Closed-loop optogenetic control of the dynamics of neural activity in non-human primates

Electrical neurostimulation is effective in the treatment of neurological disorders, but associated recording artefacts generally limit its applications to open-loop stimuli. Real-time and continuous closed-loop control of brain activity can, however, be achieved by pairing concurrent electrical recordings and optogenetics. Here we show that closed-loop optogenetic stimulation with excitatory opsins enables the precise manipulation of neural dynamics in brain slices from transgenic mice and in anaesthetized non-human primates. The approach generates oscillations in quiescent tissue, enhances or suppresses endogenous patterns in active tissue and modulates seizure-like bursts elicited by the convulsant 4-aminopyridine. A nonlinear model of the phase-dependent effects of optical stimulation reproduced the modulation of cycles of local-field potentials associated with seizure oscillations, as evidenced by the systematic changes in the variability and entropy of the phase-space trajectories of seizures, which correlated with changes in their duration and intensity. We also show that closed-loop optogenetic neurostimulation could be delivered using intracortical optrodes incorporating light-emitting diodes. Closed-loop optogenetic approaches may be translatable to therapeutic applications in humans.

Worm Control in Livestock: Bringing Science to the Field

Parasitic roundworm infections are ubiquitous in grazing livestock. Chemical control through the frequent 'blanket' administration of anthelmintics (wormers) has been, and remains, the cornerstone in controlling these infections, but this practice is unsustainable. Alternative strategies are available but, even with the plethora of best practice advice available, have yet to be integrated into routine farming practice. This is probably due to a range of factors, including contradictory advice from different sources, changes to advice following increased scientific understanding, and top-down knowledge exchange patterns. In this article, we discuss the worm control options available, the translation of new best practice advice from science bench to field, and ideas for future work and directions.

Prognostic value of a nine-minute treadmill test in patients undergoing myocardial perfusion scintigraphy

Exercise capacity is an important predictor of risk in known or suspected coronary disease. A negative treadmill test to 9 minutes of the Bruce protocol is often used in the screening process for vocational licensing; myocardial perfusion scintigraphy is an alternative for those unable to exercise, with apparent incremental prognostic power above exercise testing alone. We compared exercise test and myocardial perfusion scintigraphic (MPS) findings and risk of hard cardiac events (median 4 years) in patients completing ≥ 9-minute treadmill exercise. Patients undergoing myocardial perfusion scintigraphy who completed a 9-minute Bruce protocol exercise were identified over a 2-year period. Follow-up was performed by telephone, with case-note review when necessary; this was 97% complete. Five hundred sixteen patients were identified (73% men, median age 53 year). One hundred eighty-one (35%) had known coronary disease. One hundred forty-nine (29%) had a "high-risk" exercise test result (limiting chest pain or ST-segment depression), and 69 (13%) had high-risk MPS findings (>10% myocardium ischemic or ejection fraction <40%). Of 367 patients with a reassuring exercise test result, 38 (10.4%) had high-risk MPS findings. Of 149 with a high-risk exercise test, 118 (79%) had reassuring MPS findings. At median follow-up of 49 months, there were 8 cardiac events (1.6%). Only 2 patients with high-risk exercise test results (1.4%) and 1 with high-risk MPS findings (1.5%) had an event. In conclusion, for patients able to manage a 9-minute Bruce protocol, presence/absence of symptoms or electrocardiographic changes is a poor predictor of MPS findings. Irrespective of test findings, however, subsequent cardiac risk is extremely low. Ability to complete a 9-minute Bruce protocol treadmill exercise may itself provide adequate prognostic reassurance for most purposes.

Does myocardial perfusion scintigraphy predict improvement in symptoms and exercise capacity following successful elective percutaneous coronary intervention?

BACKGROUND

Elective percutaneous coronary intervention (PCI) without inducible ischaemia may not be beneficial. We investigated the prevalence of inducible hypoperfusion using myocardial perfusion scintigraphy (MPS) in patients undergoing PCI, and its ability to predict functional outcome.

METHODS AND RESULTS

One hundred and twenty-three patients listed for elective PCI underwent MPS, using treadmill exercise where possible. Seventy-seven patients (63%) described chest pain in daily life. Seventy-four of 103 (72%) exercise ECG tests were positive. Ninety-one (74%) had inducible hypoperfusion on MPS (extensive in 25; 20%). Interventionalists were blinded to the scintigraphic results, and PCI was performed as planned. Six months later, Seattle Angina Questionnaire physical limitation score had improved from 66 to 76 (P < 0.0001), and peak treadmill workload from 7.2 +/- 2.3 to 9.0 +/- 2.7 METS (P < 0.0001). Sex, limiting chest pain on baseline exercise testing, and MPS summed difference score (SDS) were independent predictors of improvement. Patients with both limiting chest pain and SDS > or = 7 demonstrated an increase of 3.3 +/- 1.8 METS, compared with approximately 1.5 METS for other subgroups (P < 0.05).

CONCLUSIONS

Many patients undergoing elective PCI in a UK centre have little or no evidence of inducible hypoperfusion. The combination of limiting chest pain during exercise testing and significant inducible hypoperfusion on MPS predicts a large increase in exercise capacity after PCI.