There has been a great deal of interest within the medical and scientific community in studying the response of various regions of the brain to emotional stimuli. Much research has focused on the role of the amygdala in response to emotional stimuli, and the effects of such stimuli on learning and memory retention. The amygdala "is a structure in the medial temporal lobe that is known to participate in emotional and motivational functions in animals" (CGN, 2004) however its role in human emotional response has not yet been fully uncovered. It has been directly implicated however, in emotional stimulus related examinations. The amygdale is not the only brain region activated by emotional stimuli. Recent research has suggested that many areas of the brain are activated and affected by emotional stimuli, not just the amygdala. In fact, depending on the type of emotional stimulus presented, most of the brain regions may be activated.
This paper will examine the question of which areas of the brain are engaged by emotional stimuli. The preliminary hypothesis to be supported is that every region of the brain is activated by emotional stimuli; and that secondarily, each region of the brain is activated in different manners by different stimuli. Some stimuli will have a greater affect on certain areas of the brain than others. For example, emotional responses to recognizable stimuli may elicit a stronger response than responses to foreign stimuli. The paper proposes to prove that notion that every region of the brain does not act similarly in response to various emotional stimuli, but most regions will react in some manner. The amygdala for example, will react more aggressively to certain forms of emotional stimuli than others.
The literature examined below supports the notion that various regions of the brain are affected and activated in different manners with regard to the same emotional stimuli. Each study takes a different approach to examining various forms of emotional and sensory stimuli, but most conclude that many regions of the brain are activated regardless, and some support the notion that emotional stimuli drain the brain of its ability to process other types of stimuli simultaneously. Further research needs to be conducted however, because great mystery still exists as to the extent of impact emotional stimuli have on the brain.
The first research study examined, "Attention Control of the Processing of Neural and Emotional Stimuli" very soundly supports the notion that many regions of the brain are activated during emotional stimuli, and that to process such stimuli the brain must drain resources from other regions. Specifically, this study suggests that at the neural level, there is "competition among multiple stimuli" evidenced by "mutual suppression of their visually evoked responses" (Pessoa et. al, 2002). Thus, when one region of the brain is activated by a particular emotional stimuli, the brain will subsequently drain resources it might use to activate other regions of the brain to process other types of incoming stimulation. Attention is often affected by this hierarchy of processing within the brain.
This study also verified that "top-down biasing of visual signals comes from the brain primarily in the areas of the frontal and parietal cortex" (Pessoa, et. al, 2002). Meaning, these regions of the brain are biased regarding their response and processing of emotional stimuli. The evidence uncovered by the researchers in this case suggests that if emotional stimuli enter the brain via visual stimulus the frontal and parietal cortex is activated.
This research examination also supports the notion that emotional stimuli are capable of automatically activating these brain regions, and that all brain regions respond in a different manner to emotional cues, including the amygdala, which according to this study, only responds when "sufficient attentional resources were available to process faces" (Pessoa, et. al 2002). The amygdala will not necessarily therefore, respond to all types of emotional stimuli, and may in fact be very selective in nature.
Interestingly, this last point leads to the conclusion that attentional resources within the brain must be leftover after processing emotional stimulus in order to complete an entire cognitive process. Some people might have a deficit in attentional processing ability after having processed emotional stimuli, and further research is being conducted in this area to examine the potential link between emotional processing and attention deficit disorders (Pessoa, et. al, 2002).
K.S. LaBar in an early study entitled "Arousal-mediated memory consolidation: Role of the medial temporal lobe in humans" documents the effects of emotional arousal on memory and examines the mechanism through which arousal and emotional stimuli affect the various regions of the brain. Memory and the activation of various regions during emotional stimulation are integrated. The regions of the brain that process emotional stimuli and subsequently store this information are varied in nature.
Particularly, the researchers sought to examine whether the amygdala and hippocampus work together in an integrated fashion in human brains to consolidate memories following emotional stimulus. Previous studies seem to have shown that an integrated function between the amygdale and hippocampus does exist in animal subjects (LaBar, et. al, 1998). Subjects in the study were asked to rate emotionally arousing words on a scale, and their skin conductance responses were subsequently measured. Recall for words was examined.
The study examined individuals' with brain damage to the amygdala and hippocampus, and suggested that the medial temporal lobe integrated emotional stimuli and was thus, "essential for consolidating declarative memories for arousing stimuli in the human brain." (LaBar, et. al, 1998). Thus, it seems the brain will adapt when injured and still have the ability to process emotional stimuli using other regions for processing and interpretation.
This study is important to the hypothesis proposed at the start of this paper because it supports the notion that more than just the amygdale and hippocampus are activated by emotional stimuli. In the patients examined in this study, "the medial temporal lobe became essential for processing emotional stimuli in patients who had amygdalo-hippocampul damage" or defects within the brain (LaBar, et. al, 1998).
In a study entitled "Willed Action: A Functional Study of the human prefrontal cortex," Hyder and colleagues hypothesized that when certain cognitive tasks were performed, a "large area of the dorsolateral prefrontal cortex" was activated, leading the researchers to conclude that brain activity in this area of the brain is due to "willed action" and is "independent of the stimulus modality" (Hyder et. al, 1997).
This study is important because it supports the concept that it does not matter what "modality" of emotional stimulus is presented to the human brain, whether verbal or sensori-motor or emotional, many regions of the brain are activated significantly. The study also concluded that brain activity "for verbal fluency tasks was lateralized to the left hemisphere, whereas the activity for sensori-motor task was bilateral" (Hyder et. al 1997). Willed acts or sensori-motor acts can be differentiated from some types of emotional stimuli, but were "generally shown to increase the blood flow significantly in the dorsolateral prefrontal cortex" (Hyder, et. al 1997). The type of stimulus presented for purposes of this experiments included subjects moving two fingers in response to a stimulus.
H. Yamasaki and colleagues performed a study entitled "Dissociable prefrontal brain systems for attention and emotion," which examines the prefrontal cortex or PFC, which is a "heterogeneous brain region." (Yamasaki, et. al, 2002). The study seeks to examine whether or not the PFC is divided into "domain-specific regions" which would validate whether or not this area of the brain will activate and respond to varying emotional stimuli or other types of stimuli. Both attentional and emotional stimuli were examined, and the results from the study show that attentional and emotional functions are carried out by different regions of the brain. They are segregated into "parallel dorsal and ventral streams that extend into the prefrontal cortex and integrated in the anterior cingulated." (Yamasaki, et. al, 2002).
The study is important because it my help uncover whether emotional distractibility related to attentional tasks are related. The study seems to suggest that different regions of the brain are affected by attentional vs. emotional stimuli. However, it also acknowledges that a great deal of behavioral studies have been conducted that have shown that emotional stimuli can affect the allocation of resources in the brain to attentional functions. This means in an indirect manner, the brain uses resources that may have been allocated to attentional functions to process various forms of emotional stimuli, and that these tasks are carried out in many regions of the brain including the rostral anterior cingulate.
The most significant point the study makes is that the emotional stimulus will activate different regions of the brain at different levels depending upon how much attention was devoted to the task at hand.
The study "Neural Correlates of Person Recognition" identified the regions of the brain that are activated by emotional stimuli in an abstract manner. In this study participants were examined to assess their ability to…