Biology subjects

Woodman, G. F.

Publications and source records attributed to Woodman, G. F..

10 recordsLinked to original sources

bioRxiv2025

Sensory Neural Noise as a Limiting Factor in Visual Working Memory Precision in Neurotypicals and Schizophrenia

The neural mechanisms that determine the capacity limits of working memory (WM) are not well understood, with traditional views identifying prefrontal circuitry as the main source of WM limits. Sensory noise, however, remains an underexplored explanation for WM limits despite its unavoidable influence on brain systems that encode and relay sensory information. Here, we show that individual differences in internal sensory noise during visual processing predict visual WM capacity. We further demonstrate that the well-documented WM deficits observed in schizophrenia can be associated with atypically high levels of visual sensory noise, offering a new explanatory framework for these deficits. By experimentally manipulating sensory noise via transcranial direct current stimulation applied to the visual cortex, we also show that changes in sensory noise led to corresponding changes in visual WM precision in individuals with schizophrenia. Finally, a computational model demonstrates that the same sensory noise measured during visual perception can limit WM precision during WM maintenance. These findings show that sensory noise may explain a significant amount of variance in WM function in both neurotypical adults and individuals with schizophrenia.

neuroscience↗

bioRxiv2025

What is memorable across the Pacific Ocean shows evidence of prior learning on the memorability of new visual inputs

It has been proposed that certain objects in our environment are inherently memorable due to fundamental similarities in how the human brain stores this visual information. Here we tested this hypothesis by having two groups of participants from opposite sides of the planet remember pictures of objects shown individually from several seconds each. We found that the specific objects that were more memorable varied across groups, with fine-grained analysis of the nonoverlapping objects indicating that participants have greater facility storing objects that are familiar to them as they occur in their cultural context. Thus, the present findings demonstrate that the memorability of a stimulus is jointly determined by its features and the learning history of the human brain in which it is being stored.

animal behavior and cognition↗

bioRxiv2025

Salient objects in a scene trigger enhanced perceptual selection and memory encoding

Rapidly detecting salient objects from surrounding environments is crucial for survival. Our study demonstrates that salient objects in visual search arrays trigger von Restorff-like effects. In a search task, participants detected a tilted target bar among distractors with EEG recordings. The results revealed that salient objects elicited the largest and earliest N2pc component, reflecting early attentional selection, which enhanced multivariate decoding of target location. Importantly, early selection of highly salient targets (25{degrees} tilt) triggered a cascade of preferential processing downstream, marked by stronger P3b components, neural synchronization, and phase-amplitude coupling between low- and high-frequency activity, along with better recall performance of target orientation. The strength of memory-related activity on the current trial predicted the vigor of the next selection event, indicating that salience-driven learning influences future attentional control. Overall, object salience in spatial arrays drives a cascade of processing, facilitating rapid learning of object relevance while humans search their environment, similar to the classic demonstrations of the von Restorff effect, except the objects are distributed in space rather than time.

neuroscience↗

bioRxiv2024

Executive control can query hidden human memories

When we try to retrieve a representation from visual long-term memory there is a chance that we will fail to recall seeing it even though the memory is stored in our brain. Here we show that although mechanisms of explicit memory retrieval are sometimes unable to retrieve stored memories, that mechanisms of executive control can quickly query memory and determine if a representation is stored therein. Our findings suggest that the representations stored in human memory that cannot be accessed explicitly at that moment are nonetheless directly accessible by the brains higher level control mechanisms.

neuroscience↗

bioRxiv2022

Cortical Contributions to Medial Frontal β-Bursts during Executive Control

EEG {beta}-bursts observed over the medial frontal cortex are claimed to mediate response inhibition despite their infrequent occurrence. The weak association with stopping behavior is supposed to be a by-product of the low signal-to-noise ratio of EEG recordings. We tested the premise that {beta}-bursts are more common within the cerebral cortex and more directly associated with response inhibition. We sampled simultaneously EEG and intracortical local field potentials (LFP) within the medial frontal cortex (MFC) of two macaque monkeys performing a response inhibition task. Intracortical {beta}-bursts were just as infrequent as those in EEG and did not parallel the likelihood of canceling a planned response. Cortical {beta}-bursts were more prevalent in upper layers but were not synchronized across a cortical column or with EEG {beta}-bursts. These findings contradict claims for a causal contribution of {beta}-bursts during response inhibition, provide important constraints for biophysical and cortical circuit models, and invite further considerations of {beta}-burst function in cognitive control.

neuroscience↗

bioRxiv2022

Feedforward attentional selection in sensory cortex

Salient objects stand out (pop-out) from their surroundings, grabbing our attention. Whether this phenomenon is a consequence of bottom-up sensory processing or predicated on top-down influence is debated. We show that the neural computation of attentional pop-out is embedded in the earliest cortical sensory response, seemingly void of feedback from higher-level areas. We measured synaptic and spiking activity across cortical columns in mid-level area V4 of monkeys searching for an attention-grabbing stimulus. Indexed by reaction times and behavioral accuracy, attention was captured at variable times. This moment of attentional capture occurred within the earliest feedforward response, both in terms of timing and spatial location. Moreover, the magnitude of the earliest sensory response predicted reaction times. Crucially, errant attentional selection and consequent behavior was associated with errant selection in sensory cortex. Together, these findings demonstrate a dominant role for feedforward activation of sensory cortex for dictating attentional priority and subsequent behavior. In briefWhy do certain objects stand out from their surroundings and seemingly grab our attention? In this study, Westerberg et al. determine that attentional selection for salient objects in our environment is computed in sensory cortex as soon as sensory information arrives. HighlightsO_LIEarly sensory responses in V4 predict attentional selection and behavioral responses C_LIO_LIErrant attentional selection in sensory cortex precedes errant behavior C_LIO_LITonic modulation of sensory cortex can regulate attentional selection C_LI

neuroscience↗

bioRxiv2022

Resolving the mesoscopic missing link: Biophysical modeling of EEG from cortical columns in primates

Event-related potentials (ERP) are among the most widely measured indices for studying human cognition. While their timing and magnitude provide valuable insights, their usefulness is limited by our understanding of their neural generators at the circuit level. Inverse source localization offers insights into such generators, but their solutions are not unique. To address this problem, scientists have assumed the source space generating such signals comprises a set of discrete equivalent current dipoles, representing the activity of small cortical regions. Based on this notion, theoretical studies have employed forward modeling of scalp potentials to understand how changes in circuit-level dynamics translate into macroscopic ERPs. However, experimental validation is lacking because it requires in vivo measurements of intracranial brain sources. Laminar local field potentials (LFP) offer a mechanism for estimating intracranial current sources. Yet, a theoretical link between LFPs and intracranial brain sources is missing. Here, we present a forward modeling approach for estimating mesoscopic intracranial brain sources from LFPs and predict their contribution to macroscopic ERPs. We evaluate the accuracy of this LFP-based representation of brain sources utilizing synthetic laminar neurophysiological measurements and then demonstrate the power of the approach in vivo to clarify the source of a representative cognitive ERP component. To that end, LFP was measured across the cortical layers of visual area V4 in macaque monkeys performing an attention demanding task. We show that area V4 generates dipoles through layer-specific transsynaptic currents that biophysically recapitulate the ERP component through the detailed forward modeling. The constraints imposed on EEG production by this method also revealed an important dissociation between computational and biophysical contributors. As such, this approach represents an important bridge from the mesoscopic activity of cortical columns to the patterns of EEG we measure at the scalp. HighlightsO_LICognitive EEG production was accurately modeled from empirically measured cortical activity in awake macaques. C_LIO_LIV4 laminar activity plausibly generates the attention-related signal indexed by the EEG. C_LIO_LIModels demonstrate the importance of biophysical geometry in cognitive EEG production. C_LI

neuroscience↗

bioRxiv2020

Dissociation of Medial Frontal β-Bursts and Executive Control

The neural mechanisms of executive and motor control concern both basic researchers and clinicians. In human studies, preparation and cancellation of movements are accompanied by changes in the {beta}-frequency band (15-29 Hz) of EEG. Previous studies with human participants performing stop signal (countermanding) tasks have described reduced frequency of transient {beta}-bursts over sensorimotor cortical areas before movement initiation and increased {beta}-bursting over medial frontal areas with movement cancellation. This modulation has been interpreted as contributing to the trial-by-trial control of behavior. We performed identical analyses of EEG recorded over the frontal lobe of macaque monkeys performing a saccade countermanding task. Whilst, we replicate the occurrence and modulation of {beta}-bursts associated with initiation and cancellation of saccades, we found that {beta}-bursts occur too infrequently to account for the observed stopping behavior. We also found {beta}-bursts were more common after errors, but their incidence was unrelated to response time adaptation. These results demonstrate the homology of this EEG signature between humans and macaques but raise questions about the current interpretation of {beta}-band functional significance.

neuroscience↗

bioRxiv2020

A Minimal Biophysical Model of Neocortical Pyramidal Cells: Implications for Frontal Cortex Microcircuitry and Field Potential Generation

Ca2+ spikes initiated in the apical dendrites of layer-5 pyramidal cells (PC) underlie nonlinear dynamic changes in the gain of cellular response, which is critical for top-down cognitive control. Detailed models with several compartments and dozens of ionic channels have been proposed to account for this Ca2+ spike-dependent gain with its associated critical frequency. However, current models do not account for all known Ca2+-dependent features. Previous attempts to include more features have required increasing complexity, limiting their interpretability and utility for studying large population dynamics. We present a minimal 2-compartment biophysical model, overcoming these limitations. In our model, a basal-dendritic/somatic compartment included typical Na+ and K+ conductances, while an apical-dendritic/trunk compartment included persistent Na+, hyperpolarization-activated cation (Ih), slow inactivation K+, muscarinic K+, and Ca2+ L-type. The model replicated the Ca2+ spike morphology and its critical frequency plus three other defining features of layer-5 PC synaptic integration: linear frequency-current relationships, backpropagation-activated Ca2+ spike firing, and a shift in the critical frequency by blocking Ih. Simulating 1,000 synchronized layer-5 PCs, we reproduced the current source density patterns evoked by Ca2+-spikes both with and without Ih current. Thus, a 2-compartment model with five non-classic ionic currents in the apical-dendrites reproduces all features of these neurons. We discuss the utility of this minimal model to study the microcircuitry of agranular areas of the frontal lobe involved in cognitive control and responsible for event-related potentials such as the error-related negativity. Significance StatementA tractable model of layer-5 pyramidal cells replicates all known features crucial for distal synaptic integration in these neurons. This minimal model enables new multi-scale investigations of microcircuit functions with associated current flows measured by intracranial local field potentials. It thus establishes a foundation for the future computational evaluation of scalp electroencephalogram signatures imprinted by Ca2+ spikes in pyramidal cells, a phenomenon underlying many brain cognitive processes.

neuroscience↗

bioRxiv2018

Context triggers the retrieval of long-term memories into working memory to guide attention

How do we know what we are looking for in familiar scenes and surroundings? Here we tested a novel hypothesis derived from theories of human memory that working memory (WM) buffers mnemonic contents retrieved from long-term memory (LTM) to control attention. To test this hypothesis, we measured the electrical fields recorded noninvasively from human subjects as they searched for specific sets of objects in learned contexts. We found that the subjects WM-indexing brain activity tracked the number of real-world objects people learned to search for in each context. Moreover, the level of this WM activity predicted the inter-subject variability in behavioral performance. Together, our results demonstrate that familiar contexts can trigger the transfer of information from LTM to WM to provide top-down attentional control.

neuroscience↗