Poster template by ResearchPosters.co.za
Fast Periodic Visual Stimulation EEG as a Measure for Perceptual Categorization and Discrimination
Jaana Van Overwalle1,3, Charlotte Buhre1, Stephanie Van der Donck2,3,
Sander Van de Cruys1,3, Bart Boets2,3 & Johan Wagemans1,3
1 Brain & Cognition Unit, KU Leuven, Belgium; 2 Center for Developmental Psychiatry, KU Leuven, Belgium;
3 Leuven Autism Research (LAuRes), KU Leuven, Belgiuim
• Oddball paradigm: Objects (O) are presented at 6 Hzbase rate and give neural responses at 6 Hz. Faces (F) are inserted at 1.2 Hz oddball rate. When these faces (F) are perceived as different from the objects (O), they elicit responses at 1.2 Hz and additional oddball harmonics (n x 1.2 Hz).
• Sweep paradigm: Extension of the oddball paradigm. The oddball is presented at a specific frequency while it is being parametrically varied (‘‘swept’’).
• Advantages: The response can thus be measured implicitly (i.e. without an explicit behavioral task) and objectively (since it occurs at a predefined frequency).
• Inanimate-Inanimate switch (1)
• Animate-Animate switch (1)
• Inanimate-Animate switch (3)
EEG FFT
Candle-Bottle (CB)
Penguin-Child (PC)
Peacock-Truck (PT)
Watch-Seahorse
(WS)
Church-Duck (CD)
5 sequences of black-and-white stimuli morphed from one entity to another in 10 equally spaced steps 11 morph levels per morph sequence (Hartendorp et al., 2010)
• Study 1: Categorization• Participants: 8 healthy adults• Sweep paradigm across the 11 morph levels• Implicit versus explicit EEG• 2-AFC categorization task
• Study 2: Discrimination• Participants: 18 healthy adults• Comparing 7 pairs (small steps e.g. L1-L3) and 6 pairs
(big steps e.g. L1-L4) across the morph sequence• Oddball versus sweep paradigm • 2-AFC discrimination task
Liu-Shuang et al., 2015
Study 1: Categorization
Part 1: FPVS EEG (n=18) Part 2: Behavior (n=17) Part 3: Consistency of the FPVS EEG
Study 2: Discrimination
Every day we receive plenty of visual information. We react efficiently on this input via categorization. Categorization is an automatic and implicit process, which enables us to respond adaptively to similar exemplars of a category. Although this is an implicit process, research has mainly investigated categorization explicitly. Therefore, using Fast Periodic Visual Stimulation (FPVS) EEG we want to develop an implicit measure to investigate this process and its neural correlates.
Main Goal: developing an implicit measure for categorization• Taking into account complementary processes such as discrimination• Correlating to explicit behavior
Secondary Goal: further investigating…• Differences between the naturally categorically perceived stimuli• The robustness of the FPVS EEG technique: repeated measures and individual differences
Part 1: Sweep FPVS EEG (n=8) Part 2: Behavior (n=8) Part 3: Consistency of the FPVS EEG
Oddball FPVS (n=10) Sweep FPVS (n=8)
Small
Big
Oddball FPVS: different measures
Sweep FPVS: different measures
Background
Stimuli
Oddball & Sweep FPVS Paradigm
Experimental Paradigm
European Conference on Visual Perception 2018Email: [email protected]
Conclusions
Main Goal: developing an implicit measure for categorization
The implicit EEG and explicit behavior measures for categorization and discrimination seem to correlate well. However, responses should be quantified further to make any conclusions.
Secondary Goal: further investigating robustness and inter-stimulus differences
The results show a difference in amplitude and consistency of the EEG signal for the different stimuli. In future research comparing responses between patients and healthy individuals, only the stimuli eliciting robust responses will be used.
Different measures (ep1-ep3 implicit + ep4 explicit)
Different individuals