For the human observer, it can be difficult to follow the motion of small objects, especially when they move against background clutter. In contrast, insects efficiently do this, as evidenced by their ability to capture prey, pursue conspecifics, or defend territories, even in highly textured surrounds. We here recorded from target selective descending neurons (TSDNs), which likely subserve these impressive behaviors. To simulate the type of optic flow that would be generated by the pursuer’s own movements through the world, we used the motion of a perspective corrected sparse dot field. We show that hoverfly TSDN responses to target motion are suppressed when such optic flow moves syn-directional to the target. Indeed, neural responses are strongly suppressed when targets move over either translational sideslip or rotational yaw. More strikingly, we show that TSDNs are facilitated by optic flow moving counterdirectional to the target, if the target moves horizontally. Furthermore, we show that a small, frontal spatial window of optic flow is enough to fully facilitate or suppress TSDN responses to target motion. We argue that such TSDN response facilitation could be beneficial in modulating corrective turns during target pursuit.

Extracellular electrophysiology

The files show average responses during visual stimulation

“Facilitation of neural responses to targets moving against optic flow” -- Sarah Nicholas¹ and Karin Nordström^1,2

¹Flinders Health and Medical Research Institute, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia

²Department of Neuroscience, Uppsala University, Box 593, 751 24 Uppsala, Sweden

9 September 2021

This readme file describes the data sets (compiled in Prism 7.0c for Mac OS X, GraphPad Software, San Diego, USA) accompanying the above publication. For detailed descriptions of data acquisition and analysis refer to the materials and methods section of this publication. For further questions please contact: karin.nordstrom@flinders.edu.au

Data file: “Figure1.pzfz”

Data Table: “Figure 1D – Mean response across TSDNs”

Mean response from each unique neuron included in this study in response to a target moving across a white background (Group A) or a target moving across a stationary dot field (Group B), with each row containing data from the same neuron.

Data file: “Figure2 and Figure4.pzfx”

Data Table: “Figure 2D and Figure 4B - Normalized responses across TSDNs”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to a target traversing different types of optic flow as indicated by the group titles. The data shown in each sub column across the groups are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data Table: “Figure 2C and Figure 4A - Data from example TSDN recording”

Spike rate data shown for one example neuron in response to a target traversing different types of optic flow as indicated by the group titles. The data are displayed as mean and standard error of the mean (SEM) calculated over time (rows), with a 1 ms resolution after smoothing with a 20 ms square-wave filter.

Data Table: “Figure 2C and Figure 4A - Duplicated data for graphs”

“Data from Figure 2C and Figure 4A - Data from example TSDN recording” duplicated to assist in the production of graphs.

Data Table: “% change compared to response to target on stationary optic flow”

Percentage change, defined as (response_{experimental condition} – Response_{stationary control})/ Response_{stationary control}, from each neuron (columns Y1:Y12) in response to a target traversing different types of optic flow as indicated by the group titles. The data shown in each sub column across the groups are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data file: “Figure3.pzfx”

Data Table: “Figure 3 - Effect of Optic Flow Location”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to a target traversing varying types of optic flow covering different sections of the screen as indicated by the group titles. The data shown in each sub column across the groups are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data file: “Figure5.pzfx”

Data Table: “Figure 5A - Data from example TSDN recording”

Spike rate data shown for one example neuron in response to a target traversing different types of optic flow as indicated by the group titles. The data are displayed as mean and standard error of the mean (SEM) calculated over time (rows), with a 1 ms resolution after smoothing with a 20 ms square-wave filter.

Data Table: “Figure 5A - Duplicated data for graph”

Data from “Figure 5A - Data from example TSDN recording” duplicated to assist in the production of graphs.

Data Table: “Figure 5B - Horizontal and vertical targets on white background”

Mean response from each neuron in response to a horizontal (Group A) or vertical target (Group B) moving across a white background, with each row containing data from the same neuron.

Data Table: “Figure 5C - Horizontal Target”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to a horizontal target traversing varying types of optic flow as indicated by the group titles. The data shown in each sub column across the groups and both data sets, “Figure 5C - Horizontal Target” and “Figure 5D - Vertical Target”, are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data Table: “Figure 5D - Vertical Target”

The data set shows normalized responses to vertical target motion (the mean response from each neuron to the experimental condition divided by its own mean response to vertical target motion over a white background). The data show the response to a horizontal target traversing varying types of optic flow as indicated by the group titles. The data shown in each sub column (Y1:Y8) of each group and of both data sets “Figure 5C - Horizontal Target” and “Figure 5D - Vertical Target” are repeated measures from the same neuron. 

Data file: “Figure6.pzfx”

Data Table: “Figure 6A - Dot density 10 dots/m3”

Data Table: “Figure 6B - Dot density 50 dots/m3”

Data Table: “Figure 6C - Dot density 100 dots/m3”

Data Table: “Figure 6D - Dot density 200 dots/m3”

Data Table: “Figure 6E - Dot density 300 dots/m3”

Data Table: “Figure 6F - Dot density 500 dots/m3”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to a target traversing varying types of optic flow as indicated by the group titles. Each data table (Figure 6A – Figure 6F) corresponds to a variation in the dot density of the dot field used, as indicated in the name of the data table. The data shown in each sub column across the groups and data tables are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data Table: “Figure 6 Data rearranged for 2-way ANOVA”

Data duplicated and rearranged for all other Figure 6 data tables to allow for statistical analysis.

Data file: “Figure7.pzfx”

Data Table: “Figure 7 - Models and TSDN Data”

Predicted outputs from models compared to TSDN responses, as indicated by group titles, to a leading OFF edge, trailing ON edge or a complete black target. Shown as the response of each neuron, or each model, after normalizing the data to its own sum. Sub columns in Group C represent data from the same neuron.

Data file: “SI_Figure1.pzfx”

Data Table: “Percentage of responses > max spontaneous response (white background alone)”

Percentage of trials in which the neurons’ response to the stimulus shown was greater than the same neurons’ response to a white background. Stimulus type is indicated by the group titles. Rows represent data from the same neuron.

Data Table: “Mean of normalized responses > max spontaneous response (white background alone)”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to the stimulus type indicated by the group titles. Only data from trials in which the neurons’ response to the stimulus shown was greater than the same neuron’s response to a white background were included. Blank cells indicate no trials for this neuron met the criteria for this stimulus type. Rows represent data from the same neuron.

Data file: “SI_Figure2.pzfx”

Data Table: “SI Figure 2C”

Slope constant (alpha) calculated from 10 sparse dot field examples for each of the 6 dot densities tested.

Data Table: “SI Figure 2C - Curve Fit”

Distribution of slope constants across natural scenes.

Data Table: “SI Figure 2D”

RMS contrast calculated from 10 sparse dot field examples for each of the 6 dot densities tested.

Data Table: “SI Figure 2D - Curve Fit”

Distribution of RMS constants across natural scenes.

Data Table: “SI Figure 2E”

Spontaneous firing rate and neural response of optic flow sensitive descending neurons in response to optic flow at 6 different dot densities. The data shown in each sub column across the groups and dot densities are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data file: “SI_Figure3.pzfx”

Data Table: “SI Figure 3 - Effect of Preceding and Concurrent Optic Flow”

The data set shows normalized responses (the mean response from each neuron to the experimental condition divided by its own mean response to a target moving over a white background). The data show the response to a target traversing different types of optic flow with varying presentation times as indicated by the group titles. The data shown in each sub column across the groups are repeated measures from the same neuron (e.g. Y1 Group A is from the same neuron as Y1 Group B). 

Data Table: “Data from SI Figure 3B and C rearranged for 2way ANOVA”

Data Table: “Data from SI Figure 3D and E rearranged for 2way ANOVA”

Data duplicated and rearranged from “SI Figure 3 - Effect of Preceding and Concurrent Optic Flow” to allow for statistical analysis.