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UNIT 1
Who said brain was responsible for thoughts and emotions and not heart and then what happened? Hippocrates Brain is responsible for thoughts and emotions and not the heart Plato Agreed Then Galen came and said fluids of the brain in ventricles were responsible for sensations, reasoning, judgment, memory, and movement
1. Franz Joseph Gallʼs Legacy: The Birth of Functional Localization, who was he? What did he do? problems and advantages of it? 🧠 Franz Joseph Gall 1758 1828 was a German physician and anatomist best known for developing phrenology —the idea that the shape of a personʼs skull reflects their personality, intelligence, and mental abilities.
1. What Did Gall Do? (Phrenology Explained)
🔹 Gall believed that: The brain is made up of different regions , each responsible for a specific personality trait (e.g., love, memory, aggression). These traits could be measured by feeling the bumps on a personʼs skull. If a brain region was more developed, it would cause a bump on the skull, while a weak region would create a dent. By studying skull shapes, he thought he could predict a personʼs behavior and abilities. 🔹 He and his followers mapped the brain into different regions, assigning them specific mental functions.
2. Problems with Phrenology (Why It Was Wrong)
🔴 No Scientific Evidence There was no real proof that bumps on the skull matched brain functions.
🔴 Wrong Assumptions About Brain Growth The skull does not change shape based on brain use. 🔴 Oversimplified Behavior Complex behaviors like "kindness" or "criminality" cannot be traced to a single brain spot. 🔴 Led to Discrimination Phrenology was used to justify racism, sexism, and classism , claiming certain groups were "naturally superior." 🔹 By the mid-1800s, scientists debunked phrenology using more advanced brain studies.
3. Gallʼs Contributions (What He Got Right!)
✅ First to Suggest That Different Brain Areas Have Different Functions Even though phrenology was wrong, Gallʼs idea of functional localization was correct! This influenced later discoveries, like Brocaʼs area (speech production) and Wernickeʼs area (language comprehension). ✅ Promoted the Idea That the Brain Controls Behavior Before Gall, people believed behavior came from the soul or heart. He was one of the first to argue that the brain is responsible for personality and mental functions. ✅ Inspired Modern Neuroscience Even though phrenology was a pseudoscience , it led scientists to study brain localization properly. His ideas influenced later brain researchers like Paul Broca, Carl Wernicke, and Wilder Penfield. Who is Johann Spurzheim? What did he do? problems and advantages?
Johann Spurzheim: Expanding Phrenology After Gall
Who was he?
3. Problems with Spurzheimʼs Work
❌ Further Misinformation He made phrenology even more pseudoscientific by adding moral and religious aspects. ❌ No Scientific Evidence His expansion of Gallʼs ideas had no experimental proof. ❌ Used for Social Control His version of phrenology was used to justify racism, classism, and biases in education and employment.
4. Spurzheimʼs Legacy
🚀 What He Did Right: Spread the idea that different brain areas control different functions (though inaccurately). Helped people think about the brainʼs role in personality and behavior. Inspired early brain research , even if his methods were wrong. ❌ What He Got Wrong: Made phrenology even less scientific by adding moral and religious ideas. Helped phrenology become a major pseudoscience , delaying real brain research. Promoted ideas that were used for discrimination and social inequality. 🔬 Final Verdict: Spurzheim made phrenology famous but turned it into a pseudoscience. His work helped shape early discussions on the brain, but real neuroscience moved forward without phrenology. Tell Brocaʼs and Wernieckeʼs Discoveries? Gallʼs idea of functional localization —the belief that different brain areas control different mental functions—was revolutionary, even though phrenology itself was later discredited. His work influenced:
🔹 Brocaʼs and Wernickeʼs Discoveries (1860s–1870s)
Paul Broca 1861 Discovered that damage to the left frontal lobe Brocaʼs area) caused speech impairment, proving that language function is localized. Carl Wernicke 1874 Identified Wernickeʼs area in the temporal lobe , responsible for language comprehension. Impact These discoveries confirmed that specific cognitive functions have dedicated brain regions, supporting Gallʼs core idea of localization Phineas Gage Case Study: The Man Who Survived a Brain Injury
Who was Phineas Gage?
🧠 Phineas Gage 1823 1860 was a railroad worker in the United States who became famous after a severe brain injury dramatically changed his personality. His case provided key insights into the role of the frontal lobe in personality, decision-making, and social behavior.
1. What Happened to Phineas Gage? (The Accident)
🔹 On September 13, 1848 , Gage was working on a railroad in Vermont. 🔹 While using a tamping iron (a metal rod) to pack explosives into a rock, the gunpowder accidentally exploded. 🔹 The iron rod 3 feet 7 inches long, 1.25 inches in diameter, and 13 pounds in weight) shot through his left cheek, behind his eye, and out through the top of his skull. 🔹 Surprisingly, he did not lose consciousness and could walk and talk immediately after the accident.
2. The Effects of His Brain Injury
🔹 Before the injury Gage was hardworking, responsible, and well-liked. 🔹 After the injury He became impulsive, rude, and irresponsible. He lost self-control , often cursed and made inappropriate remarks. He could not stick to a job or make good long-term decisions.
the frontal lobe. Tell the 3 main theories of foundational physiology?
1. Galvani and the Animal Electricity Theory (1781) A century later, Luigi Galvani made a famous accidental discovery so significant that it even influenced Mary Shelley's well-known novel Frankenstein. In 1781, Galvani was dissecting a frog close to a machine emitting static electricity, when his assistant accidentally touched the frog's leg with a scalpel, causing it to suddenly jump. Fascinated by the incident, he repeated the experiment several times to confirm the link between electrical impulses and movements of the body. He decided to call it animal electricity , believing that the energy resided within the frog itself, because the contractions occurred even when the nerve and muscle were detached from the body. Galvani's work paved the way for future studies on the brain and the electrical impulses. 2. Johannes Muller and the Theory of Specific Nerve Energies (1843) This scientist made a fascinating appraisal during his experimentation. Even when all the nerves carry the same type of message, the information is perceived differently by each individual. These messages running through the nerves are known nowadays as electrical impulses. Based on his many experiments, Johannes Muller decided to write a book called Elements of Physiology. In his work, he explained the relation between stimulus and physiological reactions. One of the examples he described in his book was that stimuli upon the retina and the optic nerve would invariably lead to luminous and visual impressions. An individual's mind can't access objects in natural environment except through the nerves They only perceive what Sensing nerves tell them about the environment
3. Paul Broca and the Findings Related to Speech (1864) Paul Broca, a French doctor and anthropologist, took his part in physiological psychology theories by making an autopsy and examining the brain of a patient named Victor Leborgne. Leborgne was 21 years old, and had suffered a progressive loss of speech but not a loss of mental function. This procedure led Broca to determine that his patient had an injury in the frontal lobe of the central hemisphere. The doctor proceeded with his studies until he found enough evidence to propose a theory stating the relation between the brain and speech, and that the brain area specific to speech production was the left frontal lobe. His results helped psychologists during many years, and even now they are fundamental to understanding certain speech therapies. The path was followed immediately by another French Physiologist, Pierre Fluorens. He started the method of ‘Experimental Ablationʼ, in which he observed the missing function in an animal after a portion of the brain is removed surgically. He has claimed to identify the brain regions responsible for controlling heart rate, breathing, voluntary movements, visual and auditory reflexes. Producing lesions (damaging the structure) at specific brain sites enabled systematic study of loss of function resulting from surgical removal, severing of neural connections, or destruction by chemical or electrical applications. Ablation is the removal of a structure. The vast majority of lesion studies are with laboratory animals (although occasionally, surgeons must remove some brain structure in humans to remove a tumor). The procedures in nonhuman animals are done only after thorough review by Institutional Animal Care and Use Committees IACUCs), which ensure that the work is ethical and pain will be minimized In most cases, however, ablative brain surgery doesn't involve removing brain tissue, but rather destroying tissue and leaving it in place. The lesions it causes are irreversible.
cognitive functions. He also showed that the brain could compensate for damage, supporting the idea of neuroplasticity. Criticism: While Flourensʼ work was foundational, he underestimated the degree of localization in the brain.
Key Differences:
Feature Franz Joseph Gall Jean Pierre Flourens Approach Phrenology, skull analysis Experimental lesion studies View on Localization Strict localization of mental functions Brain functions as a whole Key Discoveries Concept of localized brain functions (but wrongly mapped) Cerebellum = movement, cortex = cognition Criticism Phrenology was pseudoscience Underestimated brain specialization
Impact on Neuroscience
Gall's idea of localization of function led to later discoveries in neuroanatomy. Flourensʼ lesion studies provided the first experimental evidence on brain function. Modern neuroscience supports functional localization but recognizes that the brain has interconnected networks rather than rigidly separated areas. Wilder Graves Penfield: His Contributions
Who was he?
🧠 Wilder Graves Penfield 1891 1976 was an American-Canadian neurosurgeon known for his groundbreaking work in brain surgery and neuroscience.
His Major Contributions
1. Brain Mapping & the Cortical Homunculus
🔹 Penfield mapped different brain areas by stimulating them with electrical probes while patients were awake. 🔹 He created the cortical homunculus , a map showing which parts of the brain control different body parts. 🔹 His findings showed that some areas (like the hands, lips, and face) take up more brain space because they need finer control. 🔹 His brain maps are still used today in neurosurgery!
2. The “Montréal Procedureˮ – Epilepsy Surgery
🔹 With Herbert Jasper , he developed a technique to treat epilepsy. 🔹 This procedure involved: Keeping the patient awake with only local anesthesia. Stimulating brain areas to find the exact spot causing seizures. Carefully removing those nerve cells while avoiding damage to other areas. 🔹 This reduced side effects and became a standard method in epilepsy treatment.
3. The Penfield Dissector (A Special Neurosurgery Tool)
🔹 He invented the Penfield dissector , a tool that helped perform less damaging brain surgery. 🔹 This tool reduced scarring in brain tissues and is still used in neurosurgery today.
4. The Study of Memories & Consciousness
🔹 Penfield discovered that stimulating the temporal lobe could cause patients to recall past memories vividly.
3. Discovery of the Brainʼs Role in Internal Organs
🔹 Hess discovered that the brain, especially the hypothalamus , controls: Heart rate 💓 Blood pressure 🩸 Body temperature 🌡 Digestive system functions 🍽 🔹 His work showed that the brain directly regulates the bodyʼs internal environment (homeostasis). Santiago Ramón y Cajal: His Contributions
Who was he?
🧠 Santiago Ramón y Cajal 1852 1934 was a Spanish neuroscientist who is known as the "Father of Modern Neuroscience." He won the Nobel Prize in 1906 for discovering the structure and function of neurons.
His Major Contributions
1. The Neuron Doctrine (Neurons Are Separate Cells!)
🔹 Before Cajal, scientists thought the brain was made of a continuous network like a web. 🔹 Using a special staining method Golgi stain), Cajal proved that neurons are separate cells that communicate with each other. 🔹 This discovery became the foundation of modern neuroscience.
2. Mapping the Brainʼs Structure
🔹 Cajal drew detailed pictures of neurons and how they connect. 🔹 His drawings showed: Dendrites (receive signals) Axons (send signals)
Synapses (gaps between neurons where communication happens) 🔹 His work helped scientists understand how the brain processes information.
3. The Direction of Nerve Signals (Law of Dynamic
Polarization)
🔹 He discovered that nerve signals travel in one direction : From dendrites → through the cell body → to the axon → to the next neuron. 🔹 This explained how neurons communicate and process information.
4. Neuroplasticity (The Brain Can Change & Adapt!)
🔹 Cajal proposed that the brain is not fixed but can change and grow new connections. 🔹 This idea of neuroplasticity is now used in stroke recovery, learning, and therapy for brain injuries. What is Split-Brain? What does a person with split brain experience? Split-brain refers to a condition in which the two hemispheres of the brain are not connected to each other. This can occur as a result of surgery to remove the divider to prevent epileptic seizures, or as a result of birth defects. A split-brain person can see, feel, or sense things differently. This occurs because the two halves of the brain do not communicate with each other. Therefore, the signals on one side of the body only reach the opposite side of the brain. By contrast, in normal people the brain shares information among both sides. The split-brain person can be seen as having two individuals within one body. As a result, such people may behave in contradictory ways. What is split brain theory? What happens when corpus callosum is cut?
1. What is the Split Brain Theory?
🔹 The brain has two sides (hemispheres) connected by the corpus callosum.
The right hemisphere sees the left image but cannot speak. ✅ Math and Logic Are in the Left Hemisphere : The left hemisphere is better at solving math problems. The right hemisphere was random or inaccurate at multiplication and division. The right hemisphere was slightly better at addition than other math operations. How does the corpus callosum contribute to brain communication, and why is it surgically disconnected in some epilepsy patients?
1. The Role of the Corpus Callosum in Brain
Communication
The brain is divided into two hemispheres (left and right), which work together to control thoughts, actions, and body functions. These hemispheres communicate through a thick bundle of nerve fibers called the corpus callosum. 🔹 In normal brains , the corpus callosum allows information to flow freely and quickly between the two hemispheres. 🔹 However, in some individuals with severe epilepsy , this connection can cause serious problems.
2. How Epileptic Seizures Spread Between Brain
Hemispheres
🔹 Epilepsy is a neurological disorder that causes abnormal electrical activity in the brain. 🔹 In many cases, seizures start in one hemisphere but quickly spread to the other via the corpus callosum. 🔹 This rapid, uncontrolled communication between the hemispheres results in severe and frequent epileptic seizures that can be debilitating.
👉 Example: If a seizure starts in the left hemisphere, it can quickly spread to the right hemisphere, making the seizure more intense and harder to control.
3. The Split-Brain Operation: Surgical
Disconnection of the Corpus Callosum
To help severe epilepsy patients , neurosurgeons developed the split-brain procedure (also called a corpus callosotomy ), which cuts the corpus callosum , preventing seizures from spreading between hemispheres. 🔹 How It Works: The surgery disconnects the two hemispheres but does not damage the rest of the brain. Each hemisphere continues to function independently and controls the opposite side of the body. Seizures that start in one hemisphere can no longer spread , making them less severe and more manageable. 🔹 Benefits of the Surgery: ✅ Dramatically reduces the frequency and intensity of seizures. ✅ Improves the quality of life for epilepsy patients. ✅ Preserves cognitive and motor function , allowing patients to live normal lives. 🔹 Limitations of the Surgery: ❌ Patients may experience mild memory problems or difficulty naming objects. ❌ Each hemisphere now works independently , leading to unusual effects (e.g., one hand acting differently from the other). ❌ Split-brain symptoms can occur, affecting coordination and perception. What was the Research done by Roger Sperry? Research by Roger Sperry 1966
🔹 Roger Sperryʼs Early Split-Brain Research (1966)
Gazzaniga showed split-brain patients two different images—one on the left and one on the right. When asked what they saw, they only named the object seen by the right eye because speech is controlled by the left hemisphere. ✅ The Right Hemisphere Understands but Cannot Speak If an object appeared on the left side (processed by the right hemisphere), patients couldnʼt name it but could draw it with their left hand. ✅ Mathematical Ability is Stronger in the Left Hemisphere Patients were given math problems, and the left hemisphere solved them much more accurately than the right hemisphere. ✅ The Two Hemispheres Can Have Conflicting Responses In some cases, the left and right hands would act independently , as if controlled by two separate minds. Example: A patient buttoning a shirt with one hand and unbuttoning it with the other! 🔬 Impact of Gazzanigaʼs Work: Gazzanigaʼs research proved that the brain can function with two separate, independent minds after a split-brain operation. His work helped us understand the importance of communication between brain hemispheres. What is the significance of Split Brain Research? ✅ Confirmed the specialization of brain hemispheres (left = language/math, right = emotion/spatial). ✅ Proved that the corpus callosum is essential for brain communication. ✅ Improved epilepsy treatment and led to better understanding of brain disorders. ✅ Influenced modern neuroscience by showing how brain regions control behavior and cognition. Explanation of the Exception in Cross-Sensory Representation Using the Olfactory System
1. Understanding Cross-Sensory Representation in the Brain
Normally, sensory information from one side of the body is processed by the opposite hemisphere of the brain. Example: The left visual field is processed by the right hemisphere , and vice versa. The left side of the body is controlled by the right hemisphere , and vice versa. However, the olfactory system (sense of smell) is an exception to this general rule. Unlike vision, touch, or motor control, olfactory information does not cross over to the opposite hemisphere. Instead, the right nostril sends smell information to the right hemisphere , and the left nostril sends it to the left hemisphere.
2. Explanation of the Image (Split-Brain Experiment with
Olfactory Input)
This image depicts an experiment on a split-brain patient —a person who has had their corpus callosum severed to control severe epilepsy.
What Happens in the Experiment?
A rose's scent is presented only to the right nostril. Since the olfactory system does not cross hemispheres , the right hemisphere processes the smell of the rose. The left nostril is plugged , so no smell reaches the left hemisphere. The person denies smelling anything. Why? In a normal brain, the right hemisphere would send this information to the left hemisphere via the corpus callosum , allowing the person to verbally describe what they smelled.
