Data revision Flashcards
what are baseline corrections applied to 2p imaging?
Baseline correction involves subtracting the fluorescence (∆F/F) signal recorded just before stimulus onset (-0.5 to 0 s) from the post-stimulus response. This normalization ensures that changes in fluorescence reflect stimulus-evoked neural activity rather than fluctuations in baseline activity or slow drifts in signal. Without this correction, spontaneous fluctuations in neuronal activity might obscure the true stimulus-evoked responses, making it harder to compare activity across different neurons or experimental conditions.
why do you need to do post hoc immunostaning after 2p imaging?
Two-photon imaging alone does not provide direct molecular identification of neurons, only their calcium dynamics. By using immunohistochemical staining after imaging, researchers can determine the identity of recorded interneurons by matching their positions in post hoc brain slices to those in the in vivo imaging plane.
Why do they present the grey screen before stimulus is shown
grey screen-nerutral baseline-no contrast so won’t activate discrimination response.
ensuring that neural activity recorded in response to the gratings is not confounded by residual responses to previous stimuli and it can reset cortical activity between trials.
limitation of GCaMP6f-based two-photon imaging in interpreting the temporal dynamics of the neuronal responses
lower temporal resolution. GCaMP6f indicates intracellular calcium transients- indirectly reflects neural spiking. calcium dynamics have slower kinetics than APs.
electric field is generated by?
currents flowing down dendrites
Electric field strength depends on
squaure of distance
conductivity of brain tissue
MEG is msot sensitive to
tangential sources parallel to the scalp.
Which brain region is MEG good for
Auditory cortex activity
Evoked field on Y axis means
Strength of brain response
Time on x axis (ms)
what do local field potentials tell us
aggregate activity of small populations of neurons represented by their extracellular potentials. These signals are well suited for use in closed-loop neurophysiology because they are robust, easy to record, and clinically useful.
3 pros of intracranial recording
- High signal to noise ratio (close to source and less distortion)
- Highly localised activity (especially for single neuron recordings)
- High temporal resolution (as with EEG and MEG)
3 disadvantages of intracranial recordings
- Activity may be contaminated by interictal activity or seizures (exclude)
- Coverage is incomplete and determined by clinical need
- Patients may be medicated and/or have atypical brains
Compared to fMRI: EEG, MEG and intracranial
recordings:
- provide a more direct measure of neural activity (electrical signals, not blood flow)
- have finer temporal resolution (milliseconds, not seconds)
- provide lower spatial resolution / coverage
Compared to EEG: MEG
- is not affected by conductivity of different tissue types e.g. grey matter, scalp, skull
- has a higher signal-to-noise ratio
- is more selectively sensitive to tangential sources (i.e. those parallel to the scalp)
- can offer more reliable source localisation
- is usually less portable
Compared to EEG and MEG: intracranial
recordings
have a higher signal-to-noise ratio (closer to the source)
* have high spatial resolution (particularly with single neuron recordings)
* provide less complete brain coverage (placement based on clinical need)
* are made from patients who may be on medication or have atypical brains
Disadvantage of electrophysiology
Extracellular electrophysiology can only detect neurons when
they produce spikes — but has the temporal resolution necessary for
analysis of auditory receptive fields and short-term context sensitivity.
