Primary visual cortex excitability is not atypical in acquired synaesthesia

Lungu, Laura; Stewart, Ryan; Luke, David; Terhune, Devin Blair

doi:10.1016/j.brs.2019.10.021

Cited by 2 publications

(4 citation statements)

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“…According to this account, excessive serotonin release triggers selective hyperexcitability in visual cortices leading to aberrant perceptual states. This is consistent with visual cortex hyperexcitability in developmental synaesthesia (Terhune et al, 2011; and in trained synaesthesia (Rothen et al, 2018) (see also Lungu et al, 2020). Elsewhere, we have argued that these effects are alone unlikely to produce the hallmark behavioural features of developmental synaesthesia (e.g., automaticity and inducerconcurrent consistency) (Terhune et al, 2016;Terhune et al, 2017).…”

Section: Neurochemical and Neurocognitive Mechanismssupporting

confidence: 83%

“…It has been proposed that excessive levels of serotonin, or serotonin agonists and partial agonists activating 5-HT2A receptors, in cortical neurons is a common mechanism shared by (at least some cases of) developmental, acquired and drug-induced synaesthesia (Brogaard, 2013). In particular, excessive levels of serotonin may trigger synaesthesia through a selective enhancement of cortical excitability in visual cortex (Brogaard, 2013), which is a feature of developmental synaesthesia (Terhune, Murray, Near, Stagg, Cowey & Cohen Kadosh, 2015) and observed in trained synaesthesia (Rothen, Schwartzman, Bor, & Seth, 2018), although not in at least one case of acquired synaesthesia (Lungu, Stewart, Luke, & Terhune, 2020). A recent double-blind, placebo-controlled trial of LSD confirmed that LSD produces perceptual effects resembling synaesthesia, although the induced associations did not display consistency (Terhune et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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The chemical induction of synaesthesia

Luke¹,

Lungu²,

Friday³

et al. 2021

Preprint

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Objective Preliminary research suggests that experiences resembling synaesthesia are frequently reported under the influence of a diverse range of chemical substances although the incidence, chemical specificity, and characteristics of these effects are poorly understood. Methods Here we surveyed recreational drug users and self-reported developmental synaesthetes regarding their use of 28 psychoactive drugs comprising 12 different drug classes and whether they had experienced synaesthesia under the influence of these substances. Results The drug class tryptamines exhibited the highest incidence rates of drug-induced synaesthesia in controls and induction rates of novel forms of synaesthesia in developmental synaesthetes. Induction incidence rates in controls were strongly correlated with the corresponding induction and enhancement rates in developmental synaesthetes. In addition, the use of LSD was the strongest predictor of drug-induced synaesthesia in both controls and developmental synaesthetes. Clear evidence was observed for a clustering of synaesthesia-induction rates as a function of drug class in both groups, denoting non-random incidence rates within drug classes. Sound-colour synaesthesia was the most commonly observed type of induced synaesthesia. Further analyses suggest the presence of synaesthesia-prone individuals, who were more likely to experience drug-induced synaesthesia with multiple drugs. Conclusions These data corroborate the hypothesized link between drug-induced synaesthesia and serotoninergic activity, but also suggest the possibility of alternative neurochemical pathways involved in the induction of synaesthesia. They further suggest that the induction and modulation of synaesthesia in controls and developmental synaesthetes share overlapping mechanisms and that certain individuals may be more susceptible to experiencing induced synaesthesia with different drugs.

show abstract

Section: Neurochemical and Neurocognitive Mechanismssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The chemical induction of synaesthesia

Luke¹,

Lungu²,

Friday³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…According to this account, excessive serotonin release triggers selective hyperexcitability in visual cortices leading to aberrant perceptual states. This is consistent with visual cortex hyperexcitability in developmental synaesthesia (Terhune et al, 2011;Terhune, Song, et al, 2015) and in trained synaesthesia (Rothen et al, 2018; see also Lungu et al, 2020). Elsewhere, we have argued that these effects are alone unlikely to produce the hallmark behavioural features of developmental synaesthesia (e.g., automaticity and inducer-concurrent consistency).…”

Section: Neurochemical and Neurocognitive Mechanismssupporting

confidence: 84%

“…It has been proposed that excessive levels of serotonin, or serotonin agonists and partial agonists activating 5‐HT2A receptors, in cortical neurons is a common mechanism shared by (at least some cases of) developmental, acquired and drug‐induced synaesthesia (Brogaard, 2013). In particular, excessive levels of serotonin may trigger synaesthesia through a selective enhancement of cortical excitability in visual cortex (Brogaard, 2013), which is a feature of developmental synaesthesia (Terhune, Murray, et al., 2015) and observed in trained synaesthesia (Rothen et al., 2018), although not in at least one case of acquired synaesthesia (Lungu et al., 2020). A recent double‐blind, placebo‐controlled trial of LSD confirmed that it produces perceptual effects resembling synaesthesia, although the induced associations did not display consistency (Terhune et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

The chemical induction of synaesthesia

Luke

Lungu

Friday

et al. 2022

Human Psychopharmacology

Self Cite

View full text Add to dashboard Cite

Objective: Preliminary research suggests that experiences resembling synaesthesia are frequently reported under the influence of a diverse range of chemical substances although the incidence, chemical specificity, and characteristics of these effects are poorly understood.Methods: Here we surveyed recreational drug users and self-reported developmental synaesthetes regarding their use of 28 psychoactive drugs from 12 different drug classes and whether they had experienced synaesthesia under the influence of these substances. Results:The drug class of tryptamines exhibited the highest incidence rates of druginduced synaesthesia in controls and induction rates of novel forms of synaesthesia in developmental synaesthetes. Induction incidence rates in controls were strongly correlated with the corresponding induction and enhancement rates in developmental synaesthetes. In addition, the use of lysergic acid diethylamide (LSD) was the strongest predictor of drug-induced synaesthesia in both controls and developmental synaesthetes. Clear evidence was observed for a clustering of synaesthesiainduction rates as a function of drug class in both groups, denoting non-random incidence rates within drug classes. Sound-colour synaesthesia was the most commonly observed type of induced synaesthesia. Further analyses suggest the presence of synaesthesia-prone individuals, who were more likely to experience drug-induced synaesthesia with multiple drugs.Conclusions: These data corroborate the hypothesized link between drug-induced synaesthesia and serotoninergic activity, but also suggest the possibility of alternative neurochemical pathways involved in the induction of synaesthesia. They further imply that the induction and modulation of synaesthesia in controls and developmental synaesthetes share overlapping mechanisms and that certain individuals may be more susceptible to experiencing induced synaesthesia with different drugs.

show abstract

Primary visual cortex excitability is not atypical in acquired synaesthesia

Abstract: Fig. 1. TMS motor and phosphene thresholds in controls and LW (acquired synaesthete). Error bars reflect standard error of the mean and marginal plots reflect kernel density plots.L. Lungu et al. / Brain Stimulation 13 (2020) 341e342

Cited by 2 publications

References 10 publications

The chemical induction of synaesthesia

The chemical induction of synaesthesia

The chemical induction of synaesthesia

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