Chapter 7 - Measuring and Manipulating Brain and Behavior Flashcards
how to study humans with brain lesions
can be investigated in a postmortem examination or with a neuropsychological test
neuropsychology
the study of the relationship between brain functions and behavior in human beings
behavioral neuroscience
the study of the biological bases of behavior
- measuring brain activity is difficult and has low reliability and validity
- you can either very specifically measure the location or the time of an activity, not both
anatomical (static) - functional (dynamic)
- anatomical (static) measurements study the fixed structure of the brain (what the brain looks like at a fixed point in time)
- functional (dynamic) measurements study how the brain works and changes over time
invasive - non-invasive
- a technique is invasive if it enters the body (e.g. brain surgery)
- a technique is non-invasive if it does not enter the body (e.g. EEG)
spatial resolution - temporal resolution
if a measurment has a high spatial resolution, it has a high accuracy in space
- this means that the recorded measurement closely maps the structures and details of the brain
if a measure has a high temporal resolution, it has a high accuracy in time
- this means that the recorded measurement closely corresponds to the changes in time that occur in the brain
deep-brain stimulation (DBS)
a neurosurgery in which electrodes are implanted into the brain that stimulate a targeted area with a low-voltage electrical current to trigger or facilitate behavior
- can be performed with the use of a stereotaxic apparatus (an instrument that allows to precisely target a specific area of the brain)
- can be used to treat Parkinson’s
- invasive technique
transcranial magnetic stimulation (TMS)
a procedure in which a magentic coil is placed over the skull to stimulate the underlying brain
- used to induce or disrupt behavior
- non-invasive technique
optogenetics
based on the discovery that light can activate certain proteins that do not occur naturally
chemogenetics
a transgenic technique in which genetics and synthetic drugs are combined to influence cells
irreversible lesion techniques
- electrolytic: burning by passing current through an electrode
- neurotoxic: intoxication through infusion of neuron-killing chemicals
- high-intensity focused ultrasound (HIFU): heating with focused ultrasonic beams
- permanent lesions lead to compensation (neuroplasticity)
reversible lesion techniques
- regional cooling (temporarily shutting down a part of the brain)
- local administration of GABA agonist (temporary inhibition)
single cell recording
it is possible to measure the activity of individual cells by measuring a single action potential of a neuron with electrons applied to the brain
- also possible to record the electrical activity of clusters of neurons
- disadvantages: an electrode can kill a cell, and this cannot be done in an awake and actively moving animal or human
electroencephalography (EEG)
the electrical activity of the brain is measured by an EEG
- electrodes are attached to the scalp and each electrode measures the electrical activity of the corresponding brain area below the scalp
- measures the summed graded potentials (ESPSs and IPSPs) of many thousands of neurons that are simultaneously active
- high temporal resolution and low spatial resolution
- non-invasive and inexpensive
event-related potentials (ERPs)
shortchanges in an EEG signal in response to a discrete sensory stimulus produce a complex wave-like EEG called event-related potential
- are graded potentials on dendrites that are triggered by a sensory stimulus
- are difficult to see in the EEG because they are surrounded by many other electrical signals in the brain
- solution: repeatedly offer the stimulus and then average the responses
magnetoencephalography (MEG)
the magnetic counterpart of the EEG or ERP
- non-invasive procedure that allows to measure the magnetic activity of the brain
- high temporal resolution and spatial resolution
- better spatial resolution than EEG due to magnetic waves being less distorted by the scalp and brain tissue
- more expensive
computed tomography (CT)
a static imaging technique that produces a three-dimensional image of the brain by measuring X-ray absorption in the brain
- x-ray absorption varies with different tissue densities
- high-density tissue absorb a lot of ratiation, low-density absorbs little radiation
- mostly used to localize bone fractures, brain tumours, and brain lesions
- low temporal resolution and high spatial resolution
- inexpensive, but invasive due to x-rays which can damage DNA
magnetic resonance imaging (MRI)
MRI is the magnetic counterpart of CT
- produces a three-dimensional image by bringing a strong magnetic field into the brain, followed by a radio wave
- the radio signal is measured from hydrogen atoms contained in water molecules
- in this way, MRI can distinguish between areas with a high amount of water and areas with a low amount of water
- possible to distinguish between grey and white matter
- low temporal resolution and high spatial resolution
- more expensive and slow compared to CT
diffusion tensor imaging (DTI)
DTI is an MRI method that can map the paths of nerve fibre tracts in the brain by detecting the directional movement of water molecules
- useful to identify changes in axon myelination
magentic resonance angiography (MRA)
MRA is an MRI method that focuses on blood vessels
- it is useful to detect aneurysms, blood clots, and any disease of blood vessels
functional magnetic resonance imaging (fMRI)
a dynamic method based on MRI in which changes in brain activity are recorded by measuring the changes in blood flow and in blood constituents such as iron, glucose, and oxygen
- active brain areas have an increased blood flow, so fMRI can detect which brain areas become active during movement or rest
- fMRI has a high spatial resolution and low temporal resolution
near-infared spectorscopy (NIRS)
NIRS is an example of optical tomography, a technique based on the principle that an object can be reconstructed by gathering the light transmitted through it
- NIRS uses infrared light to record brain activity
- infrared light is injected into the scalp and a detector measures its reflection after it has travelled through the superficial layers of the brain
- allows to measure the average cortical oxygen consumption
- high temporal resolution and high spatial resolution
- non-invasive and inexpensive
positron emision tomography (PET)
an imaging technique that detects changes in blood flow by measuring changes in the uptake of compounds such as oxygen and glucose
- used to analyse the metabolic activity of neurons
- reasonably high spatial resolution and low temporal resolution
- involves the injection of radioactively charged water (partially invasive)
- very expensive
glioma
a tumour of glial cells
- tend to grow everywhere and are barely operable
meningiomas
a tumour of the meninges
- generally easier to operate on
