In this, our first in depth post on the psychoanalytic brain, we will begin by looking at the basics: the evolution and structure of the human brain. This fascinating organ, weighing just three pounds, is the culmination of hundreds of millions of years of evolutionary development. It is thought to be responsible for every lived subjective experience of consciousness we have - I say ‘thought to be’ with good reason. As scientists we are not proclaiming to know absolutely beyond doubt that this is the case, and the purpose of this series of posts is to familiarise the reader with the predominant paradigm of understanding in the field. There are other theories of nervous system functioning and its relationship with mind. What follows is the most commonly subscribed to approach within the neurosciences. So let’s go ahead and take a closer look at its interesting evolutionary history and the development of its neuroanatomy, and what this might teach us about psychoanalytic theories of mind.
The human brain, with all its complexity, did not just materialise overnight. It is the product of an extensive, and incredibly long, evolutionary process that spans hundreds of millions of years. In order to really understand the human brain, and mind, it is necessary for us to first trace its evolutionary history. One particularly useful framework for conceptualising human brain evolution is the "Triune Brain" theory, proposed by neuroscientist Paul MacLean in the 1960s. While this model is somewhat simplistic (descriptively - not in terms of its accuracy) it has been refined by more recent research, and provides a useful perspective for understanding the brain's evolutionary journey.
The most primitive component of the brain, according to Maclean, is what he termed the Reptilian Complex. It includes the brainstem and cerebellum which are situated just at the point where the spinal cord develops into more substantial and complex neural material, which gradually develops into brain. This, the most ancient part of the brain, is responsible for basic survival functions such as breathing, heart rate regulation, and balance. It bears a striking resemblance to the entire brain structure found in reptiles, and we humans share remarkably similar structures, neurochemicals, and functions with these creatures that date back to approx 550 million years ago.
As evolutionary process progressed, the Paleomammalian Complex, or limbic system, began to emerge in early mammals, somewhere about 250 million years ago. This development brought about structures and circuits involved in emotions, motivation, and memory formation, including the amygdala and hippocampus - we will be hearing a lot more about these two structures in subsequent posts. These additions to the ‘hardware’ allowed for a much more sophisticated and nuanced discrimination of, and response to, events in the animal’s environment.
According to Maclean’s model the most recent neuroanatomical development, in evolutionary terms, is the Neomammalian Complex, or neocortex, which appeared on the scene about 70 million years ago. This structure is especially well-developed in primates, reaching its pinnacle in humans. The neocortex is responsible for higher-order cognitive functions, including language processing, abstract thinking, and complex problem-solving abilities. This evolutionary perspective provides us with insight into why we can sometimes find ourselves acting on instinct or emotion rather than reason. When that happens we find ourselves under the influence of older parts of our brain, which evolved a long time before the capacity for complex thought. In times of crisis and great stress there is a tendency to regress to these default structures and processes.
Now let’s work our way up, as it were, through the major structures of the brain, travelling from the Reptilian Complex through the Paleomamallian Complex to the Neomamallian Complex. The hindbrain, located at the base of the brain, includes a collection of neurons known as the medulla oblongata, which controls vital functions like breathing and heart rate, and the pons, and acts as a relay station between different parts of the brain.It also contains as structure called the cerebellum (little brain), which coordinates movement and balance. Directly opposite from the cerebellum we find a structure called the pons, heavily involved with the generation of REM sleep, and will become important for us when we start to talk in a lot more detail about dreaming and memory.
Above the hindbrain lies what neuroanatomists refer to as the midbrain, sometimes known as the mesencephalon - the terminology can take some time to get used to, but will come in time with more reading. Technically the midbrain is part of the brainstem - the uppermost part. The midbrain houses structures involved in visual and auditory processing, as well as motor control. While smaller than other brain regions, the midbrain plays a crucial role in sensory integration and movement coordination it is like a switching station facilitating communication between the forebrain and hindbrain. It includes structures like the inferior and superior colliculi - structures important for memory and vision, the pineal gland, and several cranial nerves enter and exit through the midbrain. A major source of dopamine, the substantia nigra, is situated in the midbrain and has projections, another word for neural pathways, to the basal ganglia, a subcortical structure very important for implicit memory.
The forebrain, the largest and most complex part of the human brain, contains several critical structures. The cerebral cortex, the brain's outer layer, is responsible for higher-order thinking and cognitive processes. The basal ganglia, while technically subcortical, and therefore cognitively non-conscious, play a vital role in motor control and learning. The limbic system structures, including the amygdala and hippocampus, are also located in the forebrain. The limbic system is a theoretical construct with many neuroanatomists disagreeing about its exact geography and neurological territory. It is crucial for the processing of emotion and for memory formation. The limbic system is closely related to another neuroanatomical concept the Papez Circuit, which emphasises memory processing much more than emotion and affect - however, there is considerable overlap to be found between the two concepts. The thalamus, a structure situated at the very tip of the spinal cord and brainstem, serves as a relay station for sensory and motor signals - all of our sensory information with the exception of olfaction, which wires directly into the Papez circuit/limbic system, travels through the thalamus before being distributed around the brain to different modality-specific locations. Its function is often compared to that of a server in a computer network. While the hypothalamus, which as the name suggests is a collection of neural structures that ‘hang’ around and below the thalamus, detects and regulates basic needs such as hunger, thirst, sexual arousal, and body temperature.
Moving up into the upper reaches of the brain we encounter the cerebral cortex. It is divided into four lobes, each with specialised functions. The frontal lobe is involved in planning, decision-making, and trial action. The parietal lobe situated at the side and rear of the cortex processes sensory information and contributes to spatial awareness. The temporal lobe is crucial for memory, emotion, and language generation and comprehension. The occipital lobe is primarily responsible for processing visual information. There is also a ‘hidden’ fifth lobe that lies below the parietal and temporal lobes called the insular cortex. In evolutionary terms the insula or insular cortex is a lot older than other parts of the cortex and it plays a major role in how our bodies are represented at the level of cortex and mind.
Clearly, this is a very much simplified and reductive account of human neuroanatomy, as the limitation of this format dictates. It is important to remember that the human brain contains approximately 86 billion neurons, each connecting to thousands of others, forming trillions of intricate connections. This enormous neural network allows for the remarkable complexity of human subjective experience. It is also important to bear in mind that the brain is not a static organ. We are so used to seeing it depicted in 2D and 3D formats that we tend to conceptualise it as being fixed and rigid, and can forget that it is constructed from soft tissue and is in fact malleable, fluid, and flexible. It has the remarkable ability to change and adapt in response to our environments and experiences, we call this capacity neuroplasticity. Neuroplasticity is fundamental to learning, memory formation, and recovery from brain injury. We will be learning a lot more about it in future posts too.
The relationship between brain structure and psychoanalysis is interesting, and studying it is helpful in furthering the understanding of many psychoanalytic phenomena. For instance, the idea that much of our mental activity occurs outside of conscious awareness aligns with the fact that a significant portion of our brain's activity happens in subcortical, and therefore, cognitively non-conscious regions of our nervous system. The interplay between the limbic system, particularly the amygdala, and the prefrontal cortex helps to explain the challenges and limitations in emotional regulation that are frequently the focus of our clinical work. The role of the hippocampus in memory formation, consolidation, and reconsolidation provides a neural basis for understanding how experiences, both typical and traumatic, are processed and stored in the brainmind. Similarly, the immature nature of our nervous systems at birth, and throughout the comparatively long developmental period of the human brain, aligns neatly with many psychoanalytic theories about developmental stages. Also, the activation of various brain regions during REM sleep, including areas involved in emotion and memory, provides a neurological framework for the better understanding of dreams and their interpretation.
This post is intended to be a jumping off point. I encourage you all, if interested, to do some further research of your own around neuroanatomy. It really helps with finding your way around this sometimes very technical literature. YouTube is your friend in this regard, and many excellent resources can be found there. Drawing the brain is a great way to get to know your way around it too!
As we continue with our exploration of the concept of the psychoanalytic brain, we will go into more detail about how these brain structures and their functions relate to psychoanalytic concepts.
© 2024 Paul Moore
This series of posts on neuropsychoanalysis is derived from a postgraduate module I teach at Trinity College Dublin. The module, "The Mind-Body Question in Psychoanalysis" (MBQiPA), is part of the M.Phil. in Psychoanalytic Studies in the School of Psychology. I have developed and delivered the MBQiPA module in various forms for over 16 years.
Brilliant. Just the ticket for psychoanalytic trainees in the 21st century.