Introduction Flashcards
To acquire the basic knowledge of NNB
What are the neural mechanisms of the sensory systems?
- Receptor neurons
- The anatomical pathways
- Representation in the brain
How does brain react to the world?
- Lower motor neurons initiating muscle contractions
- Upper motor neurons planning and initiating movement
- Filtering and modulating loops (basal ganglia and cerebellum)
What happens in between sensing and reacting?
- Attention
- Cognition
- Memory
- Emotion
What do you learn during the practicals?
How does activity in different neuronal networks control specific behaviors?
What are the two views on how the brain works?
Dualism: mind-body problem
Materialistic view: mind is brain
What is meant by dualism?
“Cogito ergo sum” - I think therefore I am.
René Descartes.
The body works like a machine and has material properties. The mind (or soul) is nonmaterial and does not follow the laws of nature. The mind interacts with the body at the pineal gland
What are arguments for dualism?
- Spontaneity and creativity of the human action
- Machines are primitive
How is dualism found in our culture?
- Language “my body’, ‘my arm’
- Personal identity
- Belief in the survival of the self after destruction of the body
How is the current materialistic view?
- physical things can produce very complex behavior (computers & robots)
- brain damage and personality (Phineas Gage case)
- Drugs and hormones influence the brain/,ind and behavior
- Aging changes the brain/behavior
- Evidence from neuroscience
What is the human brain built of?
The human brain is built of >100 billion (E11) neurons
- 1000-10.000 synapses per neuron
- 10^14 - 10^15 synapses
How do neurons communicate?
By synaptic transmission
How does synaptic transmission work?
- Axons release neurotransmitters
- Different neurotransmitters bind to postsynaptic receptors and determine whether the postsynaptic cell membrane will depolarize (generate EPSP) or hyperpolarize (generate IPSP)
- Synapses/neurons can be excitatory (release glutamate) and inhibitory (GABA, glycine); modulation of synaptic transmission by dopamine, serotonin, acetylcholine etc.
- EPSPs increase excitability of the cell and increase the probability of AP generation
- IPSPs decrease excitability and probability of AP generation
- In the neuronal network each neuron will integrate multiple EPSPs and IPSPs, the sum will determine whether the cell fires an AP
- Frequency of AP firing conveys the signal
- Drugs can bind to the receptors and simulate the action of neurotransmitters
What is IPSP?
(Inhibitory postsynaptic potential)
What are EPSP neurotransmitters and recptors?
Neurotransmitter: Glutamate
Receptors: AMPA, NMDA
What are IPSP neurotransmitter and recptors?
Neurotransmitter: GABA.
Receptors: GABAergic receptors
What are IPSP neurotransmitter and recptors?
Neurotransmitter: GABA.
Receptors: GABAergic receptors
What is a EEG?
EEG is a read-out measure of electrical activity in the cortex
What do multielectrode recordings enable?
They enable network activity to be measured within the hippocampus (‘field’ recording)
How can drugs affect neuronal networks?
Drugs can simulate the action of endogenous neurotransmitter. E.g. cocaine blocks dopamine reuptake in reward circuitry
If you want to build a sensing machine, what would you need?
1) receiver and translator of information into the language of the machine
2) transportation of information for processing
3) Integration and processing of information
4) Giving output
What receives an translates information into the language of the machine
Sensory receptor translate the energy of the stimulus into electrical signals
What transport information for process?
Axons transport the signal to the series of relay nuclei
What integrates and processes information?
Interneurons and local circuitry in nuclei process the signal
How are sensory receptors activated?
Sensory receptors are activated by the energy of the stimulus.
Modality: What types of sensory receptors are known?
Mechanical, chemical, photoreceptors, thermal
How are the different types of sensory receptors activated?
- Mechanical (touch and proprioception, hearing, balance) - physical stretch or tension on the receptor deforms membrane and opens the channels
- Chemical (pain, itch, smell, taste) – binding of a chemical to the receptor
- Photoreceptors (vision: photoreceptors in retina) change in conformation of a photosensitive protein
- Thermal (temperature) receptor activation results in the change of postsynaptic potential
What is the position of the stimulus relative to the body?
Topographical arrangement of neuronal receptive fields
Density of receptors defines the spatial resolution (each receptor has a smaller receptive field). Fovea in retina, fingertips for touch
How big is the stimulus?
The sensory threshold is determined by the sensitivity of the receptors
Where does a change in energy of the stimulus lead to?
it lead to a change in membrane potential, which it turn leads to a translation into digital code of action potentials
How does the stimulus change in time?
- ) Changes in time are coded by changes in frequency.
- ) Rapidly adapting neurons (respond only to changes)
- ) Slowly adapting neurons (sustain their response while stimulated)
- ) Adaptation – a constant stimulus fades from consciousness
- ) Sensory systems are able to detect contrasts and motion
How is sensory information transported efficiently?
by parallel processing
How does parallel processing work?
- ) Multiple parallel pathways increase the speed of processing.
- ) Topographical representation is maintained
- ) Cross over sensory information
- ) Feedback connections/descending projextions
How is topographical representation maintained?
Hommunculus in somatosensory cortex
What are sensory systems capable of?
Sensory systems are able to detect contrasts and motion
What are rapidly adapting neurons good for? What about slowly adapting neurons?
Rapidly adapting neurons: respond only to changes.
Slowly adapting neurons: sustain their response while stimulated
What is the importance of the thalamus?
1) All sensory information passes through thalamus.
2) It is a major relay station for sensory and motor information
3) it projects to the middle layers of the cortex
How does the thalamus look like?
It had a Y-shaped division into anterior, lateral and medial thalamus
How does cortical columns look like?
How does a section of the somatosensory cortex look like?
It has different layers and areas. Layer 2 and 3: go to other cortical regions Layer 4: input from thalamus Layer 5: to basal ganglia Layer 6: to thalamus
What are the dilemmas that arise when we talk about dualism vs materialism?
The body works like a machine, so are we just robots?
Humanistic values?
Hard problem of consciousness
