8.4.2 - Psychology: Measures of stress (biological measures)

how is the heart rate measured using ECG

heart rate measured via ECG = researchers found heart rate increases in acute stressed individuals & decreases in chronic stressed individuals (schubert et al)
- heart rate also be measured by taking pulse & using a watch

how is the heart rate measured using heart rate variability (HRV)

heart rate variability (HRV) = variation in time between heartrates = may indicate stress = normal variation increases & stressed variation decreases
- HRV measured via EEG = detect heartrate by measuring blood flow

how is brain function measured using fMRI

scanning machine = records brain activity by recognising changes in blood oxygenation & blood flow to brain
- brain’s active = more blood flow to area increases = represented in different colours = indicate different degrees of activities

what was the aim of wang et al

study central circuitry of psychological stress using fMRI

what was the methodology of wang et al

32 participants = 25 placed experimental group & 7 control group
- experimental participants rested for 15 minutes before having fMRI = had 4 scans of 8 minutes & full anatomical scan
- scan 2 & scan 3 done in same order to eliminate contamination of control condition = higher levels of emotions due to higher stress

what were the different conditions of wang et al

scan 1 = baseline = no task

scan 2 = low-stress condition = participants count aloud from 1000 = controls activation of verbal & auditory centres

scan 3 = high-stress condition = serial substraction of 13 from 4-digit number & respond verbally quickly = any errors had to restart task

scan 4 = final baseline = no task

what was the methodology of wang et al (2)

control participants had 4 scans in same length of time = didn’t perform any task during scans
- participants in both groups completed self-report stress scale (1-9) & saliva samples collected before & after scan = reported levels of effort, frustration & difficulty = heart rate recorded every 2 minutes

what were the results of wang et al

ventral right prefrontal cortex (RPFC) = continous activation during & after stress task = serves role for biological & behavioural stress responses
- supported previous research = RPFC activation associated with negative emotions
- sustained activation of RPFC is consistent with previous research findings of emotional networks = fMRI can measure stress

what were the conclusions of wang et al

psychological stress → negative emotions & vigilance
- central right prefrontal cortex plays central role in stress response

evaluate strength of using fMRI in wang et al

fMRI = measuring stress uses internal contrast agent = non-invasive method compared to PET scan (uses radioactive tracer) = safer for participant reducing risk of psychological harm

evaluate strength of validity in wang et al

more objective for measuring stress = requires less subjective interpretation = use of fMRI scans = more reliable & valid way measuring stress

evaluate weakness of using fMRI’s findings in wang et al

expensive & time-consuming = number of participants in studies are low = reduces validity of results & generalisability of findings to wider population

evaluate weakness of using fMRI in wang et al

measures stress = not direct measure of neural activity of brain = fMRI measures blood flow changes in brain > neural activity = areas ‘causing’ stress is complex & difficult = uncertain to say RPFC is associated with function of stress