Biology 202
1998 Second Web Reports
On Serendip

Well, let's take a look at the brain. From being in class, my awareness about what I'm doing, what I'm seeing, what I'm hearing, what I'm thinking has come to reflect upon not just what, but how is it all being done by my brain. This morning I woke up, my eyes opened, I looked out my window, I saw the sun rising, it was this beautifully deep yellow/orange color. I thought, "How beautiful" and I smiled with a sense and feeling of wonderment. It could be said that I experienced nothing out of the ordinary this morning. Yet, if I could narrate these few activities in terms of the networking of neurons resulting in my eyes opening, my sight of the sun, my ability to perceive its color, my inner acknowledgment of its beauty and the emotions that sight evoked in me, you would be reading for a very long time and what I did this morning would indeed present itself in quite an extraordinary light. It is in recognition of this, with respect to the brain's aptitudes, that Howard Hughes in his paper, "Seeing, Hearing and Smelling the World" quoted May Pines in expressing, "We can recognize a friend instantly-full face, in profile, or even by the back of his head. We can distinguish hundreds of colors and possibly as many as 10,000 smells. We can feel a feather as it brushes our skin, hear the faint rustle of a leaf. It all seems so effortless: we open our eyes or ears and let the world stream in. Yet anything we see, hear, feel, smell, or taste requires billions of nerve cells to flash urgent messages along linked pathways and feedback loops in our brains, performing intricate calculations that scientists have only begun to decipher"(1). The world streams into us by the simplest act or thought which in the language of our brain is simply a magnificent piece of work.

Have you, for example, ever caught yourself in a feeling of ecstasy? Ever wondered how your brain translates whatever it is that you're experiencing into that feeling of joy, or fear, or anger? Scientist can now harbor these types of questions by pointing to specific regions of the brain from which emotions arise. The brain as a whole is divided into a series of systems such as: the Limbic System, the Basal Ganglia, the Prefrontal Cortex, the Cingulate system and the Temporal Lobes. The insights about the particular regions of the brain relating to emotions developed fairly recently in the 1950's. It is the Limbic System, the brain structures bordering the ventricles, that is associated with emotions. The identification of that group of brain structures as the Limbic System came from observing the relational states associated with these regions and emotional behavior. These regions have been understood by scientist to function by a connection model depicted as the Papez circuit. This circuit identifies and conjoins the elemental structures of the system in this manner, "The Papez circuit postulated a role for the cingulate cortex in detecting emotional meaning from sensory information impinging upon the neorcortex. The cingulate cortex projects to the hippocampus via the enthorhinal cortex. The hippocampus projects to the hypothalamus, which in turn projects to the anterior nucleus of the thalamus via the mammilothalamic tract. The anterior nucleus of the thalamus projects back to the cingulate cortex, thus completing the circuit"(2). The Limbic system is also characterized by scientist in these terms, "The limbic system is in the subcortical area at the center of the brain. Considering its size-about that of a walnut----it is power packed with functions, all of which are critical for human behavior. This is the part of the brain that sets a person's emotional tone and stores highly charged emotional memories, both positive and negative"(3). And it is about the size of a walnut, a list of its functions involve setting the emotional tone of the mind, altering moods and emotions, and modulating motivation(4). Image that! Imagine the billions of neurons responding to inputs and output commands resulting in a sigh, a smile, a frown, a cry of anguish. Imagine it, if you can.

Then, you have the amygdala described as, "the fingernail sized almond shaped organ of the Limbic System"(5). It has been labeled as a sort of 'emotion central' that is in direct dialogue with the thalamus, a relay station for sensory input. The sensory input is received from the neorcortex, the hippocampus and the cingulate cortex. The way the amygdala is believed to work is to "mediate fearful emotions through relaying the input from sensory cortex to the hypothalamus via the central nucleus"(6). Since the hypothalamus is identified with regulating the autonomic nervous system, the amygdala, through this connection, directly affects behavior controlled by this system. These insights are supported by experiments which reveal distortions in certain emotional responses as a result of damage of some sort to the amygdala. It is reported that, "Patients with damage to the amygdala have difficulty recognizing expressions of emotion. In contrast, stimulation of some parts of the Amygdala can produce anxiety and fear, while stimulation in other regions produces violent, aggressive behavior"(7). This set of observations can be understood with the cognizance that the amygdala's effect on the hypothalamus relays into a spectrum of emotions such as fear, anger, heart rate, etc.

Looking at these sections of the Limbic System, one cannot ignore its significance to the human body. But once the emotions of fear, for example, has been interpreted through the neuron activities in the regions outlined above, it is the Basal Ganglia that orchestrates the connection of these feelings to movements. This area of the brain which is located right over the Limbic System is described in this fashion, "The Basal Ganglia integrates feelings and movement. This is why you jump when you're excited, tremble when you're nervous or freeze when you are scared"(8). Other patterns of behavior associated with the Basal Ganglia includes the setting of anxiety level in an individual as well as saving behavioral patterns learned from the past. Another region of the brain which is closely associated with the functions of the Limbic System is the Prefrontal Cortex. This region is also very much defined by its influence in areas of emotions and feelings. The difference between this system and the Limbic system is highlighted in their evolved role of conveying emotions. The contrast in the two systems is thus described, "Even though the Limbic System controls mood and libido, the prefrontal cortex is able to translate the feelings of the Limbic System into recognizable feelings, emotions and words, such as love, passion or hate"(9). The Prefrontal Cortex is further associated with functions such as conscious thought, critical thinking and concentration. It could be said of the Prefrontal System that it is where the light switched is located when it comes to our cognitive abilities. Once we are able to formulate ideas and thoughts, the Cingulate System kicks in helping us go from one idea to another. This system has been associated with allowing us to shift our attention from one thing to another. Its location and function is summarized in this way, "At the top, in the middle of the frontal lobes is an area of the brain termed the cingulate gyrus. It's the part of the brain which allows you to shift your attention from one thing to another, to move from idea to idea, to see options in life"(10). This part of the brain saves us from being trapped in one set of mind. Not surprisingly, obssessive-compuslive behavior is related to that region of brain. This kind of behavior is characterized by a complete surrender of one's focus to one set of thoughts or activities.

The last area to be considered in this overview of the brain and its various functions briefly focuses on the many regions which contribute to our sense of identity. It is reported that, "The Temporal Lobes, on either side of the brain behind the temples, store memories and images; they store our experiences. They help us define our sense of ourselves. When our temporal lobes function normally, we have a clear sense of who we are, our life situation and the nature of things around us"(11). This region is described as having a dominant side which incorporates abilities such as understanding and processing language, long term and short term memory, visual and auditory images. This side is contrasted with a non-dominant region which engages in areas such as music and rhythm. In clinical research, it has been observed that behaviors such as social withdrawal and violence can be traced to deformities in the Temporal Lobe regions.

In light of all this what would the psalmist say? First what am I inclined to say? The truth is that in the process of writing this paper, I've come to understand better the inclination to make a statement such as, "The brain is behavior, there isn't anything else". It sure appears like that as far as what we see can and experiment with goes. After all, just looking at an overview of the brain shows a lot of growth in our understanding of many behaviors from the viewpoint of pattern of activities in its systems. It is indeed quite tempting a conclusion to make, even when contemplating all the questions concerning those systems which leave us in mystification and wonder, even in the mist of all the "I don't know". So what would the psalmist say? I believe something to that effect, "For it was you who formed my inward parts; you knit me together in my mother's womb. I praise you, for I am fearfully and wonderfully made. Wonderful are your works; that I know very well".

References

1. The Brain and Our Senses from journal Does God Exist?, Nov/Dec 1996

2,6,7. Emotion and Rhythms -- lecture from "Neuroscience, a course taught at The University of Toledo by William S. Messer, Jr., Ph.D."

3,4,8,9,10,11. Brain Systems and Behavior from the Amen Clinic

5. SENSE OF SMELL - BRAIN CHARACTERISTICS


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