Olfaction scaffolds the developing human from neonate to adolescent and beyond

The impact of the olfactory sense is regularly apparent across development. The foetus is bathed in amniotic fluid that conveys the mother’s chemical ecology. Transnatal olfactory continuity between the odours of amniotic fluid and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother’s diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognise their mother’s odours; later, children are able to recognise other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child’s emotions, and scaffold perception and learning through non-olfactory senses. During adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and caregiver during the multiple transitions of development between birth and adolescence

Adverse Effect of Air Pollution on Odor Perception

status: publishe

Neurobiological foundations of aesthetics and art

A theory of the neurobiological foundations of aesthetics and art is described. This has its roots in emotion, in which what is pleasant or unpleasant, a reward or punisher, is the result of an evolutionary process in which genes define the (pleasant or unpleasant) goals for action. To this is added the operation of the reasoning, syntactic, brain system which evolved to help solve difficult, multistep, problems, and the use of which is encouraged by pleasant feelings when elegant, simple, and hence aesthetic solutions are found that are advantageous because they are parsimonious, and follow Occam's Razor. The combination of these two systems, and the interactions between them, provide an approach to understanding aesthetics that is rooted in evolution and its effects on brain design and function

The impact of reward value on early sensory processing and its interaction with selective attention

Reward value affects the earliest stages of sensory perception. Whereas a host of previous studies have investigated the underlying mechanisms of reward-driven modulation of visual perception, reward effects in other sensory modalities have remained underexplored. Specifically, it has remained unknown how reward signals should be coordinated and communicated across sensory modalities. The current PhD thesis aimed to gain insight into the underlying mechanisms of reward-driven modulation of perception and its interaction with attention across sensory modalities. To this end, three experiments were conducted to identify the behavioral and electrophysiological correlates of reward effects. In Study 1, we found that high reward, task-irrelevant visual cues (intra-modal) elicited an early suppression of visual event-related potentials (ERPs). High reward auditory cues (cross-modal), on the other hand, led to a later modulation of visual ERPs and facilitated behavioral performance. Study 2 tested the dependence of reward effects on the spatial and temporal arrangement of intra-modal and cross-modal cues relative to the target, and showed that each reward cue maximally exerts its effect under a specific size of attentional focus. Study 3 explicitly manipulated the spatial attention and tested how reward associations of an audiovisual stimulus influence the allocation of attention. We found that auditory rewards enhanced the attentional modulation of both visual and auditory ERPs. Interestingly, although visual rewards did not lead to a distinguishable ERP modulation, they led to strong modulations when they were combined with auditory rewards, suggesting that integration across modalities boosts the reward effects. Taken together, the current PhD thesis identified the behavioral and neural signatures of reward-driven modulation of perception under different modes of reward signaling and different degrees of attentional engagement. Our findings inspire a two-stage model of reward processing, with local, intra-modal reward effects occurring at an early stage and long-range, multimodal reward effects arising at a later stage. Cross-modal reward signals have important ramifications for clinical applications where the impaired function of one sense can be rehabilitated by motivational signals conveyed through another sensory modality.2021-11-2

Tactile Roughness Perception in the Presence of Olfactory and Trigeminal Stimulants

Previous research has shown that odorants consistently evoke associations with textures and their tactile properties like smoothness and roughness. Also, it has been observed that olfaction can modulate tactile perception. We therefore hypothesized that tactile roughness perception may be biased towards the somatosensory connotation of an ambient odorant. We performed two experiments to test this hypothesis. In the first experiment, we investigated the influence of ambient chemosensory stimuli with different roughness connotations on tactile roughness perception. In addition to a pleasant odor with a connotation of softness (PEA), we also included a trigeminal stimulant with a rough, sharp or prickly connotation (Ethanol). We expected that - compared to a No - odorant control condition—tactile texture perception would be biased towards smoothness in the presence of PEA and towards roughness in the presence of Ethanol. However, our results show no significant interaction between chemosensory stimulation and perceived tactile surface roughness. It could be argued that ambient odors may be less effective in stimulating crossmodal associations, since they are by definition extraneous to the tactile stimuli. In an attempt to optimize the conditions for sensory integration, we therefore performed a second experiment in which the olfactory and tactile stimuli were presented in synchrony and in close spatial proximity. In addition, we included pleasant (Lemon) and unpleasant (Indole) odorants that are known to have the ability to affect tactile perception. We expected that tactile stimuli would be perceived as less rough when simultaneously presented with Lemon or PEA (both associated with softness) than when presented with Ethanol or Indole (odors that can be associated with roughness). Again, we found no significant main effect of chemosensory condition on perceived tactile roughness. We discuss the limitations of this study and we present suggestions for future research.Previous research has shown that odorants consistently evoke associations with textures and their tactile properties like smoothness and roughness. Also, it has been observed that olfaction can modulate tactile perception. We therefore hypothesized that tactile roughness perception may be biased towards the somatosensory connotation of an ambient odorant. We performed two experiments to test this hypothesis. In the first experiment, we investigated the influence of ambient chemosensory stimuli with different roughness connotations on tactile roughness perception. In addition to a pleasant odor with a connotation of softness (PEA), we also included a trigeminal stimulant with a rough, sharp or prickly connotation (Ethanol). We expected that—compared to a No-odorant control condition—tactile texture perception would be biased towards smoothness in the presence of PEA and towards roughness in the presence of Ethanol. However, our results show no significant interaction between chemosensory stimulation and perceived tactile surface roughness. It could be argued that ambient odors may be less effective in stimulating crossmodal associations, since they are by definition extraneous to the tactile stimuli. In an attempt to optimize the conditions for sensory integration, we therefore performed a second experiment in which the olfactory and tactile stimuli were presented in synchrony and in close spatial proximity. In addition, we included pleasant (Lemon) and unpleasant (Indole) odorants that are known to have the ability to affect tactile perception. We expected that tactile stimuli would be perceived as less rough when simultaneously presented with Lemon or PEA (both associated with softness) than when presented with Ethanol or Indole (odors that can be associated with roughness). Again, we found no significant main effect of chemosensory condition on perceived tactile roughness. We discuss the limitations of this study and we present suggestions for future research

Relações entre características do autismo, variáveis emocionais e o processamento olfativo na população geral

Although altered sensory processing is recognized as a key-feature of Autism Spectrum Disorder (henceforth “autism”), olfactory functioning is still poorly understood in this condition. Considering the role of olfaction in human social communication and well-being, it is crucial to investigate which variables are related to the often-observed inconsistent results concerning olfactory functioning in autism. Study of the expression of autism traits and other autism-related variables in the general population may be useful to understand which specific dimensions are related to the often-observed symptoms, alterations, and heterogeneity in the autism spectrum, including in the olfactory domain. The present work sought to contribute to the multidimensional assessment of anxiety and autism traits in adults of the general population, as well as to the understanding of the multivariate relationships between autism characteristics, olfactory processing, anxiety, and alexithymia. Study 1 and Study 2 aimed to extend the available evidence about the psychometric properties of the State-Trait Inventory for Cognitive and Somatic Anxiety (STICSA) and the Autism Spectrum Quotient (AQ). Results supported the adequacy of both instruments to measure anxiety and autism traits, respectively, in a multidimensional perspective. Consistent with the literature, Study 1 found support for a four-factor, as well as a two-factor structure within the state and traits forms of the STICSA. Moreover, measurement invariance across sex groups, and good nomological validity were also supported for the STICSA. Results also suggested that the cognitive and somatic dimensions of trait anxiety, as measured by the STICSA, are differently related with the subjective and psychophysiological responses in distinct emotional contexts. Results of Study 2 further supported a three-factor structure of the AQ, consistent with previous studies, as well as the role of alexithymia, particularly difficulties in identifying feelings, as a mediator of the relationship between autism traits and trait anxiety. Study 3 analyzed the impact of the social skills and attention to detail dimensions of autism traits, and cognitive/somatic trait anxiety, on the olfactory abilities of the general population. Results emphasized the roles of sex, attention to detail and trait-somatic anxiety as significant predictors of odor discrimination abilities. Finally, Study 4 provided an integrative review about olfactory processing in autism and how advancing research in this area may benefit the knowledge and practice regarding social cognition and behavior in autism. The findings of this research highlight the need to explore the distinct dimensions of autism-related variables to better understand their complex relationships and impact in the functioning of the spectrum, including in olfactory functioning.Embora alterações no processamento sensorial sejam uma característica-chave da Perturbação do Espetro do Autismo (daqui em diante “autismo”), o funcionamento olfativo ainda é pouco compreendido nesta condição. Considerando o papel do olfato na comunicação, interação social e bem-estar, é crucial investigar que variáveis estão relacionadas com os resultados inconsistentes frequentemente observados no âmbito do processamento olfativo no autismo. Estudar a expressão de traços de autismo na população geral, bem como a expressão multidimensional de outras variáveis relacionadas, pode ser útil para compreender que dimensões estão relacionadas com os sintomas, alterações e heterogeneidade frequentemente observados no autismo, incluindo no domínio olfativo. O presente trabalho pretendeu contribuir para a avaliação multidimensional da ansiedade e de traços de autismo em adultos da população geral, bem como para uma melhor compreensão da relação multivariada entre as características do autismo, processamento olfativo, ansiedade e alexitimia. O Estudo 1 e o Estudo 2 tiveram como objetivo estender a evidência disponível sobre as propriedades psicométricas do State-Trait Inventory for Cognitive and Somatic Anxiety (STICSA) e do Autism Spectrum Quotient (AQ). Os resultados suportaram a adequação de ambos os instrumentos para medir ansiedade e traços de autismo, respetivamente, numa perspetiva multidimensional. Em linha com a literatura, o Estudo 1 providenciou suporte para uma estrutura de quatro fatores, bem como para uma estrutura de dois fatores dentro das dimensões de ansiedade traço e estado do STICSA. Observou-se ainda invariância fatorial considerando a variável sexo, assim como boa validade nomológica. Os resultados também sugeriram que as dimensões cognitivas e somáticas da ansiedade traço, medidas pelo STICSA, estão relacionadas de forma distinta com as respostas subjetiva e psicofisiológica em diferentes contextos emocionais. Os resultados do Estudo 2, de modo consistente com estudos anteriores, suportaram uma estrutura de três fatores do AQ, bem como o papel da alexitimia, particularmente das dificuldades em identificar sentimentos e emoções, como mediadora da relação entre traços de autismo e ansiedade traço. O Estudo 3 analisou o impacto das dimensões de traços de autismo relacionadas com as capacidades sociais e atenção para os detalhes, e da ansiedade traço cognitiva/somática, nas capacidades olfativas da população geral. Os resultados evidenciaram o papel das variáveis sexo, atenção para os detalhes e ansiedade traço somática como preditores significativos da capacidade de discriminação olfativa. Por fim, o Estudo 4 apresentou uma revisão integrativa sobre o processamento olfativo no autismo, e como o avanço da investigação nesta área pode beneficiar o conhecimento e a prática no âmbito da cognição e comportamento social. Os resultados desta investigação destacam a importância de explorar as diferentes dimensões das variáveis relacionadas com o autismo para melhor compreender a complexidade das suas relações e impacto no funcionamento do espetro, incluindo no que diz respeito ao funcionamento olfativo.Programa Doutoral em Psicologi

Extending sensorimotor enactivism to flavour and smell

This thesis explores whether sensorimotor enactivism can be extended to flavour and smell perception. Sensorimotor enactivism claims that perceptual experience is constituted by skilful bodily engagement with the world. This engagement is said to be imbued with an implicit understanding of sensorimotor contingencies — law-like relations holding between bodily activity and sensory changes. The sensorimotor approach is intended as a non-visuocentric theory of perception, purporting to offer an account of all varieties of perceptual experience. However, until now there has been no sustained research into the application of sensorimotor enactivism to flavour and smell. Moreover, some researchers have argued that these senses are problem cases for the theory, and that facts about flavour and smell serve to refute the approach. This thesis responds to such worries and addresses the gap in the literature. It argues that sensorimotor enactivism can be extended to flavour and smell and offers a positive account of how we should think about our perceptual experiences through these modalities. Flavour and smell, it will be argued, do not allow immediate perceptual access to ordinary physical objects like roses and tomatoes. But rather, they give us immediate access to odours and flavours. In order to understand what our perceptual access to such entities consists in, this thesis draws upon tools from Gestalt psychology. Gestalt psychology allows for a modality-neutral way of thinking about perceptual organisation and helps us to arrive at a useful notion of ‘perceptual objecthood’. The entities we perceive through flavour and smell are much more diffuse than the ordinary three-dimensional objects that we perceive through sight, and the phenomenology of these kinds of perception seem particularly difficult to articulate. I argue that flavour and smell are still akin to other senses like vision in that they allow us to perceive the world as segregated into discrete perceptual objects, which exhibit figure-ground segregation and perceptual constancies. An understanding of perceptual organisation and objecthood allows for a more refined sensorimotor approach and will help us to arrive at solutions to further philosophical queries, such as whether flavour and smell are multisensory, and what the role of memory is in these perceptual experiences