On-off units in the first optic chiasm of the blowfly II. Spatial properties

Abstract

Abstract.We recorded from the spiking on-off unit in the first optic chiasm (between lamina and medulla) in the blowfly Calliphora vicina, and investigated its spatial properties. The receptive field extends over (11.4+ 0.9) ~ horizontally and (8.7+0.6) ~ vertically, i.e. about 7 by 5 interommatidial angles. The line spread function of the on-off unit -calculated from its response to moving sinusoidal gratings -has a half-width of (2.3 + 0.2) ~ This half-width is slightly broader than that of the photoreceptor. Lateral inhibition occurs when two different areas of the receptive field are stimulated simultaneously. Fast temporal adaptation (i.e. adaptation to trains of short light pulses) takes place independently in different areas of the receptive field.

Correlation between OFF and ON Channels Underlies Dark Target Selectivity in an Insect Visual System

“…Data from downstream Vertical and Horizontal System neurons in dipteran flies support a 2-detector EMD (see Fig. 1B) in which ON-ON and OFF-OFF information is correlated locally in parallel pathways, which are then summed (Eichner et al, 2011;Joesch et al, 2013).…”

“…The next model stage includes strong surround antagonism with ON channels inhibiting ON and OFF inhibiting OFF, as clearly observed in blowfly RTCs (Jansonius and van Hateren, 1993). This "like" channel inhibition is essential to suppress responses for features that are extended along the axis orthogonal to their motion (i.e., the "hypercomplex property" selectivity for small objects vs extended bar features) (Nordström and O'Carroll, 2009).…”

Neuromorphic Modeling of Moving Target Detection in Insects

“…This model is illustrated below in schematic form in Figure In this model, the signal path leading to the rectifying transient cell is divided into distinct 'ON' and 'OFF' channels at a relatively early stage. In this regard, it is similar to a detailed model for the lamina on-off cell (Sarakaya, Wang, and 6gmen, 1998) but differs from other prior models for RTCs (Jansonius and van Hateren, 1993;Osorio, 1991), which have placed rectification later in the processing. This assumption predicts the existence of two populations of lamina neurons to carry the ON and OFF signals;Sarakaya et al (1998) suggest that these may be two distinct types of lamina amacrine cells, but we note that the lamina monopolar cells (LMCs) and the 'sustaining' neurons (tentatively associated with lamina L5 cells, Jansonius and van Hateren (1993)) have transient and opposite-polarity responses to luminance changes, and could thus be part of the two pathways.…”

“…Initial modeling efforts were based on previously reported results (Jansonius andvan Hateren, 1991, 1993;Osorio, 1987) and predated our own electrophysiological work on such cells. We developed a basic model for the lamina neurons of this class (the 'on-off' cells of Jansonius andvan Hateren, 1991, 1993), focusing primarily on the full-wave rectifying nonlinearity and temporal characteristics (i.e., fast adaptation). Separate ON and OFF processing channels with independent adaptation were proposed, in work done primarily by the industrial partner.…”

“…We performed a limited number of simulations in which these parameters and the nonlinear filter parameters were varied, but did not do any systematic optimization of the model. (Shoemaker, Wiederman) The class of rectifying transient neurons includes neurons that in the past have been recorded from the first optic chiasm, representing the axons of afferent neurons projecting from lamina to medulla (in fly, Jansonius andvan Hateren, 1991, 1993a), and from cells in or projections into the medulla (in locust, Osorio, 1987Osorio, , 1991. Recordings from blowflies in the O'Carroll laboratory appear to be from intrinsic medulla neurons, although it is possible they may be from cells projecting to or through the medulla from elsewhere (i.e., from laminar RTCs).…”