Chapter 3: Neuroanatomy and Development

Plasticity


Plasticity means adaptive or malleable. If an area on the body is destroyed the respective brain area will start working with the area next to it. Also, experience can shape the brain areas even in adult life. Topographic mapping is when the body is represented on its respective cortical area. This is also called homunculi, which is a when a "small person" is represented on the brain areas. For example, if one of your fingers is amputated or a nerve is cut the respective brain area will eventually become active again and respond to stimulation to the finger adjacent to the amputated finger.  The cortical neurons that responded to the amputated areas may undergo denervation hypersensitivity, which means that the receptors become more sensitive or there is an increase in number of receptors. Another example of brain plasticity is in string players. String players tend to use their left hands a lot and because of this that particular brain area  grows. Within days a certain brain area can adapt itself and become active and respond to stimulation to adjacent areas. Reorganization depends on the amount of gamma-aminobutyric acid (GABA). More GABA means that the ability of the brain to reorganize itself. 

Chapter 2: Cellular Mechanisms and Cognition

Neurons

The major parts of the neuron are the soma, dendrites and axons. Dendrites receive information from other neurons and axons pass the information on. The soma is the cell body. There are different forms of neurons. They are: unipolar, bipolar, pseudounipolar and multipolar. Unipolar neurons have only one process that extends from the cell body. Bipolar neurons have two processes that extends from the cell body. Pseudounipolar neurons look like unipolar neurons but were bipolar neurons. Their dendrites and axons have merged together. Multipolar have only one axon and have many dendrites extending from the cell body.

Resting Membrane Potential

There are ion channels that allow sodium, potassium and chloride either in or out of the cell. There is a higher concentration of sodium and chloride outside than there is inside. This is opposite for potassium, there is a lower concentration outside than inside. Because of the concentration differences potassium will enter the cell while sodium and chloride are pushed out. However, the cell would be a completely different cell if there were nothing to maintain the concentration difference. The pomp helps do this. Typically, the voltage for resting potential is about -70 millivolts. Since the cell has a concentration difference in ions the voltage changes, this is called the action potential. During action potential sodium enters into the cell increasing the voltage. It seems as if it is reaching the sodium equilibrium. However, when the voltage gets too high the pump kicks in and works to lower the voltage to its normal state.

Synaptic Transmission

The important function a neuron serves is communicating with other neurons. The action potential leads to the depolarization of the neuron, which initiates an increase in calcium. This causes small vesicles to fuse with the membranes at the synapse; in turn the transmitter is released into the synaptic cleft.  The chemical interaction can lead to either hyperpolarization or depolarization. Hyperpolarization (inhibition) is very important. If the neuron would fire continually, this would produce a seizure. If the postsynaptic cell is a neuron this will lead to excitatory postsynaptic potential (EPSP). However, if the neurotransmitter has an inhibitory action this will lead to a inhibitory postsynaptic potential (IPSP). Hyperpolarization will cause the membrane potential to become negative therefore farther away from threshold. This would decrease the chances of the neuron to produce an action potential. Sometimes inhibitory synaptic inputs lead to depolarization. This is because the equilibrium potential for chloride is about -60 millivolts. The resting potential is about -70 millivolts, so opening the chloride channels would cause the membrane potential to move towards -60 milllivolts. The chloride would force the potential to remain around -60 millivolts. The threshold to create an action potential is about -40 millivolts. So, depolarization to -60 millivolts would still lead to inhibition of the neuron.

Chapter 1: A Brief History of Cognitive Neuroscience

History of Cognitive Neuroscience


In the 70's Michael Gazzaniga and George Miller were riding in the back of a taxi in New York City on their way to a dinner for those who were studying how the brain enables the mind. That is when they came up with the term cognitive neuroscience. Cognition, meaning the process of knowing or how we came to knowing something and neuroscience, which is the study of the nervous system. Essentially, cognitive neuroscience means how the brain enables the mind.


The Brain Story


Localization and topographic maps are very important ideas when studying the brain. Localization is the idea that certain areas of the brain are responsible for specific things. Topographic organization is the belief that the brain is ordered in an orderly fashion that moves from one part to another. Topographic mapping also supports the idea of localization. A study that supports the idea of localization was when Paul Broca was treating a patient with damage to the left inferior frontal lobe. The patient could understand language but he was not able to speak. Carl Wernicke treated a patient with damage to the area where the parietal and temporal lobes meet. The patient had the opposite symptoms as Broca's patient. This patient could speak but they made little sense when speaking. These findings were a huge step in the study of the brain.