L2 Methods Flashcards
How can we represent sensory information about cells in the brain?
Techniques such as single cell recording.
What type of representation is a cell?
Low level representation, very confined area of space (each photo cell has a small visual space that it responds to)
What is a pathway?
where one area is anatomically connected to another area and they both code information
What do we mean by attributes in the brain?
What parts of the brain are interested in what type of information
What are the 4 steps for the hierarchy of processing sensory information?
- Receptors
- Neurons transmit information
- Thalamus (relay station)
- Cortical processing
For sensory information, what does a single cell code?
Codes information present in a small area of space (over time)
What is the receptive field of a cell?
A “receptive field” is the area over which a cell changes its activity in response to a change in stimulus (e.g. luminance or colour)
How do we record cell activity?
Electrophysiology (EP)
What does Electrophysiology (EP) measure?
Records the electrical activity from a single cell
What are the features of Electrophysiology (EP)?
Allows to measure the function of a cell over time
Has high spatial selectivity
If sensory information passes over the receptive field of a neuron, what happens to the neuron?
Increase in electrical activity.
What did Hubel and Weisel get their Nobel prize for?
V1 - simple cells orientation firing rate
What are the features of V1 (simple cells)?
Excitatory and inhibitory regions, arranged side-by-side
Orientation tuned, but not fussy about size
What are the two pathways of sensory encoding called?
Dorsal and Ventral Pathways
Which pathway is the ‘where’ pathway
Dorsal
Which pathway is the ‘what’ pathway?
Ventral
What are the three regions that the visual pathway goes through when going from the retina to the cortex
Retinal Nerve Cells
LGN
V1
Which region of the cortex does the dorsal pathway lead?
Parietal
Which region of the cortex does the ventral pathway lead?
Temporal
The ventral (‘what’) pathway connects what two parts of the brain?
LGN to temporal lobe
The ventral (‘what’) pathway is responsible for what type of visual processing?
Object processing and in fine detail
The dorsal (‘where’) pathway connects what two regions of the brain?
LGN to parietal lobe
The dorsal (‘where’) pathway is responsible for what type of visual processing?
Motion processing and Spatial processing
What region of the brain is responsible for colour?
V4
What region of the brain is responsible for motion?
MT/V5
Damage to V4 creates a loss in ____
Colour perception
Damage to MT/V5 leads to a loss in ___
Motion perception
(can’t see things move in the environment)
Representation of stimulation is organised in the cortex to mirror stimuli in the world
True or false?
True
e.g. two points of light that are detected at adjacent spots on the retina are represented next to each other in the cortex.
What do we mean when we say that information in our brain is coded in a map?
Each sense has a representation of stimuli in the brain that is organised in the cortex to mirror stimuli in the world.
What do retinotopic maps in the cortex do?
Preserve the relative position of stimuli as they are received on the retina
Where is our visual representation most dense?
In the centre of our visual field (our fovea)
How did Tootell, Silverman, Switckes and DeValois (1982) show that our visual field is more dense in the centre and that we have a retinotopic map in our brain?
Showing animals an image while sacrificing them at the same time and injecting their brain with dye.
It shows us where the representation is in the brain.
Are all senses represented equally in the brain?
No
Homonculus shows where the representation is strongest
When linking brain activity to function is it better to represent this as maps or pathways?
What’s the difference in the explanatory power of these explanations?
Depends on the type of question but common to use the ‘computational algorithms’ representation
(meaning that the processes are ‘lawful’)
Still much debate about what sort of linking proposition you should use to describe the state of brain and physiology
What is the Marr approach?
Between circuits and behaviour
Applying the way computers work to brains (computational approach)
What are the 6 techniques you can use to measure brain function?
What is Psychophysics?
Experimental techniques for measuring the percept associated with a stimulus of a given intensity
The method of constant stimuli, method of limits, method of adjustment and the method of single stimuli are examples of what type of measuring technique?
Psychophysical
What technique might you use to see how well people can discriminate the location of two lines in space?
Psychophysical
What is ‘hyperacuity’?
Our ability to discriminate position is better than the width of a photoreceptor
What technique helped discover ‘hyperacuity’?
Psychophysics
Why did ‘hyperacuity’ tell us about processing?
That there is an inferential process happening even at as low a level as the level of the retina
What technique might you use if you are interested in the neural mechanisms of the brain?
(What part of the brain is active when doing certain activities)
fMRI
What is a weakness of the fMRI?
Hard to study certain types of things while in a magnet (limited movement, have to be lying down etc.)
Everybody’s brain is slightly different, how are we able to compare each other’s brains?
First segment grey-white matter boundary
Then render the cortical surface
Then inflate the cortical surface
What are the three types of designs for fMRI?
Block, Event-Related, Mixed
(blue is the stimulus, red is the brain response)
Describe the fMRI block design
Describe the fMRI event-related design.
Why is it important to have accurate models?
So we can accurately predict outcomes from our experiments.
