TMS and Perception (2)

Question 1

What did Walsh et al. (1998) state?

Answer 1

• “power of TMS as a lesion technique lies in the opportunity to combine reversible disruption with high degrees of spatial and temporal resolution
• examined studies on the use of TMS to investigate visual cognition

Question 2

What study did Amassian et al. (1989) conduct?

Answer 2

• the participants task was to report what 3 letters they saw on a screen
• the researchers applied one pulse of TMS at some delay (0-200ms) after the stimulus
• they recorded how many letters the participant could report

Question 3

What did Amassian et al. (1989) find?

Answer 3

• if given TMS at the same time or 200ms the stimulus appeared, people could still report accurately
• if given TMS at 80-100ms then people could not report the letters
• example of mapping when in time a process is occurring and interference of perception

Question 4

Which letter will be perceived first as the coil is moved laterally to the left hemisphere? to the right hemisphere?

Answer 4

• the left letter
• the right letter
• same trend for up and down

Question 5

What study did Amassian et al. (1993) conduct?

Answer 5

• they would flash three letters and then another 3 letters 100 ms later (visual mask)
• participants are asked to recall first 3 letters

Question 6

What is a visual mask?

Answer 6

• stimulus that comes 100ms after the first and it is known to interfere with ability to see the first stimulus

Question 7

What did Amassian et al. (1993) find?

Answer 7

• if they applied TMS 100 ms after the mask, people can report the original 3 letters because the TMS blocks the processing of the mask
• this is an example of facilitation of perception

Question 8

What is a control researchers can use in TMS experiments?

Answer 8

• hold the wand away from the head to see if just the sound of the TMS has an effect
• could also put wand over another area that shouldn’t affect the experiment

Question 9

What is extinction?

Answer 9

• when a participant only perceives ipsilateral stimulus when two stimuli are presented bilaterally
• for example: with damage to the right parietal lobe, an individual will report stimulus on left or right, but only on right when both are presented

Question 10

What study did Pascual-Leone et al. (1994) conduct?

Answer 10

• participants were to say if stimulus is on the right, left, or both sides
• they administered rTMS to the left or the right parietal lobe

Question 11

What did Pascual-Leone et al. (1994) find?

Answer 11

• there was visual extinction due to parietal rTMS

Question 12

What study did Ashbridge, Walsh and Cowey (1997) conduct?

Answer 12

• they had participants do a visual search task
• the participants had to find the different stimulus in conjunction and popout trials
• rTMS was applied to the right parietal cortex

Question 13

What is conjunction?

Answer 13

• when there are multiple kinds of distractors (colour and orientation) and it takes longer to respond the more distractors there are

Question 14

What is popout?

Answer 14

• when there is only kind of distractor and it takes the same amount of time to respond no matter how many distractors there are

Question 15

What did Ashbridge, Walsh, and Cowey (1997) find?

Answer 15

• there was no effect of TMS for popout trials
• if TMS was applied at 100 ms in conjunction trials, there was an interference
• this means that popout and conjunction trials use different neural mechanisms
• the neural mechanisms for conjunctions are linked to or in the right parietal cortex

Question 16

What did Ashbridge, Walsh and Cowey (1997) use as a control?

Answer 16

• applied rTMS to other regions (right occipitotemporal cortex and left parietal cortex)
• did not have an effect on conjunction

Question 17

What study did Walsh, Ashbridge and Cowey (1998) conduct?

Answer 17

• they conducted a similar study as their previous one but included extensive training
• they then introduced a new search array to the trained participants

Question 18

What did Walsh, Ashbridge and Cowey (1998) find?

Answer 18

• after extensive training, the effect of TMS went away
• it appears that with lots of training the attentional requirement went away
• with the new search array, participants were once again affected

Question 19

What study did Cohen et al. (1997) conduct?

Answer 19

• they had participants read braille or raised roman letters

- they held the coil over the mid-occipital region (visual) and started TMS at onset of reading

Question 20

What did Cohen et al. (1997) find?

Answer 20

• for early blind w/ braille: error rate was significantly higher for TMS to mid-occipital
• for early blind w/ Roman: error rate significantly higher for TMS to mid-occipital
• for sighted controls w/ roman: error rate significantly higher for TMS to somatosensory
• it seems the visual cortex has been recruited in early blind individuals