9th August 2021
Neuron mechanisms behind emotions
Neuron mechanisms behind emotions
Over time, we experience many different feelings. Sometimes we put verbal labels on these different feelings. At some point we might say “I feel angry.” At other times we might label our feeling disgusted, afraid, happy, sad, surprised, prideful, ashamed, empathic, hungry, thirsty, or lustful. These twelve feelings are sometimes called primary emotions, but there are perhaps hundreds of different words for feelings, each corresponding with a different subjective experience, although the differences can sometimes be quite subtle.
Feeling angry tends to bias us in favour of more aggressive behaviours. Each of the other feelings bias our behaviour in some different way. Fear biases us in favour of getting away from situations. Sadness biases us in favour of avoiding many behaviours. Disgust biases us in favour of rejection behaviours. Happiness biases us in favour of repeating recent types of behaviour. Surprise encourages us to try less usual behaviours and so on.
Feeling angry tends to bias us in favour of more aggressive behaviours. Each of the other feelings bias our behaviour in some different way. Fear biases us in favour of getting away from situations. Sadness biases us in favour of avoiding many behaviours. Disgust biases us in favour of rejection behaviours. Happiness biases us in favour of repeating recent types of behaviour. Surprise encourages us to try less usual behaviours and so on.
NEURAL MECHANISMS BEHIND BEHAVIOURS
The starting point for understanding feelings and emotions in terms of anatomy and physiology is to recall that there are two general types of information processes in the brain: condition definition/detection and behavioural recommendation definition/integration. At every point in time, each current condition detection recommends a different range of behaviours, and the behaviours with the largest total recommendation weight are implemented. Pyramidal neurons in the cortex, hippocampus and amygdala define and detect conditions, called receptive fields. Medium spiny neurons (MSNs) in the striatum of the basal ganglia correspond with behaviours, and the weights of synapses from pyramidal neurons on to MSNs define recommendation weights. The basal ganglia integrate the active weights to determine and implement the most strongly recommended behaviour across all currently detected receptive fields.
STRATEGIC, TACTICAL, SPECIFIC AND DETAILED BEHAVIOURS
Behaviour types vary in generality along a spectrum from strategic through tactical and specific to very detailed. To give an example, think about a player in a soccer game. Alternative strategic behaviour selections could be deciding to play attack or defense. Alternative tactical behaviour selections could be deciding to go to different locations on the field. Alternative specific behaviours could be deciding to mark or tackle a particular player. Detailed behaviours are the muscle movements selected.
Selection of a strategic behaviour limits the range of tactical behaviours that are recommended. Selection of a tactical behaviour limits the range of specific behaviours that are recommended and so on. The way the brain implements this is that the selection of a strategic behaviour releases the condition detections that recommended it to drive condition detections that recommend more tactical behaviours and so on. Hence the most strongly recommended tactical behaviours tend to be of the already selected strategic type.
CORTICAL AREAS AND BASAL GANGLIA REGIONS
There are about 150 different cortical areas in each cerebral hemisphere. These areas are sometimes known as Brodmann areas. Receptive fields defined in different cortical areas are most effective for recommending different types of behaviours. Receptive fields defined in areas within the orbital and medial prefrontal brain regions are most effective for recommending more strategic behaviours. Areas within the dorsolateral prefrontal region are most effective for recommending more tactical behaviours. Areas close to the premotor cortex are most effective for recommending specific behaviours, and the motor cortex is most effective for recommending detailed behaviours.
The basal ganglia is a long structure that extends from a ventral region to a dorsal region. The ventral end selects more strategic behaviours, while the dorsal end selects more detailed behaviours. The different regions of the basal ganglia are targetted by the cortical areas most effective for recommending the corresponding types of behaviour.
The acceptance of a strategic behaviour by the basal ganglia is implemented by the thalamus releasing the cortical receptive field detections that recommended that strategic behaviour to cortical areas that recommend more tactical behaviours.
NEURAL MECHANISMS BEHIND EMOTIONS AND FEELINGS
Emotions and feelings can therefore be interpreted as the presence of strong recommendation strengths in favour of relatively strategic behaviours. At the level of neuron activity, emotions and feelings are active populations of pyramidal neurons with recommendation strengths in favour of a general type of behaviour. These recommendation strengths are not directly in favour of any specific behaviours, but bias behaviour in favour of a strategic type. To give an example, feeling angry is the subjective experience of an active population of neurons with strong total recommendation strength in favour of aggressive types of behaviour. Release of the activity of this population to other cortical areas results in recommendation strengths in favour of a range of different tactical types of aggressive behaviours. These tactical alternatives might include verbal or physical assault on some person or object. If physical assault had the strongest recommendation strength, release of the detections recommending it might lead to a range of recommendations in favour of specific alternatives like kicking, punching, or striking with some weapon. If punching had the strongest recommendation weight, release of the detections recommending it would lead to recommendations in favour of different combinations of body movements that could implement a punch in different ways. Acceptance of one of the ways would lead to detailed muscle movements.
The starting point for understanding feelings and emotions in terms of anatomy and physiology is to recall that there are two general types of information processes in the brain: condition definition/detection and behavioural recommendation definition/integration. At every point in time, each current condition detection recommends a different range of behaviours, and the behaviours with the largest total recommendation weight are implemented. Pyramidal neurons in the cortex, hippocampus and amygdala define and detect conditions, called receptive fields. Medium spiny neurons (MSNs) in the striatum of the basal ganglia correspond with behaviours, and the weights of synapses from pyramidal neurons on to MSNs define recommendation weights. The basal ganglia integrate the active weights to determine and implement the most strongly recommended behaviour across all currently detected receptive fields.
STRATEGIC, TACTICAL, SPECIFIC AND DETAILED BEHAVIOURS
Behaviour types vary in generality along a spectrum from strategic through tactical and specific to very detailed. To give an example, think about a player in a soccer game. Alternative strategic behaviour selections could be deciding to play attack or defense. Alternative tactical behaviour selections could be deciding to go to different locations on the field. Alternative specific behaviours could be deciding to mark or tackle a particular player. Detailed behaviours are the muscle movements selected.
Selection of a strategic behaviour limits the range of tactical behaviours that are recommended. Selection of a tactical behaviour limits the range of specific behaviours that are recommended and so on. The way the brain implements this is that the selection of a strategic behaviour releases the condition detections that recommended it to drive condition detections that recommend more tactical behaviours and so on. Hence the most strongly recommended tactical behaviours tend to be of the already selected strategic type.
CORTICAL AREAS AND BASAL GANGLIA REGIONS
There are about 150 different cortical areas in each cerebral hemisphere. These areas are sometimes known as Brodmann areas. Receptive fields defined in different cortical areas are most effective for recommending different types of behaviours. Receptive fields defined in areas within the orbital and medial prefrontal brain regions are most effective for recommending more strategic behaviours. Areas within the dorsolateral prefrontal region are most effective for recommending more tactical behaviours. Areas close to the premotor cortex are most effective for recommending specific behaviours, and the motor cortex is most effective for recommending detailed behaviours.
The basal ganglia is a long structure that extends from a ventral region to a dorsal region. The ventral end selects more strategic behaviours, while the dorsal end selects more detailed behaviours. The different regions of the basal ganglia are targetted by the cortical areas most effective for recommending the corresponding types of behaviour.
The acceptance of a strategic behaviour by the basal ganglia is implemented by the thalamus releasing the cortical receptive field detections that recommended that strategic behaviour to cortical areas that recommend more tactical behaviours.
NEURAL MECHANISMS BEHIND EMOTIONS AND FEELINGS
Emotions and feelings can therefore be interpreted as the presence of strong recommendation strengths in favour of relatively strategic behaviours. At the level of neuron activity, emotions and feelings are active populations of pyramidal neurons with recommendation strengths in favour of a general type of behaviour. These recommendation strengths are not directly in favour of any specific behaviours, but bias behaviour in favour of a strategic type. To give an example, feeling angry is the subjective experience of an active population of neurons with strong total recommendation strength in favour of aggressive types of behaviour. Release of the activity of this population to other cortical areas results in recommendation strengths in favour of a range of different tactical types of aggressive behaviours. These tactical alternatives might include verbal or physical assault on some person or object. If physical assault had the strongest recommendation strength, release of the detections recommending it might lead to a range of recommendations in favour of specific alternatives like kicking, punching, or striking with some weapon. If punching had the strongest recommendation weight, release of the detections recommending it would lead to recommendations in favour of different combinations of body movements that could implement a punch in different ways. Acceptance of one of the ways would lead to detailed muscle movements.
ANATOMICAL PROCESSES BEHIND EMOTIONS
Some receptive fields defined by the amygdala correlate with circumstances in which it is appropriate to place priority on strategic behaviours corresponding with some of the primary emotions. For example, the amygdala gets inputs from the sensory cortices and can therefore define receptive fields that correspond with the presence of threatening objects. The amygdala gets inputs from the frontal cortex and can therefore define receptive fields that correspond with the presence of threatening situations. These receptive fields have recommendation strengths in the basal ganglia in favour of avoidance behaviours in general. If there is sufficient such recommendation strength, the receptive field detections in the amygdala are released to the frontal cortex, where they contribute to generation of a population of receptive field detections with recommendation strengths in favour of different strategic avoidance behaviours. The population of receptive field detections in the amygdala and frontal cortex is subjectively experienced as fear.
The amygdala is involved in many of the primary emotions, but active populations in the frontal cortex alone that have a strong total recommendation strength in favour of some strategic type of behaviour will be experienced as feelings of different types.
WHAT ARE MOODS?
If a recommendation in favour of a specific behaviour of a strategic type is accepted and implemented, this could result in the receptive fields recommending the type no longer being detected, and the feeling may disappear. In other words, an angry action may result in the angry feeling disappearing a bit later. However, in some situations there may be recommendation strength in favour of some strategic type of behaviour but insufficient recommendation strength in favour of any sufficiently appropriate specific behaviour of the type. The absence of any such specific behaviour could mean that the continued activity of the receptive fields recommending the type is a recommended behaviour. In this situation, the feeling may persist for a long period of time.
Even if there is an implemented specific behaviour, the receptive fields recommending the strategic type of behaviour will generally have some small initial recommendation strength in favour of prolonging their own activity. If such prolongation is rewarded, the recommendation strength will increase. In this situation, once such a feeling has developed, it will tend to continue. Such prolonged feelings are called moods.
SOME QUESTIONS AROUND THE EXPERIENCE OF EMOTIONS
There are a number of questions that have been asked around the subject of how we experience emotions and feelings. Examples include:
What is the difference in brain state between feeling different ways, such as feeling angry and feeling fearful?
At the level of neurons, feeling angry corresponds with the activity of a population of pyramidal neurons with a predominant total recommendation weight in favour of strategic aggressive behaviours. The pyramidal neurons are located mainly in layer V of the orbital and medial prefrontal cortex and in the amygdala. The recommendation weights are the synaptic strengths of these pyramidal neurons on to medium spiny neurons (MSNs) mainly in the ventral basal ganglia. Activity of these MSNs results in release of the activity of the pyramidal neurons with the largest such strength to the dorsolateral prefrontal cortex, driving the activity of pyramidal neurons that tend to have recommendation weights in favour of different tactical behaviours of the aggressive type.
Feeling fearful is the subjective description of the activity of a different population of pyramidal neurons in the orbital and medial prefrontal cortex and the amygdala. Other feelings result from the activity of yet other populations of pyramidal neurons.
Note that any one pyramidal neuron in the orbital and medial prefrontal cortex and in the amygdala may have recommendation strengths in favour of multiple different strategic behaviour types, it is the predominant recommendation strength across the population that determines the feeling.
What are the similarities and differences between brain states at different times when I feel angry?
There can be multiple different populations of active pyramidal neurons that all have a predominant total recommendation strength in favour of the same type of strategic behaviour. Some of these populations may be fairly similar (i.e a high proportion of active neurons are the same), others more different. In some cases the differences are large enough that we label the subjective experience differently. For example, the subjective experience of different populations of active neurons in the orbital and medial prefrontal cortex and in the amygdala, each population with predominant total recommendation strengths in favour of aggressive behaviours in general, may be labelled annoyed, irritated, belligerent, furious, and irate. Release of the outputs of these populations to the dorsolateral prefrontal cortex will generate recommendations in favour of different ranges of tactical aggressive behaviours.
What are the similarities and differences in brain state between my feeling angry and someone else feeling angry?
In both cases the population of active pyramidal neurons in the orbital and medial prefrontal cortex and in the amygdala has a predominant recommendation strength in favour of aggressive behaviours in general. However, there are no correspondences between the receptive fields of individual neurons in the two populations. The receptive fields are defined within the same types of sensory inputs but different experiences. All pyramidal neurons are behaviourally ambiguous and do not correspond with individual behaviours or types of behaviours. Behaviours are only determined unambiguously by interpretation of total pyramidal neuron activity by the basal ganglia.
Do animals feel emotions?
Different populations of active pyramidal neurons in the brains of animals can have recommendation strengths in favour of different types of strategic behaviours. These different populations will be experienced by the animals as different feelings.
What is the difference in brain state between a human feeling angry and a dog feeling angry?
The differences lie in the different populations of active pyramidal neurons. As between different human individuals, there are no correspondences between individual neurons in the two populations. Because of the different sensory capabilities and experiences, there will be even larger differences between the receptive fields of pyramidal neurons in the two brains, and in their ranges of recommendation strengths. However, in both cases the populations have a predominant total recommendation strength in favour of aggressive behaviours, although the more specific tactical behaviours will be different and the detailed behaviours even more different.
Why does feeling angry feel as it does and not something different?
Feeling angry is the subjective description of a pattern of neuron activity with a predominant recommendation strength in favour of the aggressive strategic behaviour type, the result of this activity is a higher probability of selection of aggressive tactical and specific behaviours.
The question of why being angry feels as it does and not something different is not a well formulated scientific question. The statement “I feel angry” and the statement “A population of pyramidal neurons is active that has a predominant recommendation strength in favour of aggressive strategic behaviour both describe the same situation, one at high level and the other at a detailed level.
The question of why it feels as it does and not something different is a philosophical question that is not answerable by any process we know. It is the same type of question as “Why does something exist rather than nothing?”. Both questions feel as if they are asking something profound, but cannot acquire a meaningful answer. However, many questions about how emotions and feelings work and the differences between emotions at different times and in different animals can be clarified by a neuron level understanding.
Some receptive fields defined by the amygdala correlate with circumstances in which it is appropriate to place priority on strategic behaviours corresponding with some of the primary emotions. For example, the amygdala gets inputs from the sensory cortices and can therefore define receptive fields that correspond with the presence of threatening objects. The amygdala gets inputs from the frontal cortex and can therefore define receptive fields that correspond with the presence of threatening situations. These receptive fields have recommendation strengths in the basal ganglia in favour of avoidance behaviours in general. If there is sufficient such recommendation strength, the receptive field detections in the amygdala are released to the frontal cortex, where they contribute to generation of a population of receptive field detections with recommendation strengths in favour of different strategic avoidance behaviours. The population of receptive field detections in the amygdala and frontal cortex is subjectively experienced as fear.
The amygdala is involved in many of the primary emotions, but active populations in the frontal cortex alone that have a strong total recommendation strength in favour of some strategic type of behaviour will be experienced as feelings of different types.
WHAT ARE MOODS?
If a recommendation in favour of a specific behaviour of a strategic type is accepted and implemented, this could result in the receptive fields recommending the type no longer being detected, and the feeling may disappear. In other words, an angry action may result in the angry feeling disappearing a bit later. However, in some situations there may be recommendation strength in favour of some strategic type of behaviour but insufficient recommendation strength in favour of any sufficiently appropriate specific behaviour of the type. The absence of any such specific behaviour could mean that the continued activity of the receptive fields recommending the type is a recommended behaviour. In this situation, the feeling may persist for a long period of time.
Even if there is an implemented specific behaviour, the receptive fields recommending the strategic type of behaviour will generally have some small initial recommendation strength in favour of prolonging their own activity. If such prolongation is rewarded, the recommendation strength will increase. In this situation, once such a feeling has developed, it will tend to continue. Such prolonged feelings are called moods.
SOME QUESTIONS AROUND THE EXPERIENCE OF EMOTIONS
There are a number of questions that have been asked around the subject of how we experience emotions and feelings. Examples include:
What is the difference in brain state between feeling different ways, such as feeling angry and feeling fearful?
At the level of neurons, feeling angry corresponds with the activity of a population of pyramidal neurons with a predominant total recommendation weight in favour of strategic aggressive behaviours. The pyramidal neurons are located mainly in layer V of the orbital and medial prefrontal cortex and in the amygdala. The recommendation weights are the synaptic strengths of these pyramidal neurons on to medium spiny neurons (MSNs) mainly in the ventral basal ganglia. Activity of these MSNs results in release of the activity of the pyramidal neurons with the largest such strength to the dorsolateral prefrontal cortex, driving the activity of pyramidal neurons that tend to have recommendation weights in favour of different tactical behaviours of the aggressive type.
Feeling fearful is the subjective description of the activity of a different population of pyramidal neurons in the orbital and medial prefrontal cortex and the amygdala. Other feelings result from the activity of yet other populations of pyramidal neurons.
Note that any one pyramidal neuron in the orbital and medial prefrontal cortex and in the amygdala may have recommendation strengths in favour of multiple different strategic behaviour types, it is the predominant recommendation strength across the population that determines the feeling.
What are the similarities and differences between brain states at different times when I feel angry?
There can be multiple different populations of active pyramidal neurons that all have a predominant total recommendation strength in favour of the same type of strategic behaviour. Some of these populations may be fairly similar (i.e a high proportion of active neurons are the same), others more different. In some cases the differences are large enough that we label the subjective experience differently. For example, the subjective experience of different populations of active neurons in the orbital and medial prefrontal cortex and in the amygdala, each population with predominant total recommendation strengths in favour of aggressive behaviours in general, may be labelled annoyed, irritated, belligerent, furious, and irate. Release of the outputs of these populations to the dorsolateral prefrontal cortex will generate recommendations in favour of different ranges of tactical aggressive behaviours.
What are the similarities and differences in brain state between my feeling angry and someone else feeling angry?
In both cases the population of active pyramidal neurons in the orbital and medial prefrontal cortex and in the amygdala has a predominant recommendation strength in favour of aggressive behaviours in general. However, there are no correspondences between the receptive fields of individual neurons in the two populations. The receptive fields are defined within the same types of sensory inputs but different experiences. All pyramidal neurons are behaviourally ambiguous and do not correspond with individual behaviours or types of behaviours. Behaviours are only determined unambiguously by interpretation of total pyramidal neuron activity by the basal ganglia.
Do animals feel emotions?
Different populations of active pyramidal neurons in the brains of animals can have recommendation strengths in favour of different types of strategic behaviours. These different populations will be experienced by the animals as different feelings.
What is the difference in brain state between a human feeling angry and a dog feeling angry?
The differences lie in the different populations of active pyramidal neurons. As between different human individuals, there are no correspondences between individual neurons in the two populations. Because of the different sensory capabilities and experiences, there will be even larger differences between the receptive fields of pyramidal neurons in the two brains, and in their ranges of recommendation strengths. However, in both cases the populations have a predominant total recommendation strength in favour of aggressive behaviours, although the more specific tactical behaviours will be different and the detailed behaviours even more different.
Why does feeling angry feel as it does and not something different?
Feeling angry is the subjective description of a pattern of neuron activity with a predominant recommendation strength in favour of the aggressive strategic behaviour type, the result of this activity is a higher probability of selection of aggressive tactical and specific behaviours.
The question of why being angry feels as it does and not something different is not a well formulated scientific question. The statement “I feel angry” and the statement “A population of pyramidal neurons is active that has a predominant recommendation strength in favour of aggressive strategic behaviour both describe the same situation, one at high level and the other at a detailed level.
The question of why it feels as it does and not something different is a philosophical question that is not answerable by any process we know. It is the same type of question as “Why does something exist rather than nothing?”. Both questions feel as if they are asking something profound, but cannot acquire a meaningful answer. However, many questions about how emotions and feelings work and the differences between emotions at different times and in different animals can be clarified by a neuron level understanding.