This weeks readings provided a new angle for thinking about Mind Wandering. Rather than examine what the effects are and what the possible implications are the studies this week examined the cognitive implications of default network activity. I found all of the research interesting, however not all of them we equally convincing.
As explained by all the authors, Default Neural Activity occurs in an area of the brain (made up of many smaller regions) know as the Default Neural Network (Also known as Default Mode Network). This activity is most frequently noted while the indivual is at rest and not performing an attention demanding task - one that does not call very much on their executive control (Mason et. al., 394). It seems that when an individual becomes engaged in an attention demanding task this DMN activity lessens. However this explanation is more complex and dependant on the way one interprets a lot of research. There is some disagreement among researchers as to what the DMN's role actually is. Some believe that rather than simply activate during non attention demanding tasks, the DMN in some way monitors the way we take in our environment. It is not as black and white as either doing a task 100% or not. Furthermore other researchers from this week have additional theories as the the manner in which the DMN functions, though upon initial reading I thought these were small differences in semantics, I actually think many of the ideas presented in these articles work well together to make sense of a complex concept.
The most compelling and comprehensive article for me was Stawarczyck et. al.'s "Neural Correlates of Ongoing Conscious Experience: Both Task-Unrelatedness and Stimulus-Independence are related to Default Network Activity." Stawarczyck did an excellent job of presenting the complexity of the topic while still maintaining a clear study and exploring the possible implications. The main issue that he addresses is the question of the active role of the DMN. One theory is the one initially mentioned, "higher FMN activity corresponds to a shift of perspective from current external information to internally generated cognitions." The other explored by Stawarczyck states, "DMN activity might support the general unfocused monitoring of the external environment rather than internal thoughts" (Stawarczyck et. al., 1).
Stawarcyzyck theorizes that inorder to properly test thins, experimenters cannot simply try and measure Task-Unrelated thoughts, or Mind Wandering, and so he creates a much more specific and valuable system. He categorizes thoughts during a task into 4 categories which take in two paramaters. Whether they are stimulus dependant or independent and whether the thoughts are task related or unrelated. According to Stawarcyzyck et. al's plan this will allow them to evaluate each of these types of thoughts separately and monitor the brain regions accordingly.
Stimulus- dependent & Task-related means that the individual is completely focused on the task at hand.
Stimulus-dependent & Task-unrelated means that the individual is engaging with a stimulus in the room that is not part of the task and should not be looked on.
Stimulus-independent & Task-related means that the individual is thinking about the task they are doing but is not engaging with any stimuli in the room - this is a more internally directed thought flow.
Stimulus independent & Task-unrelated is the only classification of Stawarcyzyck's that counts as mind wandering because the individual is neither thinking about task nor distracted/engaging with stimuli in the room.
Stawarcyzyck measured and compared the brain activity of individuals who reported to be in hese distinct categories when prompted during an attention demanding task. This is a step toward a solution to an issue of categorizing mind wandering that has come up several times throughout the class and does a nice job of explaining some of the difference in neural activity between stimulus-dependent imaging and stimulus-independent imaging.
The experimenters essentially found the results they participants perform better when reporting that they have stimulus-dependent and task-related thoughts and this coincided with decreased activity in the DMN. However the interesting further step of this study allows for a complication of the function of the DMN. Rather than just state that in general the DMN leads to more internal thoughts that are unrelated to environment, the DMN had specific areas spike for task-unrelated thoughts and different spikes for stimulus-independent thoughts. This is importnat because it leads t the possibility that there is an additive quality to the DMN. It is not simply black and white on and off but rather more a spectrum of mind wandering. The more the regions activate the more the individual may mind wander.
This possibility seems the most likely to me after all the readings, but contrasts in an interesting way with the Fox reading. In "The human brain is intrinsically organized into dynamic, anticorrelated functional networks" Fox et. al. focused more on the dichotomy between the default network where they state "task-negative"responses are and the "task-positive areas of the brain which activate when an attention demanding task is being performed. Fox et. al. look at this relationship a lot like one would picture a seesaw.
The resting state of the human mind is a highly active default network which allows for a lot of mind wandering. When a task demands out attention the activity in the DMN (or task negative area) dies down and simultaneously the activity of the task positive areas increase. As one moves up or down the other moves inversely to accomodate it.
This is a very on or off approach to the default network and is not quite in line with Stawarcyzyck's proposal. The latter allows for fluidity and shades of gray while the former is very black and white. Nevertheless Fox's proposal's accounts for the resource allocation theories that had come up in the past by researchers like McVay. Instead of assuming that there are a finite number of cognitive resources that can be attributed to attention demanding tasks, Fox asserts that once the task positive or task negative area of the brian is being called upon the seesaw must tip and activate it.
The evidence for Fox lies in the fact that the relationship between the two brain regions exists even when an individual is not explicitly working on a task. It is just a natural function of the human mind. This again is somewhat at odds with Stawarcyzyck who would say that activation of the DMN becomes more intense in accordance with the small subsections of the region that are activated (Stawarcyzyck et. al., 9).
The Mason et. al. article "Wandering Minds: The Default Network and Stimulus-Independent Thought" addressed a question similar to Fox et. al.'s are areas activated during rest implicated in mind wandering? The assertion here is that simply because the area is activated does not mean that it is the cause of mind wandering. In this study they induced a state of mind wandering during blocks of verbal and visiospatial tasks, checked that the activations areas were associated with the DMN, and checked against participant self reports of mind wandering. The study concluded that "the tonic activity observed in the default network during conscious resting states is associated with mind wandering" (Mason et. al., 394).
Aside from the lack of detail in this article, I was most unsatisfied by the assertion that "a significant positive relation between the frequency of mind-wandering and the change in BOLD signal observen when participants performed "practiced: relative to "novel" blocks" (Mason et. al. 394). Perhaps it is just due to the lack of detail provided but I am unsure how a probe/ sampling method of the participants can indicate more SITs. When probed the participant either reports a SIT or does not. If the researchers probed 10 times and received 6 instances of SITs and then did the same number of probes, they still cannot be sure what is happening between probes. Perhaps the individual reports 8 SITs simply because they are mind wandering at different times during the task.
For me the least compelling of all the studies was the Andrews-Hanna article, "Evidence for the Default Network's Role In Spontanous Cognition." It seemed redundant and over ambitious in terms of goals and essentially demonstrated thing that other articles had done more efficiently. Despite this, I thought the design of the study was at times clever and interesting. It was just a struggle to understand the theoretical intentions of the experiments and once those intentions were understand I found I was disappointed and uninterested.
There were three main conditions in the experiment. 1) External Attention where participants were told to look for brief flickers on a surface to which they should attend. The flickers would occur on the peripheries of their vision. This was the broad condition
2) was also external attention with the alteration that the flickers would occur on the central part of the screen making this the focal condition. 3) Passive/Spontaneous Cognition Condition participants were asked to look at a corsshair on the center of a screen knowing that there would be no stimulus. 4) There was also a control condition in which a set of participants completed the tasks and were prompted for information about their mind wandering while in a fake fMRI machine. This allowed the experimenters to get real time information from the subjects without disrupting the scan.
The experimenters were testing multiple things in this experiment. The first being if the DMN is used for general external attention by comparing the scans of conditions 1 and 2 to condition 3. Then they tested if the DMN is important for borad external attention by comparing activity on the brain scans of conditions 1 and 2. Finally they tested if the DMN is for internal meditation or thought by checking if DMN activity is weakest in the external attention conditions. The results indicated that the the last hypothesis was correct and had the most statistical significance
The most interesting results to come from this experiment was the fact that thought the broad focus condition did not achieve anywhere enar as many SIT repots, it did have more than the focal condition.
This result is interesting in so much as it again somewhat goes against the Fox et. al. black and white view of the DMN. There seems to be a continuum along which mind wandering occurs and not simply an easy switch. I therefore hold on to my support of the Stawarcyzyck et. al. study.
References:
Andrews-Hanna, JR., Reidler JS., Huang C., Buckner RL. (2010). Evidence for the
Default Network's Role In Spontanous Cognition. J Neurophysiol: 104 322-335.
Default Network's Role In Spontanous Cognition. J Neurophysiol: 104 322-335.
Fox, Michael D., Snyder, Abraham Z., Vincent, Justin L., Corbetta, Maurizio., Van Essen, David D., Raichle, Marcus E. (2005). The Human Brain is Intrinsically Organized Into Dynamic, Anticorrelated Functional Networks. PNAS: 102 9673-9678.
- Mason, Malia F., Norton, Michael I., Van Horn, John D., Wegner, Daniel M.m Grafton, Scott T., Macrae, C. Neil. (2007). Wandering Minds: The Default Network and Stimulus-Independent Thought. Science: 315
