Matlab 2007b

The stimuli had previously been used in other studies, and a complete description of them can be found elsewhere (Petrini et al., 2009a (link),b (link); Love et al., 2013 (link)). They comprised dynamic audiovisual movies (3 s) containing the point-light representation of a drummer playing a swing groove at 120 beats per minute, with an accent on the second beat (Figure 1). Audio and visual cues were shifted relative to each other to produce stimuli with different cue onset asynchrony (COA). The video was shifted to begin either after the audio (−333, −267, −200, −133, and −67 ms) or before the audio (+333, +267, +200, +133, and +67 ms), producing a total of 10 asynchronous stimuli to be used in the pre-fMRI experiment. Negative and positive numbers will be used to refer to audio-leading and video-leading COA levels respectively, and 0 COA will refer to the synchronous condition. To prevent participants from having to stay in the MRI scanner for an uncomfortably long time only 4 COA levels were used during the fMRI experiment: two asynchronous (−333, +333 COA) and two “synchronous” (0 COA and the individually defined PSS). The −333, 0 and +333 COA conditions are provided as Supplementary Videos 1–3, respectively.
Stimuli were presented using MATLAB 2007b (MATHWORKS Inc., Natick, MA) and the Psychophysics Toolbox (Brainard, 1997 (link); Pelli, 1997 (link)).

The AV-SOA of the separate audio and video files was manipulated using Psychophysics Toolbox version 3 (PTB-3) under Matlab 2007b (MathWorks Inc., MA, USA). Visual stimuli (size 8.89° * 7° visual angle) were projected using a CRT monitor (Sony Trinitron, Tokyo, Japan) at refresh rate of 100 Hz, and subjects' heads were stabilized using a chin rest. Auditory stimuli were presented at ~75 dB SPL via headphones.

Mean neurite lengths were determined from the normal size high resolution neurite-enhanced pictures taken for morphology analyses (20x magnification) using an image analysis app (Matlab Image Processing Toolbox; MatLab 2007b, Mathworks, USA). Briefly, neurite length was defined as the Euclidean distance in pixels or a combination of Euclidean distances between the cell body and the end of a neurite. The longest path was always chosen when a neurite had several branches. The length in pixels was then calibrated based on the length bar provided by the microscope image treatment software (AxioVision LE, Carl Zeiss, DE). For each experimental condition, 15 to 30 neurites were measured for each picture (4 × 10⁻³ cm²) and at least 5 pictures were analyzed per condition performed. Those steps were done three independent times in duplicate. The mean neurite length for each picture analyzed within a replicate was weighted by the number of measurement taken. For each independent experiment, the mean was calculated as the weighted mean (relative to the inverse of the variance) of each replicate. Finally, the overall mean was calculated as the weighted mean (relative to the inverse of the variance) of each of the three independent experiments. Overall, a total of at least 300 neurite length measurements were obtained for each experimental condition.

Basically, Euclidian distances between given macroanatomical landmarks were used to assess their topological relationship (indicated as “direct distance” in Table 1). Ratios between a set of two given landmark distances were calculated. Specific macroanatomical landmarks used for analyses are depicted in Figure 1. When junctions of sulci and fissures were detected on slice images, they tended to be located beneath the lateral cortical surface. To avoid variability in depth direction, their locations were adjusted to the cortical surface. Macroanatomical structures around the medial cortical surface were projected onto the sagittal plane for analysis. To analyze the height of macroanatomical structures, they were projected onto the coronal plane. Correlation analyses were performed between a given ratio for topological relationship and age of infant (months). All calculations were performed using a numerical processing software package, Matlab 2007b (MathWorks).

We presented stimuli generated with Psychophysics Toolbox 3 [23 (link)] running under Matlab 2007b (Mathworks inc.) on a 60 Hz Sanyo LCD projector, on which participants viewed alternating blocks of ambiguous and corresponding replay stimulation. In ambiguous blocks, we displayed two identical moving Lissajous figures formed by the intersection of two perpendicular sinusoids (x(t) = sin(3t) and y(t) = sin(6t + δ); with δ increasing from 0 to 2π), separately to the two eyes. In replay blocks, a disambiguated version of the Lissajous figure mimicked the perceptual time-course participants had experienced during the preceding ambiguous block. To this end, the two dichoptically presented Lissajous figures were phase-shifted against each other by an offset of 0.04°. This disparity cue was used to disambiguate the stimulus, biasing participants perceived direction of rotation in the direction of the phase shift. All stimuli subtended 2.05° visual angle.
We achieved dichoptic stimulation by placing a custom build cardboard divider between the mirror attached to the head-coil and the screen at the end of the scanners bore [24 (link)]. Participants wore prism glasses to facilitate fusion between to two eyes. All screens contained a fixation mark at the center and fusion frames surrounding the stimuli.