Chapter 7 - Measuring and Manipulating Brain and Behavior

Question 1

how to study humans with brain lesions

Answer 1

can be investigated in a postmortem examination or with a neuropsychological test

Question 2

neuropsychology

Answer 2

the study of the relationship between brain functions and behavior in human beings

Question 3

behavioral neuroscience

Answer 3

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

Question 4

anatomical (static) - functional (dynamic)

Answer 4

• 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

Question 5

invasive - non-invasive

Answer 5

• 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)

Question 6

spatial resolution - temporal resolution

Answer 6

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

Question 7

deep-brain stimulation (DBS)

Answer 7

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

Question 8

transcranial magnetic stimulation (TMS)

Answer 8

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

Question 9

optogenetics

Answer 9

based on the discovery that light can activate certain proteins that do not occur naturally

Question 10

chemogenetics

Answer 10

a transgenic technique in which genetics and synthetic drugs are combined to influence cells

Question 11

irreversible lesion techniques

Answer 11

• 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)

Question 12

reversible lesion techniques

Answer 12

• regional cooling (temporarily shutting down a part of the brain)
• local administration of GABA agonist (temporary inhibition)

Question 13

single cell recording

Answer 13

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

Question 14

electroencephalography (EEG)

Answer 14

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

Question 15

event-related potentials (ERPs)

Answer 15

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

Question 16

magnetoencephalography (MEG)

Answer 16

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

Question 17

computed tomography (CT)

Answer 17

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

Question 18

magnetic resonance imaging (MRI)

Answer 18

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

Question 19

diffusion tensor imaging (DTI)

Answer 19

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

Question 20

magentic resonance angiography (MRA)

Answer 20

MRA is an MRI method that focuses on blood vessels
- it is useful to detect aneurysms, blood clots, and any disease of blood vessels

Question 21

functional magnetic resonance imaging (fMRI)

Answer 21

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

Question 22

near-infared spectorscopy (NIRS)

Answer 22

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

Question 23

positron emision tomography (PET)

Answer 23

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

Question 24

glioma

Answer 24

a tumour of glial cells
- tend to grow everywhere and are barely operable

Question 25

meningiomas

Answer 25

a tumour of the meninges
- generally easier to operate on