Optogenetic activation of visual thalamus generates artificial visual percepts.

The lateral geniculate nucleus (LGN), a retinotopic relay center where visual inputs from the retina are processed and relayed to the visual cortex, has been proposed as a potential target for artificial vision. At present, it is unknown whether optogenetic LGN stimulation is sufficient to elicit behaviorally relevant percepts, and the properties of LGN neural responses relevant for artificial vision have not been thoroughly characterized. Here, we demonstrate that tree shrews pretrained on a visual detection task can detect optogenetic LGN activation using an AAV2-CamKIIα-ChR2 construct and readily generalize from visual to optogenetic detection. Simultaneous recordings of LGN spiking activity and primary visual cortex (V1) local field potentials (LFPs) during optogenetic LGN stimulation show that LGN neurons reliably follow optogenetic stimulation at frequencies up to 60 Hz and uncovered a striking phase locking between the V1 LFP and the evoked spiking activity in LGN. These phase relationships were maintained over a broad range of LGN stimulation frequencies, up to 80 Hz, with spike field coherence values favoring higher frequencies, indicating the ability to relay temporally precise information to V1 using light activation of the LGN. Finally, V1 LFP responses showed sensitivity values to LGN optogenetic activation that were similar to the animal's behavioral performance. Taken together, our findings confirm the LGN as a potential target for visual prosthetics in a highly visual mammal closely related to primates.

Deletion of the Circadian Clock Gene Per2 in the Whole Body, but Not in Neurons or Astroglia, Affects Sleep in Response to Sleep Deprivation.

The sleep-wake cycle is a highly regulated behavior in which a circadian clock times sleep and waking, whereas a homeostatic process controls sleep need. Both the clock and the sleep homeostat interact, but to what extent they influence each other is not understood. There is evidence that clock genes, in particular Period2 (Per2), might be implicated in the sleep homeostatic process. Sleep regulation depends also on the proper functioning of neurons and astroglial cells, two cell-types in the brain that are metabolically dependent on each other. In order to investigate clock-driven contributions to sleep regulation we non-invasively measured sleep of mice that lack the Per2 gene either in astroglia, neurons, or all body cells. We observed that mice lacking Per2 in all body cells (Per2Brdm and TPer2 animals) display earlier onset of sleep after sleep deprivation (SD), whereas neuronal and astroglial Per2 knock-out animals (NPer2 and GPer2, respectively) were normal in that respect. It appears that systemic (whole body) Per2 expression is important for physiological sleep architecture expressed by number and length of sleep bouts, whereas neuronal and astroglial Per2 weakly impacts night-time sleep amount. Our results suggest that Per2 contributes to the timing of the regulatory homeostatic sleep response by delaying sleep onset after SD and attenuating the early night rebound response.

Gabapentin versus levodopa-c for the treatment of restless legs syndrome in hemodialysis patients: a randomized clinical trial.

To compare the efficacy of gabapentin and levodopa-c (Levodopa/Carbidopa) in reducing restless leg syndrome (RLS) symptoms and sleep problems in hemodialysis patients with RLS in a four-week randomized clinical trial. The diagnosis of RLS was made using the criteria of the International Restless Legs Study Group. Each subject completed three questionnaires: IRLS questionnaire, Pittsburgh Sleep Quality Index and Epworth sleepiness scale. After four weeks of washout period for previous treatments for RLS, subjects were randomly assigned to four weeks of gabapentin (200 mg) or levodopa-c (110 mg). After four weeks of therapy, the questionnaires administered at the outset of the study were re-administered. Both drugs were found effective for the management of RLS. But, the effect of gabapentin was more significant. Gabapentin significantly improved the IRLS total score (change from baseline to post-treatment ≈-17) compared with levodopa-c (change from baseline to post-treatment ≈-13) (P: 0.016). Regarding sleep parameters, levodopa improved sleep quality, sleep latency and sleep duration (P <0.0001). Gabapentin was also effective with respect to sleep parameters (P <0.0001). Our study shows that gabapentin is a safe effective therapy for RLS among hemodialysis patients. This medication may be considered as an alternative or additive treatment to current therapeutic remedies for hemodialysis patients with RLS.

Comparison of the Human Bone Matrix Gelatin (HBMG) with Autogenous Bone Graft in Reconstruction of the Parietal Bone Defects in Rat: A Histological and Radiographic Study.

BACKGROUND AND AIMS: Autogenous bone graft is commonly used for reconstruction of bone defects in routine surgical procedures. The complexity of producing bone grafts and their application has lead to the use of human bone matrix gelatin (HBMG). The present study was conducted to compare the efficacy of HBMG and autograft on the reconstruction of bone defects in rats. MATERIALS AND METHODS: In this cross-sectional, experimental study, two defects were put on left and right sides of parietal bone of rats. HBMG was placed randomly on defects of one side and autograft in the defects of the other side. All specimens were assessed and compared with each other according to histological and radiographic characteristics. Other assessments included amount and the rate of bone formation, inflammation signs, fibrosis tissue and cartilage formation and also radio-graphic characteristics of grafts, assessed by digital and film-based methods. Mann-Whitney U test was used for statistical analysis. RESULTS: The results showed a reduction of inflammation and an increase in new bone formation in both groups in 7, 14, 28 and 60 days after surgery. Bone formation with HBMG on day 24 was more than autograft. However, there was no sig-nificant difference between the groups on day 60. Superiority of digital method to film-based method of imaging was also observed. CONCLUSION: Although HBMG has the same efficacy as autograft, the rate of bone reconstruction with HBMG is higher. HBMG also induces focal, rather than peripheral, bone construction in the defect.