title: Fast optical signal in visual cortex: Improving detection by General Linear Convolution Model.
abstract: In this study we applied the General Linear Convolution Model to fast optical signals (FOS). We modeled the Impulse Response Function (IRF) as a rectangular function lasting 30ms, with variable time delay with respect to the stimulus onset. Simulated data confirmed the feasibility of this approach and its capability of detecting simulated activations in case of very unfavorable Signal to Noise Ratio (SNR), providing better results than the grand average method. The model was tested in a cohort of 10 healthy volunteers who underwent to hemi-field visual stimulation. Experimental data quantified the IRF time delay at 80-100ms after the stimulus onset, in agreement with classical visual evoked potential literature and previous optical imaging studies based on grand average approach and a larger number of trails. FOS confirmed the expected contralateral activation in the occipital region. Correlational analysis between hemodynamic intensity signal, phase and intensity FOS supports diffusive rather than optical absorption changes associated with neuronal activity in the activated cortical volume. Our study provides a feasible method for detecting fast cortical activations by means of FOS.
authors.affiliation: Infrared Imaging Lab, ITAB - Institute for Advanced Biomedical Technologies, Foundation University G. d'Annunzio, Chieti, Italy; Department of Neurosciences and Imaging, University G. d'Annunzio, Chieti-Pescara, Italy.
authors.forename: Antonio Maria
authors.initials: AM
authors.lastname: Chiarelli
authors.affiliation: Infrared Imaging Lab, ITAB - Institute for Advanced Biomedical Technologies, Foundation University G. d'Annunzio, Chieti, Italy; Department of Neurosciences and Imaging, University G. d'Annunzio, Chieti-Pescara, Italy.
authors.forename: Assunta
authors.initials: A
authors.lastname: Di Vacri
authors.affiliation: Infrared Imaging Lab, ITAB - Institute for Advanced Biomedical Technologies, Foundation University G. d'Annunzio, Chieti, Italy; Department of Neurosciences and Imaging, University G. d'Annunzio, Chieti-Pescara, Italy.
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Romani
authors.affiliation: Infrared Imaging Lab, ITAB - Institute for Advanced Biomedical Technologies, Foundation University G. d'Annunzio, Chieti, Italy; Department of Neurosciences and Imaging, University G. d'Annunzio, Chieti-Pescara, Italy. Electronic address: a.merla@itab.unich.it.
authors.forename: Arcangelo
authors.initials: A
authors.lastname: Merla
mesh_terms: D000328:Adult; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D061848:Optical Imaging / Q000379:methods*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000502:physiology*
keywords: Fast optical signals; General Linear Model; Hemoglobin; Near infrared spectroscopy; Optical imaging