Biology subjects

Strauch, C.

Publications and source records attributed to Strauch, C..

10 recordsLinked to original sources

bioRxiv2026

Luminance-corrected Pupillometry for Reliable Effort-tracking in Dynamic Environments

Pupillometry provides an objective way to index effort across domains. However, pupil size is strongly affected by luminance changes, which can obscure effort-related effects, and limit its use in most applied scenarios with dynamic visual input. We here introduce and validate a method to overcome this problem. To this end, participants performed an auditory n-back task of differing difficulty while viewing either constant visual input or dynamic driving movie clips. Effort was assessed physiologically (pupil size), behaviorally (accuracy), and subjectively (NASA-TLX). Accuracy, questionnaire scores, and pupil size were analyzed at the session level, while pupillometry additionally provided continuous time-resolved information. As expected, pupillometry tracked differences in effort, but its discriminability was substantially reduced under dynamic visual input. Correcting for the effects of overall luminance and moment-to-moment luminance changes using a dynamic, explainable, and open-source modeling procedure (Open-DPSM) considerably improved effort discriminability on both aggregate and time-resolved levels. At the aggregate level, luminance-corrected pupillometry slightly outperformed accuracy and NASA-TLX. Combining all three measures yielded the highest classification performance (AUC = 0.98), supporting the view that effort is multifaceted and best captured multimodally. These findings establish a practical basis for fine-grained physiological tracking of effort and arousal in both fundamental and applied research using complex, dynamic stimuli. A tutorial section guides researchers in applying luminance correction to their own pupillometric data in dynamic viewing environments using the here validated approach.

neuroscience↗

bioRxiv2026

Attentional selection is a neuroeconomic decision

Sensorimotor decisions require balancing extrinsic rewards against intrinsic action costs. How these signals are integrated during rapid eye-movement choices remains unclear. We show that human saccade selection follows cost-benefit computations consistent with neuroeconomic decision-making. Across two experiments, participants maximized rewards and minimized effort-costs. Reward titration revealed that more effortful saccades required higher monetary rewards to be chosen equally often. While effort-costs affected choices linearly, small reward differences shifted choices more than equally-sized larger ones. Furthermore, effort-cost (but not reward) differences regulated decision engagement: Deliberation was extended only when cost differences were large. Together, costs and rewards play dissociable roles in saccade selection, positioning eye movements as a tractable model system for economic decision-making.

neuroscience↗

bioRxiv2025

Pupil size reveals the perceptual quality and effortless nature of synesthesia

Synesthesia describes cross-over processes that can generate extra conscious percepts, such as seeing additional color when reading numbers. While existing research focuses on the mechanisms and effects of synesthetic associations, it often overlooks its most distinctive feature: unique sensory phenomenology. Here, we introduce pupillometry as an objective physiological measure of synesthetic color phenomenology. Across 16 grapheme-color synesthetes and two matched control groups, pupil responses tracked the brightness of synesthetic colors under constant physical visual input, scaling with self-reported strength. Synesthetic colors elicited pupil dynamics comparable to real colors, dissociating synesthetes from non-synesthetes. These responses emerged too rapidly to reflect imagery and scaled with reported color brightness, revealing cross-over caused genuine perceptual processing. Controls required to generate color associations showed greater effort-linked pupil dilation than synesthetes or controls who did not report colors, providing evidence for the effortless nature of synesthesia. Synesthesia thus provides a tractable human model for studying physiologically measurable phenomenology. Significance statementHow can we measure what someone actually experiences? Synesthesia, in which stimuli such as numbers can evoke cross-over sensations like seeing colors, provides a rare test case. Here we make this extraordinary sensation objectively measurable and show that it has a distinct sensory signature. We find that pupil size reflects the brightness of synesthetic colors even when physical light remains constant. Pupils constrict for bright colors and dilate for dark ones, revealing the quality and strength of the percept. These responses emerge rapidly and differ from those of non-synesthetes. Together, synesthesia provides a tractable model for studying internally generated sensations, with pupillometry offering a direct, measurable window into conscious perception.

neuroscience↗

bioRxiv2025

Anticipated Relevance Prepares Visual Processing for Efficient Memory-Guided Selection

Finding an object typically involves using working memory to select relevant visual information at the right time. Using EEG, we investigated how predictable changes in stimulus relevance influence top-down visual selection. Participants memorized an oriented grating, followed by a cue indicating which of two sequentially presented probes was relevant for a memory-match/-mismatch judgment. Consistent with earlier work, relevant probes evoked stronger univariate responses than irrelevant probes. Furthermore, responses to (memory-matching and memory-mismatching) probes were more distinct when they were relevant compared to irrelevant. Crucially, using rapid invisible frequency tagging (RIFT), we found that visual responses to the (empty) probe location were enhanced even before the presentation of relevant (compared to irrelevant) probes. Predictable changes in stimulus relevance, therefore, induce both pro-active and re-active changes in visual processing. We conclude that anticipating the (ir)relevance of upcoming visual events enables the visual system to prepare for efficient memory-guided visual selection.

neuroscience↗

bioRxiv2025

Population-Level Activity Dissociates Preparatory Overt from Covert Attention

The neural signatures of preparing overt eye movements and directing covert spatial attention overlap as they recruit the same brain areas. Yet, these neural signatures are dissociable at the single-cell level: Specific cells within visuo-oculomotor areas are exclusively involved in motor preparation or covert attention. Nevertheless, it has been proposed that many cells in visuo-oculomotor areas are involved in both motor preparation and covert attention, and consequently their neural signatures should functionally overlap to a large degree. Here, we directly tested this proposal: we combined human (both sexes) EEG with sensitive decoding techniques to investigate whether the neural signatures of preparatory overt and covert attention are dissociable across large-scale neuronal populations. We found that neural decoding reliably discerned whether overt or covert attention was shifted well before saccade initiation. Further, inverted encoding modeling revealed earlier and sharper spatially-tuned activity in preparatory overt than in covert attention. We then asked whether preparatory overt attention achieved sharper spatially-tuned activity by using more-of-the-same covert attention, or by recruiting additional spatially selective neural processing. Cross-decoding results demonstrated that preparatory overt attention recruited at least one additional, frontal process. This additional spatially selective process emerged early and likely reflects motor preparation or predictive remapping. To summarize, we found that the neural signatures of overt and covert attention overlap, yet diverge rapidly, in part because overt attention employs an additional spatially selective neural process. Extending beyond a dissociation on the single-cell level, our findings demonstrate that population-level neural activity dissociates preparatory overt from covert attention. Significance statementThe world provides much more visual input than the brain can process simultaneously. Spatial visual attention allows for the selective processing of only the most important parts of this input. Spatial attention shifts either overtly (with an eye movement) or covertly (without an accompanying eye movement). The neural signatures underlying these types of spatial attention have long thought to overlap to a large degree. This strong overlap was thought to only break down at the level of single neurons. In our EEG study, we instead demonstrate that large populations of neurons dissociate overt from covert attention. Our results show that the neural signatures of overt and covert attention differ on a much broader scale than previously thought.

neuroscience↗

bioRxiv2024

Effort Drives Saccade Selection

What determines where to move the eyes? We recently showed that pupil size, a well-established marker of effort, also reflects the effort associated with making a saccade (saccade costs). Here we demonstrate saccade costs to critically drive saccade selection: when choosing between any two saccade directions, the least costly direction was consistently preferred. Strikingly, this principle even held during search in natural scenes in two additional experiments. When increasing cognitive demand experimentally through an auditory counting task, participants made fewer saccades and especially cut costly directions. This suggests that the eye-movement system and other cognitive operations consume similar resources that are flexibly allocated among each other as cognitive demand changes. Together, we argue that eye-movement behavior is tuned to adaptively minimize saccade-inherent effort.

neuroscience↗

bioRxiv2024

Sensory Input Matching Visual Working Memory Guides Internal Prioritization

Adaptive behavior necessitates the prioritization of the most relevant information in the environment (external) and in memory (internal). Internal prioritization is known to guide the selection of external sensory input, but the reverse may also be possible: Does the environment guide the prioritization of memorized material? Here we addressed whether reappearing sensory input can facilitate the prioritization of other non-reappearing memorized items held in visual working memory (VWM). Participants (total n = 96) memorized three orientations. Crucially some, but not all, items maintained in VWM were made available again in the environment. These reappearing items never had to be reproduced later. Experiment 1 showed that the reappearance of all but one memory item benefited accuracy and speed to the same extent as a spatial retro cue. This shows that reappearing items allow for the dynamic prioritization of another non-reappearing memorized item. What aspects of the reappearing sensory input drive this effect? Experiments 2-4 demonstrated that prioritization was facilitated most if reappearing items matched VWM content in terms of both location and orientation. Sensory input fully matching VWM is possibly processed more efficiently and/or protects against interference, ultimately leading to stronger prioritization of other memory content. We propose that the link between sensory processing and VWM is bidirectional: internal representations guide the processing of sensory input, which in turn facilitates the prioritization of other VWM content to subserve adaptive behavior. All data and analysis scripts are available here: https://osf.io/qzvkc/.

neuroscience↗

bioRxiv2024

The suprapyramidal and infrapyramidal blades of the dentate gyrus exhibit different GluN subunit content and dissimilar frequency-dependent synaptic plasticity in vivo

The entorhinal cortex sends afferent information to the hippocampus by means of the perforant path(PP), whereby the medial PP (MPP) is believed to convey information about spatial context and the lateral PP (LPP) may convey information about item identity. This information is encoded by means of synaptic plasticity. The PP input to the dentate gyrus(DG) terminates in the suprapyramidal (upper/inner) and infrapyramidal (lower/outer) blades. To what extent frequency-dependent synaptic plasticity in these blades differs is unclear. Here, we compared MPP-DG responses in the supra- (sDG) and infrapyramidal blades (iDG) of freely behaving adult rats and found that synaptic plasticity in the sDG is broadly frequency-dependent whereby long-term depression (LTD, >24h) is induced with stimulation at 1Hz, short-term depression (<2h) is triggered by 5 or 10Hz and long-term potentiation (LTP) of increasing magnitudes is induced by 200 and 400 Hz stimulation, respectively. By contrast, although the iDG expresses STD following 5 or 10Hz stimulation, LTD induced by 1Hz is weaker, LTP is not induced by 200Hz and LTP induced by 400Hz stimulation is significantly smaller in magnitude and is less persistent (<4h) compared to LTP in sDG. Furthermore, the stimulus-response relationship of the iDG is suppressed compared to sDG. Patch clamp recordings, in vitro, revealed reduced firing frequencies in response to high currents, and different action potential thresholds in iDG compared to sDG. Assessment of the expression of GluN subunits revealed significantly lower expression levels of GluN1, GluN2A and GluN2B in iDG compared to sDG. Taken together, these data indicate that synaptic plasticity in the infrapyramidal blade of the dentate gyrus is weaker, less persistent and less responsive to afferent frequencies than synaptic plasticity in sDG. Effects may be mediated by weaker NMDA receptor expression in iDG. These characteristics may explain reported differences in experience-dependent information processing in sDG versus iDG.

neuroscience↗

bioRxiv2023

SSVEPs reveal dynamic (re-)allocation of spatial attention during maintenance and utilization of visual working memory

Visual Working Memory (VWM) allows us to temporarily store goal-relevant information to guide future behavior. Prior work has established that VWM and spatial attention are intrinsically connected - even if location is irrelevant for responses: behavioral and neural correlates of attention show spatial biases, specific to the location at which memory items were encoded. This suggests that VWM is spatially organized and that maintaining information might rely on the allocation of spatial attention towards the location of memory items. Importantly, attention often needs to be dynamically redistributed between several locations, e.g. in preparation for an upcoming probe. Very little is known about how attentional resources are distributed between multiple locations during a VWM task and even less about the dynamic changes governing such attentional shifts over time. This is largely due to the inability to use behavioral outcomes to reveal fast dynamic changes within trials. We here demonstrate EEG Steady-State Visual Evoked Potentials (SSVEPs) to successfully track the dynamic allocation of spatial attention during a VWM task. Participants were presented with to-be-memorized gratings and distractors at two distinct locations. During maintenance and retrieval, each location was tagged with a disk flickering at either 10 or 13 Hz. This allowed us to dynamically track attention allocated to memory and distractor items via their coupling with space by quantifying the amplitude and coherence of SSVEP responses in the EEG signal to flickering stimuli at the former memory and distractor locations. SSVEP responses at memory locations did not differ from distractor locations during early parts of the maintenance window. However, shortly before probe comparison, we observed a decrease in SSVEP coherence over distractor locations indicative of a reallocation of spatial attentional resources. Reaction times were shorter when preceded by stronger decreases in SSVEP coherence at distractor locations, reflecting the reallocation of attention from the distractor location to the memory location or towards the distinct upcoming probe location. Broader Significance We demonstrate that SSVEPs can inform about dynamic processes in VWM, even if location does not have to be reported by participants. This finding not only supports the notion of a spatially organized VWM, but also reveals that SSVEPs betray a dynamic prioritization process of working memory items and locations over time that is directly predictive of memory performance.

neuroscience↗

bioRxiv2021

Why do hippocampal mossy cells matter? It depends on the frequency and context.

The discrimination of similar episodes and places, and their representation as distinct memories, depend on a process called pattern separation that relies on the circuitry of the hippocampal dentate gyrus (DG). Mossy cells (MCs) are key neurons in the circuitry, but how they influence DG network dynamics, function, and seizure risk has not been fully elucidated. We found the net impact of MCs was inhibitory at physiological frequencies connected with learning and behaviour, and their absence associated with deficits in pattern separation and spatial memory; at higher frequencies, their net impact was excitatory, and their absence protected against seizures. Thus, MCs influence DG outputs in a highly dynamic manner that varies with frequency and context. One-Sentence SummaryHippocampal mossy cells are required for learning and memory; but their absence protects against seizures.

neuroscience↗