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Neurosciences & Stroke

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About the Brain

The human brain consists of millions of nerve cells (neurons). It weighs about 3 pounds and is jello-like in consistency. It floats in fluid (cerebral spinal fluid), is covered by protective membranes (meninges), and is enclosed in the bony skull (cranial vault). It communicates with the rest of the body through nerves running through the spinal cord and the peripheral nervous system. The brain is a large consumer of oxygen, which is supplied by a complex system of blood vessels.

The brain is sometimes referred to as "the organ of behavior" as it controls almost everything we do. It controls thoughts, memory, speech, emotions, sensory information, body movement, and the function of many other organs in the body. It is also responsible for the patterns of behavior we refer to as personality. The brain has four main sections, which include: the brainstem, cerebellum, the limbic system, and the cerebral cortex.

  • Brainstem: The brainstem is the lowest part of the brain and connects the brain to the spinal cord. It is involved in regulating our level of alertness, and also controls basic bodily functions such as heart rate, breathing, body temperature, and digestion.


  • Cerebellum: The cerebellum is located at the back of the brain. It is involved with movement, coordination, and balance.


  • Limbic System: The limbic system is located above the brain stem deep inside the brain. It is involved in our emotional functioning and also plays a role in the ability to remember new information.


  • Cerebral Cortex: The cerebral cortex is the outer layer of the brain and is divided into left and right hemispheres, or halves. Each hemisphere controls movement and feeling in the opposite side of the body. The outermost inch of the cerebral cortex is composed of neuron cell bodies and is referred to as “grey matter”, because of its grey color. Below the grey matter is the “white matter”, which consists of incoming and outgoing axons that can be thought of as the arms of the neurons. These axons, or arms, start out at the neuron’s cell body, and reach out to connect with other neurons in different areas of the brain so that these different areas of the brain can communicate with one another. The cerebral cortex controls the highest levels of thinking and behavior. Each hemisphere is further divided into four lobes.


  • Frontal Lobes: The frontal lobes are involved in complex cognitive functions such as planning, organizing, initiating, monitoring and controlling behaviors or emotions. These are often referred to as “Executive Functions”. The center for speech is also located in the frontal lobe. In most people this is in the left frontal lobe.


  • Temporal Lobes: The temporal lobes control hearing and the left temporal lobe is involved in understanding language. Both temporal lobes are also involved with memory – the left temporal lobe for verbal memory and the right temporal lobe for visual memory.


  • Parietal Lobes: The parietal lobes process incoming bodily sensory information from the opposite side of the body. They are also involved in visual spatial information processing, and the left parietal lobe is involved in reading.
  • Occipital Lobes: The occipital lobes process visual information. They allow us to recognize and understand what the eyes are “seeing”.