Multidisciplinary investigation links backward-speech trait and working memory through genetic mutation

Case studies of unusual traits can provide unique snapshots of the effects of modified systems. In this study, we report on an individual from a Serbian family with the ability to rapidly, accurately and voluntarily speak backwards. We consider psychological, neural and genetic correlates of this trait to identify specific relevant neural mechanisms and new molecular pathways for working memory and speech-related tasks. EEG data suggest that the effect of word reversal precedes semantic integration of visually presented backward-words, and that event-related potentials above the frontal lobe are affected by both word reversal and the maintenance of backward-words in working memory. fMRI revealed that the left fusiform gyrus may facilitate the production of backward-speech. Exome sequencing identified three novel coding variants of potential significance in the RIC3, RIPK1 and ZBED5 genes. Taken together, our data suggest that, in this individual, the ability to speak backwards is afforded by an extraordinary working memory capacity. We hypothesise that this is served by cholinergic projections from the basal forebrain to the frontal cortex and supported by visual semantic loops within the left fusiform gyrus and that these neural processes may be mediated by a genetic mutation in RIC3; a chaperone for nicotinic acetylcholine receptors

Attenuation of N2 amplitude of laser-evoked potentials by theta burst stimulation of primary somatosensory cortex

Theta burst stimulation (TBS) is a special repetitive transcranial magnetic stimulation (rTMS) paradigm, where bursts of low-intensity stimuli are applied in the theta frequency. The aim of this study was to investigate the effect of neuronavigated TBS over primary somatosensory cortex (SI) on laser-evoked potentials (LEPs) and acute pain perception induced with Tm : YAG laser stimulation. The amplitude changes of the N1, N2, and P2 components of LEPs and related subjective pain rating scores of 12 healthy subjects were analyzed prior to and following continuous TBS (cTBS), intermittent TBS (iTBS), intermediate TBS (imTBS), and sham stimulation. Our results demonstrate that all active TBS paradigms significantly diminished the amplitude of the N2 component, when the hand contralateral to the site of TBS was laser-stimulated. Sham stimulation condition had no significant effect. The subjective pain perception also decreased during the experimental sessions, but did not differ significantly from the sham stimulation condition. The main finding of our study is that TBS over SI diminished the amplitude of the N2 component evoked from the contralateral side without any significant analgesic effects. Furthermore, imTBS produced responses similar to those observed by other forms of TBS induced excitability changes in the SI

12 tDCS modulation of pavlovian bias under intermittent loss of control

Objectives/Aims Learning from experience and making decisions based on integrated environmental feedback is crucial for human functioning and wellbeing. Difficulties in learning and decision-making have been found in several psychiatric conditions. Pavlovian bias, a tendency to approach reward and remain passive in the face of punishment, can be advantageous in some situations, while in others, it can lead to maladaptive decisions and needs to be overcome by cognitive control. It has been suggested that healthy humans rely more heavily on Pavlovian bias when instrumental control over environmental reinforcers is compromised. In our study, we were focusing on the influence of transcranial direct current stimulation (tDCS) on Pavlovian bias during and after an intermittent loss of control over rewards and losses. Methods In our pilot study, 19 adults underwent three blocks of an orthogonalized go-nogo reinforcement learning task. Blocks 1 and 3 had a response-feedback contingency of 70–30%, enabling learning via trial-and-error. In the second block, the outcome was independent of the participants’ responses (50%-50% contingency level). Cortical responses of all participants were recorded via EEG. Multi-electrode tDCS targeting the medial prefrontal cortex was administered in a randomised, double-blind placebo-controlled manner. Results We conducted a repeated-measures ANOVA with ‘session’ (PRE x tDCS x POST), ‘valence’ (Win x Avoid) and ‘PB-congruency’ (Pavlovian bias congruent x incongruent) as within-factors, ‘group’ (Active stimulation x Sham) as the between- factor and ‘accuracy’ as the dependent variable. The interaction of ‘session’ and ‘PB- congruency’ with F(2,16)=2.62, p=0.09 were marginally significant, pointing towards slightly enhanced Pavlovian bias in the second block. However, the interaction of ‘session’, ‘PB-congruency’ and ‘group’ was not significant (F(2,16)=0.46, p=0.63). The evaluation of the feedback-related negativity (FRN) in the EEG revealed gradually increasing amplitudes in reward trials in the sham group, whereas we found a trend towards reduced FRN amplitude in the active group with F(2,13)=2.83, p=0.08. Conclusions Our preliminary data show that a loss of control over feedbacks might increase the effect of Pavlovian bias on the choices of all participants. Although active tDCS seems to attenuate cortical responses during feedback evaluation, this effect is not accompanied by alterations in choice behaviour. Our data collection is still ongoing. The results from the full sample of 50 participants will be analysed by February 2020