Biology subjects

Rushworth, M. F.

Publications and source records attributed to Rushworth, M. F..

18 recordsLinked to original sources

bioRxiv2026

Ultrasound-mediated focal serotonin delivery causally modulates motivation in primates

Causal manipulation of neuromodulatory systems has been constrained by a trade-off between spatial precision and translational relevance: circuit-specific techniques are invasive, whereas systemic pharmacology lacks anatomical specificity. Here, we establish ultrasound-mediated neuromodulator delivery as a non-invasive, spatially precise approach for causal neuropharmacology in awake, behaving primates. By transiently opening the blood-brain barrier, we delivered systemically administered serotonin to the perigenual anterior cingulate cortex (pgACC) during a decision-making task. Combining computational modelling with multimodal imaging, pupillometry and histology, we show that elevating pgACC serotonin altered local neural activity and weakened the influence of reward environment on motivational state while leaving sensitivity to immediate reward opportunities intact. This was accompanied by reduced functional coupling, decreased local glutamatergic metabolite signal and increased serotonergic signal at the target, with repeated delivery well tolerated. Together, these findings establish a translatable platform for focal neuropharmacology and identify pgACC serotonin as a regulator of context-dependent motivation.

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bioRxiv2025

Low-intensity focused ultrasound to human amygdala reveals a causal role in ambiguous emotion processing and alters local and network-level activity

The amygdala is a core region changed in depression, a disorder characterized by compromised emotion, motivation and learning processes. However, lesion studies in humans examining amygdala function have largely focused on its role in processing fear. It currently remains unclear what causal role the human amygdala plays in more complex emotion, motivation and learning processes in daily life. This is because it has not been possible to reversibly modulate amygdala activity non-invasively in humans. Here, we used transcranial focused ultrasound stimulation (TUS) to bilaterally perturb neural activity in the basolateral amygdala (BLA). In separate sessions (n = 87), 29 healthy volunteers received offline-TUS to bilateral BLA, mid-insula or sham before playing a novel emotional learning task validated in an independent large cohort online (n = 210). 7T-resting-state and metabolite signals clearly demonstrated target engagement. BLA-TUS reduced the BLAs connectivity fingerprint and decreased its excitation/inhibition balance, suggesting an inhibitory effect of our TUS protocol on BLA activity. In behaviour, BLA-TUS caused a stimulation volume-dependent increase in the tendency to approach neutral, emotionally ambiguous faces, treating them more similarly to happy faces, and a slowing of reaction times for those two emotion categories. These effects were functionally and regionally specific and suggest a causal role for the amygdala in resolving emotional ambiguity. Our results provide important insights for future studies into mood disorders where ambiguous situations might be harder to resolve, which could contribute to existing emotional and learning biases.

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bioRxiv2025

Interpretable abstractions of artificial neural networks predict behavior and neural activity during human information gathering

It has been suggested that humans and other animals are driven by a fundamental desire to acquire information about opportunities available in their environments. Not only might such a desire explain pathological behaviors, but it may be needed to account for how everyday decisions are resolved. Here, we combine artificial neural networks (ANNs) with symbolic regression to extract an expressive yet interpretable model that specifies how human participants evaluate decision-relevant information during choice. This model accounts for behavior in our own data and in previous work, outperforming existing accounts of information sampling such as the Upper Confidence Bound heuristic. This modelling approach has broad potential for uncovering novel patterns in behavior and cognitive processes, while also specifying them in human-interpretable formats. We then used the value of information derived by our model, together with ultra-high field neuroimaging, to examine activity across a suite of subcortical neuromodulatory nuclei and two cortical regions that influence these nuclei. This established roles for midbrain dopaminergic nuclei, anterior cingulate cortex, and anterior insula in mediating the influence of value of information on behavior.

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bioRxiv2025

Identifying mood instability and circadian rest-activity patterns using digital remote monitoring and actigraphy in participants at risk for bipolar disorder

Mood instability and circadian rhythm disruptions are both of increasing interest with regard to a number of psychiatric disorders, notably bipolar disorder (BD), but understanding of their nature and their interrelationship are incomplete. By definition, both have an integral temporal component and, as such, measuring them longitudinally and remotely is desirable. We conducted the Cognition and Mood Evolution across Time (COMET) study to assess the feasibility and value of digital devices to capture mood, its instability, and daily rest-activity patterns, over a 10-week period, in two groups of participants. The first group (n=37) were selected as scoring >7 on the Mood Disorder Questionnaire (MDQ) ( high MDQ), thereby having a history of mood elevation and being at risk for BD. They were compared with a group (n=37) scoring <5 on the MDQ ( low MDQ). Over a 10-week period, using a tablet, mood was rated daily, clinical ratings of depression, mania, and anxiety were captured weekly via the True Colours app, and a GENEactiv actigraph was worn to capture rest-activity pattern data. The main findings are that (1) MDQ score predicts mood instability; (2) high MDQ score is associated with more negative affect and mood symptoms than people with low MDQ, and with a different circadian activity profile; and (3) mood instability and circadian indices appear uncorrelated. The implications are that (1) remote monitoring of these domains is feasible and valuable; (2) selection of participants based on MDQ score is useful for studying mood (in)stability; and (3) the approach has potential for studies of clinical populations and for experimental medicine studies assessing interventions to reduce mood instability.

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bioRxiv2025

ACTIVITY IN HUMAN DORSAL RAPHE NUCLEUS SIGNALS CHANGES IN BEHAVIOURAL POLICY

The dorsal raphe nucleus (DRN) is an important source of serotonin to the human forebrain, however there is little consensus about its behavioural function. We build on recent results from animal models to demonstrate that activity in human DRN represents changes between general behavioural policies. We use a novel behavioural task to show that human participants change their policy to pursue or reject reward opportunities as a function of the average value of opportunities in the environment. Activity in DRN - but no other neuromodulatory nucleus - signalled such policy changes. Patterns of multivariate activity in dorsal anterior cingulate cortex (dACC) and anterior insular cortex (AI), meanwhile, tracked the relative value of reward opportunities given the average value of the environment. We therefore suggest that DRN, dACC and AI form a circuit in which dACC/AI compute the relative value of reward opportunities given the current context, and DRN implements changes in behavioural policy based on context-specific values.

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bioRxiv2024

Non-invasive Ultrasound Deep Neuromodulation of the Human Nucleus Accumbens Increases Win-Stay Behaviour

Precisely neuromodulating deep brain regions could bring transformative advancements in both neuroscience and treatment. We demonstrate that non-invasive transcranial ultrasound stimulation (TUS) can selectively modulate deep brain activity and affect learning and decision making, comparable to deep brain stimulation (DBS). We tested whether TUS could causally influence neural and behavioural responses by targeting the nucleus accumbens (NAcc) using a reinforcement learning task. Twenty-six healthy adults completed a within-subject TUS-fMRI experiment with three conditions: TUS to the NAcc, dorsal anterior cingulate cortex (dACC), or Sham. After TUS, participants performed a probabilistic learning task during fMRI. TUS-NAcc altered BOLD responses to reward signals in the NAcc and surrounding areas. It also affected reward-related features, including win-stay strategy use, learning rate following rewards and learning curves. DBS-NAcc perturbed the same features, confirming target engagement. These findings establish TUS as a viable approach for non-invasive deep-brain neuromodulation.

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bioRxiv2023

An ancient subcortical circuit decides when to orient to threat in humans

Many psychiatric symptoms have been linked to threat-related perception and learning processes. In addition, however, there may also be mechanisms for balancing effectively between threat- and reward-related behaviors and these may also vary between individuals. We investigated neural activity associated with spontaneous switching between foraging for rewards and vigilance for threats with 7T fMRI. In a virtual naturalistic environment, participants freely switched between the two modes of behavior. Switching was driven by estimates of likelihood of threat and reward. Both tracking of threat and switching to vigilance were associated with specific but distributed patterns of activity spanning habenula, dorsal raphe nucleus (DRN), anterior cingulate cortex, and anterior insula cortex. Distinct distributed patterns heralded returns to reward-oriented behavior. Individual variation in DRN activity reflected individual variation in vigilance. All activity patterns were replicated in an initially held-out portion of data.

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bioRxiv2022

Timing along the cardiac cycle modulates neural signals of reward-based learning

Natural fluctuations in cardiac activity influence brain activity associated with sensory stimuli and affect perceptual decisions about low magnitude, near-threshold stimuli. However, little is known about the impact of fluctuations in heart activity on other internal representations. Here we investigate cardiac influences on learning-related internal representations - absolute and signed prediction errors. By combining machine learning techniques with electroencephalography (EEG) and both simple, direct indices of task performance and computational model-derived indices of learning, we demonstrate that just as people are more sensitive to low magnitude, near threshold sensory stimuli in certain cardiac phases, so are they more sensitive to low magnitude absolute prediction errors in the same cycles. Importantly, however, this occurs even when the low magnitude prediction errors are associated with clearly suprathreshold sensory events. In addition, participants exhibiting stronger difference in their prediction errors representations between cardiac cycles exhibited higher learning rates and greater task accuracy.

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bioRxiv2022

Hebbian activity-dependent plasticity in white matter

Synaptic plasticity is required for learning and follows Hebbs Rule, the com-putational principle underpinning associative learning. In recent years, a complementary type of brain plasticity has been identified in myelinated axons, which make up the majority of brains white matter. Like synaptic plasticity, myelin plasticity is required for learning, but it is unclear whether it is Hebbian or whether it follows different rules. Here, we provide evidence that white matter plasticity operates following Hebbs Rule in humans. Across two experiments, we find that co-stimulating cortical areas to induce Hebbian plasticity leads to relative increases in cortical excitability and associated increases in a myelin marker within the stimulated fiber bundle. We conclude that Hebbian plasticity extends beyond synaptic changes, and can be observed in human white matter fibers.

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bioRxiv2021

Social prediction modulates activity of macaque superior temporal cortex

The ability to attribute thoughts to others, also called theory of mind (TOM), has been extensively studied. Computationally, the basis of TOM in humans has been interpreted within the predictive coding framework and associated with activity in the temporo-parietal junction (TPJ). However, the evolutionary origins of these human mindreading abilities have been challenged since the concept was coined. Here we identify a brain region in the Rhesus macaque that shares computational properties with the human TPJ. We revealed, using a non-linguistic task and functional magnetic resonance imaging, that activity in a region of the macaque middle superior temporal cortex was specifically modulated by the predictability of social interactions. As in human TPJ, this region could be distinguished from other temporal regions involved in face processing. Our result suggests the existence of a precursor for the theory of mind ability in the last common ancestor of human and old-world monkeys.

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bioRxiv2020

Entraining corticocortical plasticity changes oscillatory activity in action control and inhibition

Oscillatory activity may reflect interactions between brain areas[1]. Here we tested whether inducing corticocortical plasticity in a specific set of connections changes oscillatory activity and cortico-cortical interactions and, if this is the case, whether the changes manifest in a manner that is behaviour state-dependent. We either increased or decreased the influence of activity in human ventral premotor cortex (PMv) over activity in primary motor cortex (M1) using cortico-cortical paired associative stimulation (ccPAS)[2, 3]. Before and after stimulation participants performed a Go/No-Go task. While M1 TMS pulses revealed the excitatory state of the motor system at specific time points, the electroencephalogram (EEG) revealed the evolution of oscillatory activity dynamics in the motor system over several hundreds of milliseconds before, during, and after each movement. Augmenting cortical connectivity between PMv and M1, by evoking synchronous pre- and postsynaptic activity in the PMv-M1 pathways, led to a state-dependent modulation of the causal influence of PMv over M1, and at the same time, enhanced oscillatory beta and theta rhythms in Go and No-Go trials, respectively. No changes were observed in the alpha rhythm. The plasticity induction effect was dependent on PMv-M1 stimulation order; the opposite patterns of results were observed after an equal amount of stimulation of PMv and M1 but applied in a temporal pattern that did not augment PMvs influence over M1. These results are consistent with Hebbian principles of synaptic plasticity[4] and show that artificial manipulation of cortico-cortical connectivity produces state-dependent functional changes in the spectral fingerprints of the motor circuit.

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bioRxiv2020

Perceived ambiguity of social interactions increases coupling between frontal and temporal nodes of the social brain

Social behaviour is coordinated by a network of brain regions, including those involved in the perception of social stimuli and those involved in complex functions like inferring perceptual and mental states and controlling social interactions. The properties and function of many of these regions in isolation is relatively well understood but little is known about how these regions interact whilst processing dynamic social interactions. To investigate whether social network connectivity is modulated by social context we collected fMRI data from monkeys viewing "affiliative", "aggressive", or "ambiguous" social interactions. We show activation relating to the perception of social interactions along both banks of the superior temporal sulcus, parietal, medial and lateral PFC and caudate nucleus. Within this network we demonstrate that fronto-temporal connectivity are significantly modulated by social context. Crucially, we link the observation of specific behaviours to changes in connectivity within our network. Viewing aggressive or affiliative behaviour was associated with a limited increase in temporo-temporal and premotor-temporal connectivity respectively. By contrast, viewing ambiguous interactions was associated with a pronounced increase in cingulate-cingulate, temporo-temporal, and cingulate-temporal connectivity. We hypothesise that this widespread network synchronisation occurs when cingulate and temporal areas coordinate their activity when more difficult social inferences are made.

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bioRxiv2020

Anatomically precise relationship between specific amygdala connections and selective markers of mental well-being in humans

There has been increasing interest in using neuroimaging measures to predict psychiatric disorders. However, predictions usually rely on large numbers of brain connections and large disorder heterogeneity, thus lacking both anatomical and behavioural specificity, preventing the advancement of targeted interventions. Here, we address both challenges. First, using resting-state functional MRI, we parcellated the amygdala, a region implicated in mood disorders but difficult to image with high fidelity, into seven nuclei. Next, a questionnaire factor analysis provided four sub-clinical latent behaviours frequently found in anxious-depressive individuals, such as negative emotions and sleep problems. Finally, for each latent behaviour, we identified the most predictive connections between individual amygdala nuclei and highly specific regions of interest e.g. dorsal raphe nucleus in the brainstem or medial prefrontal cortical regions. A small number of distinct connections predicted behaviours, providing unprecedented levels of specificity, in humans, for relating mental well-being to precise anatomical connections.

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bioRxiv2020

Differential functional connectivity underlying asymmetric reward-related activity in human and non-human primates

The orbitofrontal cortex (OFC) is a key brain region involved in complex cognitive functions such as reward processing and decision-making. Neuroimaging studies have shown unilateral OFC response to reward-related variables, however, those studies rarely discussed the lateralization of this effect. Yet, some lesion studies suggest that the left and right OFC contribute differently to cognitive processes. We hypothesized that the OFC asymmetrical response to reward could reflect underlying hemispherical difference in OFC functional connectivity. Using restingstate and reward-related MRI data from humans and from rhesus macaques, we first identified a specific asymmetrical response of the lateral OFC to reward in both species. Crucially, the subregion showing the highest reward-related asymmetry (RRA) overlapped with the region showing the highest functional connectivity asymmetry (FCA). Furthermore, the two types of functional asymmetries were found to be significantly correlated across humans. Altogether, our results suggest a similar pattern of functional specialization between the left and right OFC is present in two primate species.

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bioRxiv2019

Previously reward-associated stimuli capture spatial attention in the absence of changes in the corresponding sensory representations as measured with MEG

Studies of selective attention typically consider the role of task goals or physical salience, but recent work has shown that attention can also be captured by previously reward-associated stimuli, even if they are currently task-irrelevant. One theory underlying this value-driven attentional capture (VDAC) is that reward-associated stimulus representations may undergo plasticity in sensory cortex, thereby automatically capturing attention during early processing. To test this, we used magnetoencephalography to probe whether stimulus location and identity representations in sensory cortex are modulated by reward learning. We furthermore investigated the time-course of these neural effects, and their relationship to behavioural VDAC. Male and female human participants first learned stimulus-reward associations. Next, we measured VDAC in a separate task by presenting these stimuli in the absence of reward contingency, and probing their effects on the processing of separate target stimuli presented at different time lags. Using time-resolved multivariate pattern analysis, we found that learned value modulated the spatial selection of previously rewarded stimuli in posterior visual and parietal cortex from [~]260ms after stimulus onset. This value modulation was related to the strength of participants behavioural VDAC effect and persisted into subsequent target processing. Furthermore, we found a spatially invariant value signal from [~]340ms. Importantly, learned value did not influence cortical signatures of early processing (i.e., earlier than [~]200ms), nor did it influence the decodability of the identity of previously rewarded stimuli. Our results suggest that VDAC is underpinned by learned value signals which modulate spatial selection throughout posterior visual and parietal cortex. We further suggest that VDAC can occur in the absence of changes in early visual processing in cortex. Significance statementAttention is our ability to focus on relevant information at the expense of irrelevant information. It can be affected by previously learned but currently irrelevant stimulus-reward associations, a phenomenon termed "value-driven attentional capture" (VDAC). The neural mechanisms underlying VDAC remain unclear. It has been speculated that reward learning induces visual cortical plasticity which modulates early visual processing to capture attention. Although we find that learned value modulates spatial signals in visual cortical areas, an effect which correlates with VDAC, we find no relevant signatures of changes in early visual processing in cortex.

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bioRxiv2018

The macaque anterior cingulate cortex translates counterfactual choice value into actual behavioral change

The neural mechanisms mediating sensory-guided decision making have received considerable attention but animals often pursue behaviors for which there is currently no sensory evidence. Such behaviors are guided by internal representations of choice values that have to be maintained even when these choices are unavailable. We investigated how four macaque monkeys maintained representations of the value of counterfactual choices - choices that could not be taken at the current moment but which could be taken in the future. Using functional magnetic resonance imaging, we found two different patterns of activity co-varying with values of counterfactual choices in a circuit spanning hippocampus, anterior lateral prefrontal cortex, and anterior cingulate cortex (ACC). ACC activity also reflected whether the internal value representations would be translated into actual behavioral change. To establish the causal importance of ACC for this translation process, we used a novel technique, Transcranial Focused Ultrasound Stimulation, to reversibly disrupt ACC activity.

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bioRxiv2018

Offline impact of transcranial focused ultrasound on cortical activation in primates

To understand brain circuits it is necessary both to record and manipulate their activity. Despite increased availability of techniques for manipulating neural activity in rodents, manipulating neural activity in primates remains difficult. Here we show that a minimally invasive technique, transcranial focused ultrasound stimulation (TUS), induced offline changes to activity of circumscribed brain regions in the macaque. Applying TUS to the supplementary motor area or frontal polar cortex resulted in spatially specific patterns of activity change measurable with functional magnetic resonance imaging. In each case changes reflected each areas known network of interactions with the rest of the brain. Independent of these specific neural effects, TUS over these regions also induced widespread signal changes that might have a non-neuronal origin possibly mediated by the cerebral spinal fluid compartment. Although sustained for more than one hour beyond the 40s stimulation period, TUS effects were reversible and not associated with histological changes.\n\nHighlights O_LIMany studies of ultrasound neuromodulation focus on online effects in rodents.\nC_LIO_LIWe use fMRI connectivity to investigate its offline impact in the primate brain.\nC_LIO_LI40 s of ultrasound leads to a sustained, specific, reversible neural modulation.\nC_LIO_LIUltrasound caused a sharpening of the stimulated regions connectivity profile.\nC_LI\n\nIn BriefA new application of focused ultrasound safely modulates brain activation in primates for up to 2 hours after 40 seconds of stimulation. Ultrasound caused the stimulated area to interact more selectively with the rest of the brain.

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bioRxiv2017

An open resource for nonhuman primate imaging

Non-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience.\n\nUnfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMate Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 13 independent data collections aggregated across 11 sites (total = 98 macaque monkeys). We also outline the unique pitfalls and challenges that should be considered in the analysis of the non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets.

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