Week 6 Reading 3 - Psychophysiological Methods in Neuroscience PDF

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Psyc Psychophysiol hophysiol hophysiologic ogic ogical al Methods in Ne Neuroscience uroscience Intro • • • • •

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psychophysiological methods are used across a variety of disciplines in order to answer diverse questions about psychology, both mental events and behavior Allows research consumers to evaluate the meaning of the results in a particular experiment Psychophysiology methods: any research in which the dependent variable is a physiological measure and the independent variable is behavioral or mental These measures can provide information about processes including emotion, cognition, and the interactions between them Subset of the very large domain of neuroscience methods o Neuroscience methods: A research method that deals with the structure or function of the nervous system and brain Many neuroscience methods are invasive (procedure that involves the skin being broken or an instrument or chemical being introduced into a body cavity) This present survey emphasizes noninvasive methods widely used with human subjects Inferences can be made about someone’s cognitive or emotional state based on his or her selfreport, physiology, or overt behavior

History •

Phineas gage – railroad worker in mid 19th century got into an accident and part of his left frontal lobe was lost o As a result, his personality seemed to change, he became more impulsive, had trouble carrying out plans, and sometimes engaged in vulgar profanity which was out of character o This case study leads us to believe that specific areas of the brain are associated with certain psychological phenomena

Central Nervous System (CNS) • •

The Following psychophysiological methods focus on the CNS Structural magnetic resonance imaging (sMRI) o noninvasive technique that allows researchers and clinicians to view anatomical structures within a human o Placed in magnetic field 66,000 times greater than the earth’s magnetic field which causes a small portion of the atoms in a body to line up in the same direction o Body pulsed with low-energy radio frequencies that are absorbed by the atoms into the body causing them to tip over

When the atoms return to their aligned state, they give off energy in the form of harmless electromagnetic radiation o A machine measures this energy and transforms it into a 3D picture of the tissue within the body Functional Magnetic Resonance Imaging (fMRI) o Used to assess changes in activity of tissue o Builds on principles of sMRI o Uses property that when neurons fire, they use energy which must be replenished o Glucose and oxygen are two key components for energy production which are supplied from the bloodstream o Oxygen is transported through the blood through hemoglobin which is the oxygen carrying part of a red blood cell (has binding sites for oxygen) ▪ When these sites become saturated with oxygen ----> oxygenated hemoglobin ▪ When the oxygen molecules have been released from a hemoglobin molecule, ---> deoxygenated hemoglobin o When a set of neurons begin to fire, oxygen in the blood surrounding those neurons is consumed ▪ To compensate, the body provides an abundance of oxygenated hemoglobin in the blood surrounding that activated neural tissue ▪ When the activity in the neural tissue declines, the level of oxygenated hemoglobin returns to its original level o fMRI measures change in concentration of oxygenated hemoglobin which is known as the blood-oxygen-level-dependent signal o Facts about fMRI ▪ measures blood volumes and flow which helps us to infer neural activity (does not measure neural activity directly) ▪ Data typically has poor temporal resolution (on order of seconds) ▪ When combined with sMRI, provides excellent spatial resolution (on order of millimeters) o Typically, there is an inverse relationship between spatial and temporal resolution o May be used prior to neurosurgery to identify areas associated with language so that the surgeon can avoid those areas o Valuable for identifying specific areas of the brain that are associated with different physical and psychological tasks Electroencephalography (EEG) o Another technique to study brain activation o Uses at least 2 and sometimes up to 256 electrodes to measure the difference in electrical charge (voltage) between pairs of points on the head o The electrodes measure the electrical activity that is naturally occurring within the brain o Measures neural activity directly (contrasting fMRI) o Electrodes can also be placed on the brain itself – this application is called electrocorticography (ECoG) o

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Typically used prior to medical procedures to localize activity (ex. Origin of epileptic seizures) ▪ More invasive but very precise localization of neural activity ▪ Obviously not justifiable for research purposes o High temporal resolution (data can be recorded thousands of times per second) Magnetoencephalography (MEG) o Another technique for noninvasively measuring neural activity o Flow of electric charge (current) associated with neural activity produces very weak magnetic fields that can be detected by sensors placed near the participant’s scalp o Number of sensors varies from a few to several hundred o Special rooms shielded from magnetic fields in the environment are needed to avoid contamination of the signal being measured o High temporal resolution like EEG, and better spatial resolution o Less susceptible to distortions skull and scalp because magnetic fields can pass through hard and soft tissue relatively unchanged Positron emission tomography (PET) o Medical imaging technique used to measure processes in the body – including the brain o Relies on a positron-emitting tracer atom introduced to the bloodstream in a biologically active molecule such as water or glucose o A positron is a particle having the same mass as an electron except with a positive charge o Tracer molecule will emit positrons which are detected by a sensor so the spatial location of the tracer molecule can be determined o Allows researchers to construct an image of areas of the brain that have the highest metabolic needs o Usually represent neural activity that has occurred over tens of minutes (poor temporal resolution) o PET images often combined with computed tomography (CT) images to improve spatial resolution, as fine as several millimeters o Tracers can also be incorporated into molecules that bind to neurotransmitter receptors which gives researchers insight on the action of neurotransmitters Transcranial magnetic stimulation (TMS) o noninvasive method that causes depolarization or hyperpolarization in neurons near the scalp ▪ Depolarization: change in membrane potential, inside of the cell more positive and increasing the chance of an action potential ▪ Hyperpolarization: change in membrane potential, making the inside of the cell more negative and decreasing the chance of an action potential. o Not considered psychophysiological because the independent variable is phycological rather than the dependent o Still considered neuroscience method because it deals with nervous system function and can be combined with conventional psychophysiological methods

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Coil of wire placed above patient’s scalp and when electricity flows through the coil, a magnetic field is produced ▪ This magnetic field travels through the skull and scalp affecting 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 and hyperpolarization (depending on the of magnetic field pulses) Single or paired pulse TMS depolarizes site-specific neurons in the cortex causing them to fire Can produce or block muscle activity if used over primary motor cortex Can produce sensations of flashes of light or impaired vision if used over visual primary cortex TMS able to explore neural plasticity: The ability of synapses and neural pathways to change over time and adapt to changes in neural process, behavior, or environment

Peripheral Nervous System (PNS) • •

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Psychophysiological methods focused on the peripheral nervous system which is the part of the nervous system outside of the brain and spinal cord Skin conductance o Measures the electrical conductance (the inverse of resistance) between two points on the skin, which varies with the level of moisture o Sweat glands responsible for the moisture and are controlled by the sympathetic nervous system (SNS): one of the two major divisions of the autonomic nervous system, responsible for stimulation of “fight or flight” activities o Increase in skin conductance can be associated with changes in psychological activity o Poor temporal resolution (entire response taking typically several seconds to emerge and resolve) Cardiovascular Responses o Measures heart rate, heart rate variability, blood pressure o Heart is innervated by the parasympathetic nervous system (one of the two major divisions of the autonomic nervous system, responsible for stimulation of “rest and digest” activities.) and SNS ▪ Input from PNS decreases heart rate and contractile strength, input from SNS increases heart rate and contractile strength o Heart rate can be easily monitored using a minimum of 2 electrodes ▪ Measured by counting number of heartbeats in given time period or by assessing the time between successive heartbeats o Psychological activity can prompt increases and decreases in heart rate making heart rate a sensitive measure of cognition o Changes in HR variability are associated with stress as well as psychiatric conditions

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Electrocardiogram used to measure heart rate and variability:

cardiovascular measures allow researchers to monitor SNS and PNS reactivity to various stimuli or situations Electromyography (EMG) o Measures electrical activity produced by skeletal muscles o Measures voltage between 2 points (like EEG) o possible to detect very small facial movements that are not observable from looking at the face o can be used to determine when a participant first initiates muscle activity to engage in a motor response to a stimulus o Temporal resolution very similar to that of EEG and MEG Eye Movements o Eye blinks, movements, and pupil diameter can provide valuable information o Eye blinks often assessed using EMG electrodes placed just below eyelid o Video method: camera used to record video of an eye ▪ Particularly valuable when determining absolute direction of gaze o Ex. when viewing pleasant or unpleasant images, people spend different amounts of time looking at the most arousing parts. ▪ This can vary as a function of psychopathology o Pupil diameter controlled by competing inputs from SNS and PNS (like heart rate) ▪ Commonly used as an index of mental effort when performing a task o

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When to Use What • •

if you are interested in what brain structures are associated with cognitive control, you wouldn’t use peripheral nervous system measures, a fMRI or PET might be more appropriate If you are interested in how cognitive control unfolds over time, EEG or MEG would be a good choice

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If you are interested in studying the bodily response to fear in different groups of people, peripheral nervous system measures might be most appropriate...