Limits...
On the existence of a generalized non-specific task-dependent network.

Hugdahl K, Raichle ME, Mitra A, Specht K - Front Hum Neurosci (2015)

Bottom Line: We now suggest that this is because the brain utilizes the EMN network as a generalized response to tasks that exceeds a cognitive demand threshold and/or requires the processing of novel information.We further discuss how the EMN is related to the DMN, and how a network for extrinsic activity is related to a network for intrinsic activity.Finally, we discuss whether the EMN and DMN networks interact in a common single brain system, rather than being two separate and independent brain systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Medical Psychology, University of Bergen Bergen, Norway ; Division of Psychiatry, Haukeland University Hospital, Bergen Norway ; Department of Radiology, Haukeland University Hospital, Bergen Norway ; NORMENT Center of Excellence, University of Bergen Bergen, Norway.

ABSTRACT
In this paper we suggest the existence of a generalized task-related cortical network that is up-regulated whenever the task to be performed requires the allocation of generalized non-specific cognitive resources, independent of the specifics of the task to be performed. We have labeled this general purpose network, the extrinsic mode network (EMN) as complementary to the default mode network (DMN), such that the EMN is down-regulated during periods of task-absence, when the DMN is up-regulated, and vice versa. We conceptualize the EMN as a cortical network for extrinsic neuronal activity, similar to the DMN as being a cortical network for intrinsic neuronal activity. The EMN has essentially a fronto-temporo-parietal spatial distribution, including the inferior and middle frontal gyri, inferior parietal lobule, supplementary motor area, inferior temporal gyrus. We hypothesize that this network is always active regardless of the cognitive task being performed. We further suggest that failure of network up- and down-regulation dynamics may provide neuronal underpinnings for cognitive impairments seen in many mental disorders, such as, e.g., schizophrenia. We start by describing a common observation in functional imaging, the close overlap in fronto-parietal activations in healthy individuals to tasks that denote very different cognitive processes. We now suggest that this is because the brain utilizes the EMN network as a generalized response to tasks that exceeds a cognitive demand threshold and/or requires the processing of novel information. We further discuss how the EMN is related to the DMN, and how a network for extrinsic activity is related to a network for intrinsic activity. Finally, we discuss whether the EMN and DMN networks interact in a common single brain system, rather than being two separate and independent brain systems.

No MeSH data available.


Related in: MedlinePlus

Comparison of BOLD-fMRI for the Bergen Stroop task (panel #5 in Figure 1), and the average activation shown for the seven cognitive tasks used by Fedorenko et al. (2013) Figure 2. Reprinted with permission from the Publisher.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4526816&req=5

Figure 6: Comparison of BOLD-fMRI for the Bergen Stroop task (panel #5 in Figure 1), and the average activation shown for the seven cognitive tasks used by Fedorenko et al. (2013) Figure 2. Reprinted with permission from the Publisher.

Mentions: The similarities in Figure 6 are again both striking and remarkable considering the range of cognitive processes included in the studies in the comparison. Fedorenko et al. (2013) made the argument that previous group-analyses which have shown commonalities of activation across tasks may have overestimated their case because of inter-individual variability in brain anatomy, which could result in overlapping activations at the group level despite that individual activations are different. This argument could, however, be discussed since activation data typically are normalized to a standard template before visualization in order to avoid the kind of confounding that Fedorenko et al. (2013) warn against. What they did not comment on, however, is that running the same subjects on different tasks, likewise may overestimate overlapping activations, because these same subjects may be non-representative for the population at large, a potential problem that will increase in strength with decreasing sample sizes. Since Fedorenko et al. (2013) based their critical analyses on only 12 subjects this problem is not trivial. A solution would be to have different subjects run on different tasks, and then look for commonalities in the activation patterns. This was done in the studies shown in Figure 1, with 187 subjects in total. It is therefore interesting to note the close overlap between the activation patterns shown in Figure 1 and the aggregate activation pattern shown by Fedorenko et al. (2013, see Figure 6).


On the existence of a generalized non-specific task-dependent network.

Hugdahl K, Raichle ME, Mitra A, Specht K - Front Hum Neurosci (2015)

Comparison of BOLD-fMRI for the Bergen Stroop task (panel #5 in Figure 1), and the average activation shown for the seven cognitive tasks used by Fedorenko et al. (2013) Figure 2. Reprinted with permission from the Publisher.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526816&req=5

Figure 6: Comparison of BOLD-fMRI for the Bergen Stroop task (panel #5 in Figure 1), and the average activation shown for the seven cognitive tasks used by Fedorenko et al. (2013) Figure 2. Reprinted with permission from the Publisher.
Mentions: The similarities in Figure 6 are again both striking and remarkable considering the range of cognitive processes included in the studies in the comparison. Fedorenko et al. (2013) made the argument that previous group-analyses which have shown commonalities of activation across tasks may have overestimated their case because of inter-individual variability in brain anatomy, which could result in overlapping activations at the group level despite that individual activations are different. This argument could, however, be discussed since activation data typically are normalized to a standard template before visualization in order to avoid the kind of confounding that Fedorenko et al. (2013) warn against. What they did not comment on, however, is that running the same subjects on different tasks, likewise may overestimate overlapping activations, because these same subjects may be non-representative for the population at large, a potential problem that will increase in strength with decreasing sample sizes. Since Fedorenko et al. (2013) based their critical analyses on only 12 subjects this problem is not trivial. A solution would be to have different subjects run on different tasks, and then look for commonalities in the activation patterns. This was done in the studies shown in Figure 1, with 187 subjects in total. It is therefore interesting to note the close overlap between the activation patterns shown in Figure 1 and the aggregate activation pattern shown by Fedorenko et al. (2013, see Figure 6).

Bottom Line: We now suggest that this is because the brain utilizes the EMN network as a generalized response to tasks that exceeds a cognitive demand threshold and/or requires the processing of novel information.We further discuss how the EMN is related to the DMN, and how a network for extrinsic activity is related to a network for intrinsic activity.Finally, we discuss whether the EMN and DMN networks interact in a common single brain system, rather than being two separate and independent brain systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Medical Psychology, University of Bergen Bergen, Norway ; Division of Psychiatry, Haukeland University Hospital, Bergen Norway ; Department of Radiology, Haukeland University Hospital, Bergen Norway ; NORMENT Center of Excellence, University of Bergen Bergen, Norway.

ABSTRACT
In this paper we suggest the existence of a generalized task-related cortical network that is up-regulated whenever the task to be performed requires the allocation of generalized non-specific cognitive resources, independent of the specifics of the task to be performed. We have labeled this general purpose network, the extrinsic mode network (EMN) as complementary to the default mode network (DMN), such that the EMN is down-regulated during periods of task-absence, when the DMN is up-regulated, and vice versa. We conceptualize the EMN as a cortical network for extrinsic neuronal activity, similar to the DMN as being a cortical network for intrinsic neuronal activity. The EMN has essentially a fronto-temporo-parietal spatial distribution, including the inferior and middle frontal gyri, inferior parietal lobule, supplementary motor area, inferior temporal gyrus. We hypothesize that this network is always active regardless of the cognitive task being performed. We further suggest that failure of network up- and down-regulation dynamics may provide neuronal underpinnings for cognitive impairments seen in many mental disorders, such as, e.g., schizophrenia. We start by describing a common observation in functional imaging, the close overlap in fronto-parietal activations in healthy individuals to tasks that denote very different cognitive processes. We now suggest that this is because the brain utilizes the EMN network as a generalized response to tasks that exceeds a cognitive demand threshold and/or requires the processing of novel information. We further discuss how the EMN is related to the DMN, and how a network for extrinsic activity is related to a network for intrinsic activity. Finally, we discuss whether the EMN and DMN networks interact in a common single brain system, rather than being two separate and independent brain systems.

No MeSH data available.


Related in: MedlinePlus