8. Intrusive Thoughts in a Sleep Deprived Mind

Question 1

intrusive thougnts

Answer 1

• we can be reminded about past experiences which trigger memories of those experiences
• these are not always pleasant

Question 2

think/no think task

Answer 2

• participants learn associations between 2 types of stimuli (typically a face and a scene)
• this is strongly encoded so when they see the face they see the scene
• think = faces in green box means you must try and think of the scene (1/3)
• no think = faces that appear in red box you must try and not think about the paired scene (1/3)
• they then give an intrusion score stating how hard it was to keep the scene out of their heads (2 or 3 means they couldn’t avoid thinking about it)
• typically see that p’s improve their memory suppression with each trial block
• almost 50% of trials have intrusions. however, individual differences are large
• important for understanding psychiatric disorders (PTSD, major depression)

Question 3

executive deficit hypothesis

Answer 3

• sleep plays a critical role in restoring and maintaining our cogntivie and executive functions
• it is hypothesised that sleep deprivation may underly the individual differences in memory suppression
• 4 lines of research gained as evidence for this hypothesis:
• top down suppression
• motor response inhibition
• mental fatigue
• psychiatry

Question 4

top down suppression - Gagnepain et al (2012)

Answer 4

• Gagnepain et al (2012)
• think no think task with fMRI = increased activity in the hippocampus when visualising scenes associated with faces
• successful no-think trails were coupled with a lack in hippocampal activity and an increase in PFC activity
• PFC actively inhibited intrusions
• during think trials the amygdala showed increased activation to negative images
• in successful no-think trials activation in the amygdala was suppressed

Question 5

motor response inhibition

Answer 5

• Drummons, Paulus & Tapert (2006)
• behavioural data showing sleep deprivation impairs memory suppression ability
• go/no go task - must respond to stimuli by pressing the space bar and ignore the other stimuli (e.g. box and circle)
• 23, 31 and 55 hours awake (baseline awake for 7h)
• ability to inhibit a motor response is impaired significantly when sleep deprived but all SD groups showed similar responses
• almost back to normal after 7 nights of recovery
• engages the same neural regions as inhibitory internal representations (such as memory)

Question 6

mental fatigue

Answer 6

van Schie and Anderson (2007)

• P’s has to suppress memories for 3 (S) or 10 (L) seconds
• the longer you had to suppress a memory, the more fatigued you become
• P’s get better each S trial
• P’s get better each L trial until they become mentally fatigued
• mental fatigue may tax executive function similar to sleep deprivation

Question 7

psychiatry

Answer 7

• memory intrusions are common in PTSD and major depressive disorder (Brewin et al., 2010)
• sleep disturbances experienced by up to 90% of patients with these disorders (key symptom) - (Koffel et al., 2001)

Question 8

memory control and emotion

Answer 8

• Gagnepain, Hulbert and Anderson (2017)
• P’s learnt assocations between faces and scenes
• P’s were shown faces and told to avoid thinking about the scene
• greater success associated with less negative subjective ratings in subsequent rating task
• data suggests that repeatedly suppressing emotionally negative thoughts renders them less aversive

Question 9

Anderson (in press)

1. does sleep deprivation influence memory suppression ability?
2. does sleep deprivation influence affective benefits of memory suppression?

Answer 9

• 68 images, half positive and half negative
• P’s rated how they made them feel whilst also being recorded for HR and skin conductance
• images were presented for 6 seconds (as pair)
• faces were presented alone for 4s
• regardless of whether the P’s associated the scene correctly, the correct pair was shown for 3.5s
• participants then remained awake throughout the night in the lab whilst others slept

Question 10

Anderson (in press) - results

Answer 10

• think trials elicited more intrusions than no-think trials
• sleep deprived group reported more memory intrusions
• intrusions became less frequent with repeated suppression (but if sleep deprived, this reduction was inhibited)
• benefits of memory suppression for down regulating subsequent intrusions were diminished in sleep deprivation group compared to control
• greater intrusion control predicted a shift towards more positive affective evaluations of negative ‘no-think’ scenes
• for rested individuals, suppression might be an effective way of down regulating emotional tone of negative memories (implications for disorders?)