# Technical note: contour plot visualization of the light adapted electroretinogram using a generalized additive model

## TL;DR

This paper introduces a new way to visualize eye response data using contour plots, showing differences in responses between children with autism and typically developing children.

## Contribution

A novel method using contour plots and Generalized Additive Models to analyze light-adapted electroretinogram data.

## Key findings

- Contour plots revealed reduced amplitude in the ascending limb of the b-wave for the ASD group.
- The GAM-based methodology allows simultaneous investigation of amplitude changes over time and flash strength.
- The approach provides a qualitative evaluation of mean amplitude differences concentrated on the b-wave.

## Abstract

To describe a new method to visualize the amplitude profile of light adapted ERGs as a series of contour plots in response to a Flash Strength series.

Light adapted ERGs from a dataset of n = 88 Autism Spectrum Disorder (ASD) and n = 70 typically developing Control participants were used incorporating 10 flash strengths ranging from 12 to 446 Troland seconds (Td.s). The region chosen for analysis included the baseline, a-wave and ascending limb of the b-wave and included n = 1736 control and n = 1300 ASD waveforms. A Generalized Additive Model (GAM) with complexity penalized tensor product splines was applied to the waveform intervals.

Contour plots derived from the ASD and Control groups revealed a pattern of reduced amplitude in the ascending limb of the b-wave for the ASD group. Representative responses were derived from the GAM model for discrete Flash Strengths to exemplify the changing profile of the ERG waveform. A contour plot of the derived z-scores provided a qualitative evaluation of the differences in the mean amplitudes which was concentrated on the b-wave.

The production of contour plots based on amplitude, time and Flash Strength with minimal a priori assumptions provide an additional approach to analyzing stimulus response data series and may support clinical applications. Additionally, the GAM-based methodology provides a tool for simultaneous investigation of the amplitude changes over time and Flash Strength which can be useful for theoretical purposes.

The online version contains supplementary material available at 10.1007/s10633-025-10078-3.