Different neurotransmitter systems and pathways are associated with different functions. Most neural networks function with a sequence and combination of neurotransmitter systems (i.e.: serotonin, norepinephrine, dopamine, etc.). In this discussion, I shall organize neural networks according to function.
Let's look at some neural networks which regulate mental functions in greater detail. In a state of health, emotions accurately reflect our current life situations and are fast and approximate adaptive modulations. Cognition is slower and weaker but more able to adapt to unique situations. In the awake state there is a constantly changing allocation of resources between the following functions:
To define a few of the more complex functions:
Processing is the association or organization of information. It may be a fairly simple, unimodal association such as associating something that unites two perceptions in the same sensory modality. It may also be complex such as a complex multimodal or polymodal association: the other driver's face, the sound of screeching brakes, breaking glass, the smell of gasoline, the feeling of intense fear, a bodily pain, a perception of imminent harm and helplessness.
Learning is processing that occurs over time as we sensitize or desensitize memory associations. Creative processing is making new associations beyond those that were drawn from experience and memory. Processing occurs simultaneously with both cognition and feelings.
When an event occurs, that experience is processed or integrated with existing information. If an experience can not be processed immediately, that memory is then repressed to be processed at a later time. If there is an inability to process emotionally significant information, the memory is either consciously suppressed or imagery is implemented to repress the memory from consciousness. The memory may, however, keep returning to consciousness at times of decreased activity and free association, or at times when certain cues trigger recall.
To keep such memories suppressed and repressed requires a disassociation from any cues (emotions and other perceptions) which evoke recall. While adaptation occurs when these memories are integrated with other information, conversely, pathology occurs when these memories become increasingly disassociated at the sacrifice of increased impairment in adaptive capability.
Emotions are modulations, which alter functioning, thereby facilitating adaptation. In a state of health, both the intensity and type of emotions reflect the current life situation. The emotional state is constantly changing in response to changing life events and is a blend of different arousal levels of different emotions. It is unclear which emotions could be considered primary with distinct neural centers and which emotions are a blend of other primary emotions. A focal point of emotional functioning is the limbic system. Emotions alter perception, processing, physiological functioning, and behavior. Emotions are primarily instinctual and are impacted by emotional memory, cognitive memory, cognition, somatic factors and other systems. Apathy is a lack of emotional reactivity. Lability is an excessively rapid shift of emotions.
Individual differences in basic emotional temperament and learning results in different basic emotional set points and different capacities to shift appropriately in response to life events.
Mood is the external appearance of the emotional state, while feelings are the internal perception of the emotional state. Emotions appear to originate in the limbic system and are transmitted to the viscera where they are perceived as feelings.
Alexithymia is an inability to recognize, experience and describe feelings. Anhedonia is an inability to recognize, experience and describe pleasurable feelings. There may be partial degrees of both alexithymia and anhedonia.
Since the capacity to feel emotions is a critical component of empathy, alexithymia can result in a decline in the capacity for empathy. A number of conditions can cause alexithymia including autism, Asperger's Syndrome, developmental failures, PTSD and injuries from encephalopathies
Anticipation is a complex emotional perception of the future and is experienced as a feeling about the future.
Imagery is the capacity to experience what does not currently exist. It allows us to recount and process a memory from the past to create our own view of the present and imagine and plan what may be in the future. Neither creativity nor delusion could exist without this function.
Our imagination is always active. In the wakeful state it is partially suppressed by current perceptions but during REM sleep, this function is disinhibited. Our imagination is most effective when it is well integrated with an accurate assessment of our life experiences. It is sometimes difficult to differentiate past imagination from past memory, current imagination from current situation, and our image of the future from true possibilities.
Imagery is significant in a number of processes relevant to interpersonal functioning. Object constancy is a psychoanalytic term describing the ability to recognize a person exists even when they are not seen. Observing ego is our capacity to imagine how others may perceive us. Empathy is our capacity to imagine the emotional perspective of others.
In psychiatric illness, there are impairments in the ability to integrate imagery with reality and unique patterns have been demonstrated on brain imaging tests.
A deficiency of imagery inhibits creativity. A mild deficiency in the ability to differentiate between imagery and reality causes distorted perceptions and beliefs while a more severe degree of impairment causes hallucinations and delusions.* Some degrees of reality testing are seen in many psychiatric conditions including post-traumatic stress disorder, complex partial seizure disorder, encephalopathy and psychotic disorders.
Arousal is the intensity of a mental function. Sleep-wakefulness arousal is a gradation from deep sleep to a high level of alertness. Emotional arousal is the intensity of an emotional state, i.e.: states such as fear, libido, anger, hunger, jealousy, dysphoria, etc.
Motivation is an emotional modulation, which prepares us to behave in a particular direction. While anticipation is an afferent emotion, motivation is an efferent emotion. Apathy is a diminished capacity for motivation.
Hopefully we can rapidly shift the allocation of mental resources in response to current adaptive needs but we all allocate our mental resources in different ratios. Attention Deficit Disorders as well as many other traits and pathological states can be conceptualized from such a perspective.
One group of pathways is best described as the adversive or harm-avoidance pathways. These pathways modulate functions that allow us to be repelled from something perceived to have a potential for harm. Another group of pathways, reward or pleasure seeking which includes sexual, feeding and bonding functions, attracts us towards people and things that we perceive as pleasurable. Whether repelled or attracted these two major pathways have similar attributes. Harm perception is associated with negative internal perceptions while the reward pathway is associated with pleasurable, internal perceptions.
A simple perception of harm is the perception of pain. More complex perceptions of harm take the form of the more complex emotions in the harm-perception pathways. Likewise, the perception of pleasure takes both a simple and a highly complex form. For example, euphoria is an extreme of an emotionally pleasurable sensation and dysphoria is an unpleasant emotional state. When we are acquiring pleasurable feedback, we may feel some degree of euphoria, which motivates us to further pursue activities associated with this emotion. We may then respond to this by projecting ourselves into our environment, a function that is associated with increased activity of the serotonin system of the brain. Contrary to euphoria, dysphoria is an unpleasant emotional state where we experience negative feedback. This is associated with behavior inhibition and decreased serotonin activity. Mild degrees of both euphoria and dysphoria guide and mold our behavior and learning on a daily basis.
Different mental functions and emotions recognize harm based on a dimension of time. (See diagram: Time and Harm Recognition) In looking at harm avoidance, we notice several components to this pathway - perception of harm, modulation, processing and the motor pathway of harm avoidance.
Let us first look at the diagram showing the Sequence of Normal Mental Functioning, then the basic Fear Sequence, Threat Awareness Processing, Response to Threat Recognition, Threat Perception, Threat Processing, Threat Modulation-Emotional, Fast and Slow, Threat Avoidance-Efferent.
Adaptation requires a constant shift in the allocation of resources to adapt to constant changes in the internal and external environments. We all have different genetic endowments resulting in different abilities to adapt to environmental fluctuations and extremes. Traits that are adaptive in some situations are maladaptive at other times. When an individual possesses extreme traits and/or is in an extreme environment, a pathological vicious cycle may be triggered.