Chapter 2.1 - 2.2 Flashcards
To understand how the mind works you must experiment borh:
Behavioural and physiological experiments
What is physiological?
branch of biology that deals with the normal functions of living organisms and their parts.
What is cognitive neuroscience?
Field concerned with studying the neural basis of cognition.
The reasoning behind the conclusion in order to understand how the mind works to do both behavioural and physiological experiments
Is based on the idea of what?
Level of analysis
What is level of analysis?
A topic can be understood by studying it at a number of different levels of a system.
each approach contributing its own dimension to our understanding
Analogy of level of analysis
e.g buying a new car
- You can and should of course look at its performance on the road; how well does it accelerate, brake and take corners?
- On the other hand, you can also look at what is going on under its hood; are motor, breaking and steering mechanisms functioning okay and are they not affected too much by wear and tear?
- Indeed, you can look at an even deeper level, for example by finding out how well fuel enters the engine and how it is ignited.
- Clearly, considering the automobile from the different levels of driving the car, describing the motor and observing what happens inside a cylinder provides more information about cars than simply measuring the car’s performance.
Applying the level of levels of analysis to cognition
e.g car
- Consider measuring behaviour to be compared to measure the car’s performance
- measuring the physiological processes behind the behaviour as comapred to what we learned by looking under the hood.
- Study what is happening under a car’s hood at different levels,
Applying the level of levels of analysis to cognition
Can study the physiology of cognition at levels ranging from the whole brain to structures within the chrain, to chemicals that create electrical signals within these structures.
Brain is static tissue
meaning
No moving parts like the heart
Doesn’t expand or contract (like lungs)
What to look for when understanding the relation between the brain and mind and specifically to understand the physiological basis for everything we perceive?
necessary to look at?
Look within the brain and observe small units of neurons
What are neurons?
Cell that is specialized to receive and transmit information in the nervous system.
Create and transmit information about what we experience and know.
What was discovered in the 19th century?
The nature of electrical signals in the brain and the pathways over which they travelled began to discover
How did people observe the structure of the brain in 19th century?
- 19th century anatomists applied special stains to the brain issue
- This increased the contrast between different types of tissues within the brain
What happened when 19th century ataomists applied the special stain in the brain tissue and viewed this stained brain tissue under a microscope?
Saw a network that they called nerve net
Provided complex pathway for conducting signals uninterrupted through the network
What is nerve net?
A network of continuously interconnected nerve fibres (as contrasted with neural networks, in which fibres are connected by synapses).
Diagram of nerve net theory and image of neurons
What one reason for descriving the microstructure of the brain as a continuously interconnected network?
Staining techniques and microscope used during 19th century could not resolve small details, without these details, the nerve net appeared to be continuous
What did Camillo Golgi do in 1870?
Italian anatomist
- Developed a staining technique which created photo shown below(2.2b)
- With this staining technique, named after its inventor, less than one per cent of the cells were stained, so they stood out from the rest of the tissue. Also, the cells that were stained were stained completely, so it was possible to see their structure.
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What was Camillo Golgi’s staining technique called
Golgi staining technique or called black reaction after the stain’s colour
What did Ramon y Cajalf did?
Spanish physiologists
- Used Golgi staining technique in newborn animals to closely investigate the nature of the nerve net
Why was Ramon y Cajal’s decision to use newborn animals clever?
Density of cells in newborn brain is small compared to the density in the adult brain
What did Ramon y Cajal discover?
- This property of the newborn brain, combined with the fact that the Golgi stain affects less than one per cent of the neurons, made it possible to clearly see that the nerve net was not continuous, but was instead made up of individual units connected together (Kandel, 2006).
- The discovery that individual units called neurons were the basic building blocks of the brain was the centrepiece of the neuron doctrine
What is neuron doctrine?
The idea that individual cells called neurons transmit signals in the nervous system, and that these cells are not continuous with other cells as proposed by nerve net theory.
Basic parts of neuron diagram + synapse
What is the cell body?
Metabolic centre of the neuron
Contains mechanisms to keep the cell alive
Part of a cell that contains mechanisms that keep the cell alive. In some neurons, the cell body and the dendrites associated with it receive information from other neurons.
What is the function of dendrites?
receive signals from other neurons.
Structures that branch out from the cell body to receive electrical signals from other neurons.
Where does dendrites branch out from?
Cell body
What are axons also known as?
Nerve fibres
What are axons?
Part of the neuron that transmits signals from the cell body to the synapse at the end of the axon.
are usually long processes that transmit signals to other neurons.
What does this figure show?
shows a neuron with a receptor that receives stimuli from the environment—pressure, in this example. Thus, the neuron has a receiving end and a transmitting end, and its role is to transmit signals.
Important conclusions Cajall came to about neurons?
- There is a small gap between the end of a neuron’s axon and the dendrites or cell body of another neuron. This gap is called a synapse .
- Neurons are not connected indiscriminately ( in a random manner) to other neurons, but form connections only to specific neurons. This forms groups of interconnected neurons, which together form neural circuits.
- In addition to neurons in the brain, there are also neurons that are specialized to pick up information from the environment, such as the neurons in the eye, ear and skin
- Neurons are called receptors
Analogy of a synpase
In the highway analogy, a synapse may symbolize a crossing with traffic lights, providing an opportunity to manage the flow of cars, to reduce their speed, and to distribute them over different routes.
What is a synapse?
Space between the end of an axon and the cell body or dendrite of the next axon.
What is a neural circuits?
Group of interconnected neurons that are responsible for neural processing.
What are the receptors?
Specialized neural structures that respond to environmental stimuli such as light, mechanical stimulation or chemical stimuli.
Receptors synapse close up
Contribution of Cajalf
- Separate neurosn communicate with other neurons to form neural circuits enormous leap forward in understanding how the nervous system operates
- The concepts introduced by Cajal—individual neurons, synapses and neural circuits—are basic principles that are still used today to explain how the brain brings about certain cognitive functions, such as perception, language and memory.
- These discoveries earned Cajal the Nobel Prize in 1906, and currently, he is recognized as “the person who made the cellular study of mental life possible” (Kandel, 2006, p. 61).
What did Cajal miss after describing the development of individual neurons and how they are related to other neurons and transmitted signals?
Determining the exact nature of these signals had to await the development of electronic amplifiers that were powerful enough o make the extremely small electrical signals generated by the neuron visbile.
Whast was Edgar Adrian in 1920s able to record?
electrical signals from single sensory neurons, an achievement for which he too was awarded the Nobel Prize.
When an axon/nerve fibre is at rest the meter records a difference in potential between the tips of the two electrodes of how much millivolts?
-70 millivolts
Millivolt is 1/1000 of what?
A volt
-70 millivolts is the value stays the same as long as there are no signals in the neuron is called what?
Resting potential
Neuron has a charge that is 70 mv more negative than the outside and this difference continues as long as the neuron is at rest
Definition of resting potential
Difference in charge between the inside and outside of a nerve fibre when the fibre is at rest (no other electrical signals are present).
Diagram of typical set up recording from a single neuron
How did Adiran (1928,1932) record electrical signals from a single neuron?
Using microelectrodes
What are microelectrodes?
Small wires that are used to record electrical signals from single neurons
small shafts of hollow glass filled with a conductive salt solution that can pick up electrical signals at the electrode tip and conduct these signals back to a recording device.
What two types of electrodes needed from this setup to record a single neuron?
- Recording electrode
- Reference electrode
What type of electrodes do modern psychologists use?
Metal microelectrodes
Where is recording electrode located?
When used to study neural functioning, a very thin glass or metal probe that can pick up electrical signals from single neurons.’
Recroding tip inside the neuron
What does figure 2.5b show?
- Neuron’s receptor is stimulated by a nerve impulse is transmitted down the axon
- As impulse passes the recording electrode, charge inside the fibre reverses course and starts becoming negative again (figure 2.c) until it returns to resting potential (figure 2.5d) - this is called action potential lasts 1 millisecond
What does figure 2.6 show?
- Action potential on a compressed time scale
- Each vertical line represents action potential, series of line indicate a number of action potential passed electrode (2.6a)
- One action potential expanded on a time scale. There are other electrical signals in a nervous system but we will focus on action potential (2.6b)
Imagine you want to study the relation between nerve firing and sensory experience
How do you so and what will you find?
- measuring how the firing of a neuron from a receptor in the skin changes as you apply more pressure to the skin.
- find is that the shape and height of the action potential will remain the same as you increase the pressure, but that the rate of nerve firing–that is, the number of action potentials that travel down the axon per second–will increase
What does this figure deduced?
- important connection between nerve firing and experience can be deduced.
- Namely, when nerve impulses are close together (high firing rate) the sensation is intense, and, in contrast, when nerve impulses are more separated from each other (low firing rate) then the sensation is correspondingly weak.
What does this simple experiment of finding out the relation between nerve firing and sensory experience suggest?
- electrical signals are representing the intensity of the stimulus, so the pressure that generates “crowded” electrical signals feels stronger than the pressure that generates signals separated by long intervals.
What does this simple experiment suggest about vision?
- Other experiments have demonstrated a similar principle for vision.
- Presenting high-intensity light generates a high rate of nerve firing and the light is perceived or “experienced” as being bright;
- presenting lower intensity light generates a lower rate of nerve firing and the light is perceived or “experienced” as being dimmer.
- Thus, the rate of neural firing is related to the intensity of stimulation, which, in turn, is related to the magnitude of an experience, such as feeling pressure on the skin or experiencing the brightness of a light.
What did David Hubel and Thortsen Wisel started in 1960s?
series of experiments in which they presented visual stimuli to cats, as shown in Figure 2.8a, and determined which stimuli caused specific neurons to fire
What does figure 2.8b show?
- shows some of the stimuli that caused different neurons in and near the visual cortex to fire
- They called these neurons feature detectors because they responded to specific stimulus features such as orientation, movement and length.
For humans, and indeed all other mammals, the visual cortex is situated at where?
back of our head, the occipital lobe (the ‘magenta’ part
What has further research beyond visual cortex revealed about neurons
respond to more complex stimulus features (for example, geometrical shapes, hands, buildings or faces) or to a combination of simple stimulus features (for example, a left-tilted line that moves to the right).
neurons are situated in the cortex at the side of our head. This part of our brain is called the temporal lobe (this is the brownish part in Figure 1.12).
In early experiments, Gross and colleagues recorded activity from what?
- from single neurons in a monkey’s temporal lobe, on the side of the brain, while a variety of different stimuli were presented on a projection screen like the one in Figure 2.8a.
- Besides diagonally oriented bars, they also presented squares and circles, and some stimuli were light and some were dark.
Charles Gross conclusion
- Great deal of testing, they determined that this neuron responded maximally to a hand-like shape with fingers pointing up (Figure 2.9)
- After expanding the types of stimuli presented and the place of recording, researchers also found some other neurons in the temporal lobe that responded best to faces, but didn’t respond to other types of complex stimuli like hands or buildings
What does figure 2.10a show?
specificity coding
- hows how a number of neurons respond to three different faces.
- Only neuron #4 responds to Ian’s face, only #9 responds to Hannah’s face, and only #6 responds to Sam’s face.
- Also note that the neuron specialized to respond only to Ian, which we can call an “Ian neuron,” does not respond to Hannah or Sam. In addition, other faces or types of objects would not affect this neuron. It fires only to Ian’s face.
How is population coding demonstratedin this figure?
According to this idea, Ian’s face might be represented by a certain pattern of firing of ten different neurons, Hannah’s face by a different pattern, and Sam’s face by yet another pattern of the same ten neurons
How is sparse coding seen in figure 2.10
- represent Ian’s face by the pattern of firing of a few neurons (neurons 2, 3, 4 and 7). Hannah’s face would be signalled by the pattern of firing of a few different neurons (neurons 4, 6 and 7), but possibly with some overlap with the neurons representing Ian, and Sam’s face would have yet another pattern (neurons 1, 2 and 4).
- Notice that also in this case a particular neuron can respond to more than one stimulus. For example, neuron #4 responds to all three faces, although most strongly to Hannah’s.
