Click-train evoked steady state harmonic response as a novel pharmacodynamic biomarker of cortical oscillatory synchrony.

Sensory networks naturally entrain to rhythmic stimuli like a click train delivered at a particular frequency. Such synchronization is integral to information processing, can be measured by electroencephalography (EEG) and is an accessible index of neural network function. Click trains evoke neural entrainment not only at the driving frequency (F), referred to as the auditory steady state response (ASSR), but also at its higher multiples called the steady state harmonic response (SSHR). Since harmonics play an important and non-redundant role in acoustic information processing, we hypothesized that SSHR may differ from ASSR in presentation and pharmacological sensitivity. In female SD rats, a 2 s-long train stimulus was used to evoke ASSR at 20 Hz and its SSHR at 40, 60 and 80 Hz, recorded from a prefrontal epidural electrode. Narrow band evoked responses were evident at all frequencies; signal power was strongest at 20 Hz while phase synchrony was strongest at 80 Hz. SSHR at 40 Hz took the longest time (∼180 ms from stimulus onset) to establish synchrony. The NMDA antagonist MK801 (0.025-0.1 mg/kg) did not consistently affect 20 Hz ASSR phase synchrony but robustly and dose-dependently attenuated synchrony of all SSHR. Evoked power was attenuated by MK801 at 20 Hz ASSR and 40 Hz SSHR only. Thus, presentation as well as pharmacological sensitivity distinguished SSHR from ASSR, making them non-redundant markers of cortical network function. SSHR is a novel and promising translational biomarker of cortical oscillatory dynamics that may have important applications in CNS drug development and personalized medicine.

Transitory percutaneous pinning in fractures of the proximal humerus.

We report 31 patients with displaced fractures of the proximal humerus treated by transitory percutaneous pinning. The Neer fracture classification was used; there were 7 two-part, 20 three-part, and 4 four-part fractures. The Constant score was used for evaluation of the results; the mean score was 80 points. The high mean age of our patients (68 years) diminished the score because of the 25 points attributed to the strength. Avascular necrosis was observed in 5 cases: 2 three-part and 3 four-part fractures. Transitory percutaneous pinning is a good technique for the management of displaced 3-part fractures of the proximal humerus even in the older population, keeping in mind that the shoulder will tolerate a moderate residual deformity without changing the functional outcome significantly. Transitory percutaneous pinning, on the other hand, is not a satisfactory method for the management of 4-part fractures.