Transcript Introduction to Biopsychology [PSB 4002]

Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
Big Questions for Biopsychology
• How is the nervous system structured and
organized? How does the nervous system
develop?
• How does the nervous system process and
represent information about an organism’s
internal and external environment?
• How does the brain change during learning
and how are memories stored and retrieved?
How does the brain “think”?
Big Questions Continued
• What brain sites and activities underlie
emotions and feelings?
• What brain regions are
involved in language?
• How does
consciousness emerge
from the activities of a
nervous system?
What is inside your head?
• Your cerebral cortex, critical to higher brain
functions such as speech, thought, complex
movement patterns, goals and planning, has
about 10 billion neurons (nerve cells)
• Each of these neurons
receives connections from
other neurons at sites called
synapses. There are roughly
one million billion of these
connections in just in your
cerebral cortex
What is inside your head?
• If you set out to count these connections, one
connection (synapse) per second, you would
finish counting 32 million years after you
began counting.
• Another way of getting a feeling for this
complexity is to consider that a match head’s
worth of your brain contains about 1 billion
connections.
What is inside your head?
• If we consider how the connections between
neurons might be variously combined, the
number becomes hyperastronomical – 10
followed by millions of zeros.
• So we have our first clue as to what makes the
brain so remarkable, because when one adds the
chemical factors (neurotransmitters, hormones)
that influence neurons, we are talking about the
most complicated material object in the known
universe.
Complexity
• Complexity turns out to be difficult to define,
but there are five attributes that in
combination seem to be involved:
large number of parts, large number of levels
large number of interactions among parts and
levels
hierarchical organization (of multiple levels)
non-linearity (not A  B C D)
Complexity
• and perhaps most important, emergent
properties (the whole is greater than the sum of
the parts)
• emergent properties cannot be predicted based
on knowledge of the properties of the parts alone
(example of water, H2O)
• emergence will turn out to be important in how
we make sense of higher order mental functions,
such as thinking, dreaming, and consciousness
A Systems Perspective
The brain’s job is to facilitate an adaptive
dynamic pattern of interaction among
brain, body, and the world
In other words, neural systems are
elements of a larger system that includes
the rest of the organism’s body and also its
situation in and interaction with the
environment
Historical Perspective
• Traditional views within psychology, cognitive
science and philosophy have often characterized
the mind as an abstract information processor
largely divorced from the body and the
environment.
Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
The Notion of Embodiment
• Proposes that all aspects of perception, movement,
cognition, and interactions with the environment are
based on the coupling of a brain, in a body, in an
environment.
• Embodiment thus refers to bodily interactions with
the world, which is proposed to be a necessary
precondition for subjectivity, emotion, value and
meaning. These interactions are based on (and
constrained by) the actual shape and physical
capacities and limits of the body.
The overall function of the brain is to be well
informed about what goes on in the rest of the
body, about what goes on in itself, and about
the environment surrounding the organism.
Regulating both internal and external stimuli
involves the process of homeostasis.
Homeostasis involves (at the very least) the
coupling of a number of complex systems
beyond simply the nervous system.
The Bidirectional Coupling of Levels
Meeting the challenge of homeostasis involves:
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•
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•
•
central nervous system
autonomic (peripheral) nervous system
endocrine system
immune system
limbic system
Insight
• Given that the brain’s primary job is to
coordinate our dealings with the
environment, it is only in the context of
the brain, body, and environment
”system” that the function of the brain can
be understood
Neurons
• Like all cells of the body, neurons contain:
1. nucleus
2. cytoplasm
3. cell membrane
• However, neurons are specialized to communicate
with other neurons, muscles, glands, and other
internal organs. This is achieved via:
4. axon
5. dendrites
6. synapses
Neurons
•Axons are coated
(insulated) by myelin,
improving the flow of
electrical events from cell
to cell
Neurons
• Nerve cells are arranged in circuits and these are
arranged in neural networks
• There are three basic types of neurons:
– sensory neurons (input)
– motor neurons (output)
– interneurons (integration)
The Language of the Nervous System
• There are two forms or channels of
communication between neurons
– electrical: action potentials / an all or nothing
mode
– chemical: neurotransmitters / many and
modulated
Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
First Exam
• Exam Date is Friday, January 25th
• Will be combine the terms outlined in the
textbook (Chapters 1, 3, and 6) with the
information in the class lectures.
• IF ATTENDANCE IS SATISFACTORY then you will
receive the lecture notes to help you study one
week before the exam. You will receive sample
test questions to help you study.
emergence
• The manner in which complex phenomena
arise from a collection of interactions between
system components
• The outcome is more than the sum of its parts
• The brain is a complex temporally
and spatially multiscale structure
that gives rise to complex molecular,
cellular, and neuronal phenomena
that together form a basis for
perception, movement, cognition.
The Language of the Nervous System
• There are two forms or channels of
communication between neurons
– electrical: action potentials / an all or nothing
mode
– chemical: neurotransmitters / many and
modulated
HOW NEURONS COMMUNICATE WITH EACH
OTHER CHEMICALLY
• The connection between two neurons is called
a synapse
• The neurons are not in direct physical contact
at the synapse but are separated by a small
gap called the synaptic cleft
• The neuron transmitting to another is called
the presynaptic neuron
• The receiving neuron is the postsynaptic
neuron
The Synapse Between a Presynaptic Neuron and
a Postsynaptic Neuron
HOW NEURONS COMMUNICATE WITH
EACH OTHER
•A Presynaptic
Terminal Releases
Neurotransmitter at
the Synapse
Development of the Nervous System
•The human genome has approximately 25,000
genes; the brain and spinal cord (CNS) has more
than 100 billion neurons. Clearly these numbers
indicate that nervous system development cannot
be simply “genetically determined” or prescribed.
• Gene expression is certainly involved in all
aspects of nervous system activity and the
behavior it supports, but many other factors and
processes must be at play
Central Nervous System (CNS)
Development is an historical process
- initial conditions are powerful
- one thing leads to another
- what happens before guides and constrains
what can happen next
- particular pathways taken promote or make less
likely other pathways becoming available
Self-Organization:
•Self-organization is the process in which
pattern at the global level of a system
emerges from numerous interactions among
the lower-level components of the system.
•Thus, self-organization is an emergent
property of the system, rather than imposed
on the system by a pre-specified program or
set of instructions.
Self-Organization
Example: termite mounds
Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
First Exam
• Exam Date is Wednesday, January 30th
• Will be combine the terms outlined in the
textbook (Chapters 1, 3, and 6) with the
information in the class lectures.
• IF ATTENDANCE IS SATISFACTORY then you will
receive the lecture notes to help you study one
week before the exam. You will receive sample
test questions to help you study.
Two Key Concepts in Making Sense of
Developmental Processes:
- self-organization
- loss of degrees of freedom
What determines the structure and behavior
of a system are particular relational conditions
of the system and the environment over time
Self-organization can be contrasted to the
notion of organization by design.
Example: A car or a computer - in order to
work, every detail must function according
to a preconceived plan or design.
Loss of Degrees of Freedom:
The emergence of structure or pattern at any
point in a developmental sequence constrains
or limits what structure or pattern can occur
next.
Example: moving into a new apartment
The “instructions” for development don’t
reside or exist anywhere – they emerge out
of how an organism lives and interacts with
its world
This insight leads us to a key insight in our
exploration of development: the
minimum unit of analysis for
understanding the nervous systems is the
coupling of a brain, in a body, in a
complex physical and social environment
Development in utero
• The human ovum is the largest cell in the
body, roughly 15 times larger than other cells,
but it is still no larger than a dot, much much
smaller that the period at the end of this
sentence.
• Over about 277 days of gestation, this one
fertilized cell will become trillions of cells, all
organized into the various glands, tissues,
organs, etc. that constitute our brain/body
system.
Some perspective:
How old are you?
• As it turns out, not a straightforward question, as
the egg that developed following fertilization into
you was formed when your mother was a fetus –
so, at least from our mother’s side of the story,
you are as old as your mother.
• Human development before birth takes place in
three stages:
– zygote (first 2 weeks following conception)
– embryo (3-8 weeks following conception)
– fetus (8-38 weeks following conception)
Principles at Play
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•
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Self-organization
Reducing degrees of freedom
Sensitive periods
Developmental cascades
• This process of prenatal development consists of a
cascade of many thousands of events – a cascade is
a succession of sequentially interdependent events,
with each event both triggered/influenced by the
event(s) preceding it and in turn itself acting as a
trigger for the next event(s).
• The cascade of prenatal development involves gene
expression events, chemical events, cellular events,
and their interactions. No surprise - these events are
influenced by factors both internal and external to
the developing embryo or fetus.
Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
First Exam
• Exam Date is Wednesday, January 30th
• Will be combine the terms outlined in the
textbook (Chapters 1, 3, and 6) with the
information in the class lectures.
• IF ATTENDANCE IS SATISFACTORY then you will
receive the lecture notes to help you study one
week before the exam. You will receive sample
test questions to help you study.
Principles at Play
•
•
•
•
Self-organization
Reducing degrees of freedom
Sensitive periods
Developmental cascades
Key Processes in the Prenatal
Development of the Nervous System
1. Induction: cells on the ectoderm form a
neural tube, induced by cells below it in
the mesoderm
2. Proliferation: cell division results in an
incredibly rapid generation of tens of
thousands of cells per minute (during the
last half of gestation, over 250,000 cells
per minute)
Key Processes (continued)
3. Migration: moving from the neural tube
to the location where the cell will form a
part of the brain and become functional,
with help from glial cells
4. Aggregation: similar cells come together
by means of chemical and electrical
gradients produced by surrounding cells
Key Processes (continued)
5. Differentiation: sprouting axon and
dendrites by means of a growth cone
6. Circuit and Network Formation: connecting
synapses and axons and producing
neurotransmitters, thereby establishing
channels of communication across the NS
Circuit Formation
• During circuit formation, the axons of
developing neurons grow toward their target
cells and form functional connections.
– To find their way, axons form growth cones
at their tip which sample the environment
for directional cues.
– Chemical and molecular signposts attract or
repel the advancing axon, coaxing it along
the way.
Key Processes (continued)
7. Cell Death (apoptosis): based on patterns
of activity, experience, and use
DEVELOPMENT AND CHANGE
IN THE NERVOUS SYSTEM
8. The next stage of neural development, circuit pruning,
involves the elimination of excess neurons and
synapses.
– neurons that are unsuccessful in finding a place on a
target cell, or that arrive late, or that don’t get activated,
die.
• In the second step of circuit pruning, the nervous system
refines its organization and continues to correct errors by
eliminating large numbers of excessive synapses.
– synapses are strengthened or weakened depending on
whether the pre-synaptic neuron and the postsynaptic
neuron fire together (temporal synchrony).
Prenatal Development of the Nervous
System
(summary of eight processes)
•Induction
•Proliferation
•Migration
•Aggregation
•Differentiation
•Circuit formation
•Cell death (apoptosis)
•Circuit pruning
Prenatal Development
Introduction to Biopsychology
[PSB 4002]
Professor Josh Herrington
DM 249 305-348-1230
[email protected]
website: dpblab.fiu.edu
First Exam
• Exam Date is Wednesday, January 30th
• Will be combine the terms outlined in the
textbook (Chapters 1, 3, and 6) with the
information in the class lectures.
• IF ATTENDANCE IS SATISFACTORY then you will
receive the lecture notes to help you study one
week before the exam. You will receive sample
test questions to help you study.
Prenatal Development
Fetal Programming
• The Prenatal environment provides
experiences and affordances that allow for
typical neural development
POSTNATAL DEVELOPMENT IN THE NERVOUS SYSTEM
•patterns of increased connectivity and organization, and synchronization of
activity
•increased number of dendrites, axon branches, synapses
•increased brain weight, increased thickness of cortex
•increasing degree of mylenation of axons
•all of these processes involve experience and activity-dependent competition and
selection
POSTNATAL DEVELOPMENT IN THE NERVOUS SYSTEM
• The neural networks of the brain are made during
development by cellular movement, extensions,
and connections increasing numbers of neurons.
• The number of cells being made, dying, and
becoming incorporated into the nervous system is
huge. The entire situation is a dynamic one,
depending on signals, proteins, cell movement,
divisions, gradients, and cell death, all interacting
at many levels.
POSTNATAL DEVELOPMENT AND CHANGE
IN THE NERVOUS SYSTEM
• Stimulation continues to shape synaptic
construction and reconstruction throughout the
individual’s life.
• Much of the change resulting from experience in
the mature brain involves reorganization, a shift in
connections that changes the function of an area of
the brain.
Nervous System
•The process of nervous system development is
cumulative (builds on itself) – events occurring in one
place require that previous events have occurred at
other places. In other words, brain structure and
function is
• historical
• situated
• contingent
Nervous System
•The KEY mechanisms involved in the process of
nervous system development are :
• competition
• selection
Nervous System
•The notion of experience-dependent development
-interactions with the environment modify gene
activity and expression and shape the course of
nervous system construction and modification
Postnatal Maternal Care in Rodents
Variations in care lead
to variations in
offspring phenotype
stress
responsivity
response to
reward
natural variations in
maternal care
High vs. Low
levels of licking/grooming
stimulation of pups
cognition
social
behavior
Real Time/ Developmental Time
•Real Time: firing patterns of diverse neural networks;
cell groups transmit information to each other;
activities of brain regions cohere or synchronize it real
time (we can now observe this with neural imaging
technology)
•Developmental Time: increasing specification of
structure; increased levels of organization based on
real time use. The overall cumulative effects of
activity and experience over time sculpts the nervous
system.