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How the brain differentiates human and monkey faces: Neuromagnetic evidence from spatiotemporal dynamics
Emi Yamada1, Akinori Takeda2, Hisato Nakazono3
1Department of Clinical Neurophysiology, Neurological Institute, Faculty of Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan; Department of Linguistics, Faculty of Humanities, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Investigating face processing, this study reveals that inverted human and animal faces are processed differently. Upright faces activate wider brain areas, suggesting distinct neural mechanisms for face orientation.
Area of Science:
- Cognitive Neuroscience
- Visual Perception
- Neuroimaging
Background:
- Face recognition is crucial for non-verbal communication.
- Neural markers like N170/M170 are key to face processing.
- Previous studies show orientation and species affect N170/M170, but mechanisms are unclear.
Purpose of the Study:
- To clarify the spatiotemporal dynamics of processing inverted human and animal faces.
- To investigate how face orientation and species interact in neural face processing.
Main Methods:
- Magnetoencephalography (MEG) with a 306-channel system was used.
- Face-selective responses (M170) were recorded for upright and inverted human and monkey faces.
- Both sensor-level and source-level analyses were performed.
Main Results:
- Sensor analysis indicated increased M170 latency and amplitude for inverted human and upright animal faces.
- Source analysis revealed upright faces activated wider ventral and dorsal visual areas compared to inverted faces, irrespective of species.
- Face orientation differentially modulated the anterior fusiform gyrus (FG) for both human and animal faces.
Conclusions:
- Spatiotemporal dynamics of face processing differ based on orientation, independent of face category.
- The fusiform gyrus (FG) shows differential modulation by orientation but may not significantly contribute to scalp-recorded M170 modulation.
- Inverted human and animal faces are processed through distinct neural mechanisms.
