Biology subjects

Weilnhammer, V.

Publications and source records attributed to Weilnhammer, V..

3 recordsLinked to original sources

bioRxiv2024

Ischemic lesions to inferior frontal cortex alter the dynamics of conscious visual perception

Whether the prefrontal cortex is part of the neural correlates of conscious visual perception has been subject to longstanding debate. Recent work, using functional magnetic resonance imaging (fMRI) and repetitive transcranial magnetic stimulation (rTMS) to induce virtual lesions, has illustrated a key role of the right inferior frontal cortex (IFC) in the detection and resolution of perceptual ambiguities. Here, we sought to validate an active role of the IFC in conscious perception by evaluating how loss-of-function in patients with ischemic stroke in this region influences processing of ambiguous visual information. To this end, twenty-three patients (11 female, mean age 70.65 {+/-} 1.2 years) with chronic (>6 months), right-hemispheric ischemic stroke lesions within the MCA-territory (9 patients with IFC lesions, 14 without) performed a bistable perception task, having to report the perceived direction of rotation of an ambiguous random-dot-kinematogram (RDK). As hypothesized, patients with IFC lesions showed significantly fewer perceptual changes compared to patients without IFC lesions (IFC 44.9 {+/-} 46.3 s, non-IFC 28.2 {+/-} 37.1 s, T(182.9) =3.1, p = 2.2 x 10-3). Importantly, this effect remained significant when controlling for age, sex, stroke severity and lesion volume (T(5.97) = -2.9, p =0.026). Our results support the notion that the IFC is crucial for resolving perceptual ambiguities, suggesting an active role of frontal cortex in shaping conscious visual experience.

neuroscience↗

bioRxiv2024

Anterior insular activity signals perceptual conflicts induced by temporal and spatial context

The signals registered by our senses are inherently ambiguous. Subjective experience, by contrast, is informative: it portrays one interpretation of the sensory environment at a time while discarding competing alternatives. This is exemplified by bistable perception, where ambiguous sensory information induces prolonged intervals of alternating unambiguous perceptual states. According to predictive-processing accounts of bistable perception, perceptual experiences in the recent past constitute a predictive context that stabilizes perception, while sensory information that is in conflict with this predictive context evokes prediction errors. These prediction errors are thought to drive spontaneous perceptual switches. We asked whether this mechanism generalizes to conflicts between other forms of predictive context and sensory information. To this aim, we investigated the neural correlates of perceptual conflicts with temporal and spatial context during bistable perception using functional magnetic resonance imaging (fMRI). Twenty-six healthy participants viewed serial presentations of ambiguous structure-from-motion stimuli either in isolation (conflict with temporal context) or embedded in a similar but unambiguous surround stimulus (conflict with spatial context). The neural correlates of conflicts with temporal and spatial context overlapped in the anterior insula bilaterally. Model-based analyses similarly yielded common prediction error signals in the anterior insula bilaterally, right inferior frontal gyrus and right inferior parietal lobe. Together, these findings point to a generic role of these frontoparietal regions in detecting perceptual conflict and thus in the construction of unambiguous perceptual experiences.

neuroscience↗

bioRxiv2024

N-Methyl-D-aspartate receptor hypofunction causes recurrent and transient failures of perceptual inference

1Perception alternates between an external mode, driven by sensory inputs, and an internal mode, shaped by prior knowledge. We found that the external mode is more prevalent during pharmacologically induced N-Methyl-D-aspartate receptor (NMDAR) hypofunction and in schizophrenia. This NMDAR-dependent increase in external mode suggests that psychotic experiences are caused by recurring dissociations of perception from prior knowledge about the world.

neuroscience↗