Frontal lobe: Manages planning and organizing and controls your limbs
Temporal lobe: Is where language and recognition memory occurs (contains the hippocampus and amygdala)
Parietal lobe: Manages sensation and perception, spatial awareness, and navigational skills
Occipital lobe: Is the center of visual perception; organizes information to be sent to other brain areas for processing
Keeps you breathing and your heart beating—without you having to think about it (involuntary)
Plays a major role in learning and memory
Is the center for emotions (especially fear) and motivation
Coordinates and regulates muscles
Relays sensory information to the cerebral cortex
Frontal lobe: The frontal lobe stores working memory (a system for storing multiple bits of knowledge temporarily in the forefront of your mind while performing a task or solving a problem).
Temporal lobe: The temporal lobe regulates recognition memory (recognizing if a person or object is familiar, plus recalling who or what it is).
The hippocampus is involved in memory, especially mental maps of places. It also works on memory consolidation, the slow process by which memories are converted from short-term to long-term memory.
The amygdala encodes emotional learning into memory, such as fear conditioning (learning to associate something with a negative event so you can try to avoid it later).
Memory research has shown that the more intense your emotions are during an event, the greater the chance that you’ll remember the event.
The cerebellum controls balance for walking and standing and other complex motor functions, such as learning to play a musical instrument.
You’re aware of sounds, and you can remember and learn from what you hear.
You can retrieve old memories (names, places, info) to help you navigate life. You can make new memories.
You can feel pain, which may prompt you to take action to ease this negative feeling. You can also remember what you learn about the pain’s cause, so you can try to avoid that pain in the future. During a medical procedure, if an anesthesiologist or dentist gives you a local or regional anesthetic, it will block pain while you remain conscious.
We know that general anesthetics seem to cause specific changes in brain rhythms, but there is much that we don’t know. What is consciousness? What neural activity defines it? What neural activity defines the lack of consciousness? This is an important question because we don’t want patients to be conscious during surgeries. Another important question is: What is pain? What neural activity can be used to define pain? Is there a biomarker for pain?
I work on understanding how pain is perceived and regulated by the brain. Specifically, we are looking at how different regions in the brain are connected in the presence of a painful stimulus, and how chronic pain alters the normal processing of a painful stimulus. Our lab also works on translating what we learn into treatments for chronic pain.
Hippocampus & Cortex
The brain stem helps control the transitions between waking and sleeping while continuing to maintain involuntary heartbeat and breathing.
During REM sleep, the brain stem sends signals to relax muscles needed for limb movements, so that we don’t act out our dreams.
The hippocampus transfers new memories to the cortex, which replays the memories to consolidate them into long-term memory.
The amygdala becomes increasingly active during REM sleep.
Dreaming’s exact purpose isn’t known, but it may help you process your emotions.
During most stages of sleep, the thalamus (which relays sensory information to the cerebral cortex) reduces its activity so you can tune out your surroundings.
But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill your dreams.
As you sleep, you cycle through a few different stages several times per night.
Your brain ignores most sounds, but loud sounds are likely to wake you from sleep, especially sounds that might indicate danger.
Sleep is essential for transferring recent memories into long-term memory. That’s why it’s helpful to get a good night’s sleep after studying for a test.
Pain can disrupt sleep, and poor sleep can make it harder for the body to deal with pain. Like much about the brain, the relationship between pain and sleep isn’t fully understood, and scientists continue to investigate.
The brain is a big collection of highly interconnected regions that are like electrical circuits. These circuits naturally produce rhythms. The brain uses these rhythms (its brain waves) to control communications among its many regions. Anesthesia drugs take over these rhythms and thereby block communication between brain regions. Loss of communication between brain regions is one of the ways anesthesia drugs produce unconsciousness.
As an anesthesiologist and an anesthesiology researcher, I want to develop perfectly controllable anesthesia techniques so that when patients undergo surgery, they receive only the amount of anesthesia they need, no more and no less. I want patients to have no side effects after surgery, such as nausea, uncontrolled pain, or confusion. The science we uncover through these investigations into how anesthesia works in the brain may also help people sleep better and identify new ways to treat depression.
Under general anesthesia, auditory processing begins in the cortex, but it doesn’t continue, so we lose the meaning and understanding of vocal commands as well as our ability to respond verbally. Learning is suppressed.
Reprinted from British Journal of Anesthesia, Vol 121, S.L. Eagleman, M.B. MacIver, “Can you hear me now? Information processing in primary auditory cortex at loss of consciousness”, Page 526., Copyright Sep 1, 2018, with permission from Elsevier.
General anesthesia causes changes in breathing pattern, heart rate, and body temperature; thus, anesthesiologists carefully monitor surgery patients to keep them safe.
General anesthesia disrupts communication in synaptic networks, disrupting memory formation.
General anesthesia activates neurons in the amygdala that block pain.
General anesthesia interrupts and overpowers the sensory signals that travel back and forth between the thalamus and cortex.
Auditory and sensory processing is interrupted under general anesthesia, so patients can remain unaware (fortunately!) of what’s going on during surgery.
General anesthesia disrupts memory formation, so patients don’t remember what happens while they are unconscious.
General anesthetics block pain and awareness, allowing people to have life-saving surgeries like heart transplants.
The focus of my research has always been how volatile anesthetics work. Volatile anesthetics, which are inhaled in gas form, are a complete general anesthetic, used every day in operating rooms all over the world. I am trying to find what these compounds bind to in our cells, on a molecular level, that can make us completely unaware during surgery.
To be able to reversibly produce a state of unconsciousness that is oblivious to pain is a very amazing feat. How do we have receptors in us for chemicals that have just recently been discovered, when our brains are the result of an evolution that began millions of years ago? And not just us. All across the animal kingdom, gas anesthetics can work well, even on worms! So whatever is making this happen, it is an ancient pathway in our brains that was there hundreds of millions of years ago when organisms were slowly evolving into different animals. If we could understand how volatile anesthetics work, it could really tell us something about how the central nervous system functions and the nature of consciousness itself. I think that would be a contribution to medicine that would have many, many benefits.