Introduction to Neuroimaging 29-09-2023 Peripheral measures (1).pdf

Introduction to Neuroimaging Peripheral measures 29.09.2023 Ruth M Krebs, Dept. of Experimental Psychology, Ghent University 1 Overview Nervous System … all other lectures today… 2 Peripheral nervous system: Autonomic https://www.physio-pedia.com/index.php?curid=17983 3 Peripheral nervo...

Introduction to Neuroimaging Peripheral measures 29.09.2023 Ruth M Krebs, Dept. of Experimental Psychology, Ghent University 1 Overview Nervous System … all other lectures today… 2 Peripheral nervous system: Autonomic https://www.physio-pedia.com/index.php?curid=17983 3 Peripheral nervous system: Autonomic Autonomic Sympathetic (SNS) Parasympathetic (PNS) Fight or flight Rest and digest Can have systemwide effects (interconnected ganglia) Tends to affect one organ at a time 4 Overview 1. 2. 3. 4. 5. Skin conductance Pupillometry Cardiac activity Respiration Muscle activity 5 1. Skin conductance Skin conductance  Reflects fairly pure SNS activity (fight/flight) that is not “contaminated” by PNS influences  Arousal stimulates sweat glands (cools down body)  Sweat is conductive and changes the Electro-Dermal Activity (EDA)  Mostly interpreted as an index of arousal intensity in affective or cognitive processing (not positive vs. negative valence) 6 1. Skin conductance Method:  Two electrodes are applied to the volar surfaces of the fingers or palm of the non-dominant hand (dominant hand is used for the task)  A very small constant voltage is applied and the amount of current that passed is interpreted as skin conductivity  Typical units are microsiemens (μS) or micromhos (μmho) 7 1. Skin conductance Different measures:  Skin conductance level (SCL): a tonic measure of skin conductance during a task, large interindividual differences (absolute values not very menaingful, but interesting for block manipulations)  Non-specific skin conductance response (NS-SCR): spontaneous phasic changes in electrical conductivity  Event-related skin conductance response (ER-SCR): a phasic response to a certain event (stimulus-locked), latency: 1-3 sec  most interesting for us 8 1. Skin conductance Example: Responses to affective events (Öhman & Soares 1994)  Skin conductance is often used in fear conditioning research to detect the magnitude of a person’s fear response to conditioned stimuli  The fear response of individuals is selective for a certain stimulus type 9 1. Skin conductance Example: Economic decision making (Crone et al. 2004)  Gambling task with 2 advantageous and 2 disadvantageous options  Anticipatory skin conductance was increased for disadvantegous options in good performers, which likely led to better decisions in this group 10 Overview 1. 2. 3. 4. 5. Skin conductance Pupillometry [see also eye-tracking lecture] Cardiac activity Respiration Muscle activity 11 2. Pupillometry Pupil size  First and foremost, the pupil reacts to changes in luminance  but also reflects fluctuations in the autonomic nervous system High luminance Low luminance Arousal Surprise Mental effort “Adaptation in uncertain environment” Stimulation of SNS Stimulation of PNS Underlying mechanism Noradrenergic neurons (monkey) (locus coeruleus in the brainstem) Pupil diameter in target detection task See Gilzenrat et al. 2010 12 2. Pupillometry Method:  An infrared light source illuminates the eye, and an infrared-sensitive camera captures the contrast between dark pupil and iris  When luminance is kept constant, changes in pupil size can reflect cognitive processes during an experimental task  Avoid luminance differences between conditions in your experiment! http://adrianglasser.com/projects/projects.html 13 2. Pupillometry Example: Surprise in performance monitoring (Braem et al. 2015)  Classic conflict task: judge central target, ignore distractors  Pupil size measured after congruent and incongruent trials 14 2. Pupillometry Pupillometry < > Eye-tracking Although eye-tracking uses the same setup as pupillometry, it is different from the other peripheral measures in that is more “controlled”. Hence, it is more related to behavioral measures such as reaction time and accuracy. There will be a full lecture dedicated to eye-tracking! 15 Overview 1. 2. 3. 4. 5. Skin conductance Pupillometry Cardiac activity Respiration Muscle activity 16 3. Cardiac activity The heart  Transports oxygen from lungs, as well as nutrients, waste products, and regulatory substances (endocrines)  It responds most to exercise (has to be controlled during cognitive tasks)  Cardiac cycle: Initiation of cycle via sino-atrial (SA) node (pacemaker), intrinsic rythm of 105 bpm, slowed down by the PNS, sped up by the SNS  further signal conduction via atrial-ventricular (AV) node 17 3. Cardiac activity Main methods and measures of interest  Electrocardiography (ECG): • Heart rate (HR) • Heart rate variability (HRV)  Impedance cardiography / Impedance variation (ICG): • Pre-injection period (PEP) 18 3. Cardiac activity Electrocardiography (ECG)  Recording of electrical activity via surface electrodes  No direct measure of action potentials, but reflects production and conduction of action potentials in the heart during cardiac cycle 19 3. Cardiac activity Measure of interest: Heart rate (HR)  Based on RR interval, beats per minute (bpm)  HR = 60/(RR interval in seconds)  sensitive to emotional processes, influenced by SNS and PNS 20 3. Cardiac activity Example: Affective picture processing (Bradley et al. 2012)  Heart rate decreases when orienting attention to emotional pictures  This reflects PNS influence  In contrast to skin conductance (elavated for emotional pictures) But, the more popular observation is this:  If emotional events require actions  Or when effectively being in fear, under stress, or angry  Heart rate will increase  This reflects SNS influence 21 3. Cardiac activity Measure of interest: Heart rate variability (HRV)    Changes in the time intervals between consecutive heartbeats (RR interval); termed Inter-beat Intervals (IBIs) Reflects general measure of the influence of the PNS on the heart Very generally, high HRV predicts better cogntitive perfromance 22 3. Cardiac activity Main methods and measures of interest  Electrocardiography (ECG): • Heart rate (HR) • Heart rate variability (HRV)  Impedance cardiography / Impedance variation (ICG): • Pre-injection period (PEP) 23 3. Cardiac activity Impedance cardiography (ICG)  Total electrical conductivity of the thorax and its changes over time  High-frequency current is flowing between an electrode pair (via aorta)  Impedance changes are picked up by a second pair  Returns Impedance pulse wave (IMP) and the ICG curve (1st derivative) 24 3. Cardiac activity Measure of interest: Pre-ejection period (PEP)  Time interval from the electrical stimulation of the ventricles to the opening of the aortic valve (~Pumping performance)  Thought to reflect the effect of the SNS on the heart 25 3. Cardiac activity Example: effort mobilization in affective context (Glendolla & Silvestrini 2011)  PEP is used to assess effort mobilization in a letter detection task  Affective stimuli modulate PEP: shorter PEP when experiencing sad stimuli  It is argued that the sad context makes the task more difficult 26 3. Cardiac activity Additional methods (for completion, not exam material):    Photoplethysmography (PPG) Phonocardiography Blood pressure 27 3. Cardiac activity Photoplethysmography (PPG)  Pulse oximeter: shining infrared light into tissue and measuring reflection  Rather rough measure, can index vasoconstriction (SNS) 28 3. Cardiac activity Phonocardiography  Sound recording of the heart (top = ECG, bottom = phonocardiography) 29 3. Cardiac activity Blood pressure  Systolic (force produced by heart) and diastolic (heart at rest) blood pressure  systolic blood pressure (SBP) rises with exercise, caffeine, anxiety, stress  But: also mental effort mobilization (see Gendolla & Sivestrini 2011) 30 Overview 1. 2. 3. 4. 5. Skin conductance Pupillometry Cardiac activity Respiration Muscle activity 31 4. Respiration Respiratory activity  Measured via belt around the chest  Relationship between respiration and heart rate Different measures of interest: • Respiratory rate (most relevant for cognitive neuroscience) • Inspiration time • Expiration time • Inspiration to Expiration ratio 32 4. Respiration Example: Respiration in cognitive tasks (Backs & Seljos 1996)  Effects of working memory and inter trial interval on respiration  Respiration rate increases with cognitive load and paradigm speed 33 Overview 1. 2. 3. 4. 5. Skin conductance Pupillometry Cardiac activity Respiration Muscle activity Autonomic PNS 34 Peripheral nervous system: Somatic https://www.physio-pedia.com/index.php?curid=17983 35 Overview 1. Skin conductance 2. Pupillometry 3. Cardiac activity 4. Respiration 5. Muscle activity Somatic PNS 36 5. Muscle Activity Electromyogram (EMG)  Measures electrical field changes due to muscle action potentials (allows us to be in close contact with the motor cortex)  Two electrodes above the muscle of interest, plus ground electrode  Always on striated muscle, needs stimulation to contract via motor nerves (different from the cardiac muscle discussed earlier) Different measures of interest • Blink reflex  integration of autonomic and somatic system! • Facial EMG • Motor EMG • [motor EMG during TMS  see TMS lecture!] 37 5. Muscle Activity: Blink reflex Blink reflex, or “startle reflex”  Measured by surface electrodes below the eye (orbicularis oculi muscle)  Induced by external stimulation (air puff, touch/pain, light flash, sound)  Integration of autonomic and somatic PNS! 5. Muscle Activity: Blink reflex Example: effect of affective stimuli on the blink reflex (Bradley & Lang 2000)  Blink reflex to light flash is stronger during unpleasent sounds  And this correlates with subjective pleasentness ratings e.g., gun fire e.g., bird song 39 5. Muscle Activity: Facial EMG Facial EMG  Measured by surface electrodes above different facial muscles  Typically above the eye (currogator) and on the cheek (zygomaticus)  To measure responses to affective stimuli, but also during cognitive processing Zygomaticus muscle (“smile”) (picture credit: van Boxtel, 2010) Currogator muscle (“frown”) 40 5. Muscle Activity: Facial EMG Example: facial EMG in a conflict task (Cannon et al. 2010)  Participants categorized objects (garage or kitchen?) with left or right hand  Grip of the object could be compatible or incompatible with response hand “smile” “frown” 41 5. Muscle Activity: Motor EMG Motor EMG  Measured by surface electrodes above peripheral muscles (here, index finger)  Can be used during cognitive tasks that require manual responses ground 42 5. Muscle Activity: Motor EMG Example: EMG to detect partial errors in a conflict task (Burle et al. 2002)  Simon task: respond to stimulus color and ignore the position  EMG will show muscle activaty of the response finger (correct hand)  but also small activations of intended but not executed responses of the incorrect hand: “partial errors”  evidence for response conflict Simon task illustration taken from van den Wildenberg et al. 2010 43 Why are these in a neuroimaging lecture?  Measures of immediate responses of the peripheral nervous system can complement insights from behavioral and neuroimaging data  Although most of the methods are relatively old (e.g., used in emotion research), there is a new interest in basic and applied neuroscience today (e.g., affective processing of effortful tasks)  Some measures can (and should) be considered as “nuisance” variables that influence other measures of interest (e.g., heart rate and respiration can affect the hemodynamic response in fMRI)  From all the ones mentioned, pupil dilation and eye-tracking are most often used in the research conducted at our department 44