Chapter 5: The Research Methods of Biopsychology (Part 1)

measuring chemical activity of the brain

(1) 2-deoxyglucose (2-DG) technique (2) cerebral dialysis

fMRI advantages over PET

(1) Nothing has to be injected into the subject (2) It provides structural and functional information in the same image (3) Better spatial resolution (4) Can produce 3D images of activity over the entire brain

Radioactivity-based techniques: PET

- 1st functional brain image - FDG dye into carotid artery -FDG accepted by energy consuming cells -FDG not metabolized ->accumulates in active neurons -shows levels of radioactivity in many parts of 1 horizontal layer of the brain -"image"= colored map of amnt of radioactivity of each cubic voxel that make up the scan -SIGNIFICANT APPLICATION- id-ing distribution of molecules of interest (ie neurotransmitters) in brain

Measures of SNS activity: EMG

- indicator of psychological arousal -between 2 electrodes on skin of measured muscle -increase in muscle contraction= increase in amplitude -Raw EMG spiking used to make integrated signal - amplitude provides continuous measure of the level of muscle tension

electrical events

-action potentials -postsynaptic potentials -electrical signals from the skin, muscles, blood, eyes

Noninvasive stimulation techniques: TMS (transcranial magnetic stimulation)

-causal effects of human cortical activity on cognition + behavior -turn off area of human cortex by making mag. field under coil next 2 skull (different stim turns it on) -questionable safety, depth of effect, mechanism of neural disruption

X-ray based techniques: CT (computed tomography)

-computer assisted -combined individual horizonal x-rays to make 3-D image

X-ray based techniques: Cerebral Angiography

-contrast x-ray technique (uses dye to heighten contrast) ie: Radio-opaque dye to cerebral artery to see cerebral circulatory system -most useful for localizing vascular damage (locate tumors based on displacement of blood vessels

warning about lesions

-difficult to interpret -cannot destroy structure w/o sig damage to adjacent structures -unilateral lesions milder than symmetrical bilateral lesions therefore difficult to detect -experimental studies of lesion affects are bilateral lesions studies

Measures of ANS activity: Skin Conductance

-emotional thoughts/experiences ↑ sweat production ↑ ability of skin to conduct electricity 1) Skin Conductance level (SCL)- background level of conductance x particular situation 2) Skin Conductance level (SCR)- transient changes in skin conductance x discrete experiences

Measures of brain activity EEG

-gross electric activity in the brain -electrodes to scalp procced by electroencephalograph -shows sum of electrical events through the head -some EEG waves forms associated with particular states of consciousness (alpha waves=relaxed wakefulness) or particular types of cerebral pathology (epilepsy)

Magnetic-field-based Techniques: fMRI

-influential tool of cognitive neuroscience -used in medical diagnosis -produces images showing increase blood flow to active areas of brain (BOLD signal) -bad at recording timing

Lesion methods: Aspiration Lesions

-lesion area of cortical tissue -tissue must be accessible to eyes and instruments of surgeon -sucking part out w glass pipet

Measures of ANS activity; ECG

-measure elect. signal associated w each heartbeat through electrodes placed on chest used to derive changes in hear rate or measure heart rate variability (assesses vagal tone)

Measures of brain activity: MEG

-measures changes in magnetic fields on surface on scalp made by changes in patterns of neural activity -only magnetic signals on surface of brain can be measured

Measures of SNS activity: EOG

-records eye movements -steady potential difference exists between front (positive) and back (negative) of the eye ball

noninvasive stimulation technique: tDCS (transcranial direct current stimulation)

-stimulate area of cortex w electrical current -electrodes on scalp - stim inc activity in part of brain

Magnetic-field-based Techniques: MRI

-structural brain imaging - high res from radio-frequency waves of H atoms - align w powerful magnetic field -clearer imaging than CT (high spatial res) - 3D image

Electrical stim methods

-usually delivered across 2 tips of bipolar electrode -weak pulses of current produce immediate ↑ in firing of neurons near the tip -has behavioral affects -opposite to those produced by lesion to the same site -depends on location of tip, parameters of current + test environment -has been administered to conscious humans

Magnetic-field-based Techniques: Diffusion Tensor Imaging

-variation of MRI -ID of pathways of H2O molecules diffusing rapidly (major tracks of the brain) -info on connections among brain structures (connectome)

Locating Neurotransmitter + receptors in the brain

1) Immunocytochemistry 2)In situ hybridization

What does an ERP recording include

1) response to stimulus (the signal) 2) on going background EEG activity (the noise) - signal averaging used to reduce noise

Locating Neurotransmitter + receptors in the brain: In situ hybridization

1)hybrid RNA strands w complementary base seq of mRNA that synthesizes target neuroprotein are obtained 2)hybrid RNA strands labeled w dye/radioactive element 3)Brain slices = exposed to labeled hybrid RNA strands tht bind to complementary mRNA strands -marks location of neurons tht release target neuroprotein

Routes of Drug Administration

1)oral 2intragastrically 3) peritoneal cavity of abdomen (intraperitoneally, IP) 4)large muscle (Intramuscularly, IM) 5)fatty tissue beneath the skin (subcutaneously, SC) 6)large surface vein (intravenously, IV) PROBLEM : many drugs don't pass through blood brain barrier SOLUTION: administer in small amounts through cannula in brain

Measures of ANS activity: Blood pressure

2 independent measurements 1) systoles - peak pressure during heart contraction 2) diastoles- minimum pressure during heart relaxation ratio : systolic/diastolic (mmHg)

Invasive Recording methods: Invasive EEG recording

EEG signals recorded from laboratory animals large implanted electrodes cortical signals rec through stainless steel skull screws subcortical signals rec through stereotaxically implanted wire electrodes

Measures of brain activity EEG- ERPs

ERP= change in EEG signal based on momentary sensory stimulus analysis of average evoked potentials (AEPs) hones in on the various waves of the averaged signal each wave characterized by: -direction -+/- latency

Fluorescence+ brainbow techniques

Green fluorescent protein (GFP)- bright green fluorescent protein when exposed to blue light stra

methods of visualizing or stimulating the living human brain

X-ray based Techniques Radioactivity-based techniques Magnetic-field-based Techniques Noninvasive stimulation techniques

Locating Neurotransmitter + receptors in the brain Immunocytochemistry

a method for detecting a particular neuroprotein in brain y labeling their antibodies w a dye or radioactive element then exposing slices of brain tissue to labeled antibodies regions of dye or radioactivity accumulation in brain slices = locations of target neuroprotein -targets generally include enzymes that synthesize specific neurotransmitters

Invasive recording methods: Extracellular unit recording

action potentials of neuron through a microelectrode positioned in extracellular fluid next to it moving animals bc flexible micro-electrodes used to rec. 1 neuron at a time now up to 100

Invasive Physiological Methods

all preformed with animal subjects all involve stereotaxic surgery -lesion methods -electrical stimulation methods -invasive recording methods

measuring chemical activity of the brain: 2-deoxyglucose (2-DG) technique

animal injected w radioactive 2-DG in test situation -neurons active during test absorb 2-DG @ high rate but not metabolized slices subjected 2 autoradiography ↑ levels of radioactive 1-DG = black spots on slides later color coded

Lesion Methods: Knife Cuts

cutting or sectioning used to eliminate conduction in a nerve or tract

Invasive recording methods: multiple-unit recording

electrode top is much larger than micro electrode picks up many signals from many neurons action potentials picked up by the electrode def into integrating circuit (adds them together) -produces graph of number or rec. AP/unit of time

stereotaxic surgery

experimental devices are precisely positioned in the depths of the brain 1) stereotaxic atlas: where to put things 2) stereotaxic instrument: tools for implantation

Lesion Method: Radio-frequency lesions

high frequency current through target tissue via electrode heat from current destroys tissue size/shape of lesions determined by duration/intensity of current + configuration of electrode tip human studies- diction circuit study Parkinson's

Selective Chemical Lesions

injecting neurotoxins that have an affinity for certain components of the nervous system -kainic acid+ibotenic acid -6-OHDA

Optogenetics

insert opsin gene into particular type of neuron to use light to hyperpolarize or depolarize neurons

opsins

light-sensitive ion channels found in cell membranes of certain bacteria/algae open when illuminated depending on type of opsins- can polarize/depolarize cell membrane

unlike brain-imaging techniques, TMS permits the study of ____ between human cortical activity and cognition

links

measuring chemical activity of the brain: cerebral dialysis

measuring extracellular concentration of specific neurochemicals in behaving animals implantation of fine tube w short semipermeable section in brain structure of interest neurochemicals tht diffuse into tube: analyzed by chromatograph

2 methods used by biopsychology

methods used to study the nervous system methods used to study behavior used in research AND clinical settings

Invasive recording methods: Intracellular unit recording

moment-by-moment record of graded fluctuations of one neuron's membrane potential most experiments on chemically immobilized animals to prevent electrode from moving

Lesion Methods: Reversible lesions

non destructive temporarily eliminate activity in particular area of brain -cooling or injecting anesthetic into target structure same subjects can be studied multiple times (lesion+control conditions) used in young animals to find developmental affects

Lesion Methods

part of brain is damaged, destroyed, or inactivated -resulting behavior used to find function of lesioned structure

P300 wave

positive wave that occurs about 300 milliseconds after a momentary stimulus that has meaning for the subject

a patient is sometimes injected with radioactive fluorodeoxyglucose before

positron emission tomography

gene knockout

procedures for creating organisms tht lack particular gene under investigation mice most used species (knockout mice) many genes discovered (melanopsin) 1 gene, interaction, + epigenetic mechanisms also involved

gene replacement techniques

replace one gene with another insert pathological genes from human to mice (transgenic mice) treat neurological disease by replacing faulty genes replace bases tht act as switch 2 turn gene off or on in particular chemicals or points of development