Abstract
The steady-state visual evoked potential (SSVEP) is a periodic EEG response elicited by periodic visual stimulation (Regan, 1966). The amplitude of SSVEP is reduced in response to repetitions of the same face compared to presentations of different faces (e.g., Rossion et al., 2012). Although the SSVEP technique is an ideal tool to study the sensitivity to face discrimination, it is unknown whether this effect is specific to faces or can be generalized to non-face objects. Here we tested the SSVEP response to face and bird stimuli at 4 Hz of stimulation frequency in 11 bird novices. Face and bird stimuli were gray-scaled and equated for luminance. Bird stimuli were selected from exemplars from different species. All trials started with the presentation of an identical stimulus for 15 seconds followed by 75 seconds of presentation in which the identity of the stimuli either remained the same or changed at every cycle. The stimuli were presented in varying sizes to control for adaptation to low-level properties. Fourier Transform was applied to EEG recordings (32 channels) from the 18th to 67th second of presentation (frequency resolution: 0.02 Hz). Replicating previous observations, responses at both the fundamental frequency (4 Hz) and the second harmonics (8 Hz) were larger for different faces than the same face condition at occipito-temporal electrode sites. However, there was no difference at 4 Hz for bird stimuli, and only a weak effect at the second harmonics (8 Hz). This effect is not attributable to image similarity because physical differences between bird stimuli were larger than face stimuli. These results indicate that the SSVEP is sensitive to the identity differences in faces, but not to identity differences in non-face objects, such as birds.
Meeting abstract presented at VSS 2013