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PubMed1977

[Neurocybernetic basis of hallucinations and related illusions].

Present concepts of circuits of neurons involved in the development of regular perception are used as a basis for discussing possible processes proceeding in these circuits and producing hallucinations and other illusions and false perceptions in mental patients or normal subjects.

Affective Symptoms↗
PubMed2005

Out-of-body experience, heautoscopy, and autoscopic hallucination of neurological origin Implications for neurocognitive mechanisms of corporeal awareness and self-consciousness.

Autoscopic phenomena (AP) are rare illusory visual experiences during which the subject has the impression of seeing a second own body in extrapersonal space. AP consist of out-of-body experience (OBE), autoscopic hallucination (AH), and heautoscopy (HAS). The present article reviews and statistically analyzes phenomenological, functional, and anatomical variables in AP of neurological origin (n = 41 patients) that have been described over the last 100 years. This was carried out in order to further our understanding of the underlying mechanisms of AP, much as previous research into the neural bases of body part illusions has demystified these latter phenomena. Several variables could be extracted, which distinguish between or are comparable for the three AP providing testable hypotheses for subsequent research. Importantly, we believe that the scientific demystification of AP may be useful for the investigation of the cognitive functions and brain regions that mediate processing of the corporeal awareness and self consciousness under normal conditions.

Awareness↗
PubMed1976

Psychohysical hallucinations of orientation and spatial frequency.

After inspection of vertical sinusoidal gratings at least three distinct types of subjective or "hallucinated" patterns can be seen on a uniform test field. One type, here called horizontal streaming (H), is already well-known from the work of MacKay. A second type (V) looks like aroughly sinusoidal grating about 1-5 octaves above the adapting spitial frequency. Under optimal conditions a second vertical component appears at about 2 octaves below the adapting frequency. The third category of aftereffect consists of diagonal lines (D) at two orientations (about +/-40 degrees from vertical). The spatial-frequency band at these two orientations appears to be fairly broad, but roughly similar to the adapting frequency. The duration and strength of D increased, while V declined, at higher adapting spatial frequencies. D and V were increasing functions of adapting contrast, while H appeared abruptly only after the highest adapting contrast. H, D, and V are thus all functionally distinct. A schematic model of cortical organization is proposed to account for these phenomena. Pattern channels selective for a given orientation are grouped together with movement channels selective for the orthogonal direction. Antagonism between channels within such "modules" accounts for the streaming effect (H). Inhibition between modules tuned to different orientations and spatial frequencies accounts for the D and V effects: after adaptation of channels in one module, neighbouring module(s) are released from inhibition to produce a spurious response which is seen as a grating-like object in the adapted part of the visual field. During flickering adaptation a "halluncinated" lattice can be seen superimposed on the adapting grating. It apparently consists of Fourier components more remote from the adapting pattern than D and V are. This disinhibitory effect is strong confirmation of the inhibitory model. The regular and highly organized matrix of channels implied by these experiments may constitute a cortical hypercolumn conducting a coarse, piecewise Fourier transformation of the retinal image.

Figural Aftereffect↗
PubMedDate not supplied

The cognitive neuropsychiatry of auditory verbal hallucinations: an overview.

INTRODUCTION: The cognitive neuropsychiatric approach to auditory verbal hallucinations (AVHs) attempts to explain the phenomena in cognitive or information-processing terms and ultimately their brain bases. METHODS: A narrative review of the literature and an overview of this special issue of Cognitive Neuropsychiatry. RESULTS: First, an operational definition of AVHs is offered. Next, clues to etiology are derived from a detailed consideration of the clinical phenomenology of "voices", their form and content. Functional and structural neuroimaging studies suggest the importance of left-side language areas in the generation/perception of AVHs. CONCLUSIONS: Existing cognitive neuropsychiatric models provide a useful framework for the understanding of AVHs. However, data need to be applied more specifically to these models so that they may be refined.

Journal Article↗
PubMed2005

Auditory hallucinations: failure to inhibit irrelevant memories.

INTRODUCTION: The frequency of auditory hallucinations (AH) is associated with efficiency in inhibiting irrelevant memories, suggesting that the presence of AH may be related to the intrusion of strongly activated representations in memory. Therefore, we hypothesised that the inability to suppress irrelevant memories would be found only in patients currently experiencing AH. METHOD: Performance on a repeated, continuous recognition task was examined in 23 schizophrenia patients with AH present, 20 schizophrenia patients with AH absent, and 24 healthy controls. RESULTS: Patients with current AH made significantly more inappropriate responses (false alarms) to distractors seen on previous runs of the task than nonhallucinating patients. The ability to detect targets (hits) was significantly better in healthy controls than schizophrenia patients, however, there was no significant difference between the two patient subgroups. CONCLUSIONS: The findings confirm that the presence of AH involves a failure to suppress memories that are not relevant to ongoing reality. We propose that a combination of deficits in inhibition and (episodic) memory provides a useful model of AH, which can accommodate many of the characteristic features of the symptom and fits well with the neuroanatomical circuitry that is believed to underlie the occurrence of AH.

Journal Article↗
PubMed2025

Privacy-hardened and hallucination-resistant synthetic data generation with logic-solvers.

MOTIVATION: Machine-generated or synthetic data is a valuable resource for training artificial intelligence algorithms, evaluating rare workflows, and sharing data under stricter data legislations. However, current statistical and deep learning methods struggle with large data volumes, are prone to hallucinating scenarios incompatible with reality, and seldom quantify privacy meaningfully. RESULTS: Here, we introduce Genomator, a logic solving approach (SAT solving), which efficiently produces private and realistic representations of the original data. We demonstrate the method on genomic data, which arguably is the most complex and private information. We benchmark Genomator against state-of-the-art methodologies (Markov generation, Wasserstein Generative Adversarial Network and Conditional Restricted Boltzmann Machines), demonstrating a 40%-530% accuracy improvement and 57%-172% higher privacy. Genomator is also 3-100 times more efficient, making it the only tested method that scales to whole genomes. We show the universal trade-off between privacy and accuracy, and use Genomator's tuning capability to cater to all applications along the spectrum, from provable private representations of sensitive cohorts, to datasets with indistinguishable pharmacogenomic profiles. Demonstrating the production-scale generation of tuneable synthetic genomes hold great potential for balancing underrepresented populations in medical research and advancing global data exchange. AVAILABILITY AND IMPLEMENTATION: Genomator is available at https://github.com/csiro/genomator.

Algorithms↗