Disturbances in the narrative self are implicated across psychiatric disorders, with abnormalities in the neural systems supporting its generation and regulation constituting a transdiagnostic risk factor for mental illness. This review highlights how alterations in these brain systems underlie prevalent clinical features, including diminished, rigid, and sustained negative beliefs within the...
Ketamine is an N-methyl-D-aspartate receptor antagonist that has shown effectiveness as a rapidly acting treatment for depression. Although advances have been made in understanding ketamine's antidepressant pharmacological and molecular mechanisms of action, the large-scale neurocognitive mechanisms driving its therapeutic effects are less clearly understood. To help provide such a framework,...
The self is an elusive concept. We have an intuitive sense as to what it refers to, but it defies simple definition. There is some consensus that the self can be broadly separated into what W. James referred to as the "I" and the "me" – the self that experiences, and the self that extends outwards in space and in time, allowing it to be perceived as an object1. This includes the self as...
Heavy cannabis use is associated with reduced motivation. The basal ganglia, central in the motivation system, have the brain's highest cannabinoid receptor density. The frontal lobe is functionally coupled to the basal ganglia via segregated frontal-subcortical circuits conveying information from internal, self-generated activity. The basal ganglia, however, receive additional influence from...
The brain's default mode network (DMN) has become closely associated with self-referential mental activity, particularly in the resting-state. While the DMN is important for such processes, it has functions other than self-reference, and self-referential processes are supported by regions outside of the DMN. In our study of 88 participants, we examined self-referential and resting-state...
Recreational drugs are generally used to intentionally alter conscious experience. Long-lasting cannabis users frequently seek this effect as a means to relieve negative affect states. As with conventional anxiolytic drugs, however, changes in subjective feelings may be associated with memory impairment. We have tested whether the use of cannabis, as a psychoactive compound, is associated with...
The notion of a “default mode of brain function” has taken on certain relevance in human neuroimaging studies and in relation to a network of lateral parietal and midline cortical regions that show prominent activity fluctuations during passive imaging states, such as rest. In this study, we perform three fMRI experiments that demonstrate consistency and specialization in the default mode...
Abstract: The brain’s ‘default mode network’ (DMN) enables flexible switching between internally and externally focused cognition. Precisely how this modulation occurs is not well understood, although may involve key subcortical mechanisms, including hypothesized influences from the basal forebrain (BF) and mediodorsal thalamus (MD). Here, we used ultra-high field (7T) functional magnetic...