The Biology of the Mind - Psych Event for Every Bio Event • In the most basic sense, every idea, mood, memory, and behavior, that an individual has ever experienced is a biological phenomenon. • The theory that linked our mental abilities to bumps on the skull was phrenology- Francis Gall Biology • Researchers who study the links between biology and behavior are called biological psychologists. • We are made up of smaller and smaller subsystems; we are also part of larger systems. Thus we are biopsychosocial systems. Neural Communication We are a biopsychosocial system. Cellular Level (Interconnected Neurons) Ethnic Level (Culture) Organ Level (Brain) Group Level (Family) System Level (Information Processing) Individual Level (Human Being) Community Level (Society) 3 Neural Communication Neurobiologists and other investigators understand that humans and animals operate similarly when processing information. Note the similarities in the above brain regions, which are all engaged in information processing. 4 Neural Communication • Our body’s neural system is built from billions of nerve cells, or neurons. Info arriving from brain and spinal cord from the body travels in sensory neurons. Instructions from the brain and spinal cord are sent to the body’s tissue via motor neurons. The neurons that enable internal communication within the brain are called interneurons. Neural Communication • The extensions of a neuron that receive messages from other neurons are the dendrites. The extension of a neuron that transmits info to other neurons is the axon; some of these extensions are insulated by a fatty tissue called the myelin sheath; which helps speed the neuron’s impulses. Neural Communication • The neural impulse, or action potential, is a brief electrical charge that travels down an axon. The fluid interior of a resting axon carries mostly negatively charged ions, while the fluid outside has mostly positively charged ions. This polarization, called the resting potential, occurs because the cell membrane is selectively permeable. Neural Communication • An action potential occurs when the first part of the axon opens its gates and negatively charged ions rush in, causing that part of the neuron to become depolarized. During the resting pause following an action potential, called the refractory period, the neuron pumps positively charged ions back outside the cell. Depolarization & Hyperpolarization Depolarization: Depolarization occurs when positive ions enter the neuron, making it more prone to firing an action potential. Hyperpolarization occurs when negative ions enter the neuron, making it less prone to firing an action potential. 9 Neural Communication • To trigger a neural impulse, excitatory signals minus inhibitory signals must exceed a certain intensity, called the threshold. Increasing a stimulus above this level will NOT increase the neural impulse’s intensity. This phenomenon is called all or none response. Neural Communication • The strength of a stimulus does NOT affect the intensity of a neural impulse. A strong stimulus can trigger more neurons to fire. How nerve cells communicate • The junction between two neurons is called a synapse; and the gap is called the synaptic cleft. Discovery was made by Sir Charles Sherrington. How nerve cells communicate • The chemical messengers that convey information across the gaps between neurons are called neurotransmitters. These chemicals bind to receptor sites and unlock tiny channels, allowing electrically charged atoms to enter the neuron. How nerve cells communicate • Neurotransmitters influence neurons either by exciting or inhibiting their readiness to fire. Excess neurotransmitters are reabsorbed by the sending neuron in a process called reuptake. How Neurotransmitters Influence Us? Serotonin pathways are involved with mood regulation. From Mapping the Mind, Rita Carter, © 1989 University of California Press 15 Dopamine Pathways Dopamine pathways are involved with diseases such as schizophrenia and Parkinson’s disease. From Mapping the Mind, Rita Carter, © 1989 University of California Press 16 Neurotransmitters 17 Agonists 18 Antagonists 19 Lock & Key Mechanism Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism. 20 How Neurotransmitters Influence Behavior • A neurotransmitter that is important in muscle contraction is acetylcholine; It is also important in learning and memory. • Naturally occurring opiate like neurotransmitters that are present in the brain are called endorphins. Endorphins help explain runner’s high, painkilling effects of acupuncture • When the brain is flooded with drugs such as heroin or morphine. It may stop producing these neurotransmitters. How Neurotransmitters Influence Behavior • Drugs that produce their effects by mimicking neurotransmitters are called agonists. Drugs that block the effects of neurotransmitters by occupying their receptor sites are called antagonists. While certain opiate drugs create a temporary “high” by mimicking the endorphins, the poison curare produces paralysis by block the activity of the neurotransmitter ACh. The Nervous System • Taken altogether, the neurons of the body form the nervous system. The brain and spinal cord form the central nervous system. The neurons that link the brain and spinal cord to the body’s sense receptors, muscles, and glands form the peripheral nervous system. • Sensory and motor axons are bundled into electrical cables called nerves. The Nervous System Nervous System: Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system. Central Nervous System (CNS): the brain and spinal cord. Peripheral Nervous System (PNS): the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body. 24 The Nervous System • The division of the peripheral nervous system that enables voluntary control of the skeletal muscles is the somatic nervous system. • Involuntary, self regulating responsesthose of the glands and muscles of internal organs- are controlled by the autonomic nervous system. The Nervous System • The body is made ready for action by the sympathetic division of the autonomic nervous system. The parasympathetic division of the autonomic nervous system produces relaxation. The Nervous System • Neural clusters work into groups called neural networks. • Automatic responses to stimuli, called reflexes, illustrate the work of the spinal cord. Simple pathways such as these are involved in the knee- jerk response and in the pain reflex. Central Nervous System The Spinal Cord and Reflexes Simple Reflex 28 The Nervous System Neurons in the brain connect with one another to form networks Inputs The brain learns by modifying certain connections in response to feedback Neural Networks interconnected neural cells with experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results computer simulations of Outputs neural networks show analogous learning Interneurons- brains internal communication system- we have billions of interneurons Endocrine System • The body’s chemical communication is called the endocrine system. This system transmits information through chemical messengers called hormones at a much slower rate than the nervous system, and its effects last a longer time. Endocrine System • In a moment of danger, the ANS orders the adrenal glands to release epinephrine and norepinephrine. • The most influential gland is the pituitary, which, under the control of an adjacent brain area called the hypothalamus, helps regulate growth and the release of hormones by other endocrine glands. The Brain Techniques to Study the Brain A brain lesion experimentally destroys brain tissue to study animal behaviors after such destruction. The oldest technique for studying the brain involves clinical observations of patients with brain injuries or diseases. Hubel (1990) 32 Electroencephalogram (EEG) An amplified recording of the electrical waves sweeping across the brain’s surface, measured by electrodes placed on the scalp. AJ Photo/ Photo Researchers, Inc. 33 PET Scan Courtesy of National Brookhaven National Laboratories PET (positron emission tomography) Scan is a visual display of brain activity that detects a radioactive form of glucose while the brain performs a given task. 34 MRI Scan MRI (magnetic resonance imaging) uses magnetic fields and radio waves to produce computergenerated images that distinguish among different types of brain tissue. Top images show ventricular enlargement in a schizophrenic patient. Bottom image shows brain regions when a participants lies. Both photos from Daniel Weinberger, M.D., CBDB, NIMH James Salzano/ Salzano Photo Lucy Reading/ Lucy Illustrations 35 Older Brain Structures The Brainstem is the oldest part of the brain, beginning where the spinal cord swells and enters the skull. It is responsible for automatic survival functions. 36 Brain Stem The Medulla [muh-DULuh] is the base of the brainstem that controls heartbeat and breathing. Just above this part is the pons which help coordinate movements. Reticular Formation is a nerve network in the brainstem that plays an important role in controlling arousal. 37 Brain Stem The Thalamus [THAL-uhmuss] is the brain’s sensory switchboard, located on top of the brainstem. It directs messages to the sensory areas in the cortex and transmits replies to the cerebellum and medulla. (receives info from all senses except smell) 38 Cerebellum The “little brain” attached to the rear of the brainstem. Influences nonverbal learning and helps coordinate voluntary movements and balance. 39 The Limbic System The Limbic System is a doughnut-shaped system of neural structures at the border of the brainstem and cerebrum, associated with emotions such as fear, aggression and drives for food and sex. It includes the hippocampus, amygdala, and hypothalamus. 40 Amygdala The Amygdala [ah-MIGdah-la] consists of two almond-shaped neural clusters linked to the emotions of fear and anger. 41 Hypothalamus The Hypothalamus lies below (hypo) the thalamus. It directs several maintenance activities like eating, drinking, body temperature, and control of emotions. It helps govern the endocrine system via the pituitary gland. 42 Reward Center Sanjiv Talwar, SUNY Downstate Rats cross an electrified grid for self-stimulation when electrodes are placed in the reward (hypothalamus) center (top picture). When the limbic system is manipulated, a rat will navigate fields or climb up a tree (bottom picture). 43 The Cerebral Cortex The intricate fabric of interconnected neural cells that covers the cerebral hemispheres. It is the body’s ultimate control and information processing center. 44 Structure of the Cortex Each brain hemisphere is divided into four lobes that are separated by prominent fissures. These lobes are the frontal lobe (forehead), parietal lobe (top to rear head), occipital lobe (back head) and temporal lobe (side of head). 45 Functions of the Cortex The Motor Cortex is the area at the rear of the frontal lobes that control voluntary movements. The Sensory Cortex (parietal cortex) receives information from skin surface and sense organs. 46 Visual Function Courtesy of V.P. Clark, K. Keill, J. Ma. Maisog, S. Courtney, L.G. Ungerleider, and J.V. Haxby, National Institute of Mental Health The functional MRI scan shows the visual cortex is active as the subject looks at faces. 47 Auditory Function The functional MRI scan shows the auditory cortex is active in patients who hallucinate. 48 Association Areas More intelligent animals have increased “uncommitted” or association areas of the cortex. 49 Language Aphasia is an impairment of language, usually caused by left hemisphere damage either to Broca’s area (impaired speaking) or to Wernicke’s area (impaired understanding). 50 Specialization & Integration Brain activity when hearing, seeing, and speaking words 51 The Brain’s Plasticity The brain is sculpted by our genes but also by our experiences. Plasticity refers to the brain’s ability to modify itself after some type of injury or illness. 52 Our Divided Brain Our brain is divided into two hemispheres. The left hemisphere processes reading, writing, speaking, mathematics, and comprehension skills. In the 1960s, it was termed as the dominant brain. 53 Splitting the Brain A procedure in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them. Martin M. Rother Courtesy of Terence Williams, University of Iowa Corpus Callosum 54 Split Brain Patients With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot. 55 Divided Consciousness 56 Try This! Try drawing one shape with your left hand and one with your right hand, simultaneously. BBC 57 Non-Split Brains People with intact brains also show left-right hemispheric differences in mental abilities. A number of brain scan studies show normal individuals engage their right brain when completing a perceptual task and their left brain when carrying out a linguistic task. 58 Brain Organization & Handedness Is handedness inherited? Yes. Archival and historic studies, as well as modern medical studies, show that the right hand is preferred. This suggests genes and/or prenatal factors influence handedness. 59 Is it Alright to be Left Handed? Being left handed is difficult in a right-handed world. 60 Is it Alright to be Left Handed? The percentage of left-handed individuals decreases sharply in samples of older people (Coren, 1993). 61 Deep Brain Stimulation • Deep-brain stimulation (DBS) was first developed in France in 1987 and evolved out of the so-called ablative, or lesioning, surgeries in which doctors use heat probes to burn and permanently damage small regions of the brain — in the case of Parkinson's, regions where patients' tremors and quakes are known to arise. These same brain areas are targeted with DBS, but instead of destroying tissue, doctors implant slender electrodes that pump steady pulses of electricity — think of it as a sort of pacemaker for the brain. Kinds of Neurons Sensory Neurons carry incoming information from the sense receptors to the CNS. Motor Neurons carry outgoing information from the CNS to muscles and glands. Interneurons connect the two neurons. Interneuron Neuron (Unipolar) Sensory Neuron (Bipolar) Motor Neuron (Multipolar) 63 Brain Studies • Reticular FormationMoruzi/ Magounelectrically stimulating the reticular formation of a sleeping cat instantly produced an awake, alert animal. Vice versa, severing the cat’s reticular formation caused the cat to lapse into a coma which it will never awake Brain Studies • Kluver and Bucy surgically lesioned the part of a rhesus monkey’s brain that included the amygdala. What happened? Made the animal very mellow • What happens when we stimulate the amygdala in a placid domestic animal? One minute- attacks, hisses, pupils dilate; the next cowers in terror. Hypothalamus Case Study • • • • Olds and Milner- goal was to implant electrode in cat’s reticular formation when they accidently hit the hypothalamus- brain’s reward center Located other pleasure centers they named reward centers When rats could trigger their own stimulation- they would go at a feverish pace- 7,000 times per houruntil they dropped from exhaustion How does this translate to humans? Theory is some of us may suffer from reward deficiency syndrome- genetic disposed deficiency that leads people to crave missing pleasures or relive negative feelings. This causes disorders such s alcohol dependence, drug abuse, and binge eating Fritch and Hitzig Mapping of Motor Cortex• Fritch and Hitzigdiscovered motor cortexarch shaped region at back of the frontal lobe; by applying mild electrical stimulation to a dog’s cortex which made its body move. Effects were selective. Morever, stimulating the right hemisphere, moved the left side of the body and vice versa. Phineas Gage • 25 year old foreman- had a rod go right through skull- immediately got up and spoke. Returned to work- irritable, profane, dishonest- mental ability and memory intact; personality changedShowed the brain can reorganize itself Plasticity + Numerous Studies • • • Plasticity- brains ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience Brains are most plastic when we are young children Constraint induced therapy- forces use of the “bad hand or bad leg” and brain gradually learns to recover lost skills • • • Deaf- have enhanced peripheral vision due to temporal lobe helping out with vision V.S. Ramachandran- when stroking the arm of someone whose hand has been amputated, person felt sensations not only on the area stroked but also on the nonexistent finger Hemispherectomy is a surgical procedure where one cerebral hemisphere (half of the brain) is removed or disabled. This procedure is used to treat a variety of seizure disorders where the source of the epilepsy is localized to a broad area of a single hemisphere of the brain. It is solely reserved for extreme cases in which the seizures have not responded to medications and other less invasive surgeries. Blood Brain Barrier • • • • • • • • The BBB has several important functions: Protects the brain from "foreign substances" in the blood that may injure the brain. Protects the brain from hormones and neurotransmitters in the rest of the body. Maintains a constant environment for the brain. General Properties of the BBB Large molecules do not pass through the BBB easily. Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules, such as barbiturate drugs, rapidly cross through into the brain. Molecules that have a high electrical charge are slowed.