Marta I Garrido

Marta I Garrido
The University of Queensland | UQ · Queensland Brain Institute

PhD

About

117
Publications
14,477
Reads
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5,053
Citations
Citations since 2016
70 Research Items
3336 Citations
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
Additional affiliations
January 2013 - present
The University of Queensland
Position
  • The University of Queensland
September 2009 - December 2012
University College London
January 2008 - August 2009
Education
September 2004 - July 2008
University College London
Field of study
  • Imaging Neuroscience
September 1998 - September 2003
Technical University of Lisbon
Field of study
  • Physics Engineering

Publications

Publications (117)
Preprint
Full-text available
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 o...
Article
Full-text available
The folk psychological notion that “we see what we expect to see” is supported by evidence that we become consciously aware of visual stimuli that match our prior expectations more quickly than stimuli that violate our expectations. Similarly, “we see what we want to see,” such that more biologically-relevant stimuli are also prioritised for consci...
Article
Full-text available
Rapidly detecting salient information in our environments is critical for survival. Visual processing in subcortical areas like the pulvinar and amygdala has been shown to facilitate unconscious processing of salient stimuli. It is unknown, however, if and how these areas might interact with cortical regions to facilitate faster conscious perceptio...
Article
Full-text available
Reduced inhibitory control and a hypersensitivity to reward are key deficits in drug dependents; however, they tend to be studied in isolation. Here, we seek to understand the neural processes underlying control over reward and how this is different in people with a tobacco use disorder (pTUD). A novel variant of the monetary incentive delay task w...
Article
Full-text available
A general consensus persists that sensory-perceptual differences in autism, such as hypersensitivities to light or sound, result from an overreliance on new (rather than prior) sensory observations. However, conflicting Bayesian accounts of autism remain unresolved as to whether such alterations are caused by more precise sensory observations (prec...
Preprint
Full-text available
Bayesian models of autism suggest that disruptions in context-sensitive prediction error weighting may underpin sensory perceptual alterations, such as hypersensitivities. We used an auditory oddball paradigm with pure tones arising from high or low uncertainity contexts to determine whether autistic individuals display differences in context adjus...
Article
Previous studies applying machine learning methods to psychosis have primarily been concerned with the binary classification of chronic schizophrenia patients and healthy controls. The aim of this study was to use electroencephalographic (EEG) data and pattern recognition to predict subclinical psychotic-like experiences on a continuum between thes...
Preprint
Full-text available
A general consensus persists that sensory-perceptual differences in autism, such as hypersensitivities to light or sound, result from an overreliance on new (rather than prior) sensory observations. However, conflicting Bayesian accounts of autism remain unresolved as to whether such alterations are caused by more precise sensory observations (prec...
Preprint
Full-text available
Rapidly detecting salient information in our environments is critical for survival. Visual processing in subcortical areas like the pulvinar and amygdala have been shown to facilitate unconscious processing of salient stimuli. It is unknown, however, if and how these areas might interact with cortical networks to facilitate faster conscious percept...
Article
Recent theories in computational psychiatry propose that unusual perceptual experiences and delusional beliefs may emerge as a consequence of aberrant inference and disruptions in sensory learning. The current study investigates these theories and examines the alterations that are specific to schizophrenia spectrum disorders vs those that occur as...
Article
Full-text available
Detecting changes in the environment is fundamental for our survival. According to predictive coding theory, detecting these irregularities relies both on incoming sensory information and our top-down prior expectations (or internal generative models) about the world. Prediction errors (PEs), detectable in event-related potentials (ERPs), occur whe...
Article
Full-text available
Background: Compensation and adaptation therapies have been developed to improve community functioning via improving neurocognitive abilities in people with schizophrenia. Various modes of delivering compensation and adaptation therapies have been found to be effective. The aim of this trial is to compare two different cognitive interventions, Com...
Article
Full-text available
The diagnostic criteria for schizophrenia comprise a diverse range of heterogeneous symptoms. As a result, individuals each present a distinct set of symptoms despite having the same overall diagnosis. Whilst previous machine learning studies have primarily focused on dichotomous patient‐control classification, we predict the severity of each indiv...
Article
Our perceptions result from the brain’s ability to make inferences, or predictive models, of sensory information. Recently, it has been proposed that psychotic traits may be linked to impaired predictive processes. Here, we examine the brain dynamics underlying statistical learning and inference in stable and volatile environments, in a population...
Article
Full-text available
A lesion to the right hemisphere of the brain in humans commonly leads to perceptual neglect of the left side of the sensorium. The clinical observation that lesions to disparate cortical and subcortical areas converge upon similar behavioural symptoms points to neglect as a dysconnection syndrome that may result from the disruption of a distribute...
Article
Full-text available
Electro- and magneto-encephalography are functional neuroimaging modalities characterised by their ability to quantify dynamic spatiotemporal activity within the brain. However, the visualisation techniques used to illustrate these effects are currently limited to single- or multi-channel time series plots, topographic scalp maps and orthographic c...
Article
Background The ability to generate a precise internal model of statistical regularities is impaired in schizophrenia. Predictive coding accounts of schizophrenia suggest that psychotic symptoms may be explained by a failure to build precise beliefs or a model of the world. The precision of this model may vary with context. For example, in a noisy e...
Article
The very earliest stages of sensory processing have the potential to alter how we perceive and respond to our environment. These initial processing circuits can incorporate subcortical regions, such as the thalamus and brainstem nuclei, which mediate complex interactions with the brain’s cortical processing hierarchy. These subcortical pathways, ma...
Article
Full-text available
Recent studies have shown that prediction and attention can interact under various circumstances, suggesting that the two processes are based on interdependent neural mechanisms. In the visual modality, attention can be deployed to the location of a task-relevant stimulus (‘spatial attention’) or to a specific feature of the stimulus, such as colou...
Preprint
Background: The diagnostic criteria for schizophrenia comprise a diverse range of heterogeneous symptoms. As a result, individuals each present a distinct set of symptoms despite having the same overall diagnosis. Methods: Although machine learning techniques are considered a potential gateway to precision psychiatry, prior work has primarily focus...
Preprint
Full-text available
Our perceptions result from the brain’s ability to make inferences, or predictive models, of sensory information. Recently, it has been proposed that psychotic traits may be linked to impaired predictive processes. Here, we examine the brain dynamics underlying sensory learning and inference in stable and volatile environments, in a population of h...
Article
Full-text available
Our sensory systems actively predict sensory information based on previously learnt patterns, which are continuously updated with information from the actual sensory input via prediction errors. Individuals with schizophrenia consistently show reduced auditory prediction errors as well as altered fractional anisotropy (indicative of white matter ch...
Preprint
Full-text available
Detecting changes in the environment is fundamental for survival, as these may indicate potential rewards or threats. According to predictive coding theory, detecting these irregularities relies on both incoming sensory information and our prior beliefs; with incongruity between the two manifesting as a prediction error (PE) response. Many changes...
Preprint
Full-text available
Background The ability to generate a precise internal model of statistical regularities is impaired in schizophrenia. Predictive coding accounts of schizophrenia suggest that psychotic symptoms may be explained by a failure to build precise beliefs or a model of the world. The precision of this model may vary with context. For example, in a noisy e...
Preprint
Full-text available
Recent studies have shown that prediction and attention can interact under various circumstances, suggesting that the two processes are based on interdependent neural mechanisms. In the visual modality, attention can be deployed to the location of a task-relevant stimulus (‘spatial attention’) or to a specific feature of the stimulus, such as colou...
Article
Auditory prediction errors, i.e. the mismatch between predicted, forthcoming auditory sensations and actual sensory input, trigger the detection of surprising auditory events in the environment. Auditory mismatches engage a hierarchical functional network of cortical sources, which are also interconnected by auditory white matter pathways. Hence it...
Article
Full-text available
[This corrects the article DOI: 10.1371/journal.pbio.2006812.].
Article
Background Recent theories in computational psychiatry have proposed that unusual perceptual experiences and delusional beliefs in psychotic disorders may emerge as a consequence of aberrant inference and disruptions in prediction error updating. The current study investigates anomalies in belief formation and updating that are specific to the schi...
Preprint
Humans show striking limitations in information processing when multitasking, yet can modify these limits with practice. Such limitations have been linked to a frontal-parietal network, but recent models of decision-making implicate a striatal-cortical network. We adjudicated these accounts by investigating the circuitry underpinning multitasking i...
Article
Full-text available
The encoding of sensory information in the human brain is thought to be optimised by two principal processes: ‘prediction’ uses stored information to guide the interpretation of forthcoming sensory events, and ‘attention’ prioritizes these events according to their behavioural relevance. Despite the ubiquitous contributions of attention and predict...
Data
Independent main effects of attention and prediction on orientation response profiles, showing standards, deviants, and controls. (A) Main effect of attention on orientation response profiles. The amplitude of attended gratings was larger than that of ignored gratings (219–550 ms, cluster-corrected p = 0.001). Shading denotes standard error of the...
Data
ERPs and MMRs. (A) ERPs at selected electrodes, shown separately for each condition. Bars underneath each plot indicate time points at which there was a significant main effect of attention (solid grey bar), significant main effect of prediction (solid black bar), or a significant interaction between attention and prediction (dotted black bar) at t...
Data
RSS for exponentiated cosine functions fitted to generalised mismatch response profiles (Fig 5). Note the high RSS values along the x-axis beginning at 200 ms, indicating that the apparent generalisation of spatial maps trained at stimulus onset to later times in the epoch (Fig 5, red patch along the x-axis) was likely due to noise. RSS, residual s...
Preprint
Full-text available
Our sensory systems actively predict sensory information based on previously learnt patterns. An inability to accurately predict forthcoming information results in prediction errors. Individuals with schizophrenia consistently show reduced auditory prediction errors as well as reduced microstructure in auditory white matter pathways. However, it is...
Article
COVER ILLUSTRATION Reconstruction of whole‐brain white matter from diffusion magnetic resonance imaging (MRI) data in preparation for structural connectome analyses. Colours indicate direction of the white matter tracts and the scull is reconstructed from T1‐images. (See article by Oestreich et al., pages 529–537, this issue.)
Article
Full-text available
One of the most common copy number variants, the 22q11.2 microdeletion, confers an increased risk for schizophrenia. Since schizophrenia has been associated with an aberrant neural response to repeated stimuli through both reduced adaptation and prediction, we here hypothesized that this may also be the case in nonpsychotic individuals with a 22q11...
Preprint
Electro-and magneto-encephalography are functional neuroimaging modalities characterised by their ability to quantify dynamic spatiotemporal activity within the brain. However, the visualisation techniques currently used to illustrate these effects are currently limited to single-or multi-channel time series plots, topographic scalp maps and orthog...
Preprint
Electro- and magneto-encephalography are functional neuroimaging modalities characterised by their ability to quantify dynamic spatiotemporal activity within the brain. However, the visualisation techniques currently used to illustrate these effects are currently limited to single- or multi-channel time series plots, topographic scalp maps and orth...
Preprint
Full-text available
Our survival depends on how well we can rapidly detect threats in our environment. To facilitate this, the brain is faster to bring threatening or rewarding visual stimuli into conscious awareness than neutral stimuli. Unexpected events may indicate a potential threat, and yet we tend to respond slower to unexpected than expected stimuli. It is unc...
Preprint
Full-text available
The human brain is thought to optimise the encoding of incoming sensory information through two principal mechanisms: prediction uses stored information to guide the interpretation of forthcoming sensory events, and attention prioritizes these events according to their behavioural relevance. Despite the ubiquitous contributions of attention and pre...
Article
Full-text available
Our ability to rapidly detect threats is thought to be subserved by a subcortical pathway that quickly conveys visual information to the amygdala. This neural shortcut has been demonstrated in animals but has rarely been shown in the human brain. Importantly, it remains unclear whether such a pathway might influence neural activity and behavior. We...
Article
Full-text available
Neural processing of sensory input in the brain takes time, and for that reason our awareness of visual events lags behind their actual occurrence. One way the brain might compensate to minimize the impact of the resulting delays is through extrapolation. Extrapolation mechanisms have been argued to underlie perceptual illusions in which moving and...
Preprint
Full-text available
Our ability to rapidly detect threats is thought to be subserved by a subcortical pathway that quickly conveys visual information to the amygdala. This neural shortcut has been demonstrated in animals but has rarely been shown in the human brain. Importantly, it remains unclear whether such a pathway might influence neural activity and behaviour. W...
Preprint
Full-text available
Background One of the most common copy number variants, the 22q11.2 microdeletion, confers an increased risk for schizophrenia. Since schizophrenia has been associated with an aberrant neural response to repeated stimuli through both reduced adaptation and prediction, we here hypothesized that this may also be the case in nonpsychotic individuals w...
Article
Full-text available
Predictive coding postulates that we make (top-down) predictions about the world and that we continuously compare incoming (bottom-up) sensory information with these predictions, in order to update our models and perception so as to better reflect reality. That is, our so-called “Bayesian brains” continuously create and update generative models of...
Article
Widespread white matter connectivity disruptions have commonly been reported in schizophrenia. However, it is questionable whether structural connectivity decline is specifically associated with schizophrenia or whether it extends along a continuum of psychosis into the healthy population. Elucidating brain structure changes associated with psychot...
Article
Full-text available
The 22q11.2 deletion is one of the most common copy number variants in humans. Carriers of the deletion have a markedly increased risk for neurodevelopmental brain disorders, including schizophrenia, autism spectrum disorders, and attention deficit hyperactivity disorder. The high risk of psychiatric disorders associated with 22q11.2 deletion syndr...
Preprint
Neuroimaging methods, including magnetoencephalography and electroencephalo- graphy (MEEG), allow non-invasive collection of neural data in healthy people and in individuals with neurological or psychiatric disorders, with the aim of advancing the understanding of brain function in health and disease. Currently, scientific practice is undergoing a...
Preprint
Previous studies of psychosis using machine learning methods have primarily been concerned with binary classification of patients and healthy controls. The aim of this study was to use electroencephalographic (EEG) data and pattern recognition to predict individual psychotic experiences on a continuum between these two extremes in otherwise healthy...
Preprint
Background Widespread white matter disruptions in schizophrenia have been commonly reported, but it remains unanswered whether these abnormalities are associated with schizophrenia specifically or whether they range along a psychotic continuum into the healthy population. Investigating the extent of white matter connectivity disruptions specific to...
Preprint
Auditory prediction errors, i.e. the mismatch between predicted and actual auditory input, are generated by a hierarchical functional network of cortical sources. This network is also interconnected by auditory white matter pathways. Hence it would be reasonable to assume that these structural and functional networks are quantitatively related, whi...
Preprint
Predictive coding postulates that we make (top-down) predictions about the world and that we continuously compare incoming (bottom-up) sensory information with these predictions, in order to update our models and perception so as to better reflect reality. That is, our so-called 'Bayesian brains' continuously create and update generative models of...
Article
Full-text available
Predictive coding postulates that the brain continually predicts forthcoming sensory events based on past experiences in order to process sensory information and respond to unexpected events in a fast and efficient manner. Predictive coding models in the context of overt speech are believed to operate along auditory white matter pathways such as th...
Article
22q11.2 deletion syndrome (22q11.2DS) is one of the most common copy number variants and confers a markedly increased risk for schizophrenia. As such, 22q11.2DS is a homogeneous genetic liability model which enables studies to delineate functional abnormalities that may precede disease onset. Mismatch negativity (MMN), a brain marker of change dete...
Preprint
Full-text available
A lesion to the right hemisphere of the brain often leads to perceptual neglect of the left side of the sensorium. The fact that lesions to different cortical regions lead to the same symptoms points to neglect as a dysconnection syndrome that may result from the dysconnection of a distributed network, rather than a disruption of computation in any...
Article
Background 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 neuro-computational level is unknown, but could clarify the brain mechanisms disrupted in psychiatric conditions such as PTSD. Predictive coding, instantiated by dynam...
Preprint
Full-text available
Sensory attenuation refers to the cortical suppression of self-generated sensations relative to externally-generated sensations. This attenuation of cortical responsiveness is the result of internal forward models which make precise predictions about forthcoming sensations. Forward models of sensory attenuation in the auditory domain are thought to...
Article
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 at...
Article
Full-text available
Schizophrenia is a complex psychiatric disorder, typically diagnosed through symptomatic evidence collected through patient interview. We aim to develop an objective biologically-based computational tool which aids diagnosis and relies on accessible imaging technologies such as electroencephalography (EEG). To achieve this, we used machine learning...
Article
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 comparis...
Article
Sensory prediction errors are fundamental brain responses that signal a violation of expectation in either the internal or external sensory environment, and are therefore crucial for survival and adaptive behaviour. Patients with schizophrenia show deficits in these internal and external sensory prediction errors, which can be measured using electr...
Article
There is significant controversy over the existence and function of a direct subcortical visual pathway to the amygdala. It is thought that this pathway rapidly transmits low spatial frequency information to the amygdala independently of the cortex and yet the directionality of this function has never been determined. We used magnetoencephalography...
Preprint
Schizophrenia is a complex psychiatric disorder, typically diagnosed through symptomatic evidence collected through patient interview. We aim to develop an objective biologically-based computational tool which aids diagnosis and relies on accessible imaging technologies such as electroencephalography (EEG). To achieve this, we used machine learning...
Preprint
Full-text available
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 comparis...
Preprint
Full-text available
There is significant controversy over the anatomical existence and potential function of a direct subcortical visual pathway to the amygdala. It is thought that this pathway rapidly transmits low spatial frequency information to the amygdala independently of the cortex and yet this function has never been causally determined. In this study, neural...
Poster
Full-text available
Introduction: Theoretical accounts of human brain development assume an increasing influence of the frontal lobes on posterior brain regions during childhood (e.g., Stevens, 2009). However, the practical challenges of conducting functional imaging studies with young children mean that there is little direct evidence to support such postulations. In...
Article
Full-text available
The ability to learn about regularities in the environment and to make predictions about future events is fundamental for adaptive behaviour. We have previously shown that people can implicitly encode statistical regularities and detect violations therein, as reflected in neuronal responses to unpredictable events that carry a unique prediction err...
Article
Objective: We investigated the neurophysiological mechanisms underpinning the generation of the mismatch negativity (MMN) and its development from adolescence to early adulthood. Methods: We used dynamic causal modelling (DCM) to study connectivity models for healthy adults and adolescents. MMN was elicited with an auditory oddball paradigm in two...
Article
Full-text available
This technical note addresses some key reproducibility issues in the dynamic causal modelling of group studies of event related potentials. Specifically, we address the reproducibility of Bayesian model comparison (and inferences about model parameters) from three important perspectives namely: (i) reproducibility with independent data (obtained by...