OxCIN Global Scholars + Publication Round Up

Allegra Moodley, Pranav Mahajan, James Bacon

Wednesday, 01 July 2026, 12pm to 1pm

Cowey Rooms (FMRIB Annexe)

Hosted by Michiel Cottaar, Caro Nettekoven

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Neuroimaging biomarkers of TBI and comorbid PTSD: from systematic evidence to longitudinal analysis

Presented by Allegra Moodley

Abstract: Traumatic brain injury (TBI) is a major global health concern and a key risk factor for the development of posttraumatic stress disorder (PTSD). Despite substantial overlap in symptomatology between these conditions, the neurobiological mechanisms underlying PTSD following TBI remain poorly understood. Neuroimaging studies have begun to identify structural and functional brain alterations associated with TBI and comorbid PTSD; however, findings remain inconsistent across studies.

This seminar will present work from my ongoing PhD investigating neuroimaging biomarkers associated with TBI and subsequent development of PTSD. Key findings from a systematic review highlights convergent alterations across fronto-limbic circuitry in individuals with TBI and comorbid PTSD, as well as hypoconnectivity within the default mode network. Interpretation of these findings, which implicate regions involved in emotion regulation, salience processing, and introspective thought, is limited by variability in study design, population characteristics, and methodological considerations.

Building on these findings, I will present ongoing work leveraging data from the CENTER-TBI multisite collaboration to examine structural and diffusion imaging markers associated with TBI and their relationship with PTSD symptom trajectories over the first year post-injury. By integrating cross-sectional and longitudinal imaging metrics, this work will examine the neurobiological vulnerability and recovery following TBI and shared imaging markers underlying PTSD development in a civilian cohort.

WIN Wednesday Publication Round Up

Balancing safety and efficiency in human decision making

Presented by Pranav Mahajan

Link: https://elifesciences.org/articles/101371

Abstract: The safety-efficiency dilemma describes the problem of maintaining safety during efficient exploration and is a special case of the exploration-exploitation dilemma in the face of potential dangers. Conventional exploration-exploitation solutions collapse punishment and reward into a single feedback signal, whereby early losses can be overcome by later gains. However, the brain has a separate system for Pavlovian fear learning, suggesting a possible computational advantage to maintaining a specific fear memory during exploratory decision-making. In a series of simulations, we show that this promotes safe but efficient learning and is optimised by arbitrating Pavlovian avoidance of instrumental decision-making according to uncertainty. We provide a basic test of this model in a simple human approach-withdrawal experiment in virtual reality and show that this flexible avoidance model captures choice and reaction times. These results show that the Pavlovian fear system has a more sophisticated role in decision-making than previously thought, by shaping flexible exploratory behaviour in a computationally precise manner.

MR Spectroscopy without Water Suppression using the Gradient Impulse Response Function

Presented by James Bacon

Abstract: Non-water-suppressed proton spectroscopy, 1H-MRS, is desirable, as retaining the strong water resonance can facilitate automated online data corrections, internal concentration referencing, and monitoring of line narrowing effects in functional MRS. Removal of the water suppression module can also mitigate magnetization transfer effects and slightly reduce the minimum achievable TR and total RF power deposition. However, water suppression is typically considered essential due to eddy current-induced antisymmetric sidebands on the water resonance that distort the spectral baseline and obscure metabolite signals.

Theory and Methods: The Gradient Impulse Response Function (GIRF) was used to predict time-dependent magnetic field perturbations during the FID that generate the artefactual sidebands. The GIRF was measured in a one-time calibration, independent of spectroscopy acquisitions, enabling post-processing correction of the sidebands without sequence modification or additional dedicated hardware. GIRF-corrected non-water-suppressed single-voxel-spectroscopy (SVS) was compared to otherwise identical water-suppressed acquisitions in eight participants at 3T using semi-LASER and MEGA-PRESS sequences.

Results: Across participants, GIRF correction reduced sideband amplitudes to levels comparable with the spectral baseline, enabling recovery of the underlying metabolite signals. Systematic increases in quantified metabolite concentrations were observed relative to water-suppressed acquisitions, consistent with water-suppression-induced magnetization transfer effects. Total creatine exhibited the largest increase, with enhancement ratios of 1.069±0.039 for MEGA-PRESS and 1.535±0.160 for semi-LASER acquisitions.

Conclusion: Gradient-induced artefactual sidebands in non-water-suppressed MR spectroscopy can be effectively corrected using the GIRF to predict time-dependent magnetic field perturbations during the FID. In principle, the approach extends to other SVS sequences and field strengths following appropriate GIRF calibration.

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