Exploring the Brain, Mark F. Bear
Summary
Chapter 1: Past, present, and future
5 Levels of Analysis
- Molecular Neuroscience
o Most elementary level of brain study
o Brain matter; molecules
- Cellular Neuroscience
o How do all the molecules work together?
o What types of neurons are there?
o How do neurons connect?
o How do they perform computations?
- Systems Neuroscience
o “visual system”, “motor system”
o How do different neural circuits analyze sensory info, make decisions, execute
movements, etc.
- Behavioral Neuroscience
o How do those systems work together to create behavior?
o Where do drugs act on?
o Gender-specific behaviors
o Where are dreams created?
o How do these systems contribute to mood and behavior?
- Cognitive Neuroscience
o (greatest challenge) neural mechanisms for higher levels of human mental
activity
o Self-awareness
o Imagination
o Language
o “how the brain creates the mind”
The use of animals in neuroscience research
The more basic the process under investigation, the more distant can the evolutionary
relationship be; e.g., molecular basis of nerve impulse conduction.
More than half are rodents: rats, mice; specifically bred for this purpose
Animal Welfare
Moral responsibilities of neuroscientists:
, 1. Only use animals in worthwhile experiments that promise advance in knowledge of
the nervous system
2. All necessary steps are taken to minimize pain and distress experienced by the animal;
anesthesia, etc.
3. All possible alternatives to using animals are considered
Monitoring happens:
Must pass review by Institutional Animal Care and Use Committee (IACUC)
Then, evaluation for scientific advances by panel of expert neuroscientists
Also, when submitting for publication, papers are carefully reviewed for scientific and animal
welfare concerns
Rejection can lead to stop of funding.
Animal Rights
“animals have same legal and moral rights as humans” hence, all animal testing should be
stopped
But: is the death of mouse equivalent to that of a human being? Is keeping a pet the moral
equivalent of slavery? Etc.
“Animal rights” philosophy is NOT the same as “animal welfare”
Chapter 2: Neurons and Glia
The Neuron Doctrine
- Neurons: sense changes in environment, communicate to other neurons, command
body responses to these sensations
- Glia (or glia cells): insulating, supporting, and nourishing neighboring neurons (glia =
glue)
“if the brain were a chocolate chip cookie, and neurons the chocolate chips, the glia would be
the dough that keep the chips in place”
Cell size: 0.01 – 0.05 mm in diameter
Neurons cannot be seen by naked eye; cellular neuroscience could thus not progress before
development of compound microscope in late 17th century (1600s)
Histology: microscopic study of the structure of tissue
Staining allows for selectively coloring neurons
Nissl staining; staining of nuclei of all cells, as well as clumps of material surrounding nuclei of
neurons = “Nissl bodies”
Useful because:
1. Distinguishes between neurons and glia
, 2. Enables histologists to study arrangement (cytoarchitecture) of neurons in different
parts of the brain. Cyto = cell
This led to the realization that brain consists of specialized regions with different functions!
The Golgi Stain
Soaking brain in silver chromate solution
Makes a small percentage of neurons become darkly colored in their entirety
Showed that: neurons have two distinguishable parts;
- central region (cell nucleus); cell body, soma, perikaryon
- and thin tubes that are connected to it; axons (long, send out), dendrites (short,
receive)
Cajal’s Contribution
Histologist that used the Golgi method
Was the first to state that neurons worked like cells; they are separate and in contact with
each other, not continuous -> the “reticular theory” by Golgi; seeing the neurons as fused
together, working like arteries.
Cajal: “neurons communicate by contact, not continuity” = Neuron Doctrine
This was supported later by the electron microscope in 1950s
Electron Microscope
- Uses an electron beam instead of “standard” light microscope.
- Limit of resolution = 0.1 nm. Compared to 0.1 micrometers for light telescope. 1000x
better!
- Space between neurons is 20 nm
- New techniques allow for looking into brain tissue that is still alive!
The Prototypical Neuron
Also called “nerve cell”. Consists of: Soma, dendrites, axon
Inside separated from outside by “neuronal membrane”
Cell body is about 20 micrometers
The Soma
Watery fluid inside = Cytosol
- Is salty, and potassium rich
- Is kept together by neuronal membrane
Within soma:
- Organelles; structures within the membrane
o Nucleus
o Rough endoplasmic reticulum (rough ER)
o Smooth endoplasmic reticulum (smooth ER)
o Golgi apparatus
o Mitochondria
, - Everything within cell membrane together, EXCEPT for nucleus, is called the
“cytoplasm”
The Nucleus
- Contained within double membrane called “nuclear envelope”
- Within nucleus: chromosomes; which contain DNA
o Same DNA as in any other cell in the body
o But difference lies in what specific parts of the DNA are used to ensemble the
cell; genes
Summary
Chapter 1: Past, present, and future
5 Levels of Analysis
- Molecular Neuroscience
o Most elementary level of brain study
o Brain matter; molecules
- Cellular Neuroscience
o How do all the molecules work together?
o What types of neurons are there?
o How do neurons connect?
o How do they perform computations?
- Systems Neuroscience
o “visual system”, “motor system”
o How do different neural circuits analyze sensory info, make decisions, execute
movements, etc.
- Behavioral Neuroscience
o How do those systems work together to create behavior?
o Where do drugs act on?
o Gender-specific behaviors
o Where are dreams created?
o How do these systems contribute to mood and behavior?
- Cognitive Neuroscience
o (greatest challenge) neural mechanisms for higher levels of human mental
activity
o Self-awareness
o Imagination
o Language
o “how the brain creates the mind”
The use of animals in neuroscience research
The more basic the process under investigation, the more distant can the evolutionary
relationship be; e.g., molecular basis of nerve impulse conduction.
More than half are rodents: rats, mice; specifically bred for this purpose
Animal Welfare
Moral responsibilities of neuroscientists:
, 1. Only use animals in worthwhile experiments that promise advance in knowledge of
the nervous system
2. All necessary steps are taken to minimize pain and distress experienced by the animal;
anesthesia, etc.
3. All possible alternatives to using animals are considered
Monitoring happens:
Must pass review by Institutional Animal Care and Use Committee (IACUC)
Then, evaluation for scientific advances by panel of expert neuroscientists
Also, when submitting for publication, papers are carefully reviewed for scientific and animal
welfare concerns
Rejection can lead to stop of funding.
Animal Rights
“animals have same legal and moral rights as humans” hence, all animal testing should be
stopped
But: is the death of mouse equivalent to that of a human being? Is keeping a pet the moral
equivalent of slavery? Etc.
“Animal rights” philosophy is NOT the same as “animal welfare”
Chapter 2: Neurons and Glia
The Neuron Doctrine
- Neurons: sense changes in environment, communicate to other neurons, command
body responses to these sensations
- Glia (or glia cells): insulating, supporting, and nourishing neighboring neurons (glia =
glue)
“if the brain were a chocolate chip cookie, and neurons the chocolate chips, the glia would be
the dough that keep the chips in place”
Cell size: 0.01 – 0.05 mm in diameter
Neurons cannot be seen by naked eye; cellular neuroscience could thus not progress before
development of compound microscope in late 17th century (1600s)
Histology: microscopic study of the structure of tissue
Staining allows for selectively coloring neurons
Nissl staining; staining of nuclei of all cells, as well as clumps of material surrounding nuclei of
neurons = “Nissl bodies”
Useful because:
1. Distinguishes between neurons and glia
, 2. Enables histologists to study arrangement (cytoarchitecture) of neurons in different
parts of the brain. Cyto = cell
This led to the realization that brain consists of specialized regions with different functions!
The Golgi Stain
Soaking brain in silver chromate solution
Makes a small percentage of neurons become darkly colored in their entirety
Showed that: neurons have two distinguishable parts;
- central region (cell nucleus); cell body, soma, perikaryon
- and thin tubes that are connected to it; axons (long, send out), dendrites (short,
receive)
Cajal’s Contribution
Histologist that used the Golgi method
Was the first to state that neurons worked like cells; they are separate and in contact with
each other, not continuous -> the “reticular theory” by Golgi; seeing the neurons as fused
together, working like arteries.
Cajal: “neurons communicate by contact, not continuity” = Neuron Doctrine
This was supported later by the electron microscope in 1950s
Electron Microscope
- Uses an electron beam instead of “standard” light microscope.
- Limit of resolution = 0.1 nm. Compared to 0.1 micrometers for light telescope. 1000x
better!
- Space between neurons is 20 nm
- New techniques allow for looking into brain tissue that is still alive!
The Prototypical Neuron
Also called “nerve cell”. Consists of: Soma, dendrites, axon
Inside separated from outside by “neuronal membrane”
Cell body is about 20 micrometers
The Soma
Watery fluid inside = Cytosol
- Is salty, and potassium rich
- Is kept together by neuronal membrane
Within soma:
- Organelles; structures within the membrane
o Nucleus
o Rough endoplasmic reticulum (rough ER)
o Smooth endoplasmic reticulum (smooth ER)
o Golgi apparatus
o Mitochondria
, - Everything within cell membrane together, EXCEPT for nucleus, is called the
“cytoplasm”
The Nucleus
- Contained within double membrane called “nuclear envelope”
- Within nucleus: chromosomes; which contain DNA
o Same DNA as in any other cell in the body
o But difference lies in what specific parts of the DNA are used to ensemble the
cell; genes
