When self comes to a wandering mind: Brain representations and dynamics of self-generated concepts in spontaneous thought

Self-relevant concepts are major building blocks of spontaneous thought, and their dynamics in a natural stream of thought are likely to reveal one's internal states important for mental health. Here we conducted an fMRI experiment (n = 62) to examine brain representations and dynamics of self-generated concepts in the context of spontaneous thought using a newly developed free association-based thought sampling task. The dynamics of conceptual associations were predictive of individual differences in general negative affectivity, replicating across multiple datasets (n = 196). Reflecting on self-generated concepts strongly engaged brain regions linked to autobiographical memory, conceptual processes, emotion, and autonomic regulation, including the medial prefrontal and medial temporal subcortical structures. Multivariate pattern-based predictive modeling revealed that the neural representations of valence became more person-specific as the level of perceived self-relevance increased. Overall, this study provides a hint of how self-generated concepts in spontaneous thought construct inner affective states and idiosyncrasies.

Distinct electrophysiological signatures of task-unrelated and dynamic thoughts

Humans spend much of their lives engaging with their internal train of thoughts. Traditionally, research focused on whether or not these thoughts are related to ongoing tasks, and has identified reliable and distinct behavioral and neural correlates of task-unrelated and task-related thought. A recent theoretical framework highlighted a different aspect of thinking—how it dynamically moves between topics. However, the neural correlates of such thought dynamics are unknown. The current study aimed to determine the electrophysiological signatures of these dynamics by recording electroencephalogram (EEG) while participants performed an attention task and periodically answered thought-sampling questions about whether their thoughts were 1) task-unrelated, 2) freely moving, 3) deliberately constrained, and 4) automatically constrained. We examined three EEG measures across different time windows as a function of each thought type: stimulus-evoked P3 event-related potentials and non–stimulus-evoked alpha power and variability. Parietal P3 was larger for task-related relative to task-unrelated thoughts, whereas frontal P3 was increased for deliberately constrained compared with unconstrained thoughts. Frontal electrodes showed enhanced alpha power for freely moving thoughts relative to non-freely moving thoughts. Alpha-power variability was increased for task-unrelated, freely moving, and unconstrained thoughts. Our findings indicate distinct electrophysiological patterns associated with task-unrelated and dynamic thoughts, suggesting these neural measures capture the heterogeneity of our ongoing thoughts.

Hippocampal atrophy and intrinsic brain network dysfunction relate to alterations in mind wandering in neurodegeneration

Mind wandering represents the human capacity for internally focused thought and relies upon the brain’s default network and its interactions with attentional networks. Studies have characterized mind wandering in healthy people, yet there is limited understanding of how this capacity is affected in clinical populations. This paper used a validated thought-sampling task to probe mind wandering capacity in two neurodegenerative disorders: behavioral variant frontotemporal dementia [(bvFTD); n = 35] and Alzheimer’s disease [(AD); n = 24], compared with older controls (n = 37). These patient groups were selected due to canonical structural and functional changes across sites of the default and frontoparietal networks and well-defined impairments in cognitive processes that support mind wandering. Relative to the controls, bvFTD patients displayed significantly reduced mind wandering capacity, offset by a significant increase in stimulus-bound thought. In contrast, AD patients demonstrated comparable levels of mind wandering to controls, in the context of a relatively subtle shift toward stimulus-/task-related forms of thought. In the patient groups, mind wandering was associated with gray matter integrity in the hippocampus/parahippocampus, striatum, insula, and orbitofrontal cortex. Resting-state functional connectivity revealed associations between mind wandering capacity and connectivity within and between regions of the frontoparietal and default networks with distinct patterns evident in patients vs. controls. These findings support a relationship between altered mind wandering capacity in neurodegenerative disorders and structural and functional integrity of the default and frontoparietal networks. This paper highlights a dimension of cognitive dysfunction not well documented in neurodegenerative disorders and validates current models of mind wandering in a clinical population.

The Stream of Consciousness: VII. Further Relevancies from Imagination, Cognition and Personality

Quite naturally, Imagination, Cognition and Personality is the literal context of the present series of articles, which aims to examine what is known and knowledgeably held about the nature and character of the referents of William James's concept of the stream of consciousness. The sixth and seventh installments focus on selected relevant interpretations and facts from Imagination, Cognition and Personality. These relevancies include 1) Lee Tilford Davis and Peder J. Johnson's result of no mental activity at all reported ten per cent of the time by the subjects in an experiment using a thought-sampling technique, 2) Richard A. Block, John L. Saggau, and Leo H. Nickol's finding of similarity between the stream of consciousness and college students' conception of physical time, and 3) L. Stafford Betty's analysis of certain basic durational components of the stream of consciousness (which he calls “non-symbolic”) that are frequently reported as characteristic of mystical experience.

The Stream of Consciousness: VI. Relevancies from Imagination, Cognition and Personality

Quite naturally, Imagination, Cognition and Personality is the literal context of the present series of articles, which aims to examine what is known and knowledgeably held about the nature and character of the referents of William James's concept of the stream of consciousness. The sixth and seventh installments focus on selected relevant interpretations and facts from Imagination, Cognition and Personality. These relevancies include 1) Christopher M. Aranosian's account of those temporal sections of the stream of consciousness during composing and improvising that consist of auditory musical imagery, 2) Erwin R. Steinberg's argument against the stream-of-consciousness technique of writing literature, as providing a poor simulation of a stream of consciousness, especially when compared to what might be accomplished by programming a present-day computer, and 3) Lee Tilford Davis and Peder J. Johnson's result of no mental activity at all reported ten per cent of the time by the subjects in an experiment using random thought-sampling.