Biology subjects

Becker, B.

Publications and source records attributed to Becker, B..

94 records · Page 6Linked to original sources

bioRxiv2018

Shifted balance of dorsal versus ventral striatal communication with frontal reward and regulatory regions in cannabis dependence

The transition from voluntary to addictive behavior is characterized by a loss of regulatory control in favor of reward driven behavior. Animal models indicate that this process is neurally underpinned by a shift in ventral to dorsal striatal control of behavior, however this shift has not been directly examined in humans. Against this background the present resting state fMRI study employed a two-step approach to (1) precisely map striatal alterations using a novel, data-driven network classification strategy combining Intrinsic Connectivity Contrast (ICC) with Multivoxel Pattern Analysis (MVPA) and, (2) to determine whether a ventral to dorsal striatal shift in connectivity with reward and and regulatory control regions can be observed in abstinent (28 days) male cannabis-dependent individuals (n = 24) relative to matched controls (n = 28). Network classification revealed that the groups can be reliably discriminated by global connectivity profiles of two striatal regions that mapped onto the ventral (nucleus accumbens) and dorsal striatum (caudate). Subsequent functional connectivity analysis demonstrated a relative shift between ventral and dorsal striatal communication with fronto-limbic regions that have been consistently involved in reward processing (rostral ACC) and executive / regulatory functions (dorsomedial PFC). Specifically, in the cannabis dependent subjects connectivity between the ventral striatum with the rostral ACC increased, whereas both striatal regions were uncoupled from the regulatory dorsomedial PFC. Together these findings suggest a shift in the balance between dorsal and ventral striatal control in cannabis dependence. Similar changes have been observed in animal models and may promote the loss of control central to addictive behavior.

neuroscience↗

bioRxiv2018

Altered Reward Processing in Abstinent Dependent Cannabis Users: Social Context Matters

Public perception of cannabis as relatively harmless, alongside claimed medical benefits, have led to moves towards its legalization. Yet, long-term consequences of cannabis dependence, and whether they differ qualitatively from other drugs, are still poorly understood. A key feature of addictive drugs is that chronic use leads to adaptations in reward processing, blunting responsivity to the substance itself and other rewarding stimuli. Against this background, the present study investigated whether cannabis dependence is associated with reductions in hedonic representations by measuring behavioral and neural responses to social reward in 23 abstinent cannabis-dependent men and 24 matched non-using controls. In an interpersonal pleasant touch fMRI paradigm, participants were led to believe they were in physical closeness of or touched (CLOSE, TOUCH) by either a male or female experimenter (MALE, FEMALE), allowing the assessment of touch- and social context-dependent (i.e. female compared to male social interaction) reward dynamics.\n\nUpon female compared to male touch, dependent cannabis users displayed a significantly attenuated increase of reward experience compared to healthy controls. Controls responded to female as compared to male interaction with increased striatal activation whereas cannabis users displayed the opposite activation pattern, with stronger alterations being associated with a higher lifetime exposure to cannabis. Neural processing of pleasant touch in dependent cannabis users remained intact.\n\nThese findings demonstrate that cannabis dependence in men is linked to similar lasting neuroadaptations in striatal responsivity to hedonic stimuli as observed for other drugs of abuse. However, reward processing deficits seem to depend on the social context.

neuroscience↗

bioRxiv2018

Sex- and Context-dependent Effects of Oxytocin on Social Reward Processing

We interact socially and form bonds with others because such experiences are rewarding. However, an insecure attachment style or social anxiety can reduce these rewarding effects. The neuropeptide oxytocin (OXT) may facilitate social interactions either by increasing their rewarding experience or by attenuating anxiety, although effects can be sex- and attachment-style dependent. In this study, 64 pairs of same-sex friends completed a social sharing paradigm in a double-blind, placebo-controlled, between-subject design with one friend inside an MRI scanner and the other in a remote behavioral testing room. In this way we could examine whether intranasal-OXT differentially modulated the emotional impact of social sharing and associated neural processing. Additionally, we investigated if OXT effects were modulated by sex and attachment style. Results showed that in women, but not men, OXT increased ratings for sharing stimuli with their friend but not with a stranger, particularly in the friend in the scanner. Corresponding neuroimaging results showed that OXT decreased both amygdala and insula activity as well as their functional connectivity in women when they shared with friends but had the opposite effect in men. On the other hand, OXT did not enhance responses in brain reward circuitry. In the PLC treated group amygdala responses in women when they shared pictures with their friend were positively associated with attachment anxiety and OXT uncoupled this. Our findings demonstrate that OXT facilitates the impact of sharing positive experiences with others in women, but not men, and that this is associated with differential effects on the amygdala and insula and their functional connections. Furthermore, OXT particularly reduced increased amygdala responses during sharing in individuals with higher attachment anxiety. Thus, OXT effects in this context may be due more to reduced anxiety when sharing with a friend than to enhanced social reward.

neuroscience↗

bioRxiv2017

New barcoded primers for efficient retrieval of cercozoan sequences in high-throughput environmental diversity surveys, with emphasis on worldwide biological soil crusts

We describe the performance of a new metabarcoding approach to investigate the environmental diversity of a prominent group of widespread unicellular organisms, the Cercozoa. Cercozoa is an immensely large group of protists and although it may dominate in soil and aquatic ecosystems, its environmental diversity remains undersampled. We designed PCR primers targeting the hyper-variable region V4 of the small subunit ribosomal RNA (SSU or 18S) gene, which is the recommended barcode marker for Cercozoa. The length of the amplified fragment (ca. 350 bp) is suitable for Illumina MiSeq, the most cost-effective platform for molecular environmental surveys. We provide barcoded primers, an economical alternative to multiple libraries for multiplex sequencing of over a hundred samples. In silico, our primers matched 68% of the cercozoan sequences of the reference database and performed better than previously proposed new generation sequencing primers. In mountain grasslands soils and in biological soil crusts from a variety of climatic regions, we were able to detect cercozoan sequences encompassing nearly the whole range of the phylum. We obtained 901 OTUs at 97% similarity threshold from 26 samples, with ca. 50,000 sequences per site, and only 8% of non-cercozoan sequences. We could contribute to a further increase of the diversity of Cercozoa, since only 43% of the OTUs were 97-100% similar to any known sequence. Our study thus provides an advanced tool for cercozoan metabarcoding and to investigate their diversity and distribution in the environment.

bioinformatics↗