Transcription
Hi everyone, welcome back to another lesson. We're talking about the brain's default mode network in this lesson. So, we're going to talk about where in the brain this default mode network is located. We'll also talk about important functions it performs, and we'll also talk about some different psychological problems that can occur if the default mode network isn't working properly.
So, the default mode network is a pattern of brain activation that occurs during a resting state. So, it's different brain structures that activate together when we're in a resting state. And during states of focus or attention, the default mode network becomes deactivated. So, this default mode network was actually originally found accidentally in other brain imaging studies where they had patients doing some cognitively stimulating activity. And then in between each of those activities, researchers noticed this pattern of brain activation that occurred during rest. So, this is where we see the default mode network.
Now, when the default mode network is activated, there are particular structures in the brain that become activated. That's the that pattern of brain activation we talked about before. So, when the default mode network is activated, these are the parts of the brain that are activated. More specifically, those locations include the dorsal medial prefrontal cortex, which is this location here in the frontal lobe of the brain, the ventromedial prefrontal cortex, which is this area of the frontal cortex, the inferior parietal lobes, which are on the inferior aspect of the parietal lobes, which is this lobe here of the brain, the temporoparietal junction, which is the junction between the temporal lobe and the parietal lobe, the posterior cingulate cortex, which if we were to split the brain in two and look between the two hemispheres, the posterior cingulate cortex is this area here, and then the hippocampus is also a part of the default mode network, which is not in the diagrams we've shown.
So, these particular structures in the brain that become activated occur bilaterally. They occur in both hemispheres. And it has been noted that the default mode network is more activated in particular regular age groups. So, it's more activated in adulthood as compared to very young childhood and very old age. So, the extremes of age seem to have lower activity of the default mode network. And these structures seem to be more highly associated and more interconnected with each other in female patients. So, a couple of important and interesting notes to point out here.
Let's talk about the functions and the purposes of the default mode network. So, one of the most important functions that this particular network does is mind wandering and daydreaming. So, in those states where we're not actively doing something and we are at rest, where we let our mind wander or perform daydreams, this is when the default mode network is activated.
Other important functions that this network performs is self-reflection and self-referential and introspective thoughts. So, thinking about yourself, thinking about things that you've done or mistakes you've made, all of those are going to be important parts of this network as well. Processing of episodic memory is also an important function of the default mode network. So, this is going to include recollecting past memory, so thinking about past memories or thinking about autobiographical memories. So, especially autobiographical memories, so thinking about things that happened to you personally in the past, you're going to be utilizing your default mode network.
This is going to be more likely to be active. Planning for the future is also another part of the default mode network. So, what we would call prospective memory. So, you're thinking about a possible future plan or future situation. You're utilizing the default mode network. And these two particular functions, the processing of episodic memory and planning for the future, are generally activities performed by the posterior cingulate cortex, we mentioned that as an important brain structure in the default mode network.
Social awareness and cognition is also another important function of the default mode network. So, when you're engaging with somebody, and in those times where you're not really thinking about the engagement itself, you might be thinking about how what they've said relates to you or relates to what they've said in the past. So, all of that has to do with the default mode network as well.
And kind of abstracting a general idea from what we've just mentioned, the default mode network seems to play an important role in integrating past information with the current situation you're in, and also helping to plan for the future. So, it's involved as a sort of function of interplay between what you've heard and what you know before, and what you're experiencing now, and what you're going to do in the future. So, that all ties in with some of the processing of episodic memory, planning for the future, and social cognition. So, if you know somebody, what they've said in the past, you can input that into the current situation you're engaging in. So, all of that has to do with again, integrating past information with your current situation for ability to plan for the future.
And then it's also involved in utilization of schemas and narratives. Schemas are going to be these mental representations of parts of your environment or patterns of beliefs regarding your environment. And narratives are going to be stories that you have about particular situations. So, again, it seems to play a role in integrating past, present, and future information. So, it can be reminiscent of a story or narrative, and it can also help edit particular narratives you might have. So, if you have a particular story or narrative about a particular restaurant you go to, and then something changes at that restaurant, your default mode network engages with that new information and changes the narrative with regards to that restaurant. So, there's one interesting aspect of this pattern of activation of the brain, how it can modify certain narratives or stories you might hold about certain situations.
So, that's a lot of information, maybe hard to understand exactly what the default mode network is doing. But what we can take away here is that when the default mode network is deactivated or has lower activity, this is when the brain is engaging outwardly. We can think of it engaging outwardly, perhaps you're doing some outward goal-directed behavior or action. So, you're not really thinking about your future plan or a past memory, but now you're actively engaging in some process. This is when the default mode network is suppressed or it's deactivated. Whereas the default mode network is activated when you're thinking inwardly. So, inward or introspective thinking or planning. So, this is the way you can sort of remember when the default mode network is either deactivated or activated.
So, the default mode network is activated when you're actively or cognitively engaged in some activity. You're not thinking about any past memories, you're not wandering in your thoughts, you're simply focused on that task. Whereas when you're at a resting state, you're not focused on any particular task, your mind is wandering, you're thinking about the past, you're thinking about the future, that is when the default mode network is activated. So, I hope that helps as a way to remember when it's activated and deactivated.
Now, let's talk about the default mode network in associations with psychopathology. Now, it has been found that default mode network activity is altered in patients with major depressive disorder. For instance, it has been found that there is higher default mode network activity found in patients who are more likely to ruminate. Ruminating is when you're thinking about something that bothers you, perhaps a past memory that is troubling you, and you're thinking about that over and over and over again. That's rumination, and that's more likely to occur if you have higher default mode network activity.
It has also been found that individuals with higher neuroticism, this is one of the Big Five personality traits, so this is the trait that indicates high negative emotion. If someone has higher neuroticism, they are more likely to show higher levels of default mode network activation when hearing criticism as compared to patients with lower neuroticism. So, in those patients, they hear criticism from somebody, some personal criticism, and they keep thinking about it over and over again, they keep ruminating on that criticism. So, it's recollecting that past autobiographical memory over and over and over again, that's again part of the default mode network. So, we see higher levels of default mode network activation in those individuals.
It's also been demonstrated that individuals with generalized anxiety disorder have dysfunctional default mode network activity as well. So, we mentioned before that the default mode network is involved in thinking about the future. So, in patients with generalized anxiety disorder, they may be thinking about the future, certain anxiety-provoking things that are bothering them with regard to their future. So, in those patients, they may have higher default mode network activity because they're thinking about some future possibility that is causing them anxiety, for instance.
And then it's also been noted that there is structural and functional issues in the default mode network in patients with autism spectrum disorder as well. So, this makes sense as mentioned before, the default mode network is involved in social awareness, in social cognition. So, remembering being aware of what the person that you're interacting with now said to you before, and also what they're saying to you now, and putting that together and interacting with the person is all going to be important with regards to the default mode network. So, this makes sense that we can see particular issues in autism spectrum disorder in the default mode network.
Please check my lesson on brain language areas and check out my other lessons on other brain anatomy topics if you haven't already. Please like and subscribe for more lessons like this one. And as always, thanks so much for watching and hope see you next time.