Biology subjects

Hickey, C.

Publications and source records attributed to Hickey, C..

12 recordsLinked to original sources

bioRxiv2025

Complementary attentional mechanisms for the resolution of representational ambiguity in the human brain

When we view cluttered environments containing multiple objects, the neural code for individual items can become ambiguous. This reflects a capacity limit in spatially-tuned visual neurons: when multiple objects fall within the cell receptive field, output cannot be attributed to a single object. Vision models from primate electrophysiology propose this is resolved by attention, which biases competition between object representations. However, evidence in humans is sparse and inconclusive, and reliance on single-cell data limits insight into underlying mechanisms and neurophysiological scope. Here, we use a novel multivariate approach to the analysis of human EEG and concurrent EEG/MRI to address this. First, we test whether attention is recruited by representational ambiguity. Second, we identify the mechanisms that act on representations of attended and unattended objects to resolve ambiguity. Finally, we characterize the millisecond timing and whole-brain action of these mechanisms to identify pervasive effects in semantic and executive brain networks.

neuroscience↗

bioRxiv2025

Neural Oscillations Coordinate Continuous Error Correction During Force Control

Effective motor control depends on the brains ability to monitor performance and make continuous corrections. While many studies focus on discrete errors, everyday actions often require ongoing feedback-based adjustments. Here, we used an isometric force control task with EEG to investigate the neural dynamics supporting real-time error correction. Participants maintained a constant grip force with or without continuous visual feedback. With feedback, behavior showed [~]6 Hz rhythmic fluctuations, consistent with active correction. These fluctuations were mirrored in EEG activity across theta, beta, and alpha bands--oscillations linked to performance monitoring, updating, and attentional control. Without feedback, performance decayed linearly, and the corresponding neural signatures were reduced. These findings suggest that continuous sensory feedback engages a dynamic feedback loop involving distinct neural processes that support adaptive behavior. Our results highlight the importance of oscillatory activity in tracking and correcting moment-to-moment fluctuations in force, offering insight into the neural basis of feedback-loop force control.

neuroscience↗

bioRxiv2025

Predictive distractor processing relies on integrated proactive and reactive attentional mechanisms

Visual attention is shaped by statistical regularities in the environment, with spatially predictable distractors being proactively suppressed. The neural mechanisms underpinning this suppression remain poorly understood. In this study, we employed magnetoencephalography (MEG) and multivariate decoding analysis to investigate how predicted distractor locations are proactively processed in the human brain. Male and female human participants engaged in a statistical learning visual search task that required them to identify a target stimulus while ignoring a colour-singleton distractor. Critically, the distractor appeared more frequently on one side of the visual field, creating an implicit spatial prediction. Our results revealed that distractor locations were encoded in temporo-occipital brain regions prior to the presentation of the search array, supporting the hypothesis that proactive suppression guides visual attention away from predictable distractors. The neural activity patterns corresponding to this pre-search distractor processing extended to post-search activity during late attentional stages ([~]200 ms), suggesting an integrated suppressive mechanism. Notably, this generalization from pre- to post- search phases was absent in the early sensory processing stages ([~]100 ms), suggesting that post-search distractor processing is not merely a continuation of sustained proactive processing, but involves re-engagement of the same mechanism at distinct stages. These findings establish a mechanistic link between proactive and reactive processing of predictable distractors, demonstrating both shared and unique contributions to attentional selection.

neuroscience↗

bioRxiv2025

Systematic contextual biases in SegmentNT relevant to all nucleotide transformer models

Recent advances in large language models (LLMs) have extended to genomic applications, yet model robustness relative to context is unclear. Here, we demonstrate two intrinsic biases (input sequence length and nucleotide position) affecting SegmentNT results, a model included with the Nucleotide Transformer that provides nucleotide-level predictions of biological features. We demonstrate that nucleotide position within the input sequence (beginning, middle, or end) alters the nature of SegmentNTs raw prediction probabilities, which can be standardized to improve prediction consistency. While longer input sequence length improves model performance, diminishing returns suggest a surprisingly small input length of [~]3,072 nucleotides might be sufficient for many applications. We further identify a 24-nucleotide periodic oscillation in SegmentNTs prediction probabilities, revealing an intrinsic bias potentially linked to the models training tokenization (6-mers) and architecture. We identify potential approaches to account for these biases and provide generalizable insights for utilizing nucleotide-resolution functional prediction models.

bioinformatics↗

bioRxiv2025

Neural mechanisms of object prioritization in vision

Selective attention is widely thought to be sensitive to visual objects. This is commonly demonstrated in cueing studies, which show that when attention is deployed to a known target location that happens to fall on a visual object, responses to targets that unexpectedly appear at other locations on that object are faster and more accurate, as if the object in its entirety has been visually prioritized. However, this notion has recently been challenged by results suggesting that putative object-based effects may reflect the influence of hemifield anisotropies in attentional deployment, or of unacknowledged influences of perceptual complexity and visual clutter. Studies employing measures of behaviour provide limited opportunity to address these challenges. Here, we used EEG to directly measure the influence of task-irrelevant objects on the deployment of visual attention. We had participants complete a simple visual cueing task involving identification of a target that appeared at either a cued location or elsewhere. Throughout each experimental trial, displays contained task-irrelevant rectangle stimuli that could be oriented horizontally or vertically. We derived two cue-elicited indices of attentional deployment-lateralized alpha oscillations and the ADAN component of the event-related potential-and found that these were sensitive to the otherwise irrelevant orientation of the rectangles. Our results demonstrate that the allocation of visual attention is influenced by objects boundaries, supporting models of object-based attentional prioritization.

neuroscience↗

bioRxiv2024

Using N2pc variability to probe functionality: Linear mixed modelling of trial EEG and behaviour

This paper has two concurrent goals. On one hand, we hope it will serve as a simple primer in the use of linear mixed modelling (LMM) for inferential statistical analysis of multimodal data. We describe how LMM can be easily adopted for the identification of trial-wise relationships between disparate measures and provide a brief cookbook for assessing the suitability of LMM in your analyses. On the other hand, this paper is an empirical report, probing how trial-wise variance in the N2pc, and specifically its sub-component the NT, can be predicted by manual reaction time (RT) and stimuli parameters. Extant work has identified a link between N2pc and RT that has been interpreted as evidence of a direct and causative relationship. However, results have left open the less-interesting possibility that the measures covary as a function of motivation or arousal. Using LMM, we demonstrate that the relationship only emerges when the NT is elicited by targets, not distractors, suggesting a discrete and functional relationship. In other analyses, we find that the target-elicited NT is sensitive to variance in distractor identity even when the distractor cannot itself elicit consistently lateralized brain activity. The NT thus appears closely linked to attentional target processing, supporting the propagation of target-related information to response preparation and execution. At the same time, we find that this component is sensitive to distractor interference, which leaves open the possibility that NT reflects brain activity responsible for the suppression of irrelevant distractor information.

neuroscience↗

bioRxiv2024

Attentional propagation of conceptual information in the human brain

The visual environment is complicated, and humans and other animals accordingly prioritise some sources of information over others through the deployment of spatial attention. We presume that attention has the ultimate purpose of guiding the abstraction of information from perceptual experience in the development of concepts and categories. However, neuroscientific investigation has focussed closely on identification of the systems and algorithms that support attentional control, or that instantiate the effect of attention on sensation and perception. Much less is known about how attention impacts the acquisition and activation of high-level information in the brain. Here, we use machine learning of EEG and concurrently-recorded EEG/MRI to temporally and anatomically characterise the neural network that abstracts from attended perceptual information to activate and construct semantic and conceptual representations. We find that the trial-wise amplitude of N2pc - an ERP component closely linked to selective attention - predicts the rapid emergence of information about semantic categories in EEG. Similar analysis of EEG/MRI shows that N2pc predicts MRI-derived category information in a network including VMPFC, posterior parietal cortex, and anterior insula. These brain areas appear critically involved in the attention-mediated translation of perceptual information to concepts, semantics, and action plans.

neuroscience↗

bioRxiv2024

Fast feature- and category-related parafoveal previewing support natural visual exploration.

Studies on vision tend to prevent or control eye movements, while humans naturally saccade every [~]250 ms. As the oculomotor system takes [~]100 ms to initiate and execute a saccade, this leaves only [~]150 ms to identify the fixated object and select the next saccade goal. This is very little time, suggesting that vision relies on parafoveal processing before and after the eye movement. However, evidence of high-level parafoveal access is sparse. The purpose of our study was to use magnetoencephalography (MEG) combined with eye-tracking and multivariate pattern analysis to identify the neuronal dynamics of parafoveal processing which support natural visual exploration. We demonstrated that future saccade goals in the parafovea could be decoded at the feature and category level peaking at [~]90 ms and [~]160 ms respectively. Simultaneously, decoding of fixated objects at the feature and category level peaked at [~]70 ms and [~]145 ms respectively. Also decoding feature and category specific neuronal information related to past parafoveal objects were sustained for [~]230 ms after saccading away from them. The feature and category of objects in the parafovea could only be decoded if they were in the saccade goal. In sum, we provide insight on the neuronal mechanism of pre-saccadic attention by demonstrating that feature and category specific information of foveal and parafoveal objects can be extracted in succession within a [~]150 ms time-interval and may serve to plan the next saccade. This information is maintained also after fixations and may support integration across the full visual scene. Our study provides novel insight on the temporal dynamics of foveal and parafoveal processing at the feature and semantic levels during natural visual exploration.

neuroscience↗

bioRxiv2022

Statistical Learning of Distractor Suppression Down-regulates Pre-Stimulus Neural Excitability in Early Visual Cortex

Visual attention is highly influenced by past experiences. Recent behavioral research has shown that expectations about the spatial location of distractors within a search array are implicitly learned, with expected distractors becoming less interfering. Little is known about the neural mechanism supporting this form of statistical learning. Here we used magnetoencephalography (MEG) to measure human brain activity to test whether proactive mechanisms are involved in the statistical learning of distractor locations. Specifically, we used a new technique called rapid invisible frequency tagging (RIFT) to assess neural excitability in early visual cortex during statistical learning of distractor suppression, while concurrently investigating the modulation of posterior alpha-band activity (8-12 Hz). Male and female human participants performed a visual search task in which a target was occasionally presented alongside a color-singleton distractor. Unbeknown to the participants, the distracting stimuli were presented with different probabilities across the two hemifields. RIFT analysis showed that early visual cortex exhibited reduced neural excitability in the pre-stimulus interval at retinotopic locations associated with higher distractor probabilities. In contrast, we did not find any evidence of expectation-driven distractor suppression in alpha-band activity. These findings indicate that proactive mechanisms of attention are involved in predictive distractor suppression and that these mechanisms are associated with altered neural excitability in early visual cortex. Moreover, our findings indicate that RIFT and alpha-band activity might subtend different and possibly independent attentional mechanisms.

neuroscience↗

bioRxiv2018

Previewing a face in the periphery reduces the fN170: Combined EEG and eye-tracking suggests two stages of trans-saccadic predictive processes

The world appears stable despite saccadic eye-movements. One possible explanation for this phenomenon is that the visual system predicts upcoming input across saccadic eye-movements, based on peripheral preview of the saccadic target. We tested this idea using concurrent electroencephalography (EEG) and eye-tracking. Participants made cued saccades to peripheral upright or inverted face stimuli that could change (invalid preview) or keep their orientation (valid preview) across the saccade. Experiment 1 demonstrated better discrimination performance and a reduced fixation-locked N170 (fN170) with valid than with invalid preview demonstrating integration of pre- and post-saccadic information. Moreover, the early fixation-locked EEG showed a preview face inversion effect suggesting that we perceive pre-saccadic input up to about 170 ms post fixation-onset, at least for face orientation. Experiment 2 replicated Experiment 1 and manipulated the proportion of valid and invalid trials (mostly valid versus mostly invalid, 66.6% to 33.3%) to test whether the preview effect reflected active expectations. A whole-scalp Bayes factor analysis provided evidence for no influence of proportion on the fN170 preview effect. Instead, before the saccade the preview face orientation effect declined earlier in the mostly invalid than in the mostly valid block suggesting some form of pre-saccadic expectations. We conclude that visual stability is achieved by two trans-saccadic integration processes: pre-saccadic prediction, reflected in the pre-saccadic proportion modulation, and early post-saccadic change-detection reflected in the fN170 preview effect.

neuroscience↗

bioRxiv2018

Spatial attention follows category-based attention during naturalistic visual search: evidence from MEG decoding

In daily life, attention is often directed to high-level object attributes, such as when we look out for cars before crossing a road. Previous work used MEG decoding to investigate the influence of such category-based attention on the time course of object category representations. Attended object categories were more strongly represented than unattended categories from 180 ms after scene onset. In the present study, we used a similar approach to determine when, relative to this category-level modulation, attention is spatially focused on the target. Participants completed two tasks. In the first, they detected cars and people at varying locations in photographs of real-world scenes. In the second, they detected a cross that appeared at salient locations in an array of lines. Multivariate classifiers were trained on data of the artificial salience experiment and tested on data of the naturalistic visual search experiment. Results showed that the location of both target and distracter objects could be accurately decoded shortly after scene onset (50 ms). However, the emergence of spatial attentional selection - reflected in better decoding of target location than distracter location - emerged only later in time (240 ms). Target presence itself (irrespective of location and category) could be decoded from 180 ms after stimulus onset. Combined with earlier work, these results indicate that naturalistic category search operates through an initial spatially-global modulation of category processing that then guides attention to the location of the target.

neuroscience↗

bioRxiv2017

Distractor inhibition contributes to retroactive attentional orienting within working memory: Evidence by lateralized event-related parameters of the EEG

Shifts of attention within mental representations based on retroactive cues (retro-cues) facilitate performance in working memory tasks. It was suggested that this retro-cue benefit is related to the concentration of working memory resources on a subset of representations, thereby improving storage and retrieval at the cost of non-cued items. However, the attentional mechanisms underlying this updating of working memory representations remain unknown. Here, we present EEG data for distinguishing between target enhancement and distractor suppression processes in the context of retroactive attentional orienting. Therefore, we used a working memory paradigm with retro-cues indicating a shift of attention to either a lateralized or non-lateralized item. There was an increase of posterior alpha power contralateral compared to ipsilateral to the irrelevant item when a non-lateralized mental representation was cued and a contralateral suppression of posterior alpha power when a lateralized item had to be selected. This suggests that both inhibition of the non-cued information and enhancement of the target representation are important features of attentional orienting within working memory. By further presenting cues to either remember or to forget a working memory representation, we give a first impression of these retroactive attentional sub-processes as two separable cognitive mechanisms.

neuroscience↗