Critically Discuss The Notion That The Amygdala Is The Brain Structure Responsible For All Emotions (Essay Sample)

Title: A critical discussion of the notion that the amygdala is the brain structure responsible for all emotions
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A critical discussion of the notion that the amygdala is the brain structure responsible for all emotions
According to the Webster New World Dictionary, the term ‘emotion’ refers to a state of mind occurring when feelings have been aroused or stimulated. It differs from other frames of mind such as cognition and the awareness of bodily sensations (Elder, 1996). Emotions have long been recognized as a critical engine that propels human behaviour since it affects the ability of human beings to coexist with each other and survive in the world (Blanchard et.al, 2001). Indeed, emotions are responsible for how human beings relate to one another, where positive emotions lead to positive human relationships and vice versa.
Until recently, scientists and psychologists were of the opinion that feelings can not be empirically and scientifically understood with most believing that emotions are to because they are too intangible, making it impractical to determine the neural substrates of emotions (Robinson, 2002). This has however been proven to be false and studies examining the neurobiology of emotions have been conducted, including human imaging, human amygdala damage and animal lesion studies (Robinson, 2002). The major area of contention now is in determining what part of the brain is responsible for emotions. It has been posited by many neuroscientists that it is the amygdala (a two-sided structure in the brain from the medial temporal lobe) (Bonnet et.al, 2015). This brain structure has long been the centre of attention from neuroscientists who consider its role to be vast, stretching from the molecular and cellular to the clinical level, including a significant role in all human emotions (Adolphs, 2010). Other psychologists are of a differing opinion, however, with a considerable number holding the belief that the amygdala only plays a role in a few emotions, particularly negative ones such as fear and anger. The following discussion shall therefore seek to determine the truth, critically analysing various empirical studies that have addressed the notion that the amygdala is the brain structure responsible for all emotions.
Discussion
For several decades, researchers have considered the amygdala to be integral to emotion, especially with respect to handling information that is aversive (Bonnet et.al, 2015). To determine whether the amygdala is indeed the brain structure responsible for all emotions, studies that have put forward arguments for and against the role of the amygdala in emotions need to be analysed. Several human neuroscience studies including those undertaken by Lindquist et al (2016), LeDoux (1996) and Sabatinelli et al (2011) have found that emotionally arousing stimuli trigger the amygdala and this indicates that the major duty of the amygdala could be in sensing all emotionally arousing signals and thereafter triggering the motivational circuitry of a human or animal.
A recent study carried out by Bonnet et al. (2015) offers further proof of this emotion “arousal” perspective. In the study, BOLD (blood-oxygenation-level-dependent) activity was measured as participants watched enjoyable visuals varying in emotional arousals. The study discovered that there was a higher activation of the amygdala and hypothalamus, and greater autonomic reactivity for the images that participants viewed to be high in arousal. The opposite was true for images that were rated to be low in arousal. These results align with data from earlier empirical research done by Lang et al (1993) and Bradley et al (2001). The findings are also in tandem with research findings from animal data conducted by Davis and Whalen (2001) as well as Lang and Davis (2006) that revealed that projections from the amygdala to the lateral hypothalamus trigger strong sympathetic activation.
In addition, Adolphs (2010) states that the amygdala plays an unmistakeably key role in processing all emotionally and socially pertinent data. It accomplishes this by processing a psychological stimulus dimension that is linked to relevance. Mechanisms have been pinpointed to associate it with processing unpredictability, and understandings obtained from reward learning have located it within a system of structures such as the prefrontal cortex in processing the present value of a trigger. These aspects help to reveal the amygdala's role in identifying emotion from faces.
Furthermore, functional neuroimaging and lesion-based neuropsychological experiments have been conducted, showing the role that the amygdala plays amongst human beings in determining fear and anger in facial expressions. In their study, Adolphs et.al (2016) analysed the recognition of emotional dimensions, arousal and valence, in participants who had experienced total bilateral damage on their amygdala. The study found that recognition of emotional arousal with respect to facial expressions and negative words/phrases/sentences particularly those related to fear and anger was impaired. Recognition of emotional valence was however not impaired. These findings indicate that the amygdala plays a significant role in helping to recognise negative emotions, a findings that is in line with the role that the amygdala plays in processing stimuli associated with risk and hazard.
According to further research done by McGaugh (2013), empirical evidence indicates that emotional arousal improves the ability to store memories thereby allowing us to have enduring memories of particularly significant emotional experiences. The studies reveal that neurobiological systems that facilitate emotional stimulation and memory have a very close connection. Emotional arousal releases corticosterone and adrenal stress hormones epinephrine, which in the process solidifies long-term memory. The amygdala is highly instrumental in mediating the stress hormone stimuli. The amygdala releases norepinephrine and noradrenergic receptors are activated all of which is necessary in enhancing stress hormone-induced memory. The findings of both human and animal studies give convincing proof that the activation of the amygdala by stressful triggers and its interplay with other brain structures that are pertinent in processing memory are crucial in making sure that experiences that are emotionally noteworthy are kept in memory in the long term (McGaugh, 2013).
Functional neuroimaging studies have further given considerable backing to the notion that the amygdala plays a major role in overall emotional processing. Nevertheless, Sergerie et.al (2008) rightfully points out that several contentions exist with respect to whether different factors like sex, the type of stimuli and valence influence the scale and lateralization of how the amygdala responds. To determine this, Sergerie and his colleagues carried out a meta-analysis of functional neuroimaging studies of visual emotional perception that reported amygdala activation. This study was critical in nature since they took into consideration the size of the effect (scale) and the reliability linked to all the activations, an approach that was markedly different from neuroimaging meta-analyses studies that were done in the past. Their results revealed that the amygdala’s responses were to both positive and negative triggers, with an inclination towards faces that exhibited emotions. The study did not find any proof that factors such as sex or valence have an influence on the scale and lateralization of how the amygdala responds to stimuli.
That said, despite all these studies that place the responsibility of emotions on the amygdala, there are several researchers who are of a divergent opinion. According to studies done by Vuilleumier et al. (2004) and Adolphs et al (2005), for instance, a lot more evidence exists in relation to the central role the amygdala plays in the emotional enhancement of mnemonic and perceptual processes rather than in their overall responsibility and role with respect to all emotions as a whole. As per the findings of Bradley et al (2003), neuroimaging studies have shown that emotionally arousing images strongly stimulate the early primary and secondary visual cortex, not the amygdala.
Another study that puts into question whether the amygdala is actually responsible for emotions was carried out by Liu et.al (2015). The study found that whereas the amygdala is widely deemed to be the substrate for the processing of emotions, their findings show that the evidence for the involvement of the left and right amygdala in the early recognition of various facial expressions is vague. The findings additionally revealed that the right amygdala is linked to autonomic stimuli created by facial emotions and the left amygdala might be involved in assessing expressive faces but only during early perceptual emotion processing. The results of effective connectivity are evidence that the cortical and subcortical pathways linked to the right amygdala are only engaged during negative emotional processing. The amygdala therefore appears to only play a role in processing negative emotions, not all emotions that human being experience.
Furthermore, Dr. Damasio, who is Head of Neurology at the University of Iowa College of Medicine and is widely considered a leader in the area of neurobiology of emotions, does not consider the amygdala to responsible for emotions overall. Based on his studies, he found that the amygdala is an induction site, playing a role in the origination of the force that leads to an emotion like fear. It does not, however, have a role in initiating a majority of other human emotions.
According to Dr. Damasio, when humans have certain injuries on the amygdala and no impairments to the cortex or hippocampus, there is only a change...