(1+2) Psychophysiology - Introduction + Methods and Techniques

history - mid-1950s

the term "psychophysiologist" was coined

1964

Journal of Psychophysiology-AlbertAx

1960

Society for Psychophysiological Research, Chester Darrow as the first president

Luigi Galvani

animals produce electricity that originates within the organism itself

-> how electricity improves people's health

Vigouroux

Measured skin resistance while the hysterical symptom was transferred from side to side

-> habituation of skin resistance: diminution of a response to repeated stimulation

Mueller

changes in skin resistance appeared to correlate with changes in psychological state

Veraguth

believed that he found a new reflex, sensitive to emotional factors

-> influenced Jung: combined the measure of skin resistance with a word-association procedure

Jung

- with Veraguth: combined the measure of skin resistance with a word-association procedure

- with Ricksher: Skin resistance responses related to attention to stimulus and ability to associate it with preview occurrences, either conscious or unconscious

capillary electrometer

- first instrument capable of reproducing a continuous record of a rapidly changing bioelectrical event

- 1870s

- Tube filled with sulfuric acid and mercury. The electrical activity would change the shape of the mercury meniscus

1887: Waller

first recorded the electrical activity of the human heart using electrodes on the skin

Einthoven

developed string galvanometer

1929 - Berger

- first EEG, measuring electrical activity from the brain

- Berger demonstrated EEG changes related to eye opening, large-scale stimuli, mental activity, and attention

physiological measures are acquired on what kind of participants?

- noninvasively

- awake human

recording techniques focusing on central nervous system

EEG and MEG

EEG and MEG investigates....

investigate the degree to which different parts of the brain "talk" to each other

-> better understanding of brain networks

EEG measures

the difference in electrical charge between pairs of points on the head

-> investigate the change in amplitude or frequency components of the recorded EEG on an ongoing basis of averaged over dozens of trials

EEG pros and cons

- pros: temporal resolution:

Data can be recorded thousands of times per second -> allows researchers to document events that happen in less than a millisecond

- cons: localization of the activity is less precise because it's measured from the scalp (electrical activity must travel through the skull and scalp before reaching the electrodes)

MEG measuring conditions

Due to the fact that the magnetic fields of interest are so small, special rooms that are shielded from magnetic fields in the environment are needed in order to avoid contamination of the signal being measured

MEG pros and cons

- excellent temporal resolution

- better spatial resolution than EEG, not as susceptible to distortions from the skull and scalp

+ Magnetic fields are able to pass through the hard and soft tissue relatively unchanged

- much more expensive than EEG

methods focus on studying peripheral nervous system

skin conductance

cardiovascular responses

muscle activity

pupil diameter

eye blinks

movement

skin conductance response (SCR) measures

the electrical conductance (the inverse of resistance) between two points on the skin, which varies with the level of moisture

SCR mechanism

- Sweat glands are responsible for this moisture and are controlled by the sympathetic nervous system (SNS)

- Increases in skin conductance can be associated with changes in psychological activity

SCR temporal resolution

poor: the entire response typically takes several seconds to emerge and resolve

Cardiovascular measures (ECG or EKG) measures:

heart rate, heart rate variability (HRV) and blood pressure

+ Heart is innervated by the PNS and SNS: input from PNS decreases heart rate and contractile strength, input from SNS increases heart rate and contractile strength

why is heart rate a sensitive measure of cognition?

psychological activities prompt increases and decreases in heart rate, often in less than a second

EMG (electromyography) measures

electrical activity produced by skeletal muscles

EMG's purposes

- determine when a participant first initiates muscle activity to engage in a motor response to a stimulus

- The degree to which a participant begins to engage in an incorrect response even if it's never visibly executed

- Emotion research to identify activity in muscles that are used to produce smiles and frowns, detecting not observable facial movements

Eye blinks - measuring methods

- EMG electrodes places just below the eyelid, or on the face near the eyes, which generate voltage across the entire eyeball

- using a camera to record video of an eye

Neuroimaging tools

sMRI, fMRI, PET, fTCD, TMS

why are these techniques not considered traditionally psychophysiological

because psychophysiology mainly grounds in electrical signal analysis

Structure MRI purposes

- view anatomical structures within a human

- Compare the size of structures in different groups of people

- Increase the accuracy of spatial locations as measured with fMRI

sMRI mechanism

- The participant is placed in a magnetic field that may be 66,000 times greater than the Earth's magnetic field, which causes a small portion of the atoms in his or her body to line up in the same direction

- The body is then pulsed with low-energy radio frequencies that are absorbed by the atoms in the body, causing them to tip over

- As these atoms return to their aligned state, they give off energy in the form of harmless electromagnetic radiation, which is measured by the machine

- The machine then transforms the measured energy into a three-dimensional picture of the tissue within the body

fMRI purpose

- assess changes in activity of tissue

- identifies specific areas of the brain that are associated with different physical or psychological tasks

- may be used prior to neurosurgery in order to identify areas that are associated with language so that the surgeon can avoid those areas during the operation

- comparing brain activation in different tasks and/or populations

fMRI mechanism

- measures the change in the concentration of oxygenated hemoglobin (blood-oxygen level dependent - BOLD - signal), not neural activity directly

- mechanism:

+ Oxygen is transported through the blood using hemoglobin, which contains binding sites for oxygen: when these sites are saturated with oxygen, it is referred to as oxygenated hemoglobin; when the oxygen molecules have all been released from a hemoglobin molecule, it is known as deoxygenated hemoglobin

+ As a set of neurons begin firing, oxygen in the blood surrounding those neurons is consumed, leading to a reduction in oxygenated hemoglobin; the body then compensates and provides an abundance of oxygenated hemoglobin in the blood surrounding that activated neural tissue

fMRI temporal and spatial resolution

- poor temporal, excellent spatial

- Temporal resolution for fMRI is typically on the order of seconds, whereas its spatial resolution is on the order of millimeters

Positron emission tomography (PET) mechanism

- relies on a positron-emitting tracer atom that is introduced into the bloodstream in a biologically active molecule, such as glucose, water, or ammonia

- A positron is a particle much like an electron but with a positive charge; one example of a biologically active molecule is fludeoxyglucose, which acts similarly to glucose in the body

- Fludeoxyglucose will concentrate in areas where glucose is needed—commonly areas with higher metabolic needs.

- Over time, this tracer molecule emits positrons, which are detected by a sensor; the spatial location of the tracer molecule in the brain can be determined based on the emitted positrons

allows researchers to construct a three-dimensional image of the areas of the brain that have the highest metabolic needs, typically those that are most active

PET resolution

- temporal - poor: represents neural activities that have occurred over tens of minutes

- often combined with CT to improve spatial resolution

Functional transcranial doppler sonography (fTCD) measures:

cerebral perfusion changes

fTCD pros and cons

- pros:

+ noninvasive, easy to apply

+ can be applied in individuals with limited cooperative ability

+ excellent temporal resolution: based on a close coupling between regional cerebral blood flow changes and neural activation

- cons:

+ Highly operator dependent

+ 10-15% rate of inadequate acoustic windows prevalent in Blacks, Asians, and elderly women: may relate to thickness and porosity of the bone

+ Only provide index of global rather than local cerebral blood flow velocity

fTCD mechanism

utilizes pulse-wave Doppler technology to record blood flow velocities in the anterior, middle, and posterior cerebral arteries:

- Ultrasound waves emitted from the Doppler probe are transmitted through the skull and reflected by moving red blood cells within the intracerebral vessels

- The difference in the frequency between the emitted and reflected wave (Doppler shift frequency) is directly proportional to the blood flow velocity

fTCD - how to obtain measures from blood flow velocity

using spectral analysis

- Parameters include: peak systolic velocity (Vs), pulsatility index (PI), time-averaged mean maximum velocity (Vmean)

- Vmean: a continuous trace of peak velocities as a function of time, and in most fTCD instruments, it is calculated and displayed automatically

insonation of the cerebral arteries is only possible through thinner regions of the skull (acoustic windows):

Transtemporal window

Transorbital window

Submandibular window

Suboccipital window

Transcranial magnetic stimulation (TMS) purpose

- studying the function and timing of specific processes

- Explore neural plasticity: the ability of connections between neurons to change

TMS mechanism

- causes depolarization or hyperpolarization in neurons near the scalp

- a coil of wire is placed just above the participant's scalp: when electricity flows through the coil, it produces a magnetic field

- This magnetic field travels through the skull and scalp and affects neurons near the surface of the brain

- When the magnetic field is rapidly turned on and off, a current is induced in the neurons, leading to depolarization or hyperpolarization, depending on the number of magnetic field pulses

- Single or paired pulse TMS depolarizes site-specific neurons in the cortex -> cause them to fire

TMS's effects

- If this method is used over primary motor cortex, it can produce or block muscle activity, such as inducing a finger twitch or preventing someone from pressing a button

- If used over primary visual cortex, it can produce sensations of flashes of light or impair visual processes: TMS is a valuable tool in studying the function and timing of specific processes such as the recognition of visual stimuli

- repetitive TMS produces more long-lasting effects than the initial stimulation: depending on intensity, coil orientation, and frequency, the neural activity in the stimulated area may be either attenuated or amplified

if you are interested in what brain structures are associated with cognitive control, you use:

fMRI or PET

If you are interested in how cognitive control unfolds over time, you use

EEG or MEG

If you are interested in studying the bodily response to fear in different groups of people, you use

peripheral nervous system measures

The key to decide what method is the most appropriate

properly defining the question that you are trying to answer

important questions to ask when choosing a method

What aspects are most interesting?

Do you care about identifying the most relevant brain structures?

Temporal dynamics?

Bodily responses?

why isn't TMS considered a psychophysiological measure?

the independent variable is physiological, rather than the dependent

when do we use camera to record movement of the eye?

this method is particularly valuable when determination of absolute direction of gaze (not just change in direction of gaze) is of interest, such as when the eyes scan a picture

calibration phase of eye tracking

- a participant looks at multiple, known targets

- eye position is then extracted from each video frame during the main task and compared with data from the calibration phase -> allowing researchers to identify the sequence, direction, and duration of gaze fixations

Walter Cannon

formulated the principle of the emergency functions of the sympathico-adrenal system

Ax (1964) - general goal of psychophysiology

the description of the systems in the organism which transfer information between the two collections of sub-systems generally referred to as psyche and soma

Law of Initial Value

- the direction of response of a body function to any agent depends to a large degree on the initial level of that function

-> is necessary to adjust the tolerance for detecting responses