title: Optical monitoring of neuronal activity at high frame rate with a digital random-access multiphoton (RAMP) microscope.
abstract: Two-photon microscopy offers the promise of monitoring brain activity at multiple locations within intact tissue. However, serial sampling of voxels has been difficult to reconcile with millisecond timescales characteristic of neuronal activity. This is due to the conflicting constraints of scanning speed and signal amplitude. The recent use of acousto-optic deflector scanning to implement random-access multiphoton microscopy (RAMP) potentially allows to preserve long illumination dwell times while sampling multiple points-of-interest at high rates. However, the real-life abilities of RAMP microscopy regarding sensitivity and phototoxicity issues, which have so far impeded prolonged optical recordings at high frame rates, have not been assessed. Here, we describe the design, implementation and characterisation of an optimised RAMP microscope. We demonstrate the application of the microscope by monitoring calcium transients in Purkinje cells and cortical pyramidal cell dendrites and spines. We quantify the illumination constraints imposed by phototoxicity and show that stable continuous high-rate recordings can be obtained. During these recordings the fluorescence signal is large enough to detect spikes with a temporal resolution limited only by the calcium dye dynamics, improving upon previous techniques by at least an order of magnitude.
authors.affiliation: Laboratoire de Neurobiologie, CNRS UMR 8544, Ecole Normale Supérieure, 46 rue d'Ulm 75005, Paris, France.
authors.forename: Yo
authors.initials: Y
authors.lastname: Otsu
authors.forename: Volker
authors.initials: V
authors.lastname: Bormuth
authors.forename: Jerome
authors.initials: J
authors.lastname: Wong
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mathieu
authors.forename: Guillaume P
authors.initials: GP
authors.lastname: Dugué
authors.forename: Anne
authors.initials: A
authors.lastname: Feltz
authors.forename: Stéphane
authors.initials: S
authors.lastname: Dieudonné
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D002525:Cerebellar Cortex / Q000166:cytology / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology; D049229:Dendritic Spines / Q000502:physiology / Q000648:ultrastructure; D005456:Fluorescent Dyes / Q000592:standards; D019044:Image Cytometry / Q000295:instrumentation / Q000379:methods; D036641:Microscopy, Fluorescence, Multiphoton / Q000295:instrumentation / Q000379:methods*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009482:Neurophysiology / Q000295:instrumentation / Q000379:methods*; D055095:Optics and Photonics / Q000295:instrumentation*; D009924:Organ Culture Techniques; D011689:Purkinje Cells / Q000166:cytology / Q000502:physiology; D017966:Pyramidal Cells / Q000166:cytology / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013194:Staining and Labeling / Q000379:methods; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D005456:Fluorescent Dyes