Week 11+12 - Neuroanatomy (& Neurophysiology)/ DIVA MODEL

FINAL EXAM https://create.kahoot.it/share/neuroanatomy-2024/e44d9387-15df-4cd5-a249-f4d75644d66a

How’s the nervous system (CNS) divided into?

How’s the nervous system (CNS) divided into?

• Central nervous system

  • Encased in bone

  • Cerebral cortex, cerebellum, thalamus, basal ganglia, brainstem and spinal cord

  • Made of neurons (transmit information) and glial cells (support neuron function)

• Peripheral nervous system

  • Serve peripheral body

  • Cranial nerves - serve head and neck

  • Spinal nerves - serve the rest of the body

Explain the different steps occuring in the Nervous System

1. External vs Internal receptors

2. The sensory division

3. Information processing

4. The motor division (two systems)

5. Effectors

Overview of the nervous system

How are neurons supported & how do they communicate?

• Neurons supported by glial cells (store information in long term memory) and astrocytes (help the development of synapses)

• Neurons communicate through synapse by means of neurotransmitter substance

How are neurons active?

• Excitation: increases their firing rate

• Inhibition: decreases their firing rate

What are the parts of the brain

1. Forebrain

2. Cerebellum

3. Brain stem

4. Spinal cord

General structure of each brain parts

1. Forebrain

   • Cerebrum

   • Subcortical structures

2. Cerebellum

3. Brain stem

   • midbrain, pons, medulla, cranial nerves

4. Spinal cord

Forebrain: Characterisitcs of the Cerebrum

• Outside layer of brain

• Consists of two hemispheres and corpus collosum (connects the two hemispheres)

• Divided by longitudinal fissure

  • Sulci & gyri

Forebrain: What are the Five lobes?

Frontal, Temporal, Parietal and Occipital

Forebrain: What does the Subcortical structures contain & their functions?:

• Basal ganglia: movement & movement patterns

• Subthalamus: motor funtions

• Thalamus: most sensory information

• Hypothalamus: Bodily functions, link the nervous system to the endocrine (“hormone”) system

• Limbic system:

  • Amygdala: emotional regulation

  • Hippocampus: learning, memory

Characteristic of the Cerebellum

• Largest component of hindbrain

• High Neuron density (around 80% of brain’s neurons)

What does the Brain stem consist of?

• Midbrain

• Pons

• Medulla

• 12 cranial nerves

Brain stem: Cranial nerves levels

• Nerves I-IV: midbrain level

• Nerves V-VIII: pons level

• Nerves IX-XII: medulla level

What are the 12 cranial nerves?

1. Olfactory: sense of smell

2. Optic: visual information

3. Oculomotor: Innervation for eye movement

4. Trochlear: Innervation for eye movement

5. Trigeminal: Sensory information in parts of face and tongue, chewing

6. Abducens: Movement of eyeball

7. Facial: Innervates muscles of facial expression & Sensory component for part of tongue

8. Vestibulocochlear: Mediates auditory and vestibular (gravity, balance...) sensation

9. Glossopharyngeal: Somatic sense from tongue and pharynx & Upper pharynx reflexes

10. Vagus: Autonomic function & Somatic motor innervation

11. Accessory: Collaborates with the vagus nerve to innervate the intrinsic muscles of the larynx

12. Hypoglossal: Innervates the muscles of the tongue

What does the Spinal cord contain?

31 pairs of spinal nerves

What’s Apraxia of speech/ verbal apraxia

difficulty in planning certain speech sounds

COMMON LANGUAGE IMPAIRMENTS

What’s Dysarthria?

causing difficulty pronouncing phonemes

What’s Oral dyspraxia vs Verbal dyspraxia?

• Oral dyspraxia: deficit in programming articulators for non-speech sounds

• Verbal dyspraxia: deficit in programming articulators for speech production, phoneme substitution errors, but good comprehension

What’s Dysgraphia?

failure to use visual and motor feedback

Whats’s Developmental language disorder?

problems with language development in children

What’s Dyslexia?

difficulty mapping sounds to written language and reading difficulties

What’s Aphasia?

general language impairment due to lesion/ stroke

What’s Broca’s aphasia?

difficulty in speech production

• broca: inferior frontal gyrus

What’s Wenicke’s aphasia?

syntax maintained, but meaning/ content is irregular
- Wernicke: Superior temporal gyrus

What’s Global aphasia?

both expressive and receptive abilities are severely impaired

What are causes of language impairments?

• Acquired brain injuries

  • covers all situations in which brain injury has occurred since birth, and includes Traumatic Brain Injury (TBI) as well as tumour, stroke, brain haemorrhage and encephalitis...

• Traumatic brain injury

  • Is an acquired brain injury

  • Motor vehicle accidents -> brain slams against the inside of the skull

• Mild traumatic brain injury

  • Repeated head traumas

  • Concussions

• Degenerative diseases

  • Amyotrophic lateral sclerosis (ALS)

  • Parkinson’s disease

  • Huntington’s disease

  • Myasthenia gravis (MG)

  • Bell’s pals

Imaging methods used in cognitive neuroscience

• EEG/ERP

• MEG

• PET

• fMRI

Behavioural methods used in cognitive science

DIVA MODEL

What’s conventional feedback vs feed-forward?

• Conventional feedback is past focused. It provides information about past activity and performance.

• Feed-forward is future focused. It provides information about what a person could do differently in the future.

How does the DIVE model work?

• The speech sound map of the premotor cortex controls the articulator velocity and position maps (lower left) which, in turn, control the muscles of speech.

• The output of the cortex is fed to somatosensory and auditory error-map regions responsible for monitoring the accuracy of production based on the proposed plan produced at the premotor cortex.

• The error monitoring system serve as feedback control, which modifies the output over time during learning stages.

What happens eventually?

• the feedforward control has been modified sufficiently that feedback is no longer critically essential until a perturbation occurs in the system → that requires error correction again (-> feedback loop)

• Such a perturbation could be:

  • anesthesia from dental work

  • or inserting a tube into the mouth (see lip tube experiments)

  • to a swollen lip or tongue

  • to motor disturbance arising from neuromuscular disease.

  • or simply an experiment where the auditory feedback is altered (phonetic experiments)

• For normal speech the feedback loop is turned off (otherwise speech production would be too slow) → only activated when necessary (i.e. perturbation occurs)

What’s the general requirements for a speech model?

• Feedback:

  • Auditory information (hearing your own voice and determine
    how exact targets have been reached)

  • Tactile and kinesthetic feedback (how accurately your
    production was achieved in articulation (e.g. collision control or
    precision of closure/narrow channel for plosive vs. fricative)

  • External sources (e.g. frown on someone’s face if he did not
    understand)

• DIVA model contains mirror neurons model to match production to perception (a “model” of the desired speech sound is sent from the
  premotor cortex to the perceptual regions) → if mirror neuron “model”
  does not correspond to achieved acoustic output of the muscle model
  then muscle model is modified in the next trials → but this concept is
  still highly disputed

DIVA model: Stuttering

• It takes 75 to 150 ms for auditory information to reach the
  cerebral cortex → that is too long to produce fluent running speech (e.g. an unstressed syllable is often only 100 ms long)

• So we have to disable the feedback loop for faster speech → that is the reason why we speak slower when learning new languages (learning process) → dysfluency very similar to stuttering can be achieved when we do not disable the feedback part of the model and increase the speech rate

  → in other words, in stuttering the feedback part of the model cannot be turned off, causing interference between the continuous auditory feedback and the motor planning for the following phonemes

DIVA model: Locked-in syndrome

• Sensors have been implanted in the model-appropriate regions of a young patient with locked-in syndrome (following a stroke after traumatic brain injury)

• The researchers first identified the area of the patient’s brain that was active when the patient imagined himself speaking → these regions are likely to be involved in the active production of speech

• They then implemented a “neural prosthesis” that could read activity in these regions

• These activations run a speech synthesizer based on the specific phonemes the patient is thinking of producing

• This DIVA-human combination can now successfully and consistently produce three vowels