A good place to start exploring cognitive science is with the brain. When we talk about cognition we are talking about a process that takes place in the brain. This process involves the entire brain. Therefore to understand the process the reader must have some knowledge of the parts of the brain and their purpose and their location. In addition, it is important to know how the brain communicates. It is different from the rest of the nervous system in that its’ electrical communication is produced chemically and the neurons never touch unlike nerves which much touch. I have included a quick overview of the brain with pictures from the National Institute of Neurological Disorders since we will be talking about the brain quite a bit so I am hoping this will be a good reference.
Biology of the brain
The brain is one of the more intricate organs in the body. It only weighs about three pounds but it is where you intelligence, interpreter of the senses, body movement, and behavior all begin. It is in a protective fluid that is encased by the skull. The brain is the center for all our individual qualities as a person. The brain is one of the most difficult of our organs to study. It is not until the last 10 years that we have really been able to look at the human brain while it was functioning. We could study the behaviors produced by the brain but the way in which that was happening alluded us until MRI and PET scan entered the medical and scientific world.
All the parts of the brain work together but each has its own responsibilities. There are three main sections, the forebrain, the midbrain and the hindbrain (1). The hindbrain which is the cerebellum controls body functions such as respiration, heartbeat. It coordinates movement and it is also involved in learned movements such as typing. The upper part of the brain stem is called the midbrain. It is responsible for coordinating movement. It controls reflexes and voluntary and involuntary eye movement. This is sometime called the animal brain as it controls much of the autonomic nervous system and is the most primitive part of the brain.
The forebrain is the biggest part of the brain and it is also the most highly developed, what you can see in (2) is the cerebrum. There are many structures hidden beneath it. It is usually the cerebrum that you will notice in pictures because it is the largest area. It is the source or intellectual activities. This is where you plan and carry your memories. This is where your imagination lies. Your ability to read and write is in the cerebrum. All those kinds of activities are controlled here.
The Forebrain ——- The Midbrain ——– The Hindbrain
The cerebrum is split into two hemispheres. Even though there are two halves the two work together. They communicate through the corpus collasum which is a connection of nerve fibers. The two halves may look the same but they do different things. The ability to form words is in the left side while the ability to reason and so abstract thinking is mainly in the right side. The signals from the brain to the body cross over. So the left side of the brain controls the right side of the body. It works in reverse too. The left side of the body communicates with the right side of the brain. So if you had a stroke in the right side of the brain the left side of the body would be effected.
Layout of the Brain
Each side of the brain is divided into lobes, each having their own responsibilities. (3) the frontal lobes are right behind you forehead. They plan, imagine, and reason. This is the work horse of the brain. This is also where you short term memories are stored. In the back of the frontal lobes (4) you will find the area that controls your movement. Notice also Broca’s area (5) this forms you thoughts into word. The parietal lobes (6) control taste and smell and area (7) is the primary sensory areas. The receive information from the rest of the body such as taste, temperature, and movement in the body. This is also the area you use when reading or doing math.
Number (8) is the occipital lobes. This is the vision center of the brain. It processes information sent in through the eyes. Finally (9) the temporal lobes this is where you make sense of music. Information from the ears comes to this location to be interpreted here. Remember you five senses just code information from the outside world and the brain reads the code and gives it meaning.
The Cerebral Cortex
The cerebrum and the cerebellum is encased in a layer of tissue about the consistency of a punch ball although it is a bit thicker. This is the cortex. This is where most of the information processing takes place. When people talk about gray matter, this is what they are usually talking about. The folds add to the surface area allowing large amounts of information to be processed at the same time.
The Inner Brain
So far we have just looked at the outside of the brain that is visible just beneath the skull. There are other parts of the brain that are hidden inside. These are the parts that determines our emotions, change our perceptions and responses to the world and maintain movement of which you are not thinking, such as breathing, digesting food, blinking and so on. The hypothalamus (10) wakes you up in the morning. It also controls anger, exhilaration or unhappiness. The thalamus (11) is the clearing house for information going to the spinal cord and the cerebrum and also for information returning from the spinal cord. The hippocampus (12) is responsible from putting things into your long term memory and retrieving them as needed. The basal ganglia are nerves surrounding the thalamus responsible for integrating movement. This is the area effected by Parkinson’s disease.
What Makes It All Work?
The primary cell in the brain is the neuron. All sensation, emotions, thoughts, memories and movements result from signals that have passed through neurons. This is done by a chemical reaction. You have likely heard of neurotransmitters. They are the chemicals produced by the neuron. Neurons cluster in groups called synaptic connections which form thought, ideas and reactions that are stored in our memory. Memory causes these reactions to be repeated if we do not think about changing them. The names indicated on the drawing are (13) cell body, containing the nucleus and your DNA (14) dendrites, receive neurotransmitter, or information (15) axon passes signal on, (16) myelin sheath which in an insulator and speeds transmission.
The synapse is where a signal passes from the neuron to another cell. This is done by the release of the neurotransmitter (chemical) which is picked up by another neuron. The signal continues on until the action desired is completed. This likely involves thousands maybe millions of neurons
The Function of the Brain: Sensation and Perception
As we learn more about the function of the brain, we begin to first understand the more simple systems such as sensation, motor control, and autonomic regulation. We know less about the more complex functions of the brain such as memory, problem solving and language. First we must understand neural information processing. We certainly cannot give an exhaustive description here but we will attempt to describe a few connections between neural processing and cognition so that the reader can get an idea of how cognition may be physically implemented in the human brain.
The nervous system is more than just the brain. It includes various sensory systems that gather information from various parts of the body. In many cases the information processing that takes place outside of the brain is considerable. The human brain contains about 100 billion neurons each one has about the processing capability of a medium size computer. According to this view of the brain there is more computational power in one three pound brain than in all the computers in the world.
Neurons interact by driving up the activation level of other neurons called excitation or driving down their activation level which is called inhibition. How the neurons represent information is an interesting question. There is some evidence that some neuron which respond to more complex sets of features such as faces are in a single cell. We are sure however, that it is not possible for a single neuron to encode all the concepts and shades of meaning we possess. So a single neuron firing cannot represent all the complexity of the structure of a face. This being the case how then do we solve a problem or maintain an emotion? It appears that concepts occur in large patterns of bit changes. Cognition if found in patterns of the primitive elements in computers. Similarly we are sure that human cognition is achieved through large patterns of neural activity. We know that information in the brain can be represented in terms of patterns of neural activity rather than simply as cells firing. We can indeed chart this activity. So far was have only talked about the encoding of a single activity which then quickly dissipate. Memories on the other hand are maintained by changes in the synaptic connections. So first something is encoded and understood and that causes a change in the synaptic connection which is a memory of the understood code.
Perception, Sensation and Sensory Memories
Perception is simply code. It is chemical in the case of taste, smell, and touch. It is light waves in the case of sight and sound waves in the case of hearing. As codes come together like a telegraph into a pattern to form a thought; it becomes a sensation and that series of codes is recognized by the brain. When information first enters the brain it is put into sensory memory. These memories include iconic memory for visual information and an echoic memory for auditory information Sensory memories can store a lot of information but only for a short period of time. Sensory memory is perceived by the five senses, vision, tough, olfactory (smell), auditory and taste. There is no other way to get information into the brain. So sensation is the process of one or all of you five senses coding the world and sending that code to the brain. You can make and hold a lot of code but ultimately it is sent to the brain to be understood. The sensory memory is in the body not the brain. It holds the full about of code to have a concept understood. So if you are watching a sunset, you see and code that and you hear and code that and you feel (touch) and code that and you taste and code that. Some of those codes are almost nothing and others such as vision in this case are huge. All the codes then go to the brain together to be processed and understood. Sensory memories only last long enough to be understood and then either they are dismissed as unimportant or saved in long term memory. This is the point at which we have cognition.
Why we save one memory and not another is controlled by two things. The first is due to the process of attention. The second is by what we have taught our brain is important or not important. The main two ways we teach this to the brain is through day dreaming and self-talk. This is really a form of learning which we will get to later.
Plotnik, R., Kouyoumdjian, H., (2013). Intro to Psychology, ninth ed. Belmont CA. Wadsworth.