Biology subjects

Swallow, K. M.

Publications and source records attributed to Swallow, K. M..

5 recordsLinked to original sources

bioRxiv2026

Attention modulates EEG spectral activity across serial positions

Electroencephalographic (EEG) activity has been associated with attentional processes such as task-irrelevant stimulus suppression and orienting. The aim of this study was to understand how spectral activity evolves as words are presented in a word list learning task and as multiple components of attention are engaged under multitasking demands. We recorded scalp EEG in a delayed free-recall task in which participants encoded common noun word lists either under full attention (encoding only) or divided attention (simultaneous target detection task). In the target detection task, participants pressed a response button when a word was paired with a target-colored square but not for words paired with a distractor-colored square (cue condition). Activity in the high gamma frequencies (50-100 Hz) decreased while alpha activity (8-12 Hz) increased throughout word list presentation (i.e., across serial positions), consistent with prior work demonstrating effects of cognitive load on EEG spectral power. Divided attention attenuated this change in gamma power across the list. Cue condition modulated alpha activity evenly across serial positions, with consistently lower power during target trials than distractor trials. Our findings suggest that frequency-specific characteristics of processing during list encoding may reflect multiple components of attention that vary over different time scales. Gamma frequencies capture the interactive effects of cognitive load and dual-task demands, while alpha power separately reflects gradual increases in cognitive load and momentary orienting.

neuroscience↗

bioRxiv2023

Locus coeruleus neuromelanin accumulation and dissipation across the lifespan

The pigment neuromelanin, produced in the locus coeruleus (LC) as a byproduct of catecholamine synthesis, gives the "blue spot" its name, and both identifies LC neurons and is thought to play an important yet complex role in normal and pathological aging. Using neuromelanin-sensitive T1-weighted turbo spin echo MRI scans we characterized volume and neuromelanin signal intensity in the LC of 96 participants between the ages of 19 and 86. Although LC volume did not change significantly throughout the lifespan, LC neuromelanin signal intensity increased from early adulthood, peaked around age 60 and precipitously declined thereafter. Neuromelanin intensity was greater in the caudal relative to rostral extent and in women relative to men. With regard to function, rostral LC neuromelanin intensity was associated with fluid cognition in older adults (60+) only in those above the 50th percentile of cognitive ability for age. The gradual accumulation of LC neuromelanin across the lifespan, its sudden dissipation in later life, and relation to preserved cognitive function, is consistent with its complex role in normal and pathological aging.

neuroscience↗

bioRxiv2023

Temporal Attention Modulates EEG Spectral Correlates of Successful Memory Encoding

The current study investigates whether changes in scalp electroencephalographic (EEG) activity over time reflect the effects of target detection and divided attention on memory encoding. We recorded EEG activity in 61 young adults as they memorized lists of words either under full attention (single-task) or while performing a secondary task (dual-task). In both cases, colored squares appeared with each word. However, in the dual-task condition participants also pressed a button when the colored squares were in a predefined color (target) but made no response when the squares were in a different color (distractor). Subsequent memory effects in the alpha (8-12 Hz) and high gamma (50-100 Hz) frequency bands changed throughout the trial, and these effects differed across conditions. Prior to word presentation, high gamma activity was associated with encoding success in the target and single-task conditions, but not in the distractor conditions. In contrast, alpha band activity decreased following word presentation, and these decreases were greater for successfully encoded words in the target condition than in the distractor or single-task conditions. The results are consistent with the view that alpha and gamma activity reflect distinct neural processes which both contribute to memory formation, but are differentially sensitive to task demands and momentary shifts in attention.

neuroscience↗

bioRxiv2020

Auditory Target Detection Enhances Visual Processing and Hippocampal Functional Connectivity

Though dividing ones attention between two input streams typically impairs performance, detecting a behaviorally relevant stimulus can sometimes enhance the encoding of unrelated information presented at the same time. Previous research has shown that selection of this kind boosts visual cortical activity and memory for concurrent items. An important unanswered question is whether such effects are reflected in processing quality and functional connectivity in visual regions and in the hippocampus. In this fMRI study, participants were asked to memorize a stream of naturalistic images and press a button only when they heard a predefined target tone (400 or 1200 Hz, counterbalanced). Images could be presented with a target tone, with a distractor tone, or without a tone. Auditory target detection increased activity throughout the ventral visual cortex but lowered it in the hippocampus. Enhancements in functional connectivity between the ventral visual cortex and the hippocampus were also observed following auditory targets. Multi-voxel pattern classification of image category was more accurate on target tone trials than on distractor and no tone trials in the fusiform gyrus and parahippocampal gyrus. This effect was stronger in visual cortical clusters whose activity was more correlated with the hippocampus on target tone than on distractor tone trials. In agreement with accounts suggesting that subcortical noradrenergic influences play a role in the attentional boost effect, auditory target detection also caused an increase in locus coeruleus activity and phasic pupil responses. These findings outline a network of cortical and subcortical regions that are involved in the selection and processing of information presented at behaviorally relevant moments.

neuroscience↗

bioRxiv2019

Estimates of locus coeruleus function with functional magnetic resonance imaging are influenced by localization approaches and the use of multi-echo data

The locus coeruleus (LC) plays a central role in regulating human cognition, arousal, and autonomic states. Efforts to characterize the LCs function in humans using functional magnetic resonance imaging have been hampered by its small size and location near a large source of noise, the fourth ventricle. We tested whether the ability to characterize LC function is improved by employing neuromelanin-T1 weighted images (nmT1) for LC localization and multi-echo functional magnetic resonance imaging (ME-fMRI) for estimating intrinsic functional connectivity (iFC). Analyses indicated that, relative to a probabilistic atlas, utilizing nmT1 images to individually localize the LC increases the specificity of seed time series and clusters in the iFC maps. When combined with independent components analysis (ME-ICA), ME-fMRI data provided significant gains in the temporal signal to noise ratio relative to denoised single-echo (1E) data. The effects of acquiring nmT1 images and ME-fMRI data did not appear to only reflect increases in power: iFC maps for each approach only moderately overlapped. This is consistent with findings that ME-fMRI offers substantial advantages over 1E data acquisition and denoising. It also suggests that individually identifying LC with nmT1 scans is likely to reduce the influence of other nearby brainstem regions on estimates of LC function.\n\nHighlightsO_LIManual tracing of locus coeruleus increased specificity of seed time series\nC_LIO_LIManual tracing of locus coeruleus increased specificity of intrinsic connectivity\nC_LIO_LIMulti-echo fMRI increased temporal signal-to-noise ratio compared to single-echo fMRI\nC_LIO_LIConnectivity maps across methodologies overlapped only moderately\nC_LIO_LIMeasurement of LC function benefits from multi-echo fMRI and tracing ROIs\nC_LI

neuroscience↗