This unit explores the structure and function of the human brain, covering methods used to study brain activity and damage, and detailing the major divisions and specific regions of the brain. Students should be prepared to identify the roles of various brain parts and distinguish between related concepts like Broca's and Wernicke's aphasia, and gray versus white matter.
Methods of Studying the Brain
Explores techniques and case studies used to understand brain function.
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Phineas Gage
A railroad worker who survived an accident where a steel rod penetrated his brain, damaging his limbic system.
He was able to walk and talk normally but had trouble controlling his emotions. This case study helped scientists learn that specific brain areas play specific roles, particularly regarding emotions.
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Lesion Studies
Doctors or researchers destroy specific parts of the brain to gain insight into their different functions.
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Split Brain Procedures
A surgical technique that cuts the corpus callosum to treat severe epilepsy, preventing communication between the brain's hemispheres (see Split Brain Procedure and Contralateral Organization).
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Autopsy
The dissection and examination of a corpse to determine the cause, mode, and manner of death, allowing for post-mortem brain analysis.
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Technology (fMRI)
fMRI (functional Magnetic Resonance Imaging) is a technology used to study brain activity by detecting changes associated with blood flow.
Split Brain Procedure and Contralateral Organization
Details the split-brain procedure and the concept of contralateral hemispheric organization.
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Split Brain Procedure
Involves surgically cutting the corpus callosum, the main bundle of neuronal fibres connecting the two brain hemispheres, primarily to treat severe epilepsy.
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Contralateral Hemispheric Organization
The principle that the left field of view is processed by the right hemisphere, and the right field of view is processed by the left hemisphere.
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Visual Input to Right Field
A word is flashed briefly to the right field of view, sending information to the left hemisphere.
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Left Hemisphere Processing
The left hemisphere is dominant for verbal processing, allowing the patient to verbally identify what they saw (e.g., 'FACE').
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Visual Input to Left Field
A word is flashed briefly to the left field of view, sending information to the right hemisphere.
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Right Hemisphere Processing
The right hemisphere processes the image but, due to the severed corpus callosum, cannot share this information with the left hemisphere for verbalization. The patient is unable to say what they saw but can draw it.
| Left Hemisphere | Right Hemisphere | |
|---|---|---|
| Primary Role | Dominant for verbal processing and language | Processes simple spatial reasoning and visual-spatial tasks |
| Visual Input | Receives input from the right field of view | Receives input from the left field of view |
| Motor Control | Controls the right side of the body | Controls the left side of the body |
Major Brain Divisions
Overview of the three main evolutionary divisions of the brain.
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Hindbrain
The oldest part of the brain from an evolutionary standpoint, vital for survival.
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Midbrain
Involved in processing visual and auditory information, motor control, and integrating sensory and motor pathways.
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Forebrain
Responsible for complex thoughts and higher-level cognitive functions.
Hindbrain Structures
Details the structures within the hindbrain and their vital functions.
Hindbrain
The oldest part of the brain, vital for survival, controlling basic life functions.
Spinal Cord
Connects the brain to the rest of the nervous system and the body.
Brainstem
Comprises the Medulla Oblongata, Pons, and Reticular Activating System.
Medulla Oblongata
Regulates the cardiovascular system and respiratory system (autonomic functions).
Pons
A bridge between different areas of the nervous system (from Medulla to Cerebellum); involved in movement, sleep, and dreaming.
Reticular Activating System (Reticular formation)
Involved in regulating arousal, alertness, and sleep; sends sensory input to the Thalamus.
Cerebellum
Coordinates voluntary movements, maintains posture, balance, and refines motor skills.
- The Hindbrain collectively manages autonomic functions, motor control, sleep cycle, and reflexes.
- The Brainstem is crucial for basic life support, while the Cerebellum refines movement.
Midbrain
Describes the midbrain's role in sensory processing and motor control.
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Midbrain
A central brain region involved in processing visual information and auditory information, motor control, and the integration of sensory pathways and motor pathways.
Limbic System
Covers the limbic system components crucial for emotions, learning, memory, and basic drives.
The Limbic System is a collection of brain structures critical for Emotions, Learning, Memory, and Basic Drives. Key components include the Thalamus, Hypothalamus, Pituitary Gland, Hippocampus, and Amygdala. Other structures like the Corpus callosum, Cingulate gyrus, Basal ganglia, Cerebrum, and Pineal gland are also associated or depicted in diagrams of the limbic system.
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Thalamus (Relay Station)
Relays all incoming sensory information (except smell) to the appropriate areas of the cerebral cortex for processing. For example, visual input from the Eye goes to the Thalamus then to the Occipital Lobe.
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Hypothalamus (Instinct)
Maintains homeostasis by keeping the body balanced and controlling essential Basic Drives such as thirst, hunger, temperature, and sex.
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Pituitary Gland (Master Gland)
Produces and releases hormones that regulate many bodily functions and control other endocrine glands throughout the body.
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Hippocampus
Crucial for Learning and Memory Formation. It's associated with the 'Method of Loci,' a memory enhancement strategy using visualizations of familiar spatial environments.
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Amygdala
Involved in Emotional reactions, particularly anxiety, anger, and aggression.
Cerebrum and Hemispheres
Introduces the cerebrum, its lobes, hemispheres, and gray/white matter.
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Cerebrum (Forebrain)
The largest part of the brain, responsible for Complex Thoughts and higher cognitive functions. It is divided into 4 Lobes: Frontal, Parietal, Temporal, and Occipital.
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2 Hemispheres
The cerebrum is divided into two distinct hemispheres, the Left Hemisphere and the Right Hemisphere, which specialize in different functions.
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Corpus Callosum
A thick band of nerve fibers that serves as the primary bridge between the 2 hemispheres, allowing them to communicate.
| Left Hemisphere | Right Hemisphere | |
|---|---|---|
| Primary Function | Dominant for language (production and comprehension) | Specializes in simple spatial reasoning and visual-spatial tasks |
| Control | Controls the right side of the body | Controls the left side of the body |
| Gray Matter (Cerebral Cortex) | White Matter | |
|---|---|---|
| Composition | Mostly neuronal cell bodies | Mostly heavily myelinated axons |
| Function | Processes and transmits information; controls movement, memory, and emotion | Connects brain regions to help with learning, attention, and motor control |
| Development | Fully develops in your 20s | Peaks in middle age |
Frontal Lobe
Details the frontal lobe's functions, including higher-level thinking, motor control, and language production.
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Frontal Lobe
Located at the front of the brain, responsible for higher level of thinking and executive functions.
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Prefrontal Cortex
The very front part of the frontal lobe, crucial for foresight, judgment, complex thoughts, and language.
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Motor Cortex
Located at the rear of the frontal lobe, responsible for planning and executing voluntary movements. It exhibits Contralateral hemispheric organization, meaning the left hemisphere controls the right side of the body, and vice versa.
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Motor Homunculus
A distorted map representing the different body parts associated with specific parts of the Motor Cortex, with areas requiring finer control (like hands and face) having larger representations.
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Broca's Area
Located in the Left Hemisphere (typically) in front of the Motor Cortex, it is crucial for language production, specifically controlling the muscles involved in speech.
Broca's Aphasia
Damage to Broca's Area results in Broca's Aphasia, a condition characterized by the loss in ability to produce language (difficulty speaking fluently), though comprehension may remain relatively intact.
Parietal Lobe
Covers the parietal lobe's role in sensory processing and spatial orientation.
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Parietal Lobe
Brain lobe responsible for processing sensory information (e.g., touch, pain, temperature), spatial orientation, and organizing information.
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Somatosensory Cortex
A strip of cortex in the parietal lobe that processes sensory input from the body. It operates contralaterally, meaning the left hemisphere processes sensations from the right side of the body, and vice versa.
Temporal Lobe
Explores the temporal lobe's functions in auditory processing, language, and memory.
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Temporal Lobe
Brain lobe involved in processing auditory information, linguistic information, recognizing faces (and shapes), and memory.
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Auditory Cortex
The primary area within the temporal lobe responsible for processing sound.
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Wernike's Area
Located in the left temporal lobe; crucial for creating and understanding meaningful speech. Damage to this area results in Wernike's Aphasia.
| Broca's Area | Wernike's Area | |
|---|---|---|
| Location | Left Frontal Lobe (see Frontal Lobe) | Left Temporal Lobe |
| Primary Function | Responsible for making speeches (language production) | Responsible for understanding speech (language comprehension) |
| Aphasia (Damage) | Broca's Aphasia: Loss of ability to produce language (see Frontal Lobe) | Wernike's Aphasia: Disorder affecting the ability to create and understand meaningful speech |
Occipital Lobe
Details the occipital lobe's role in visual processing and object recognition.
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Occipital Lobe
Brain lobe primarily responsible for visual information processing. Also involved in recognizing objects (in conjunction with the Temporal Lobe) and understanding spatial relationships, perceiving depth, and movement (in conjunction with the Parietal Lobe).
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Primary Visual Cortex
The area within the occipital lobe that directly receives visual input from the eyes.