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Emotions and the brain

Help UI researcher receives grant to study connectivity in the brain Fear conditioning Some outcomes from our “Imaging human emotion” research
Cultural Specificity in Amygdala Response to Fear Faces
Original modules
History Module: The Quest for the “Emotional Brain” The Quest for the “Emotional Brain”
Tool Module: Brain Imaging   Brain Imaging

Through various animal species have evolved many different behavioural responses to danger, the central role of the amygdala in the fear response seems to have been very well preserved in all of them. The earliest experiments, in which the amygdala was removed, demonstrated that its absence interfered tremendously with an animal’s ability to assess danger. Later experiments, in which electrical stimuli were applied to the amygdala, repeatedly generated the same well-known defence reactions (bodily changes, inhibition, flight, defensive attack) in several different species of mammals.

The amygdala is a structure located deep in the anterior inferior temporal lobe of the brain. The amygdala receives projections mostly from the sensory regions of the thalamus and the cortex, but also from several other structures such as the hippocampus and the prefrontal cortex.

As with the hippocampus, most of the neural pathways that enter the amygdala are paired with other pathways that exit it. One of these output pathways is the ventral amygdalofugal pathway, which plays an important role in associative learning–of a conditioned fear, for example. The gratifying or aversive nature of a stimulus is associated by connections of this pathway to the nucleus accumbens, which plays a recognized role in the brain’s pleasure circuits. The other main destinations of this pathway are the ventral striatum, the septum, the hypothalamus, the nuclei of the brainstem, and certain parts of the cortex (orbitofrontal, piriform, cingulate, etc.).


Another important pathway emerging from the amygdala is the stria terminalis, which is to the amygdala as the fornix is to the hippocampus. Like the fornix, the stria terminalis projects only to sub-cortical structures such as the hypothalamus and the septum. The hypothalamus and the septum also receive projections from the amygdala by another route–the ventral amygdalofugal pathway–as well as from the hippocampus. Moreover, the hippocampus and the amygdala are located beside and have many connections with each other.  

The basal ganglia, a group of sub-cortical nuclei, are another area of the brain that seems to be closely involved in voluntary emotional activity. The basal ganglia are known to be involved in controlling movement, and their interaction with the amygdala supports this active, voluntary component of the behavioural expression of emotion.

Meanwhile, the automatic bodily responses involved in emotions such as fear are controlled mainly by the outputs of the amygdala to the nuclei of the sympathetic nervous system in the brainstem and to the hypothalamus, which itself controls the hormonal secretions of the pituitary gland.

The outputs of the amygdala provide a good idea of what is necessary for the experience of an emotion such as fear. The connections from the amygdala to the cortex can influence attention to and perception and memory of dangerous situations. The amygdala can also influence the cortex indirectly, through its connections to the attention system in the brainstem. Other parts of the brainstem trigger the cascade of physiological reactions associated with fear that send feedback to the brain. When this feedback is combined in working memory with the other “ingredients” just described, it produces the feeling of experiencing an emotion.


An emotional meeting of minds
Emotion research starts to yield results! EMOTION, MEMORY, AND THE BRAIN: What the Lab Does and Why We Do It
Original modules
History Module: The Quest for the “Emotional Brain” The Quest for the “Emotional Brain”
Experiment Module: Identifying the Brain Structures Involved in Conditioned Fear   Identifying the Brain Structures Involved in Conditioned Fear

When you have a traumatic experience, the implicit memory systems of your amygdala and the explicit memory systems of your hippocampus record different aspects of the event. Later on, your hippocampus will enable you to remember such things as where the event happened, when it happened, and whom you were with at the time. Meanwhile, as your amygdala is activated, your muscles will tighten, your blood pressure will rise, your stomach will get tied up in knots, and so on.

Because both of these systems are activated by the same memory indexes, we do not realize that they are actually specialized. But certain experiments and pathological case studies have highlighted their independence.

For example, one woman had suffered such severe damage to her hippocampi that she could not recognize her doctor, even though she saw him every day. Every day, they shook hands and introduced themselves as if for the first time. One day, to test a hunch, the doctor placed a thumbtack in the palm of his hand before extending it to his patient. When she saw it, she pulled her hand back suddenly. The next day, when she and the doctor were about to shake hands again, she pulled her hand back at the last minute. When the doctor asked her why she had done so, the only explanation she could give was that she had experienced a sudden sense of fear.


When the brain receives a sensory stimulus indicating a danger, it is routed first to the thalamus. From there, the information is sent out over two parallel pathways: the thalamo-amygdala pathway (the “short route”) and the thalamo-cortico-amygdala pathway (the “long route”). The short route conveys a fast, rough impression of the situation, because it is a sub-cortical pathway in which no cognition is involved. This pathway activates the amygdala which, through its central nucleus, generates emotional responses before any perceptual integration has even occurred and before the mind can form a complete representation of the stimulus.

Subsequently, the information that has travelled via the long route and been processed in the cortex reaches the amygdala and tells it whether or not the stimulus represents a real threat. To provide this assessment, various levels of cortical processing are required.


First, the various modalities of the perceived object are processed by the primary sensory cortex. Then the unimodal associative cortex provides the amygdala with a representation of the object. At an even higher level of analysis, the polymodal associative cortex conceptualizes the object and also informs the amygdala about it. This elaborate representation of the object is then compared with the contents of explicit memory by means of the hippocampus, which also communicates closely with the amygdala.

The hippocampus is the structure that supports the explicit memory required to learn about the dangerousness of an object or situation in the first place. The hippocampus is also especially sensitive to the encoding of the context associated with an aversive experience. It is because of the hippocampus that not only can a stimulus become a source of conditioned fear, but so can all the objects surrounding it and the situation or location in which it occurs.

The imminent presence of a danger then performs the task of activating the amygdala, whose discharge patterns in turn activate the efferent structures responsible for physical manifestations of fear, such as increased heart rate and blood pressure, sweaty hands, dry mouth, and tense muscles.

The parallel operation of our explicit (hippocampal) and implicit (amygdalic) memory systems explains why we do not remember traumas experienced very early in our lives. At that age, the hippocampus is still immature, while the amygdala is already able to record unconscious memories. Early childhood traumas can disturb the mental and behavioural functions of adults by mechanisms that they cannot access consciously.

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