Download Structure-Function I

Structure-Function I
The Cerebrum
Reading:
BCP Chapter 7/7A
Major Divisions of the Brain
Cerebrum
Brainstem
Divisions are based on developmental origins; they do not sub-serve discrete
functions.
The Cerebrum
A frontal section of the forebrain
reveals that the telencephalon
(cerebrum) surrounds the paired
lateral ventricles, whereas the
diencephalon surrounds the third
ventricle.
telencephalon
The cerebrum comprises three
different areas:
• outer area of neuronal cell
bodies (called gray matter or
cerebral cortex)
• inner area of myelinated
axons (called white matter)
• subcortical areas of gray
matter
diencephalon
Neocortex 1
Most areas of cerebral cortex are
organized in a similar manner
(called neocortex): 6 layers deep;
in total, 2-4 mm thick
•
•
•
•
•
layer 1, synaptic integration
layers 2 and 3, input/output to other
cortical areas
layer 4, input from thalamus
layer 5,output brainstem/spinal cord
layer 6 output to thalamus
Features:
•
•
•
•
layers differ in thickness, cell density
and type
pyramidal cells (output neurons;
excitatory) vs stellate cells (local
circuit; both excitatory and inhibitory)
vertical axons and dendrites give
rise to columnar organization
layer thickness differs from brain
area to area
Neocortex 2
Based on cytoarchitectural
grounds (as observed in Nissl
stained material), the German
anatomist Korbinian Brodmann
defined upwards of 50 distinct
regions of neocortex (1909).
Brodmann areas have been
discussed, debated, refined, and
renamed exhaustively for over a
century but remain the most
widely known and frequently cited
map of human cortex.
Brodmann postulated that these
areas with different structures
performed different functions.
lateral view
medial view
Neocortex 3
Many of the areas Brodmann
defined based solely on their
neuronal organization have since
been correlated closely to diverse
cortical functions. For example,
Sensory
• 1-3: primary somatosensory
• 17: primary visual
• 34: part of primary olfactory (most
olfactory cortex is not neocortex)
• 41-42: primary auditory
• 43: primary taste (gustatory)
Motor
• 4: primary motor
• 6: supplementary motor
Association
• 39-40: language comprehension
(Wernicke’s area)
• 44-45: speech production (Broca’s)
Wernicke’s area
(areas 44, 45)
Broca’s area
(areas 44, 45)
Neocortex is commonly described as
comprising three parts: sensory, motor,
and association (higher-order) areas.
Neocortex 4
Brodmann areas and cortical functions also correlate well with gross anatomical
features of the forebrain.
Primary motor cortex
Central sulcus
Primary somatosensory cortex
Supplementary motor
Frontal lobe
Broca’s area
Wernicke’s area
Primary visual
Primary auditory
Superior temporal gyrus
White Matter 1
White matter is composed of bundles
of myelinated nerve cell axons,
which connect various gray matter
areas of the CNS to each other.
There are three types of fiber tracts:
•
•
•
association – connect gyri in same
hemisphere (short and long)
commissural – connect corresponding
gyri in opposite hemispheres
projection – connect cerebrum with other
parts of brain and spinal cord
White Matter 2
White matter fiber tracts connect
gray matter areas of the CNS to
each other.
Within the three types of tracts,
major bundles include:
Association
• short (arcuate) fibers: primary
somatosensory with primary motor
• long (fasciculus) fibers: connect
Wernicke’s and Broca’s areas
Commissural
• corpus callosum
• anterior
Projection
• corona radiata
• internal capsule
 sensory input from thalamus
 motor output to spinal cord
Subcortical Areas 1
Below the cerebral cortex are
a variety of other structures,
called subcortical (literally
"below the cortex") structures.
Collectively, there are three
main groups, but not all the
nuclei in each group serve the
same function.
The three groups organized
roughly anterior to posterior
(and medial to lateral) are the:
• basal forebrain
• basal ganglia
• limbic system
Basal
forebrain
(memory)
Subcortical Areas 2
The basal forebrain is a collection
of structures located to the front
of and below the thalamus (rostral
to the hypothalamus). It includes
a number of structures including
the nucleus accumbens and the
nucleus basalis.
Nucleus
accumbens
The nucleus accumbens plays a
significant role in the cognitive
processing of motivation and
reward learning, and in addiction.
The nucleus basalis plays a role
in the sleep-wake cycle and
learning and memory (this
nucleus undergoes damage in
Alzheimer’s disease).
Nucleus
basalis
(memory)
Subcortical Areas 3
The basal ganglia include several
subcortical nuclei, including the
caudate and putamen (together
called the striatum) and the globus
pallidus, all lateral to the thalamus.
Other components include the
subthalamus (diencephalon) and
substantia nigra (mesencephalon).
The basal ganglia plays a role in
the selection of which of several
motor actions to execute at any
given time. Damage to the basal
ganglia can lead to Parkinson’s or
Huntington’s disease.
Subcortical Areas 4
The limbic system is a set of brain
structures located on both sides of the
thalamus. Major components include:
Cerebral cortex:
• hippocampus (not neocortex)
• cingulate cortex
Subcortical
• amygdala
• septum
Diencephalon
• hypothalamus
• mammillary bodies
• anterior nuclei of thalamus
The structures of the limbic system
are involved in basic motivations (in
particular, hypothalamus), emotion
(amygdala), learning and memory
(hippocampus)
StructureFunction: Cerebrum