Bayesian accounts of perceptual decisions in the nonclinical continuum of psychosis : Greater imprecision in both top-down and bottom-up processes

Neurocomputational accounts of psychosis propose mechanisms for how information is integrated into a predictive model of the world, in attempts to understand the occurrence of altered perceptual experiences. Conflicting Bayesian theories postulate aberrations in either top-down or bottom-up processing. The top-down theory predicts an overreliance on prior beliefs or expectations resulting in aberrant perceptual experiences, whereas the bottom-up theory predicts an overreliance on current sensory information, as aberrant salience is directed towards objectively uninformative stimuli. This study empirically adjudicates between these models. We use a perceptual decision-making task in a neurotypical population with varying degrees of psychotic-like experiences. Bayesian modelling was used to compute individuals’ reliance on prior relative to sensory information. Across two datasets (discovery dataset n = 363; independent replication in validation dataset n = 782) we showed that psychotic-like experiences were associated with an overweighting of sensory information relative to prior expectations, which seem to be driven by decreased precision afforded to prior information. However, when prior information was more uncertain, participants with greater psychotic-like experiences encoded sensory information with greater noise. Greater psychotic-like experiences were associated with aberrant precision in the encoding both prior and likelihood information, which we suggest may be related to generally heightened perceptions of task instability. Our study lends empirical support to notions of both weaker bottom-up and weaker (rather than stronger) top-down perceptual processes, as well as = aberrancies in belief updating that extend into the non-clinical continuum of psychosis

Neighbourhoods as commodities : the case of gentrification of Sants-Montjuïc

Premi UAB de la Fundació Autònoma Solidària (FAS) als millors Treballs de Fi de Grau sobre desenvolupament sostenible i justícia global. 5a Edició, curs 2020/2021Affordable housing, sustainable cities and decent lives are at the front page of political, social and economic discussions. With the growing number of population living in cities and the growing global inequalities, fair and equal urbanisation needs to be at the chore of the debate. Gentrification is the tag defining the socioeconomic transformations happening in many neighbourhoods worldwide, where the working class is displaced from their place of residence in favour of higher social classes and for the sake of the capitalists' profits. The causes are numerous and diverse, but one of them is repeated in many Mediterranean cities: tourism. This thesis studies the literature on the production of urban space in capitalist economies with the aim of conducting a quantitative analysis of the process taking place in the district of Sants-Montjuïc, Barcelona. Through the elaboration of a gentrification index, we can corroborate how the seven neighbourhoods are undergoing such process. Moreover, through the analysis of the touristification indicators we can prove that tourism has a big impact in our gentrification study case

Effective connectivity reveals right-hemisphere dominance in audiospatial perception: implications for models of spatial neglect

Detecting the location of salient sounds in the environment rests on the brain's ability to use differences in sounds arriving at both ears. Functional neuroimaging studies in humans indicate that the left and right auditory hemispaces are coded asymmetrically, with a rightward attentional bias that reflects spatial attention in vision. Neuropsychological observations in patients with spatial neglect have led to the formulation of two competing models: the orientation bias and right-hemisphere dominance models. The orientation bias model posits a symmetrical mapping between one side of the sensorium and the contralateral hemisphere, with mutual inhibition of the ipsilateral hemisphere. The right-hemisphere dominance model introduces a functional asymmetry in the brain's coding of space: the left hemisphere represents the right side, whereas the right hemisphere represents both sides of the sensorium. We used Dynamic Causal Modeling of effective connectivity and Bayesian model comparison to adjudicate between these alternative network architectures, based on human electroencephalographic data acquired during an auditory location oddball paradigm. Our results support a hemispheric asymmetry in a frontoparietal network that conforms to the right-hemisphere dominance model.Weshow that, within this frontoparietal network, forward connectivity increases selectively in the hemisphere contralateral to the side of sensory stimulation. We interpret this finding in light of hierarchical predictive coding as a selective increase in attentional gain, which is mediated by feedforward connections that carry precision-weighted prediction errors during perceptual inference. This finding supports the disconnection hypothesis of unilateral neglect and has implications for theories of its etiology

Time-varying effective connectivity during visual object naming as a function of semantic demands

Accumulating evidence suggests that visual object understanding involves a rapid feedforward sweep, after which subsequent recurrent interactions are necessary. The extent to which recurrence plays a critical role in object processing remains to be determined. Recent studies have demonstrated that recurrent processing is modulated by increasing semantic demands. Differentially from previous studies, we used dynamic causal modeling to model neural activity recorded with magnetoencephalography while 14 healthy humans named two sets of visual objects that differed in the degree of semantic accessing demands, operationalized in terms of the values of basic psycholinguistic variables associated with the presented objects (age of acquisition, frequency, and familiarity). This approach allowed us to estimate the directionality of the causal interactions among brain regions and their associated connectivity strengths. Furthermore, to understand the dynamic nature of connectivity (i.e., the chronnectome; Calhoun et al., 2014) we explored the time-dependent changes of effective connectivity during a period (200–400 ms) where adding semantic-feature information improves modeling and classifying visual objects, at 50 ms increments. First, we observed a graded involvement of backward connections, that became active beyond 200 ms. Second, we found that semantic demands caused a suppressive effect in the backward connection from inferior frontal cortex (IFC) to occipitotemporal cortex over time. These results complement those from previous studies underscoring the role of IFC as a common source of top-down modulation, which drives recurrent interactions with more posterior regions during visual object recognition. Crucially, our study revealed the inhibitory modulation of this interaction in situations that place greater demands on the conceptual system

Timing in predictive coding: the roles of task relevance and global probability

Predictive coding models of attention propose that attention and prediction operate synergistically to optimize perception, as reflected in interactive effects on early sensory neural responses. It is yet unclear whether attention and prediction based on the temporal attributes of expected events operate in a similar fashion. We investigated how attention and prediction based on timing interact by manipulating the task relevance and a priori probability of auditory stimulus onset timing within a go/no-go task while recording EEG. Preparatory activity, as indexed via the contingent negative variation, reflected temporally specific anticipation as a function of both attention and prediction. Higher stimulus probability led to significant predictive N1 suppression; however, we failed to find an effect of task relevance on N1 amplitude and an interaction of task relevance with prediction. We suggest the predictability of sensory timing is the predominant influence on early sensory responses where a priori probabilities allow for strong prior beliefs. When this is the case, we find that the effects of temporal prediction on early sensory responses are independent of the task relevance of sensory stimuli. Our findings contribute to the expansion of predictive coding frameworks to include the role of timing in sensory processing

Assessing the influence of dopamine and mindfulness on the formation of routines in visual search

Given experience in cluttered but stable visual environments, our eye‐movements form stereotyped routines that sample task‐relevant locations, while not mixing‐up routines between similar task‐settings. Both dopamine signaling and mindfulness have been posited as factors that influence the formation of such routines, yet quantification of their impact remains to be tested in healthy humans. Over two sessions, participants searched through grids of doors to find hidden targets, using a gaze‐contingent display. Within each session, door scenes appeared in either one of two colors, with each color signaling a differing set of likely target locations. We derived measures for how well target locations were learned (target‐accuracy), how routine were sets of eye‐movements (stereotypy), and the extent of interference between the two scenes (setting‐accuracy). Participants completed two sessions, where they were administered either levodopa (dopamine precursor) or placebo (vitamin C), under double‐blind counterbalanced conditions. Dopamine and trait mindfulness (assessed by questionnaire) interacted to influence both target‐accuracy and stereotypy. Increasing dopamine improved accuracy and reduced stereotypy for high mindfulness scorers, but induced the opposite pattern for low mindfulness scorers. Dopamine also disrupted setting‐accuracy invariant to mindfulness. Our findings show that mindfulness modulates the impact of dopamine on the target‐accuracy and stereotypy of eye‐movement routines, whereas increasing dopamine promotes interference between task‐settings, regardless of mindfulness. These findings provide a link between non‐human and human models regarding the influence of dopamine on the formation of task‐relevant eye‐movement routines and provide novel insights into behavior‐trait factors that modulate the use of experience when building adaptive repertoires

Full-term pregnancy in breast cancer survivor with fertility preservation: A case report and review of literature

A 43-year-old woman with an associated history of gynecological pathology and breast cancer with only one cryopreserved embryo wished to be a mother. Several factors that influenced the success of the pregnancy in this case were analyzed. Favorable factors included: triple positive breast cancer [positive hormone receptors and positive human epidermal growth factor receptor 2], which is more hormosensitive and chemosensitive; absence of metastasis; correct endometrium preparation; and the patient's optimistic attitude and strict health habits. In contrast, the factors against success were: breast cancer; adjuvant breast cancer therapy gonadotoxicity; the age of the patient (> 40-year-old); endometriosis; ovarian cyst; hydrosalpinx; submucosal fibroids and the respective associated surgery done for the above-mentioned pathology (all resolved prior to the embryo transfer); and a low quantity of ovules (low ovarian reserve) after ovarian stimulation. This is a very special clinical case of a patient with theoretically low pregnancy success probability due to the consecutive accumulation of gynecological and oncological pathologies, who nonetheless became pregnant and delivered a full-term infant and was able to provide adequate breastfeeding

Bayesian mapping reveals that attention boosts neural responses to predicted and unpredicted stimuli

Predictive coding posits that the human brain continually monitors the environment for regularities and detects inconsistencies. It is unclear, however, what effect attention has on expectation processes, as there have been relatively few studies and the results of these have yielded contradictory findings. Here, we employed Bayesian model comparison to adjudicate between 2 alternative computational models. The “Opposition” model states that attention boosts neural responses equally to predicted and unpredicted stimuli, whereas the “Interaction” model assumes that attentional boosting of neural signals depends on the level of predictability. We designed a novel, audiospatial attention task that orthogonally manipulated attention and prediction by playing oddball sequences in either the attended or unattended ear. We observed sensory prediction error responses, with electroencephalography, across all attentional manipulations. Crucially, posterior probability maps revealed that, overall, the Opposition model better explained scalp and source data, suggesting that attention boosts responses to predicted and unpredicted stimuli equally. Furthermore, Dynamic Causal Modeling showed that these Opposition effects were expressed in plastic changes within the mismatch negativity network. Our findings provide empirical evidence for a computational model of the opposing interplay of attention and expectation in the brain

Activation of visible up-conversion luminescence in transparent and conducting ZnO:Er:Yb films by laser annealing

Transparent and conducting ZnO:Er:Yb thin films with visible up-conversion (660-nm emission under 980-nm excitation) were fabricated by RF magnetron sputtering. The as-deposited films were found to be transparent and conducting and the activation of the Er ions in these films to produce up-conversion luminescence was achieved by different post deposition annealing treatments in air, vacuum or by laser annealing using a Nd:YVO4 laser. The structural, electrical and optical properties and the up-conversion efficiency of these films were found to be strongly influenced by the annealing method, and a detailed study is reported in this paper. It has been demonstrated that, although the air annealing was the most efficient in terms of up-conversion, laser annealing was the only method capable of activating Er ions while preserving the electrical conductivity of the doped films. It has been shown that a minimum energy was needed in laser annealing to optically activate the rare earth ions in the ZnO host material to produce up-conversion. Up-converting and transparent conducting ZnO:Er:Yb films with an electrical resistivity of 5×10-2 Ω·cm and transparency ~80% in the visible wavelength range has been achieved by laser annealing

The un-predictive brain under threat: a neuro-computational account of anxious hypervigilance

Anxious hypervigilance is marked by sensitized sensory-perceptual processes and attentional biases to potential danger cues in the environment. How this is realized at the neurocomputational level is unknown but could clarify the brain mechanisms disrupted in psychiatric conditions such as posttraumatic stress disorder. Predictive coding, instantiated by dynamic causal models, provides a promising framework to ground these state-related changes in the dynamic interactions of reciprocally connected brain areas.Anxiety states were elicited in healthy participants (n\ua0= 19) by exposure to the threat of unpredictable, aversive shocks while undergoing magnetoencephalography. An auditory oddball sequence was presented to measure cortical responses related to deviance detection, and dynamic causal models quantified deviance-related changes in effective connectivity. Participants were also administered alprazolam (double-blinded, placebo-controlled crossover) to determine whether the cortical effects of threat-induced anxiety are reversed by acute anxiolytic treatment.Deviant tones elicited increased auditory cortical responses under threat. Bayesian analyses revealed that hypervigilant responding was best explained by increased postsynaptic gain in primary auditory cortex activity as well as modulation of feedforward, but not feedback, coupling within a temporofrontal cortical network. Increasing inhibitory gamma-aminobutyric acidergic action with alprazolam reduced anxiety and restored feedback modulation within the network.Threat-induced anxiety produced unbalanced feedforward signaling in response to deviations in predicable sensory input. Amplifying ascending sensory prediction error signals may optimize stimulus detection in the face of impending threats. At the same time, diminished descending sensory prediction signals impede perceptual learning and may, therefore, underpin some of the deleterious effects of anxiety on higher-order cognition