I wouldn’t trust the results of the Reward vs Loss task, as they are mostly random noise with some structured artifact.
Matt. From: <hcp-users-boun...@humanconnectome.org<mailto:hcp-users-boun...@humanconnectome.org>> on behalf of Zhuochen Wang <zhuoc...@usc.edu<mailto:zhuoc...@usc.edu>> Date: Thursday, September 27, 2018 at 5:00 PM To: "Burgess, Gregory" <gburg...@wustl.edu<mailto:gburg...@wustl.edu>> Cc: "hcp-users@humanconnectome.org<mailto:hcp-users@humanconnectome.org>" <hcp-users@humanconnectome.org<mailto:hcp-users@humanconnectome.org>> Subject: Re: [HCP-Users] Gambling tfMRI Hi Greg, I really appreciate your response. fMRI is not my area of expertise yet so I might be asking obvious questions here: is it meaningful to extract trials of the same type across blocks and perform analysis on trial types instead of block types? I'm mainly looking at reward vs baseline and would like to compare reward trials vs neutral trials only, instead of comparing mostly reward blocks vs fixation blocks. This can also remove confounds from visual stimuli. The visual hyperactivation in Reward vs Baseline makes sense, although in Reward vs Loss the visual cortex is still significantly activated despite the same visual stimulus. I'm also surprised by the hyperactivation of dorsal striatum and the hypoactivation of nucleus accumbens and vmPFC. The literature suggested that nucleus accumbens and vmPFC are consistently activated by reward tasks, and dorsal striatum is functionally dissociated from ventral striatum and tend not to be activated by stationary reward tasks. Given decades of replicable, converging evidence from rodents, primates, and human imaging studies, I'm inclined to give credence to the literature. Since I know HCP has a large sample size, high quality images, and state-of-the-art data processing protocols, I can't really think of why the results partially deviate from the literature besides two possible reasons. 1. a mixture of trial types in a block confounded the results 2. the task did not recruit the regions as intended due to its predictable design. I suspect it's a mixture of the two. For example, in a "mostly reward" block, participants quickly realized the high occurrence of reward, and activation in reward processing regions such as ventral striatum and vmPFC drops as expectation adapts, but were soon surprised by the infrequent alternative outcomes so a different pattern of activation occurs corresponding to processing loss or the absence of reward. So although loss/neutral trials only occupy one or two trials out of eight trials, they might have a disproportionally large effect on the average activation results due to the "surprise element". In fact, the literature suggests that unexpected absence of reward could cause hypoactivation in nucleus accumbens. Do you think this might have contributed to the unexpected results? HCP data has made enormous contributions to neuroscience and my sole intention is to make sure I understand the data and analysis properly so I don't misuse the results. I really appreciate your help. Best, Bryan ________________________________ From: Burgess, Gregory <gburg...@wustl.edu<mailto:gburg...@wustl.edu>> Sent: 27 September 2018 10:26:58 To: Zhuochen Wang Cc: hcp-users@humanconnectome.org<mailto:hcp-users@humanconnectome.org> Subject: Re: [HCP-Users] Gambling tfMRI The rationale for using a blocked design versus event-related design is discussed in Barch et al. 2013. In general, blocked designs have higher sensitivity than event-related designs. The event-related design showed the same pattern of activation, but was less sensitive. Therefore, the blocked design was preferred. If your concern is about the activation of visual cortex, keep in mind which contrast you were reviewing. The Reward vs. Baseline contrast will identify all regions that are more active for the task than passively viewing a fixation cross. The visual stimuli associated with the Gambling task simply cause more activation than a fixation cross. Consider looking at the Reward vs. Loss contrast. That should reduce your concern about loss and neutral trials being confounded, because that contrast subtracts similar activity out. --Greg ____________________________________________________________________ Greg Burgess, Ph.D. Staff Scientist, Human Connectome Project Washington University School of Medicine Department of Psychiatry Phone: 314-362-7864 Email: gburg...@wustl.edu<mailto:gburg...@wustl.edu> On Sep 26, 2018, at 6:18 PM, Zhuochen Wang <zhuoc...@usc.edu<mailto:zhuoc...@usc.edu>> wrote: Hello, During reading Barch et al 2013's group tfMRI results for the incentive processing task, I was baffled by the highly significant activation in the visual cortex and dorsal striatum in Reward vs Baseline. I wasn't aware that these two regions can be differentially activated by a reward task after reviewing the literature. It was also interesting to see nucleus accumbens being absent from the activation map. Then I realized that they used "mostly reward" and "mostly punishment" blocks as two predictors of the GLM instead of using "reward", "punishment", and "neutral" trials. This means the "punishment" or "neutral" trials within the "mostly reward" blocks can confound results associated with reward. The same argument goes for results associated with punishment. So I was wondering if anyone knows why they did it this way and if this is a valid method. Perhaps I'm missing something obvious here? Sincerely, Bryan (Zhuochen) Wang, M.S. 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