Conscious and Non-conscious Representations of Emotional Faces in Asperger's Syndrome

Summary

An EEG experimental protocol is designed to clarify the interplay between conscious and non-conscious representations of emotional faces in patients with Asperger's syndrome. The technique suggests that patients with Asperger's syndrome have deficits in non-conscious representation of emotional faces, but have comparable performance in conscious representation with healthy controls.

Abstract

Several neuroimaging studies have suggested that the low spatial frequency content in an emotional face mainly activates the amygdala, pulvinar, and superior colliculus especially with fearful faces^1-3. These regions constitute the limbic structure in non-conscious perception of emotions and modulate cortical activity either directly or indirectly². In contrast, the conscious representation of emotions is more pronounced in the anterior cingulate, prefrontal cortex, and somatosensory cortex for directing voluntary attention to details in faces^3,4. Asperger's syndrome (AS)^5,6 represents an atypical mental disturbance that affects sensory, affective and communicative abilities, without interfering with normal linguistic skills and intellectual ability. Several studies have found that functional deficits in the neural circuitry important for facial emotion recognition can partly explain social communication failure in patients with AS^7-9. In order to clarify the interplay between conscious and non-conscious representations of emotional faces in AS, an EEG experimental protocol is designed with two tasks involving emotionality evaluation of either photograph or line-drawing faces. A pilot study is introduced for selecting face stimuli that minimize the differences in reaction times and scores assigned to facial emotions between the pretested patients with AS and IQ/gender-matched healthy controls. Information from the pretested patients was used to develop the scoring system used for the emotionality evaluation. Research into facial emotions and visual stimuli with different spatial frequency contents has reached discrepant findings depending on the demographic characteristics of participants and task demands². The experimental protocol is intended to clarify deficits in patients with AS in processing emotional faces when compared with healthy controls by controlling for factors unrelated to recognition of facial emotions, such as task difficulty, IQ and gender.

Introduction

Facial emotion recognition is one of the most important brain processes engaged in social communications. A variety of mental disorders are related to problems with explicit detection of facial emotions^4-6. A photograph of a face contains a spectrum of spatial information that can be filtered for either the high spatial frequency (HSF) or low spatial frequency (LSF) content. HSF is related to highly detailed parts of an image, such as the edges of a face, while LSF is related to coarser or less well-defined parts such as a holistic face with LSF contents⁷. Any face recognition task simultaneously induces conscious and non-conscious processes^....

Protocol

Ethics Statement: Procedures involving human participants have been approved by the human participant research ethics committee/Institutional Review Board at the Academia Sinica, Taiwan.

1. Stimuli and Experimental Program Preparation

1. Prepare a pool of more than 60 emotional face photographs²⁹ categorized into three facial expressions (angry, happy, and neutral). Use graphics software to mask out hair and ear parts in the photographs with black background as shown in Figure 1A so that participants can concentrate on the facial features in the photographs.
   1. Open a photograph in the graphics software. Use the sel....

Results

The average verbal and performance IQ scores are listed in Table 1 for the control and AS groups along with the average reaction times and average scores assigned to emotionality of faces of the two groups. In the table, none of the group differences achieves statistical significance except for the neutral faces in the line-drawing task, where the AS group has an average score near zero (p <0.001)¹³. Interestingly, the AS group still has slightly lo.......

Discussion

The literature features studies on recognition of facial emotions in patients with autism by analysis of EEG reactions⁴⁴, and on recognition of high- and low-spatial frequency contents using visual stimuli⁴³. To the best of our knowledge, however, there is a lack of existing work on the brain oscillatory activity that combines emotion recognition with distinct spatial frequency contents. Our protocol is a first step towards estimating the influence of emotionality (positive, neutral and negative fac.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Synamps 2/RT 128-channel EEG/EP/ERP	Neuroscan
Quik-CapEEG 128 electrodes	Neuroscan
Gel	Quik-Gel
FASTRAK 3D digitizer	Polhemus