Nervensystem II: ausgewählte Kapitel

= degenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem/spinal chord

• Symptoms: progressive weakness, atrophy, hyperreflexia, dysphagia, paralysis of respiratory function
• Pathophysiology: motor neurons are replaced with fibrous astrocytes and anterior spinal nerve roots and corticospinal tract atrophy. 
• Could be due to the dysregulation of axon guidance proteins -> denervation of neuromuscular junctions

= the ability of the brain to optimize or maximize performance through differential recruitment of brain networks or the usage of an alternative strategy:

2 proposed mechanisms:

1. neural reserve
2. neural compensation

1. motor noise: motor neurons, muscles -> variations in execution
2. cellular noise: ion channels, synaptic transmission -> difference in cells
3. sensory noise: -> the transformation of an external stimulus into an AP, certain insecurity there
4. noisy external sensory stimuli: Thermodynamic, quantum mechanical

• you present 2 tonal pairs of the same pitch. The subject must then say which has a higher pitch (an impossible task)
• but due to the imperfect treatment of the information, the subject perceives the tones at different pitches.
• mithilfe von neuroimaging konnte man feststellen, dass der rechte superior temporal gyrus 100ms für den brain noise verantwortlich war -> moduliert die wahrgenommene Tonhöhe
  • Internal noise is perceivable and it influences perception

Sie haben das internal brain noise untersucht, indem sie ein internes prediktives modell aufgebaut haben mithilfe von Tönen

Bei dem Omission eines brain tones wurde dennoch eine Antwort im Gehirn gemessen -> self generated brain activity driven by the expectation that a sound will be generated -> arbeitet gegen den Gehirnlärm und verbessert die Präzision 

Experience-based predictions generate brain activity as would physically real events as well

The voltage is generated by excitatory postsynaptic potentials of massively synchronized pyramidal cells:

• a single neuronal event is too small to be detected on the scalp
• synchronisation is important

= transcranial direct current stimulation

- two electrodes run a weak, constant electric current through the brain (1-2mA) 

- induces focal changes of cortical excitaility 

• anodal stimulation: excitatory effect (AN)
• cathodal stimulation: inhibitory effect (KABUTT)

= transcranial magnetic stimulation

- can also be either excitatory or inhibitory

- repetitive TMS -> the effect can outlast the stimulation

- simultaneous stimulation of more than one are is possible using several coils

- produces a more focal electrical field

1. A1 -> Wernicke's area (language comprehension) -> Broca's area (Speech production, initiation of speech) -> M1

2. V1 -> Angular gyrus (copmrehension) -> Wernicke's -> Broca -> M1

Wernicke Aphasia: You lose language comprehension. You can't understand anyone and what you say makes no sense -> flüssige Aphasie

Broca Aphasia: can't produce speech -> nicht-flüssige Aphasie

1. Shifting: task/-mind sets -> Regeln
2. Updating (working memory) -> information
3. Inhbiting: cognitive and motor processes

- Man gibt einem Kind ein Marshmallow, es muss dem widerstehen können während 10min widerstehen können und dann erhält das Kind einen 2. Marshmallow, sonst nicht. 

- benötigt self-control (executive function): gain a larger but delayed rewards over a smaller but more immediate reward. 

- Higher self-control ist assoziiert mit besseren IQ, und besseren akademischen Entwicklungen

Top down causes:

1. negative moods
2. resource depletion
3. PFC damage
4. alcohol consumption

Bottom up causes:

1. cue exposure
2. lapse activated consumption

= die Idee ist es, den PFC zu bestärken -> Motor inhibitory training with Go/NoGo tasks

• respond as fast as possible to Go tasks and withhold response in NoGo stimulus
• right inferior frontal gyrus (rIFG) -> inhibits motor commands via projections to the Basal ganglia (Subthalamic nucleus)

• all ypes of inhibition rely on the same IC mechanism

GNG training does not reinforce IC, if the stimulus is always the same -> development of automatic, feed-forward, stimulus dirven, bottom up form of inhibition --> Reflexes. No longer requires voluntary initiation of inhibition (association etween NoGo stimulus and inhibition command)

Associative IC training -> devaluation of trained NoGo stimuli

Varying NoGo Stimli: 

- prevents associative learnng

- leads to modification of domain-general IC-Network

- intentional inhibition is systematically required --> rIFG is modified (structural grey and white matter) -> strong anatomical connectivity between IFG and BG is the key to sustained supranormal self control -> all types of IC are imporved because they rely on domain general structures. Ideal example: martial arts

= multisensory enhancement is inversely related to the effectiveness of the individual cues that are being combined

Bei der Wahrnehmungsgrenze ist die integration verhältnissmässig am grössten.

= Die MSI ist am grössten, je näher die stimuli auftreten. Schickt man visuelle und auditive stimuli genau gleichzeitig ist die MSI am grössten. Je grösser die Phasenverschiebung, desto kleiner die Integration

= MSI ist am grössten, wenn die loci von verschiedenen Modalitäten mit den rezeptiven Felden und diese auch untereinander überlappen --> Wenn ein visueller und auditiver stimulus vom gleichen Ort kommen -> bessere Integration

1. Stimuli from 2 or more sensory modalities
2. multisensory integration: neural processes, which are involved in synthetizing info from cross-modal stimuli
3. Multisensory enhancement: A situation where the response to cross-modal stimuli is greater than the response to the most effective of its component stimuli
   • super-additive combinations
   • equal = additive

dorsal pathway (hoher Weg): Where system

• identifizieren, wo sich Objekte im Raum befinden

Ventral pathway (tiefer Weg): Was System

• Identifikation von Objekten

You are up high when you need to find something(where) and go below to see what exactly it is.

Auditory, visual and somatosensory:

• principal sulcus
• ventral premotor cortex
• ss areas 1 nd 3b
• ventral intraparietal area
• temporoparietal area
• superior temporal sulcus
• auditory core and lateral belt area

PV SV TSA

auditory and visual:

• ventrolateral prefrontal cortex
• lateral intraparietal area
• primary and secondary visual areas

Very Large Portion

Auditory and somatosensroy:

• caudiomedial auditory belt area
• visual areas middle temporal (MT)

Curriculum vitae

• Vision dominates over hearing (audiovisual effect)
• the visual information a person gets while hearing a person speak and seeing their lips move influences their perception of the sound
  • BaBaBa sound and seeing the appropriate lips -> perception of BaBaBa
  • BaBaBa sound and seeing the lips say FaFaFa -> perception of FaFaFa
  • The visual information is not in line with the auditory -> it dominates over the auditory. 

audio-visual effect

• person with a puppet
• you see the puppets lips move, but not the persons
• you interpret the sound to be coming from the doll --> visual also here dominates over auditory

- place your left hand out of sight and now also a rubber hand in sight. 

- stroke both hands (real and fake) simultaneously in the same direction -> start to perceive the rubber hand as your own

Space: vision > touch > audition

Time: audition > touch > vision

= participants respond more often to the visual component of an audiovisual stimulus, when presented with a bimodal stimulus -> provides evidence for the visual dominance in humans. 

1. direct feedforward from sensory areas to vFP
2. indirect influences of multisensory signals in FP network
3. direct projections between sensory-specific areas
4. subcortical structures

1. Developmental differentiation view:
   1. low level basic, multisensory integration present at birth
2. Developmental integration view:
   1. multisensory skills are absent at birth
   2. emerge and imporve slowly with increasing sensorimotor experience

• before 8, children do not integrate information between the senses, one merely dominates the other
• after a time, the more robust one educates the other

Older age:

• older adults have greater MSI (not better) than young adults
• reduced sensitivity in unisensory systems increases the inverse effectiveness effect
• have a larger time window integration -> less precise MSI

• Non-autistic subjects focus more on linguistic stimuli

Autistic subjects:

• focus more on non-linquistic stimuli
• have impairments in audiovisual integration -> McGurk effect is weaker: seeing the person say somehting makes less of a difference
• have a larger temporal integration window (binding impairment)-> less temporally precise integration (it is better to have focalized MSI)
• relatively intact intersensory processing for simple events, but impaired for complex events -> especially in the social context
• Unisensory impairments which limit intersensory functioning:
  • reduced lipreading
  • face processing
    • detection of speech in a mix
• In general a weak central coherence -> focus more on the components rather than the global picture of things

1. Phonological Hypothesis: specific impairment in the representation, storage and/or retrieval of speech sounds
2. Rapid auditory processing Hypothesis: deficits in the ability to properly process rapidly changing acoustical cues
3. magnocellular hypothesis: importance of temporal processes within the visual system (visual representation of the printed word)
4. cerebellar hypothesis: highly automatic processes are impaired -> timing mechanisms controlled by cerebellar circuits. 

• reduced coupling of auditory and visual responses in the auditory association cortex and superior temporal sulcus
• do not show modulation of the auditory mismatch negativity -> no efficient integration of letter-speech sound information
• have a wider MSI window -> are more easily distracted and have less efficient MSI

Positive symptoms = things that appear

• hallucinations
• delusions
• disorganized behaviour
• disorganized speech

Negative Symptoms = things that disappear

• emotional withdrawal
• anhediona -> inability to feel pleasure during normally pleasurable behaviours
• social avoidance

Structural changes = gray matter contraction

• parieto-occipital regions
• temporal lobes
• frontal lobes

Unisensory: severe deficits in the basic:

• auditory
• visual
• somatosensory

MS Integration:

• decrease of multisensory facilitation
• decrease in the susceptibility to McGurk illusion
• benefit from speech reading/visual articulation is reduced
• cross-sensory gating is impaired (visuoacoustic -> filtering of unnecessary information)