Download Higher brain functions

Higher brain functions
Magdalena Gibas-Dorna
[email protected]
Dear Students,
• Please note that this ppt presentation presents anatomical
considerations of brain structures that are associated with higher
brain functions
• The lecture is based on Ganong’s Review of medical Physiology
• Only selected higher brain functions are presented
• The mark
indicates the most important info
• For more learning please visit:
http://neuroscience.uth.tmc.edu/s4/index.htm
„two – oval skull” includes regions of
higher functions
• Diencephalon
• Cerebellum
• Cerebral Hemispheres
Diencephalon
integrates conscious and unconscious activity
• Between cerebral hemispheres
• Mostly thalamus and hypothalamus
Thalamus
transmits sensory information
and emotional state
• Nuclei of thalamus:
– Anterior group— limbic system
– Medial group— hypothalamus
emotion center to cerebrum
frontal lobe
– Ventral group—touch and
proprioceptive information
relayed to cerebral cortex
– Posterior group—optic and
auditory information to cerebral
cortex
– Lateral group—emotional state
feedback from limbic system;
integrates with sensory
information
• Limbic system = emotional nervous system
• Higher mental functions, such as learning and formation of memories
• Structures of limbic system include: The Hippocampus
The Amygdala
The Thalamus
The Hypothalamus
The Fornix and Parahippocampus
The Cingulate Gyrus
The Hippocampus
• hippocampus is a major part of the brain involved in declarative
memory function
• transformation (not storage) of short term into long term memory
The Amygdala
integrative center for emotions, emotional
behavior, and motivation
• mediation and control of such activities and feelings as love,
friendship, affection, and expression of mood
• the center for identification of danger
• the amygdala is the nucleus responsible for fear
The Thalamus – anterior nuclear group
• connects subcortical areas and the cerebral cortex - every
sensory system (except olfactory sys) includes a thalamic
nucleus receiving sensory signals and sending them to the
primary cortical area
• Regulates sleep and wakefulness; damage to the thalamus can
lead to permanent coma
• Functionally connected to the hipocampus
• Plays role in episodic memory (events)
The Hypothalamus - HOMEOSTASIS
•
•
•
•
•
•
body temperature
water balance
circadian rhythmicity,
regulation of endocrine hormonal levels
appetite
behaviour (eg. sexuality, combativeness,
emotions)
• milk production
The Hypothalamus - HOMEOSTASIS
• Feeding reflexes—licking, swallowing, etc.
• Subconscious skeletal muscle movements—facial expressions, sexual
movements
• Autonomic center—control medulla oblongata nuclei for cardiovascular,
respiration
• Secretes oxytocin that stimulates smooth muscle of uterus, mammary
glands and prostate
• Regulates body temperature
• Controls pituitary gland by hormonal secretion—pituitary in turn regulates
many hormonal endocrine functions
• Produces emotions/sensations/drives: e.g. thirst, hunger (not really
“sensations” from periphery)
• Coordinates autonomic response to conscious input—thought of fear
produces accelerated heart rate, etc.
The Fornix and Parahippocampus:
important in connecting pathways
for the limbic system
The Cingulate Gyrus:
participates in the emotional reaction to pain
and in the regulation of aggressive behavior
Pineal gland
• Regulates Cycles
• Secretes melatonin
which helps regulate
circadian and
reproductive cycles
Cerebellum
posture and movement
• Oval at back of cranial
cavity
• Convoluted surface of
neural cortex (like
cerebrum)
• Damage leads to
“ataxia”—disturbance
of muscular
coordination
Cerebrum
(processing central for somatic/conscious information)
• Two cerebral hemispheres
separated by longitudinal
fissure (sagittal plane)
• Central sulcus divide
(coronal plane) separates
frontal lobe from parietal
lobe
• Horizontal lateral sulcus (in
transverse plane) separates
frontal lobe from temporal
lobe
• Parietal-occipital sulculs
separates parietal lobe from
occipital lobe
Cerebral function in brief
• Basal nuclei/ganglia (sometimes considered part of midbrain)
– Deep in hemispheres
– Subconscious control of skeletal muscle
– Rhythmic movements—overall walking coordination
• Frontal Lobe (primary motor cortex)-voluntary control of skeletal muscle
• Parietal lobe (primary sensory cortex)—conscious perception from skin—
touch, pressure, pain
• Occipital lobe (visual cortex)—conscious perception of visual field
• Temporal lobe (auditory cortex and olfactory cortex)—conscious
perception of sound and smell
• All Lobes—integration and processing of sensory input to initiate
conscious motor output
Find a kid
Find hidden face…
Old or young ?
Selected higher brain functions
Learning and Memory
Learning
ability to alter behavior on the basis of
experience
eg. learning/studying new language
Memory is the retention and storage of that
information
Learning and Memory
memory is ability to remember past
experiences
You learn a new language by studying it, but you then speak it by
using your memory to retrieve the words that you have learned.
Memory is the record left by a learning process
Two aspects of learning
1. acquisition of a response in presence of a
stimulus
2. suppression of responses in its absence
Types of memory
• Sensory memory is the memory that
results from our perceptions
automatically and generally
disappears in less than a second
• Short-term memory (STM) depends
on the attention paid to the elements
of sensory memory. Short-term
memory lets you retain a piece of
information for less than a minute and
retrieve it during this time (eg.
repeating a list of items that has just
been read to you, in their original
order. In general, you can retain 5 to 9
items in short-term)
• Long-term memory (LTM) includes
both our memory of recent facts,
which is often quite fragile, as well as
our memory of older facts, which has
become more consolidated. Longterm memory consists of three main
processes that take place
consecutively: encoding, storage, and
retrieval (recall) of information.
Short term memory vs. working memory
STM
• cognitive system that is
used for holding sensory
events, movements, and
cognitive information, such
as digits, words, names, or
other items for a brief
period of time
(Kolb&Wishaw, 2009)
• dorsolateral part of
prefrontal cortex (dlPFC)
WM
• maintenance and controlled
manipulation of a limited
amount of information
before recall (Baddeley,
1992)
• STM is a critical component
of WM
• dorsolateral part of
prefrontal cortex (dlPFC)
Encoding = to assign a meaning to the information
to be memorized
Storage = active process of consolidation that makes
memories less vulnerable to being forgotten
Retrieval (recall) of memories = involves active mechanisms
that make use of encoding indexes
(whether voluntary or not )
HIPPOCAMPUS & MEDIAL
TEMPORAL LOBE
• Working memory consists of central executive in the dorsolateral
part of prefrontal cortex and verbal system for retaining verbal
memories and a parallel visuospatial system for retaining visual and
spatial aspects of objects
• Prefrontal cortex has a connection with hippocampus and
parahippocampal regions of temporal cortex
Memory – forms
EXPLICIT (DECLERATIVE) memory
• associated with consciousness
• dependent on hippocampus and medial temporal lobes
IMPLICIT (NONDECLERATIVE) memory
• its retention does not usually involve processing in the
hippocampus
declarative memories can become
nondeclarative once the task is thoroughly
learned.
DECLARATIVE memory:
EPISODIC
• for events
SEMANTIC
• for facts (words, rules,
language)
NONDECLARATIVE memory:
PROCEDURAL
• skills and
habits once
acquired
become
automatic
NONASSOCIATIVE
PRIMING
LEARNING
• facilitation of
recognition of
• learning about
words or objects
one stimulus
by prior exposure
to them
ASSOCIATIVE
LEARNING
• relation of one
stimulus to
another
Forms of long-term memory
Forms of long-term memory
Nonassociative learning
• Habituation
– neural stimulus repeated many times (it evokes less and
less electrical response as it is repeated)
- generally neutral, non-noxious stimuli
• Sensitization
- repeated exposure to a stimulus
results in increased responding
to that stimulus
- the stimulus is paired once or
several times with a noxious stimulus
Research on neural mechanisms has focused on
non-associative learning and classical conditioning.
Eric Kandel and his
collaborators used Aplysia
to unravel synaptic
mechanisms for short- and
long-term habituation,
short- and long-term
sensitization, and classical
conditioning.
Aplysia
Eric Kandel won
the 2000 Nobel Prize for
Physiology and Medicine
for this work.
Habituation in Aplysia
Associative learning
classical conditioning; Pavlovian
conditioning; respondent conditioning
•A neutral stimulus is paired with a stimulus that
reliably elicits a response. Conditioning is indicated
when the previously neutral stimulus evokes a
response.
Classical conditioned reflex
• After the CS and US had been paired a sufficient number of times,
the CS produced the response originally evoked only by the US.
• The CS had to precede the US.
Meat placed in the mouth =
unconditioned stimulus (US)
Bell ringing = conditioned
stimulus (CS)
CSUSUR
bell meat saliva
CR
Respondent behavior is a characteristic of
classical conditioning that is a reflex in
response to the stimulus provided.
Operant behavior, when someone acts on the
surrounding environment to receive the
reward or punishment stimulus, is a defining
factor of operant conditioning
Associative learning
operant conditioning; instrumental learning
• a learning procedure whereby the effects of a particular behavior in a
particular situation increase (reinforce) or decrease (punish) the
probability of the behavior
operant conditioning reinforces
one's actions with reward or
punishment
Instrumental learning
Molecular basis of memory
• alteration in the strength of selected synaptic
connections that involves gene activation and
protein synthesis
Habituation
Sensitization
Synaptic plasticity:
Long-term potentiation
(LTP)
Long-term depression
(LTD)
Change in efficacy
of synapse increasing or
decreasing amount
of neurotransmitter
presynaptically or by
increasing or
decreasing amount
of AMPA receptors
(thereby making that
synapse more
sensitive)
LTP in the hippocampus:
A mammalian model for learning
typical LTP experiment
1. stimulate neuron A, record PSP from neuron B
2. stimulate neuron A tetanically (e.g. burst of stimuli @ 100 Hz)
3. record PSP from B w/test pulses at varying intervals
4. PSP augmented for several days or even up to months
5. this augmentation is what is called LTP
LTP (long term potentiation)
• rapidly developing persistent enhancement of the postsynaptic
potential response to presynaptic stimulation after a brief period of
rapidly repeated stimulation of the presynaptic neuron (increase in
Ca ions in postsynaptic neuron)
• After intense stimulation of the
presynaptic neuron, the
amplitude of the post-synaptic
neuron’s response increases.
• The stimulus applied is generally
of short duration (less than 1
second) but high frequency
• In the postsynaptic neuron, this
stimulus causes sufficient
depolarization to evacuate the
Mg2+ that are blocking the
NMDA receptor, thus allowing
large numbers of calcium ions to
enter the dendrite
• CREB plays a major role in gene
transcription, and its activation
leads to the creation of new
AMPA receptors that can increase
synaptic efficiency still further.
LTP in the hippocampus:
A mammalian model for learning
CaMKII: Calcium/calmodulin
dependent kinase II
PKA, PKC: Protein kinase A, C
CREB: cAMP-responsive
element-binding protein
Low-frequency stimulation
results in small increases in
[Ca2+] in the postsynaptic cell,
which in turn results in fewer
AMPA channels opening in
response to glutamate. This is
called low-frequency
depression and is a
mechanism for weakening
synaptic strength.
LTD (long term depression)
• decrease in synaptic strength
• produced by slower stimulation of presynaptic neurons
and is associated with a smaller rise in intracellular Ca2+
than occurs in LTP
• In the hippocampus, the role of LTD is thought to be to
return synapses that have been potentiated by LTP to a
normal level so that they will be available to store new
information.
• Elsewhere in the brain, LTD may be actively responsible
for the storage of new information, as in the cerebellum
• LTD develops when a
presynaptic neuron is active at
low frequencies (1 to 5 Hz)
without the postsynaptic
neuron’s being subjected to
strong depolarization, as it is
with LTP.
• instead of proteins such as CaM
kinase II or kinase A being
activated, enzymes called
phosphatases dephosphorylate
AMPA receptors
• this dephosphorylation of the
AMPA receptor would be to
reduce the amplitude of the
postsynaptic potential to the
normal level where it was
before LTP.
• IT is also believed that the
number of AMPA receptors
decreases during LTD
amnesia
Anterograde amnesia
Amnesia for events that occur after trauma.
Retrograde amnesia
Amnesia for events that occur just prior to the brain trauma
– Korsakoff’s syndrome
• Permanent anterograde amnesia caused by mamillary
bodies damage resulting from chronic alcoholism.
– Confabulation
• The reporting of memories of events that did not take
place without the intention to deceive, seen in people
with Korsakoff’s syndrome.
Alzheimer Disease
SIGNS: loss of short-term memory, which impedes recollection of recent
events followed by general loss of cognitive and other brain functions,
Cytopathologic hallmarks: intracellular neurofibrillary tangles (tau protein)
and senile plaques (β-amyloid peptides),
Mechanism: polypeptides form extracellular aggregates, which can stick to
AMPA receptors and Ca2+ ion channels, increasing Ca2+ influx. The
polypeptides also initiate an inflammatory response
Summary
SENSES
PREFRONTAL
CORTEX
(working
memory)
PARAHIPOCAMPAL
CORTEX
HIPPOCAMPUS
SUBICULUM
AND
ENTORHINAL
CORTEX
NEOCORTICAL
AREAS
Speach
and language
physiology
Definitions
• Language = cognitive behaviour
• Speach = the means of communication
between the two individual or group of
individuals (sensory and motor). Spoken or
written speach.
• Is there any difference between language
and speach?
American Speach-Langue-Hearing Association:
Language is made up of
socially shared rules that
include the following:
• What words mean
• How to make new words
(e.g., friend, friendly, unfriendly)
• How to put words together
• What word combinations
are best in what situations
("Would you mind moving your
foot?" or "Get off my foot,
please!")
• Speach is the verbal means
of communicating:
• Articulation
– How speech sounds are made
(e.g., children must learn how
to produce the "r" sound in
order to say "rabbit" instead
of "wabbit").
• Voice
– Use of the vocal folds and
breathing to produce sound.
• Fluency
– The rhythm of speech (e.g.,
hesitations or stuttering can
affect fluency).
Language is symbolisation of ideas, ability to
convert thought into comprehensive words
•
•
•
•
•
Speaking
Hearing
Repeating
Reading
Writing
Two hemispheres
– specialization related to handedness
• Dominant hemisphere =
Categorical hemisphere
• sequential-analytic
processes (mathematical
and scientific skills)
• reasoning
• LANGUAGE
• Lesions produce language
disorders
• Representational
hemisphere
• visuospatial relations (3D
awarness)
• identification of objects by
their form and music
awarness, art. awarness,
face recognition
• imaginaion
• Lesions produce
astereognosis
1. Name the colors which were used for writing the words within 15 sec
2. Representative hemisphere tries to name the colors, but the dominant
hemisphere analyses definitions (insists on reading the word)
Corpus callosum transfers information
between 2 hemispheres
• Categorical hemisphere
• Language
• In 96% of righthanded
individuals left hemisphere is
dominant
• In 70% of left-handers the left
hemisphere is the categorical
one
• Representational
hemisphere:
• Facial expression, intonation,
body language
Brain Areas Concerned with
Speech / Language
•
•
•
•
•
•
Wernicke’s area
Broca’a area
Speech articulation area in insular cortex
Motor cortex
Angular gyrus
Aud/Vis/Touch association areas
ASSOCIATION AREAS
These areas receive and analyze signals
simultaneously from multiple regions of both
the motor and sensory cortices as well as from
sub-cortical structures.
The most important association areas are
Parieto-occipitotemporal association area
Prefrontal association area
Limbic association area.
PRIMARY, SECONDARY AND
ASSOCIATION AREAS
PARIETO-OCCIPITOTEMPORAL
ASSOCIATION AREAS
1. Analysis of the Spatial Coordinates of the Body.
2. Area for Language Comprehension.
3. Area for Initial Processing of Visual Language (Reading).
4. Area for Naming Objects.
Language areas of brain
Broca's Area - special region in the frontal cortex; word formation.
Located partly in the posterior lateral prefrontal cortex and partly in the premotor area.
Wernicke's language comprehension center - in the temporal association cortex
• Broca’s area (44, 45): anterior speach
area
• Location: 3rd frontal gyrus
• Detailed and coordinated pattern of
vocalization
• Wernicke’s area (22): posterior speach
area
• Location: at the posterior end of the
uperior temporal gyrus
• Comprehension of the auditory and
visual information
Exner’s area
• Exner’s area (6): motor writing centre
• Location: middle frontal gyrus of
categorical hemisphere
• Dejerine’s area (39)
• Location: angular gyrus
• processes information from the read words that they can be
converted into auditory forms of the words in Wernicke’s area
Dejerine’s area
Language areas of brain
(Dejerine’s area)
• Path taken by
impulses when a
subject names a
visual object
projected on a
horizontal section
of the human brain
Dejerine’s area
Auditory Language Perception
Visual Language (Reading)
(Dejerine’s area)
Interesting facts
In individuals who learn a second language in adulthood, fMRI reveals that
the portion of Broca’s area concerned with it is adjacent to but separate from
the area concerned with the native language
How about children?
STEPS OF COMMUNICATION
Steps of Communications
Collection of sensory input: Auditory and visual
Integration: hearing and articulation mechanism
Motor execution
SPEECH PRODUCTION PROPCESS
Speach/language disorders
APHASIA
CATEGORICAL HEMISPHERE
APHASIA IS LOSS OF OR DEFECTIVE LANGUAGE
it results from damage to the speach centres within left
hemisphere
Please note that:
In aphasia there is on lesion in vision,
hearing, or motor areas of brain.
Nonfluent aphasia
• Nonfluent aphasia (motor aphasia) – Broca’s
area
• Speech is slow, and words are hard to come by
Fluent aphasia
• Fluent aphasia - it was thought to be due to
lesions of the arcuate fasciculus connecting
Wernicke’s and Broca’s areas
• lesions in and around the auditory cortex
• speech itself is normal and sometimes the
patients talk excessively. However, what they say
is full of jargon and neologisms that make little
sense
Fluent or Receptive (Wernicke’s
Aphasia)
• Patients with Wernicke’s Aphasia usually have
great difficulty understanding speech, even
though there is no deafness.
• They may speak fluently, often in long
sentences, but the meaning of their sentences
is unclear. (“fluent paraphasia”).
Conduction Aphasia (form of fluent
aphasia)
• Patients may be able to understand speech as well as
produce meaningful speech, but have difficulty
repeating a spoken sentence.
• patients can speak relatively well and have good
auditory comprehension but cannot put parts of
words together or conjure up words
• Often associated with damage to the Arcuate
Fasciculus, which connects Wernicke’s area with
frontal pre-motor structures.
The Arcuate Fasciculus
Big fibre bundle connecting Broca’s and Wernicke’s Areas
http://www.biocfarm.unibo.it/aunsnc/pictef14.html
Anomic aphasia
• Location: the angular gyrus in the categorical
hemisphere without affecting Wernicke’s or
Broca’s areas
• there is no difficulty with speech or the
understanding of auditory information;
instead there is trouble understanding written
language or pictures
Agnosia
Have we met?
Agnosia
• inability to recognize objects by a particular sensory modality
even though the sensory modality itself is intact
• Parietal lobe
• Unilateral inatension, when lesion is in representational
hemisphere (right one)
Thank you!
Magdalena Gibas-Dorna
[email protected]