femme Neuroscience Notes

Some Topics

Reptilian Behavior,  The R Complex

Paul Maclean referred to the basal ganglia as the reptilian brain or R complex. When we describe innate tendencies, we can point to the read only memory features of the brain stored in the neuron dense structures at the base of the cerebral hemispheres that use the neocortex as memory and processing multiple sources of information. The reptiles that were transitional to mammals are all extinct. Existing reptiles, such as snakes,  lizards and crocodiles, display some of the characteristic of ancient reptiles.

Maclean listed 24 behaviors typical of reptiles. While all these behaviors are manifest in humans, they all have undergone evolutionary modifications; they represent the most deeply imbedded, innate features of humans. Behavior is communication in the reptilian world with, for example, displays to greet, challenge and court other animals. Reptilean Brain are used to maintain the reptilian, hierarchical social order, just as they are in human societies. You can account for some of the most persistent and essential human activities as elaborations of reptilian displays.  Display patterning is retained as Read Only Memory in the globus pallidus, part of the R complex.

MacLean stated:" Reptiles have a perfect memory for what their ancestors learned to do over millions of years, but are poorly equipped for learning to cope with new situations." Transitions from mammal-like reptiles to fully formed mammals involved growth of the cortex and increased ability to learn. Cortical evolution added learning and evaluation capacity to the rather fixed programs in the reptilian brain.  Cortical evolution is linked to more sophisticated social behaviors which are linked to cooperation and the care of offspring. The concept of the limbic system represents an attempt to understand the linkages between the old and the new brain; between the outside world and body needs and responses. Cortical expansion developed sight and sound capabilities that replace smell as the primary source of information about the outside world. Rats and hamsters who develop without a neocortex display most of behaviors expected of normal animals; they mate, breed, feed and even have play behaviors. However, they cannot develop normally or even survive if key areas of their reptilian brain are missing or dysfunctional. The same can be said of primates including humans."

Three reptilian behaviors are worth special mention

Perseveration is the tendency for a fixed behavior to repeat or persist, even when the path is blocked or the real benefit of a behavior disappears. Eating behaviors, for example, are highly automated and resist change; "...reptiles are slaves to routine, precedent, and ritual..."

Frustration and anger are responses whenever seeking-behaviors are blocked, or threats are perceived. The least degree of drive-blocked discomfort is frustration; "...there is hardly anything more surely to upset than the alteration of a long-established routines."

Displacement occurs when there is no further supply of the gratification for the appetite or drive. Seeking behaviors shift laterally to find an alternative.