Chapter 3 Notes-Brain and Behavior
Chapter 3 Notes-Brain and Behavior
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October 7 2013 PSYCH 101 Tori Timmons Chapter 3 Notes 39 Neuroscience and Behavior o Prolonged crystal meth use alters the normal functioning of some of the chemicals in someone s brain distorting their perception of reality o A rare disorder called prosopagnosia is the inability to recognize familiar faces and is a result of brain damage to part of the right side of the brain o This chapter will teach us how the brain works what happens when it doesn t and how both states of affairs determine behavior o Neurons The Origin of Behavior There are approximately 100 billion cells in your brain that perform a variety of tasks to allow you to function as a human being These are called neurons Like cells in all organs of the body neurons have a cell body Function such as protein synthesis energy production and metabolism take place here The cell body also contains the nucleus which houses chromosomes that contain your DNA Neurons have 2 types of specialized extensions of the cell membrane that allow them to communicate dendrites and axons Dendrites receive information from other neurons and relay it to the cell body The axon transmits information to other neurons muscles or glands Sometimes axons can be very long October 7 2013 PSYCH 101 Tori Timmons In many neurons the axon is covered by a myelin sheath which is composed of glial cells An axon insulated with myelin can more efficiently transmit signals to other neurons organs or muscles With some demyelinating diseases the myelin sheath deteriorates slowing the transmission of information from one neuron to another This causes problems like loss of feeling in limbs partial blindness and difficulties in coordinated movement and cognition Neurons look like the form a continuously connected lattice but there is a small gap between the axon of one neuron and the dendrite or cell body of another and this gap is part of the synapse The transmission of information across the synapse is fundamental to communication between neurons a process that allows us to think feel and behave There are 3 major types of neurons each performing a distinct function 39 Sensory neurons receive information from the external world and convey this information to the brain via the spinal cord These neurons have specialized endings on their dendrites that receive signals for light sound touch taste and smell 39 Motor neurons carry signals from the spinal cord to the muscles to produce movement These neurons often have long axons that can stretch to the muscles at our extremities October 7 2013 PSYCH 101 Tori Timmons The nervous system is composed of interneurons which connect sensory neurons motor neurons and other interneurons Some interneurons carry information from sensory neurons into the nervous system and others carry information from the nervous system to motor neurons and other perform a variety of other information processing functions o Information Processing in Neurons First information has to travel inside the neuron from the dendrite to the cell body to the axons in the form of an electrical signal The signal has to be passed from one neuron across the synapse to another neuron Electric Signaling Conducting Information Within A Neuron The neuron s cell membrane is porous allowing small ions to flow in and out of the cell The flow of the molecules across the cell membrane enhances the transmission of information in the nervous system 39 The Resting Potential The Origin of the Neuron s Electrical Properties o Neurons have a natural electric charge called the resting potential The resting potential arises from the difference in concentrations of the ions inside and outside of the neuron s cell membrane o In the resting state there are various positively and negatively charged ions on both sides of the membrane October 7 2013 PSYCH 101 Tori Timmons but there is usually a higher concentration of positively charged potassium ions K inside the neuron s cell membrane than outside it The concentration of K inside and outside an axon is controlled by channels in the axon membrane that allow molecules to flow in and out of the neuron As K molecules flow out of the neuron through open channels this reduces the proportion of positively charge ions inside the neurons leaving the inside of the neuron with a resting potential of about 70 millivolts relative to the outside The resting potential creates the environment for a possible electrical impulse The Action Potential Sending Signals Across The Neuron o The neuron maintains its resting potential most of the time In the 193039s biologists Hodgkin and Huxley noticed that they could stimulate the axon with a brief electric shock which resulted in the conduction of a large electric impulse down the length of the axon This electric impulse is called an action potential The action potential occurs only when the electric shock reaches a certain level or threshold The action potential is all or nothing October 7 2013 PSYCH 101 Tori Timmons Electric stimulation below the threshold fails to produce an action potential whereas electric simulation at or above the threshold always produces an action potential The action potential occurs when there is a change in the state of the axon s membrane channels During an action potential the K channels briefly shut down and other channels that allow the flow of Na are opened The positively charged Na ions flow inside increasing the positive charge inside the axon relative to that outside This flow of Na into the axon pushes the electric charge inside the neuron from 70 millivolts to 40 millivolts The electrical current moves down the axon like a kind of chain reaction as an action potential is generated at the beginning of the axon it spreads a short distance which generates an action potential at another nearby location and so on Myelin does not cover the entire axon rather it clumps around the axon with little break points between clumps These breakpoints are called the nodes of Ranvier When an electric current passes down the length of a myelinated axon the charge seems to jump from node to node rather than having to traverse the entire axon This helps the sped of the flow of information down the axon October 7 2013 PSYCH 101 Tori Timmons o After the action potential reaches its maximum the membrane channels return to their original state This leaves a lot of extra Na ions inside the axon and a lot of extra K ions outside the axon o When the ions are imbalanced the neuron cannot initiate another action potential and is said to be in a refractory period The imbalance in ions is eventually reversed by an active chemical pump in the cell membrane that moves the Na out and the K in Chemical Signaling Transmission Between Neurons The electric charge of the action potential takes a form that can cross the relatively small synaptic gap Axons usually end in terminal buttons which are filled with tiny vesicles or bags that contain neurotransmitters The dendrites of the receiving neuron contain receptors The action potential travels down the length of the axon of the sending neuron or the presynaptic neuron Once the action potential reaches the terminal buttons of the presynaptic neuron it stimulates the release of neurotransmitters from vesicles into the synapse These neurotransmitters float across the synapse and bind to receptor sites on a nearby dendrite of the receiving neuron or postsynaptic neuron A new electric potential is initiated in that neuron which in turn may generate an action potential of its own This process called October 7 2013 PSYCH 101 Tori Timmons synaptic transmission allows neurons to communicate with one anothen 39 Something must make the neurotransmitters stop acting on neurons otherwise there would be no end to the signals they send o First neurotransmitters can be reabsorbed by the terminal buttons of the presynaptic neuron a process called reuptake o Second neurotransmitters can be broken down into their component molecules a process called deactivation o Third neurotransmitters can bind to receptor sites called autoreceptors on the presynaptic neuron Autoreceptors detect how much of a neurotransmitter has been released into a synapse and signal the neuron to stop releasing neurotransmitters Types and Functions of Neurotransmitters Today we know that some 60 chemicals play a role in transmitting information through the brain and body Neurotransmitters and receptor sites act like a lock and key system Only some neurotransmitters bind to specific receptor sites on a dendrite 39 Most neurotransmitters fit into a few major classes o Acetylcholine is a neurotransmitter involved in a number of functions including voluntary motor control October 7 2013 PSYCH 101 Tori Timmons Acetylcholine is found in neurons of the brain and in the synapses where axons connect to muscles and body organs such as the heart Acetylcholine also contributes to the regulation of attention learning sleeping dreaming and memory Dopamine is a neurotransmitter that regulates motor behavior motivation pleasure and emotional arousal Because of its association with the processing of motivation and pleasure dopamine plays a role in drug addiction Glutamate is a major excitatory neurotransmitter in the brain meaning that it enhances the transmission of information between neurons Too much glutamate can cause neurons to become overactive causing seizures 2 related neurotransmitters Norepinephrine Serotonin influence mood and arousal Norepinephrine is particularly involved in vigilance or a heightened awareness of dangers in the environment Serotonin is involved in the regulation of sleep and wakefulness eating and aggressive behavior Endorphins are chemicals that act within the pain pathways and emotion centers of the brain to help dull the experience of pain and elevate moods October 7 2013 PSYCH 101 Tori Timmons Each of the neurotransmitters affects thoughts feelings and behavior in different ways so normal functioning involves a delicate balance of each People who smoke drink alcohol or take drugs legal or not are altering the balance of neurotransmitters in their brains How Drugs Mimic Neurotransmitters Many drugs that affect the nervous system operate by increasing interfering with or mimicking the manufacture or function of neurotransmitters Agonists are drugs that increase the action of a neurotransmitter Antagonists are drugs that block the function of a neurotransmitter Some drugs have a chemical structure so similar to a neurotransmitter that the drug is able to bind to receptors that are keyed to that neurotransmitter For example morphine is a drug that binds to endorphin receptors in the brain The result is a calming and pleasurable effect similar to that produced by the endorphins themselves Other drugs alter a step in the production or release of the neurotransmitter For example a drug called L dopa has been developed to treat Parkinson39s disease a movement disorder characterized by tremors and difficulty initiating movement and caused by the loss of neurons that use the neurotransmitter dopamine October 7 2013 PSYCH 101 Tori Timmons Ingesting L dopa will spur the surviving neurons to produce more dopamine The combination of methamphetamine s agonist and antagonist effects alters the functions of neurotransmitters that help us perceive and interpret visual images 39 Legal drugs such as caffeine tobacco and alcohol also work by altering the actions of neurotransmitters o The Organization of the Nervous System Neurons work by forming circuits and pathways in the brain which in turn influence circuits and pathways in other areas of the body The nervous system is an interacting network or neurons that conveys electrochemical information throughout the body There are 2 major divisions of the nervous system the central nervous system and the peripheral nervous system The central nervous system is composed of the brain and spinal cord It receives sensory information from the external world processes and coordinates this information and sends commands to the skeletal and muscular systems for action The peripheral nervous system connects the central nervous system to the body s organs and muscles The Peripheral Nervous System The peripheral nervous system is composed of 2 major subdivisions the somatic nervous system and the autonomic nervous system October 7 2013 PSYCH 101 Tori Timmons Humans have conscious control over the somatic nervous system and use it to perceive think and coordinate their behaviors In contrast the autonomic nervous system works on its own to regulate bodily systems largely outside of conscious control The ANS has 2 major subdivisions the sympathetic nervous system and the parasympathetic nervous system The sympathetic nervous system is a set of nerves that prepares the body for action in threatening situations the parasympathetic nervous system helps the body return to a normal resting state For example imagine that you are walking alone late at night and frightened by footsteps behind you in a dark alley Your sympathetic nervous system kicks into action at this point it dilates your pupils to let in more light increases your heart rate and respiration to pump more oxygen to muscles diverts blood flow to your brain and muscles and activates sweat glands to cool your body Once you are safe your parasympathetic nervous system kicks in to reverse the effects of the sympathetic nervous system and return your body to its normal state Thus the parasympathetic nervous system constricts your pupils slows your heart rate and respiration diverts blood flow to your digestive system and decreases activity in your sweat glands The Central Nervous System October 7 2013 PSYCH 101 Tori Timmons It has 2 elements the brain and the spinal cord But these 2 elements are responsible for most of what we do as humans The brain supports the most complex perceptual motor emotional and cognitive functions of the nervous system The spinal cord branches down from the brain to relay commands to the body Connections between the sensory inputs and motor neurons in the spinal cord mediate spinal reflexes If you touch a hot stove the sensory neurons that register pain send inputs directly into the spinal cord More elaborate tasks require the collaboration of the spinal cord and the brain The peripheral nervous system communicates with the central nervous system through nerves that conduct sensory information into the brain carry commands out of the brain or both The brain sends commands for voluntary movement through the spinal cord to motor neurons whose axons project out to skeletal muscles and send the message to contract Damage to the spinal cord severs the connection form the brain to the sensory and motor neurons that are essential to sensory perception and movement Researchers are making progress in understanding the nature of spinal cord injuries and how to treat them by focusing on how the brain changes in response to injury o Structure of the Brain October 7 2013 PSYCH 101 Tori Timmons Right now your neurons and glial cells are busy humming away giving you potentially brilliant ideas consciousness and feelings But which neurons in which parts of the brain control which functions To answer that question neuroscientists first had to find a way of describing the brain Although each side of the brain is roughly analogous 1 half of the brain specializes in some tasks that the other half doesn t None of these structures of areas in the brain can act alone they are all part of 1 big interacting interdependent whole The Hindbrain 39 The spinal cord is continuous with the hindbrain The hindbrain controls the most basic functions of life respiration alertness and motor skills 39 There are 3 anatomical structures that make up the hindbrain the medulla the cerebellum and the pons o The medulla is an extension of the spinal cord into the skull that coordinates the heart rate circulation and respiration Inside the medulla is a small cluster of neurons called the reticular formation which regulates sleep wakefulness and levels of arousal The reticular formation maintains a delicate balance between alertness and unconsciousness in humans o Behind the medulla is the cerebellum a large structure of the hindbrain that controls fine motor skills It contributes to the fine tuning of behavior smoothing October 7 2013 PSYCH 101 Tori Timmons our actions to allow their graceful execution rather than imitating the actions o The last major area of the hindbrain is the pons a structure that relays information from the cerebellum to the rest of the brain Although the detailed functions of the pons remain poorly understood it essentially acts as a relay station or bridge between the cerebellum and other structures in the brain The Midbrain Sitting on top of the hindbrain is the midbrain which is relatively small in humans The midbrain contains 2 main structures the tectum and the tegmentum These structures help orient an organism in the environment and guide movement toward or away from stimuli The midbrain may be relatively small but it is important The Forebrain The forebrain is the highest level of the brain literally and figuratively and controls complex cognitive emotional sensory and motor functions The forebrain itself is divided into 2 main sections the cerebral cortex and the subcortical structures Subcortical Structures o The subcortical structures are areas of the forebrain housed under the cerebral cortex near the very center of October 7 2013 PSYCH 101 Tori Timmons the brain The subcortical structures are nestled deep inside the brain where they are quite protected It includes the thalamus hypothalamus pituitary gland hippocampus amygdala and basal ganglia Each of these subcortical structures plays an important role in relaying information throughout the brain as well as performing specific tasks that allow us to think feel and behave as humans The Thamamus relays filters information from the senses and transmits the information to the cerebral cortex It receives input from all the major senses except smell which has direct connections to the cerebral cortex It also acts as a kind of computer server in a networked system taking in multiple inputs and relaying them to a variety of locations The thalamus actively filters sensory information giving more weight to some inputs and less weight to others It also closes the pathways of incoming sensations during sleep providing a valuable function by not allowing information to pass to the rest of the brain The Hypothalamus is right below the thalamus The hypothalamus regulates body temperature hunger thirst and sexual behavior October 7 2013 PSYCH 101 Tori Timmons The Pituitary Gland is below the hypothalamus It is the master gland of the body s hormone producing system which releases hormones that direct the functions of many other glands in the body The hypothalamus sends hormonal signals to the pituitary gland which in turn sends hormonal signals to other glands to control stress digestive activities and reproductive process The Hippocampus is critical for creating new memories and integrating them into a network of knowledge so that they can be stored indefinitely in other parts of the cerebral cortex Patients with damage to the hippocampus can acquire new information and keep it in awareness for a few seconds but as soon as they are distracted they forget the information and the experience that produced it The Amygdala is located at the tip of each horn of the hippocampus The amygdala plays a central role in many emotional processes particularly the formation of emotion memories When we are in emotionally arousing situations the amygdala stimulate the hippocampus to remember many details surrounding the situation The Basal Ganglia is located near the thalamus and hypothalamus It is a set of subcortical October 7 2013 PSYCH 101 Tori Timmons structures that directs intentional movements The basal ganglia receive input form the cerebral cortex and send outputs to the motor centers in the brain stem One part of the basal ganglia the striatum is involved in the control of posture and movement The Cerebral Cortex o The cerebral cortex is the outermost layer of the brain visible to the naked eye and divided into 2 hemispheres o The highest level of the brain the cortex is responsible for the most complex aspects of perception emotion movement and thought o The cortex with its wrinkles and folds holds a lot of brainpower in a relatively small package that fits comfortably inside the human skull o The functions of the cerebral cortex can be understood at 3 levels the separation of the cortex into 2 hemispheres the functions of each hemisphere and the role of specific cortical areas o Organization Across Hemispheres The first level of organization divides the cortex into the left and right hemispheres The 2 hemispheres are more or less symmetrical in their appearance and to some extent in their functions However each hemisphere controls the October 7 2013 PSYCH 101 Tori Timmons functions of the opposite side of the body This is called contralateral control The cerebral hemispheres are connected to each other by a bundle of axons that make communication between parallel areas of the cortex in each half possible The largest of these bundles is the corpus callosum which connects large areas of the cerebral cortex on each side of the brain and supports communication of information across the hemispheres That means information can be received in the right hemisphere and can pass across the corpus callosum to the left hemisphere o Organization Within Hemispheres The second level of organization in the cerebral cortex distinguishes the functions of the different regions within each hemisphere of the brain Each hemisphere of the cerebral cortex is divided into four lobes 39 The occipital lobe located at the back of the cerebral cortex process visual information Sensory receptors in the eyes send information to the thalamus which in turn sends information to the primary areas of the occipital lobe where simple features of the stimulus are extracted October 7 2013 PSYCH 101 Tori Timmons such as the location and orientation of an object39s edges These features are then processed further in the occipital cortex leading to comprehension of what s being seen The parietal lobe located in the front of the occipital lobe carries out functions that include processing information about touch The parietal lobe contains the somatosensory cortex a strip of brain tissue running from the top of the brain down to the sides Each part of the somatosensory cortex maps onto a particular part of the body If a body area is more sensitive a larger part of the somatosensory cortex is devoted to it Directly in front of the somatosensory cortex in the frontal lobe is a parallel strip of brain tissue called the motor cortex The motor cortex initiates voluntary movements and sends messages to the basal ganglia cerebellum and spinal cord The motor and somatosensory cortices then are like sending and receiving areas of the cerebral cortex taking in information and sending out commands October 7 2013 PSYCH 101 Tori Timmons The temporal lobe located on the lower side of each hemisphere is responsible for hearing and language The primary auditory cortex in the temporal lobe is analogous to the somatosensory cortex in the parietal lobe and the primary visual areas of the occipital lobe it receives sensory information from the ears based on the frequencies of sounds Secondary areas of the temporal lobe then process the information into meaningful units such as speech and words The temporal lobe also houses the visual association areas which interpret the meaning of visual stimuli and help us recognize common objects in the environment The frontal lobe which sits behind the forehead has specialized areas for movement abstract thinking planning memory and judgment In short the frontal cortex allows us to do the kind of thinking imagining planning and anticipating that sets humans apart from most other species o Organization Within Specific Lobes October 7 2013 PSYCH 101 Tori Timmons The third level of organization in the cerebral cortex involves the representation of information within specific lobes in the cortex There is a hierarchy of processing stages from primary areas that handle fine details of information all the way up to association areas which are composed of neurons that help provide sense and meaning to information registered in the cortex Brain Plasticity Sensory cortices are not fixed They can adapt to changes in sensory inputs a quality researchers call plasticity The brain is plastic functions that were assigned to certain areas of the brain may be capable of being reassigned to other areas of the brain to accommodate changing input from the environment This suggests that sensory inputs compete for representation in each cortical area Plasticity doesn t occur only to compensate for missing digits or limbs however An extraordinary amount of stimulation of one finger can result in that finger taking over the representation of the part of the cortex that usually represents other adjacent fingers Recent research indicates greater plasticity within the motor cortex of professional musicians compared with non musicians perhaps reflecting an increase in the number of motor synapses October 7 2013 PSYCH 101 Tori Timmons as a result of extended practice Similar findings have been obtained with quilters and taxi drivers Plasticity is also related to a question you might not expect to find in a psych textbook how much exercise have you been getting lately Physical exercise can increase the number of synapses and even promote the development of new neurons in the hippocampus There are many beneficial effects of cardiovascular exercise on aspects of brain function and cognitive performance It should be clear by now that the plasticity of the brain is not just an interesting theoretical idea it has potentially important applications to everyday life o The Evolution of Nervous Systems Far from being a single elegant machine the human brain is instead a system comprised of many distinct components that have been added at different times during the course of evolution The human species has retained what worked best in earlier versions of the brain then added bits and pieces to get us to our present state through evolution Evolutionary Development of the Central Nervous System The central nervous system evolved from the very simple one found in simple animals to the elaborate nervous system in humans today October 7 2013 PSYCH 101 Tori Timmons During the course of evolution a major split in the organization of the nervous system occurred between invertebrate animals and vertebrate animals In all vertebrates the central nervous system is organized into a hierarchy with lower levels executing simpler functions and higher levels performing more complex ones The forebrain undergoes further evolutionary advances in vertebrates Mammals have a highly developed cerebral cortex which develops multiple areas that serve a broad range of higher mental functions This forebrain development has reached its peak so far in humans This refinement of the forebrain allows for some remarkable uniquely human abilities self awareness sophisticated language use social interaction abstract reasoning imagining and empathy among others Genes and the Environment The phrase nature vs nurture suggests that either genetics nature or the environment nurture plays a major role in producing particular behaviors personality traits psychological disorders or pretty much any other thing that a human does The emerging picture from current research is that both nature and nurture play a role in directing behavior and the focus has shifted to examining the relative contributions of each influence rather than the absolute contributions of either influence alone October 7 2013 PSYCH 101 Tori Timmons A gene is the unit of hereditary transmission Genes are sections on a strand of DNA and are organized into large threads called chromosomes Chromosomes come in pairs and humans have 23 pairs each You inherit one member of each pair rom your father and one from your mother The probability of sharing genes is called degree of relatedness Many researchers have tried to determine the relative influence of genetics on behavior In short genetics can contribute to the development likelihood or onset of a variety of traits But a more complete picture of genetic influences on behavior must always take the environmental context into consideration o Investigating the Brain Anatomists can dissect a human brain and identify its structures but they cannot determine which structures play a role in producing which behaviors by dissecting a nonliving brain Scientists use a variety of methods to understand how the brain affects behavior Let s consider 3 of the main ones Learning About Brain Organization by Studying the Damaged Brain Betty is a 75yearold woman who could not recognize her own husband She had suffered a stroke caused by a blood clot that deprived her brain of oxygen and caused the death of neurons in the afflicted area October 7 2013 PSYCH 101 Tori Timmons Betty39s stroke affected part of the association area in her temporal lobe where complex visual objects are identified Betty39s occipital lobe the main area where visual processing takes place was unaffected so she could see her husband and sons but because of the damage to her temporal lobe she could not recognize them Much research in neuroscience correlates the loss of specific perceptual motor emotional or cognitive functions with specific areas of brain damage The better understand the normal operation of a process it is instructive to understand what happens when that process fails The Emotional Functions of the Frontal Lobes o Psychology s first glimpse at some functions of the frontal lobes came from an accident that happened to Phineas Gage Phineas was a 25yearold railroad worker In 1848 he was packing an explosive charge into a crevice in a rock when the powder exploded driving a 3 foot 13 pound iron rod through his head at high speed The rod entered through his lower left jaw and exited through the middle top of his head He lived but his personality underwent a significant change o Before the accident Phineas had been mild mannered quiet conscientious and a hard worker After the accident however he became irritable irresponsible indecisive and given to profanity October 7 2013 PSYCH 101 Tori Timmons o His case study was the first to allow researchers to investigate the hypothesis that the frontal lobe is involved in emotion regulation planning and decision making Furthermore because the connections between the frontal lobe and the subcortical structures were affected scientists were able to better understand how the amygdala hippocampus and related brain structures interacted with the cerebral cortex The Distinct Roles of the Left and Right Hemispheres o Sometimes though disorders can threaten the ability of the brain to function and the only way to stop them is with radical methods This is sometimes the case with patients who suffer from sever intractable epilepsy Seizures that begin in one hemispheres cross the corpus callosum to the opposite hemisphere and start a feedback loop To alleviate the severity of the seizures surgeons can perform a split brain procedure to sever the corpus callosum but this produces some unusual if not unpredictable behaviors Roger Sperry designed several experiments that investigated the behaviors of human split brain patients and in the process revealed a great deal about the independent functions of the left and right hemispheres October 7 2013 PSYCH 101 Tori Timmons o The hemispheres themselves are specialized for different kinds of tasks o These split brain studies reveal that the two hemispheres perform different functions and can work together seamlessly as long as the corpus callosum is intact Without a way to transmit information from one hemisphere to the other information gets stuck in the hemisphere it initially entered Listening to the Brain Single Neurons and Global Activity A second approach to studying the link between brain structures and behavior involves recording the pattern of electrical activity of neurons An electroencephalograph EEG is a device used to record electrical activity in the brain Typically electrodes are place on the outside of the head and even though the source of electrical activity in synapses and action potentials is far removed from these wires the electric signals can be amplified several thousand ties by the EEG Using this technique researchers can determine the amount of brain activity during different states of consciousness EEG recordings allow researchers to make these fundamental discoveries about the nature of sleep and wakefulness The EEG can also be used to examine the brain39s electrical activity when awake individuals engage in a variety of psychological functions such as perceiving learning and remembering October 7 2013 PSYCH 101 Tori Timmons David Hubel and Torsten Wiesel used a technique that inserted electrodes into the occipital lobes of anesthetized cats and observed the patterns of action potentials of individual neurons They discovered that neurons in the primary visual cortex are activated whenever a contrast between light and dark occurs in part of the visual field Since then many studies have shown that neurons in the primary visual cortex represent particular features of visual stimuli such as contrast shape and colour These neurons in the visual cortex are known as feature detectors because they selectively respond to certain aspects of a visual image The discovery of this specialized function for neurons was a huge leap forward in our understanding of how the visual cortex works Brain Imaging From Visualizing Structure to Watching the Brain in Action EEG readouts give an overall picture of a person s level of consciousness and single cell recordings shed light on the actions of particular clumps of neurons The aspiration of neuroscience however has been to see the brain in operation while behavior is being enacted This goal has been steadily achieved thanks to a wide range of neuroimaging techniques that use advanced technology to create images of the living healthy brain October 7 2013 PSYCH 101 Tori Timmons Structural brain imaging provides information about the basic structure of the brain and allows clinicians or researchers to see abnormalities in brain structure Functional brain imaging in contrast provides information about the activity of the brain when people perform various kinds of cognitive or motor tasks One structural neuroimaging technique is the computerized axial tomography CT scan In a CT scan a scanner rotates a device around a person s head and takes a series of x ray photographs from different angles Computer programs then combine these images to provide views from any angle CT scans show different densities of tissue in the brain Another technique magnetic resonance imaging MRI involves applying brief but powerful magnetic pulses to the head and recording how the pulses are absorbed throughout the brain For very short periods these magnetic pulses cause molecules in the brain tissue to twist slightly and then relax which releases a small amount of energy Differently charged molecules respond differently to the magnetic pulses so the energy signals reveal brain structures with different molecular compositions CT and MRI scans give psychologists a clearer picture of the structure of the brain and can help localize brain damage but they reveal nothing about the functions of the brain 2 newer functional brain imaging techniques show researchers much more than just the structure of the brain by allowing us to October 7 2013 PSYCH 101 Tori Timmons actually watch the brain in action These techniques rely on the fact that activated brain areas demand more energy for their neurons to work In positron emission tomography PET a harmless radioactive substance is injected into a person39s bloodstream Then the brain is scanned by the radiation detectors as the person performs perceptual or cognitive tasks such as reading or speaking Areas of the brain that are activated during these tasks demand more energy and greater blood flow resulting in a higher amount of radioactivity in that region In functional magnetic resonance imaging fMRI magnetic pulses cause the twisting of hemoglobin molecules Hemoglobin is the molecule in the blood that carries oxygen to our tissues including the brain When active neurons demand more energy and blood flow oxygenated hemoglobin concentrates in the active areas fMR detects the oxygenated hemoglobin and provides a picture of the level of activation in each brain area fMR has a couple of advantages over PET First fMR does not require any exposure to a radioactive substance Second fMR can localize changes in brain activity across briefer periods than PET which makes it more useful for analyzing psychological processes that occur extremely quickly such as reading a word or recognizing a face PET and fMRI provide remarkable insights into the types of information processing that take place in specific areas of the brain For example when people look at faces fMR reveals October 7 2013 PSYCH 101 Tori Timmons strong activity in a region located near the border of the temporal and occipital lobes called the fusiform gyrus Although the human brain still holds many mysteries researchers are developing increasingly sophisticated ways of unraveling them KEY TERMS Neurons Cells in the nervous system that communicate with one another to perform information processing tasks Cell Body The part of a neuron that coordinates information processing tasks and keeps the cell alive Dendrites The part of a neuron that receives information from other neurons and relays it to the cell body Axon The part of a neuron that transmits information to other neurons muscles or glands Myelin Sheath An insulating layer of fatty material Glial Cells Support cells found in the nervous system Synapse The junction or region between the axon of one neuron and the dendrites or cell body of another Sensory Neurons Neurons that receive information from the external world and convey this information to the brain via the spinal cord Motor Neurons Neurons that carry signals from the spinal cord to the muscles to produce movement Interneurons Neurons that connect sensory neurons motor neurons or other interneurons Resting Potential The difference in electric charge between the inside and outside of a neuron s cell membrane October 7 2013 PSYCH 101 Tori Timmons Action Potential An electric signal that is conducted along a neuron s axon to a synapse Refractory Period The time following an action potential during which a new action potential cannot be initiated Terminal Buttons Knoblike structures that branch out from an axon Neurotransmitters Chemicals that transmit information across the synapse to a receiving neuron s dendrites Receptors Parts of the cell membrane that receive the neurotransmitter and initiate or prevent a new electric signal Agonists Drugs that increase the action of a neurotransmitter Antagonists Drugs that block the function of a neurotransmitter Nervous System An interacting network or neurons that conveys electrochemical information throughout the body Central Nervous System The part of the nervous system that is composed of the brain CNS and spinal cord Peripheral Nervous The part of the nervous system that connects the central System PNS nervous system to the body s organs and muscles Somatic Nervous A set of nerves that conveys information into and out of the System central nervous system Autonomic Nervous A set of nerves that carries involuntary and automatic System ANS commands that control blood vessels body organs and glands Sympathetic Nervous A set of nerves that prepares the body for action in threatening System situations Parasympathetic A set of nerves that helps the body return to a normal resting Nervous System state Spinal Reflexes Simple pathways in the nervous system that rapidly generate muscle contractions Hindbrain An area of the brain that coordinates information coming into and out of the spinal cord October 7 2013 PSYCH 101 Medulla An extension of the spinal cord into the skull that coordinates heart rate circulation and respiration Reticular Formation A brain structure that regulates sleep wakefulness and levels of arousal Cerebellum A large structure of the hindbrain that controls fine motor skills Pons A brain structure that relays information from the cerebellum to the rest of the brain Subcortical Structures Areas of the forebrain housed under the cerebral cortex near the very center of the brain Thalamus A subcortical structure that relays and filters information from the senses and transmits the information to the cerebral cortex Hypothalamus A subcortical structure that regulates body temperature hunger thirst and sexual behavior Pituitary Gland The master gland of the body s hormone producing system which releases hormones that direct the functions of many other glands in the body Hippocampus A structure critical for creating new memories and integrating them into a network of knowledge so that they can be stored indefinitely in other parts of the cerebral cortex Amygdala A part of the limbic system that plays a central role in many emotional processes particularly in the formation of emotional memories Basal Ganglia A set of subcortical structures that directs intentional movements Cerebral Cortex The outermost layer of the brain divided into two hemispheres Tori Timmons October 7 2013 PSYCH 101 Tori Timmons Corpus Callosum A thick band of nerve fibers that connects large areas of the cerebral cortex on each side of the brain and supports communication of information across the hemispheres Occipital Lobe A region of the cerebral cortex that processes visual information Parietal Lobe A region of the cerebral cortex whose functions include processing information about touch Temporal Lobe A region of the cerebral cortex responsible for hearing and language Frontal Lobe A region of the cerebral cortex that has specialized areas for movement abstract thinking planning memory and judgment Association Areas Areas of the cerebral cortex that are composed of neurons that help provide sense and meaning to information registered in the cortex Gene The unit of hereditary transmission Chromosomes Strands of DNA wound around each other in a double helix configuration