Pengmin Qin

How is our self related to midline regions and the default-mode network?

The problem of the self has been of increasing interest in recent neuroscience. Brain imaging studies have raised the question of whether neural activity in cortical midline regions is self-specific and whether self-specific activity is related to resting state activity (RSA). A quantitative meta-analysis that included 87 studies, representing 1433 participants, was conducted to discuss these questions. First, the specificity of the self (e.g. hearing ones own name, seeing ones own face) was tested and compared across familiar (using stimuli from personally known people) and other (non-self-non-familiar, i.e. strangers and widely-known figures) conditions. Second, the relationship between the self and resting state activity, as reflected by the default-mode network (DMN), was tested. The results indicated that the perigenual anterior cingulate cortex (PACC) is specifically involved in self-processing when compared to familiarity, other, and task/stimulus effects. On the contrary, other midline regions, i.e., medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC) were functionally unspecific as they were recruited during the processing of both self-specific and familiar stimuli. Finally, the PACC was recruited during self-specific stimuli and this activity overlapped with DMN activity during resting state, thus distinguishing the self-related processing from both that of the familiar and other conditions. Taken together, our data suggest that our sense of self may result from a specific kind of interaction between resting state activity and stimulus-induced activity, i.e., rest-stimulus interaction, within the midline regions.

Cerebral response to patient's own name in the vegetative and minimally conscious states

Background: A challenge in the management of severely brain-damaged patients with altered states of consciousness is the differential diagnosis between the vegetative state (VS) and the minimally conscious state (MCS), especially for the gray zone separating these clinical entities. Objective: To evaluate the differences in brain activation in response to presentation of the patients own name spoken by a familiar voice (SON-FV) in patients with VS and MCS. Methods: By using fMRI, we prospectively studied residual cerebral activation to SON-FV in seven patients with VS and four with MCS. Behavioral evaluation was performed by means of standardized testing up to 3 months post-fMRI. Results: Two patients with VS failed to show any significant cerebral activation. Three patients with VS showed SON-FV induced activation within the primary auditory cortex. Finally, two patients with VS and all four patients with MCS not only showed activation in primary auditory cortex but also in hierarchically higher order associative temporal areas. These two patients with VS showing the most widespread activation subsequently showed clinical improvement to MCS observed 3 months after their fMRI scan. Conclusion: The cerebral responses to patients own name spoken by a familiar voice as measured by fMRI might be a useful tool to preclinically distinguish minimally conscious state–like cognitive processing in some patients behaviorally classified as vegetative.

Rest-stimulus interaction in the brain: a review

Studies in animals and humans have demonstrated intrinsic activity in the brain during the resting state. The concept of the default-mode network (DMN) - a set of brain regions in which resting-state activity (RSA) activity is reduced in response to external stimuli - recently raised much controversy concerning the psychological correlates of RSA. However, it remains unclear how RSA interacts with stimulus-induced activity. Here we review studies in humans and animals that address how RSA interacts with stimulus-induced activity; we also discuss, conversely, how stimulus-induced activity can modulate RSA. Psychologically, the rest-stimulus interaction is relevant to predicting subsequent behavioral and mental states. We conclude that a better understanding of the rest-stimulus interaction is likely to be crucial to the elucidation of the brains contribution to mental states.

Brain imaging of the self - Conceptual, anatomical and methodological issues

In this paper we consider two major issues: conceptual-experimental approaches to the self, and the neuroanatomical substrate of the self. We distinguish content- and processed-based concepts of the self that entail different experimental strategies, and anatomically, we investigate the concept of midline structures in further detail and present a novel view on the anatomy of an integrated subcortical-cortical midline system. Presenting meta-analytic evidence, we show that the anterior paralimbic, e.g. midline, regions do indeed seem to be specific for self-specific stimuli. We conclude that future investigation of the self need to develop novel concepts that are more empirically plausible than those currently in use. Different concepts of self will require novel experimental designs that include, for example, the brains resting state activity as an independent variable. Modifications of both conceptual and anatomical dimensions will allow an empirically more plausible account of the relationship between brain and self.

Anterior cingulate activity and the self in disorders of consciousness

Objectives: The aim of this study was to investigate the relationship between medial cortical activation and the presence of self and consciousness in healthy subjects and patients with vegetative state and minimally conscious state using functional magnetic resonance imaging (fMRI). Experiment design: We first conducted two fMRI experiments in healthy subjects to identify brain regions specifically associated with self‐perception through the use of different auditory stimuli that had different grades of self‐relatedness. We then applied these regions as functional localizers to examine the relationship between neural activity changes during self‐relatedness and consciousness level in the patients with disorders of consciousness (DOC). Principal observations: We demonstrated recruitment of various anterior medial cortical regions including the anterior cingulate cortex (ACC) in healthy subjects during auditory perception of self‐related stimuli. We further showed that patients with DOC showed signal changes in the ACC during auditory perception of self‐related stimuli. Finally, it was shown that these signal changes correlate with the level of consciousness in the patients with DOC. Conclusion: The degree of consciousness in patients with DOC was correlated with neural activity in the ACC induced by self‐related stimuli. Our results not only shed light on the pathophysiology of DOC, but may also suggest a useful neural, and thus diagnostic, marker of the dysfunction of consciousness in vegetative patients. Hum Brain Mapp, 2010.

Mismatch negativity to the patient's own name in chronic disorders of consciousness

Previous studies implicated potential value of mismatch negativity (MMN) in predicting recovery of consciousness in patients with disorders of consciousness (DOC). We have adopted a novel MMN evoked by subjects own name (SON), a self-referential stimulus thought to be powerful in evoking residual brain activity, and examined the correlation between the MMN and recovery of consciousness in patients with chronic (>1 month) DOC. Twelve patients and 12 age-matched healthy controls were investigated. The patients were diagnosed as coma (n=4), vegetative state (VS, n=6), and minimally conscious state (MCS, n=2), mainly based on the JFK Coma Recovery Scale-Revised. The SON-evoked MMN (SON-MMN) was present in seven patients. Critically, the presence of SON-MMN was significantly correlated with recovery of consciousness. While four of the five patients (three VS and two coma) showing SON-MMN changed to MCS 3 months later, the rest of the patients (three VS and two coma) without SON-MMN failed to show any clinical improvement. Our study thus illustrates that the subjects own name is effective in evoking MMN in patients with DOC, and that SON-MMN has potential prognostic values in predicting recovery of consciousness.

Dissociation between anterior and posterior cortical regions during self-specificity and familiarity: a combined fMRI-meta-analytic study.

The familiarity to the subject of any potential stimuli presents one of the major difficulties for the investigation of the self; the separation of effects resulting from familiarity from self‐effects being extremely problematic. The aim of this study was thus to investigate the neural distinction between self and familiarity by combining two sets of fMRI data with a meta‐analysis. In the first fMRI experiment, regions responding to self/familiarity were investigated using the subjects own name and names of familiar others. These effects were confirmed and extended in a second fMRI experiment using the subjects own name and a strangers name, as spoken by familiar and unfamiliar voices. Finally, a meta‐analysis of self‐ and familiarity‐related studies was conducted. Neural activity in the anterior brain regions, such as the anterior cingulate (ACC) and anterior insula (AI), was found to be specific for self‐specific stimuli. In contrast, posterior brain regions, such as the posterior cingulate, were activated by familiar stimuli. Finally, the distinction between anterior and posterior regions for self and familiarity was confirmed by meta‐analytic data. This study demonstrates a clear anterior–posterior cortical partition between self‐specificity and familiarity. Hum Brain Mapp, 2012.

Is There a Nonadditive Interaction Between Spontaneous and Evoked Activity? Phase-Dependence and Its Relation to the Temporal Structure of Scale-Free Brain Activity

Abstract The aim of our study was to use functional magnetic resonance imaging to investigate how spontaneous activity interacts with evoked activity, as well as how the temporal structure of spontaneous activity, that is, long‐range temporal correlations, relate to this interaction. Using an extremely sparse event‐related design (intertrial intervals: 52‐60 s), a novel blood oxygen level‐dependent signal correction approach (accounting for spontaneous fluctuations using pseudotrials) and phase analysis, we provided direct evidence for a nonadditive interaction between spontaneous and evoked activity. We demonstrated the discrepancy between the present and previous observations on why a linear superposition between spontaneous and evoked activity can be seen by using co‐occurring signals from homologous brain regions. Importantly, we further demonstrated that the nonadditive interaction can be characterized by phase‐dependent effects of spontaneous activity, which is closely related to the degree of long‐range temporal correlations in spontaneous activity as indexed by both power‐law exponent and phase‐amplitude coupling. Our findings not only contribute to the understanding of spontaneous brain activity and its scale‐free properties, but also bear important implications for our understanding of neural activity in general.

How are different neural networks related to consciousness

We aimed to investigate the roles of different resting‐state networks in predicting both the actual level of consciousness and its recovery in brain injury patients.

External awareness and GABA—A multimodal imaging study combining fMRI and [18F]flumazenil-PET

Awareness is an essential feature of the human mind that can be directed internally, that is, toward our self, or externally, that is, toward the environment. The combination of internal and external information is crucial to constitute our sense of self. Although the underlying neuronal networks, the so‐called intrinsic and extrinsic systems, have been well‐defined, the associated biochemical mechanisms still remain unclear. We used a well‐established functional magnetic resonance imaging (fMRI) paradigm for internal (heartbeat counting) and external (tone counting) awareness and combined this technique with [18F]FMZ‐PET imaging in the same healthy subjects. Focusing on cortical midline regions, the results showed that both stimuli types induce negative BOLD responses in the mPFC and the precuneus. Carefully controlling for structured noise in fMRI data, these results were also confirmed in an independent data sample using the same paradigm. Moreover, the degree of the GABAA receptor binding potential within these regions was correlated with the neuronal activity changes associated with external, rather than internal awareness when compared to fixation. These data support evidence that the inhibitory neurotransmitter GABA is an influencing factor in the differential processing of internally and externally guided awareness. This in turn has implications for our understanding of the biochemical mechanisms underlying awareness in general and its potential impact on psychiatric disorders. Hum Brain Mapp 35:173–184, 2014.