Neural correlates underlying subjective experience in perceiving emotion: an ERP study

다국어 초록 (Multilingual Abstract)

A noticeable number of recent researches suggest significant influence of top-down modulation in emotional perception. Here, we attempted to investigate the neural substrates related to the bottom-up and top-down modulation when making an emotional perceptual choice. We focused on the relation between the brain activity and the reported emotional percept.
Ambiguous stimuli were presented to assess the influence of the top-down process in emotional perception. These ambiguous stimuli were consisted of fearful faces and neutral faces embedded in identical noise patches and were altered to form two different contrast levels (high and low). The contrast level of the low-contrast condition was adjusted to the extent where the subjects were aware of the faces (an A´ value significantly greater than 0.5 measured by SDT methods) yet able to make different responses according to how they perceived the stimuli. An additional condition consisted of noise-alone displays without any facial stimuli embedded were also included.
The emotional facial stimuli and the noise alone stimuli were presented randomly on a trial-by-trial basis to preclude any possible emotional expectation effect when perceiving the stimuli. EEG recording was conducted while the subjects (N=22) performed a forced, two choice emotion-discrimination task. ERP analyses were made for the four following response categories: hit, miss, false alarm and correct rejection (‘fearful faces’ being the signal and ‘neutral faces’ being the noise).
We observed an augmented early posterior negativity (EPN; 260-280ms, temporo-occipital sites) amplitude and an enlarged late positive potential (LPP; 350-550ms, centro-parietal sites) when subjects reported to see a fearful face, even when fearful face was not physically presented (hit vs. correct rejection trials and false alarm vs. miss trials).
The results of the ERP data showed a characteristic modulation that reflects emotional processing that occurs according to whichever type of emotion each individual subjectively perceived. The results above suggest that neural responses could be evoked corresponding to the subjective state or a top-down modulation without any relevant bottom-up stimuli.

국문 초록 (Abstract)

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