PSY270H1 Lecture Notes - Sensory Neuroscience, Sensory Neuron, Microelectrode

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PSY270 Ch.2
Cognition and the Brain: Basic Principles10/8/2012 11:20:00 AM
1. Neurons & the nervous system
2. How neurons communicate
3. How neurons process info
4. How stimuli are represented by the firing of neurons
5. Cognitive processes & the brain
6. Interacting with the environment affects operation of the nervous
1. Neurons & the nervous system
Camillo Golgi developed a chemical technique that stained some
neurons but left most unstained, which revealed the structure of
single neurons in pictures
Neurons: cells that are specialized to receive and transmit
information in the nervous system
o Different neurons specialized for difference functions
Cell body (keeps the cell alive)
Dendrites (branch out from cell body, receive info from
other neurons)
Axon/Nerve Fibre (transmitting structure of the neuron,
tube filled with fluid to conduct electrical signals)
Sensory receptors (sometimes replace cell body +
dendrites at receiving end. Receptors are specialized
structures which respond to sensory info/changes in the
o Stimulus from environment Sensory receptors Electrical
signal along nerve fiber Synapse Dendrites Cell body
o Transduction: the transformation of one form of energy into
another form of energy (e.g. energy from environment into
electrical energy)
Recording from Single Neurons
o Detecting neuron‟s electrical signal and relating these signals
to cognitive processes
o Action potentials: signals recorded by using tiny wires called
microelectrodes, which are places near an axon, and that pick
up the electrical signals that travel down the axon
Axons electrical signals displayed on an oscilloscope
show that the charge of the neurons change.
o Action potential info about stimulus intensity is represented
not by size of action potentials, but by their rate of firing.
o Action potentials are propagated they travel from one end
of the axon to the other without decreasing in size
Signals can travel long distances as individual neurons
are linked together
2. How neurons communicate
What happens once action potentials reach the end of the axon?
Communication between neurons occurs at the synapse:
o Synapse: a space between the end of the axon and the next
neuron which transmits signals to the next neuron
Chemical process that bridges the gap between the two
When potentials reach the end of one neuron, they
cause structures called synaptic vesicles to open and
release chemicals called neurotransmitters onto the
next neuron.
Excitation and inhibition interact at the synapse:
o When neurotransmitters are released there are 2 scenarios
that can occur
Release of an excitatory neurotransmitter from one of
the neurons increases the chances that the next neuron
will fire. Excitation = Increased nerve firing
Release of an inhibitory neurotransmitter decreases the
chances that a neuron will fire. Inhibition = Decreases
nerve firing
3. How neurons process information
Brain has 180 billion neurons, 80 billion involved in cognitive
Neurons process information by interacting with each other
o Neural processing: occurs when a number of neurons synapse
together to form a neural circuit a group of interconnected
o Two basic properties of these circuits that contribute to neural
processing are:
Convergence: a number of neurons sending signals to a
single neuron
Interaction of excitation & inhibition
Neural processing creates neurons that respond to specific types of
o Hubel & Wiesel (1965) research on visual system
Neurons that respond best to a bar of light with a
particular orientation, called simple cells
Neurons that respond
best to bars of light of a
particular orientation
that were moving
across the retina in a
specific direction, called
complex cells
Neurons that respond
best to an orientated