lecture of Associational Cortex in detail.pdf

Overview
of
Associational
Cortex
•
Spring
2013

1
Medical
Neuroscience
2013
|
Tutorial

Overview
of
Associational
Cortex

MAP
TO
NEUROSCIENCE
CORE
CONCEPTS
1

NCC5.
Intelligence
arises
as
the
brain
reasons,
plans,
and
solves
problems.

NCC7.
The
human
brain
endows
us
with
a
natural
curiosity
to
understand
how
the
world
works.

LEARNING
OBJECTIVES

After
study
of
the
assigned
learning
materials,
the
student
will:

1. Characterize
the
behaviors
and
corresponding
neural
processes
that
contribute
to
cognition.

2. Discuss
the
major
similarities
and
differences
in
the
organization
of
primary
cortex
and

associational
cortex.

TUTORIAL
OUTLINE

I. Introduction
to
the
neuroscience
of
cognition

A. lay-‐person’s
definition
of
cognition:
the
process
of
knowing

B. neurobiological
definition:
the
neural
processes
by
which
the
brain
integrates

meaningful
stimuli,
memory,
and
internal
motivations
producing
perceptional

awareness
and
appropriate
behavior

C. Table
1.

Neural
processes
that
contribute
to
cognition

Cognitive

process
Metaphor
/
Example
Neural
Process

Attention
cognitive
“search
light”
modulatory
influences
of
brainstem
reticular
formation,

hypothalamus
and
basal
forebrain
nuclei
on
thalamic
and
cortical

processes

Recognition
finding
a
friend’s
face
in
a
crowd
coding
of
feature
representations
in
primary
and
higher
order

sensory
cortices

Integration
knowing
that
friend
integration
(“association”)
of
disparate
processing
streams
in

associational
cortices

Planning
deciding
to
seek
out
that
friend
processing
in
executive
associational
cortices
in
prefrontal
cortex

of
frontal
lobe

Selection
&

execution

Walking
towards
that
friend
and

engage
in
conversation

implementation
of
short-‐term
and
long-‐term
plans
via
somatic

motor,
visceral
motor
and
emotional
motor
systems

1

Visit
BrainFacts.org
for
Neuroscience
Core
Concepts
(©2012
Society
for
Neuroscience)
that
offer
fundamental
principles

about
the
brain
and
nervous
system,
the
most
complex
living
structure
known
in
the
universe.

Overview
of
Associational
Cortex
•
Spring
2013

2
II. Anatomy
of
the
Associational
Cortex

A. review
of
cortical
structure
and
function

1. “canonical”
(i.e.,
standard/representative)
cortical
microcircuit

a. the
columnar
circuit
is
the
fundamental
unit
of
processing
and

computation
in
the
complex
circuitry
of
the
cerebral
cortex

b. within
a
cortical
column,
different
types
of
excitatory
and
inhibitory

neurons
populate
distinct
cellular
layers

(i) the
main
excitatory
neurons
are
pyramidal
neurons

(ii) the
inhibitory
neurons
are
diverse
morphologically
and

functionally

c. each
layer
maintains
distinct
sets
of
inputs
and
outputs

(i) pyramidal
neurons
project:

- to
other
neurons
in
the
same
layer
and
across
layers

within
the
local
column

- to
other
columns
in
the
same
cortical
area

- to
other
columns
in
other
cortical
areas,
including
the

corresponding
area
in
the
opposite
cerebral
hemisphere

- to
subcortical
targets
(e.g.,
corticospinal
tract
neurons)

(ii) most
inhibitory
neurons
project
locally
within
their
home
layer

and
column,
but
some
do
project
across
cortical
columns
within

the
same
area
(few
project
to
other
areas;
very
few
if
any

project
to
the
other
hemisphere
or
subcortically)

B. distribution
of
associational
cortex
(see
Figure
26.12
)

1. only
about
25%
of
the
cerebral
mantle
is
comprised
of
primary
sensory
and

motor
cortex;
the
remaining
75%
is
termed
associational
cortex

2. with
the
possible
exception
of
the
occipital
lobe
(which
is
largely
if
not
entirely

devoted
to
increasingly
complex
aspects
of
visual
processing),
all
other
lobes

contain
associational
cortex

3. as
its
name
implies,
the
associational
cortex
integrates
(or
associates)
different

types
of
inputs,
some
of
which
come
from
primary
and
higher
order
sensory

cortex

4. it
is
in
the
associational
cortices
that
most
of
the
neural
processes
of
cognition

are
carried
out
(together
with
interactions
among
subcortical
neural
centers)

C. differences
between
associational
cortex
and
primary
cortex
(see
Figure
26.4)

1. unlike
primary
cortices,
which
receive
their
main
input
from
specific
sensory
and

motor
relay
nuclei
of
the
thalamus,
the
associational
cortex
receives
its
most

influential
input
from
other
parts
of
the
cortex

2

Figure
references
to
Purves
et
al.,
Neuroscience,
5
th

Ed.,
Sinauer
Assoc.,
Inc.,
2012.
[click
here]

Overview
of
Associational
Cortex
•
Spring
2013

3
2. associational
cortex
does
receive
input
from
thalamus,
but
it
arises
from

thalamic
nuclei
(pulvinar,
posterior
nuclei,
and
mediodorsal
nucleus)
that
are

themselves
driven
by
highly
processed
“feedback”
projections
from
the
cortex

(rather
than
from
“feedforward”
sensory
systems)
(see
also
Appendix
BoxA)

3. other
sources
of
input
come
from
brainstem
modulatory
systems:

a. noradrenergic
cells
of
the
locus
coeruleus

b. serotonergic
cells
of
the
Raphe
nuclei

c. dopaminergic
cells
of
the
ventral
tegmental
area)

4. and
from
the
basal
forebrain:

a. cholinergic
cells
in
the
basal
nucleus
of
Meynert

STUDY
QUESTION

Cognition
is
an
emergent
property
of
brain
function,
reflecting
(as
Charles
Sherrington
famously
put
it
a

century
ago)
the
integrative
action
of
the
nervous
system.

Nevertheless,
it
is
useful
to
identify
and
study

distinct
neurobiological
mechanisms
that
support
disparate
functions
that
contribute
to
cognition.

Which
cognitive
process
is
attributable
to
the
functions
of
brainstem
modulatory
(biogenic
amine)

systems?

A. selection
and
execution
of
short
and
long-‐term
plans

B. integration
of
disparate
processing
streams

C. recognition
and
coding
of
salient
features

D. attentional
modulation
of
sensory
processing

E. planning
appropriate
behaviors

lecture of Associational Cortex in detail.pdf

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