Biology subjects

Smith, P. J. C.

Publications and source records attributed to Smith, P. J. C..

4 recordsLinked to original sources

bioRxiv2026

Spatial attention and lateralized pre-stimulus alpha shape iconic memory via inhibition

The earliest stage of visual memory is often characterized as pre-attentive, yet recent work suggests that spatial attention and pre-stimulus alpha oscillations both shape iconic memory at its onset. Whether these influences reflect a common inhibitory mechanism or contribute independently is unknown. We combined an endogenous spatial pre-cue (valid, invalid, neutral) with an analysis of pre-stimulus alpha power in a partial-report paradigm, at target-to-post-cue onset asynchronies (SOAs) of 0, 120, and 1240 ms, while recording EEG from 45 participants. Behaviorally, perceptual sensitivity (d') showed a cost-dominated signature: invalid cues impaired performance relative to both neutral and valid cues at the 0 and 120 ms SOAs, with no benefit of valid over neutral cues. The pre-stimulus EEG mirrored this asymmetry: at 120 ms, stronger alpha power ipsilateral to the target predicted higher d', whereas contralateral alpha had no effect at any SOA, indicating suppression of the irrelevant hemifield rather than facilitation of the target. This ipsilateral effect was additive with cue validity rather than interactive, and it persisted in neutral trials without any directional cue. Iconic memory is thus continuously biased by the inhibitory state of early visual cortex, to which endogenous attention and spontaneous excitability fluctuations contribute through separable channels. Significance StatementWhether the earliest stage of visual memory depends on attention has long been debated. We show that the same asymmetry with which spatial attention shapes iconic memory--misdirecting attention impairs memory, but correctly directing it yields no benefit--also appears in EEG alpha power. Stronger prestimulus alpha power over the hemisphere ipsilateral to the target improves memory, while activity over the target-processing hemisphere does not. This alpha effect occurs even without any spatial cue, showing that it does not depend on deliberate attention. Because the cue-driven and spontaneous alpha effects add together rather than interact, they reflect two separable routes to the same outcome: suppression of irrelevant input. Early visual memory is thus continuously gated by the inhibitory state of visual cortex.

neuroscience↗

bioRxiv2026

Effects of spatial attention on iconic memory are primarily driven by costs rather than benefits

The role of spatial attention in iconic memory - an early interface between visual perception and short-term memory - remains poorly understood. Across two experiments run in 2025, we investigated how endogenous spatial attention modulates iconic memory using a partial-report paradigm. In both exper-iments, pre-cues manipulated the allocation of spatial attention before stimulus onset. Stimulus arrays were then briefly presented to one hemifield and followed by a post-cue that probed iconic memory at varying delays after stimulus offset. In Experiment 1 (N = 47), valid attentional cues improved perfor-mance at short delays. Performance was modeled with an exponential decay function to dissociate effects on initial stimulus availability at short SOAs, the rate of iconic decay, and later transfer to working mem-ory. This analysis indicated that valid pre-cues increased initial stimulus availability relative to invalid pre-cues. In Experiment 2 (N = 66), a neutral pre-cue condition was added, and post-cues were pre-sented at three delays (0, 120, and 1240 ms). This revealed that performance differences were driven by attentional costs at invalidly cued locations, with no detectable benefits at validly cued locations relative to neutral cues. Together, these results show that spatial attention modulates the earliest measurable phase of iconic memory by shaping the initial sensory trace. The cost-dominated pattern suggests that attention primarily suppresses information at unattended locations rather than enhancing representa-tions at attended locations. This finding challenges the view of iconic memory as a pre-attentive sensory store and indicates that attentional selection operates earlier than previously assumed. Significance StatementThe influence of attention on iconic memory - a high-capacity, ultra-brief sensory store - remains highly debated. We demonstrate that endogenous spatial attention modulates iconic memory at its earliest measurable stage. Critically, this modulation reflects an attentional cost at unattended locations rather than a benefit at attended locations, suggesting that spatial attention acts through inhibitory suppression of irrelevant sensory input. These findings challenge models proposing that early sensory representation is categorically attention-free and establish a suppressive role for attention in shaping visual short-term memory at its earliest stage.

neuroscience↗

bioRxiv2025

Pre-stimulus pupil-linked arousal enhances initial stimulus availability and accelerates decay in iconic memory.

Pupil diameter reflects not only reflexive responses to light but also spontaneous fluctuations in arousal. Such pre-stimulus fluctuations may shape visual performance, yet it remains unclear whether they only affect perceptual sensitivity or decision processes in near-threshold tasks, or instead influence the temporal availability of sensory information even for highly visible stimuli. We tested whether pupil-linked arousal modulates iconic memory, a high-capacity but short-lived visual store bridging sensory encoding and short-term memory. Based on a model in which a brief stimulus evokes an internal response decaying over a few hundred milliseconds, we hypothesized that increased arousal enhances performance either by amplifying the initial response or by slowing its decay. Thirty-seven participants viewed brief displays of six oriented stimuli, followed by a cue after a variable stimulus-cue onset asynchrony indicating which item to report. Pre-stimulus pupil diameter was continuously recorded, and behavioral data were fitted with an exponential decay function estimating initial stimulus availability, decay rate, and asymptotic performance. Larger pre-stimulus pupil dilation was associated with higher initial stimulus availability but faster decay of the iconic trace, while information transferred into short-term memory and confidence ratings remained unaffected. These findings demonstrate that spontaneous fluctuations in arousal shape the temporal dynamics of sensory persistence. Elevated arousal boosts the initial strength of visual representations but shortens their duration, suggesting that arousal adaptively prioritizes rapid updating of visual input over prolonged stability. Significance StatementHow does arousal shape the earliest stages of visual memory? By leveraging a criterion-free partialreport task that emphasizes the temporal availability of sensory information, we show that spontaneous pre-stimulus pupil dilation - an index of arousal - selectively boosts the initial availability of iconic memory while accelerating its decay. This dual effect suggests that arousal tunes the temporal dynamics of sensory persistence, potentially prioritizing rapid updating of incoming information. These findings advance the understanding of how state-dependent fluctuations in arousal shape early perception in a context that minimizes decision-bias confounds.

neuroscience↗

bioRxiv2024

Spontaneous alpha-band lateralization extends persistence of visual information in iconic memory by modulating cortical excitability.

Pre-stimulus alpha oscillations in the visual cortex modulate neuronal excitability, influencing sensory processing and decision-making. While this relationship has been demonstrated mostly in detection tasks with low-visibility stimuli, interpretations of such effects can be ambiguous due to biases, making it difficult to clearly distinguish between perception-related and decision-related effects. In this study, we investigated how spontaneous fluctuations in pre-stimulus alpha power affect iconic memory, a high-capacity, ultra-short visual memory store. Data from 49 healthy adults (34 female and 15 male) was analyzed. We employed a partial report task, where a brief display of six stimuli was followed by a report cue indicating the target stimulus. In this paradigm, accuracy at short stimulus-cue onset asynchronies (SOAs) is typically high, reflecting the initial availability of sensory information, but it rapidly declines at intermediate SOAs due to the decay of the iconic memory trace, stabilizing at a low asymptote at long SOAs, representing the limited capacity of short-term memory. Crucially, performance in this task is constrained by the temporal persistence of sensory information, not by low visibility or response bias. We found that strong pre-stimulus alpha power enhanced performance by amplifying initial stimulus availability without affecting the speed of iconic decay. This effect was driven predominantly by stronger pre-stimulus alpha power in the hemisphere ipsilateral to the to-be-reported target, likely suppressing neuronal excitability of neurons coding irrelevant stimuli. Our findings underscore the role of alpha oscillations in modulating neuronal excitability and visual perception, independent of decision-making strategies implicated in prior studies.

neuroscience↗