Higher functions

Language (Speech)

It is expression of thoughts and ideas through production of sounds.

To understand the spoken and printed words and to express idea in speech and writing is called language.

Speech Pathway

Printed words will be seen by the primary visual area

Words are interpreted by the visual association area

These words are converted into internal words by the Dejerine area (angular gyrus)

These words are then interpreted by Wernicke’s area

Broca’s area will coordinate

Motor area for the spoken speech

Exner’s area (motor writing centre)along with motor area to initiates appropriate muscle movements of hand and fingers to written speech

Pathway for Spoken and Written speech

Speech disorders

• Aphasia: abnormalities of speech functions

• Types:

1. Sensory aphasia

2. Conduction aphasia

3. Motor aphasia

4. Global aphasia

Learning and memory

• Learning and memory are two important higher functions of the nervous system.

• Learning means to gather experience or knowledge

• Memory is to retain this knowledge for future use

Learning

• Conditioned reflex - Important for learning • Unconditioned reflex or inborn reflex

• Pavlov’s classical dog experiment

• Types of conditioned reflex1. Operant conditioning :An animal learns to repeat a

behavior which is rewarding or to avoid a behavior associated with punishment.

2. Discriminate conditioning: Animal is taught to discriminate between different signals with great accuracy.

Basis of conditioned reflex

• Development of new connection in the nervous system

• Synaptic plasticity

Memory

• Memory is the ability to store what is learned or experienced and can be recalled in need.

. Memory systemsTypes of declarative and nondeclarative memory

Declarative: easy to form and easily forgottenNondeclarative: require repetition and practice over a long period, but less likely to be forgotten

Types of Declarative MemoryShort-term (seconds to hours) and long-term memory

Definitions• Short-term declarative memory

• 1. temporary, limited in capacity, requires repetition

• Long-term declarative memory

• 1. more permanent, large capacity, does not require repetition

• 2. consolidation = process of retention in long-term memory

I. Inferotemporal Cortex

• A. Visual association area )

• B. Experimental lesion studies

• 1. loss of visual discrimination task

• 2. basic vision normal

• 3. loss of memory

Inferotemporal Cortex (area IT)

• C. Face recognition neurons

• 1. face selectivity

• 2. facial memory

II. Temporal Lobe & Memory• 5. connections

• A. inputs: all sensory association areas

• B. outputs: hypothalamus via fornix

III. Papez circuit

•

IV. Prefrontal Cortex

Prefrontal Cortex• Hypothesized functions

1. complex planning

• 2. problem solving

• 3. memory

Memory

• Short-term:– Memory of recent events.

• Medial temporal lobe: – Consolidates short term into long term

memory.

• Hippocampus is critical component of memory.

• Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.

Long-Term Memory

• Consolidation of short-term memory into long-term memory.– Requires activation of genes, leading to protein synthesis and

formation of new synaptic connections.• Altered postsynaptic growth of dendritic spines in area of contact.

• Cerebral cortex stores factual information:– Visual memories lateralized to left hemisphere.– Visuospatial information lateralized to right hemisphere.

• Prefrontal lobes:– Involved in performing exact mathematical calculations.

• Complex, problem-solving and planning activities.

Long-Term Potentiation

• Type of synaptic learning.– Synapses that are 1st stimulated at high frequency will

subsequently exhibit increased excitability.• Postsynaptic changes:

– Glutamate binds to NMDA and AMPA receptors.– Opens Ca2+ and Na+ channels.

• Presynaptic changes:– Ca2+ causes, release of NO from postsynaptic neuron.– NO acts as a retrograde messenger, causing release of

NT in bouton.

Amnesia = loss of memory and/or the ability to learn

A. Retrograde amnesia

• loss of memory prior to trauma

B. Anterograde amnesia

• loss of ability to form new memories after trauma

Alzheimers disease

• Degenerative changes in various parts of CNS

• Amyloid plaques

• Senile dementia