Paper 1: Ticklishness

Question 1

What is the big question of the paper?

Answer 1

What are the neural correlates of tickling?

Question 2

What are neural correlates?

Answer 2

patterns of neural activity that correlate with neural behaviour (specific stimuli)

Question 3

What are the major questions in tickle research? (4)

Answer 3

• Why does tickling induce laughter?
• Why are tickling effects so mood-dependent?
• Why do body parts differ in ticklishness
• Why can’t we tickle ourselves?

Question 4

What does Fig 1 show?

Answer 4

• tickling induces ultrasonic vocalizations (USVs)
• chasing play also induces USVs

Question 5

What does Fig 2 show?

Answer 5

somatosensory cortex responses to tickling and gentle touch

• analyzing trunk somatosensory cortex in the left hemisphere

Question 6

Figure 2 Conclusions: Layer 5a trunk somatosensory neurons…

Answer 6

• fire more during trunk tickling than trunk gentle touch
• fire more during tickling, gentle touch, and hand chasing than during break periods
• in general, neurons that increased during tickling also increased during hand chasing

Question 7

What does Fig 3 show?

Answer 7

stressed rats don’t appreciate tickles

• rats that are stressed out are less likely to produce USVs in response to tickling

Question 8

Why are the results of Fig 3 important?

Answer 8

• mood-dependent modulation of sensory cortex has rarely been reported
• results support Darwin’s idea that “the mind must be in a pleasurable condition” for ticklish laughter
• since human ticklishness is also modulated by mood, tickling is likely to be a very old and conserved form of social interaction

Question 9

What is a peristimulus time histogram?

Answer 9

histogram of neural activity

processed like raster plots – take different trails, average across them, and make them all relative to a set time point

Question 10

What does Fig 4 show?

Answer 10

spike timing predicts USV onset

• biggest response in layer 5a
• stimulation of cortex elicits USVs (Fig. 4G-I) – stimulation of deep layers of trunk somatosensory cortex is sufficient to elicit rat laughter (sufficiency experiment – adding neural activity by stimulating cortex)

Question 11

What did the same researchers find and report in another paper?

Answer 11

• used tickling to train rats to play hide and seek
• rats seek out tickling, but will disengage if there’s too much tickling