Biology subjects

Strauch, C.

Publications and source records attributed to Strauch, C..

5 recordsLinked to original sources

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↗