Neuroscience & Behavior The Brain - Ms. G's Classroom

Neuroscience & Behavior The Brain Studying the Brain The oldest method of brain study was observation of specific brain diseases and the results of brain injuries. Today, in the lab, scientists can lesion (destroy) small clusters of brain cells, leaving the

surrounding tissue unharmed and observe changes in brain function. These clinical observations and lab experiments have enabled us to link structure with function of the brain. Phineas Gage Phineas Gage (1848) Level headed and calm railroad foreman suffered a horrific damage to his brain when an explosion hurled an iron rod through his head. o Cage survived the accident. o His behavior became

impulsive and he was unable to control his emotions or his obscene language. o An autopsy revealed a loss phineas gage Electroencephalogra ph (EEG) AN EEG is an amplified readout of the electrical activity of brain waves from neuronal impulses. By presenting a stimulus repeatedly and having a computer filter out brain activity unrelated to

the stimulus, one can identify the electrical wave known as an evoked potential that has been induced by the stimulus. Computerized Axial Tomography (CT) CAT or CT scan creates a computerized image using x-rays through various angles of the brain showing 2 dimensional slices that can be arranged to show the extent of a lesion in the brain. Positron Emission Tomography (PET) Scan

PET scans can produces color computer graphs that depend on the amount of metabolic activity in the imaged brain region When neurons are active, an automatic increase in blood flow to the active regions of the brain bring more oxygen and glucose necessary for cellular respiration. Blood flow changes are used to create brain images when radioactive tracers (tagged glucose) injected into the blood of the patient emit particles called positrons, which are then converted into signals detected by the PET scanner to produce a visual image display

of brain activity while the brain is performing a specific task Decoding a PET Scan MRI (Magnetic Resonance Imaging) Use magnetic fields and radio waves to produce computer generated images of soft tissues, including the brain. MRI scans are frequently used to study brain anatomy. ventricles

healthy brain schizophrenic brain Functional MRI FMRI (functional magnetic resonance imaging) can reveal brain structure AND function.

It shows the brain at work at higher resolution than a PET scan. Changes in the oxygen in the blood to an activefurther brain area alters processing, a After computer is magnetic qualities, detailed picture of local brain activity which is then recorded

Evolution of the Brain Triune Brain: One model of evolution with respect to the brain. o The human brain has three major divisions, overlapping layers with the most resent neural systems nearest the front and the top. o The reptilian brain, which maintains homeostasis and instinctive behaviors, roughly corresponds to the brainstem (hindbrain). o The old mammalian brain corresponds to the limbic system, including the thalamus, hypothalamus, septum, hippocampus,

amygdala, and the cingulate cortex Evolution of the Brain (contd) The new mammalian brain or neocortex (cerebral cortex) accounts for about 80% of the brain volume and associated with high functions of judgment, abstract thought, decision making, language and computing, foresight, insight, hindsight, sensation and Old Mammalian perception. brain Brainstem

The oldest part and central core of the brain, beginning where the spinal cord swells at it enters the skullis an The brainstem extension of the spinal cord and includes the medulla and the pons. The thalamus (not part of the brainstem) sits on

top of the brainstem as pictured. Brainstem (contd) The brainstem is the crossover point where most nerves to and from each side of the brain connect with the opposite side. The first swelling a the base of the brainstem is the medulla.

Center for all involuntary muscle control such as heart, arteries, digestive system, and diaphragm. Above the medulla is the pons. connects the upper and lower parts of the brain; serves as a message station between several areas of the brain. Contralat eral nature of Brainstem (contd)

Inside the brainstem (between your ears) lies the reticular formation, a finger-shaped network of neurons that extends from the spinal cord to the thalamus. Some sensory information from the spinal cord travels through the reticular formation, which filters this information and relays important information to other parts of the brain In 1949, experimentation with electrical stimulation of the reticular formation of a sleeping cat produced immediate arousal. Conversely, when reticular formation was Thalamus

The thalamus sits on top of the brainstem. It is a pair of egg shaped structures that function as the brains switchboard. The thalamus receives messages from all the senses except for smell and routes them to the brains regions that deal with seeing, hearing, tasting, and touching. The thalamus also receives some of the cortexs interpretations or replies and directs these

Cerebellum Extends from the rear of the brainstem, ballshaped, two halves that are wrinkled (cross section looks like a cauliflower or tree) Coordinates voluntary movement and balance Enables nonverbal learning and memory Recent studies indicate that the cerebellum also helps us to judge time, modulate our emotions, and discriminate sounds and texture.

These older brain functions all occur without any conscious effort; we are aware of the results of our brains efforts but not of how the brain constructs these results. Limbic System Doughnut shaped, between the cerebral hemispheres and the brainstem. Made up of the: Hippocampus: processing of conscious memories. People who lose their hippocampus to injury or surgery lose their ability to form new

memories of facts or events. Amygdala: 2 lima bean shaped clusters that influence fear & aggression including the perception of these emotions and the processing of emotional memories Hypothalamus: lies below the thalamus, contain neural clusters of cells that direct important maintenance activities such as thirst, hunger, sex drive, & temperature to help maintain internal amygdala & teen homeostasis (steady internal state) Diagram of Limbic System Limbic System

(contd) Nucleus accumbens Located in front of the hypothalamus Along with the hypothalamus, appear to be involved in our reward centers; mediated by dopamine. some researchers believe that addictive disorders such as alcohol or drug dependence or binge eating may be related to malfunctions in natural brain systems for pleasure & well-being. Reward Deficiency Syndrome: people who are genetically pleasure disposed to this centers brai syndrome, may crave

n whatever Cerebrum Cerebrum is the largest and most prominent part of the human brain and constitutes 4/5 of its weight. It is split longitudinally into two large, prominent left & right hemispheres separated by a deep median fissure called cerebral fissure.

Corpus callosum: large band of neural fibers connecting the two brain hemispheres that carries messages between them. Each hemisphere is further divided into the frontal, parietal, temporal, and occipital lobes divided by prominent fissures (folds) Four Lobes of the Cerebrum Functions of the Four Lobes Lobes of the Cerebrum

Frontal Lobes: lie just behind the forehead, involved in speaking, muscle movements, making plans, and judgments. Parietal Lobes: lie at the top of the head behind the frontal lobes; involved with sensory input for touch and body position, Occipital Lobes: lie to the back of the head; includes visual areas, which receive visual information from the opposite visual field Temporal Lobes: lie roughly above the ears; includes the auditory areas, each of which receives auditory information primarily from the opposite ear.

Cerebral Cortex The Cerebral Cortex is the intricate covering of interconnected neural cells, that form a thin surface layer on your cerebral hemispheres. Contains some 20-23 billion nerve cells supported by nine times as many glial cells

that guide neural connections, provide nutrients, mop up ions and neurotransmitters. The cerebral cortex is the bodys ultimate control and information-processing center. Much of the neural activities of the cerebrum Cerebral Cortex (contd) The outer surface is highly convoluted, increasing the surface area of the cerebral

cortex. The ridges of these convolutions are called gyri and depressions between them as sulci. Each region is responsible for a particular function. According to the function or activity, these regions can be divided into three general categories: motor, sensory, and associative. Differences between Cerebrum and Cortex Cerebral cortex is a part of the cerebrum. Cerebrum is the largest and most prominent

part of the brain whereas cerebral cortex is the outer layer of the cerebrum. Cerebrum has both gray and white matter while the gray part of it is considered as the cerebral cortex. Human cerebral cortex is made up of approximately 10 billion nerve cell bodies and their dendrites whereas the cerebrum Functions of the Cortex

Motor Cortex: the area at the rear of the frontal lobes that controls voluntary movement Contralateral function: when tissue of the motor cortex is stimulated on the left hemisphere, the right body part responds (same for the right motor cortex) In the motor cortex, the brain devotes more tissue area to sensitive body parts

and to areas requiring Functions of the Cortex (contd) Sensory Cortex: the area in the front of the parietal lobes that registers and processes body touch and movement sensations. The more sensitive a body region, the larger the area of the sensory cortex devoted to it. Visual Cortex: receives visual

input from the retina. Auditory Cortex: receives input from the ear on the opposite side of the brain. The brain devotes more tissue to sensitive areas & areas requiring precise control so, for example, the fingers have greater representation in the somatosensory and motor Brain Homuculus (little man) Sensory & Motor Homuculi Brain-Computer Interface (BCI)

BCI is a collaboration between a brain and a device that enables direct communications pathway between the brain and the object to be controlled. Cognitive Neural Prosthetics: BCI for people who

BCI Association Areas Association areas are parts of the cerebral cortex NOT involved in primary motor or sensory functions. These areas are involved in higher metal

functions such as learning, remembering, thinking and speaking. Since these areas are so vital to higher order thinking, the saying that we use only 10% of our brains is completely false. Association areas are found in all four lobes In the frontal lobes, these areas play and executive role in judgment, planning, and the processing of new memories. Brain Plasticity Plasticity: the brains capacity for modification, as evident in brain reorganization following damage, particularly in children.

If one hemisphere is damaged early in life, the other hemisphere will pick up many of the damaged spheres functions. Neurogenesis: the growth of new neurons Plasticity decreases as a person ages, although nearby neurons may partially compensate for damaged ones after a stroke or other brain injury. brain plasticity The Divided Brain

Lateralization of the brain: Clinical observations more than a century ago, found that the left hemisphere is critical for speaking, writing, arithmetic reasoning, and understanding. Corpus Callosum: a large band of neural fibers connecting the two brain hemispheres that carries messages between them. Split Brain: a condition in which the two hemispheres of the brain are isolated by cutting the corpus callosum and other

Studying the Split Brain Information from the left half of your field of vision goes to your right hemisphere and information from the right half of your field of vision goes to your left hemisphere. The data received by either hemisphere is

quickly transmitted to the other side via the corpus callosum. In a split brain patient Of Two Minds split brain Right/Left Differences in Intact Brains Left brain thinking is verbal and analytical. Right brain is non-verbal and intuitive, using

pictures rather than words (visual perception and emotional recognition) Together, the left and right hemisphere make unique contributions to the integrated functioning of the brain.

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