Biology subjects

Jamieson, A. J.

Publications and source records attributed to Jamieson, A. J..

10 recordsLinked to original sources

bioRxiv2026

Mapping the neural circuitry of cognitive restructuring in depressive and anxiety disorders

BackgroundCognitive restructuring, the process of identifying and challenging negative thoughts, is a key technique for treating depressive and anxiety disorders. Although neuroimaging studies have characterised the brain systems supporting cognitive restructuring in healthy individuals, it remains unclear how these systems are altered in depression and anxiety, or whether each disorder is associated with distinct neural dysfunction. MethodsSeventy-three clinical participants with depressive or anxiety disorders and 70 healthy controls completed a cognitive restructuring paradigm during 7 Tesla functional magnetic resonance imaging (fMRI). The task required participants to either repeat a series of negative statements or challenge them using Socratic questioning. Group-level fMRI analyses examined the effects of depressive and anxiety symptom severity on brain activation, while dynamic causal modelling characterized the directional neural influences between implicated regions. ResultsDuring challenging compared to repeating statements, greater depressive symptoms were associated with reduced dorsolateral prefrontal cortex (dlPFC) activation. Conversely, greater anxiety symptoms were associated with greater dlPFC activation. Effective connectivity results revealed that depressive symptoms were associated with greater inhibition from the ventrolateral prefrontal cortex (vlPFC) to the ventromedial prefrontal cortex, whereas anxiety symptoms were associated with greater excitation from the dlPFC to amygdala and greater inhibition from the vlPFC to amygdala. ConclusionsWhile clinical participants modified negative beliefs as effectively as healthy controls, depressive and anxiety symptoms were associated with dissociable neural signatures during restructuring. This suggests that cognitive behavioral therapy may engage partially distinct mechanisms depending on symptom profile, a possibility that warrants longitudinal investigation of treatment response.

neuroscience↗

bioRxiv2026

Automated and quantitative characterization of multi-scale benthic habitat and associated biological communities of an unknown southeast Pacific seamount

Seamounts are prominent deep-ocean features that strongly influence geological processes, ocean circulation, and benthic biodiversity. Despite their importance, most seamounts remain unmapped and poorly characterized, particularly in the southeast Pacific Ocean, a region recognized for high marine endemism and ecological isolation. In this study, we present a quantitative habitat characterization of a previously undocumented seamount, informally named Solito Seamount, located between the Nazca-Desventuradas Marine Park and the Juan Fernandez Archipelago. High-resolution multibeam bathymetry and backscatter intensity data were integrated with in situ observations from two remotely operated vehicle (ROV) dives (SO643 and SO645) to investigate how geomorphology and substrate distribution influence benthic community patterns. An automated and hierarchical quantitative mapping framework incorporating objective terrain analysis and multivariate statistical techniques, including principal component analysis and clustering, was applied to delineate five distinct megahabitat types: flat, basal slope, valley, ridge slope, and ridge crest. ROV video transects traversing these megahabitats revealed five associated substrate type forming macrohabitats: bedrock, bedrock with sediment veneer, sediment-rock transition, sediment, and coral rubble. Outputs were used to investigate how environmental heterogeneity structures megafaunal assemblages of Solito Seamount. Multivariate analysis revealed a combined effect of megahabitat type and substrate type on benthic megafaunal assemblages across the depth gradient. These compositional dissimilarities were primarily driven by habitat-forming taxa. In the deeper dive (SO643), a broad suite of taxa contributed to dissimilarities, and assemblages were primarily organised by megahabitat. The ridge crest hosted a distinct reef-building scleractinian community, whereas the ridge slope hosted mixed antipatharian, gorgonian and actiniarian assemblages. In contrast, the shallower dive exhibited simpler patterns with few taxa driving dissimilarities. Substrate effects were most pronounced with coral rubble forming a distinct habitat characterised by sponges (Stelletta sp.). Pronounced biological differences between dives may also represent depth-dependent structuring resulting from differences in oxygen regimes associated with water masses, underscoring the role of oceanographic forcing. This study provides the first quantitative habitat map of this previously undocumented seamount, delivering essential baseline information for this largely unexplored region of the southeast Pacific. The integrated multi-scale geophysical and biological approach presented here offers a robust framework for advancing seamount ecosystem understanding and supporting future biodiversity assessments and conservation planning.

ecology↗

bioRxiv2025

Bivalent habenula modulation of human monoaminergic midbrain and cortical pathways

The habenula is implicated in signaling negative reward prediction errors (RPE), yet direct causal evidence demonstrating its influence on downstream human brain circuits is limited. Using ultra-high field (7T) fMRI and dynamic causal modelling across two negative RPE-inducing experimental tasks, we characterize habenula-directed connectivity with monoaminergic midbrain and cortical pathways in healthy adults. Negative feedback drove strong habenula inhibition of ventral tegmental area and dorsal raphe nucleus activity, while positive feedback had an excitatory effect. These core effects are replicated across reversal learning and perceptual decision uncertainty tasks, establishing a generalizable mechanism for behavioral adaptation. Task-specific modulatory effects emerged in pathways between the subcortical and cortical regions (ventral tegmental area[->]dorsal anterior cingulate cortex, dorsal raphe nucleus[->]medial prefrontal cortex, and dorsal anterior cingulate cortex[->]habenula), revealing context-dependent cortical elaboration of negative RPE-driven habenula signals. This provides the first evidence in humans for bivalent causal modulation of habenula function on monoaminergic midbrain and cortical pathways, demonstrating how the brain integrates negative and positive signals to guide adaptive behavior.

neuroscience↗

bioRxiv2025

Dissecting heterogeneity in cortical thickness abnormalities in major depressive disorder: a large-scale ENIGMA MDD normative modelling study

ImportanceMajor depressive disorder (MDD) is highly heterogeneous, with marked individual differences in clinical presentation and neurobiology, which may obscure identification of structural brain abnormalities in MDD. To explore this, we used normative modeling to index regional patterns of variability in cortical thickness (CT) across individual patients. ObjectiveTo use normative modeling in a large dataset from the ENIGMA MDD consortium to obtain individualised CT deviations from the norm (relative to age, sex and site) and examine the relationship between these deviations and clinical characteristics. Design, setting, and participantsA normative model adjusting for age, sex and site effects was trained on 35 CT measures from FreeSurfer parcellation of 3,181 healthy controls (HC) from 34 sites (40 scanners). Individualised z-score deviations from this norm for each CT measure were calculated for a test set of 2,119 HC and 3,645 individuals with MDD. For each individual, each CT z-score was classified as being within the normal range (95% of individuals) or within the extreme range (2.5% of individuals with the thinnest or thickest cortices). Main outcome measuresZ-score deviations of CT measures of MDD individuals as estimated from a normative model based on HC. ResultsZ-score distributions of CT measures were largely overlapping between MDD and HC (minimum 92%, range 92-98%), with overall thinner cortices in MDD. 34.5% of MDD individuals, and 30% of HC individuals, showed an extreme deviation in at least one region, and these deviations were widely distributed across the brain. There was high heterogeneity in the spatial location of CT deviations across individuals with MDD: a maximum of 12% of individuals with MDD showed an extreme deviation in the same location. Extreme negative CT deviations were associated with having an earlier onset of depression and more severe depressive symptoms in the MDD group, and with higher BMI across MDD and HC groups. Extreme positive deviations were associated with being remitted, of not taking antidepressants and less severe symptoms. Conclusions and relevanceOur study illustrates a large heterogeneity in the spatial location of CT abnormalities across patients with MDD and confirms a substantial overlap of CT measures with HC. We also demonstrate that individualised extreme deviations can identify protective factors and individuals with a more severe clinical picture. Key points QuestionCan z-scores derived from normative modelling shed light on the heterogeneous group-level findings of cortical thickness abnormalities in major depression and what characterises individuals at the extreme ends of cortical thickness abnormalities? FindingWe confirmed a large overlap in z-score distributions between depressed individuals and healthy controls and a heterogeneous spatial distribution of extreme z-deviations across brain regions across individual patients. Lower z-scores for cortical thickness were related to more severe clinical characteristics. MeaningOur findings confirm the heterogeneity in individual variation in the location and extent of CT abnormalities across patients with MDD and stress the importance of individualised predictions when examining cortical thickness abnormalities.

neuroscience↗

bioRxiv2024

Altered basal forebrain regulation of intrinsic brain networks in depressive and anxiety disorders

Depressive and anxiety disorders are characterized by altered connectivity within and between the default mode (DMN) and salience networks. Basal forebrain subdivisions, critical for regulating network activity, remain understudied across these conditions. To address this gap, we analyzed 7-Tesla resting-state functional magnetic resonance imaging data from a transdiagnostic sample (n = 70), primarily with depressive and anxiety disorders, and healthy controls (n = 77). We used spectral dynamic causal modelling to assess effective connectivity between the medial septum/diagonal band (Ch1-3), nucleus basalis of Meynert (Ch4), ventral pallidum, and DMN and salience networks. Healthy participants showed excitatory connectivity from Ch1-3 to the DMN and from Ch4 to the anterior insula. In contrast, clinical participants exhibited greater inhibitory Ch4 to DMN connectivity and increased excitatory connectivity from Ch4 to the anterior insula. Wide-spread Ch4 connectivity dysfunction may implicate the cholinergic system as a mechanistic and therapeutic target for depressive and anxiety disorders.

neuroscience↗

bioRxiv2023

Graded changes in local functional connectivity of the brain in young people with depression

Major depressive disorder (MDD) is marked by significant changes to the coupling of spontaneous neural activity within various brain regions. However, many methods for assessing this local connectivity use fixed or arbitrary neighborhood sizes, resulting in a decreased capacity to capture smooth changes to the spatial gradient of local correlations. A newly developed method sensitive to classical anatomo-functional boundaries, Iso-Distant Average Correlation (IDAC), was therefore used to examine depression associated alterations to the local functional connectivity of the brain. One-hundred and forty-five adolescents and young adults with MDD and 95 healthy controls underwent a resting-state fMRI scan. Whole-brain functional connectivity maps of intracortical neural activity within iso-distant local areas (5-10mm, 15-20mm, and 25-30mm) were generated to characterize local fMRI signal similarities. Across all spatial distances, MDD participants demonstrated greater local functional connectivity of the bilateral posterior hippocampus, retrosplenial cortex, dorsal insula, fusiform gyrus, and supplementary motor area. Additionally, in the short and medium range connections there were depression associated alterations in the midcingulate (15-20mm and 25-30mm) and subgenual anterior cingulate (15-20mm). Our study identified increased synchrony of the neural activity in several regions commonly implicated in the neurobiology of depression; however, a subset of identified effects was dependent on the spatial distance under consideration. Longitudinal examination of these effects will clarify whether these differences are also found in other age groups and if this synchrony is additionally altered by continued disease progression.

neuroscience↗

bioRxiv2023

A Brain Model of Disturbed Self-Appraisal in Social Anxiety Disorder

The brains default mode network has a central role in the processing of information concerning oneself. Dysfunction in this self-referential processing represents a key component of multiple mental health conditions, including social anxiety disorder (SAD). This case-control study aimed to clarify alterations to network dynamics present during self-appraisal in SAD participants. A total of 38 adolescents and young adults with SAD and 72 healthy control participants underwent a self-referential processing fMRI task. The task involved two primary conditions of interest: direct self-appraisal (thinking about oneself) and reflected self-appraisal (thinking about how others might think about oneself). Dynamic causal modelling and parametric empirical Bayes were then used to explore differences in the effective connectivity of the default mode network between groups. We observed connectivity differences between SAD and healthy control participants in the reflected self-appraisal but not the direct self-appraisal condition. Specifically, SAD participants exhibited greater excitatory connectivity from the posterior cingulate cortex (PCC) to medial prefrontal cortex (MPFC) and greater inhibitory connectivity from the inferior parietal lobule (IPL) to MPFC. In contrast, in the absence of task modulation, SAD participants exhibited reduced intrinsic connectivity, with reduced excitatory connectivity from the PCC to MPFC and reduced inhibitory connectivity from the IPL to MPFC. As such, participants with SAD showed changes to afferent connections to the MPFC which occurred during both reflected self-appraisal as well as intrinsically. The presence of connectivity differences in reflected and not direct self-appraisal is consistent with the characteristic fear of negative social evaluation that is experienced by people with SAD.

neuroscience↗

bioRxiv2022

Microbiomes of hadal fishes contain similar taxa, obligate symbionts, and known piezophiles across trench habitats

Hadal snailfishes are the deepest-living fishes in the ocean, inhabiting trenches from depths of [~]6,000 to 8,000 m. While the microbial communities in trench environments have begun to be characterized, the microbes associated with hadal megafauna remain relatively unknown. Here, we describe the gut microbiomes of two hadal snailfishes, Pseudoliparis swirei (Mariana Trench) and Notoliparis kermadecensis (Kermadec Trench) using 16S rRNA gene amplicon sequencing. We contextualize these microbiomes with comparisons to the abyssal macrourid Coryphaenoides yaquinae and the continental shelf-dwelling snailfish Careproctus melanurus. The microbial communities of the hadal snailfishes were distinct from their shallower counterparts and were dominated by the same sequences related to the Mycoplasmataceae and Desulfovibrionaceae. These shared taxa indicate that symbiont lineages may have remained similar to the ancestral symbiont since their geographic separation or that they are dispersed between geographically distant trenches and subsequently colonize specific hosts. The abyssal and hadal fishes contained sequences related to known, cultured piezophiles, microbes that grow optimally under high hydrostatic pressure, including Psychromonas, Moritella, and Shewanella. These taxa are adept at colonizing nutrient-rich environments present in the deep ocean, such as on particles and in the guts of hosts, and we hypothesize they could make a dietary contribution to deep-sea fishes by degrading chitin and producing fatty acids. We characterize the gut microbiota within some of the deepest fishes to provide new insight into the diversity and distribution of host-associated microbial taxa and the potential of these animals, and the microbes they harbor, for understanding adaptation to deep-sea habitats. ImportanceHadal trenches, characterized by high hydrostatic pressures and low temperatures, are one of the most extreme environments on our planet. By examining the microbiome of abyssal and hadal fishes, we provide insight into both the physiology of the deepest-living vertebrates and the microbes which colonize them. Our findings show that there are similar microbial populations in fishes geographically separated by thousands of miles, reflecting strong selection for specific microbial lineages. Only a handful of psychropiezophilic taxa, which do not reflect the diversity of microbial life at great depth, have been successfully isolated in the laboratory. Our examination of deep-sea fish microbiomes shows that typical high-pressure culturing methodologies, which have largely remained unchanged since the pioneering work of Claude ZoBell in the 1950s, may simulate the chemical environment found in animal guts and helps explain why the same deep-sea genera are consistently isolated.

microbiology↗

bioRxiv2021

Dynamic Subcortical Modulators of Human Default Mode Network Function

The brains default mode network (DMN) enables flexible switching between internally and externally focused cognition. Precisely how this modulation occurs is not well understood, although may involve key subcortical mechanisms, including hypothesized influences from the basal forebrain (BF) and mediodorsal thalamus (MD). Here, we used ultra-high field (7T) functional magnetic resonance imaging to examine the involvement of the BF and MD across states of task-induced DMN activity modulation. Specifically, we mapped DMN activity suppression ( deactivation) when participants transitioned between rest and externally focused task performance, as well as DMN activity engagement ( activation) when task performance was internally (i.e., self) focused. Consistent with recent rodent studies, the BF showed overall activity suppression with DMN cortical regions when comparing the rest to external task conditions. Further analyses, including dynamic causal modelling, confirmed that the BF drove changes in DMN cortical activity during these rest-to-task transitions. The MD, by comparison, was specifically engaged during internally focused cognition and demonstrated a broad excitatory influence on DMN cortical activation. These results provide the first direct evidence in humans of distinct basal forebrain and thalamic circuit influences on the control of DMN function and suggest novel mechanistic avenues for ongoing translational research.

neuroscience↗

bioRxiv2021

A thalamo-centric neural signature for restructuring negative self-beliefs

Negative self-beliefs are a core feature of psychopathology. Despite this, we have a limited understanding of the brain mechanisms by which negative self-beliefs are cognitively restructured. Using a novel paradigm, we had participants use Socratic questioning techniques to restructure self-beliefs during ultra-high resolution 7-Tesla functional magnetic resonance imaging (UHF fMRI) scanning. Cognitive restructuring elicited prominent activation in a fronto-striato-thalamic circuit, including the mediodorsal thalamus (MD), a group of deep subcortical nuclei believed to synchronize and integrate prefrontal cortex activity, but which has seldom been directly examined with fMRI due to its small size. Increased activity was also identified in the medial prefrontal cortex (MPFC), a region consistently activated by internally focused mental processing, as well as in lateral prefrontal regions associated with regulating emotional reactivity. Using Dynamic Causal Modelling (DCM), evidence was found to support the MD as having a strong excitatory effect on the activity of regions within the broader network mediating cognitive restructuring. Moreover, the degree to which participants modulated MPFC-to-MD effective connectivity during cognitive restructuring predicted their individual tendency to engage in repetitive negative thinking. Our findings represent a major shift from a cortico-centric framework of cognition and provide important mechanistic insights into how the MD facilitates key processes in cognitive interventions for common psychiatric disorders. In addition to relaying integrative information across basal ganglia and the cortex, we propose a multifaceted role for the MD whose broad excitatory pathways act to increase synchrony between cortical regions to sustain complex mental representations, including the self.

neuroscience↗