Transcript Neurocognition Cognitive Neuroscience/neuropsychology

Neurocognition
Cognitive Neuroscience/neuropsychology

All cognition is the result of neurological
activity
– most closely linked to cerebral cortex
The study of the relationships between
neuroscience and cognitive psychology,
especially those theories of the mind
dealing with memory, sensation and
perception, problem solving, language
processing, motor functions and cognition
The relationship between brain
and cognition


Cognition is a product of the brain.
Understanding the brain and its organization
is useful for assessing the plausibility of
cognitive theories
neural basis of cognition
can be considered at two levels of
description…
a) neuronal - one or a small collection of
individual neurons
b) neural systems - a large number of
neurons that serve a similar function
(localization of function); usually referred
to by a collective name (e.g., cortex,
temporal lobe, etc.)

Major regions of cerebral cortex




frontal lobes - motor activity, planning &
moving, processing of affective info.,
spoken language (Broca' s area)
temporal lobes - audition, language
perception (Wernicke' s area)
parietal lobes - somatosensation, spatial
perception
occipital lobes - vision
Brain & Cerebral Cortex
Topographical organization

one-to-one correspondence between a point
or location in an external system, such as
the retina, and a point or location in the
brain
– e.g., motor cortex, occipital lobes
Neurons - Structure

Basic building block of nervous system
– soma - cell body; contact site for other neurons
– dendrites - contact site for other neurons
– axon - conducts action potential away from cell
body & dendrites towards other neurons
– terminal buttons - at end of axon; site of
connection to other neurons
– myelin sheath - electrical insulation (optional)
neuronal functioning


Action potential - how neurons convey
information; an electrochemical
transmission along length of neuron
Synapse - site of “connection” between
adjacent neurons or between neurons and
muscle fibers
– Terminal buttons of presynaptic neuron @
dendrites/soma of postsynaptic neuron (or
muscle fibres)
neurotransmitter

Transmitter substance - chemical produced
by a neuron that enables it to affect an
adjacent neuron or group of muscle fibres
– Excitatory synapse - increases likelihood of
AP in post-synaptic neuron
– Inhibitory synapse - decreases likelihood of AP
in post-synaptic neuron
neural representation of
information


each neuron is connected to many other
neurons (1:1000)
representation of information is due to the
pattern of activation across many neurons
(i.e., a concept or idea does not correspond
to a single neuron)
– permanent memories are coded by long-term
synaptic changes (rate of presynaptic NT
release, re-uptake, & postsynaptic dendritic
sensitivity)
Compartmentalization vs. Mass
Action



Phrenology - exact location specific,
measured by bumps on the head
Compartmentalization - some
functions,m such as motor activitiy, are
associated with a specific area of the
brain
Aggregate Field Theory - functions also
distributed in other brain areas
Currently believed it is a little of both
Anatomy of Brain



Review Structures of Forebrain,
Midbrain and Hindbrain
Contralateral actions
Karl Lashley - localization vs.
generalization of function research
– theory of mass action

Current Models of neural processing?
Now...


Field of Neuroscience given big boost
by development of techniques that allow
us to peer into the human brain and
reveal structures and processes never
seen before.
The mostly noninvasive tools are
possible due to advances in computer
technology and brain scanning
techniques
Then...




Excising of tissue
Electrical probes
EEG recordings
postmortem exams
Magnetic Resonance Imaging

a method of scanning the brain that
produces detailed maps of brain
structure without X-rays or other
radiation by relying on the difference in
the magnetic resonance of certain
atomic nuclei.
MRI



body surrounded by electromagnets
that align the nuclei of hydrongen atoms
found in water.
Since hydrogen reflects water content,
can infer varying densities of tissue
Good for static measures, but not for
rapidly changing cognitive functions
Functional MRI (fMRI)



New method, capable of high-resolution
images of functional activity in the brain
scan in 30 milliseconds
giant magnet surrounds the subject's
head
– Changes in the direction of the magnetic
field induce hydrogen atoms in the brain to
emit radio signals. These signals increase
when the level of blood oxygen goes up,
indicating which parts of the brain are most
CAT Scans



Computerized Axial Tomography
X-ray machine rotates around skull,
sending tons of thin, fan-shaped x-ray
beams that are recorded on detectors
on the opposite side of their source
used to display cognitive structures
PET


Positron Emission Tomography
a type of scan that measures changes
in blood flow associated with brain
function by detecting positrons,
positively charged particles emitted by
radioactively labeled substances that
have been injected into the body.
PET

Left - Subject
Reading words

Right - Subject
hearing Words
PET


Since brain activity involves an increase
in blood flow, more blood—and
radioactive substance—streamed into
the areas of the volunteers' brains that
were most active while they saw or
heard words.
High costs, time for image recording is
too long (20 seconds)
fMRI vs. PET

BOTH: blood flow to brain provides the
signals detected
– when resting neurons become active,
blood flow to them increases


fMRI - detects changes in oxygen
levels, which rise in nearby blood
vessels when they are at rest
PET - relies on increased delivery of
injected radioactive water, which
diffuses out of the vessels to reach rest
of brain
Next Generation of Scans...


Messages from the senses travel so
swiftly through the brain that imaging
machines such as PET and fMRI can’t
really keep up with them.
To track these messages in real time,
scientists now use faster methods electrical recording techniques such as
MEG (magnetoencephalography) or
EEG (electroencephalography).
MEG and EEG


MEG - a technique for recording
electrical signals from the brain based
on changes in magnetic fields.
EEG - the recording of brain waves by
means of electrodes attached to the
skull.
Next Generation of Scans...

These techniques rely on large arrays of
sensors or electrodes that are placed
harmlessly on the scalp to record the
firing of brain cells almost
instantaneously. Their data may then be
combined with anatomical information
obtained by structural MRI scans.