scholarly journals Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

2015 ◽  
Vol 112 (43) ◽  
pp. 13401-13406 ◽  
Author(s):  
Christoph Teufel ◽  
Naresh Subramaniam ◽  
Veronika Dobler ◽  
Jesus Perez ◽  
Johanna Finnemann ◽  
...  
Keyword(s):  
Information Processing ◽  
Prior Knowledge ◽  
Early Psychosis ◽  
Psychotic Symptoms ◽  
Psychotic Experiences ◽  
Healthy Individuals ◽  
Top Down ◽  
Bottom Up ◽  
Psychosis Proneness ◽  
Sensory Evidence

Many neuropsychiatric illnesses are associated with psychosis, i.e., hallucinations (perceptions in the absence of causative stimuli) and delusions (irrational, often bizarre beliefs). Current models of brain function view perception as a combination of two distinct sources of information: bottom-up sensory input and top-down influences from prior knowledge. This framework may explain hallucinations and delusions. Here, we characterized the balance between visual bottom-up and top-down processing in people with early psychosis (study 1) and in psychosis-prone, healthy individuals (study 2) to elucidate the mechanisms that might contribute to the emergence of psychotic experiences. Through a specialized mental-health service, we identified unmedicated individuals who experience early psychotic symptoms but fall below the threshold for a categorical diagnosis. We observed that, in early psychosis, there was a shift in information processing favoring prior knowledge over incoming sensory evidence. In the complementary study, we capitalized on subtle variations in perception and belief in the general population that exhibit graded similarity with psychotic experiences (schizotypy). We observed that the degree of psychosis proneness in healthy individuals, and, specifically, the presence of subtle perceptual alterations, is also associated with stronger reliance on prior knowledge. Although, in the current experimental studies, this shift conferred a performance benefit, under most natural viewing situations, it may provoke anomalous perceptual experiences. Overall, we show that early psychosis and psychosis proneness both entail a basic shift in visual information processing, favoring prior knowledge over incoming sensory evidence. The studies provide complementary insights to a mechanism by which psychotic symptoms may emerge.

scholarly journals Circular inference in bistable perception

2019 ◽  
Author(s):  
Pantelis Leptourgos ◽  
Charles-Edouard Notredame ◽  
Marion Eck ◽  
Renaud Jardri ◽  
Sophie Denève
Keyword(s):  
Prior Knowledge ◽  
Bayesian Approach ◽  
Necker Cube ◽  
Top Down ◽  
Inference Model ◽  
Bottom Up ◽  
Bistable Perception ◽  
Sensory Evidence ◽  
The Brain ◽  
Healthy Participants

AbstractWhen facing fully ambiguous images, the brain cannot commit to a single percept and instead switches between mutually exclusive interpretations every few seconds, a phenomenon known as bistable perception. Despite years of research, there is still no consensus on whether bistability, and perception in general, is driven primarily by bottom-up or top-down mechanisms. Here, we adopted a Bayesian approach in an effort to reconcile these two theories. Fifty-five healthy participants were exposed to an adaptation of the Necker cube paradigm, in which we manipulated sensory evidence (by shadowing the cube) and prior knowledge (e.g., by varying instructions about what participants should expect to see). We found that manipulations of both sensory evidence and priors significantly affected the way participants perceived the Necker cube. However, we observed an interaction between the effect of the cue and the effect of the instructions, a finding incompatible with Bayes-optimal integration. In contrast, the data were well predicted by a circular inference model. In this model, ambiguous sensory evidence is systematically biased in the direction of current expectations, ultimately resulting in a bistable percept.

scholarly journals Signature patterns for top-down and bottom-up information processing via cross-frequency coupling in macaque auditory cortex

2018 ◽  
Author(s):  
Christian D. Márton ◽  
Makoto Fukushima ◽  
Corrie R. Camalier ◽  
Simon R. Schultz ◽  
Bruno B. Averbeck
Keyword(s):  
Information Processing ◽  
Auditory Cortex ◽  
Predictive Coding ◽  
Low Frequency ◽  
Information Need ◽  
Top Down ◽  
Bottom Up ◽  
Low Frequencies ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

AbstractPredictive coding is a theoretical framework that provides a functional interpretation of top-down and bottom up interactions in sensory processing. The theory has suggested that specific frequency bands relay bottom-up and top-down information (e.g. “γ up, β down”). But it remains unclear whether this notion generalizes to cross-frequency interactions. Furthermore, most of the evidence so far comes from visual pathways. Here we examined cross-frequency coupling across four sectors of the auditory hierarchy in the macaque. We computed two measures of cross-frequency coupling, phase-amplitude coupling (PAC) and amplitude-amplitude coupling (AAC). Our findings revealed distinct patterns for bottom-up and top-down information processing among cross-frequency interactions. Both top-down and bottom-up made prominent use of low frequencies: low-to-low frequency (θ, α, β) and low frequency-to-high γ couplings were predominant top-down, while low frequency-to-low γ couplings were predominant bottom-up. These patterns were largely preserved across coupling types (PAC and AAC) and across stimulus types (natural and synthetic auditory stimuli), suggesting they are a general feature of information processing in auditory cortex. Moreover, our findings showed that low-frequency PAC alternated between predominantly top-down or bottom-up over time. Altogether, this suggests sensory information need not be propagated along separate frequencies upwards and downwards. Rather, information can be unmixed by having low frequencies couple to distinct frequency ranges in the target region, and by alternating top-down and bottom-up processing over time.1SignificanceThe brain consists of highly interconnected cortical areas, yet the patterns in directional cortical communication are not fully understood, in particular with regards to interactions between different signal components across frequencies. We employed a a unified, computationally advantageous Granger-causal framework to examine bi-directional cross-frequency interactions across four sectors of the auditory cortical hierarchy in macaques. Our findings extend the view of cross-frequency interactions in auditory cortex, suggesting they also play a prominent role in top-down processing. Our findings also suggest information need not be propagated along separate channels up and down the cortical hierarchy, with important implications for theories of information processing in the brain such as predictive coding.

Computational Models of Learning Mechanisms in Psychosis

2017 ◽  
Author(s):  
Andreas Heinz
Keyword(s):  
Mental Disorders ◽  
Psychiatric Disorders ◽  
Computational Models ◽  
The Self ◽  
Psychotic Experiences ◽  
Learning Mechanisms ◽  
Top Down ◽  
Bottom Up ◽  
Surrounding World

Psychotic experiences may best be described as an alteration in the self-ascription of thoughts and actions, which is associated with a profoundly altered experience of oneself and the surrounding world. Computational models of key symptoms of psychiatric disorders are discussed with respect to the attribution of salience and self-relatedness to otherwise irrelevant stimuli and the role of top-down modelling in the generation of delusions. Top-down and bottom-up approaches in understanding mental disorders and their computational models are compared and critically reflected.

scholarly journals Preserved capacity for learning statistical regularities and directing selective attention after hippocampal lesions

2019 ◽  
Vol 116 (39) ◽  
pp. 19705-19710 ◽  
Author(s):  
Nuttida Rungratsameetaweemana ◽  
Larry R. Squire ◽  
John T. Serences
Keyword(s):  
Information Processing ◽  
Prior Knowledge ◽  
Human Perception ◽  
Motion Direction ◽  
Hippocampal Lesions ◽  
Perceptual Performance ◽  
Statistical Regularities ◽  
Probabilistic Structure ◽  
Sensory Evidence ◽  
Task Conditions

Prior knowledge about the probabilistic structure of visual environments is necessary to resolve ambiguous information about objects in the world. Expectations based on stimulus regularities exert a powerful influence on human perception and decision making by improving the efficiency of information processing. Another type of prior knowledge, termed top-down attention, can also improve perceptual performance by facilitating the selective processing of relevant over irrelevant information. While much is known about attention, the mechanisms that support expectations about statistical regularities are not well-understood. The hippocampus has been implicated as a key structure involved in or perhaps necessary for the learning of statistical regularities, consistent with its role in various kinds of learning and memory. Here, we tested this hypothesis using a motion discrimination task in which we manipulated the most likely direction of motion, the degree of attention afforded to the relevant stimulus, and the amount of available sensory evidence. We tested memory-impaired patients with bilateral damage to the hippocampus and compared their performance with controls. Despite a modest slowing in response initiation across all task conditions, patients performed similar to controls. Like controls, patients exhibited a tendency to respond faster and more accurately when the motion direction was more probable, the stimulus was better attended, and more sensory evidence was available. Together, these findings demonstrate a robust, hippocampus-independent capacity for learning statistical regularities in the sensory environment in order to improve information processing.

Voluntary and Stimulus-Induced Attention Detected as Motion Sensation

Perception ◽  
1993 ◽  
Vol 22 (5) ◽  
pp. 517-526 ◽  
Author(s):  
Okihide Hikosaka ◽  
Satoru Miyauchi ◽  
Shinsuke Shimojo
Keyword(s):  
Information Processing ◽  
Response Bias ◽  
Visual Information ◽  
Stimulus Change ◽  
Early Stage ◽  
Visual Information Processing ◽  
Salient Object ◽  
Voluntary Attention ◽  
Top Down ◽  
Bottom Up

Attention may be drawn passively to a visually salient object. We may also actively direct attention to an object of interest. Do the two kinds of attention, passive and active, interact and jointly influence visual information processing at some neural level? What happens if the passive and active attentions come into conflict? These questions were addressed with the aid of a novel psychophysical technique which reveals an attentional gradient as a sensation of motion in a line which is presented instantaneously. The subjects were asked to direct attention with voluntary effort: to the side opposite to a stimulus change, to an object with a predetermined colour, and to an object moving smoothly. In every case the same motion sensation was induced in the line from the attended side to the unattended side. This voluntary attention, however, can easily and quickly be distracted by a change in the periphery, though it can be regained within a period of 200 to 500 ms. The results suggest that the line motion can be induced in voluntary (top-down) as well as stimulus-driven (bottom-up) situations, thus indicating the truly attentional nature of the effect, rather than it being some kind of retinotopic sensory artifact or response bias. The results also suggest that these two kinds of attention have facilitatory effects acting together on a relatively early stage of visual information processing.

Perceptual and Conceptual Information Processing in Schizophrenia and Depression

1995 ◽  
Vol 80 (2) ◽  
pp. 447-465 ◽  
Author(s):  
Elizabeth K. Dreben ◽  
John H. Fryer ◽  
Douglas M. McNair
Keyword(s):  
Information Processing ◽  
Rule Learning ◽  
Top Down ◽  
Bottom Up ◽  
Conceptual Information ◽  
Conceptual Processing ◽  
Schizophrenic Patients ◽  
Schizophrenic Group ◽  
Information Processing Strategy ◽  
Normal Adults

Schizophrenic patients ( n = 20), depressive patients ( n = 20), and normal adults ( n = 20) were compared on global vs local analyses of perceptual information using tachistoscopic tasks and on top-down vs bottom-up conceptual processing using card-sort tasks. The schizophrenic group performed more poorly on tasks requiring either global analyses (counting lines when distracting circles were present) or top-down conceptual processing (rule learning) than they did on tasks requiring local analyses (counting heterogeneous lines) or bottom-up processing (attribute identification). The schizophrenic group appeared not to use conceptually guided processing. Normal adults showed the reverse pattern. The depressive group performed similarly to the schizophrenic group on perceptual tasks but closer to the normal group on conceptual tasks, thereby appearing to be less dependent on a particular information-processing strategy. These deficits in organizational strategy may be related to the use of available processing resources as well as the allocation of attention.

scholarly journals The Curious Incident of Attention in Multisensory Integration: Bottom-up vs. Top-down

2016 ◽  
Vol 29 (6-7) ◽  
pp. 557-583 ◽  
Author(s):  
Emiliano Macaluso ◽  
Uta Noppeney ◽  
Durk Talsma ◽  
Tiziana Vercillo ◽  
Jess Hartcher-O’Brien ◽  
...  
Keyword(s):  
Prior Knowledge ◽  
Multisensory Integration ◽  
The Other ◽  
Top Down ◽  
Bottom Up ◽  
Stimulus Properties ◽  
Low Level ◽  
Other Hand ◽  
Current Task ◽  
The One

The role attention plays in our experience of a coherent, multisensory world is still controversial. On the one hand, a subset of inputs may be selected for detailed processing and multisensory integration in a top-down manner, i.e., guidance of multisensory integration by attention. On the other hand, stimuli may be integrated in a bottom-up fashion according to low-level properties such as spatial coincidence, thereby capturing attention. Moreover, attention itself is multifaceted and can be describedviaboth top-down and bottom-up mechanisms. Thus, the interaction between attention and multisensory integration is complex and situation-dependent. The authors of this opinion paper are researchers who have contributed to this discussion from behavioural, computational and neurophysiological perspectives. We posed a series of questions, the goal of which was to illustrate the interplay between bottom-up and top-down processes in various multisensory scenarios in order to clarify the standpoint taken by each author and with the hope of reaching a consensus. Although divergence of viewpoint emerges in the current responses, there is also considerable overlap: In general, it can be concluded that the amount of influence that attention exerts on MSI depends on the current task as well as prior knowledge and expectations of the observer. Moreover stimulus properties such as the reliability and salience also determine how open the processing is to influences of attention.

scholarly journals The impact of action effects on infants’ predictive gaze shifts for a non-human grasping action at 7-, 11-, and 18 months

2021 ◽  
Author(s):  
Maurits Adam ◽  
Christian Gumbsch ◽  
Martin V. Butz ◽  
Birgit Elsner
Keyword(s):  
Prior Knowledge ◽  
Prior Experience ◽  
Gaze Behavior ◽  
Top Down ◽  
Complex Interplay ◽  
Goal Object ◽  
Bottom Up ◽  
Action Effect ◽  
Event Based ◽  
The Impact

During the observation of goal-directed actions, infants usually predict the goal when the action and the agent are familiar, but they do not as easily predict the goal when the action or the agent are unfamiliar. Recent theoretical accounts suggest that predictive gaze behavior relies on a complex interplay between bottom-up- (e.g., agency cues) and top- down information (e.g., prior experience with the action), depending on an observer’ prior knowledge about the unfolding action event. Based on these accounts, we hypothesized that during the observation of grasping actions performed by a mechanical claw, younger infants would need agency cues to show predictive gaze behavior, whereas older infants would be able to show predictive gaze behavior regardless of agency cues. Therefore, we presented 7-, 11-, and 18-month-old infants with videos of a mechanical claw that repeatedly approached and grasped a goal object and then either did or did not produce a salient action effect. The 7-month-olds were not predictive regardless of the salient action effect, the 11-month-olds were only predictive when the salient action effect was presented, and the 18-month-olds were predictive regardless of the salient action effect. These results therefore support the idea of a complex interplay between bottom-up and top-down information as a crucial factor for the production of predictive gaze behavior during the observation of goal-directed actions performed by mechanical agents.

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