The Tale of the Dueling Neurosurgeons

1. Brain Injuries Offer Unique Insights

Tiny flaws in the brain had strange but telling consequences all the time.

Accidental discoveries. Neuroscience has advanced significantly through the study of individuals with brain injuries. These unfortunate events, such as strokes, accidents, or botched surgeries, reveal how specific brain areas contribute to various mental functions. By observing the deficits that arise from damage to particular regions, scientists can infer the roles those areas play in normal cognition and behavior.

Historical examples. The case of Phineas Gage, who suffered a personality change after a tamping iron pierced his frontal lobes, provided early evidence for the role of the frontal cortex in executive functions and social behavior. Similarly, the study of patients with aphasia, who lost the ability to speak after damage to specific brain regions, led to the identification of Broca's and Wernicke's areas as critical for language production and comprehension.

Modern relevance. Despite advances in brain-scanning technologies, injuries remain invaluable for understanding the brain. They offer a direct way to link specific brain areas to particular functions, providing insights that are difficult to obtain through other methods. The study of brain injuries continues to be a cornerstone of neuroscience research, helping to unravel the complexities of the human mind.

2. Neurotransmitters: The Brain's Chemical Messengers

These psychoses depend rather upon circulatory and chemical disturbances.

Chemical communication. Neurons communicate with each other through chemical messengers called neurotransmitters. These chemicals are released from the axon tip of one neuron, cross the synapse, and bind to receptors on the dendrites of another neuron, transmitting signals throughout the brain. Different neurotransmitters have different effects, with some exciting neurons and others inhibiting them.

Balance is key. The proper functioning of the brain depends on a delicate balance of neurotransmitters. Imbalances in these chemicals can lead to a variety of neurological and psychiatric disorders. For example, schizophrenia is associated with disruptions in dopamine and glutamate, while depression is linked to serotonin and norepinephrine imbalances.

Pharmacological interventions. Many psychiatric medications work by targeting neurotransmitter systems. Selective serotonin reuptake inhibitors (SSRIs), for instance, increase serotonin levels in the brain, helping to alleviate symptoms of depression. Understanding the role of neurotransmitters has been crucial for developing effective treatments for mental illness.

3. Neural Circuits: The Brain's Intricate Wiring

Neurons that fire together wire together.

Interconnected networks. Neurons are not isolated entities but rather interconnected in complex networks called circuits. These circuits are responsible for processing information and generating behavior. The strength of connections between neurons can change over time, a process known as synaptic plasticity.

Experience shapes circuits. Repeated activation of a particular circuit strengthens the connections between the neurons involved, making it easier for that circuit to be activated in the future. This principle, often summarized as "neurons that fire together, wire together," underlies learning and memory.

Vertical organization. Cajal saw neurons arranged into tiny vertical "columns" of around one hundred neurons each—little stacks that covered the surface of the brain like stubble. Axons from one column did sometimes reach horizontally into neighboring columns, Cajal admitted, but vertical organization was the general rule.

4. Sensory Substitution: Rewiring the Brain

We don’t see with the eyes, we don’t hear with the ears. All of that goes on in the brain.

Brain's adaptability. The brain has a remarkable ability to adapt to changing circumstances, a property known as plasticity. This plasticity allows the brain to rewire itself in response to injury or sensory deprivation. Sensory substitution devices exploit this plasticity to provide alternative pathways for sensory information.

Examples of sensory substitution:

• Tongue display: Converts visual information into electrical stimulation on the tongue, allowing blind individuals to "see" with their tongues.
• BrainPort Balance: Uses electrical stimulation on the tongue to provide balance information to individuals with vestibular disorders.

Underlying mechanisms. Sensory substitution works by rerouting sensory information to different brain areas. For example, in blind individuals using a tongue display, the visual cortex becomes activated by tactile input from the tongue. This demonstrates the brain's ability to repurpose existing neural circuits for new functions.

5. The Brain's Reliance on Movement and Feedback

Running into a pole is a drag, but never being allowed to run into a pole is a disaster.

Action and perception. The brain relies on movement and feedback to create a coherent perception of the world. Sensory information is not passively received but actively sought out through exploration and interaction. Movement provides crucial information about the environment, allowing the brain to construct a more complete and accurate representation.

Echolocation. Blind individuals who use echolocation, such as Daniel Kish, demonstrate the brain's ability to extract spatial information from sound. By clicking their tongues and listening to the echoes, they can navigate complex environments and perceive the size, shape, and texture of objects.

Importance of feedback. Feedback from the body is essential for motor control and coordination. The cerebellum, a brain region involved in motor learning, relies on sensory feedback to refine movements and correct errors. Without feedback, movements become clumsy and uncoordinated.

6. The Power and Peril of Specialized Brain Regions

The world’s finest surgeon spent his twilight in Paris, having served four kings, and he died in his bed in one of his five houses.

Modular organization. The brain is organized into specialized regions that perform specific functions. For example, the visual cortex processes visual information, the auditory cortex processes auditory information, and the motor cortex controls movement. This modular organization allows the brain to perform complex tasks efficiently.

Category deficits. Damage to specific brain regions can result in highly selective deficits, such as the inability to recognize animals, fruits, or tools. These category deficits suggest that the brain has specialized circuits for processing different types of information.

Tradeoffs of specialization. While specialization allows for efficient processing, it also makes the brain vulnerable to targeted damage. If a particular circuit is damaged, the corresponding function may be lost, even if other brain areas remain intact. This highlights the importance of redundancy and plasticity in the brain.

7. The Interplay of Reason and Emotion

We don’t see with the eyes. We see with the brain.

Intertwined systems. Reason and emotion are not separate and opposing forces but rather intertwined systems that work together to guide behavior. The limbic system, which is involved in processing emotions, interacts closely with the frontal lobes, which are responsible for higher-level cognitive functions.

Emotional tagging. Emotions play a crucial role in decision-making by tagging options with positive or negative feelings. These emotional tags help us to quickly evaluate choices and select the most advantageous course of action.

The case of Elliot. Damage to the connections between the frontal lobes and the limbic system can disrupt this interplay, leading to impaired decision-making and social behavior. The case of Elliot, who lost his ability to experience emotions after brain surgery, illustrates the importance of emotions for rational thought.

8. Delusions: When the Mind Fabricates Reality

I am constantly asked… what is the use of travelling to one who cannot see?

Distorted perceptions. Delusions are false beliefs that are held despite evidence to the contrary. They can arise from a variety of causes, including brain damage, psychiatric disorders, and substance abuse. Delusions can take many forms, ranging from bizarre and fantastical to relatively mundane.

Capgras syndrome. Capgras syndrome is a delusion in which a person believes that a loved one has been replaced by an imposter. This delusion is thought to result from a disconnection between the visual cortex and the limbic system, preventing the person from experiencing the normal emotional response to seeing a familiar face.

Underlying mechanisms. Delusions often involve a combination of cognitive and emotional factors. Damage to specific brain regions can disrupt the normal processing of information, leading to distorted perceptions and beliefs. Emotional factors, such as anxiety and paranoia, can also contribute to the formation and maintenance of delusions.

9. Memory: A Fragile Tapestry of the Past

I’m Going to the Lordy.

Constructive process. Memory is not a perfect recording of the past but rather a constructive process that involves encoding, storage, and retrieval. Each of these stages is susceptible to errors and distortions. Memories can be influenced by our current beliefs, emotions, and expectations.

Types of memory. Different types of memory rely on different brain structures. The hippocampus is crucial for forming new declarative memories (facts and events), while the amygdala is involved in emotional memories. Damage to these brain regions can result in specific memory deficits.

Confabulation. Confabulation is the unintentional fabrication of memories, often to fill in gaps in recall. It can occur in individuals with damage to the frontal lobes, which are involved in monitoring and verifying memories. Confabulation highlights the constructive nature of memory and the potential for distortions to arise during retrieval.

10. The Elusive Nature of Consciousness

I treated him, God healed him.

Subjective experience. Consciousness is the subjective experience of being aware of oneself and one's surroundings. It is a complex phenomenon that has been difficult to define and study scientifically. Consciousness involves a variety of cognitive processes, including attention, perception, memory, and emotion.

Neural correlates of consciousness. Neuroscientists have identified several brain regions that are thought to be critical for consciousness, including the prefrontal cortex, parietal cortex, and thalamus. These regions are interconnected in a complex network that allows for the integration of information and the generation of subjective experience.

Altered states of consciousness. Altered states of consciousness, such as sleep, meditation, and drug-induced states, can provide insights into the neural basis of consciousness. By studying how these states affect brain activity and subjective experience, scientists can gain a better understanding of the mechanisms that underlie consciousness.

11. The Brain's Hemispheric Divide

I’m a dead man.

Lateralization of function. The brain is divided into two hemispheres, each of which specializes in certain functions. The left hemisphere is typically dominant for language, logic, and analytical thinking, while the right hemisphere is dominant for spatial processing, creativity, and emotional expression.

Split-brain studies. Split-brain studies, in which the corpus callosum connecting the two hemispheres is severed, have provided valuable insights into the functions of each hemisphere. These studies have revealed that each hemisphere can operate independently, with its own thoughts, feelings, and perceptions.

Integration and collaboration. Despite their differences, the two hemispheres normally work together in a coordinated fashion. The corpus callosum allows for communication between the hemispheres, enabling them to share information and integrate their functions. This integration is essential for complex cognitive tasks.

12. The Self: A Tenacious Core Amidst Change

I’m awfully sorry because I did not see my father [again].

Multifaceted construct. The self is a complex and multifaceted construct that encompasses our sense of identity, personality, and values. It is shaped by a variety of factors, including genetics, experience, and social interactions. The self is not a fixed entity but rather a dynamic process that evolves over time.

Neurological basis of self. The self is thought to be supported by a network of brain regions, including the prefrontal cortex, parietal cortex, and limbic system. These regions work together to integrate information about our past, present, and future, creating a coherent sense of self.

Resilience of the self. Despite the potential for brain damage to disrupt our sense of self, the self is remarkably resilient. Even individuals with severe brain injuries often retain a core sense of identity and continue to experience emotions, form relationships, and pursue goals. This highlights the enduring power of the human spirit.

Last updated: February 23, 2025