Biology subjects

Ester, E.

Publications and source records attributed to Ester, E..

10 recordsLinked to original sources

bioRxiv2026

Neural Measures of Human Decision Making Track Evidence Accumulation in Learned Space

Neural decision-making flexibly integrates evidence across sensory, mnemonic, and semantic domains. Yet prior demonstrations have focused on evidence that is either directly available in stimuli, retrieved from established representations, or computed relative to fixed perceptual frameworks. A fundamental question remains: does neural evidence accumulation extend to decisions based on evidence that must be computed through learned representational transformations? Here we show it does. We recorded scalp EEG while participants classified continuously-oriented visual stimuli into discrete categories defined by an experimenter-imposed boundary. Category-level evidence was operationalized as category coherence, or the angular distance between each stimulus and the learned boundary. We predicted that if neural decision mechanisms are truly domain-general, the centro-parietal positivity (CPP)--a scalp EEG potential indexing evidence accumulation--should scale with category coherence, and individual differences in CPP sensitivity should correlate with computational drift rates. Both predictions were supported: CPP slopes increased monotonically with category coherence, and individual differences in CPP slopes correlated with individual differences in drift rates across participants. These findings reveal that the brains decision machinery treats evidence identically regardless of its representational origin---whether externally available, pre-existing, or computed through learned transformations. Significance StatementEvidence accumulation is a universal principle by which brains convert information into decisions. Prior work demonstrates this mechanism for sensory evidence, memory retrieval, and evidence computed relative to fixed perceptual axes, but a critical gap remains: does it extend to decisions based entirely on learned, arbitrary rules? We show that it does. Specifically, we demonstrate that the centro-parietal positivity (CPP)--a neural marker of evidence accumulation--tracks decisions in rule-defined category space, with buildup rates that scale with distance from learned boundaries and correlate with computational measures of evidence-accumulation rate. This reveals that the brains decision machinery is flexible, adapting to evidence in any representational framework, whether externally available or internally constructed.

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bioRxiv2025

Distinct Cortical and Oculomotor Dynamics During Endogenous and Exogenous Competition in Working Memory

Working memory (WM) enables the temporary maintenance of information for guiding thought and action, but its limited capacity requires internal selective attention mechanisms to prioritize goal-relevant representations. Like external attention, internal selection can be shaped by both endogenous (goal-driven) and exogenous (stimulus-driven) factors. Classic work by Charles Folk and Roger Remington demonstrated that such factors interact competitively during external attention, producing stimulus-driven capture under certain conditions. Whether similar competitive dynamics govern internal selection remains unclear. Prior studies using retro-cue paradigms with extended cue-response delays have reported evidence for "retro-capture"--involuntary orienting toward task-irrelevant but cue-matching working memory content. Here, we combined EEG and eye-tracking to test whether retro-capture persists when the cue and response probe are simultaneous, eliminating the temporal window in which capture has previously been observed. Participants remembered two oriented bars and used either a pro-cue or an anti-cue to guide recall. Across behavioral, cortical, and oculomotor measures, we found no evidence for retro-capture. Instead, competition between endogenous and exogenous selection mechanisms uniformly delayed the selection of task-relevant WM content, with delays evident in response times, lateralized alpha-band activity, and gaze biases toward remembered locations. Our findings indicate that retro-capture is not an obligatory consequence of endogenous-exogenous competition in WM but may depend on the temporal separation between cue and action.

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bioRxiv2025

Human eye movements track stimulus meaning

Categorization, or the ability to group stimuli according to behavioral relevance, is a cornerstone of abstract cognition. Neurophysiological studies in non-human primates have revealed that category-selective signals are robustly encoded in oculomotor structures, including the lateral intraparietal area (LIP) and superior colliculus (SC), and that this encoding produces small, uninstructed eye movements that reflect learned category distinctions. Whether a similar phenomenon exists in humans is unknown. Here, we show that human gaze behavior encodes abstract categorical information independent of physical stimulus features. In three experiments, participants learned to classify oriented stimuli according to an arbitrary rule while their eye movements were recorded. Category identity could be reliably decoded from records of gaze position, particularly on trials with accurate categorization. A delayed match-to-category task confirmed that category-selective gaze patterns emerged before any motor response could be planned, ruling out response-related confounds. A further experiment demonstrated that gaze patterns tracked both orientation and color categories, confirming that the decoded signal reflects the observers behavioral state rather than stimulus-evoked oculomotor biases. These findings establish that human oculomotor behavior carries abstract cognitive signals, paralleling recent non-human primate results linking incidental gaze shifts to the multiplexed encoding of category information within oculomotor networks.

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bioRxiv2024

Cortical traveling waves link visual and frontal cortex during working memory-guided behavior

Cortical traveling waves, or global patterns of activity that extend over several centimeters of the cortical surface, are a key mechanism for guiding the spatial propagation of neural activity and computational processes across the brain. Recent studies have implicated cortical traveling waves in successful short- and long-term memory encoding, storage, and retrieval. However, human memory systems are fundamentally-action oriented: eventually, the contents of memory must be utilized to produce appropriate behaviors. Cortical traveling waves could contribute to the production and control of memory-guided behaviors by flexibly routing information between brain areas responsible for storing memory content and brain areas responsible for planning and executing actions. Here, using short-term memory as a test case, we report evidence supporting this possibility. By applying image-based analyses to published human EEG studies, we show that the initiation of a memory-guided behavior is accompanied by a low-frequency (2-6 Hz) feedforward (occipital to frontal) traveling wave that predicts intra- and inter-individual differences in response onset, while the termination of a memory-guided behavior is followed by a higher frequency (14-32 Hz) feedback (frontal-to-occipital) traveling wave. Control analyses established that neither waveform could be explained by nuisance factors (e.g., propagation of visually-evoked potentials, eye movements, or passive volume conduction). Moreover, both waveforms required an overt behavior: when participants selected task-relevant memory content and prepared but did not yet execute an action based on this content, neither waveform was observed. Our findings suggest a role for traveling waves in the generation and control of memory-guided behaviors by flexibly organizing the timing and direction of interactions between brain regions involved in memory storage and action.

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bioRxiv2022

The Entorhinal-DG/CA3 Pathway in the Medial Temporal Lobe Retains Visual Working Memory of a Simple Surface Feature

Classic models consider working memory (WM) and long-term memory as distinct mental faculties that are supported by different neural mechanisms. Yet, there are significant parallels in the computation that both types of memory require. For instance, the representation of precise item-specific memory requires the separation of overlapping neural representations of similar information. This computation has been referred to as pattern separation, which can be mediated by the entorhinal-DG/CA3 pathway of the medial temporal lobe (MTL) in service of long-term episodic memory. However, although recent evidence has suggested that the MTL is involved in WM, the extent to which the entorhinal-DG/CA3 pathway supports precise item-specific WM has remained elusive. Here, we combine an established orientation WM task with high-resolution fMRI to test the hypothesis that the entorhinal-DG/CA3 pathway retains visual WM of a simple surface feature. Participants were retrospectively cued to retain one of the two studied orientation gratings during a brief delay period and then tried to reproduce the cued orientation as precisely as possible. By modeling the delay-period activity to reconstruct the retained WM content, we found that the anterior-lateral entorhinal cortex (aLEC) and the hippocampal DG/CA3 subfield both contain item-specific WM information that is associated with subsequent recall fidelity. Together, these results highlight the contribution of MTL circuitry to item-specific WM representation.

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bioRxiv2022

Changes in behavioral priority influence the accessibility but not the quality of working memory content.

Evolving behavioral goals require the existence of selection mechanisms that prioritize task-relevant working memory (WM) content for action. Selecting an item stored in WM is known to blunt and/or reverse information loss in stimulus-specific representations of that item reconstructed from human brain activity, but extant studies have focused on all-or-none circumstances that allow or disallow an agent to select one of several items stored in WM. Conversely, behavioral studies suggest that humans can flexibly assign different levels of priority to different items stored in WM, but how doing so influences neural representations of WM content is unclear. One possibility is that assigning different levels of priority to items in WM influences the quality of those representations, resulting in more robust neural representations of high- vs. low-priority WM content. A second - and non-exclusive - possibility is that asymmetries in behavioral priority influence how rapidly neural representations of high- vs. low-priority WM content can be selected and reported. We tested these possibilities in two experiments by decoding high- and low-priority WM content from EEG recordings obtained while human volunteers performed a retrospectively cued WM task. Probabilistic changes in the behavioral relevance of a remembered item had no effect on our ability to decode it from EEG signals; instead, these changes influenced the latency at which above-chance decoding performance was reached. Thus, our results indicate that probabilistic changes in the behavioral relevance of WM content influence the ease with which memories can be accessed and retrieved independently of their strength.

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bioRxiv2022

Competition between endogenous and exogenous attention delays the selection of task-relevant working memory content.

External selective attention is mediated by competition between endogenous (goal-driven) and exogenous (stimulus-driven) factors, with the balance of competition determining which stimuli are selected. Occasionally, exogenous factors "win" this competition and drive the selection of task-irrelevant stimuli. Endogenous and exogenous selection mechanisms may also compete to control the selection of internal representations (e.g., those stored in working memory), but how this competition manifests and whether it is resolved in the same way as external attention is unknown. Here, we leveraged the high temporal resolution of human EEG to determine how competition between endogenous and exogenous factors influences the selection of internal representations. Unlike external attention, competition between endogenous and exogenous factors did not prompt the selection of task-irrelevant working memory content. Instead, it simply delayed the endogenous selection of task-relevant working memory content by several hundred milliseconds. Thus, competition between endogenous and exogenous factors influences internal selective attention, but in a different way than external selective attention.

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bioRxiv2022

Transient and sustained visuomotor selection during working-memory guided behavior.

Working Memory (WM) is a capacity- and duration-limited system that forms a temporal bridge between fleeting sensory phenomena and possible actions. But how are the contents of WM used to guide behavior? A recent high-profile study reported evidence for simultaneous access to WM content and linked motor plans during WM-guided behavior, challenging serial models where task-relevant WM content is first selected and then mapped on to a task-relevant motor response. However, the task used in that study was not optimized to distinguish the selection of spatial versus non-spatial visual information stored in memory, nor to distinguish whether or how the chronometry of selecting non-spatial visual information stored in memory might differ from the selection of linked motor plans. Here, we revisited the chronometry of spatial, feature, and motor selection during WM-guided behavior using a task optimized to disentangle these processes. Concurrent EEG and eye position recordings revealed clear evidence for temporally dissociable spatial, feature, and motor selection mechanisms during this task, partially replicating yet also extending previous findings. More generally, our data reveal the existence of multiple WM selection mechanisms that belie conceptualizations of WM-guided behavior based on purely serial or parallel visuomotor processing.

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bioRxiv2019

Information recovery following a retrospective cue decreases with time.

Working memory (WM) performance can be enhanced by an informative cue presented during storage. This effect, termed a retrocue benefit, can be used to explore how observers prioritize information stored in WM to guide behavior. Recent studies have demonstrated that neural representations of task-relevant memoranda are strengthened following the appearance of a retrocue, suggesting that participants can consult alternative information stores to supplement active memory traces. Here, we sought to better understand the nature of these memory store(s) by asking whether they are subject to the same temporal degradation seen in active memory representations. We reconstructed and quantified representations of remembered positions from alpha-band EEG activity recorded while participants performed a retrospectively cued spatial WM task, and varied the temporal interval separating the encoding display and retrocue. Although we observed a partial recovery of location information in all cue conditions, the magnitude of recovery was linearly and inversely related to the timing of the retrocue. This suggests that participants ability to supplement active memory representations with information from additional memory stores is not static: the information maintained in these stores may be subject to temporal degredation, or the stores themselves may become more difficult to access with time.

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bioRxiv2018

Retrospective cues mitigate information loss in human cortex during working memory storage.

Working memory (WM) enables the flexible representation of information over short intervals. It is well-established that WM performance can be enhanced by a retrospective cue presented during storage, yet the neural mechanisms responsible for this benefit are unclear. Here, we tested several explanations for retro-cue benefits by quantifying changes in spatial WM representations reconstructed from alpha-band (8-12 Hz) EEG activity recorded from human participants (both sexes) before and after presentation of a retrospective cue. This allowed us to track cue-related changes in WM representations with high temporal resolution (tens of milliseconds). Participants encoded the locations of two colored discs for subsequent report. During neutral trials an uninformative cue instructed participants to remember the locations of both discs across a blank delay, and we observed a monotonic decrease in the fidelity of reconstructed spatial WM representations with time. During valid trials a 100% reliable cue indicated the color of the disc participants would be probed to report. Critically, valid cues were presented immediately after termination of the encoding display (\"valid early\", or VE trials) or midway through the delay period (\"valid late\" or VL trials). During VE trials the gradual loss of location-specific information observed during neutral trials was eliminated, while during VL trials it was partially reversed. Our findings suggest that retro-cues engage several different mechanisms that together serve to mitigate information loss during WM storage.\n\nSignificance StatementWorking memory (WM) performance can be improved by a cue presented during storage. This effect, termed a retrospective cue benefit, has been used to explore the limitations of attentional prioritization in WM. However, the mechanisms responsible for retrospective cue benefits are unclear. Here we tested several explanations for retrospective cue benefits by examining how they influence WM representations reconstructed from human EEG activity. This approach allowed us to visualize, quantify, and track the effects of retrospective cues with high temporal resolution (on the order of tens of milliseconds). We show that under different circumstances retrospective cues can both eliminate and even partially reverse information loss during WM storage, suggesting that retrospective cue benefits have manifold origins.

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