Biology subjects

Sommer, I. E.

Publications and source records attributed to Sommer, I. E..

6 recordsLinked to original sources

bioRxiv2026

Teaching others reveals hidden structure in conceptual cognitive maps

Disorganized thought is a core feature of the psychosis spectrum. It is recognized, clinically and in daily life, through language, yet its proposed cognitive basis, shallow cognitive maps, the relational structures that organize knowledge, has been tested almost exclusively with task performance and neural measures. Here we show that the organization of a learned conceptual map can be read out from natural speech. Adults varying in schizotypal cognitive disorganization (n = 107) learned the same two-dimensional conceptual structure from images or sentences, then described their memory strategy and explained the material to a novice. Explaining elicited two-dimensional spatial descriptions selectively after image-based learning. Higher cognitive disorganization was associated with answers that tracked the question asked less closely, on an automated, rater-free embedding measure robust to report language, again selectively after image-based learning. Natural speech thus provides a scalable behavioral readout of conceptual map organization and its disorganization.

neuroscience↗

bioRxiv2025

Disorganization impairs cognitive maps built from visual inputs

Background and HypothesisCognitive disorganization is a core disturbance across the psychosis spectrum, characterized by difficulties integrating perceptual information into coherent representations. How such disturbances affect the construction of internal cognitive maps remains unclear. A key question is whether these maps emerge from visual input as readily as from language structure. We hypothesized that cognitive disorganization would impair cognitive maps derived from visual input while sparing performance when structure was provided linguistically. Study DesignParticipants with varying schizotypy learned food items associated with two attributes: who consumed the food (age group) and when it was consumed (time of day). These attributes were presented as images or language descriptions and organized in a two-dimensional (2D) conceptual space. Participants then completed similarity judgment and reward-learning tasks requiring inference of the underlying relational structure. Study ResultsAmong individuals with higher cognitive disorganization, 2D distances were less predictive of similarity judgments, but only when relational structure had to be inferred from visual input. In the reward-learning task, computational modeling indicated that decisions were guided by spatial representations (Gaussian process). Higher cognitive disorganization was associated with weakened spatial generalization when structure had to be inferred from visual input, but not when it was provided through language. ConclusionsCognitive disorganization disrupts the ability to build and use cognitive maps from visual input, while performance appeared preserved when structure was conveyed through language. These findings support the shallow cognitive map hypothesis and suggest that cognitive disorganization selectively disrupts the transformation of perceptual input into stable relational representations.

neuroscience↗

bioRxiv2021

Brain Networks Detectable by fMRI during On-Line Self Report of Hallucinations in Schizophrenia

An analysis of an internationally shared functional magnetic resonance imaging (fMRI) data involving healthy participants and schizophrenia patients extracted brain networks involved in listening to radio speech and capture hallucination experiences. A multidimensional analysis technique demonstrated that for radio-speech sound files, a brain network matching known auditory perception networks emerged, and importantly, displayed speech-duration-dependent hemodynamic responses (HDRs), confirming fMRI detection of these speech events. In the hallucination-capture data, although a sensorimotor (response) network emerged, it did not show hallucination-duration-dependent HDRs. We conclude that although fMRI retrieved the brain network involved in generating the motor responses indicating the start and end of an experienced hallucination, the hallucination event itself was not detected. Previous reports on brain networks detected by fMRI during hallucination capture is reviewed in this context.

neuroscience↗

bioRxiv2020

Connectivity patterns of task-specific brain networks allow individual prediction of cognitive symptom dimension of schizophrenia and link to molecular architecture

BackgroundDespite the marked inter-individual variability in the clinical presentation of schizophrenia, it remains unclear the extent to which individual dimensions of psychopathology may be reflected in variability across the collective set of functional brain connections. Here, we address this question using network-based predictive modeling of individual psychopathology along four data-driven symptom dimensions. Follow-up analyses assess the molecular underpinnings of predictive networks by relating them to neurotransmitter-receptor distribution patterns. MethodsWe investigated resting-state fMRI data from 147 schizophrenia patients recruited at seven sites. Individual expression along negative, positive, affective, and cognitive symptom dimensions was predicted using relevance vector machine based on functional connectivity within 17 meta-analytic task-networks following a repeated 10-fold cross-validation and leave-one-site-out analyses. Results were validated in an independent sample. Networks robustly predicting individual symptom dimensions were spatially correlated with density maps of nine receptors/transporters from prior molecular imaging in healthy populations. ResultsTen-fold and leave-one-site-out analyses revealed five predictive network-symptom associations. Connectivity within theory-of-mind, cognitive reappraisal, and mirror neuron networks predicted negative, positive, and affective symptom dimensions, respectively. Cognitive dimension was predicted by theory-of-mind and socio-affective-default networks. Importantly, these predictions generalized to the independent sample. Intriguingly, these two networks were positively associated with D1 dopamine receptor and serotonin reuptake transporter densities as well as dopamine-synthesis-capacity. ConclusionsWe revealed a robust association between intrinsic functional connectivity within networks for socio-affective processes and the cognitive dimension of psychopathology. By investigating the molecular architecture, the present work links dopaminergic and serotonergic systems with the functional topography of brain networks underlying cognitive symptoms in schizophrenia.

neuroscience↗

bioRxiv2020

Neural activity precedes conscious awareness of being in or out of a transient hallucinatory state

Auditory verbal hallucinations, or "hearing voices", is a remarkable state of the mind, occurring in psychiatric and neurological patients, and in a significant minority of the general population. An unexplained characteristic of this phenomenon is that it transiently fluctuates, with coming and going of episodes with time. We monitored neural activity with BOLD-fMRI second-by-second before and after participants indicated the start and end of a transient hallucinatory episode during the scanning session by pressing a response-button. We show that a region in the ventro-medial frontal cortex is activated in advance of conscious awareness of going in or out of a transient hallucinatory state. There was an increase in activity initiated a few seconds before the button-press for onsets, and a corresponding decrease in activity initiated a few seconds before the button-press for offsets. We identified the time between onset and offset button-presses, extracted the corresponding BOLD time-courses from nominated regions-of-interest, and analyzed changes in the signal from 10 seconds before to 15 seconds after the response-button was pressed, which identified onset and offset events. We suggest that this brain region act as a switch to turn on and off a hallucinatory episode. The results may have implications for new interventions for intractable hallucinations.

neuroscience↗

bioRxiv2018

Paracingulate sulcus morphology and hallucinations in clinical and non-clinical groups

Hallucinations are a characteristic symptom of psychotic mental health conditions that are also experienced by many individuals without a clinical diagnosis. Research has linked the experience of hallucinations in schizophrenia to differences in the length of the paracingulate sulcus (PCS), a structure in the medial prefrontal cortex of the brain which has previously been associated with the ability to differentiate perceived and imagined information. We investigated whether this notion of a specific morphological basis for hallucinations in the paracingulate cortex extends to individuals without a clinical diagnosis by testing the hypothesis that non-clinical individuals with hallucinations have shorter PCS than non-clinical individuals without hallucinations. Structural MRI scans were examined from three demographically matched groups of individuals: 50 patients with psychotic diagnoses who experienced auditory verbal hallucinations, 50 non-clinical individuals with auditory verbal hallucinations, and 50 healthy control subjects with no life-time history of hallucinations. Measurements of paracingulate sulcal length were compared between the groups and the results verified using automated data-driven gyrification analyses. Patients with hallucinations had shorter PCS than both healthy controls and non-clinical individuals with hallucinations, with no difference between non-clinical individuals with hallucinations and healthy controls. These findings suggest that the association of shorter PCS length with hallucinations is specific to patients with a psychotic disorder. This presents challenges for continuum models of psychosis and suggests possible differences in the mechanisms underlying hallucinations in clinical and non-clinical groups.

neuroscience↗