Sunday, July 10, 2022

Sound induces analgesia through corticothalamic circuits

Sound induces analgesia through corticothalamic circuits. Wenjie Zhou et al. Science, Jul 7 2022, Vol 377, Issue 6602, pp. 198-204, DOI: 10.1126/science.abn4663

The pain-reducing effects of music: That sound can effectively suppress pain has been known for some time. However, it is still unclear what drives the analgetic effect induced by music or noise. Zhou et al. used a range of methods to demonstrate in mice that the auditory cortex is functionally connected to regions involved in nociception (see the Perspective by Kuner and Kuner). The neuronal circuits depend on the physical location of the pain. Whereas the analgetic effect of a 5-decibel signal-to-noise ratio white noise on the hindpaws involved projections from the auditory cortex to the posterior thalamic nuclei, on the forepaws, it involved projections from the auditory cortex to the ventral posterior nuclei. Distinct thalamic nuclei are thus involved in the processing of nociceptive information perceived at distinct physical locations. —PRS

Abstract: Sound—including music and noise—can relieve pain in humans, but the underlying neural mechanisms remain unknown. We discovered that analgesic effects of sound depended on a low (5-decibel) signal-to-noise ratio (SNR) relative to ambient noise in mice. Viral tracing, microendoscopic calcium imaging, and multitetrode recordings in freely moving mice showed that low-SNR sounds inhibited glutamatergic inputs from the auditory cortex (ACxGlu) to the thalamic posterior (PO) and ventral posterior (VP) nuclei. Optogenetic or chemogenetic inhibition of the ACxGlu→PO and ACxGlu→VP circuits mimicked the low-SNR sound–induced analgesia in inflamed hindpaws and forepaws, respectively. Artificial activation of these two circuits abolished the sound-induced analgesia. Our study reveals the corticothalamic circuits underlying sound-promoted analgesia by deciphering the role of the auditory system in pain processing.

Popular version: Soft sounds numb pain. Researchers may now know why. Experiments in mice show how sound tamps down on pain processing in the brain. Tess Joosse. Science News, Jul 7 2022.

In their sexual fantasies, women have sex with about one person a day, men with about two

Sexual Fantasies, from Part II - Copulatory Adaptations. Rui Miguel Costa. In The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology, pp 209-240. Jun 30 2022.

Summary: Sexual fantasies refer to mental imagery of sexual activity with an emotional component that absorbs the fantasizer. These images are often sexually arousing and enjoyable, but they can elicit guilt and be unwanted and intrusive. Reported frequency of sexual fantasizing is subject to large individual differences. The present chapter reviews and discusses the role of motivational tendencies underlying sexual fantasies and the relationship between sexual functioning and sexual fantasies. Men report more frequent fantasies than women, but at least part of the difference is explained by greater frequency of masturbation accompanied by fantasies for men than women. Sexual desire does not require the experience of fantasies, but fantasy frequency is robustly related to sexual desire in the reproductive years. Tendency to experience sexual fantasies is related to imagery ability, in general, but the modest correlations suggest independent processes. Unlike sexual activity that requires compromise between partners’ desires, fantasies are unconstrained by physical and social reality; as such, they provide a window into sexual motivations that guide cognitions and behavior. Predictions of sex differences in fantasy contents based on evolutionary theory have been confirmed by many studies. Women are more likely than men to fantasize about sex with the current partner, and less likely than men to fantasize about group sex, sex with strangers, extradyadic relationships, and sex with (legally) much younger partners. This is interpreted as fantasies reflecting sex-differentiated mating strategies. However, a substantial proportion of women report fantasies of group sex, sex with unknown men, and sex with men other than their current partner. This suggests that a certain degree of sperm competition has occurred in human evolutionary history, which is corroborated by the relative size of men’s testes in comparison with other primates. Generally (and against expectations), women do not fantasize more about sex with much older partners and famous people. Fantasies involving sexual aggression are very common. Men fantasize more than women about forcing someone to have sex. Some studies report that women fantasize more about being forced to have sex, but others have failed to find this sex differences. Still, more women than men report that the fantasy of being forced to have sex is among their favorites. These fantasies are typically very sexually arousing, but they may challenge evolutionary explanations and the notion of fantasies revealing motivations, as rape is reported to be traumatic and revolting by victims. Several explanations are discussed. Rape fantasies might facilitate intercourse and sexual pleasure in circumstances of psychological ambivalence, when the environment is safe. In women, evidence of a relationship between sexual fantasies and sexual satisfaction is mixed. Sexual satisfaction is unrelated to female coital fantasies and to male fantasies, in general. Many variables that may cause fantasy-related dissatisfaction are discussed; these include fantasies provoking guilt feelings, preference for arousal solely induced by sensory and emotional stimulation, fantasies being used as escapes from relationship problems and other stressors of reality, and lack of adequate sleep leading to greater fantasy-induced arousal.

Relative infrequency of males providing oral sex to the girls in preindustrial and non-Western samples

Men’s Provisioning of Oral Sex, from Part II - Copulatory Adaptations. Gavin Vance. In The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology, pp 271-293, June 2022.

Summary: Men sometimes engage in noncopulatory sexual behaviors, such as cunnilingus and other kinds of sexual foreplay. Men involved in long-term romantic relationships, in particular, tend to provision their partners with oral sex. Potential adaptive functions of cunnilingus in humans are discussed with a focus on the hypothesis that men use oral sex provisioning as part of a general benefit-provisioning, long-term mating strategy. Other potential adaptive functions are also considered, including the infidelity detection hypothesis and several hypotheses concerning sperm competition adaptations. Some research has proposed the possibility that men may use oral sex as a form of infidelity detection, wherein they might be able to smell or taste the semen of rival males in their partner’s vagina. Other research has posited that men might perform cunnilingus in order to induce orgasm in their partners, thereby increasing the amount of sperm retained in her reproductive tract after ejaculation. Still others have suggested that men might perform cunnilingus to increase their own arousal, thus increasing their subsequent ejaculate volume. These adaptive perspectives are couched within the wider literature on oral sex, which includes data regarding the frequency of oral sex in adolescent, preindustrial and non-Western samples, as well as women’s desire for receiving oral sex. Regarding the relative infrequency of cunnilingus in preindustrial and non-Western samples, in particular, men’s provisioning of oral sex is considered as potentially being a part of an evolved cognition for benefit-provisioning mate retention in general, rather than oral sex itself serving a specific adaptive function. Specifically, oral sex may be one type of sexual favor that men, especially those in Western cultures, sometimes provide to their long-term partners. Additional data regarding the increased sexual and relationship satisfaction in women who engage in a wider variety of sexual practices and who more frequently experience orgasm further supports the mate retention hypothesis of men’s provisioning of oral sex. Nevertheless, the available literature investigating these potential adaptive functions is currently insufficient to draw any decisive conclusions. Finally, gaps in the current literature and suggestions for future research that may help determine the evolved nature of men’s oral sex provisioning are discussed.

The apparent similarity between authenticity and honesty has obscured the tension between the two constructs; but honesty can decrease authenticity and dishonesty can increase authenticity

Yours Truly: On the Complex Relationship Between Authenticity and Honesty. Erica R. Bailey, Sheena S. Iyengar. Current Opinion in Psychology, July 8 2022, 101419.

Abstract: Authenticity is defined as being true to yourself, but does being true to yourself always mean being truthful? The apparent similarity between authenticity and honesty has obscured directly scrutinizing possible tension between the two constructs. In the current paper, we review recent research which reveals their orthogonality, highlighting how honesty can decrease authenticity and dishonesty can increase authenticity. In addition, we delineate between honesty with the self and self-rated authenticity, as well as honesty with others and perceived authenticity. Finally, we propose the importance of coherence and morality which describe when honesty will serve (or harm) authenticity both intra- and interpersonally, illuminating avenues for future research.

People reliably report that their “true self”, the often-cited source of authenticity, is more moral and generally better than the true selves of others.

Visual imagery vividness declines across the lifespan; more pronounced in males

Visual imagery vividness declines across the lifespan. Erzsébet Gulyás et al. Cortex, July 9 2022.

Abstract: The capacity to elicit vivid visual mental images varies within an extensive range across individuals between hyper- and aphantasia. It is not clear, however, whether imagery vividness is constant across the lifespan or changes during development and later in life. Without enforcing the constraints of strict experimental procedures and representativity across the entire population, our purpose was to explore the self-reported level of imagery vividness and determine the relative proportions of aphantasic/hyperphantasic participants in different age groups. Relying on the frequently used Vividness of Visual Imagery Questionnaire, we collected data on a random sample of 2252 participants between the ages of 12 to 60 years. We found a novel developmental pattern that describes a declining ability to elicit vivid visual mental images in the group averages of different age groups from adolescence to middle age. This effect involves both a decreasing proportion of individuals with vivid visual imagery vividness and an increasing proportion of individuals with low imagery vividness as maturation (based on bone age assessments in adolescents) and ageing progress. These findings may shed some light on the developmental mechanisms of our internal, stimulus-independent processes, and might also help to determine genetic, maturational, and age-dependent factors in the cases of hyper- and aphantasia.

Keywords: imageryaphantasiadevelopmentmaturationlifespan

4. Discussion and conclusions

We examined whether visual imagery vividness is constant across the lifespan, or whether it changes during development and later in life. Our results show - for the first time - that visual imagery vividness declines with age, and this decline is more pronounced in males than females. Above average imagery vividness is common during the teenage years, while the proportion of hyperphantasics sharply declines from adolescence to middle age. Aphantasia, on the other hand, is non-existent in adolescents, and seems to become increasingly prevalent in the later years. Additionally, in 11 to13-year-old adolescents, advanced biological maturity (measured via bone age assessment) is correlated with weaker visual imagery vividness. We interpret these findings as evidence for the waning of imagery vividness as a function of chronological age between adolescence and middle age, and as a function of biological age in adolescents.

We believe that the discovered developmental changes in visual imagery vividness and in the prevalence of aphantasia are novel findings. In terms of visual mental imagery and ageing, there exist different experimental approaches, as well as studies on mental rotation, visuo-spatial internal representation, and visual working memory (for recent examples see: Craik & Dirkx, 1992Dror & Kosslyn, 1994Isaac & Marks, 1994Wimmer et al., 2015) trying to define and model the phenomenon of visual internal representations. However, these studies approach mental imagery from a stimulus-response, functional perspective of short-term memory, while our study looks at the development of external stimulus independent visual mental imagery. The latter could avoid the potential biases of perceptual changes or decline due to ageing.

Our results contradict some of the already heterogeneous results of earlier studies measuring visual imagery vividness over the lifespan mentioned in the introduction (Isaac & Marks, 1994Campos & Sueiro, 1993Kemps & Newson, 2005White et al., 1977Wolmer et al., 1999). We noted that these studies use comparatively small sample sizes, limited age-based distribution, and other artefacts, which may contribute to inconsistent findings. The above described, age-related declining pattern of imagery vividness seems to provide a fresh and more coherent picture, and perhaps an alternative way of thinking about the background of internal representations. Our results may also shed light on the necessity of more representative surveys in this field to get more persuasive information about the maturational effects of the phenomenon.

Our observation on the remarkable distribution of the two extremes – namely hyper- and aphantasia – is also unique in the literature. Most previous studies on aphantasia look at its role in different cognitive functions, and potential impairments or compensative internal processes, mainly only in adult samples (for recent examples, see: Jacobs et al., 2018Pounder et al., 2018Keogh et al., 2021Milton et al., 2021Wicken et al., 2021). However, to understand the phenomenon more comprehensively, it would be essential to examine the nature of lifelong prevalence as well. The fact that both chronological and biological age are negatively correlated with visual imagery vividness seems to uncover a developmental process and indicates the existence of “developmental aphantasia” in addition to the potentially genetically based and acquired forms.

The other terminus of the visual imagery vividness spectrum is the phenomenon of hyperphantasia (Zeman, 2020). In contrast to aphantasia, this kind of extreme, ’offline-perceptual’ experience means to have abnormally strong, or photo-like, even eidetic imagery. According to the previous prevalence calculations, this mental representational ability is more frequent in the group of elementary-school-aged children, than among subjects in other age groups (Giray et al., 1976Haber, 1979Haber & Haber, 1964). Different theoretical approaches exist to explain this distributional pattern of which the most popular viewpoint is the developmental hypothesis (Haber, 1979Haber & Haber, 1964). According to this assumption, extreme visual imagery vividness is an early capacity, modulated or lost by the progression of developmental processes during childhood. Nevertheless, this aspect could not necessarily provide a reliable explanation to any longitudinal observations, namely to the cases within the eidetic subjects that remained eidetically classified in the entire experimental time interval (Leask et al., 1969). Based on our findings, we would like to suggest that in addition to the genetically based neurodiversity along the visual imagery spectrum, a lifelong developmental pattern of decreasing visual imagery vividness is also part of the picture. The mechanism behind this decline and the neural background is not within the scope of our investigation here, however, we hope to facilitate a more detailed investigation of the neural correlates.

Inspired by our current findings we propose that the vividness of visual mental imagery is shaped by developmental factors, and there is a natural tendency for less vivid mental images with both maturation and ageing (see Fig. 2). Although we leave the possibility open that there might be a small proportion of individuals with genetically based hyper- or aphantasia whose imaging capacities are unaffected by maturational or developmental factors, we also claim the relevance of the developmental changes. As for future studies, this relevance might be twofold. On one hand, by acknowledging the changing distributions of imaging capacities, future studies might involve samples more representative for age and gender to determine the actual prevalence of either, potentially genetically based extremes. On the other hand, the clear declining tendency raises several questions about the developmental mechanisms that bring about such a remarkable change. For example, is there a difference between genetically based and developmental hyper- and aphantasia?

Fig. 2Fig. 2

Instead of indulging in further exciting but unanswered questions, let us also note the limitations of our exploratory study that could be overcome in further investigations. First, despite the large number of participants in the adult age groups, our study cannot be considered representative, and it is not longitudinal. Therefore, we cannot completely rule out confounds related to random samples, and confounds that may include social, educational, technological, or lifestyle changes over time that may affect the spectrum of mental imagery vividness across the examined age groups. It would be very important to systematically study these potential confounds in future studies. Additionally, although unlikely, we cannot rule out the possibility that aphantasics from older age brackets were more inclined to participate in our study, e.g., by being overrepresented among the readers of the news portal where the invitation link of the study was published. Attrition bias might also be present if, e.g., mortality would decrease in the presence of aphantasia, or increase in the general and hyperphantasic population. The latter effect, that is, the relative decrease in the number of people with high imagery vividness in the population might be due to a confound with psychiatric or neurodegenerative diseases reducing life expectancy (Ji et al., 2019Pearson et al., 2013Pearson et al., 2015). It is also a shortcoming of this exploratory study that we used a self-report questionnaire that is subject to several response biases, and it may not be readily applicable in children.

Since it seems relevant to extend the current investigation to childhood, where over-reporting of imagery experience might be an issue, more objective measures involving lower levels of cognitive complexity are called for. For example, a no-report version (Frässle et al. 2014Ziman et al., 2022) of the binocular rivalry dominance priming method (Milton et al., 2021Pearson et al., 2008, 201; Keogh & Pearson 2018) might be a useful paradigm in forthcoming studies. The essence of this method is that there is an imagery instruction before each rivalry trial, and the induced mental image is expected to affect perceptual decisions about the multistable stimulus (Pearson et al., 2008). The facilitatory effect correlates with the subjective vividness reports (Pearson et al., 2011), and it is not present in subjects with aphantasia (Keogh & Pearson 2018). Although this method seems to deal with the subjectivity of self-reports, the rivalry paradigm is still short of objectivity since participants intentionally report their subjective percepts on each primed rivalry trial, involving criterion level problems, and individual results suggest on demand responses in a significant number of catch trials (Pearson et al., 2011). To solve this issue, a ‘no-report’ version of the rivalry paradigm, based on eye-tracking has been introduced (Frässle et al, 2014Ziman et al., 2022). Another recently introduced method for the objective study of aphantasia uses the pupillary light response (Kay et al. 2022). During imagery of light or dark objects, the pupils react similarly as in natural vision: they dilate while imaging dark stimuli and constrict while imaging bright stimuli. Kay et al. (2022) found that the degree of imagery-evoked pupillary light response correlates with the proportion of successful priming in the binocular rivalry task and seems to be absent in aphantasia. Since intentional behavioural responses are not required (e.g., choices of questionnaire alternatives or button presses), while behavioural correlates of imagery vividness can be measured, these paradigms are good candidates for future objective studies of visual imagery vividness.

The lifelong changes in visual imagery vividness found in the current study should encourage future research to establish advanced, more objective techniques to measure vividness to determine exact age group standards that should help more precise prevalence estimations of hyper- or aphantasia. In addition to the prevalence estimations, the neural background of these conditions might be better revealed relying on the developmental information confirmed by objective methods, which should, in turn, help the understanding of visual imagery in general.

To sum up, we found a novel developmental pattern showing a declining ability to elicit vivid visual images as age increases from adolescence to middle age. This effect involves both a decreasing proportion of individuals with very vivid visual imagery and an increasing proportion of individuals with weak visual imagery as maturation and ageing progress. These findings may shed some light on the developmental mechanisms of our internal, stimulus-independent processes, and might also help to determine genetic, maturational, and age-dependent factors in the cases of hyper- and aphantasia.