Specialization in the default mode: Task‐induced brain deactivations dissociate between visual working memory and attention

Abstract

The idea of an organized mode of brain function that is present as default state and suspended during goal-directed behaviors has recently gained much interest in the study of human brain function. The default mode hypothesis is based on the repeated observation that certain brain areas show task-induced deactivations across a wide range of cognitive tasks. In this event-related functional resonance imaging study we tested the default mode hypothesis by comparing common and selective patterns of BOLD deactivation in response to the demands on visual attention and working memory (WM) that were independently modulated within one task. The results revealed task-induced deactivations within regions of the default mode network (DMN) with a segregation of areas that were additively deactivated by an increase in the demands on both attention and WM, and areas that were selectively deactivated by either high attentional demand or WM load. Attention-selective deactivations appeared in the left ventrolateral and medial prefrontal cortex and the left lateral temporal cortex. Conversely, WM-selective deactivations were found predominantly in the right hemisphere including the medial-parietal, the lateral temporo-parietal, and the medial prefrontal cortex. Moreover, during WM encoding deactivated regions showed task-specific functional connectivity. These findings demonstrate that task-induced deactivations within parts of the DMN depend on the specific characteristics of the attention and WM components of the task. The DMN can thus be subdivided into a set of brain regions that deactivate indiscriminately in response to cognitive demand ("the core DMN") and a part whose deactivation depends on the specific task.

Upregulation of emotion areas through neurofeedback with a focus on positive mood

“…Within the limitation of reverse influence (Poldrack, 2006), we might speculate that the whole-brain activation observed reflects memory (MTL), attention (dorsal ACC) and focus on bodily sensations (insula). The deactivation of the TPJ (equivalent to a higher activation during the rest epochs) is compatible with the role of this area in the "default mode network" and its deactivation during attention-demanding processes (Mayer et al, 2010).…”

Metabolic and structural connectivity within the default mode network relates to working memory performance in young healthy adults

“…Indeed, spontaneous activity within the DMN persists across both experimental and rest conditions (Greicius and Menon, 2004). While DMN activity is clearly suppressed during a WM task, there is a substantial amount of spontaneous signal fluctuations within the DMN (Fransson, 2006;Mayer et al, 2010), indicating that the network is still active in the "deactivation mode".…”

Establishing task- and modality-dependent dissociations between the semantic and default mode networks

“…Indeed, across studies, no region has been consistently reported in both networks. In addition to the various factors noted above, the lack of clarity might relate to a failure of existing studies to take into account task-dependent variations, because the networks' neural responses are likely to vary based on factors such as stimulus type, modality, or task difficulty (19,(29)(30)(31))-which might be clarified by directly comparing DMN and SN across multiple tasks and modalities. One final limitation of the existing work is the tendency to focus solely on areas of DMN-SN overlap and to ignore any large divergences between the networks.…”