Brain Circuits: Harvard Medical School Researchers Crawl a Neural Network

Summary

This lab research delves into the cerebral cortex, the brain's outer layer responsible for perception, memory, and planning. The study is divided into two parts: observing neuron activity in response to visual stimuli and tracing the physical connections between these neurons using electron microscopy. The team created a 3D wiring diagram by stitching together millions of high-resolution images, allowing them to map a partial circuit and gain insights into how the brain processes visual information. This novel approach offers a powerful tool for exploring the brain's complexity and the enigma of the mind.

Takeaways

• 🧠 The lab focuses on studying the cerebral cortex, the outer part of the brain responsible for perception, memory, and planning.
• 🔬 The research aims to understand the brain circuit by circuit, with each circuit comprising approximately 10,000 neurons and tens of millions of connections.
• 🐁 The first part of the study involves observing the brain's response to visual stimuli by recording the activity of 50 neurons in an animal's brain.
• 💡 Neurons react to specific elements in the visual scene, and each neuron's activation is represented by a flash of light.
• 🔍 A significant challenge in this research is tracing the physical connections between the observed neurons.
• 📸 The second part of the study uses an electron microscope to take millions of high-resolution images of the neurons over several months.
• 🧩 The process of creating a wiring diagram involves assembling a three-dimensional representation of the neural circuit from billions of pixels.
• 👨‍🔬 Three scientists manually traced the connections for 10 selected neurons from the 3D images, creating a partial wiring diagram of the circuit.
• 🎯 The study identified the target neurons for each of the 10 neurons, contributing to the understanding of how the brain processes visual information.
• 🌟 This research offers a new and powerful approach to explore the complexity of brain circuits and contributes to the understanding of how the mind works.

Q & A

What is the primary focus of the lab's research?

The lab's research primarily focuses on studying the cerebral cortex, which is the outer layer of the brain responsible for perception, memory, and planning.

What is a 'circuit' in the context of the cerebral cortex?

A 'circuit' in the context of the cerebral cortex refers to a network of roughly 10,000 neurons with tens of millions of connections between them.

What are the two main aspects researchers aim to understand about these circuits?

Researchers aim to understand what the circuit does and how it does it, which involves studying both the function and the connectivity of the neurons within the circuit.

How does the lab observe the brain's response to visual stimuli?

The lab observes the brain's response to visual stimuli by showing a movie to an animal and recording the activity of 50 neurons in the animal's brain, which light up as they fire in response to specific elements in the visual scene.

What is the challenge in studying these neural circuits?

The challenge lies in tracing the physical connections between the neurons, which requires high-resolution imaging and complex analysis to map out the wiring diagram of the circuit.

What role does the electron microscope play in the study?

The electron microscope is used to take millions of high-resolution pictures of the neurons over several months, which are then assembled into a wiring diagram.

How does the lab create a three-dimensional representation of the neural circuit?

The lab creates a three-dimensional representation by stitching together millions of pictures, comprising billions of pixels, to visualize the dense network of connections between neurons.

What was the process for tracing the connections of the selected neurons?

Three scientists from the lab selected 10 individual neurons that were observed firing in the first part of the study and painstakingly traced their connections using the 3D images, creating a partial wiring diagram of the circuit.

What does this research offer in terms of understanding the brain's visual processing?

This research provides a new approach to understanding how the brain sees by allowing researchers to examine the complex circuits in the brain and their connectivity in detail.

Why is understanding the brain's circuits considered important for studying the mind?

Understanding the brain's circuits is crucial for studying the mind because it offers insights into the complex processes that underlie perception, memory, and cognition, which are fundamental to understanding how the mind works.

Outlines

00:00

🧠 Studying the Cerebral Cortex

The paragraph introduces a lab's focus on studying the cerebral cortex, the outer layer of the brain responsible for perception, memory, and planning. The lab's approach involves examining neural circuits, each consisting of approximately 10,000 neurons with tens of millions of connections. The study is divided into two parts: observing the brain's response to visual stimuli and tracing the physical connections between neurons using electron microscopy. The lab's goal is to understand both the function and the mechanism of these circuits, which is crucial for deciphering how the brain processes visual information.

Keywords

💡Cerebral Cortex

The cerebral cortex is the outer layer of the brain, responsible for higher cognitive functions such as perception, memory, and planning. In the video, the researchers focus on understanding the cerebral cortex by studying its neural circuits, which are crucial for the brain's ability to perceive and process visual information. The script mentions that the cerebral cortex is what 'we use to perceive, remember, and plan things,' highlighting its central role in the study.

💡Neurons

Neurons are the fundamental units of the nervous system, responsible for transmitting information through electrical and chemical signals. The script describes how the researchers observe neurons firing in response to visual stimuli, with each neuron reacting to specific elements in the visual scene. This observation is part of the first part of their study, where they watch the brain's reaction to visual input.

💡Circuit

In the context of the video, a 'circuit' refers to a network of approximately 10,000 neurons with tens of millions of connections between them. The researchers aim to understand the function and operation of these circuits, which is essential for comprehending how the brain processes information. The script states that understanding a circuit involves knowing 'what the circuit does and how it does it.'

💡Electron Microscope

An electron microscope is a high-resolution imaging tool that uses electron beams instead of light to visualize samples. In the video, the researchers use an electron microscope to take millions of pictures of neurons, which are then assembled into a wiring diagram. This technology is crucial for the second part of the study, where they trace the physical connections between neurons.

💡Wiring Diagram

A wiring diagram is a visual representation of the connections between components in a system. In the video, the researchers create a 'wiring diagram' of a neural circuit by assembling millions of high-resolution images. This diagram helps them understand the complex network of connections between neurons, which is essential for deciphering how the brain processes visual information.

💡Three-Dimensional Representation

A three-dimensional representation provides a spatial view of an object or system. The video describes how the researchers create a 3D representation of a neural circuit by stitching together millions of pictures comprising billions of pixels. This approach allows them to visualize and analyze the intricate connections between neurons in a way that was previously not possible.

💡Neural Circuit

A neural circuit is a network of interconnected neurons that work together to perform a specific function. The video's main theme revolves around understanding these circuits, particularly in the context of vision. The researchers' goal is to create a partial wiring diagram of a neural circuit to understand how the brain perceives and processes visual information.

💡Visual Scene

The term 'visual scene' refers to the environment or setting that is perceived through sight. In the video, the researchers show a movie to an animal and observe how specific neurons in the animal's brain react to different elements within the visual scene. This reaction is crucial for understanding how the brain processes and interprets visual information.

💡Firing

In the context of neurons, 'firing' refers to the process of transmitting an electrical signal. When a neuron 'fires,' it is actively sending a signal to other neurons. The script describes how the researchers observe neurons firing in response to specific elements in a visual scene, which is a key aspect of understanding how the brain processes visual information.

💡Mind

The 'mind' is often used to describe the aspect of consciousness that involves thoughts, perceptions, and memories. The video discusses the mystery of how the mind works, which is intrinsically linked to the functioning of the brain. The research presented aims to provide a new approach to exploring this mystery by studying the complexity of neural circuits in the brain.

💡Complexity

Complexity in the video refers to the intricate and detailed nature of the brain's neural circuits. The researchers emphasize the importance of looking at circuits in the brain 'in all of their complexity' to understand how the brain perceives and processes information. This complexity is what makes studying the brain and the mind such a challenging and fascinating endeavor.

Highlights

The lab focuses on studying the cerebral cortex, which is crucial for perception, memory, and planning.

Understanding the cerebral cortex involves examining individual neural circuits, each comprising roughly 10,000 neurons.

Neurons in a circuit are interconnected with tens of millions of connections, forming complex networks.

The study aims to understand both the function and the operational mechanism of these neural circuits.

The first part of the study involves observing the brain's response to visual stimuli.

Neurons react to specific visual elements, as seen through their activation in the brain.

The challenge lies in tracing the physical connections between these activated neurons.

The second part of the study uses an electron microscope to capture high-resolution images of neurons.

Millions of images are taken over several months to create a detailed wiring diagram of the neural circuit.

A three-dimensional representation of the neural circuit is created by stitching together billions of pixels.

Three scientists manually traced the connections of 10 selected neurons from the 3D images.

This partial wiring diagram allows for the first time a detailed look at the connections between individual neurons.

The study provides a new approach to understanding how the brain processes visual information.

The research offers a powerful method to explore the complexity of neural circuits in the brain.

Understanding the mind's workings is one of nature's greatest mysteries, and this study contributes to unraveling it.

The lab's research presents a significant step forward in the field of neuroscience.

Transcripts

my lab studies the brain and in

particular its that is the outside of

the brain the cerebral cortex the

cerebral cortex is what we use to

perceive to remember and to plan things

to understand the cerebral cortex we

would like to go one circuit at a time

and a circuit is roughly 10,000 neurons

with tens of millions of connections

between those neurons to understand one

of these circuits you'd really want two

things you'd want to know what the

circuit does and how it does it so we

did this study in two parts the first

part it's actually something we've been

doing for five or six years now and it's

literally watching the brain see on the

left is a movie we showed an animal on

the right you see 50 neurons that are

flashing away in the animals brain every

time a neuron gets bright it's firing in

fact these neurons are reacting to very

specific elements in the visual scene

the big challenge is tracing the

physical connections between these

particular neurons which brings us to

the second part of the study so this is

the electron microscope that we use to

take millions of pictures over the

course of several months after

collecting high-resolution images of the

neurons in question from our souped-up

microscope we began the process of

assembling a wiring diagram here's a

bird's eye view of the neural circuit

when we zoom in you can begin to see the

impossible thicket of connections

between these cells we created this

three-dimensional representation by

stitching together millions of pictures

comprising billions of pixels then three

scientists my lab selected 10 individual

neurons neurons that would observed

firing in the first part of the study

and they painstakingly traced the

connections for these chosen 10 using

our 3d images they'd crawl through the

brains dense thicket for the first time

jumping from neuron to neuron to create

a partial wiring diagram of the circuit

they were able to identify each neurons

targets as shown here all together this

gives us a new approach to answer the

question how does the brain see more

importantly we can finally look at

circuits in the brain in all of their

complexity how the mind works is one of

the greatest mysteries in nature and

this research presents a new and

powerful way for us to explore that

mystery