***Extensive Summary of lectures 1 - 7 for the course "perception & motor control" in ENGLISH. All images and text from the slides are included, as well as important text from the reading material. ***
Other human senses include:
- pain (nociception)
- balance (vestibular system)
- body posture (proprioception)
- temperature
- internal organs
o respiration, heart beating
o hunger, gagging, swallowing
o full bladder, rectum
- Non-human senses
o Electric fields (fish)
o Magnetic fields (pigeons)
o Light polarisation (insects)
General physiological principles
Transduction: specialized cells in the sense organs
convert stimulus energy into electrical signals.
Different experiences are evoked because the
signals from different senses arrive in different
brain regions (specific nerve energy).
Electrical stimulation in these areas evokes a
corresponding sensation.
Classification of the senses:
The main senses can be divided
into:
Four receptor types and six
receiving brain areas.
,Sensations & Representation
Magnitude of sensations:
Sensations are caused by stimulation of the sensory organs. Usually, the more intense the stimulus
the stronger the sensation. Light intensity → brightness. The rate of increase varies with different
sensations. Steven’s law: relation is a power law.
Adaptation:
The relation between sensory magnitude and stimulus level is not fixed,
but varies according to stimulus conditions. Following prolonged
exposure to a given stimulus level, apparent intensity is reduced and
weak stimuli are more difficult to detect – adaptation.
Representation:
We have seen that sensory stimulation causes localized activity in
dedicated sensory brain areas (localization of function). Thus, different
patterns of brain activity represent different sensations.
But, sensations =/= neural activity. A sensation is a conscious mental
state. Neural activity is a physical state.
Relating sensations with neural activity requires a theory: linking
propositions. A linking proposition links mental states to physical states.
Perceptual processing advances through successive stages. →
Each stage computes a representation of the input.
Points to remember:
• Sensations correspond to patterns of brain activity in dedicated brain areas (localization of
function)
• Sensations are caused by stimulation of sensory receptor cells in our sensory organs (transduction)
• Sensations often have a magnitude
• Over time the sensed magnitude decreases (adaptation)
• Electrical signals from the sensory receptors are processed in several stages (computation)
• Each stage ‘represents’ the external cause of stimulation (representation)
, Nervous system:
The nervous system is not just the brain, it also includes spinal cord and nerve fibers (or just nerves).
Information processing already takes throughout the nervous system. The basic functional unit of this
system is the neuron. Humans have around 20 billion (miljard) neurons in the brain, in comparison to
the octopus with 300 million and a bee with 950 thousand.
Directions in the brain
Rostral Toward the nose
Caudal Toward the tail
Dorsal Toward the back
Ventral Toward the belly
Lateral Toward the side
Medial Toward the middle
Anatomic organization of the brain:
Anatomically: Brodmann’s areas.
Functional organization of the brain
The functional organization of the brain is also topographic.
Brain areas are specialized for certain functions.
Neurons
There are many different neurons. Unipolar cell, bipolar cell, pseudo-unipolar cell and three types of
multipolar cells (motor neuron, pyramidal cell of hippocampus, pikinje cell of cerebellum).
Dendrites: receive neurotransmitters from other cells. It conducts signals to the trigger zone (usually
near cell body).
Trigger zone (cell body): Integrates electrical signals and ‘fires’ an action potential.
Axon: Conducts electrical signals to terminal
buttons.
Axon terminals (synapses): Releases
neurotransmitters. They are connected to dendrites
of other neurons.
Myelin sheath: Improve conduction.
Nodes of ranview: amplify action potential.
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