Transcript Document

Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
Chapter 5 The Brain
“The brain is contained within the cranium, and constitutes the upper, greatly
expanded part of the central nervous system.”
Henry Gray, Anatomy of the Human Body, 1918
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
Chapter Outline
1.0 Introduction
2.0 Growing the brain from the bottom up
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
4.0 Summary
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The nervous system …
The two main parts of the nervous system are the
central nervous system (CNS), which includes the
brain and spinal cord, and the peripheral nervous
system (PNS), which includes the autonomic and
peripheral sensory and motor system.
Together, the CNS and PNS provide a dynamic and
massive communication system throughout all
parts of the body, with a hub at the brain that is
accessed through the spinal cord.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The CNS …
The brain sits atop the CNS, a dynamic and
highly interconnected hub of activity.
Here is a side -- or lateral -- view of the brain
inside the head. The slice is taken at the
mid-sagittal position, in the center of the
brain between the two hemispheres.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The geography of the brain
The four major lobes of the brain are visible
from a lateral view.
A lateral view of the left hemisphere, with the
frontal lobe (purple) at the anterior of the
brain, the parietal lobe (orange) posterior to
the frontal lobe at the superior aspect of the
brain, the temporal lobe (blue) posterior to
the frontal lobe and inferior to the parietal
lobe, and the occipital lobe (yellow) which is
posterior to both the parietal and temporal
lobes.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The geography of the brain
Some important landmarks of the brain in the left hemisphere from a lateral
perspective (left panel) and a mid-sagittal perspective (right panel).
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The geography of the brain
The Brodmann classification (based on microscopic cell differences) of regions in the left
hemisphere, shown in a lateral view. Areas 41 & 52 are indicated by lines. Some areas,
like the insula and auditory region, are tucked away behind the temporal lobe.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The geography of the brain
The Brodmann classification of regions in the left hemisphere in mid-sagittal view.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
1.0 Introduction
The geography of the brain
A schematic drawing of the six
layers in the gray matter of the
cortex. Some cortical neurons
send their axons to the thalamus,
while others receive input from
thalamic neurons.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
2.0 Growing a brain from the bottom up
Evolution and personal history are expressed in the brain
The brain has grown and evolved from the
inside out, much like a seed grows into a
tree. Lower regions like the brainstem are
generally more ancient than higher regions,
such as the frontal cortex.
Basic survival functions like breathing are
controlled by neural centers in the lower
brainstem, while the large prefrontal cortex
in humans is a late addition to the basic
mammalian brain plan.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
2.0 Growing a brain from the bottom up
Building a brain from bottom to top
The brain builds on the brainstem,
with the thalami on top as a major
input hub. The hippocampi and
amygdalas are actually nestled
inside each of the temporal lobes.
The light blue ventricles have no
neurons, but provide the brain’s own
circulatory system. The basal ganglia
can be thought of as the output hub
of the system. A great deal of traffic
flows back to the cortex as well.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
2.0 Growing a brain from the bottom up
Building a brain from bottom to top
The cerebral hemispheres are shown
mounted above the brainstem and the
other subcortical bodies.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The cerebral hemispheres: the left-right division
The two hemispheres are completely
separate, divided by the longitudinal
fissure that runs between the two
hemispheres from the anterior to the
posterior part of the brain.
A schematic view of the two
hemispheres, showing some major
functions of the left and right
hemispheres.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The cerebral hemispheres: the left-right division
How do the hemispheres ‘talk’ to each
other?
The link between the hemispheres is
provided by the corpus callosum, a
large arch of white matter, shown in
this cut-away of a 3-dimensional MRI.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
Output and input: the front-back division
The frontal lobe typically is involved in
executive and motor (output) functions.
The posterior half of the brain is involved
in sensory processing.
A view of functional areas in sensory
regions of the cortex: the central sulcus
separates the frontal lobe from the
parietal. Immediately anterior to the
central sulcus are motor areas, and just
posterior to the central sulcus is the
primary somatosensory area.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
Output and input: the front-back division
A homonculus (‘little man’) shows the
body map for motor representation of
different areas of the body. Note that some
body areas, such as the fingers, have
disproportionately larger representation
than other body areas, such as the trunk.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
Output and input: the front-back division
A homonculus (‘little man’) shows the
body map for somatosensory
representation of different areas on the
body. Note that some body areas, such as
the face, have disproportionately larger
representation than other body areas,
such as the trunk.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
Output and input: the front-back division
The close physical connection between motor cortex, located just anterior to the
central sulcus, and the somatosensory cortex, located just posterior to it, allows for a
tight coupling between the senses of touch, pressure, and pain and the action or
motor system.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The major lobes: visible and hidden
The frontal lobe is the site for motor
planning and motor output, but in
humans the frontal lobe -- especially the
prefrontal cortex -- performs many other
functions:
Initiating activities
Planning
Holding critical information ready to use
Changing mental set from one line of thinking to another
Monitoring the effectiveness of ones actions
Inhibiting plans and actions that are ineffective or self defeating
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The major lobes: visible and hidden
How to locate the prefrontal cortex:
The frontal lobe lies anterior to the
central sulcus. The two purple gyri (hills)
immediately in front of the central sulcus
are call the motor and premotor cortex.
The reddish purple patch in front of that
is called the supplementary motor
cortex. The three shades of yellow in the
frontal third of the whole cortex is the
prefrontal cortex, often considered the
most ‘cognitive’ part of the brain.
central sulcus
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The parietal lobe is posterior to the
frontal lobe. The anterior portion of the
parietal lobe contains somatosensory
cortex. One important function of the
parietal lobe that it contains multiple
maps of body space. Other important
functions are multisensory integration.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The temporal lobe is posterior to the
frontal lobe and inferior to the parietal
lobe. The temporal lobe contains
auditory cortex where sound is
processed, as well as language
reception and comprehension regions.
The middle regions of the temporal lobe
are important to memory and the inferior
posterior regions are involved in visual
object representation.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The occipital lobe, located at the
posterior of the brain, is home to visual
cortex. The visual system occupies a
large region of the occipital lobe that
extends upwards to the parietal lobe and
anterior to the temporal lobe.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The massive interconnnectivity
of the cortex and thalamus
The cortex and thalamus are a
massively interconnected system:
color coding shows the mapping of
connections between cortical and
thalamic regions.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
3.0 From ‘where’ to ‘what’: the functional roles of brain regions
The massive interconnnectivity of the cortex
Top: schematic drawing of the connectivity of
the brain, showing major fiber patterns.
Bottom: diffusion tensor image of white
bundles of myelinated axons which run in all
directions through the cortical domes.
Cognition, Brain and Consciousness: An Introduction to Cognitive Neuroscience
Edited by Bernard J. Baars and Nicole M. Gage
2007 Academic Press
4.0 Summary
Important concepts:
The brain has developed and changed through time and so some areas of the
brain are ‘older’ than others.
The cortex represents recent brain developments in the human, and frontal and
parietal lobes have expanded their neural territory as compared to non-human
primates.
While there are separate regions and parts of the brain, such as the two
hemispheres and the four lobes, the brain is highly interconnected with an
extensive fiber pathway system that connects the hemispheres, the lobes, and
provides circuits to subcortical regions.