The Biology of Mind - Modules 4-6

Module 4-6: The Biology of Mind

Head Transplants: A Hypothetical Scenario

The Experiment: Two transplant surgeons, Sergio Canavero and Xiaoping Ren, are planning a head transplant. Wang Huanming, paralyzed from the neck down, volunteered to have his head transplanted onto a brain-dead person's body.
Ethical Concerns: The procedure raises serious ethical issues, with some calling it "reckless and ghastly."
Cost and Feasibility: The procedure is estimated to cost $100 million and faces the seemingly insurmountable challenge of reconnecting spinal cord nerves.
Questions of Identity: Assuming the procedure could work, it raises questions about identity, skills, and parental lineage. Would Wang still be Wang? Whose home should he return to? Would he retain skills from his old life?
The Presumption: Most people presume that even with a new body, Wang's brain would make him who he is, suggesting the brain provides identity and enables the mind. No brain, no mind.

Biology, Behavior, and Mind

Central Principle: Everything psychological is simultaneously biological.
Every idea, mood, and urge is a biological happening. You love, laugh, and cry with your body.
Thinking, feeling, or acting without a body would be like running without legs. Without your body (genes, nervous system, hormones, appearance), you would be nobody.
Interaction: The body and brain influence and are influenced by experiences.
Shared Design, Individual Differences: Humans share a basic biological design, but differ due to genes, experiences, cultural traditions, and teachings.
Nature and Nurture: Traits and behaviors arise from the interaction of nature and nurture.
Top-Down Influence: Thoughts, feelings, and actions influence blood pressure, hormones, health, and the brain. Biology changes in response to behaviors and environments.
Nurture on Nature: Nurture works on what nature provides.

Module Overview

Modules 4-6 explore the mind's biology, starting with nerve cells and building up to the brain.
The discussion also includes how behavior and environment can influence biology.

4 Neural and Hormonal Systems

Biological Psychology: The scientific study of the links between biological (genetic, neural, hormonal) and psychological processes.

Biology, Behavior, and Mind

Hippocrates: Correctly located the mind in the brain.
Aristotle: Believed the mind was in the heart.
Phrenology: In the early 1800s, Franz Gall proposed that studying bumps on the skull could reveal a person's mental abilities and character traits. This focused attention on the localization of function.
Localization of Function: The idea that various brain regions have particular functions.
Modern Biological Psychology: Uses advanced technologies to study the interplay of biology and behavior and mind.

Key Discoveries in the Biology of Mind

The adaptive brain is wired by experiences.
Nerve cells (neurons) conduct electricity and communicate by sending chemical messages across tiny gaps.
Specific brain systems serve specific functions.
Information processed in different brain systems is integrated to construct our experience.
Biopsychosocial Systems: Tiny cells organize to form body organs, which form larger systems for digestion, circulation, and information processing. These systems are part of an even larger system: the individual, who is part of a family, community, and culture.

The Power of Plasticity

Neuroplasticity: The brain's ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience. Your brain is sculpted by both genes and life experiences. It is greatest in childhood, but continues throughout life.
Taxi Driver Trainees: London taxi driver trainees who learn the city's street locations develop an enlarged hippocampus.
Musicians: Well-practiced pianists have a larger-than-usual auditory cortex area.
Brain as a Work in Progress: The brain you were born with is not the brain you will die with.
Adaptation: Neuroplasticity enables humans to adapt to a rapidly changing world.

Neural Communication

Animal Similarities: The information systems of humans and other animals operate similarly, allowing researchers to study simpler animals to understand our neural systems.

Neurons

Neurons (Nerve Cells): The building blocks of the neural information system. New neurons are born, and unused neurons wither away.
Neuron Structure: Each neuron consists of a cell body and branching fibers.
Dendrites: Receive and integrate information, conducting it toward the cell body. They listen.
Axon: Passes the message through its terminal branches to other neurons or to muscles or glands. They speak.
Axon Length: Axons may be very long.
Myelin Sheath: A layer of fatty tissue that insulates axons and speeds their impulses. It is laid down up to about age 25, increasing neural efficiency, judgment, and self-control.
Multiple Sclerosis: Results from the degeneration of the myelin sheath. Communication to muscles and brain regions slows, with diminished muscle control and sometimes impaired cognition.
Glial Cells (Glia): Support, nourish, and protect neurons. Glia also play a role in learning, thinking, and memory. Einstein's brain had a much greater concentration of glial cells than average.

The Neural Impulse

Action Potential: A brief electrical charge that travels down an axon, transmitting messages.
Neural Impulse Speed: Varies from 2 miles (3 kilometers) per hour to more than 200 miles (320 kilometers) per hour.
Brain Activity Measurement: Measured in milliseconds. Computer activity is measured in nanoseconds.
Chemical Events: Neurons generate electricity from chemical events. Ions (electrically charged atoms) are exchanged.
Resting Potential: The positive-outside/negative-inside state of an axon's surface.
Selective Permeability: The axon's surface is selective about what it allows through its gates.
Depolarization: Loss of the inside/outside charge difference. Positive ions flood in, causing the next section of axon channels to open.
Threshold: If excitatory signals exceed the inhibitory signals by a minimum intensity, the combined signals trigger an action potential.
Refractory Period: A resting pause during which subsequent action potentials cannot occur until the axon returns to its resting state.
All-or-None Response: A neuron's reaction of either firing (with a full-strength response) or not firing. Increasing the level of stimulation above the threshold will not increase the neural impulse's intensity.

How Neurons Communicate

Synapse: The meeting point between neurons, with a tiny synaptic gap (or synaptic cleft).
Ramón y Cajal: Marveled at these near-unions of neurons, calling them "protoplasmic kisses."
Neurotransmitters: Chemical messengers released when an action potential reaches the button-like terminals at an axon's end.
Receptor Sites: Neurotransmitter molecules cross the synaptic gap and bind to receptor sites on the receiving neuron.
Reuptake: Excess neurotransmitters are reabsorbed by the sending neuron or broken down by enzymes.
Some antidepressant medications partially block the reuptake of mood-enhancing neurotransmitters.

How Neurotransmitters Influence Us

Neurotransmitter Variety: Researchers have discovered several dozen neurotransmitters.
Specific Effects: Particular neurotransmitters affect specific behaviors and emotions.
Acetylcholine (ACh): Plays a role in learning, memory, and muscle action. When ACh is released to our muscle cell receptors, the muscle contracts. If ACh transmission is blocked, muscles are paralyzed.
Endorphins: Natural, opiate-like neurotransmitters linked to pain control and pleasure. They help explain good feelings such as the "runner's high" and the painkilling effects of acupuncture. Our body releases several types of neurotransmitter molecules similar to morphine in response to pain and vigorous exercise.

How Drugs and Other Chemicals Alter Neurotransmission

Agonist Molecules: Increase a neurotransmitter's action. Some may increase the production or release of neurotransmitters or block reuptake in the synapse. Others mimic the excitatory or inhibitory effects of a neurotransmitter.
Antagonist Molecules: Decrease a neurotransmitter's action by blocking production or release. Botulin (Botox) causes paralysis by blocking ACh release. Curare, a poison, occupies and blocks ACh receptor sites on muscles, producing paralysis.

The Nervous System

Nervous System: The body's communication network that takes in information, makes decisions, and sends back information to the body's tissues.
Central Nervous System (CNS): The brain and spinal cord, the body's decision maker.
Peripheral Nervous System (PNS): Responsible for gathering information and transmitting CNS decisions to other body parts.
Nerves: Electrical cables formed from bundles of axons, linking the CNS with the body's sensory receptors, muscles, and glands.

Types of Neurons

Sensory Neurons (Afferent): Carry messages from the body's tissues and sensory receptors inward to the brain and spinal cord for processing.
Motor Neurons (Efferent): Carry instructions from the central nervous system outward to the body's muscles and glands.
Interneurons: Process information between the sensory input and motor output.

The Peripheral Nervous System

Somatic Nervous System: Enables voluntary control of our skeletal muscles.
Autonomic Nervous System (ANS): Controls our glands and our internal organ muscles. The ANS influences functions such as glandular activity, heartbeat, and digestion.
Sympathetic Nervous System: Arouses and expends energy.
Parasympathetic Nervous System: Conserves energy as it calms you.
Homeostasis: The sympathetic and parasympathetic nervous systems work together to keep us in a steady internal state.

The Central Nervous System

Brain: Enables our humanity—our thinking, feeling, and acting. It contains approximately 86 billion neurons.
Neural Networks: Neurons network with nearby neurons with which they can have short, fast connections; each layer's cells connect with various cells in the neural network's next layer. Learning occurs as experience strengthens connections. (Neurons that fire together wire together).
Spinal Cord: A two-way information highway connecting the peripheral nervous system and the brain.
Reflexes: Automatic responses to stimuli. A simple spinal reflex pathway is composed of a single sensory neuron and a single motor neuron. These often communicate through an interneuron.

The Endocrine System

Endocrine System: Contains glands and fat tissue that secrete hormones into the bloodstream.
Hormones: Chemical messengers that travel through the bloodstream and affect other tissues, including the brain.
Hormones influence our interest in sex, food, and aggression.
Speed: The nervous system zips messages faster from eyes to brain to hand. Endocrine messages trudge slower in the bloodstream.
Duration: Endocrine messages tend to outlast the effects of neural messages.
Adrenal Glands: Release epinephrine and norepinephrine (adrenaline and noradrenaline), which increase heart rate, blood pressure, and blood sugar, providing a surge of energy.
Pituitary Gland: The endocrine system's most influential gland, controlled by the hypothalamus. It releases a growth hormone and oxytocin, which promotes social bonding. triggers your sex glands to release sex hormones. Under the brain's influence, the pituitary triggers your sex glands to release sex hormones.
A stressful event triggers your hypothalamus to instruct your pituitary to release a hormone that causes your adrenal glands to flood your body with cortisol, a stress hormone that increases blood sugar.
Intimate Connection: The nervous system directs endocrine secretions, which then affect the nervous system.

5 Tools of Discovery, Older Brain Structures, and the Limbic System

The Tools of Discovery: Having Our Head Examined

Lesion: Destroy tiny clusters of normal or defective brain cells, observing any effect on brain function.
Stimulation: Stimulate various brain parts-electrically, chemically, or magnetically-and note the effect.
Microelectrodes: Detect the electrical pulse in a single neuron.
Optogenetics: Control the activity of individual neurons by programming them to become receptive to light.
EEG (Electroencephalogram): An amplified readout of electrical activity sweeping across the brain's surface.
MEG (Magnetoencephalography): Measures magnetic fields from the brain's natural electrical activity.
PET (Positron Emission Tomography) Scan: Depicts brain activity by showing each brain area's consumption of its chemical fuel, the sugar glucose.
MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves to produce computer-generated images of soft tissue. MRI scans show brain anatomy.
fMRI (Functional MRI): Reveals blood flow and, therefore, brain activity by comparing successive MRI scans. fMRI scans show brain function as well as structure.
fNIRS (functional near-infrared spectroscopy): Uses infrared light that shines onto blood molecules to identify brain activity.
Brain imaging enables a crude eavesdropping on the mind.
Neuroimaging techniques illuminate brain structure and activity and sometimes help us test different theories of behavior. But given that all human experience is brain-based, it's no surprise that different brain areas become active when one listens to a lecture or lusts for a lover.
Today's techniques for peering into the thinking, feeling brain are doing for psychology what the microscope did for biology and the telescope did for astronomy. From them we have learned more about the brain in the last 100 years than in the previous 10,000.
Major funding goes into brain research: Europe's Human Brain Project; The Human Connectome Project seeks to map the brain's long-distance connections by harnessing the power of diffusion spectrum imaging.

Older Brain Structures

The Brainstem

Brainstem: The brain's oldest and innermost region. Brainstem components perform for us much as they did for our distant ancestors. Base is the medulla.
Medulla: Controls heartbeat and breathing.
Pons: Helps coordinate movements and control sleep.
Cut off from the brain's higher regions, a cat won't purposefully run or climb to get food.
The brainstem is a crossover point, where most nerves to and from each side of the brain connect with the body's opposite side.

The Thalamus

Thalamus: Sits atop the brainstem and acts as the brain's sensory control center. It receives information from all the senses except smell, and routes that information to the higher brain regions that deal with seeing, hearing, tasting, and touching. The thalamus also receives some of the higher brain's replies, which it then directs to the medulla and to the cerebellum.

The Reticular Formation

Reticular Formation: A nerve network extending from the spinal cord right up through the thalamus. It filters incoming stimuli and relays important information to other brain areas and controls arousal.

The Cerebellum

Cerebellum: Extends from the rear of the brainstem and is baseball-sized. It enables nonverbal learning and skill memory. Along with the basal ganglia, deep brain structures involved in motor movement.
The cerebellum helps you judge time, discriminate textures and sounds, and control your emotions and social behaviors. With assistance from the pons, it also coordinates voluntary movement.
These older brain functions all occur without any conscious effort.

The Limbic System

Limbic System: Associated with emotions and drives and contains the amygdala, the hypothalamus, and the hippocampus.

The Amygdala

Amygdala: Two lima-bean-sized neural clusters enabling aggression and fear.
Monkeys and humans with amygdala damage become less fearful of strangers. Other studies link criminal behavior with amygdala dysfunction. When people view angry and happy faces, only the angry ones increase activity in the amygdala. And when negative events energize the amygdala, they become more memorable.

The Hypothalamus

Hypothalamus: An important link in the command chain governing bodily maintenance. Neural clusters influence hunger, thirst, body temperature, and sexual behavior. Together, they help maintain a steady (homeostatic) internal state.
To monitor your body state, the hypothalamus tunes in to your blood chemistry and any incoming orders from other brain parts. Influence on hormones intensifies the thoughts of sex in your cerebral cortex.
Open-minded investigators made an unexpected observation: McGills James Olds and Peter Milner found a brain center that provides pleasurable rewards when they misplaced an electrode in hypothalamus.
Animal research has also revealed both a general dopamine-related reward system and specific centers associated with the pleasures of eating, drinking, and sex. Animals, it seems, come equipped with built-in systems that reward activities essential to survival.
Researchers have discovered other limbic system reward centers, such as the nucleus accumbens in front of the hypothalamus.
Experiments have also revealed the effects of a dopamine-related reward system in people. For example, experimentally boosting dopamine levels increases the pleasurable "chills" ". Some researchers believe that many disordered behaviors may stem from malfunctions in natural brain systems for pleasure and well-being. People genetically predisposed to this reward deficiency syndrome may crave whatever provides that missing pleasure or relieves negative feelings, such as aggression, fattening food, or drugs alcohol.

The Hippocampus

Hippocampus: Processes conscious, explicit memories. Humans who lose their hippocampus lose their ability to form new memories of facts and events. Hippocampus size and function decrease as we grow older, which furthers cognitive decline.

6 The Cerebral Cortex

The Cerebral Cortex

Cerebral Cortex: Newer neural networks within the cerebrum form specialized work teams that enable our perceiving, thinking, and speaking. Covering those hemispheres, like bark on a tree, is the cerebral cortex, a thin surface layer of interconnected neural cells. In our brain's evolutionary history, the cerebral cortex—our brain's thinking crown—is a relative newcomer.
As we move up the ladder of animal life, the cerebral cortex expands, tight genetic controls relax, and the organism's adaptability increases. What makes us distinctively human is the size and interconnectivity of our cerebral cortex.

Structure of the Cortex

The cerebral cortex contains some 20 to 23 billion of the brain's nerve cells and 300 trillion synaptic connections (de Courten-Myers, 2005).
Each hemisphere's cortex is subdivided into four lobes, separated by prominent fissures, or folds. Starting at the front of your brain and moving over the top: frontal, parietal, occipital, temporal lobes. Each carry out many functions and require interplay of several lobes.

Functions of the Cortex

More than a century ago, surgeons found damaged cortical areas during autopsies of people who had been partially paralyzed or speechless. This rather crude evidence did not prove that specific parts of the cortex control complex functions like movement or speech.

Motor Functions

In 1870, German physicians Gustav Fritsch and Eduard Hitzig made an important discovery: mild electrical stimulation to parts of an animal's cortex made parts of its body move. They had discovered what is now called the motor cortex.
In the 1930s, Otfrid Foerster and Wilder Penfield were able to map the motor cortex in hundreds of wide-awake patients by stimulating different cortical areas and observing responses. They discovered that body areas requiring precise control, such as the fingers and mouth, occupy the greatest amount of cortical space.
Scientists can predict a monkey's arm motion just before it moves by repeatedly measuring motor cortex activity preceding specific arm movements. Scientists have also observed monkeys' motor cortex neurons responding differently when executing a social act (putting an object in an experimenter's hand) rather than a nonsocial act (putting something in a container or in their own mouth).

Brain-Machine Interfaces

Implants in motor cortexes to monitor signals and operate the joystick, rewarding monkeys for using a joystick to follow a moving red target.
Clinical trials with people who have severe paralysis or have lost a limb: able to control a TV, draw shapes on a computer screen, and play video games thanks to an aspirin-sized chip recording in his motor cortex.
lan Burkhart, who lost use of his arms and legs, helped create computer to stimulate his motor cortex so that he was able to grasp bottle with his own paralyzed arm. By learning Burkhart's unique brain response patterns, the computer can predict his brain activity to help him make these movements.
Microelectrodes could someday detect complex thoughts to enable people to control their environment with greater precision. Scientists have even created a prosthetic voice creating understandable speech by reading the brain's motor commands that direct vocal movement.

Sensory Functions

Somatosensory Cortex: Parallel to and just behind the motor cortex that specializes in receiving information from the skin senses in order to move body parts.
The more sensitive the body region, the larger the somatosensory cortex area devoted to it.
Visual cortex in occipital lobes so that it is possible to witness flashes of light if one is stimulated in the occipital lobes.
Sound processed by auditory cortex in temporal lobes; If stimulated in auditory cortex, might hear a sound. In MRI scans people with schizophrenia display during auditory hallucinations.

Association Areas

These areas use 3/4 of the cerebrum and, unlike the aforementioned areas, do not allow responses to external stimuli, making it difficult to test for observation.
Prefrontal cortex in the frontal lobes enables judgment, planning, social interactions, and processing of new memories.
Damage to prefrontal cortex results in high intelligence and cake-baking skills, but an inability to remember or plan towards parties, to bake the cake or to feel regret for not doing it.
Damage to prefrontal cortex also causes alterations to personality and inhibitions as seen in the case of Phineas Gage: normally friendly, but now irritable, profane, and dishonest; said to no longer be "Gage".
*Frontal lobes help steer us toward kindness and away from violence, their dysfunction causes patients to be no longer be able to tell right from wrong, thus rendering their morals and moral actions ineffective
Parietal lobes enable mathematical and spatial reasoning. Stimulation of one parietal lobe area can generate sensation of wanting to move another location in body, as opposed to actual movement occurring.
Right Temporal Lobe Association in recognizing faces. Strokes impacting this area renders patients unable to recognize faces, even loved ones.
Brain Activity, functional Connectivity, and overall Health: Brain scans show that, like humans, dogs usually process words with their left hemisphere and intonation with a right hemisphere region. People are at increased risk for a variety of mental disorders when brain areas struggle to communicate with each other such to memory, language, attention, and social skills that comes with distinct, integrated brain areas and neural networks.

Responses to Damage

Brain displays neuroplasticity, ability to change in response to experiences, both good and bad.
Severed brain and spinal cord neurons, unlike cut skin, do not regenerate. If spinal cord were severed, you would probably be permanently paralyzed; preassigned to one brain in function.
Neuroplasticity may also occur after serious damage, especially in young children (Kolb, 1989; see also FIGURE 6.7).
Constraint-induced therapy aims to rewire brains and improve the dexterity as damaged-brain functions migrated to other brain regions, therapist force patients to use the limb with impaired skill.
Blindness/deafness leads to unused brain area used by sound or smell.
Slow-growing left hemisphere tumor has right-hemisphere compensate for language.
Brain often attempts self-repair by reorganizing existing tissue, researchers are debating whether it can also mend itself through neurogenesis-producing new neurons.
Brain, a lot more than the average organ, can be improved and expanded during stem cell research, where mass-produced parts could be injected into damaged areas and have it regenerate for a new cell. Can be increased through sleep, execrise, and having little external stress factors.

The Divided Brain

Our brain's look-alike left and right hemispheres serve differing functions called lateralization. This later.alization is apparent after brain damage. When right is damaged: less dramatic of affects when there is similar left hemisphere damage i.e impairing in reading, writing, speaking, arithmetic reasoning, and understanding.

Splitting the Brain

In the early 1960s, the Corpus Callosum, major epileptic seizures were caused by an amplification of abnormal brain activity bouncing back and forth between the two cerebral hemispheres, which work together as a whole system, were severed. No ill effects of the actions in Sperry et al.'s research.
Patients with split brains were surprisingly normal, their personality and intellect hardly affected. Allowed in-depth research of function in each hemisphere by seeing each hemisphere of eye.
Knowing these facts, Sperry and Gazzaniga could send information to a patient's left or right hemisphere. Because the split-brain surgery had cut the communication lines between the hemispheres, the researchers could, with these patients, quiz each hemisphere separately.
After research on patients with split brains, the left was deduced: