Brain functions

1
Brain functions

• a specific function (e.g. speaking) does not
  activate the entire brain
• brain functions are represented in specific
  regions of the brain

2
Neuropathological examination

• without the left inferior frontal gyrus, speech
  production is impaired / impossible
• left and right hemispheres have different
  functions

3
MRI

• functions like a mobile phone
• contains transmitter and receiver
• electromagnetic energy is transmitted into the
  patient
• the body interacts with those elecromagnetic
  fields
• energy is sent out

4
fMRI - tongue movement
5
For clinical use

• functional neuroimaging will (most likely) not be
  a diagnostic tool
• diagnoses we make are clinical
• functional neuroimaging is an excellent tool to
  monitor the neural correlates of brain recovery
• can provide evidence for the effectiveness of
  therapies, e.g. speech-language therapy,
  physiotherapy etc.

6
Speech Science

• Somatosensory System

7
Motor control

• Necessary for successful reaching / grasping
• somatosensory control
• visual control

8
Speech motor control

• somatosensory feedback
• position of the vocal folds? -gt muscle receptors
• position of the mandible? -gt joint receptors
• pressure of the tongue against the teeth? -gt
  mechanoreceptors
• auditory feedback

9
Sensation

• Superficial sensation
• skin, mucosa (oral and nasal cavities)
• Deep sensation
• muscles, joints
• Visceral sensation
• e.g. esophagus

10
Receptors
sensory stimulus
mechanorecetors nociceptors thermoreceptors
receptor
proprioceptors
electric impulses
response
subjective experience
response
11
Mechanoreceptors

• different types of receptors in the skin
• specialized cells (mechanoreceptors)
• free neve endings (pain)

12
Muscle spindles

• Receptors that provide proprioceptive feedback
  for the movement, position and extension of
  muscles.
• The spindle is composed of specialized
  intrafusal muscle fibres.
• Intrafusal muscle fibres are arranged in parallel
  with extrafusal muscle fibres.
• Spindle muscle fibres are entwined by sensory
  fibres.
• Spindle muscle fibres are innervated by small
  (gamma) motor neurons.

13
Muscle spindles

• When muscle is passively stretched or loaded, the
  muscle spindle fibres are also stretched
• This distorts the sensory fibres wound around the
  spindle fibres, causing them to produce action
  potentials
• Activation of these sensory fibres results in
  activation of the motor neurons innervating the
  extrafusal muscle. Thus, the muscle contracts in
  response to the muscle stretch.

14
Spinal nerves

• anterior root motor
• posterior root sensory

15
Sensory ganglion
16
Trigeminal nerve

• 3 sensory branches
• unite in the trigeminal ganglion
• motor branch
• innervates jaw closers

17
Sensory pathways

• cranial nerve
• secondary sensory neurons
• thalamus
• somatosensory cortex

18
Thalamus

• the central sensory filter

19
Oropharyngeal stimulation

• bilateral stimulation (A)
• left stimulation (B)
• right stimulation (C)
• in all conditions, activation of both hemispheres

20
Speech control

• motor pathways (black)
• sensory pathways (green)

21
Homunculus

• postcentral gyrus primary somatosensory cortex
• body regions are represented in a certain order
  in the primary somatosensory cortex
  somatosensory homunculus
• very similar to the motor homunculus

22
Sensory disorders

• Peripheral sensory disorder
• mono- / polyneuropathy disorder of one or more
  peripheral nerves
• rare in the orofacial region
• Central sensory disorder
• stroke, multiple sclerosis
• orofacial region is often spared or only mildly
  affected

23
Lateralization

• somatosensory and motor functions for the limbs
  are represented in the contralateral hemisphere
• left-hemispheric stroke -gt right hemiparesis,
  right-sided sensory deficit
• somatosensory and motor functions for the
  orofacial region are represented in both
  hemispheres
• left-hemispheric stroke -gt facial muscles and
  facial sensation are less affected than the
  limbs usually the facial paresis recovers faster

24
Auditory system
25
Auditory system

• understand what others are saying (speech
  comprehension)
• monitor what we are saying (feedback)

26
Auditory feedback

• interaction between auditory and motor system
• similar in playing an instrument and producing
  speech

27
Ear
28
Auditory pathways

• contralateral and ipsilateral