Supplementary document for Aberration-free holographic microscope for simultaneous imaging and stimulation of neuronal populations - 6610401.pdf

Supplementary documen

Supplementary document for Aberration-free holographic microscope for simultaneous imaging and stimulation of neuronal populations - 6512517.pdf

Supplemental figures and tex

Cortical ensembles selective for context

Neural processing of sensory information is strongly influenced by context. For instance, cortical responses are reduced to predictable stimuli, while responses are increased to novel stimuli that deviate from contextual regularities. Such bidirectional modulation based on preceding sensory context is likely a critical component or manifestation of attention, learning, and behavior, yet how it arises in cortical circuits remains unclear. Using volumetric two-photon calcium imaging and local field potentials in primary visual cortex (V1) from awake mice presented with visual "oddball" paradigms, we identify both reductions and augmentations of stimulus-evoked responses depending, on whether the stimulus was redundant or deviant, respectively. Interestingly, deviance-augmented responses were limited to a specific subset of neurons mostly in supragranular layers. These deviance-detecting cells were spatially intermixed with other visually responsive neurons and were functionally correlated, forming a neuronal ensemble. Optogenetic suppression of prefrontal inputs to V1 reduced the contextual selectivity of deviance-detecting ensembles, demonstrating a causal role for top-down inputs. The presence of specialized context-selective ensembles in primary sensory cortex, modulated by higher cortical areas, provides a circuit substrate for the brain's construction and selection of prediction errors, computations which are key for survival and deficient in many psychiatric disorders

Neuronal photoactivation through second-harmonic near-infrared absorption by gold nanoparticles

Zapping neurons to life with infrared light Neuronal impulses can be generated by aiming a near-infrared laser beam at gold nanoparticles precisely tethered to brain cells. Wieteke de Boer and Jan Hirtz of the NeuroTechnology Center at Columbia University, USA, and colleagues developed the technique, which could provide a nontoxic, nongenetic alternative to commonly used optical methods for activating brain cells. They tested it in live mouse brain tissue, and also used it to induce movement in a tiny freshwater animal called Hydra vulgaris. The authors demonstrate the potential for targeted stimulation of neurons through the nonlinear absorption of light by nanoparticles. By using low-power short-pulsed near-infrared excitation, the photodamage of the tissue is minimal. The approach shows promise for application in biological systems and for future treatments of neurological and mental disorders

Germline quality control: eEF2K stands guard to eliminate defective oocytes

The control of germline quality is critical to reproductive success and survival of a species; however, the mechanisms underlying this process remain unknown. Here, we demonstrate that elongation factor 2 kinase (eEF2K), an evolutionarily conserved regulator of protein synthesis, functions to maintain germline quality and eliminate defective oocytes. We show that disruption of eEF2K in mice reduces ovarian apoptosis and results in the accumulation of aberrant follicles and defective oocytes at advanced reproductive age. Furthermore, the loss of eEF2K in Caenorhabditis elegans results in a reduction of germ cell death and significant decline in oocyte quality and embryonic viability. Examination of the mechanisms by which eEF2K regulates apoptosis shows that eEF2K senses oxidative stress and quickly downregulates short-lived antiapoptotic proteins, XIAP and c-FLIPL by inhibiting global protein synthesis. These results suggest that eEF2K-mediated inhibition of protein synthesis renders cells susceptible to apoptosis and functions to eliminate suboptimal germ cells