Psychtoolbox

The experiment was run in Matlab Psychtoolbox (Matlab R2015b 64-bit, Psychtoolbox 3.0.11, MathWorks). The method-of-adjustment task used was developed by Manning et al. (2017 (link)) for studying the susceptibility to visual illusions in autistic children. The task was adapted for the current research (e.g. number of trials, procedure).

We performed widefield epifluorescence imaging of jGCaMP7f^{47 (link)} to generate a retinotopic map that was used to determine the two-photon imaging field of view for the PPC as previously described^{48 (link)}. In brief, we excited jGCaMP7f with blue light (452–486 nm band-pass filtered, Thorlabs) and filtered green emitted light (505–545 nm band-pass filtered, Thorlabs) that was imaged with a CMOS camera (acA1920-155um, Basler) with a field of view covering the entire cranial window. Mice were anaesthetized under 1% isoflurane. Visual stimuli were coded with Psychtoolbox (MATLAB, MathWorks), presented on a 27 inch monitor, and consisted of a spherically corrected bar 12.5° in width moving at 10° s⁻¹ horizontally or vertically in either direction. The bar was patterned with a 3 Hz alternating black and white checkered pattern. Data were processed as previously described^{49 (link),50 (link)} using a temporal Fourier transform to extract responses to horizontal and vertical bar positions (since visual stimuli were presented periodically in time), creating horizontal and vertical response maps. The field sign was computed as the sine of the angle between the gradient of the horizontal and vertical maps. Fields of view for the PPC were centred approximately at (−1.7 (ML), −2 mm (AP) from bregma) as in previous studies^{48 (link),51 (link)}.

Novel objects were created using Matlab 2017b (MathWorks, Natick, MA) with Psychtoolbox. The gratings were generated in Python using the Psychopy version 1.9 toolbox (Peirce, 2009). For the testing procedure, a Dell PC running Matlab 2016b and Psychtoolbox was used to conduct the experiment. Subjects were placed in front of a DELL monitor with a 1600x900 resolution at 70 Hz. The training paradigm was made with Unity^® (version 2017.2.03f). For the training procedure, subjects used their personal computer running on Windows. For the course of the experiment, subjects were asked to uphold an upright position and to limit forward and backward movements from the screen during testing and training.