PRIMARY NEUROSCIENCE RESEARCH UNDERLYING EACH STEP OF ALTRUISTIC BRAIN THEORY

The title of this post is identical to the title of a chapter in an important book by Donald W. Pfaff, Ph.D. with Sandra Sherman. The subtitle is “How We are Naturally Good.”

Neural Basis of Step 1: How We can Represent an Act in Our Brain Before Undertaking the Act

Corollary discharge refers to the extra motor signals that are sent over to the sensory pathways to notify the sensory pathways that the world will appear to change as the result of movement. When we move our eyes to the right, the world does not appear to jump to the left. This is because the same motor neurons that tell the eye muscles what to do also represent the movement to the visual system so that the visual system expects such an eye movement. ‘Corollary discharge’ means the common phenomenon that the brain represents intended movements to its appropriate sensory system.

Neural Basis of Step 2: How We can Perceive the Target of an Intended act.

When we see another person this visual information is processed by our brains so that an image of that person is virtually ‘constructed’ in the brain. This occurs in a area of in the inferotemporal cortex which is much further forward than the primary visual cortex, which is at the very back of the brain. There are neurons here that will respond only to faces. Some neurons respond best to faces shown in profile; others respond to frontal views of faces. Neuroanatomical work by MIT Professor Nancy Kanwisher used functional magnetic imaging (fMRI) and found a convincing “face recognition module” in one part of the human brain. She even identified specific electromagnetic waves associated with the categorization of visual stimuli as faces and the successful recognition of individual faces.

What about the case when the beneficiary is not right in front of the person who is going to perform an altruistic act, but instead as a generic ‘image’ —some unknown wounded person. In such a situation, the visual representation of that generic person must be there in the cortex, but neuroscience does not yet know how that envisioning process is initiated.

To summarize, we all want our percepts—our sensory signals—to be clear and accurate, a neurophysiological challenge. ABT posits the opposite, the challenging case in which our sensory signals are unclear as the next step explains.

Neural Basis of Step 3: How Images of Actor and Target Can Merge in the Brain

Here is one way to understand how the merging or joining of images can take place. It has to do with ‘cell assemblies,’ groups of neurons that enable us to recognize faces. If any one part of a cell assembly is turned off, the function of that cell assembly is not accomplished. It is easy to make a cell assembly not function, by altering the chemistry of one of those cells in the assembly or by altering their hookups. So if cells are not working in the relevant part of the cerebral cortex, a special part of the temporal lobe of the cerebral cortex essential for face recognition, that would reduce our ability to recognize and think about a person’s individual visual image, and correspondingly increase the opportunity to see the other person’s image as our own. As a consequence, using mechanisms spelled out later, the lack of precision of facial perception can be achieved as required by ABT.

It is clearly plausible to propose a reduction in operational efficiency of neural circuits the discriminate between oneself and ‘not self,’ that is, another person.

One could depict an act to be avoided. A young man might be angry and intend to push someone in front of a bus. But during the interval, his mental image of the would-be target merges with his own. He is left with an instantaneous image of himself being pushed in front of the bus. Hence he desists.

Pfaff proposes three ways of merging images of two persons. So although proof of this process is not provided, possible avenues of accomplishing this merger are proposed.

Neural Basis of Step 4: When the Brain Evaluates an Impending Action, then it causes a prosocial act.

Step 4 unfolds when the positive or negative import for feelings and thus for intended action is determined. The cortex needs to link the blurred image and intended action to parts of the brain that will evaluate what results they might lead to. Then the message, appropriately processed, will be headed for an emotionally loaded ‘ethical switch.’ a mechanism in the brain influenced by positive or negative emotional consequences.

Neural Basis of Step 5: The Decision and the Act

In Step 5 a classic Yes/No decision that the central nervous system has to make all the time it is carried out. Carrying out the behavior uses ordinary motor control neurophysiology of the sort that has been studied for almost a century. This is the simplest step of the theory because the emotional valence of the considered act has already been realized. If in Step 4, the intended action leads to a positive result, then the action will be carried out. If an intended action leads to perceived harm of the imaged self achieved in Step 3, then the action will not be carried out.

Where in the brain does this final step take place? Modern neuroscience’s best guess at the time of this writing would be in an obscure part of the cerebral cortex called the ‘insula.’ Insula neurons respond to pleasant states (leading to the performance of the intended response) or to the impression of moral disgust (leading to abstention from the intended response). The output of the insula connects to motor control systems in the forebrain that allow the insula to ‘weigh in’ on the performance of the motor act that is being considered. If there are good consequences, then it’s Go! If, however there are bad consequences for the act’s intended recipient, then it’s No Go.

Pfaff raised the question as to when the decision to perform an altruistic act has been completed, what neurobiological forces ensure that the act will actually be carried out? Does the brain proceed with the motor act based on ‘goodness for its own sake,’ or are there strong biological forces that have evolved to encourage prosocial behavior? The answer is the latter, and those forces are ground in our instincts toward sex and parental care, that is, in the biology of reproduction. A tremendous amount of primary neuroscience research tells us how this works. Those studies will be discussed in the next posts.