Biology subjects

Tracey, I.

Publications and source records attributed to Tracey, I..

3 recordsLinked to original sources

bioRxiv2018

Cortico-brainstem mechanisms of biased perceptual decision-making in the context of pain

Perceptual decision-making is commonly studied using stimuli with different physical properties but of comparable affective value. Here, we investigate neural processes underlying human perceptual decisions in the affectively rich domain of pain using a drift-diffusion model in combination with a probabilistic cueing paradigm. This allowed us to characterize a novel role for the dorsolateral prefrontal cortex (DLPFC), whose anticipatory responses reflecting a decision bias were dependent on the affective value of the stimulus. During intense noxious stimulation, these model-based anticipatory DLPFC responses were linked to an engagement of the periaqueductal gray (PAG), a midbrain region implicated in defensive responses including analgesia. Complementing these findings on biased decision-making, the model parameter reflecting sensory processing predicted subcortical responses (in amygdala and PAG) when expectations were violated. Our findings highlight the importance of taking a broader perspective on perceptual decisions and link decisions about pain with subcortical circuitry implicated in endogenous pain modulation.

neuroscience↗

bioRxiv2018

Trace-based correction of breathing-induced field fluctuations in T2*-weighted imaging of the spinal cord

PurposeSpinal cord MRI at ultra-high field is hampered by time-varying magnetic fields associated with the breathing cycle, giving rise to ghosting artifacts in multi-shot acquisitions. Here, we suggest a correction approach based on linking the signal from a respiratory bellows to field changes inside the spinal cord. The information is used to correct the data at the image reconstruction level.\n\nMethodsThe correction was demonstrated in the context of multi-shot T2*-weighted imaging of the cervical spinal cord at 7T. A respiratory trace was acquired during a high-resolution multi-echo gradient-echo sequence, used for structural imaging and quantitative T2* mapping, and a multi-shot EPI time series, as would be suitable for fMRI. The coupling between the trace and the breathing-induced fields was determined by a short calibration scan in each individual. Images were reconstructed with and without trace-based correction.\n\nResultsIn the multi-echo GRE, breathing-induced fields caused severe ghosting in the long echo time images, which led to a systematic underestimation of T2* in the spinal cord. The trace-based correction reduced the ghosting and increased the estimated T2* values. Breathing-related ghosting was also observed in the multi-shot EPI images. The correction largely removed the ghosting, thereby improving the temporal signal-to-noise ratio of the time series.\n\nConclusionsTrace-based retrospective correction of breathing-induced field variations can reduce ghosting and improve quantitative metrics in multi-shot structural and functional T2*-weighted imaging of the spinal cord. The method is straightforward to implement and does not rely on sequence modifications or additional hardware beyond a respiratory bellows.

neuroscience↗

bioRxiv2018

CAN NEUROPATHIC PAIN PREDICT RESPONSE TO ARTHROPLASTY IN KNEE OSTEOARTHRITIS? A PROSPECTIVE OBSERVATIONAL COHORT STUDY.

A significant proportion of patients with knee osteoarthritis (OA) continue to have severe ongoing pain following knee replacement surgery. Central sensitization and features suggestive of neuropathic pain before surgery may result in a poor outcome post-operatively. In this prospective observational study of patients undergoing primary knee arthroplasty (n=120), the modified PainDETECT score was used to divide patients, with primary knee OA, into nociceptive (<13), unclear (13-18) and neuropathic -like pain (>18) groups pre-operatively. Response to surgery was compared between groups using the Oxford Knee Score (OKS) and the presence of moderate to severe long-term pain 12 months after arthroplasty. The analyses were replicated in a larger independent cohort study (n=404). 120 patients were recruited to the main study cohort: 63 (52%) nociceptive pain; 32 (27%) unclear pain; 25 (21%) neuropathic-like pain. Patients with neuropathic-like pain had significantly worse OKS pre and post-operatively, compared to the nociceptive pain group, independent of age, sex and BMI. At 12-months post-operatively the mean OKS was 4 points lower in the neuropathic-like group compared with the nociceptive group in the study cohort (non-significant); with a difference of 5 points in the replication cohort (p<0.001). Moderate to severe long-term pain after arthroplasty at 12-months was present in 50% of the neuropathic-like pain group versus 24% in the nociceptive pain group, in the replication cohort (p<0.001). Neuropathic pain is common and targeted therapy pre, peri and post-operatively may improve treatment response.

epidemiology↗