiar odors. Six-year-olds were significantly poorer at discrimination than adults. In Experiment 4 the researchers controlled for verbal labeling by using an articulatory suppression task, with the same basic procedure as in Experiment 1. Six-year-old performance was the same as for Experiment 1 and significantly poorer than that of adults. Impoverished olfactory discrimination may underpin performance deficits previously observed in children. These all may result from their lesser experience with odors, relative to adults.

Adult↗

PubMed2006

Disgust and Huntington's disease.

The disproportionate impairment for the recognition of facial expressions of disgust in patients with Huntington's disease (HD) forms a double dissociation with the impaired recognition of fear that has been reported in amygdala patients. The dissociation has generated discussion regarding the potential existence of neural substrates dedicated to the recognition of facial signals of specific emotions. The aim of this study was to establish whether the impairment for disgust in HD was restricted solely to the domain of facial perception, or whether HD patients also demonstrate impairment in other kinds of disgust. Fourteen HD patients and fourteen age and education matched healthy controls participated in seven disparate emotion processing tasks. (1) A measure of knowledge for the situational determinants of distinct emotions; (2) recognition of emotion expressed in nonverbal vocalisations; (3) recognition of the emotional content of explicit lexical stimuli; (4) recognition of emotional content in pictures of emotion scenes; (5) a disgust experience questionnaire; (6) a measure of olfactory hedonic responsiveness; (7) a measure of gustatory perception. While verbal aspects of disgust processing were preserved, parallel impairments were revealed for olfactory disgust, vocal disgust expressions, the classification of disgusting pictures, and declarative knowledge of disgust elicitors. The finding of impaired perception of disgust signalled through different input domains suggests that the inability to recognise the facial expression in this population reflects a fundamental problem with disgust processing.

Anger↗

PubMed2006

Can odours acquire fat-like properties?

Odours can acquire taste-like properties via simultaneous pairing in the mouth with tastants like sucrose. The experiment reported here sought to test whether qualities other than taste may also be acquired. Participants received pairings between odour A and low-fat unsweetened milk (LFUN), odour B and low-fat sweetened milk (LFSW), odour C and high-fat unsweetened milk (HFUN) and odour D and high-fat sweetened milk (HFSW). On test, participants reported that odours paired with milks perceived as being fattier (i.e. LFSW, HFUN, HFSW) were judged to smell fattier than they did prior to conditioning. In a further test, participants were asked to sample each of the four odours in a slightly fatty-sweet milk target. Odours previously paired with high-fat milks enhanced perceived fattiness of the target, whilst odours previously paired with sweetened milks enhanced perceived sweetness. These results were not well accounted for by participants' explicit knowledge of the odour-milk pairings and suggest that fat-like qualities may be acquired.

Adolescent↗

PubMed2006

Hedonic and sensory characteristics of odors conditioned by pairing with tastants in humans.

Animals readily acquire positive odor-taste hedonic associations, but evidence for this in humans remains weak and was explored further. Retronasal pairing of odors with sucrose or salty stimuli (Experiment 1) increased the rated sweetness of sucrose-paired odors without altering liking, although changes in odor pleasantness correlated with sucrose liking. Experience of odors with sucrose or quinine by sweet likers (Experiment 2) found increased pleasantness and sweetness for sucrose-paired odors, whereas quinine-paired odors became less liked and more bitter. Odor-sucrose pairings in sweet likers and dislikers (Experiment 3) found increased sweetness in both groups but increased odor liking only in likers. These data suggest that evaluative and sensory learning are dissociable and that evaluative changes are sensitive to individual differences in sweet liking.

Adult↗

PubMed2005

Olfactory imagery: a review.

Olfaction's unique cognitive architecture, the apparently inconsistent evidence favoring imagery, and its difficulty of evocation have led some to conclude that there is no capacity for olfactory imagery. Using three streams of evidence, we examine the validity of this claim. First, self-reports of olfactory imagery can resemble those obtained for actual perception. Second, imagining an odor can produce effects similar to actual perception. Third, olfactory perception and memory-based images can interact. A model of olfactory imagery is then presented that utilizes the same systems employed in actual perception, with similar constraints. This model is consistent with olfaction's unique information-processing capacities and can account for previous experimental inconsistencies on the basis of difficulty of evocation, a consequence of unstable access to semantic information. In sum, the evidence presented here is favorable to the existence of an olfactory imagery capacity.

Brain↗

PubMed2004

Reduced discriminability following perceptual learning with odours.

In this experiment, the effects of prior experience on odour perception and discrimination were explored. Participants repeatedly sniffed a mixture composed of two odours, AX, as well as smelling two further odours alone, B and Y. After this training phase, participants were asked to rate the similarity of the odours A and X, B and Y, and a non-exposed pair C and Z. A and X were judged as significantly more alike than the other pairs. Exactly the same pattern emerged on a second test, in which participants were asked to select the odd odour out of sets of three. It was consistently harder for participants to pick the odd odour when the stimuli were drawn from the AX pair (eg A versus AX versus AX). Not only do these findings demonstrate that prior experience can affect odour perception, a finding not predicted by theories of odour perception based solely upon the physiochemical properties of odours, they also suggest that experience can act to selectively decrease discriminability.

Adolescent↗

PubMed2003

Olfactory perceptual learning: the critical role of memory in odor discrimination.

The major problem in olfactory neuroscience is to determine how the brain discriminates one odorant from another. The traditional approach involves identifying how particular features of a chemical stimulus are represented in the olfactory system. However, this perspective is at odds with a growing body of evidence, from both neurobiology and psychology, which places primary emphasis on synthetic processing and experiential factors--perceptual learning--rather than on the structural features of the stimulus as critical for odor discrimination. In the present review of both psychological and sensory physiological data, we argue that the initial odorant feature extraction/analytical processing is not behaviorally/consciously accessible, but rather is a first necessary stage for subsequent cortical synthetic processing which in turn drives olfactory behavior. Cortical synthetic coding reflects an experience-dependent process that allows synthesis of novel co-occurring features, similar to processes used for visual object coding. Thus, we propose that experience and cortical plasticity are not only important for traditional associative olfactory memory (e.g. fear conditioning, maze learning, and delayed-match-to-sample paradigms), but also play a critical, defining role in odor discrimination.

Animals↗

PubMed2003

The fundamental role of memory in olfactory perception.

Current emphasis on odorant physiochemical features as the basis for perception largely ignores the synthetic and experience-dependent nature of olfaction. Olfaction is synthetic, as mammals have only limited ability to identify elements within even simple odor mixtures. Furthermore, olfaction is experience-bound, as exposure alone can significantly affect the extent to which stimuli can be discriminated. We propose that early analytical processing of odors is inaccessible at the behavioral level and that all odors are initially encoded as 'objects' in the piriform cortex. Moreover, we suggest that odor perception is wholly dependent on the integrity of this memory system and that its loss severely impairs normal perception.

Animals↗

PubMed2003

Age-related changes in children's hedonic response to male body odor.

Male sweat smells disgusting to many adults, but it is unclear whether children find it so. In Experiment 1A, children (mean age = 8.7 years) and adolescents (M=16.6 years) smelled male sweat and other odors, rated each for liking, and attempted their identification. Only female adolescents disliked male sweat and could identify it. Experiment 1B, using the same procedure, obtained this gender difference in adults (M=26.7 years). In Experiment 2, children (M=8.1 years) and adolescents (M=16.6 years) were cued about the identity of the same odors. Irrespective of gender, adolescents disliked male sweat more than did children. In sum, dislike for the odor of male sweat may be an acquired social response that is based on odor identification.

Adolescent↗

PubMed2003

A mnemonic theory of odor perception.

The psychological basis of odor quality is poorly understood. For pragmatic reason, descriptions of odor quality generally rely on profiling odors in terms of what odorants they bring to mind. It is argued here that this reliance on profiling reflects a basic property of odor perception, namely that odor quality depends on the implicit memories that an odorant elicits. This is supported by evidence indicating that odor quality as well as one's ability to discriminate odors is affected by experience. Developmental studies and cross-cultural research also point to this conclusion. In this article, these findings are reviewed and a model that attempts to account for them is proposed. Finally, the model's consistency with both neurophysiological and neuropsychological data is examined.

Humans↗

PubMed2002

A cognitive remediation programme for adults with Attention Deficit Hyperactivity Disorder.

OBJECTIVE: This is the first systematic examination of the efficacy of a cognitive remediation programme (CRP) for management of adult Attention Deficit Hyperactivity Disorder (ADHD). The CRP was designed to target problems commonly associated with adult ADHD, namely, attention problems, poor motivation, poor organizational skills, impulsivity, reduced anger control and low self-esteem. METHOD: In a randomized, controlled trial, a representative sample of adults with ADHD (some medicated, some not) were assigned to either a CRP (n = 22) or a waiting list control (n = 21). The CRP was delivered in an intensive format with eight two-hour, weekly sessions with support people who acted as coaches, and participant workbooks with homework exercises. RESULTS: Participants who completed the CRP reported reduced ADHD symptomatology (effect size (d) = 1.4), improved organizational skills (d = 1.2) and reduced levels of anger (d = 0.5). Clinically significant improvements in ADHD symptomatology (d = 1.4) and organizational skills (d = 1.3) were maintained one year after the intervention. CONCLUSIONS: These findings suggest that the CRP provides a practical way of enhancing daily functioning for adults with ADHD.

Adult↗

PubMed2002

Gender differences in the retention of Swahili names for unfamiliar odors.

Several studies, using different techniques, have established that women typically outperform men in naming odors. The mechanism for this effect was explored here in two experiments. In experiment 1, men and women learned randomly assigned Swahili names for a set of seven unfamiliar odors. Following multiple acquisition trials, participants were retested 1 week later. Although learning rates were identical during acquisition, after the 1 week interval, females were able to name more of the odors than men. Experiment 2 used a similar design but also included a retroactive interference task following the 1 week retention interval test. Although the week-long interval had the same effect as in experiment 1, interference had no effect on male or female performance. These results suggest that under conditions where experience is equated, female naming advantage may result from better consolidation of the learned material.

Adolescent↗