Chapter Three Flashcards
Representations:
properties of the world that are manifested in cognitive systems (mental) and neural systems (neural)
Single-cell recordings:
measure the responsiveness of a neuron to a given stimulus (in terms of AP/sec)
Electroencephalography (EEG):
measurements of the electrical signal generated by the brain through electrodes placed on different points on the scalp
What characteristic makes EEG methods highly useful?
changes are conducted instantaneously making it useful when measuring relative timing of cognitive events and neural activity
Event-related potentials:
The average amount of change in voltage at the scalp that is linked to the timing of a particular cognitive events
EX: stimulus, response
Reaction time:
the time taken between the onset of a stimulus/event and the production of a behavioral response (button press)
Functional imaging methods (fMRI) have better temporal/spatial resolution than temporal/spatial resolution.
spatial; temporal
Lesion methods tend to rely on measuring […] than […].
error rates; time-based processes
The AP is directly measured in the method of […].
single/multi cell recording
How can single-cell recording be obtained?
Why is it impossible to measure AP from a single neuron noninvasively?
electrode implanted intra or extracellularly
signal is too weak and the noise from other neurons is too high
Multi-cell recordings:
electrical activity (AP/sec) of many individually recorded neurons recorded at one or more electrodes
Grandmother cell:
hypothetical neuron that just responds to one particular stimulus
EX: the sight of one’s grandmother
What are the three different types of representation that may be found at the neural level?
- local: all information about a stimulus/event is carried in one of the neurons (grandmother cell)
- fully distributed: all information about a stimulus/event is carried in all the neurons of a given population
- sparse: a distributed representation in which a small proportion of the neurons carry information about a stimulus/event
Rate coding:
the informational content of a neurons may be related to the number of AP per second
given stimulus/event is associated with a change (typically increase) in the rate of neural firing
Temporal coding:
synchrony of firing may be used by a population of neurons to code the same stimulus or event
given stimulus/events is associated with greater sychronization of firing across different neurons
Both multi and single-cell recordings representation of information dependson what type of coding?
Why?
sparse distributed coding
- conserves energy
- high memory capacity
- protect against losing information if synapses or neurons die
- generalize/categorize (deja vu)
Th physiological bases of the EEG signal originates in the […] current rather than the axonal currents.
postsynaptic dendritic (passive)
In order for an electrical signal to be detectable at the scalp, what basic requirements need to be met?
Based on these requirements, what region is the most optimal space for EEG recording?
- whole population of neurons must be active in synchrony to generate a large enough electrical field
- population must be aligned in a parallel orientation so they can summate together (not cancel out)
cerebral cortex
EEG: The greater the electrical activity of neurons…
the greater the voltage change at the scalp
To gain an EEG measure one needs to compare the …
voltage between two or more different sites
What are some types of reference sites for EEG voltage comparisons?
- nasal
- mastoid bone behind ear
- average of all electrodes
Electrode placement labeling:
right side = even numbers
left side = odd numbers
midline = z
frontal = f
parietal = p
occipital = o
temporal = t
central = c
What are the limitations of ERPs?
Poor spatial resolution– don’t know the source of the signal we only know scalp distributions
- electrical signal is filtered/distorted by body tissue
- summed postsynaptic potentials; ERP loses identity of individual neurons/layers
- cannot distinguish IPSPs and EPSPs; polarity at the scalp depends on the location and the type of PSP
- inverse problem; have the output but that could be created through a variety of combinations
Incomplete measure of the brain
- ERP generated by synchronous firing of open field neurons
- ERPs are blind to close sources and asynchronous firing
- Electrical fields in sulci cancel out
- Distant and small activity will cancle out
The most common use of EEG in cognitive neuroscience is the method known as […].
ERP