169 research outputs found
Neuroimaging of Aggressive and Violent Behaviour in Children and Adolescents
In recent years, a number of functional and structural neuroimaging studies have investigated the neural bases of aggressive and violent behaviour in children and adolescents. Most functional neuroimaging studies have persued the hypothesis that pathological aggression is a consequence of deficits in the neural circuits involved in emotion processing. There is converging evidence for abnormal neural responses to emotional stimuli in youths with a propensity towards aggressive behaviour. In addition, recent neuroimaging work has suggested that aggressive behaviour is also associated with abnormalities in neural processes that subserve both the inhibitory control of behaviour and the flexible adaptation of behaviour in accord with reinforcement information. Structural neuroimaging studies in children and adolescents with conduct problems are still scarce, but point to deficits in brain structures in volved in the processing of social information and in the regulation of social and goal-directed behaviour. The indisputable progress that this research field has made in recent years notwithstanding, the overall picture is still rather patchy and there are inconsistencies between studies that await clarification. Despite this, we attempt to provide an integrated view on the neural abnormalities that may contribute to various forms of juvenile aggression and violence, and discuss research strategies that may help to provide a more profound understanding of these important issues in the future
The Heterogeneity of Disruptive Behavior Disorders – Implications for Neurobiological Research and Treatment
Disruptive behavior disorders (DBDs) are reflected by a great variety of symptoms ranging from impulsive-hot-tempered quarrels to purposeful and goal-directed acts of cruelty. A growing body of data indicates that there are neurobiological factors that increase the risk for developing DBDs. In this review, we give a broad overview of recent studies investigating physiological, neural, genetic factors, and specific neurotransmitter systems. We also discuss the impact of psychosocial risk and consider the effects of gene-environment interactions. Due to the heterogeneity of DBDs, it is concluded that specific subtypes of disruptive behavior should be considered both in terms their biological basis and in regard to specific treatment needs
Own-race and own-age biases facilitate visual awareness of faces under interocular suppression
The detection of a face in a visual scene is the first stage in the face
processing hierarchy. Although all subsequent, more elaborate face processing
depends on the initial detection of a face, surprisingly little is known about
the perceptual mechanisms underlying face detection. Recent evidence suggests
that relatively hard-wired face detection mechanisms are broadly tuned to all
face-like visual patterns as long as they respect the typical spatial
configuration of the eyes above the mouth. Here, we qualify this notion by
showing that face detection mechanisms are also sensitive to face shape and
facial surface reflectance properties. We used continuous flash suppression
(CFS) to render faces invisible at the beginning of a trial and measured the
time upright and inverted faces needed to break into awareness. Young
Caucasian adult observers were presented with faces from their own race or
from another race (race experiment) and with faces from their own age group or
from another age group (age experiment). Faces matching the observers’ own
race and age group were detected more quickly. Moreover, the advantage of
upright over inverted faces in overcoming CFS, i.e., the face inversion effect
(FIE), was larger for own-race and own-age faces. These results demonstrate
that differences in face shape and surface reflectance influence access to
awareness and configural face processing at the initial detection stage.
Although we did not collect data from observers of another race or age group,
these findings are a first indication that face detection mechanisms are
shaped by visual experience with faces from one’s own social group. Such
experience-based fine-tuning of face detection mechanisms may equip in-group
faces with a competitive advantage for access to conscious awareness
reward and punishment alter conscious visual perception during binocular rivalry
Perception is an inferential process, which becomes immediately evident when
sensory information is conflicting or ambiguous and thus allows for more than
one perceptual interpretation. Thinking the idea of perception as inference
through to the end results in a blurring of boundaries between perception and
action selection, as perceptual inference implies the construction of a
percept as an active process. Here we therefore wondered whether perception
shares a key characteristic of action selection, namely that it is shaped by
reinforcement learning. In two behavioral experiments, we used binocular
rivalry to examine whether perceptual inference can be influenced by the
association of perceptual outcomes with reward or punishment, respectively, in
analogy to instrumental conditioning. Binocular rivalry was evoked by two
orthogonal grating stimuli presented to the two eyes, resulting in perceptual
alternations between the two gratings. Perception was tracked indirectly and
objectively through a target detection task, which allowed us to preclude
potential reporting biases. Monetary reward or punishments were given
repeatedly during perception of only one of the two rivaling stimuli. We found
an increase in dominance durations for the percept associated with reward,
relative to the non-rewarded percept. In contrast, punishment led to an
increase of the non-punished compared to a relative decrease of the punished
percept. Our results show that perception shares key characteristics with
action selection, in that it is influenced by reward and punishment in
opposite directions, thus narrowing the gap between the conceptually separated
domains of perception and action selection. We conclude that perceptual
inference is an adaptive process that is shaped by its consequences
Priming in a shape task but not in a category task under continuous flash suppression
Continuous flash suppression (CFS) is an interocular suppression technique
that uses high-contrast masks flashed to one eye to prevent conscious
perception of images shown to the other eye. It has become widely used due to
its strength and prolonged duration of suppression and its nearly
deterministic control of suppression onset and offset. Recently, it has been
proposed that action-relevant visual processing ascribed to the dorsal stream
remains functional, while processing in the ventral stream is completely
suppressed, when stimuli are invisible under CFS. Here we tested the
hypothesis that the potentially dorsal-stream-based analysis of prime-stimulus
elongation during CFS affects the categorization of manipulable target
objects. In two behavioral experiments, we found evidence for priming in a
shape task, but none for priming in a category task, when prime stimuli were
rendered invisible using CFS. Our results thus support the notion that the
representation of CF-suppressed stimuli is more limited than previously
thought
Mesolimbic confidence signals guide perceptual learning in the absence of external feedback
It is well established that learning can occur without external feedback, yet
normative reinforcement learning theories have difficulties explaining such
instances of learning. Here, we propose that human observers are capable of
generating their own feedback signals by monitoring internal decision
variables. We investigated this hypothesis in a visual perceptual learning
task using fMRI and confidence reports as a measure for this monitoring
process. Employing a novel computational model in which learning is guided by
confidence-based reinforcement signals, we found that mesolimbic brain areas
encoded both anticipation and prediction error of confidence—in remarkable
similarity to previous findings for external reward-based feedback. We
demonstrate that the model accounts for choice and confidence reports and show
that the mesolimbic confidence prediction error modulation derived through the
model predicts individual learning success. These results provide a
mechanistic neurobiological explanation for learning without external feedback
by augmenting reinforcement models with confidence-based feedback
Priming of object detection under continuous flash suppression depends on attention but not on part-whole configuration
Previous research has shown that the identification of visual objects can rely on both view-dependent, holistic as well as view-independent, analytic representation, depending on visual attention. Here, we asked whether
the initial conscious detection of objects reveals similar dependencies and may therefore share similar perceptual mechanisms. We used continuous flash suppression to render objects presented in familiar views invisible at the beginning of a trial and recorded the time these target objects needed to break into awareness. Target objects were preceded by spatially attended or unattended primes that were either shown in the same familiar view as the targets or horizontally split (i.e., with their halves swapping positions) in order
to disrupt holistic processing. Relative to an unprimed baseline, suppression times were shorter for all priming conditions. Although spatial attention enhanced this priming effect on access to awareness, even unattended
primes facilitated awareness of a related target, indicating that object detection does not fully concur with the idea of attention-demanding analytic object representations. Moreover, priming effects were of similar strength for primes shown in the same familiar view as the targets and for horizontally split primes, indicating that holistic (template-like) representations do
not play an integral role in object detection. These results suggest that the initial detection of an object relies on representations of object features rather than holistic representations used for recognition. The perceptual mechanisms mediating conscious object detection are therefore markedly different from those underlying object identification
An Integration of Predictive Coding and Phenomenological Approaches
Current theories in the framework of hierarchical predictive coding propose
that positive symptoms of schizophrenia, such as delusions and hallucinations,
arise from an alteration in Bayesian inference, the term inference referring
to a process by which learned predictions are used to infer probable causes of
sensory data. However, for one particularly striking and frequent symptom of
schizophrenia, thought insertion, no plausible account has been proposed in
terms of the predictive-coding framework. Here we propose that thought
insertion is due to an altered experience of thoughts as coming from
“nowhere”, as is already indicated by the early 20th century phenomenological
accounts by the early Heidelberg School of psychiatry. These accounts
identified thought insertion as one of the self-disturbances (from German:
“Ichstörungen”) of schizophrenia and used mescaline as a model-psychosis in
healthy individuals to explore the possible mechanisms. The early Heidelberg
School (Gruhle, Mayer-Gross, Beringer) first named and defined the self-
disturbances, and proposed that thought insertion involves a disruption of the
inner connectedness of thoughts and experiences, and a “becoming sensory” of
those thoughts experienced as inserted. This account offers a novel way to
integrate the phenomenology of thought insertion with the predictive coding
framework. We argue that the altered experience of thoughts may be caused by a
reduced precision of context-dependent predictions, relative to sensory
precision. According to the principles of Bayesian inference, this reduced
precision leads to increased prediction-error signals evoked by the neural
activity that encodes thoughts. Thus, in analogy with the prediction-error
related aberrant salience of external events that has been proposed
previously, “internal” events such as thoughts (including volitions, emotions
and memories) can also be associated with increased prediction-error signaling
and are thus imbued with aberrant salience. We suggest that the individual’s
attempt to explain the aberrant salience of thoughts results in their
interpretation as being inserted by an alien agent, similarly to the emergence
of delusions in response to the aberrant salience of sensory stimuli
Access to awareness of direct gaze is related to autistic traits
Background: The atypical processing of eye contact is a characteristic hallmark of autism spectrum disorder (ASD). The severity of these symptoms, however, is thought to lie on a continuum that extends into the typical population. While behavioural evidence shows that differences in social cognitive tasks in typically developed (TD) adults are related to the levels of autistic-like traits, it remains unknown whether such a relation exists for the sensitivity to direct gaze.; Methods: In two experiments, we measured reaction times to detect the faces with direct and averted gaze, suppressed from awareness, i.e. the access to awareness. In experiment 1, we tested N = 19 clinically diagnosed adults with ASD and N = 22 TD matched controls, while in experiment 2, we tested an independent sample of N = 20 TD adults.; Results: In line with the literature, experiment 1 showed preferential processing of direct gaze in the TD group but not in the ASD group. Importantly, we found a linear relationship in both experiments between the levels of autistic traits within the groups of TD participants and their sensitivity to direct gaze: with increasing autistic characteristics, there was a decrease in sensitivity to direct gaze.; Conclusion: These results provide the first evidence that differences in gaze processing and the sensitivity to direct gaze are already present in individuals with subclinical levels of autistic traits. Furthermore, they lend support to the continuum view of the disorder and could potentially help in an earlier diagnosis of individuals at high risk for autism.Peer Reviewe
A predictive coding account of bistable perception - a model-based fMRI study
In bistable vision, subjective perception wavers between two interpretations
of a constant ambiguous stimulus. This dissociation between conscious
perception and sensory stimulation has motivated various empirical studies on
the neural correlates of bistable perception, but the neurocomputational
mechanism behind endogenous perceptual transitions has remained elusive. Here,
we recurred to a generic Bayesian framework of predictive coding and devised a
model that casts endogenous perceptual transitions as a consequence of
prediction errors emerging from residual evidence for the suppressed percept.
Data simulations revealed close similarities between the model’s predictions
and key temporal characteristics of perceptual bistability, indicating that
the model was able to reproduce bistable perception. Fitting the predictive
coding model to behavioural data from an fMRI-experiment on bistable
perception, we found a correlation across participants between the model
parameter encoding perceptual stabilization and the behaviourally measured
frequency of perceptual transitions, corroborating that the model successfully
accounted for participants’ perception. Formal model comparison with
established models of bistable perception based on mutual inhibition and
adaptation, noise or a combination of adaptation and noise was used for the
validation of the predictive coding model against the established models. Most
importantly, model-based analyses of the fMRI data revealed that prediction
error time-courses derived from the predictive coding model correlated with
neural signal time-courses in bilateral inferior frontal gyri and anterior
insulae. Voxel-wise model selection indicated a superiority of the predictive
coding model over conventional analysis approaches in explaining neural
activity in these frontal areas, suggesting that frontal cortex encodes
prediction errors that mediate endogenous perceptual transitions in bistable
perception. Taken together, our current work provides a theoretical framework
that allows for the analysis of behavioural and neural data using a predictive
coding perspective on bistable perception. In this, our approach posits a
crucial role of prediction error signalling for the resolution of perceptual
ambiguities
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