Parabolic avalanche scaling in the synchronization of cortical cell assemblies.

Neurons in the cerebral cortex fire coincident action potentials during ongoing activity and in response to sensory inputs. These synchronized cell assemblies are fundamental to cortex function, yet basic dynamical aspects of their size and duration are largely unknown. Using 2-photon imaging of neurons in the superficial cortex of awake mice, we show that synchronized cell assemblies organize as scale-invariant avalanches that quadratically grow with duration. The quadratic avalanche scaling was only found for correlated neurons, required temporal coarse-graining to compensate for spatial subsampling of the imaged cortex, and suggested cortical dynamics to be critical as demonstrated in simulations of balanced E/I-networks. The corresponding time course of an inverted parabola with exponent of χ = 2 described cortical avalanches of coincident firing for up to 5 s duration over an area of 1 mm2. These parabolic avalanches maximized temporal complexity in the ongoing activity of prefrontal and somatosensory cortex and in visual responses of primary visual cortex. Our results identify a scale-invariant temporal order in the synchronization of highly diverse cortical cell assemblies in the form of parabolic avalanches.

Altering undigested neutral detergent fiber through additives applied in corn, whole barley crop, and alfalfa silages, and its effect on performance of lactating Holstein dairy cows.

OBJECTIVE: We hypothesized that silage additives may alter the undigested neutral detergent fiber (uNDF) content through ensiling. Therefore, urea and formic acid were applied to corn, whole barley crop (WBC) and alfalfa to change uNDF content of the ensiled forages. METHODS: Six experimental diets at two groups of high uNDF (untreated corn and alfalfa silages [CSAS] and untreated whole barley and alfalfa silages [BSAS]) and low uNDF (urea-treated corn silage+untreated alfalfa silage [CSUAS], urea-treated whole barley silage+untreated alfalfa silage [BSUAS], untreated corn silage+formic acid-treated alfalfa silage [CSASF], and untreated whole barley silage+formic acid-treated alfalfa silage [BSASF]), were allocated to thirty-six multiparous lactating Holstein dairy cows. RESULTS: The untreated silages were higher in uNDF than additive treated silages, but the uNDF concentrations among silages were variable (corn silage0.05). Milk yield tended to increase in the cows fed high uNDF diets than those fed low uNDF (p = 0.10). The cows fed diet based on urea-treated corn silage had higher milk yield than those fed other silages (p = 0.05). The substitution of corn silage with the WBC silage tended to decrease milk production (p = 0.07). Changing the physical source of NDF supply and the uNDF content from the corn silage to the WBC silage caused a significant increase in ruminal NH3-N concentration, milk urea-N and fat yield (p< 0.05). The cows fed diets based on WBC silage experienced greater rumination time than the cows fed corn silage (p<0.05). CONCLUSION: Administering additives to silages to reduce uNDF may improve the performance of Holstein dairy cows.

Enhanced tagging of light utilizing acoustic radiation force with speckle pattern analysis.

In optical imaging, the depth and resolution are limited due to scattering. Unlike light, scattering of ultrasound (US) waves in tissue is negligible. Hybrid imaging methods such as US-modulated optical tomography (UOT) use the advantages of both modalities. UOT tags light by inducing phase change caused by modulating the local index of refraction of the medium. The challenge in UOT is detecting the small signal. The displacement induced by the acoustic radiation force (ARF) is another US effect that can be utilized to tag the light. It induces greater phase change, resulting in a stronger signal. Moreover, the absorbed acoustic energy generates heat, resulting in change in the index of refraction and a strong phase change. The speckle pattern is governed by the phase of the interfering scattered waves; hence, speckle pattern analysis can obtain information about displacement and temperature changes. We have presented a model to simulate the insonation processes. Simulation results based on fixed-particle Monte Carlo and experimental results show that the signal acquired by utilizing ARF is stronger compared to UOT. The introduced mean irradiance change (MIC) signal reveals both thermal and mechanical effects of the focused US beam in different timescales. Simulation results suggest that variation in the MIC signal can be used to generate a displacement image of the medium.

Are varus knees contracted? Reconciling the literature.

PURPOSE: There is direct literature conflict regarding coronal plane contracture or laxity in the end-stage varus osteoarthritic knee. Understanding the preoperative soft tissue status is important for optimizing the soft tissue envelope during total knee arthroplasty (TKA). METHODS: The lower limb was manipulated using computer navigation, prior to surgical releases, to allow the limb weight-bearing axis to pass through the knee centre in maximum extension and 20° of flexion. Coronal plane laxity was measured in 78 varus (-7.7° ± 2.8°) knees as medial and lateral displacement from this point and compared to published values for healthy subjects. RESULTS: Medial contracture was present in 12.8% (10/78) of the knees. Of these 10 knees, 5 displayed abnormal lateral laxity. Knees with a contracture in maximum extension also displayed a significant decrease ( p < 0.0001) in medial laxity at 20° of flexion compared to non-contracted knees. In maximum extension, 19.2% (15/78) of knees had abnormally increased lateral laxity, 10 did not have a medial contracture. The remaining five knees with increased lateral laxity or 6.4% (5/78) of the total cohort also displayed a medial contracture. Lateral laxity increased significantly with increasing varus deformity. Medial laxity did not significantly decrease when comparing varus deformity of 5-10° versus >10°. CONCLUSION: The majority of varus knees with deformity of up to 15° have neither a medial contracture nor abnormal lateral laxity when referenced to the individualized neutral axis of the knee. Surgical releases during TKA should be uncommon. Medial contracture when present is influenced by both posterior and medial structures. Lateral laxity is a more consistent feature of the varus knee. The patterns of contracture and laxity are variable with limited correlation to deformity.