Linearity and Non-linearity in the Retinal Light Response
{'Code': '08090200', 'Directorate': {'Abbreviation': 'BIO', 'LongName': 'Direct For Biological Sciences'}, 'Division': {'Abbreviation': 'IOS', 'LongName': 'Division Of Integrative Organismal Systems'}}
{'SignBlockName': 'Christopher Platt', 'PO_EMAI': None, 'PO_PHON': None}
This continuing grant for three years is on mechanisms of visual                response in the eye.  The retina of the eye is the sensory tissue               containing the photoreceptor cells connected to several kinds of                nerve cells.  The simplest subunit of human visual processing is the            response from a uniform patch of retina illuminated when it is                  stimulated by light.   This response to light is not simple, but                subject to a sequence of events which can be modelled mathematically            as linear and non-linear processes.  Over the past century, a set of            psychophysical "laws" have been established to relate dynamic visual            responses to stimulus changes over time.  But some of these laws imply          simple linear addition of stimulus effects, and some imply that the             effects cannot be added linearly.                                                                                                                               This project will try to clarify what kinds of processing in                    the retina could satisfy all of these laws under non-extreme                    conditions.  The question of linearity of the response at each                  level of the visual system, and conditions under which the                      linearity fails have complementary significance un unravelling                  the sequence of visual processing.  The general approach is to                  use the nonlinear stages as markers to determine the response                   dynamics before and after each such marker.  Human observers will               be tested by measuring their perception of the intensity of                     flickering lights, while varying the intensity and duration of                  the stimulus.  The first set of experiments will examine the                    linearity of the mechanism of phototransduction, in which the                   light signal is first converted to a neural response signal.                    intensity levels high enough to saturate the system will be used                to explore the time course of photochemical reactions preceding                 the saturation.  The second experiments will test how non-                      linearity applies to the change in threshold for perception of a                test pulse when there is a large abrupt "step" change in light                  intensity.   Analysis of the data will include mathematical                     modelling of the functions describing the stimulus-response                     relationships.                                                                                                                                                  This integrated approach is a novel and very sophisticated                      one, with a strong theoretical component.  The results should                   have impact on visual research in many areas, and on models of                  information processing in other systems.
{'FirstName': 'Christopher', 'LastName': 'Tyler', 'PI_MID_INIT': 'W', 'PI_SUFX_NAME': None, 'PI_FULL_NAME': 'Christopher W Tyler', 'EmailAddress': 'cwt@ski.org', 'NSF_ID': '000096707', 'StartDate': '08/01/1987', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'Smith-Kettlewell Eye Research Foundation', 'CityName': 'SAN FRANCISCO', 'ZipCode': '941151813', 'PhoneNumber': '4153452035', 'StreetAddress': '2318 FILLMORE ST', 'StreetAddress2': None, 'CountryName': 'United States', 'StateName': 'California', 'StateCode': 'CA', 'CONGRESSDISTRICT': '11', 'CONGRESS_DISTRICT_ORG': 'CA11', 'ORG_UEI_NUM': 'VT22KLLMNQL6', 'ORG_LGL_BUS_NAME': 'THE SMITH-KETTLEWELL EYE RESEARCH INSTITUTE', 'ORG_PRNT_UEI_NUM': 'VT22KLLMNQL6'}
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{'Code': '1185', 'Text': 'SENSORY SYSTEMS'}
{'url': 'https://www.nsf.gov/awardsearch/download?DownloadFileName=1987&All=true', 'xml': '8711217.xml'}