VISION--HOW WE SEE THINGS

VISION--HOW WE SEE THINGS

Vision is a complex, two-part process that begins when your eyes detect light and ends when your brain constructs the final, meaningful image. It involves a precise pathway from the outside world to the visual cortex.

👁️ Step 1: In the Eye (Capturing and Focusing Light)

Light Entry and Bending: Light rays reflected from an object first pass through the transparent, dome-shaped cornea, which performs the majority of the light-bending (refraction) needed for focusing.
Light Regulation: The light then travels through the pupil, an opening whose size is controlled by the iris (the colored part of the eye). The iris constricts the pupil in bright light and dilates it in low light, much like a camera aperture.
Final Focusing: The light passes through the lens, a clear structure that changes shape (a process called accommodation) to fine-tune the focus, ensuring the image lands sharply on the retina. Due to this process, the image projected onto the retina is upside down and reversed.
Signal Conversion (Retina): The focused light hits the retina, the light-sensitive tissue at the back of the eye. This layer contains specialized photoreceptors:
- Rods: Handle vision in dim light (low resolution, black and white).
- Cones: Handle color vision and fine detail (require bright light).
- These cells convert the light energy (photons) into electrical signals (neural impulses).

🧠 Step 2: To the Brain (Transmission and Interpretation)

Optic Nerve Transmission: The electrical signals are collected by the optic nerve (Cranial Nerve II), which carries the information from the back of the eye toward the brain.
The Crossover (Optic Chiasm): The optic nerves from both eyes meet at the optic chiasm. Here, the nerve fibers from the nasal (inner) half of each retina cross over to the opposite side of the brain. This ensures that the right visual field (everything you see to your right) is processed by the left hemisphere, and the left visual field is processed by the right hemisphere.
Relaying Information: Most signals make a stop at the Lateral Geniculate Nucleus (LGN), a major relay center in the thalamus.
Cortical Processing: The signals are finally sent to the Primary Visual Cortex (V1), which is located in the Occipital Lobe at the very back of the brain. This is where sight becomes vision. The brain performs several crucial processing tasks:
- It flips the inverted image from the retina, so you perceive the world right-side up.
- It combines the two slightly different signals from your eyes to create a single, continuous image with depth perception (3D vision).
- The information is then routed into specialized pathways for further processing: the "What" pathway (for recognizing objects, faces, and color) and the "Where" pathway (for determining motion and spatial location).

Diagram of Brain

Information from our eyes goes to areas at the very back of the brain. We've all seen cartoons where the rabbit gets hit on the head and the rabbit sees stars. This can actually happen in human beings (trust me, not a good thing to do at home!). If you take a hard enough blow to the back of the head, this brain area bangs against back of your skull. This stimulates it and you can see stars and flashing lights. Remember those two hemispheres? Each hemisphere processes half the visual information. Visual information that we see on the left gets processed by the right hemisphere. Information on the right gets processed by the left hemisphere. Remember, wires that bring in information to the brain are "crossed"--visual information from the left goes to the right brain.

Diagram of Brain; VIDEO

Diagram of Brain: SKIN SENSATION

SKIN SENSATION

Here is a diagram of the brain highlighting the area responsible for skin sensation (touch, temperature, pain, pressure)—this area is called the Somatosensory Cortex.

🖐️ The Somatosensory Cortex

The Somatosensory Cortex is located in the Parietal Lobe (the area shaded in the diagram), specifically in the postcentral gyrus (the ridge right behind the central sulcus).

Function

This area is the main receiving area for somatosensory information from the entire body, which includes:

Touch and pressure
Pain and temperature
Proprioception (sense of body position)

Somatosensory Homunculus

The cortex is organized in a unique map of the body called the somatosensory homunculus. The representation of body parts is distorted, with areas requiring fine-tuned sensation (like the lips, hands, and face) taking up a much larger portion of the cortex than areas with less sensitivity (like the trunk or back).

Diagram of Brain: SKIN SENSATION

If something lands on my left hand, this information will be transmitted to the right side of my brain. It goes to the area of the brain next to the area that deals with movement. The tactile area of the brain deals with physical sensation. Movement and feeling are closely related, so it makes sense that they are next to each other in the brain. Because movement and tactile areas are located close to each other, it is not uncommon for people with a brain injuries to lose both movement and feeling in parts of their body. Remember--tactile information from the left side of the body goes to the right brain, just like movement and vision.

VIDEO

DIAGRAM OF BRAIN

Dimensions and Sizes

Average dimensions of the adult brain: Width = 140 mm/5.5 in, Length = 167 mm/6.5 in, Height = 93 mm/3.6 in.
How much does human brain weigh? At birth our brains weigh and average of 350-400g (about 4/5 lbs), as adults the brain averages 1300-1400g (about 3 lbs).
If Stretched out the cerebral cortex would be 0.23 sq. m(2.5sq.ft), the area of a night table.
Total surface area of the cerebral cortex is 2,500 cm2 or 2.69 sq.ft.

Composition

The composition of the brain = 77-78% water, 10-12% lipids, 8% protein, 1% carbs, 2% soluble organics, 1% inorganic salt.
The breakdown of intracranial contents by volume (1,700 ml, 100%): brain = 1,400 ml (80%); blood = 150 ml (10%); cerebrospinal fluid = 150 ml (10%).
The cerebellum contains half of all the neurons in the brain but comprises only 10% of the brain.
The cerebral cortex is about 85% of the brain.
Percentage of total cerebral cortex volume = frontal lobe 41%, temporal lobe 22%, parietal lobe 19%, occipital lobe 18%.
There are about 100 billion neurons in the human brain, the same number of stars in our galaxy.
The left hemisphere of the brain has 186 million more neurons than the right hemisphere.
750-1000ml of blood flow through the brain every minute or about 3 full soda cans.
In that minute the brain will consume 46cm3 (1/5 cups) of oxygen from that blood.
Of that oxygen consumed, 6% will be used by the brain's white matter and 94% by the grey matter.

Times

The brain can stay alive for 4 to 6 minutes without oxygen. After that cells begin die.
The slowest speed at which information travels between neurons is 416 km/h or 260 mph, thats as "slow" as todays supercar's top speed (the Bugatti EB 16.4 Veyron clocked at 253 mph).
10 seconds is the amount of time until unconsciousness after the loss of blood supply to the brain.
Time until reflex loss after loss of blood supply to the brain, 40-110 seconds.
During early pregnancy the rate of neuron growth is 250,000 neurons a minute.

Other Fun Facts About The Human Brain

Results from cognitive tests show 30% of 80-year-olds perform as well as young adults.
Your brain is about 2% of your total body weight but uses 20% of your body's energy.
The energy used by the brain is enough to light a 25 watt bulb.
More electrical impulses are generated in one day by a single human brain than by all the telephones in the world.
How much does human brain think? 70,000 is the number of thoughts that it is estimated the human brain produces on an average day.
After age 30, the brain shrinks a quarter of a percent (0.25%) in mass each year.
Albert Einsteins brain weighed 1,230 grams (2.71 lbs), significantly less then the human average of 1,300g to 1,400g (3 lbs).
Each year Americans consume 50 billion aspirin tablets or 15.5 million tons.
89.06 is the percentage of people who report normally writing with their right hand, 10.6% with their left and 0.34% with either hand.

Diagram of Brain

DIAGRAM OF BRAIN: BRAINSTEM

DIAGRAM OF BRAIN: BRAINSTEM

🧩 THE BRAINSTEM

The Brainstem is the lowest part of the brain, connecting the cerebrum (the upper brain) to the spinal cord.
Though small in size, it controls many essential life functions — including breathing, heartbeat, and blood pressure — that keep you alive every second.

It acts like the brain’s “autopilot system”, managing all the automatic processes your body performs without you having to think about them.

📍 LOCATION

The brainstem sits at the base of the brain, just above the spinal cord and below the cerebrum.
It connects the brain to the spinal cord, forming a bridge between the brain and the rest of the body.
It is made up of three main parts:
1. Midbrain
2. Pons
3. Medulla Oblongata

⚙️ PARTS AND FUNCTIONS

1. Midbrain (Mesencephalon)

The uppermost part of the brainstem.
Controls eye movements, hearing, visual processing, and reflexes (like turning your head toward a sudden sound).
Plays a role in maintaining alertness and motor control.

2. Pons

The middle section of the brainstem, located below the midbrain.
Acts as a bridge between the cerebrum and cerebellum.
Helps regulate sleep, respiration (breathing), swallowing, facial expressions, and eye movement.
It also assists in transmitting sensory messages to higher parts of the brain.

3. Medulla Oblongata

The lowest part of the brainstem, connecting directly to the spinal cord.
Controls vital autonomic functions that are necessary for life:
Because of these critical roles, damage to the medulla can be fatal.

💡 MAIN FUNCTIONS OF THE BRAINSTEM

Function	Description
Autonomic Control	Regulates breathing, heart rate, and blood pressure automatically.
Reflex Actions	Controls reflexes like blinking, coughing, and swallowing.
Motor and Sensory Pathways	Acts as a relay center, sending messages between the brain and the body.
Sleep and Arousal	Helps maintain alertness, wakefulness, and the sleep cycle.
Balance and Coordination	Works with the cerebellum to maintain posture and balance.

⚠️ DAMAGE OR DISORDERS OF THE BRAINSTEM

Injury or disease affecting the brainstem can cause serious problems, such as:

Difficulty breathing or irregular heartbeat
Loss of consciousness or coma
Trouble swallowing or speaking
Loss of balance and coordination
Paralysis or loss of sensation

Because the brainstem controls basic life functions, any damage can be life-threatening.

❤️ IN SUMMARY

The Brainstem is the life-support center of the human body.
It connects the brain and spinal cord, relays vital information, and controls automatic functions like breathing and heartbeat.
Without the brainstem, survival would not be possible.

Brainstem - The lower extension of the brain where it connects to the spinal cord. Neurological functions located in the brainstem include those necessary for survival (breathing, digestion, heart rate, blood pressure) and for arousal (being awake and alert).

Most of the cranial nerves come from the brainstem. The brainstem is the pathway for all fiber tracts passing up and down from peripheral nerves and spinal cord to the highest parts of the brain.

Diagram of brainVIDEO

FRONTAL LOBES--Planning, Organizing, Controlling

FRONTAL LOBES--Planning, Organizing, Controlling

🧩 THE FRONTAL LOBES

The frontal lobes are the largest lobes of the brain and are located at the front part of each cerebral hemisphere, just behind the forehead. They are often called the “control panel” or “command center” of the brain because they are responsible for complex thinking, planning, decision-making, emotions, and voluntary movement.

📍 LOCATION

Found at the front of the brain, directly behind the forehead.
They are part of the cerebrum, the brain’s largest region.
The central sulcus (a deep groove) separates the frontal lobes from the parietal lobes, while the lateral sulcus divides them from the temporal lobes.

⚙️ MAIN FUNCTIONS OF THE FRONTAL LOBES

The frontal lobes are involved in higher-level brain functions that make us uniquely human — our ability to think, plan, and behave socially and emotionally.

Here’s what they do:

Motor Function (Movement Control)
- The primary motor cortex, located in the rear part of the frontal lobe, controls voluntary muscle movement (like walking, talking, or writing).
- Each side of the frontal lobe controls movement on the opposite side of the body.
Planning and Decision-Making
- Helps you set goals, organize thoughts, and make choices.
- Used in reasoning, judgment, and problem-solving — critical for everyday decisions.
Speech and Language Production
- The Broca’s area (in the left frontal lobe for most people) controls speech production.
- Damage here can cause Broca’s aphasia, leading to difficulty speaking or forming sentences.
Emotional Regulation and Behavior
- The prefrontal cortex helps manage emotions, social behavior, and impulse control.
- It helps you act appropriately in different situations (e.g., staying calm under stress).
Memory and Attention
- Involved in working memory — the ability to hold and use information temporarily (like remembering a phone number).
- Helps maintain focus and attention on tasks.
Personality and Creativity
- The frontal lobes shape your personality traits, motivation, and moral values.
- It’s where creative ideas, initiative, and individuality come from.

⚠️ EFFECTS OF DAMAGE TO THE FRONTAL LOBES

Injury or damage to this region can cause noticeable changes in behavior, thinking, and movement, such as:

Poor judgment or impulse control
Difficulty planning or concentrating
Changes in personality or mood
Trouble speaking or forming sentences
Loss of coordination or weakness on one side of the body

For example, famous patient Phineas Gage (1848) survived a severe frontal lobe injury but experienced a dramatic personality change — proving how critical this area is for personality and behavior.

💡 IN SUMMARY

Function	Description
Movement Control	Directs voluntary muscle actions.
Thinking & Planning	Handles reasoning, problem-solving, and decision-making.
Speech Production	Controls speech via Broca’s area.
Emotion & Behavior	Regulates mood, impulse, and social interaction.
Memory & Focus	Supports working memory and concentration.
Personality	Shapes identity, creativity, and motivation.

🧠 The frontal lobes make you who you are — the seat of your personality, intelligence, and control over your actions. They help you think ahead, speak clearly, behave responsibly, and live meaningfully.

Diagram of Brain

The biggest and most advanced part of the brain is the frontal lobe. (It's called the frontal lobe because it's in the front part of brain.) One job of the frontal lobe is planning. You have probably heard of "frontal lobotomies." At the turn of the century, this surgery was done on people who were very violent or who were in a psychiatric hospital because they were very agitated. Doctors used surgery to damage this area of the brain.

Following this surgery, people became very passive and less violent. At first, scientists saw this as a great thing. Neurosurgery could stop behavioral problems such as violence. The problem was that the patients stopped doing a lot of other things. They didn't take care of themselves and they stopped many activities of daily living.

They basically sat there. In head injury, individuals with frontal lobe impairment seem to lack motivation and have difficulty doing any task that requires multiple steps (e.g., fixing a car or planning a meal). They have problems with planning.

The frontal lobe is also involved in organizing. For a lot of activities, we need to do step A, then step B, then step C. We have to do things in order. That's what the frontal lobes help us do. When the frontal lobe is injured, there is a breakdown in the ability to sequence and organize. A common example is people who cook and leave out a step in the sequence.

They forget to add an important ingredient or they don't turn the stove off. I've met a lot of patients who've burned or melted a lot of pans.

Additionally, the frontal lobes also play a very important role in controlling emotions. Deep in the middle of the brain are sections that control emotions. They're very primitive emotions that deal with hunger, aggression, and sexual drive.

These areas send messages to other parts of the brain to DO SOMETHING. If you're mad, hit something or someone. If you're hungry, grab something and eat it. The frontal lobes "manage" emotions. In general, the frontal lobe has a NO or STOP function. If your emotions tell you to punch your boss, it's the frontal lobes that say "STOP or you are going to lose your job." People have often said to me "a little thing will set me off and I'm really mad." The frontal lobes failed to stop or turn off the emotional system.

On the other hand, we have talked about how the frontal lobes plan activities. The frontal lobes may fail to plan for some types of emotion. For example, sexual interest involves some level of planning or preparation. Without this planning, there is a lack of sexual interest.

A lack of planning can also affect the expression of anger. I've had some family members say "You know, the head injury actually improved him, he's not such a hot-head anymore." If you listen very carefully, you're also going to hear "he's not as motivated anymore." Remember, the frontal lobe plans activities as well as controls emotions.

Diagram of Brain Video

UNDERSTANDING HOW THE BRAIN WORKS

UNDERSTANDING HOW THE BRAIN WORKS

🧠 UNDERSTANDING HOW THE BRAIN WORKS

The human brain is the control center of the body. It manages everything we do — from breathing and heartbeat to thinking, emotions, memory, movement, and imagination. It communicates with the rest of the body through the nervous system, using billions of specialized cells called neurons.

⚙️ 1. Structure of the Brain

The brain is divided into three major parts, each responsible for specific functions:

🧩 A. The Cerebrum

Largest part of the brain, divided into the right and left hemispheres.
Responsible for thinking, memory, emotions, movement, and sensory processing.
Covered by a wrinkled layer called the cerebral cortex, which helps with advanced thought and reasoning.

Each hemisphere is divided into four lobes:

Frontal Lobe – controls decision-making, problem-solving, movement, and personality.
Parietal Lobe – processes touch, pressure, pain, and spatial awareness.
Temporal Lobe – handles hearing, memory, and language comprehension.
Occipital Lobe – responsible for vision and interpreting what we see.

🧠 B. The Cerebellum

Located at the back of the brain, below the cerebrum.
Coordinates balance, posture, and muscle movement.
Ensures that all movements are smooth and accurate.

🌡️ C. The Brainstem

Connects the brain to the spinal cord.
Controls vital automatic functions like breathing, heart rate, blood pressure, and digestion.
Has three parts: midbrain, pons, and medulla oblongata.

🧬 2. How the Brain Communicates

The brain communicates through a vast network of neurons — about 86 billion of them!

Each neuron sends and receives messages using electrical and chemical signals. These signals travel through tiny gaps called synapses, allowing the brain to:

Interpret sensations (like pain or sound)
Control muscle movements
Form thoughts, memories, and emotions

💡 Think of it as an ultra-fast communication network — your brain’s version of Wi-Fi!

❤️ 3. The Limbic System: The Emotional Brain

Located deep within the cerebrum, the limbic system controls emotions, motivation, and memory.
It includes:

Amygdala – regulates fear, anger, and emotional responses
Hippocampus – stores and retrieves memories
Thalamus – relays sensory information
Hypothalamus – controls hunger, thirst, temperature, and hormones

This system helps explain why emotions strongly affect memory and behavior.

🌈 4. The Brain and Body Connection

The nervous system has two main parts:

Central Nervous System (CNS) – brain and spinal cord
Peripheral Nervous System (PNS) – nerves throughout the body

Together, they send and receive signals that allow you to:

Move your muscles
Feel sensations (heat, pain, pressure)
Think and remember
React to danger
Experience joy, sadness, or excitement

⚡ 5. The Brain’s Amazing Abilities

Neuroplasticity: The brain can reorganize and adapt by forming new connections — even after injury or trauma.
Memory Storage: Information is stored in different parts of the brain; short-term and long-term memories are managed separately.
Learning: Repeated experiences strengthen neural connections — the basis for learning new skills.

🧘 6. Keeping the Brain Healthy

To keep your brain sharp and strong:

🥦 Eat a balanced diet (rich in omega-3s, fruits, and vegetables)
💤 Get enough sleep
🏃 Exercise regularly (improves blood flow and memory)
🧩 Challenge your mind (puzzles, reading, learning new things)
😊 Manage stress and stay socially connected

💡 In Summary

The brain is your body’s command center — controlling thoughts, feelings, movements, and every function that keeps you alive.
It works through a complex system of neurons and lobes, balancing emotion, reason, and reflex.
Taking care of your brain means caring for your entire self — body, mind, and spirit.

OTHER SOURCES

The human brain weighs only three pounds and is estimated to have more or less 100 billion cells. It is hard to get a handle on a number that large (or connections that small).

Let's try to get an understanding of this complexity by comparing it with something humans have created--the entire phone system for the planet earth .

If we took all the phones in the world and all the wires (there are over four billion people on the planet), the number of connections and the trillions of messages per day would NOT equal the complexity or activity of a single human brain.

Now let's take a "small problem"--break every phone in Los Angeles and cut every wire in the state.

How long would it take for the entire state (about 16 million people) to get phone service back?

A week, a month, or several years?

If you guessed several years, you are now beginning to see the complexity of recovering from a head injury.

In the example LA residents would be without phone service while the rest of the world had phone service that worked fine.

This is also true with people who have a head injury.

Some parts of the brain will work fine while others are in need of repair or are slowly being reconnected.

Diagram of Brain: thalamus.

The Thalamus

Diagram of Brain...

The Thalamus

🧠 The Thalamus

The Thalamus is a small but vital structure located deep within the center of the brain, sitting just above the brainstem and beneath the cerebral cortex. It acts as the brain’s relay station — processing and transmitting information between the body and different areas of the brain.

🔍 Location

Found in the diencephalon, near the center of the brain.
Lies between the cerebral cortex (which controls thought and perception) and the midbrain (which handles movement and sensory input).
Each hemisphere of the brain has its own thalamus.

⚙️ Main Functions of the Thalamus

Sensory Relay Center
- The thalamus receives sensory information (like touch, pain, temperature, vision, and sound) and sends it to the appropriate part of the cerebral cortex for processing.
- Example: Visual signals go to the occipital lobe, sound to the temporal lobe, and touch to the parietal lobe.
Motor Control
- Works with the basal ganglia and cerebellum to help coordinate movement.
Regulation of Consciousness and Alertness
- The thalamus helps maintain wakefulness, attention, and awareness.
- It filters incoming sensory signals, letting the brain focus on what’s important.
Emotion and Memory
- Through its connection with the limbic system, the thalamus plays a role in emotions, motivation, and memory formation.

⚠️ Damage or Disorders

If the thalamus is injured or affected by disease, symptoms may include:

Loss of sensation or numbness
Movement disorders
Difficulty with memory or attention
Changes in consciousness or alertness
Pain syndromes, such as thalamic pain after a stroke

💡 In Summary

The Thalamus acts as the brain’s central hub — receiving sensory data, sorting it, and sending it to the right part of the brain.
It helps control how we feel, move, sense, and stay alert, making it one of the most essential structures for overall brain function.

The thalamus is sort of the hub for all sensory information in the brain, sort of like the mailroom in a large office building. Almost all signals that go into or come out of the brain pass through the thalamus. While the thalamus has long been thought to be just a relay station, new research suggests that it is much more complicated. For instance it is in some way related to sleep and wakefulness. Finally, the hypothalamus is the brain part that controls many hormones and regulates other important bodily functions including hunger, thirst, body temperature, and even breast feeding.

Diagram of brain....Video