Difference between revisions of "Data analysis - Maritime Defender"

Revision as of 08:27, 19 March 2011

Maritime Defender

The game begins with MD_MaritimeDefenderGameBegin (41) and ends with MD_DotCoherenceEstimate (6). The game also is considered to have ended if the begin code for any other mini-game occurs.

Independent Components Analysis

For the shooter phase, ICA can be applied to epochs beginning with MD_ShooterOpenWormholeSuccess and ending with MD_ShooterActivateFireWeapon, MD_ShooterEnemyWeaponFired, or MD_ShooterCollectibleSpawned, whichever comes first.

For the navigation phase, ICA can be applied to the entire continuous EEG record from the first MD_DotTrialBegin after the MD_DotPhaseBegin, up till the first event that is NOT any of MD_DotTrialBegin (2), MD_DotTrialExpire (3), MD_UserRespondLeft (4), MD_UserRespondRight (5), or MD_CockpitDamageFeedback (42).

Potentials related to behavioural inhibition

Go trials and no-go trials each can be successful or unsuccessful; there are therefore four categories of events each beginning with an MD_ShooterPresentFriendly (21) which signals a no-go trial or an MD_ShooterPresentEnemy (22) which signals a go trial. The analysis software should use the context provided by subsequent events to translate these two codes into four codes as follows:

At an MD_ShooterPresentFriendly (21), if there is no MD_ShooterActivateFireWeapon (24) until the next MD_ShooterCollectibleSpawned (28) or until 5 seconds have elapsed, whichever is sooner, then code this event as MD_ShooterNoGoSUCCEED. Otherwise code MD_ShooterNoGoFAIL. This new event code replaces the originally logged D_ShooterPresentFriendly, and is inserted into the data at the time time stamp as the originally logged event.

At an MD_ShooterPresentEnemy (22), if there is no MD_ShooterActivateFireWeapon (24) until the next MD_ShooterEnemyWeaponFired (27) or until 5 seconds have elapsed, whichever is sooner, then code this event as MD_ShooterGoFAIL. Otherwise code MD_ShooterGoSUCCEED. This new event code replaces the originally logged D_ShooterPresentFriendly, and is inserted into the data at the time time stamp as the originally logged event.

MD_ShooterActivateFireWeapon events within MD_ShooterNoGoFAIL sequences should be re-coded as MD_ShooterWeaponFALSE_ALARM. MD_ShooterActivateFireWeapon events within MD_ShooterGoSUCCEED sequences should be re-coded as MD_ShooterWeaponHIT.

As a behavioural measure, the mean and standard deviation of reaction time for MD_ShooterGoSUCCEED can be calculated from the intervals between the relevant MD_ShooterPresentEnemy and MD_ShooterActivateFireWeapon events. Also, d' can be calculated where hits are MD_ShooterGoSUCCEED, misses are MD_ShooterGoFAIL, false alarms are MD_ShooterNoGoFAIL, and correct rejections are MD_ShooterNoGoSUCCEED.

Motor and preparatory potentials

For the events MD_ShooterActivateMovePort (17), MD_ShooterActivateMoveStarboard (19), and MD_ShooterActivateOpenWormholeBeam (14), both the bereitschaftspotential (readiness potential, from supplementary motor area) ERP and the event-related desynchronisation of the mu rhythm near the hand area (lateral central electrodes) can be computed.

The interval between MD_ShooterOpenWormholeSuccess (16) and MD_ShooterGoSUCCEED will evoke a Contingent Negative Variation at frontocentral electrodes which resolves into a motor execution. The interval between MD_ShooterOpenWormholeSuccess (16) and MD_ShooterNoGoSUCCEED will evoke the same Contingent Negative Variation, followed by a further inhibition-related negativity instead of by motor execution. Both the CNV beginning at the time of MD_ShooterOpenWormholeSuccess and the response-related activities time-locked to MD_ShooterGoSUCCEED and MD_ShooterNoGoSUCCEED are of interest.

As a behavioural measure, between each pair of MD_ShooterPresentWormhole (23) and MD_ShooterOpenWormholeSuccess (16), both the elapsed time and the number of distinct movement commands (MD_ShooterActivateMovePort (17) or MD_ShooterActivateMoveStarboard (19)) can be computed.

Potentials related to motion perception

Leftward-drifting trials and rightward-drifting trials each can be successful or unsuccessful; there are therefore four categories of events each beginning with an MD_DotTrialBegin (2). The analysis software should use the context provided by subsequent events to translate this code into six codes as follows:

At an MD_DotTrialBegin Direction=Left followed by MD_UserRespondLeft as the very next event, code MD_DotLeftHIT, and similarly at an MD_DotTrialBegin Direction=Right followed by MD_UserRespondRight as the very next event, code MD_DotRightHIT.

At an MD_DotTrialBegin Direction=Left followed by MD_UserRespondRight as the very next event, code MD_DotLeftFALSE_ALARM, and similarly at an MD_DotTrialBegin Direction=Right followed by MD_UserRespondLeft as the very next event, code MD_DotRightFALSE_ALARM.

At an MD_DotTrialBegin Direction=Left whose next event is neither MD_UserRespondLeft nor MD_UserRespondRight is an MD_DotLeftMISS, and similarly an MD_DotTrialBegin Direction=Right whose next event is neither MD_UserRespondLeft nor MD_UserRespondRight is an MD_DotRightMISS.

MD_UserRespondLeft events following MD_DotLeftHIT, and MD_UserRespondRight events following MD_DotRightHIT, should be re-coded as MD_DotResponseHIT.

MD_UserRespondRight events following MD_DotLeftFALSE_ALARM, and MD_UserRespondLeft events following MD_DotRightFALSE_ALARM, should be re-coded as MD_DotResponseFALSE_ALARM.

MD_CockpitDamageFeedback events immediately following MD_DotResponseFALSE_ALARM events should be re-coded as MD_DotFeedbackFALSE_ALARM. MD_CockpitDamageFeedback events immediately following MD_DotTrialBegin events should be re-coded as MD_DotFeedbackMISS.

ERPs and ERSPs time-locked to each of the six MD_Dot stimulus onset events can be compared; pilot data indicate that the ERSPs would show event-related desynchronisations in occipital generators. (There might not be sufficient FALSE_ALARM events for reliable averaging, in which case just the HIT and MISS events can be compared.) Likewise, ERPs and ERSPs time-locked to each of the three (or two, if there are insufficient numbers of false alarms) MD_DotResponse events can be compared.

Potentials related to reward

MD_ShooterCollectibleCollision (29) and MD_ShooterMeteorExplosion (30) both can be examined for a cingulate negativity related to reward value which occurs between 250 and 350 ms post-stimulus; see Yeung et al. http://dx.doi.org/10.1093/cercor/bhh153

Potentials related to error processing

MD_ShooterWeaponFALSE_ALARM events should generate a cingulate error-related negativity; this error-related negativity can be most straightforwardly visualised by computing a difference wave: subtract the ERP associated with MD_ShooterWeaponHIT events from the ERP associated with MD_ShooterWeaponFALSE_ALARM events.

During the navigation phase, a couple of strategies might be applied to discern the error-related negativity associated with erroneous responses: The right way to do it, if there were enough MD_DotResponseFALSE_ALARM events available for reliable ERP averaging, would be to subtract the ERP associated with MD_DotResponseHIT events from the ERP associated with MD_DotResponseFALSE_ALARM events. But there probably won't be sufficient numbers of false-alarm responses for that. Instead of false alarms, subjects who are unable to discern the motion direction probably will generate misses - that is, no overt behavioural response at all. So we can look at the ERP associated with MD_DotFeedbackMISS (without any subtraction).