title: Holographically patterned activation using photo-absorber induced neural-thermal stimulation.
abstract: OBJECTIVE
  Patterned photo-stimulation offers a promising path towards the effective control of distributed neuronal circuits. Here, we demonstrate the feasibility and governing principles of spatiotemporally patterned microscopic photo-absorber induced neural-thermal stimulation (PAINTS) based on light absorption by exogenous extracellular photo-absorbers.
  
  
  METHODS
  We projected holographic light patterns from a green continuous-wave (CW) or an IR femtosecond laser onto exogenous photo-absorbing particles dispersed in the vicinity of cultured rat cortical cells. Experimental results are compared to predictions of a temperature-rate model (where membrane currents follow I ∝ dT/dt).
  
  
  RESULTS
  The induced microscopic photo-thermal transients have sub-millisecond thermal relaxation times and stimulate adjacent cells. PAINTS activation thresholds for different laser pulse durations (0.02 to 1 ms) follow the Lapicque strength-duration formula, but with different chronaxies and minimal threshold energy levels for the two excitation lasers (an order of magnitude lower for the IR system <50 nJ). Moreover, the empirical thresholds for the CW system are found to be in good agreement with detailed simulations of the temperature-rate model, but are generally lower for the IR system, suggesting an auxiliary excitation mechanism.
  
  
  CONCLUSIONS
  Holographically patterned PAINTS could potentially provide a means for minimally intrusive control over neuronal dynamics with a high level of spatial and temporal selectivity.
authors.affiliation: Faculty of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Nairouz
authors.initials: N
authors.lastname: Farah
authors.forename: Alaa
authors.initials: A
authors.lastname: Zoubi
authors.forename: Suhail
authors.initials: S
authors.lastname: Matar
authors.forename: Lior
authors.initials: L
authors.lastname: Golan
authors.forename: Anat
authors.initials: A
authors.lastname: Marom
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Butson
authors.forename: Inbar
authors.initials: I
authors.lastname: Brosh
authors.forename: Shy
authors.initials: S
authors.lastname: Shoham
mesh_terms: D000465:Algorithms; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology; D003198:Computer Simulation; D004574:Electromagnetic Fields; D005453:Fluorescence; D006696:Holography / Q000379:methods*; D007259:Infrared Rays; D007834:Lasers; D059906:Neuroimaging; D009474:Neurons / Q000502:physiology*; D062308:Optogenetics / Q000379:methods*; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature