Refinement and Pattern Formation in Neural Circuits by the Interaction of Traveling Waves with Spike-Timing Dependent Plasticity

Traveling waves in the developing brain are a prominent source of highly correlated spiking activity that may instruct the refinement of neural circuits. A candidate mechanism for mediating such refinement is spike-timing dependent plasticity (STDP), which translates correlated activity patterns into changes in synaptic strength. To assess the potential of these phenomena to build useful structure in developing neural circuits, we examined the interaction of wave activity with STDP rules in simple, biologically plausible models of spiking neurons. We derive an expression for the synaptic strength dynamics showing that, by mapping the time dependence of STDP into spatial interactions, traveling waves can build periodic synaptic connectivity patterns into feedforward circuits with a broad class of experimentally observed STDP rules. The spatial scale of the connectivity patterns increases with wave speed and STDP time constants. We verify these results with simulations and demonstrate their robustness to likely sources of noise. We show how this pattern formation ability, which is analogous to solutions of reaction-diffusion systems that have been widely applied to biological pattern formation, can be harnessed to instruct the refinement of postsynaptic receptive fields. Our results hold for rich, complex wave patterns in two dimensions and over several orders of magnitude in wave speeds and STDP time constants, and they provide predictions that can be tested under existing experimental paradigms. Our model generalizes across brain areas and STDP rules, allowing broad application to the ubiquitous occurrence of traveling waves and to wave-like activity patterns induced by moving stimuli

Subtotal colectomy for ulcerative colitis: lessons learned from a tertiary centre

Aim: Subtotal colectomy (STC) is a well‐established treatment for complicated and refractory ulcerative colitis (UC). A laparoscopic approach offers potentially improved outcomes. The aim of the study was to report our experience with STC for UC in a single large centre. Method: From January 2007 to May 2015, all consecutive patients undergoing STC for UC were retrospectively analysed from a prospectively managed database. Patients with known Crohn's disease or those undergoing one‐stage procedures were excluded. Demographics, perioperative outcomes and second‐stage procedures were analysed. Results: During the study period, 151 STCs were performed for UC [100 emergency (66%) and 51 elective (34%)]. Acute severe colitis refractory to therapy was the most common indication (62%). Overall, 117 laparoscopic (78%) and 34 open STCs were performed, with a conversion rate of 14.5%. Mortality and morbidity rates were 0.7% and 38%, respectively. Whilst operative time was shorter for open STC (by 75 min; P = 0.001), there were fewer complications (32% vs 62%; P = 0.002) and a shorter hospital stay (by 6.9 days; P = 0.0002) following laparoscopic STC. Fewer complications and shorter hospital stay were also observed after elective STC. Patients undergoing laparoscopic STC were more likely to undergo a restorative second‐stage procedure than those having open STC (75% vs 50%; P = 0.03). Conclusion: Laparoscopic STC for UC is feasible and safe, even in the emergency situation. A laparoscopic approach may offer advantages in terms of lower morbidity and reduced length of stay. Elective resection may offer similar advantages and is best performed whenever possible.</p

A two centre experience of transanal total mesorectal excision

Transanal total mesorectal excision (TaTME) offers a promising alternative to the standard surgical adominopelvic approach for rectal cancer. The aim of this study was to report a two centre experience of this technique, focusing on the short-term and oncological outcome.From May 2013 to May 2015, 40 selected patients with histologically proven rectal adenocarcinoma underwent TaTME in two institutions and were prospectively entered on an online international registry.Forty patients (80% male, mean body mass index (BMI) of 27.4 kg/m(2) ) requiring total mesorectal excision underwent TaTME. Procedures included low anterior resection (n=31), abdominoperineal excision (n=7), and proctocolectomy (n=2). A minimally invasive approach was attempted in all the cases, with three conversions. The mean operation time was 368 minutes and 16 patients (40%) had a synchronous abdominal and transanal approach. There was no mortality and 16 postoperative complications occurred all of which 68.8% were minor. The median length of stay was 7.5 (3-92) days. A complete or near-complete TME specimen was delivered in 39 (97.5%) cases with a mean number of 20 lymph nodes harvested. R0 resection was achieved in 38 (95%) patients. After a median follow-up of 10.7 months, there were no local recurrences and six (15%) patients had developed distant metastases.TaTME appears to be feasible, safe and reproducible, without compromising the oncological principles of rectal cancer surgery. It is an attractive option for patients for whom laparoscopy is likely to be particularly difficult. These encouraging results should encourage larger studies with assessment of long-term function and the oncological outcome

A two centre experience of transanal total mesorectal excision

Transanal total mesorectal excision (TaTME) offers a promising alternative to the standard surgical adominopelvic approach for rectal cancer. The aim of this study was to report a two centre experience of this technique, focusing on the short-term and oncological outcome.From May 2013 to May 2015, 40 selected patients with histologically proven rectal adenocarcinoma underwent TaTME in two institutions and were prospectively entered on an online international registry.Forty patients (80% male, mean body mass index (BMI) of 27.4 kg/m(2) ) requiring total mesorectal excision underwent TaTME. Procedures included low anterior resection (n=31), abdominoperineal excision (n=7), and proctocolectomy (n=2). A minimally invasive approach was attempted in all the cases, with three conversions. The mean operation time was 368 minutes and 16 patients (40%) had a synchronous abdominal and transanal approach. There was no mortality and 16 postoperative complications occurred all of which 68.8% were minor. The median length of stay was 7.5 (3-92) days. A complete or near-complete TME specimen was delivered in 39 (97.5%) cases with a mean number of 20 lymph nodes harvested. R0 resection was achieved in 38 (95%) patients. After a median follow-up of 10.7 months, there were no local recurrences and six (15%) patients had developed distant metastases.TaTME appears to be feasible, safe and reproducible, without compromising the oncological principles of rectal cancer surgery. It is an attractive option for patients for whom laparoscopy is likely to be particularly difficult. These encouraging results should encourage larger studies with assessment of long-term function and the oncological outcome