Ch13 - Combining fMRI with other techniques Flashcards
converging operations
employing 2+ techniques to provide complementary evidence used to test an experimental hypothesis or scientific theory
constructs
abstract concept that explains behavior but that itself is not directly observable
- e.g. psychological constract
isomorphic
having an identical form
- a physiological measurement that is isomorphic with psychological construct would vary over time consistently with postulated changes in the construct
localization of function
idea that brain may have distinct regions that support particular mental process
functional connectivity
pattern of functional relationships among regions, inferred from common changes in activation over time
- may reflect direct or indirect links between these regions
direct cortical stimulation
applying small currents directly to brain tissue to excite or disrupt neural activity
- usually contucted in humans to localize critical brain regions in context of neurosurgery
transcranial direct current stimulation
(tDCS)
inexpensive and safe neuroscience technique using weak electrical current that passes through brain
- changers excitability of neurons and alters brain function
equipotentiality
concept that a function is so widely distributed within brain that activity depends on whole brain
- antithesis of localization of function
anode
source of positive charge or ions and attractor of free electrons
cathode
attractor for positive charge/ions and source of free electrons
homotopic
cortex in one cerebral hemisphere corresponds to same region in other hemisphere
single-pulse TMS
delivery of single TMS stimulation pulse to disrupt some ongoing brain process
repetitive TMS
delivery of extended series of closely spaced TMS stimulation pulses to effect long-lasting changes in brain function
- may lead to indirect changes in brain physiology by increased excitability/inhibition of area
- applied for e.g. chronic neurological and psychiatric conditions
single dissociation
demonstration that an experimental manipulation has an effect on one variable but not a second
double dissociation
demonstration that 2 experimental manipulations have different effects on 2 dependent variables. Manipulation A affects X but not Y, Manipulation B affects Y but not X
registry
patient database
plasticity
change in normal functional properties of brain tissue following injury or experience
recovery of function
improvement in previously impaired ability over time due to functional/structural changes within brain
polymorphism
common variation in a gene or segmant of DNA
imaging genomics
field that investigates effect of genetic variation on brain structure and function
action potential
wave of depolarization that travels down neuronal axon
electrogenesis
generation of electrical electrophysiological phenomena by living organism
single-unit recording
collection of data about electrophysiological activity of single neuron
field potentials
changes in electrical potential over space associated with postsynaptic neuronal activity
recepive field
part of visual field that, when stimulated, will result in an increase in firing of particular neuron
simple cell
neuron in visual cortex that responds with increased firing to stimulus with preferred orientation in its receptive field
decreased firing when stimulus in surroundings of receptive field
- central rectangular region
complex cell
neuron in visual cortex with larger receptive field than simple cell that responds to stimulus with preferred orientation anywhere withing receptive field
ion
atom or molecule that carries electrical charge
pump
transport system that moves ions across cell membrane against concentration gradient
current sink
attractor of positive ions
- depolarized patch of neuronal membrane is a current sink because positively charge ions will flow towards it
current source
source of positive ions
primary current
current flow within neuron caused by inflow of ions through ionic channels opened by synaptic activity
volume conducter
continuously conductive medium
- brain, meninges, skull, scalp constitute of a volume conductor throughout which currents created by ionic flow can be measured
volume current
return current through extracellular medium that balances the primary current within neuron
current dipole
idealized pairing of current source and current sink separated by infinitesimal distance
- used as a simple convenient model for electromagnetic fields produced by activated neuron
apical dendrites
dendrites that are distant from the neuronal cell body
- e.g: pyramidal cells - dendrites extend all the way to the cortex
equivalent dipole
simplified model that represents the electromagnetic field produced by population of neurons as though it were produced by single dipole
polysynaptic potential
(PSP)
Any postsynaptic potential that results from synaptic activity
excitiatory postsynaptic potential
(EPSP)
depolarization of postsynaptic cell membrane
inhibitory postsynaptic potential
(IPSP)
hyperpolarization of postsynaptic cell membrane
electric dipole
a point in space whose electrical propertied can be approximated by assuming that it consists of physically separated positive and negative charges
inverse problem
mathematical impossibility of determining the distribution of electrical sources within an object based on the measurement of electric/magnetic fields at the surface of the object
evoked potential
field potential that occurs in response to sensory stimulus
event-related potentials
(ERPs)
small electrical changes in the brain that are associated with sensory or cognitive events
ERP component
stereotypic feature of an ERP waveform, such as a peak at a particular latency, that has presumed functional significance
forward solution
direct calculation of the electric and magnetic fields that would occur at an array of sensors based on a given distribution of dipoles with known orientations and magnitudes
evoked magnetic fields
(EMFs)
change in the MEG signal that occurs in response to a particular stimulus
- equivalent of evoked or event-related potential in EEG
