Qiufang Fu, Yong-Jin Liu, Wenfeng Chen, Xiaolan Fu. 
Time course of natural scene categorization in human brain: simple line-drawings vs. color photographs. 
Journal of Vision, Vol. 13, No. 9, article. 1060; doi:10.1167/13.9.1060, 2013. 

Abstract

Human beings are very quick and efficient at categorizing nature scenes. 
Recent functional MRI studies found that the neural activation in response 
to line-drawings was similar to color photographs (e.g., Walter et al., 2011). 
However, it remains unclear whether the time course of braining activity 
was similar to the different images. The present study was aimed to 
investigate how the nature scene categorization of line-drawings and 
color photographs was reflected in event-related potentials (ERPs). 
Color photographs and line-drawings of six natural scene categories 
(beaches, city streets, forests, highways, mountains and offices) were 
adopted as stimuli, which were first used by Walter et al. (2011). All 
the images were resized to a resolution of 320 * 240 pixels. Each of 
them was flashed for 13 ms, and then followed by 100 ms of mask stimuli 
and 500 ms of a blank. The stimulus onset asynchrony (SOA) between the 
image and the mask was 13, 26, 40 or 213 ms. On each trial, participants 
were asked to report the scene category by pressing a key after the blank.
Each participant was tested for 10 blocks of 96 trials. ERPs were recorded 
during the experiment. The behavioral results showed that the accuracy was 
higher for line-drawings than color photographs when SOA was 13 ms, but was 
lower when SOA was greater than 13 ms. Importantly, the ERP results revealed 
that a more negative N170 in occipital electrodes and a more positive P2 in 
frontocentral electrodes were elicited by incorrect than correct categorization 
of color photographs, whereas a more positive P1 in occipital electrodes and 
a more negative N2 in frontocentral electrodes were led to by incorrect than 
correct categorization of line-drawings. These findings help to understand 
the role of color in rapid scene categorization and how human brain 
categorizes different visual stimuli.