Emotions and Learning

Show how emotion influence learning.

A primer on Emotions and Learning by Ulrike Rimmele
"Emotions have a profound impact on what we learn and keep in mind."
 
So far, knowledge on the neurobiological underpinnings of emotional influence on learning and memory is most elaborate considering fear and stress as well as two special dimensions of emotional information: arousal (how exciting or calming) and valence (how positive or negative). Therefore this primer will focus on the influence of these emotional states on learning and memory.

Fear      
      The amygdala is a critical part in fear processing circuits. It mediates the fear response and the association of a stimulus with fear. Thereby, when a tone signals danger, the information reaches the amygdala via two pathways (Figure 1). One pathway is rapidly processed and thus only approximate information of an emotional stimulus leads directly from the thalamus (footnote 2) to the amygdala. The other, indirect pathway, mediates information of an emotional stimulus from the thalamus to the amygdala via the cortex (footnote 3). Thus, the information of the indirect pathway is more highly processed and reaches the amygdala after a brief lag of time. To illustrate the meaning of these pathways, imagine a hiker walking through the woods. All of a sudden, he stops and freezes. Only a few meters in front of him lies a snake. His heart races and he is scared. Then he realizes that he actually mistook a root for a snake. He calms down and continues walking. This reaction can be divided into two phases. First, the hiker sees something that looks like a snake, stops walking and his body gets prepared for a dangerous situation: his heart rate increases, etc. Only then, the hiker realizes that the snake is actually not a snake, but a root. He calms down and continues walking.

It is important to note that the conscious recognition of the "snake" happens after the startle response. What brain processes causes the hiker to react like this? An emotional stimulus, something that looks like a snake, is first processed in the brain by the thalamus. The thalamus passes on a fast, but crude representation of the stimulus to the amygdala. This fast but crude transmission allows the brain to start to respond to a potentially dangerous object, which could be a snake. Therefore, the hiker's body prepares for a dangerous situation, before he even knows what the stimulus is. Meanwhile, the thalamus also sends information to the cortex for more thorough examination. The cortex then creates a more detailed and accurate representation of the stimulus. The hiker realizes that he mistook a root for a snake. This outcome is fed to the amygdala as well and is transmitted to the body. The hiker then calms down. The advantage of the thalamus-cortex-amygdala pathway is that the stimulus representation is more accurate, it does, however, take longer. In situations of danger, the fast thalamus-amygdala pathway is very useful. The time saved by the direct pathway could be decisive between survival and death.

Fig 1: Direct and indirect pathways to the amygdala.
Information about an external stimulus reaches the amygdala by two ways: by a direct pathway from the thalamus and by an indirect pathway from the thalamus via the cortex to the amygdala. The direct pathway is shorter and faster, but therefore provides only a crude representation of the stimulus. Thus, this pathway allows responding to a stimulus before fully knowing what the stimulus is. However, at the same time, the stimulus is more thoroughly processed by the cortex in the indirect pathway. Then the cortex can prevent inappropriate responses.
 
Fear and learning in humans
     In humans, the amygdala has also been shown to be crucially involved in the processing and encoding of fearful stimuli into memory. This shows that memories produced by fearful situations have both an affective and a cognitive component. Thereby the unconscious affective component involves the amygdala, while the conscious cognitive component depends on the hippocampus (Figure 2).

Fig 2: Memory of an emotional situation is mediated by multiple memory systems: The conscious explicit memory is mediated by the hippocampus and its associated cortical areas. The unconscious implicit memory of fear is by the amygdala and its associated areas.

Stress and learning Stress is a condition that is provoked by heightened demands on the cognitive and motor system and is experienced accordingly emotionally. Imagine for example that you are meeting a lion in the street. This is a dangerous stressful situation! Your brain recognizes quickly that you are in danger and prepares your cognitive and motor system for survival. A set of various reactions to the stressor (lion) makes up the stress response. Your cognitive capacities increase, e.g. vigilance and attention, and your body gets prepared for fight or flight. Your heart rate and blood pressure rise while digestion, growth and reproduction are slowed down, as these functions are not necessary in an acute stress situation and can be delayed without damage to the organism. This stress response is mediated by stress hormones: Within milliseconds, epinephrine and norepinephrine are secreted. Seconds later, the secretion of cortisol follows. Research has shown that these stress hormones act on the brain and thereby modulate cognition, learning and memory.

The effects of nor-/epinephrine on learning and memory will be described under the paragraph "emotional arousal" because they are also secreted under emotional arousal. Let us therefore examine the effects of the hormone cortisol. What would you do to find out about the effects of cortisol on learning and memory? Researchers induced heightened cortisol levels with laboratory stress tests (e.g. a public speaking task or a mental arithmetic task, real stress situations (examination stress)) or the administration of pills containing cortisol or similar substances. Then they had subjects memorize word lists, pictures or film clips. From the findings of these studies, it can be hypothesized- in accordance with findings from animal studies- that low and medium cortisol levels improve learning and enhance memory, whereas high levels of cortisol have a deleterious effect on learning and memory.

Arousal and pleasure in memory  
      During the last decade, researchers have started to investigate certain facets of emotional memories. Margaret Bradley and her colleagues presented slides that were either neutral (e.g. umbrella), pleasant (e.g. a beach at sunset) or unpleasant (e.g. an attacking snake). The subjects remembered the emotional slides better than the neutral ones. Interestingly, after a year, the pictures, that were arousing, were remembered a lot better than the ones that were low in arousal. Bradley concluded that pleasantness as well as arousal are important at the initial stage of memory formation, while long-term memory is mainly affected by arousal. This might explain our flashbulb phenomenon of the 11th of September. Possibly, emotional arousal was triggered by the announcement of the attack, leading to a deeper elaboration and thus to a potentiation of our memory of this event.

But what processes happen in the brain during emotional memory formation?

And what role does arousal and what role does valence, i.e. pleasantness play therein?

Norepinephrine plays a crucial role in mediating the memory-enhancing effect of emotional arousal under normal circumstances. In a further study, it was found that another stress hormone, cortisol, impaired memory for the emotionally arousing information of the story, while it enhanced memory for neutral material . Taken together, the findings of these studies indicate that a specific hormonal and brain system, which is activated by emotional arousal, regulates long-term memory storage. Within this emotional memory brain system, the stress hormones norepinephrine and cortisol, as well as the amygdala appear to be critical for the modulation of memory enhancement for emotionally arousing stimuli.

Footnotes
1- The word amygdala means almond-shaped and stands for a collection of neurons with the size and shape of an almond. Every human has two amygdalae located one at each side of the brain. They are part of a set of structures collectively known as the limbic system that lies within the center of the brain. This system is viewed as the seat of emotion and is therefore also referred to as the “emotional brain”.
2- The thalamus is a sensory relay station. Information of an emotional stimulus is first sent to the thalamus. The thalamus then passes this information on in two different ways: directly to the amygdala or to the amygdala via the cortex
3- The cortex is the furrowed gray matter covering the cerebral hemispheres. It is the part of the brain in which the operations for our cognitive abilities occur.
4- The hippocampus plays a major role in forming long-term memories for facts and events, the kind of memory- also referred to as declarative memory
5- They administered propanolol, a drug that acts on ß-adrenergic receptors and thereby dampens the body reactions to arousal
6- The prefrontal cortex is located in the frontal part of the brain and plays an important role in working memory