Biology subjects

Chakrabarti, B.

Publications and source records attributed to Chakrabarti, B..

7 recordsLinked to original sources

bioRxiv2018

The true size of placebo analgesia: Concordant neural and behavioural measures of placebo analgesia during experimental acute pain

Placebo analgesia refers to the reduction of pain following the administration of an inactive treatment. While most clinical trials compare a drug treatment against a placebo to determine the efficacy of the analgesic, most experimental studies of placebo analgesia do not include a real analgesic condition. A direct comparison of placebo against a real analgesic can inform us about the true size of the placebo effect. To this end, we aimed to provide a robust estimate of placebo analgesia by contrasting the effect of pain relief expectation from an inert cream (vaseline) against a real topical analgesic agent (lidocaine) applied on two different limbs and their respective control conditions. Pain reports and electroencephalography (EEG) responses triggered by laser nociceptive stimulation were collected. Forty typical healthy adults were enrolled in a double-blind randomized within-subject study where a standard placebo induction script of verbal suggestions in a sham medical setting was used to enhance the expectation on treatment outcome. In line with the earliest studies of placebo analgesia, majority (30 of 40) of participants was placebo responders, i.e. they reported lower pain to the placebo treatment. Placebo responders reported low pain and displayed low laser evoked potentials (LEPs) amplitude for both the analgesic and placebo treatment limbs compared to the respective control limbs. Placebo analgesia correlated positively with the amplitude of the LEPs, thus establishing convergent validity of the findings. This study provides a robust estimate of the neural and behavioural measures of placebo analgesia, in comparison to a real analgesic. These estimates can help inform the quantitative criteria for similar neural and behavioural measures in assessing the effectiveness of a real drug in placebo controlled trials.

neuroscience↗

bioRxiv2017

Systemizing is genetically correlated with autism and is genetically distinct from social autistic traits

The core diagnostic criteria for autism comprise two symptom domains - social and communication difficulties, and unusually repetitive and restricted behaviour, interests and activities. There is some evidence to suggest that these two domains are dissociable, yet, this hypothesis has not been tested using molecular genetics. We test this using a GWAS of a non-social autistic trait, systemizing (N = 51,564), defined as the drive to analyse and build systems. We demonstrate that systemizing is heritable and genetically correlated with autism. In contrast, we do not identify significant genetic correlations between social autistic traits and systemizing. Supporting this, polygenic scores for systemizing are significantly positively associated with restricted and repetitive behaviour but not with social difficulties in autistic individuals. These findings strongly suggest that the two core domains of autism are genetically dissociable, and point at how to fractionate the genetics of autism.

genetics↗

bioRxiv2017

Reprogramming, oscillations and transdifferentiation in epigenetic landscapes

Waddingtons epigenetic landscape provides a phenomenological understanding of the cell differentiation pathways from the pluripotent to mature lineage-committed cell lines. In light of recent successes in the reverse programming process there has been significant interest in quantifying the underlying landscape picture through the mathematics of gene regulatory networks. We investigate the role of time delays arising from multistep chemical reactions and epigenetic rearrangement on the cell differentiation landscape for a realistic two-gene regulatory network, consisting of selfpromoting and mutually inhibiting genes. Our work provides the first theoretical basis of the transdifferentiation process in the presence of delays, where one differentiated cell type can transition to another directly without passing through the undifferentiated state. Additionally, the interplay of time-delayed feedback and a time dependent chemical drive leads to long-lived oscillatory states in appropriate parameter regimes. This work emphasizes the important role played by time-delayed feedback loops in gene regulatory circuits and provides a framework for the characterization of epigenetic landscapes.

systems biology↗

bioRxiv2017

Perceived closeness and autistic traits modulate interpersonal vocal communication

Vocal modulation is a critical component of interpersonal communication. It not only serves as a dynamic and flexible tool for self-expression and linguistic information but also plays a key role in social behaviour. Variation in vocal modulation can be driven by individual traits of the individual interlocutors, as well as by factors relating to the dyad, such as the perceived closeness between interlocutors. Accordingly, the current study examines the role of a) individual differences in autism-related traits, and b) perceived closeness between interlocutors on vocal modulation. Since lack of appropriate vocal modulation is often associated with Autism Spectrum Disorders we also focus on autism-related individual traits. The role of these individual and dyad-level factors on vocal modulation is tested for cultural generalizability by conducting this study in three separate samples from India, Italy, and the UK. Articulatory features were extracted from recorded conversations between a total of 85 same-sex pairs of participants and correlated with their self-reported perceived closeness (CR) to the other member of the pair and with the individual Autism Spectrum Quotient (AQ). Results indicated a significant positive correlation between interpersonal closeness and articulation area in all three samples. A significant negative correlation between AQ and articulation area was observed only in the UK sample. This study thus provides novel insights into determinants of interpersonal vocal communication and a test of their cultural generalizability.

animal behavior and cognition↗

bioRxiv2017

Individual differences in responsivity to social rewards: Insights from two eye-tracking tasks

Humans generally prefer social over nonsocial stimuli from an early age. Reduced preference for social rewards has been observed in individuals with autism spectrum conditions (ASC). This preference has typically been noted in separate tasks that measure orienting toward and engaging with social stimuli. In this experiment, we used two eye-tracking tasks to index both of these aspects of social preference in in 77 typical adults. We used two measures, global effect and preferential looking time. The global effect task measures saccadic deviation toward a social stimulus (related to orienting), while the preferential looking task records gaze duration bias toward social stimuli (relating to engaging). Social rewards were found to elicit greater saccadic deviation and greater gaze duration bias, suggesting that they have both greater salience and higher value compared to nonsocial rewards. Trait empathy was positively correlated with the measure of relative value of social rewards, but not with their salience. This study thus elucidates the relationship of empathy with social reward processing.

animal behavior and cognition↗

bioRxiv2016

Looking at my own Face: Visual Processing Strategies in Physical Self-representation

We live in an age of selfies. Yet, how we look at our own faces has seldom been systematically investigated. In this study we test if visual processing of self-faces is different from other faces, using psychophysics and eye-tracking. Specifically, the association between the psychophysical properties of self-face representation and visual processing strategies involved in self-face recognition was tested. Thirty-three adults performed a self-face recognition task from a series of self-other face morphs with simultaneous eye-tracking. Participants were found to look at lower part of the face for longer duration for self-face compared to other-face. Participants with a reduced overlap between self and other face representations, as indexed by a steeper slope of the psychometric response curve for self-face recognition, spent a greater proportion of time looking at the upper regions of faces identified as self. Additionally, the association of autism-related traits with self-face processing metrics was tested, since autism has previously been associated with atypical self-processing, particularly in the psychological domain. Autistic traits were associated with reduced looking time to both self and other faces. However, no self-face specific association was noted with autistic traits, suggesting that autism-related features may be related to self-processing in a domain specific manner.

animal behavior and cognition↗

bioRxiv2016

Genome-wide meta-analysis of cognitive empathy: heritability, and correlates with sex, neuropsychiatric conditions and brain anatomy

We conducted a genome-wide meta-analysis of cognitive empathy using the Reading the Mind in the Eyes Test (Eyes Test) in 88,056 research volunteers of European Ancestry (44,574 females and 43,482 males) from 23andMe Inc., and an additional 1,497 research volunteers of European Ancestry (891 females and 606 males) from the Brisbane Longitudinal Twin Study (BLTS). We confirmed a female advantage on the Eyes Test (Cohens d = 0.21, P < 2.2x10-16), and identified a locus in 3p26.1 that is associated with scores on the Eyes Test in females (rs7641347, Pmeta = 1.58 x 10-8). Common single nucleotide polymorphisms (SNPs) explained 5.8% (95% CI: 0.45 - 0.72; P = 1.00 x 10-17) of the total trait variance in both sexes, and we identified a twin heritability of 0.28 (95% CI: 0.13-0.42). Finally, we identified significant genetic correlation between the Eyes Test and anorexia nervosa, measures of empathy (the Empathy Quotient), openness (NEO-Five Factor Inventory), and different measures of educational attainment and cognitive aptitude, and show that the genetic determinants of volumes of the dorsal striatum (caudate nucleus and putamen) are positively correlated with the genetic determinants of performance on the Eyes Test.

genetics↗