Biology subjects

Riegler, C.

Publications and source records attributed to Riegler, C..

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↗

bioRxiv2020

Coordination of two enhancers drives expression of olfactory trace amine-associated receptors

Olfactory sensory neurons (OSNs) are functionally defined by their expression of a unique odorant receptor (OR). Mechanisms underlying singular OR expression are well studied, and involve a massive cross-chromosomal enhancer interaction network. Trace amine-associated receptors (TAARs) form a distinct family of olfactory receptors, and here we find that mechanisms regulating Taar gene choice display many unique features. The epigenetic signature of Taar genes in TAAR OSNs is different from that in OR OSNs. We further identify that two TAAR enhancers conserved across placental mammals are absolutely required for expression of the entire Taar gene repertoire. Deletion of either enhancer dramatically decreases the expression probabilities of different Taar genes, while deletion of both enhancers completely eliminates the TAAR OSN populations. In addition, both of the enhancers are sufficient to drive transgene expression in the partially overlapped TAAR OSNs. We also show that the TAAR enhancers operate in cis to regulate Taar gene expression. Our findings reveal a coordinated control of Taar gene choice in OSNs by two remote enhancers, and provide an excellent model to study molecular mechanisms underlying formation of an olfactory subsystem.

neuroscience↗

bioRxiv2020

Colors everywhere: enhanced chromatic processing across the first visual synapse in the zebrafish central brain

Larval zebrafish (Danio rerio) are an ideal organism to study color vision, as their eye possesses four types of cone photoreceptors, covering most of the visible range and into the UV [1,2]. Additionally, their entire eye and nervous system are accessible to imaging, given they are naturally transparent [3-5]. Relying on this advantage, recent research has found that, through a set of color specific horizontal, bipolar and retinal ganglion cells (RGCs) [6-8], the eye then relays tetrachromatic information to several retino-recipient areas (RAs) [9,10]. The main RA is the optic tectum, receiving 97% of the RGC axons via the neuropil mass termed Arborization Field 10 (AF10) [11,12]. In this work, we aim to understand the processing of color signals at the interface between RGCs and their targets in the brain. We used 2-photon calcium imaging to separately measure the responses of RGCs and neurons in the dorsal brain to stimulation with four different colors in awake animals. We find that color information is widespread throughout the larval brain, with a large variety of color responses among RGCs, and an even greater diversity in their targets. Specific combinations of response types are localized to specific nuclei, but we observe no single color processing structure. In the main interface in this pathway, the connection between Arborization Field 10 and the tectum, we observe key elements of color processing such as enhanced signal decorrelation and improved decoding [13,14]. Finally, when presenting a richer set of stimuli, we identify parallel processing of color, motion and luminance information in the same cells/terminals, evidence of a rich color vision machinery in this small vertebrate brain.

neuroscience↗