Amygdala and Emotional Facial Expressions

Amygdala, a small subcortical structure lying deep within the temporal region of the brain is a part of the limbic system which responsible for processing the emotion. Emotions are part of our lives and are categorised into Negative and positive emotions. Positive are emotions which makes an individual feel good like joy and happiness While Negative emotions such as sadness, loneliness anger, fear, or rejection are painful at times. Amygdala receives input from the other units of the brain such as the medial geniculate nucleus which is located in the thalamus. additionally, it receives stimuli from the coagulate and orbitofrontal cortices. Evidences show that the amygdala is responsible for interpreting the meaning of the construction of facing expression based on the social and emotional meaning. Other parts of the brain which are concerned with emotions include the Hypothalamus which controls emotional responses, the hippocampus which helps preserve and retrieve memories as well as the limbic cortex which contains the cingulate gyrus as well as the parahippocampal gyrus which together influence mood, motivation, and judgement. The seminal reports of Brown, Shafer, Kluver and Bucy mentioned by Kluver & Bucy (1939) showed that primates’ amygdala is responsible for regulation of the social and emotional behaviour. In the mentioned study the temporal lobes of a number of rhesus monkeys were bilaterally removed and visual agnosia, an increased tendency to explore items by mouth, hypermetamorphosis, dampening of emotional expression, altered sexual behavior and differences in diet were observed among those primates. A majority of human neuroscience studies, however, found that the amygdala is activated by emotionally arousing stimuli, regardless of whether they are pleasant i.e. joy, truest etc. or unpleasant like fear, anger and sadness (Sabatinelli et al., 2011; Costafreda et al., 2008; Lindquist et al., 2016), These studies suggest that the amygdala's predominant role may be the detection of emotionally arousing cues and subsequent activation of the organisms' motivational circuitry.

The aim of the study conducted by Adolphs & Tranel (2003) was to evaluate if the damage in the amygdala influences the recognition and/or interpretation of the meaning of the facial expression. The performance of two groups; 23 persons with unilateral amygdala damage in the first group and 22 brain damaged persons without amygdala damage in the second groups was compared. Both groups were shown visual stimuli; two blocks of complex social scenes using a computer, and the performances were converted to accuracy score based on the data collected from neurologically normal population. The study found that bilateral amygdala damage disproportionately impairs recognition of anger from complex visual stimuli when the subjects are presented with facial expression for example, the participants frequently mistook expressions of anger for smiles. The researchers concluded that the amygdala is relatively specialized for processing certain negative facial expressions, and that hence damage to the amygdala results in a disproportionate impairment in recognizing scenes containing such facial expressions and the amygdala might play a broader role in processing faces, and that certain negative facial expressions are more difficult to process and hence stand out following amygdala damage. the first limitation of the study is the use of relatively smaller number of stimuli. Secondly the stimuli were biased to trigger more negative expression than positive expression.

In conclusion, though other parts of the brain such as the Hypothalamus which controls emotional responses, the hippocampus and the limbic cortex together influence emotions, it is Evident that amygdala is responsible for processing the emotion, and interpreting the meaning of the construction of facing expression based on the social and emotional meaning.