Mesolimbic dopamine release conveys causal associations.

Learning to predict rewards based on environmental cues is essential for survival. It is believed that animals learn to predict rewards by updating predictions whenever the outcome deviates from expectations, and that such reward prediction errors (RPEs) are signaled by the mesolimbic dopamine system-a key controller of learning. However, instead of learning prospective predictions from RPEs, animals can infer predictions by learning the retrospective cause of rewards. Hence, whether mesolimbic dopamine instead conveys a causal associative signal that sometimes resembles RPE remains unknown. We developed an algorithm for retrospective causal learning and found that mesolimbic dopamine release conveys causal associations but not RPE, thereby challenging the dominant theory of reward learning. Our results reshape the conceptual and biological framework for associative learning.

Elastic Image Fusion Software to Coregister Preoperatively Planned Pedicle Screws With Intraoperative Computed Tomography Data for Image-Guided Spinal Surgery.

BACKGROUND: For complex spinal cases, especially when robotic guidance is used, preoperative planning of pedicle screws can be helpful. Transfer of these preoperatively planned pedicle screws to intraoperative 3-dimensional imaging is challenging because of changes in anatomic alignment between preoperative supine and intraoperative prone imaging, especially when multiple levels are involved. In the spine, where each individual vertebra is subject to independent movement from adjacent level, rigid image fusion is confined to a single vertebra and can display fusion inaccuracies on adjacent levels. A novel elastic fusion algorithm is introduced to overcome these disadvantages. This study aimed to investigate image registration accuracy of preoperatively planned pedicle screws with an elastic fusion algorithm vs. rigid fusion for intraoperative placement with image-guided surgery. METHODS: A total of 12 patients, were selected depending on the availability of a preoperative spinal computed tomography (CT) and an intraoperative AIRO CT scan (BrainLAB AG, Munich, Germany) of the same spinal region. To verify accuracy differences between rigid fusion and elastic fusion 76 bilateral screw trajectories were virtually defined in the preoperative CT image, and they were transferred via either rigid fusion or elastic fusion to the intraoperative CT scan. Accuracy of the transferred screws in the rigid and elastic fusion group was determined by measuring pedicle breaches on the intraoperative CT. RESULTS: In the rigid fusion group 1.3% of screws showed a breach of less than 2 mm, 9.2% showed breaches between 2 and 4 mm, and 18.4% of the screws showed an error above 4 mm. The elastic fusion group showed no breaches and provided high accuracy between preoperative and intraoperative screw placement. CONCLUSION: Elastic fusion provides high registration accuracy and represents a considerable step towards efficiency and safety in CT-based image-guided surgery. LEVEL OF EVIDENCE: 3.

Travel behaviour of patients with haemophilia.

BACKGROUND: We aimed to identify socio-demographic, or illness-specific variables, influencing travel behaviour of haemophilic patients. METHODS: A standardised questionnaire was sent to more than 2000 members of two German Haemophilia associations. Multivariable logistic regression with the outcomes frequent (at least two journeys per year) and long-haul travel (outside of Europe) was applied separately on adult patients and patients younger than 18 years. RESULTS: Among 345 adults, high education level, living in a partnership or travelling alone was significantly associated with frequent travel with odds ratios (ORs)/95%-confidence intervals (95%-CI) of 3.10/1.72-5.80, 1.99/1.10-3.62 and 1.73/1.01-3.62, respectively. High education level and self-application of clotting factors were significant variables for long-haul travel (OR/95%-CI: 2.45/1.43-4.26 and 3.25/1.33-8.52, respectively). Among 144 non-adults, a younger age or performing permanent prophylactic treatment was significantly associated with a lower likelihood for long-haul travel (OR/95%-CI: 0.51/0.22-0.95 and 0.10/0.01-0.65, respectively). Longer awareness of the disease increased the likelihood for long-haul travel (OR/95%-CI: 1.06/1.01-1.14). CONCLUSIONS: High education level and self-application of clotting factors influence travel intensity of adult patients most strikingly. Parents of very young patients on permanent prophylactic treatment might need special education to facilitate holiday travel for these families.