Can side effect expectations be assessed implicitly? A comparison of explicit and implicit expectations of vaccination side effects.

OBJECTIVE: Treatment expectations alter the probability of experiencing unpleasant side effects from an intervention, including vaccinations. To date, expectations have mostly been assessed explicitly bearing the risk of bias. This study aims to compare implicit expectations of side effects from COVID-19 and flu vaccinations and to examine their relationships with vaccine attitudes and intentions. METHODS: N = 248 participants took part in a cross-sectional online survey assessing explicit and implicit expectations, as well as vaccine-related attitudes and personal characteristics. A Single Category Implicit Association Test (SC-IAT) was developed to assess implicit side effect expectations. Explicit side effect expectations were measured with the Treatment Expectation Questionnaire (TEX-Q). RESULTS: Whereas explicit and implicit expectations regarding COVID-19 vaccine were significantly correlated (r = -0.325, p < .001), those correlations could not be found regarding flu vaccine (r = -0.072, p = .32). Explicit measures (COVID-19: ß = -0.576, p < .001; flu: ß = -0.301, p < .001) predicted the intention to receive further vaccinations more than implicit measures (COVID-19: ß = -0.005, p = .93; flu: ß = 0.004, p = .96). Explicit measures (COVID-19: OR = 0.360, p < .001; flu: OR = 0.819, p = .03) predicted vaccination status, while implicit measures did not (COVID- 19: OR = 2.643, p = .35; flu: OR = 0.829, p = .61). CONCLUSION: Expectations to experience side effects from vaccinations can be measured implicitly, in addition to explicit measures. Further investigation needs to determine the relative contribution and additive value of using implicit measures to assess treatment expectations.

Therapist's warmth and competence increased positive outcome expectations and alliance in an analogue experiment.

Objective: The quality of the therapeutic alliance, treatment motivation, outcome expectations (OE), and specific health behaviour predicts psychotherapy success. Therapists should be able to improve these factors to optimize outcomes. This study investigated the therapist's interpersonal behaviour to optimize alliance, motivation, OE, and health behaviour. Method: A stressed study sample (N = 465) completed an online analogue experiment. We gave participants positive information about psychotherapy effectiveness and varied the therapist's interpersonal behaviour along the dimensions of warmth and competence.Results: High (vs. low) competence and high (vs. low) warmth increased alliance, OE, and help-seeking scores, while high (vs. low) competence increased motivation to do psychotherapy. We found no effects on health behaviour.Conclusion: In contrast to previous correlational analyses, our experimental study supports the causal role of the therapist's warmth and competence and its impact on alliance, motivation, and OE. We discuss approaches for future studies and clinical implications.

Spotlight on the Left Frontal Cortex: No Evidence for Response Inhibition from Cathodal High-Definition transcranial Direct Current Stimulation over Left Inferior Frontal Gyrus or Left Dorsolateral Prefrontal Cortex.

Inhibitory control functions draw on a fronto-basal network with central cortical hubs at the right inferior frontal gyrus (IFG) and the pre-SMA. However, few neuropsychological studies investigated the role of brain regions in the left frontal cortex and some previous evidence from bilateral studies remained inconclusive. This study presents a systematic investigation with high-definition transcranial direct current stimulation (HD tDCS) in a focal 4 × 1 configuration, which was used to target the left IFG or the left dorsolateral prefrontal cortex (DLPFC) with 1-mA active or sham cathodal HD tDCS. Healthy participants were randomized into three groups. We analyzed performance in an adaptive stop-signal task to quantify inhibitory control before (baseline), during cathodal HD tDCS (on-line), and after cathodal HD tDCS (off-line) to either left IFG, left DLPFC, or sham. Results from 67 participants and Bayesian analyses indicated moderate evidence against an effect of cathodal tDCS (left DLPFC and left IFG compared with sham) regardless of timing, that is, on-line or off-line cathodal HD tDCS. The study results are examined in view of previous neuropsychological and neurostimulation studies with bilateral and unilateral cathodal tDCS in healthy and patient samples. Theoretically, our results are compatible with a right-lateralization of response inhibition functions and suggest a negligible role of the left frontal hemisphere in healthy participants, but more stimulation parameters can be still explored in the left hemisphere. In line with previous studies, right inferior frontal gyrus seems a more promising target to investigate or alleviate response inhibition with tDCS.

Fear Memory Retrieval Is Associated With a Reduction in AMPA Receptor Density at Thalamic to Amygdala Intercalated Cell Synapses.

The amygdala plays a crucial role in attaching emotional significance to environmental cues. Its intercalated cell masses (ITC) are tight clusters of GABAergic neurons, which are distributed around the basolateral amygdala complex. Distinct ITC clusters are involved in the acquisition and extinction of conditioned fear responses. Previously, we have shown that fear memory retrieval reduces the AMPA/NMDA ratio at thalamic afferents to ITC neurons within the dorsal medio-paracapsular cluster. Here, we investigate the molecular mechanisms underlying the fear-mediated reduction in the AMPA/NMDA ratio at these synapses and, in particular, whether specific changes in the synaptic density of AMPA receptors underlie the observed change. To this aim, we used a detergent-digested freeze-fracture replica immunolabeling technique (FRIL) approach that enables to visualize the spatial distribution of intrasynaptic AMPA receptors at high resolution. AMPA receptors were detected using an antibody raised against an epitope common to all AMPA subunits. To visualize thalamic inputs, we virally transduced the posterior thalamic complex with Channelrhodopsin 2-YFP, which is anterogradely transported along axons. Using face-matched replica, we confirmed that the postsynaptic elements were ITC neurons due to their prominent expression of µ-opioid receptors. With this approach, we show that, following auditory fear conditioning in mice, the formation and retrieval of fear memory is linked to a significant reduction in the density of AMPA receptors, particularly at spine synapses formed by inputs of the posterior intralaminar thalamic and medial geniculate nuclei onto identified ITC neurons. Our study is one of the few that has directly linked the regulation of AMPA receptor trafficking to memory processes in identified neuronal networks, by showing that fear-memory induced reduction in AMPA/NMDA ratio at thalamic-ITC synapses is associated with a reduced postsynaptic AMPA receptor density.

Midbrain dopaminergic inputs gate amygdala intercalated cell clusters by distinct and cooperative mechanisms in male mice.

Dopaminergic signaling plays an important role in associative learning, including fear and extinction learning. Dopaminergic midbrain neurons encode prediction error-like signals when threats differ from expectations. Within the amygdala, GABAergic intercalated cell (ITC) clusters receive one of the densest dopaminergic projections, but their physiological consequences are incompletely understood. ITCs are important for fear extinction, a function thought to be supported by activation of ventromedial ITCs that inhibit central amygdala fear output. In mice, we reveal two distinct novel mechanisms by which mesencephalic dopaminergic afferents control ITCs. Firstly, they co-release GABA to mediate rapid, direct inhibition. Secondly, dopamine suppresses inhibitory interactions between distinct ITC clusters via presynaptic D1 receptors. Early extinction training augments both GABA co-release onto dorsomedial ITCs and dopamine-mediated suppression of dorso- to ventromedial inhibition between ITC clusters. These findings provide novel insights into dopaminergic mechanisms shaping the activity balance between distinct ITC clusters that could support their opposing roles in fear behavior.

Layer- and subregion-specific electrophysiological and morphological changes of the medial prefrontal cortex in a mouse model of neuropathic pain.

Chronic neuropathic pain constitutes a serious public health problem, but the disease mechanisms are only partially understood. The involvement of different brain regions like the medial prefrontal cortex has already been established, but the comparison of the role of different subregions and layers is still inconclusive. In the current study, we performed patch-clamp recordings followed by anatomical reconstruction of pyramidal cells from different layers of the prelimbic and infralimbic subregions of the medial prefrontal cortex in neuropathic (spared nerve injury, SNI) and control mice. We found that in the prelimbic cortex, layer 2/3 pyramidal cells from SNI mice exhibited increased excitability compared to sham controls, whereas prelimbic layer 5 pyramidal neurons showed reduced excitability. Pyramidal cells in both layer 2/3 and layer 5 of the infralimbic subregion did not change their excitability, but layer 2/3 pyramidal cells displayed increased dendritic length and branching. Our findings support the view that chronic pain is associated with subregion- and layer-specific changes in the medial prefrontal cortex. They therefore provide new insights into the mechanisms underlying the chronification of pain.

Combined Optogenetic and Freeze-fracture Replica Immunolabeling to Examine Input-specific Arrangement of Glutamate Receptors in the Mouse Amygdala.

Freeze-fracture electron microscopy has been a major technique in ultrastructural research for over 40 years. However, the lack of effective means to study the molecular composition of membranes produced a significant decline in its use. Recently, there has been a major revival in freeze-fracture electron microscopy thanks to the development of effective ways to reveal integral membrane proteins by immunogold labeling. One of these methods is known as detergent-solubilized Freeze-fracture Replica Immunolabeling (FRIL). The combination of the FRIL technique with optogenetics allows a correlated analysis of the structural and functional properties of central synapses. Using this approach it is possible to identify and characterize both pre- and postsynaptic neurons by their respective expression of a tagged channelrhodopsin and specific molecular markers. The distinctive appearance of the postsynaptic membrane specialization of glutamatergic synapses further allows, upon labeling of ionotropic glutamate receptors, to quantify and analyze the intrasynaptic distribution of these receptors. Here, we give a step-by-step description of the procedures required to prepare paired replicas and how to immunolabel them. We will also discuss the caveats and limitations of the FRIL technique, in particular those associated with potential sampling biases. The high reproducibility and versatility of the FRIL technique, when combined with optogenetics, offers a very powerful approach for the characterization of different aspects of synaptic transmission at identified neuronal microcircuits in the brain. Here, we provide an example how this approach was used to gain insights into structure-function relationships of excitatory synapses at neurons of the intercalated cell masses of the mouse amygdala. In particular, we have investigated the expression of ionotropic glutamate receptors at identified inputs originated from the thalamic posterior intralaminar and medial geniculate nuclei. These synapses were shown to relay sensory information relevant for fear learning and to undergo plastic changes upon fear conditioning.