• If infant-like: stronger responses to fast, linear flows
• If adult-like: stronger responses to slow, radial flows

Methods

• Time-varying optic flow patterns
• Steady-state visual evoked potentials (SSVEPs)
  • Event-related EEG technique
  • Focus on phase-locked, low-order harmonics
• n=29 4-8 year-olds

(Gilmore, Thomas, & Fesi, under review)

https://databrary.org/volume/75

https://github.com/gilmore-lab/gilmore-thomas-fesi-2015

• Modulate coherence/signal-to-noise ratio (SNR), 100%/0%
• Modulation frequency 1.2 Hz (1F1), dots update rate 24 Hz (1F2)
• 3 Patterns {radial, rotation, translation} x 3 Speeds {2, 4, 8 deg/s}

• Fourier analysis (frequency domain)
  • generates complex domain (real, imaginary) components
  • time-varying signals have amplitude, phase
• Codepen Demo

• Use mixed effects MANOVA to capture phase, amplitude
  • Pattern (radial, rotation, linear) and Speed (2, 4, 8 deg/s) as fixed effects
  • Individual means as random factors
• Analyze channels independently

• Highly responsive channels over right lateral cortex
• Radial & rotation >> translation
• Amplitude and phase differences

• Highly responsive channels over medial cortex.
• Speed, but not pattern tuned, 2 < 4 < 8 deg/s.
• Amplitude and phase differences.

• Anatomical separation of responses
  • speed (medial)
  • vs. pattern (lateral)
• Radial & rotation != translation, phase and amplitude
• Speed tuning

• Children adult-like in some respects
  • Lateral "pattern" responses @ 1F1
  • Medial "speed" responses @ 3F1 and 1F2
• Activate smaller # of channels
• Unilateral