Neural Information Integration: Key Factor to Conscious Face Perception

Rebecca Lewis January 08, 2013

The human brain has an extraordinary capability to process varying sensory input into recognisable images. For instance, it can detect and identify object categories in complex natural scenes without any effort. But according to the researchers from the University of Amsterdam, category tuning is not enough to achieve conscious recognition of objects.

Using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), the researchers found that even though both the visible and invisible faces produce similar category-selective responses in the brain, only the visible images caused widespread response enhancement and changes in the neural oscillatory synchronization. According to them, the pattern of neural activities evoked by visible faces can be used to decode or identify the invisible faces, and vice versa.

Their findings, which were published in the Proceedings of the National Academy of Sciences, reveal that sustained neural integration is critical to conscious face perception.

Arriving at this conclusion was not easy. The researchers faced a series of challenges in conducting their study. In his interview with Medical Xpress, Dr. Johannes J. Fahrenfort said there were practical challenges they had to deal with. For instance, they had to use a special apparatus that allowed them to adjust the position of the beamers in all directions, millimetre by millimetre. They also had to use a stimulus sequence that made objects that were naturally visible completely invisible in controlled conditions. They also had issues with analysing the data results, Fahrenfort added. He said their team had to look for voxels or the three-dimensional volumetric pixels that responded to both visible and invisible objects to find the visibility-invariant category.

Their hard work though had led to important findings. Their study found that face perception is much more linked to neural information integration than to category tuning. Fahrenfort said conscious face perception requires face-selective cells to interact with earlier areas in the network that initially respond only to simple bottom-up features. Such interaction is what really causes a stimulus to become conscious.

For future studies, the team would like to look at the measures that more accurately capture processes involved in the actual information integration, not just its ‘markers’.

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Source of this article:

Neuronal integration in visual cortex elevates face category tuning to conscious face perception