This paper proposes a hypothesis about automatic nerve signal transmission and conscious primacy. If stimulated suddenly, people are initially unaware of the stimulation. Without conscious guidance, nerve signals are automatically transmitted via the strongest neural connections, thereby producing fast and involuntary behavior. Upon awareness of the stimulation, conscious primacy plays a role, and nerve signals are transmitted in consciously guided directions, thereby generating cognition and voluntary behaviors. When we repeat an action in a special environment, it will become a habit. This is because when nerve signals are repeatedly transmitted to action cells in a specific environment, neural connections between the specific environment and the action are strengthened. Upon return to this specific environment, nerve signals will be automatically transmitted, producing a stereotyped habit behavior without conscious thought. Facial expression, for example, is controlled by both emotion and cognition. Prior to emotional awareness of sudden stimulation, nerve signals are automatically transmitted, producing microexpressions consistent with emotion. Upon awareness, control switches from emotion to cognition, producing flexible facial expressions consistent with consciousness. The automatic nerve signal transmission and conscious primacy hypothesis suggests a new mechanism for producing different behaviors, reveals the essential difference and mutual transformation of stereotyped and flexible behaviors, and opens a new field for ethological study.
People generally believe that decisions they make and the corresponding actions they perform are consciously initiated and controlled. However, there is strong emerging evidence that unconscious processes influence decision-making [
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In this paper, we present the automatic nerve signal transmission and conscious primacy hypothesis. We first discuss the basic neurobiological mechanisms of automatic unconscious nerve signal transmission. Then, we discuss our hypothesis in the context of experimental findings and use it to explain the generation of psychological phenomena including habits, dreams, and cocktail party effect.
Automatic nerve signal transmission and conscious primacy occurs when sensory receptors convert stimuli into nerve signals, which transmit automatically according to the strongest neural connections in the neural network. If nerve signals reach motor neurons or effector neurons, instinctive and unconscious behavior is produced. However, under the control of consciousness, the brain may analyze the stimuli and change the direction of nerve signal transmission, thereby resulting in nerve signals transmitting to other motor neurons and producing conscious or voluntary behavior. Therefore, automatic nerve signal transmission occurs first. Upon awareness of the stimulation, conscious primacy plays a role. The change from automatic transmission to conscious transmission may then block instinctive and unconscious behaviors, which are replaced by conscious voluntary behaviors. However, if conscious intervention does not occur prior to automatic signal processing, then automatic nerve signal transmission will produce instinctive and unconscious behaviors.
Electrophysiological experiments are one of the most fundamental types of neuroscience experiments, in which responses are generated by electron stimulation without consciousness. In the 18th century, Luigi Galvani found that a dead frog’s leg kicked as if attached to a living being when the nerve was stimulated by electricity [
Nerve signals are transmitted by axons via action potentials, which occur following integrated postsynaptic potentials. The integrate-and-fire neuronal model is one of the most widely used models for analyzing behavior in neural systems [
Nerve signals transmit between neurons via synapses, which are the structure connecting two neurons. When electrical nerve signals reach the synapse, the presynaptic membrane releases neurotransmitters into the gap, which then bind to specific receptors on the postsynaptic membrane and generate postsynaptic potentials. The postsynaptic potentials combine into an overall signal by integrating in space and time. When integrated signals reach a threshold at the axon hillock, an action potential is generated and the signal can be conducted to other neurons.
The spatial distribution of synapses varies across the neuronal body and dendrites, and presynaptic neurons also release neurotransmitters at different times. Additionally, there are both excitatory and inhibitory synapses on a single neuron. Overall, postsynaptic potentials are integrated over space and time, as well as by the combination of excitatory and inhibitory synapses, to achieve postsynaptic potentials that exceed the firing threshold and generate action potentials [
The action potential is an all-or-none response; it is either on or off, like a light switch. When the integrated postsynaptic potential is below the firing threshold, an action potential will not occur at all, but when the integrated postsynaptic potential exceeds the firing threshold, an action potential will occur, regardless of stimulus intensity. If the threshold is not reached, the action potential cannot be generated, and nerve signal transmission is temporarily blocked until the postsynaptic potential reaches the threshold.
When nerve signals easily transmit between neurons via synapses, it is termed a strong neural connection; when nerve signals do not easily transmit to other neurons, it is termed a weak neural connection. One neuron typically has synaptic connections with multiple neurons; therefore, activation of one neuron can potentially propagate nerve signals to numerous connecting neurons. When the activated neuron has multiple strong neural connections, the signals will transmit via many pathways; however, when the activated neuron has strong neural connections with only one neuron, the nerve signal will only be transmitted via one pathway. If all neural connections to the activated neuron are weak, signal transmission will be terminated.
Hebb proposed the following hypothesis regarding neural connections: “When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased” [
There is a time lapse between being stimulated and being aware of stimulation, and conscious decisions occur after both components have occurred. Behavior cannot be guided by consciousness in the interval between these two events, but cerebral potential changes occur in the brain. The potential changes during this period of time are termed the readiness potential [
Unconscious movement has been observed in a visual search experiment [
Automatic nerve signal transmission and conscious primacy hypothesis explains that the original target and new object stimuli were received by the eyes and converted to nerve signals, which traveled automatically to the motor neurons and generated eye movements. When observers became aware of the target stimuli, the brain began to analyze target and instruction information, in order to make conscious decisions. Because of readiness potentials, at the initial stages without conscious control, nerve signals automatically generate eye movements toward the new object based on strong connections for a new object. After the readiness potential period elapses and observers are aware of the target, they follow instructions to make a voluntary goal-directed saccade to the target. This goal-directed event is accomplished by initiation of nerve signals that underlie the action of eye movement to the target. Therefore, observers were aware of seeing the target, but did not know that their eyes had moved to the new object.
Priming is a brief stimulus presentation that does not reach conscious awareness, but which can affect motor responses to subsequently presented target stimuli. In priming experiments, arrows are often used as primer and target stimuli [
According to the automatic nerve signal transmission hypothesis, when left-pointing primer arrows are presented, the stimulus is received by the eye and converted into a nerve signal that automatically travels in the left direction, because the participants are not aware of the stimulus and signal transmission is therefore not under conscious control. Additionally, when a left-pointing target arrow is presented, participants become aware of the stimulus from the left side, and voluntarily point their hands to the left. Because the directions of both the primer and the target are the same, the directions of automatic transmission and conscious transmission overlap, thereby accelerating the decision-making speed via compatible effects. In contrast, when the primer arrow points to the left and the target arrow points to the right, the direction of automatic transmission is left and conscious transmission is right; therefore, opposite directions reduce processing speed as a result of incompatible effects.
Consciousness enables human behavior to be flexible. However, the mechanisms of consciousness are not clear. For the present discussion, consciousness is defined as an ability to perceive stimuli and make decisions by analysis, which results in strengthened or changed behavior. Conscious primacy results in nerve signals being transmitted according to conscious guidance, thereby resulting in cognition and voluntary behavior.
In a study of free will, participants responded to two stimulus signals [
The automatic nerve signal transmission and conscious primacy hypothesis can explain the different peaks observed by Kühn and Brass [
Facial expressions reflect emotions. For example, people generally laugh when they are happy, and cry when they are sad. However, facial expressions do not always express actual feelings. For example, upon encountering a person who is disliked, people may smile and greet each other to be polite instead of displaying disgust; this interaction is the result of cognition. Affect and cognition are highly interdependent, but the contributions of affective primacy vs. cognitive primacy have been debated for several decades [
Emotions can also rapidly evoke facial responses in the absence of conscious awareness [
In daily life, people often have facial expressions that are consciously controlled but inconsistent with their underlying emotions. Prior to inconsistent facial expressions, there are subtle changes in expression, known as microexpressions. Microexpressions are brief facial expression for 1/25 - 1/5 s, and are evoked unconsciously by stimuli. Facial muscle activity that is consistent with the true emotion can be recorded during microexpressions. Microexpressions are also consistent with experimental findings that facial expressions are rapid and unconscious. However, the mechanisms for rapid changes to inconsistent facial expressions have not been elucidated. The automatic nerve signal transmission and conscious primacy hypothesis can explain the switch between two expressions. During the response to a facial expression eliciting stimulus, nerve signals automatically transmit to facial muscles and generate facial expressions rapidly and unconsciously. There is an initial reading potential period, during which the participant is not aware of the stimulus. Once the participant is aware of the emotion, the brain begins to be controlled by consciousness, at which time the conscious primacy principle initiates a change in nerve signal transmission. Under the guidance of consciousness, nerve signals for facial muscle movements are generated, thereby producing facial expressions consistent with cognition. The automatic nerve signal transmission and conscious primacy hypothesis suggests that during responses to stimuli, the facial expression consistent with the true emotion appears rapidly and involuntary at first, followed by a switch to facial expression consistent with cognition.
This rapid switching can be described using the example of a salesman who carefully prepared a presentation of new products. He thought that the presentation would be successful; however, after the presentation, the boss had opinions that indicated some dissatisfaction. Upon hearing these opinions, an unhappy expression appeared on the salesman’s face, but this expression switched to a happy expression almost immediately, before being noticeable to others. Common sense would indicate that the salesman should welcome his boss’s opinions, so he appears to be happy. However, the opinions are negative stimuli to the salesman, which are automatically processed by neural networks for unhappy emotions. The salesman cannot immediately be aware of his unhappy expression, but becomes aware of it only after the reading potential, at which point he can use cognition to switch to a happy expression. The voluntary reaction that results from cognition is slower than the automatic reaction to stimuli.
William James wrote in the book The Principles of Psychology, “When we look at living creatures from an outward point of view, one of the first things that strike us is that they are bundles of habits. It thus appears that habit covers a very large part of life.” Similarly to other animals, humans can repeat the same actions in the same environment, thereby forming habits and the associated actions. Examples include washing one’s face and brushing one’s teeth automatically after waking up every morning or always going home along the same route after work. These habits develop unconsciously, and it is possible to perform many actions automatically, without conscious control [
It is difficult to change habits that are formed in particular environments, and changing such habits requires intense determination. Automatic nerve signal transmission allows actions to occur automatically, thereby eliminating the need for thinking and decision-making. To overcome negative habits, the pathways of nerve signal transmission must be changed by conscious efforts, and therefore require conscious thought and intention. Under these circumstances, there is resistance to change, therefore, a person must be very determined to overcome the resistance. Tam, Bagozzi, and Spanjol [
The automatic nerve signal transmission hypothesis proposes that the brain is in a state of unconsciousness during sleep; but that nerve impulses continue to be transmitted in the cortex. One function of these nerve impulses is posited to be automatic transmission to retrieve memories, which contribute to dreams.
Freud used his psychoanalytic theory to analyze dreams and proposed that dreams are fulfillments of wishes or expressions of impulses that are repressed during awake states. He interpreted the implied meanings of dreams and used these interpretations to treat patients with psychological disorders. While psychoanalysis has many supporters, there are also many people who dispute its validity [
The contents of dreams are derived from memory, but dreams often alternate between multiple episodic memories [
A woman who prefers eating at home is driving on a freeway to Las Vegas. If she feels hungry, she will exit the freeway to find a restaurant instead of driving back home to eat. Although the neural connections between being hungry and eating at home are stronger than those between being hungry and eating at a restaurant, her consciousness forces nerve signals to transmit along pathways for exiting the freeway to find a restaurant instead of returning home to eat.
In the evening, while the woman is sleeping at a hotel in Las Vegas, the neurons that transmit information for hunger fire in her cerebrum, and the nerve signal will be transmitted via the main pathway for eating instead of for exiting the freeway because the connection between hunger and eating is very strong. In addition to the main pathway for eating, there are many side pathways. The nerve signals may therefore be transmitted along the strongest neural connections, which may be from cooking to fire to ambulance to kidnapping, or from cooking to food to farm to flower. If the woman does not like cooking, the nerve signals may be transmitted to restaurant, then from restaurant to hotel to flying to sky, or from restaurant to party to wedding to flower. Therefore, in the dream, the woman may dream of concepts related to cooking, including food, farm, flower, fire, ambulance, and kidnapping, or her dream may include restaurant, party, wedding, hotel, flying, and sky. This example explains how the plots of dreams shift constantly and discontinuously.
The cocktail party effect refers to the ability to focus one’s attention on a particular person’s voice amongst other voices and background noise. A common experience, such as while reading an interesting book, is that a person may not notice the content of conversation between people nearby. However, if someone mentions the person’s name, attention will shift to process this information. Experiments have demonstrated brain responses to a person’s own name while sleeping, even without conscious awareness of the name being presented [
The automatic nerve signal transmission hypothesis may explain why irrelevant topics can be ignored but processing can quickly shift when the information becomes relevant. When reading an interesting book with people speaking nearby, the story attracts the person, making him focus on its contents.
When a person is reading an interesting book and immersed in the story, even if there are other people talking nearby, he is still able to focus on its contents. The speaking voice, which is irrelevant, will pass through his ear and be transmitted by his brain, but the neural connections are very weak and the signal transmission will be terminated. The signal is therefore not consciously heard. A person’s own name is repeated by others every day, so this information is frequently transmitted by the neural networks and the neural connection is fortified. When one’s own name is mentioned while reading, the name impulse will automatically conduct to the associated neurons and attract conscious attention.
The automatic nerve signal transmission and conscious primacy hypothesis should be verified by experimental testing of associated hypotheses. If this hypothesis is supported, there may be extensive applications across scientific fields.
Is correct memory retrieval related to the strength of neural connections? It is clear that neural connections are plastic. Can the direction of memory retrieval be changed when neural connection strength is increased or decreased, thereby creating false memories?
Many antipsychotic drugs can reduce patient’s symptoms, but when patients stop taking the medicine, the symptoms come back. Does this mean that schizophrenia is related to strong but inappropriate neural connections? Is it possible that a false memory can be extracted, producing hallucinations, when nerve signals transmit automatically along a strong but inappropriate neural pathway? Maybe antipsychotic drugs inhibit the nerve signals’ transmission, temporarily bringing symptoms under control, but if the patient stops taking antipsychotic drugs, the symptoms reappear.
Is Alzheimer’s disease related to neural connections? Maybe as neural connections become weak, nerve signal transmission speed is reduced, slowing cognition. The connections become increasingly weak until they are damaged, resulting in an inability to extract the memory and dementia.
Is addiction related to neural connections? Can automatic transmission be used for information processing in artificial intelligence?
Are neural connections related to the mind? After birth, children receive stimulation from the external environment, and new neural connections constantly form and develop. By aiding mental maturation, a good social environment helps children achieve healthy mental growth.
Why do people’s cognition and behavior vary by environment? Maybe in different environments, people receive different stimuli that change neural connections, so the nerve signal transmission direction changes. This in turn changes cognition and behavior, so a good social environment is also important for adults.
Offensive language will strengthen people’s neural connections on associated pathways. If automatic nerve signal transmission has undesirable consequences, who should be held responsible? How can automatic nerve signal transmission on the associated pathways be avoided? What are the implications for freedom of speech?
Automatic nerve signal transmission produces good and bad habits. To overcome bad habits, the direction of nerve signal transmission must be consciously changed. Can bad habits be easily overcome by conscious effort? Is a strong will needed? Based on the mechanism of habit formation, how can good habits be maintained and bad habits be prevented?
Maybe someone who has obsessive-compulsive disorder has strong inappropriate neural connections resulting from a strong suggestion or experience. If automatic transmission on inappropriate neural connections can cause disorders, avoiding inappropriate neural connections and weakening existing ones will be very important.
The automatic nerve signal transmission and conscious primacy hypothesis proposes that nerve signals are repeatedly transmitted along a direction. The neural connections in this direction will therefore gradually increase and become strengthened. Furthermore, when responding to stimuli, nerve signals will be automatically transmitted along the strongest neural connections, thereby rapidly generating actions. As soon as stimuli reach conscious awareness, the nerve signals switch to consciousness-guided direction, thereby generating voluntary action. Automatic nerve signal transmission is a natural law in biology and the origin of all behaviors.
The author declares no conflicts of interest.
Shan, Z. (2017) The Automatic Nerve Signal Transmission and Conscious Primacy Hypothesis. Journal of Behavioral and Brain Science, 7, 165-179. https://doi.org/10.4236/jbbs.2017.74014