- The Human Brain
The Architecture & Connectivity of the Human Brain
The brain consists of three basic units: the hindbrain, the midbrain and the forebrain. The hindbrain includes the cerebellum, the upper section of the spinal cord and the brain stem. It controls respiration and heart rate and coordinates movements. The midbrain, which is the uppermost part of the brain, controls some reflex action. It also contributes to the control of the eye movements and other voluntary movements. The forebrain houses primarily the cerebrum, which is the largest and most highly developed part of the brain. The cerebrum is the source of intellectual activities, such as receiving and processing sensory information, learning, initiation of thoughts and actions, memorizing, planning, imagining, thinking, reading, playing, recognizing and behavior and social integration (National Institute of Neurological Disorders and Stroke (NINDS, n.d.), (Chopra, D., Tanzi, 2012). The cerebrum itself is split into the right and left hemispheres. Despite the apparent split, the two hemispheres are linked together by nerve fibers. There is a two-way crossover of signals involving the two hemispheres from the brain to the body and vice versa (NINDS, n.d.).
Source (NINDS, n.d.): Brain basics: Know your brain, p.2
Each hemisphere can be divided into areas or lobes. Each of the two frontal lobes (3) have their own distinctive functions. These lobes are located directly behind the forehead. They act as short-term sites regulating information processing, problem solving and decision-making processes. The motor area (4) is responsible for regulating voluntary motor movement. The Broca’s area (5) regulates the transformation of thoughts into words. The parietal lobes (6) process information received from the body. The sensory areas (7) receive and process sensory information from the body, such as taste, aroma and texture. These lobes also regulate reading and working with numbers. The occipital lobes (8) provide visual information received from the eyes and associate that information with previously stored information in memory. The temporal lobes (9) control memory, emotions, hearing, language and learning (NINDS, n.d.). The cerebrum and the cerebellum are coated with six layers of neural tissue called the cerebral cortex, commonly known as the “gray matter” in the brain. The largest concentration of neurons (approximately 40 billion) is located in the cerebrum. Most of the information processing activities in the brain occurs in the cerebral cortex (NINDS, n.d.).
The inner brain consists of four key components that regulate emotional states and facilitate automatic body movements. The hypothalamus (10) regulates multiple functions and acts as an emotional center. The thalamus (11) facilitates information exchange between the spinal cord and the cerebrum. The hippocampus (12) regulates long-term information storage and just-in-time information. The basal ganglia (not shown) are responsible for initiating and integrating movement (NINDS, n.d.)
Source (NINDS, n.d.): Brain basics: Know your brain, p. 4
The nervous system and the brain are composed of several different types of cells. The neuron is a primary functional unit of these cells, since the signals that regulate all sensations, movements, thoughts, memories and feelings travel through neurons. A neuron consists of three main parts: the cell body (13); the dendrites (14); and the axon (15). The cell body produces most of the molecules that a neuron needs to survive and perform its functions. The dendrites are outshoots of the cell body similar to the branches of a tree and are designed to capture signals. These signals then travel from the dendrites through the cell body, and leave the cell body down an axon (15) and migrate to another neuron, a muscle cell, or the cell of some other organ. Axons are usually wrapped in a sheath (16) which acts as an insulator to allow nerve signals to move faster and farther. Axons vary in length, depending on their connecting points in the brain.
Source (NINDS, n.d.): Brain basics: Know your brain, p. 5
Scientists have discovered that when a signal reaches the end of an axon, tiny sacs (17) are released. These sacs release neurotransmitters in the form of chemicals into the synapse (19), which cross the synapse to attach themselves to receptors (20) on nearby cells. The properties of the receiving cells can be altered by these receptors. The signal can of course extend the transmission to the next cell if the receiving cell is also a neuron (NINDS, n.d.). The connections between neurons encode memories and learning.
Source (NINDS, n.d.): Brain basics: Know your brain, p. 5
Brain – Mind Connection
For many years the scientific community has struggled to make the mind-brain connection. Not surprisingly, there is not a clear definition of the mind because of the mystery which surrounds it. From a religious perspective, mind is synonymous with soul, spirit and divine principle. Scientists have so far been unable or unwilling to define the mind. Daniel Siegel has probably provided the most comprehensive definition of the mind, which is gaining widespread acceptance amongst scientists. He defined the mind as follows: “a core aspect of the mind is an embodied and relational process that regulates the flow of energy and information’’ (p. 2). Siegel’s conceptualization of the mind, encapsulating the mind, brain and relationship elements, is illustrated in the diagram below.
Source: Adapted from Siegel (Siegel, 2010).
In this conception of the mind, the brain is seen as an organ having a variety of parts designed to perform some specific functions by themselves in combination with other parts. The mind is conceptualized as the flow of energy and information. This assumes that the mind regulates the energy. By regulating, Siegel meant monitoring what is happening with the energy and exerting an influence to alter the way things are happening. The information component represents the symbolization of what is happening. The relationship element of the model suggests a mind-body connection, rather than a limited perspective of mind-brain connection. According to Siegel, the mind regulates energy and information flow not only throughout the whole body of an individual, but also between and among people. The relationship function is for sharing of energy and information flow (Campbell, 2008). This brain-mind conception proposes the brain as a flexible, modifiable, malleable organ that can be altered with new experiences and thoughts. As mentioned earlier, the mind is the flow of energy and information. Therefore the dynamics of brain plasticity can be explained as the effects of the mind over the brain. New experiences and thoughts generate a flow of energy and information (mind), which acts on the neurons to trigger the development of new neurons and new neural connections.