Higher brain functions

Magdalena Gibas-Dorna

physioplus@wp.pl

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

• Between cerebral hemispheres

• Mostly thalamus and hypothalamus

Diencephalon integrates conscious and unconscious activity

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

• 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 Hypothalamus - HOMEOSTASIS

The Fornix and Parahippocampus:

The Cingulate Gyrus:

participates in the emotional reaction to pain and in the regulation of aggressive behavior

important in connecting pathways

for the limbic system

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

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

Learning and Memory

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. Long-term 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)

Storage = active process of consolidation that makes

memories less vulnerable to being forgotten

Encoding = to assign a meaning to the information to be memorized

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

PRIMING

• facilitation of recognition of words or objects by prior exposure to them

ASSOCIATIVE

LEARNING

• relation of one stimulus to another

NONASSOCIATIVE

LEARNING

• learning about one stimulus

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

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.

Eric Kandel won

the 2000 Nobel Prize for

Physiology and Medicine

for this work.

Research on neural mechanisms has focused on

non-associative learning and classical conditioning.

Aplysia

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)

CSUSUR

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

Long-term potentiation

(LTP)

Long-term depression

(LTD)

Synaptic plasticity: 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

Anterograde amnesia

Amnesia for events that occur after trauma.

Retrograde amnesia

Amnesia for events that occur just prior to the brain trauma

amnesia

– 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

The most important association areas are

Parieto-occipitotemporal association area

Prefrontal association area

Limbic association area.

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.

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.

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

Language areas of brain

• 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

• 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

• Exner’s area (6): motor writing centre • Location: middle frontal gyrus of

categorical hemisphere

Exner’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

APHASIA IS LOSS OF OR DEFECTIVE LANGUAGE it results from damage to the speach centres within left hemisphere

CATEGORICAL 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

physioplus@wp.pl