Background Knowledge Flashcards
Which primary (and secondary) brain vesicle does the cerebral cortex come from?
Forebrain (Telencephalon)
Which primary (and secondary) brain vesicle do the thalamus and hypothalamus come from?
Forebrain (Diencephalon)
Which primary (and secondary) brain vesicle do the cerebellum and pons come from?
Hindbrain (Metencephalon)
Which primary (and secondary) brain vesicle does the medulla come from?
Hindbrain (Myelencephalon)
What is the Neuron Doctrine?
The concept that the nervous system is made up of discrete individual cells, a discovery due to decisive neuro-anatomical work of Santiago Ramón y Cajal in the early 1900’s
Who was Hermann von Helmholtz? And with respect to psychophysics, for what is he well-known?
Helmholtz was a German physician and physicist who was interested in the relationships between measurable physical stimuli and their correspondent human perceptions. He sought to demonstrate that nerves conduct signals at finite velocity using crude velocity techniques (results were variable and inaccurate). He did find that the signal velocity was 10’s of milliseconds
What is the nature of neural processing?
Comprises of the neural code which utilises action potentials (spikes).
Individual AP’s do not differ from one another.
Code is based on space (Which neurons are firing) and time (precise time sequence of a series of spikes or “the spike train”)
How does the action potential convey the strength of the signal?
By its frequency
How many neurons are there in the human cerebral cortex?
17 billion
How many neurons are there in the human cerebellum?
69 billion
How many synapses are there in the human brain?
10^14
What is the rate code?
The average spike frequency
Number of spikes over some time/ the interval between events
What is the temporal code?
Precise timing of the spikes within a spike train
How fast do action potentials travel along nerves?
<1m/s to >100m/s. Majority <10m/s
How quickly can APs be generated?
Varies with cell type and species
Fastest= 2ms (spike + absolute refractory period)
What is the maximum firing rate?
500 spikes per second
Define sensation
Reception of sensory data
Awareness of a physical stimulus through the senses
Define perception
Recognition, integration and interpretation of raw sensory information/ stimuli
What are the two theories of perception?
Direct perception (naive realism) The representational model of the mind where there is the outer world, with its mass, and physics and molecules and the inner world (where we make sense of abstract concepts)
What evidence is there for radical skepticism i.e. Can we entirely trust our senses?
Illusions: misinterpreted perception of a sensory experience
Hallucinations: perception in the absence of a stimulus
What is the “hard problem”?
Proposed by Chalmers (1995), the hard problem refers to the fact that mental events (e.g. sensations) seem qualitatively different from the physical
Define dualism
The mind and body are separate substances
Define materialism (physicalism)
The mind is the brain or arises from the physical activity of the brain
Define functionalism
The mind is what the brain does: the brain is hardware and the mind is software
What is Shepard (1990)’s experiment?
Drawing of two tables where one is horizontally and vertically oriented. One seems longer than the other when in fact they are the same size.
This is perception by inference- the hypothesis is constrained by existing knowledge as well as the current sensory neural data
Who proposed the term “perception as unconscious inference”?
Helmholtz (1867)
What is the Bottom-Up theory (feed forward)?
- Physical characteristics result in a particular perception
- Perception is driven by physical characteristics of the stimuli
- Suggests a realist view of the world
o A square is a square because it presents itself with four sides of equal length set at right angles to one another. We match features with stored knowledge - Gibson (1966): In visual perception, patterns of light received by the retina are all that is necessary for perception to occur.
- Well-designed objects suggest their use (affordance)
- Texture gradients- converging lines give the appearance of depth. Closely packed together things suggest objects are further away. Objects are not as large as they seem to appear
- Perceiving Motion- closer objects seem to move more quickly.
- Horizon ratios- used to judge the vertical height of an object
What is the Top Down theory (feedback)?
- Involves the combination of sensorial data with other psychological constructs e.g. expectations, previous experiences or other sensory information to provide context
- Hoover and Beezil proved that that visual input from birth is required to develop the visual cortex
- Perceptual Grouping- we perceive objects as “going together”. This makes the world simpler
- Effect of past experience- You can’t “unsee” something, regardless if you remember having seen it
- Expectation Effect- a bin may seemingly be a burglar if you take the garbage out in the middle of the night
What are pitfalls of the Bottom Up Theory?
Retina is a curved 2D surface yet we perceive the world as 3D. Two eyes yet we perceive one visual world- integration process.
Impenetrability- we know that perception is occurring but we can’t switch it off
