lecture 6 - electrophysiology Flashcards
electrophysiology
what is electrophysiology?
measures neural function by recording electrical potentials or magnetic fields
single cell electrophysiology
single cell electrophysiology
intracellular recording, can be in vivo (invasive)
best way to guarantee measurement of a single neuron’s behavior
single cell electrophysiology
single cell electrophysiology methods
patch clamp method - creates tight seal
pipette filled with conductive solution, containing single metal electrode that records electrical signals of single cell
receptive fields
receptive fields definition
the sensory field where a stimulus as the potential to excite/ can trigger a neuron to AP
“zone of influence”
receptive fields
receptive field - spatial location
neuron responds to an area in space where stimulus must be to trigger AP
ex: visual cortical neurons driven by retinal location of stimulus (where stimulus is located in retina)
receptive fields
receptive field - specific feature
neuron responds to a particular feature to trigger AP
ex: auditory cortical neurons driven by frequency (pitch) of sound
receptive fields
hippocampal “place” cell
fires when animal enters a specific place/location in its environment (usually during exploratory behavior)
- here the receptive field is the spatial location of the observer, not the specific stimulus
LFPs
local field potentials
extracellular, measures postsynaptic potentials in dendrites
LFPs
what causes postsynaptic potentials?
slight depolarization due to excitatory NT binding OR slight hyperpolarization due to inhibitory NT binding
LFPs
why collective activity measurement
EPSPs & IPSPs are small in single neuron
LFPs measure collective current flow across dendritic membrane of multiple (thousands) of postsyn neurons
LFPs
how does collective activity measurement work
spatial & temporal summation allows electrical field (dipole) to be measured in extracellular space
LFPs
cortical sources for LFPs
pyramidal neurons (cell body triangle shape)
~85% of neurons in cerebral cortex are excitatory pyramidal
LFPs
closed electrical fields
radially symmetric neurons, randomly oriented neurons, asynchronously neurons = closed source fields
- CANNOT measure
LFPs
open electrical field
synchronously activated & perpendicular to cortical surface = open source field
- can measure + record
ECoG
electrocorticography (ECoG)
electrodes place on cortical surface, invasive
ECoG
ECoG used when?
common in presurgical work-ups
ECoG
ECoG adv & disadv
- better ‘view’ of electrical changes with skull removed
- still most sensitive to cortical surface (not deeper)
electrophysiology
invasive vs noninvasive measures
invasive:
- single cell
- LFPs
- ECoG
noninvasive:
- EEG
- MEG
electrophysiology
which electrophysiology methods are electric field recordings
multiple neurons
LFPs, ECoG, EEG - record electrical activity of multiple nurons
EEG
what is electroencephalography
“writing with the brain’s electric field”
electrodes attached to scalp
EEG
how is EEG measured?
2 electrodes that measure difference in electical potential
EEG
resistivity in EEG
electrical current has a harder time passing through different tissues because of varied conductivity
- resistance is different for different tissues
MEG
what is magentoencephalography
“writing with brain’s magnetic field”
big machine
MEG
how is MEG measured?
uses magnetic shield to focus on brain’s magnetic field (produced by electrical current) and blocks out interfering surrounding magnetic fields
