'Self' and the Problem of Consciousness

During adolescence, major changes in brain mechanisms take place and differentiated representations of both the self and of others are developed. Although studies have investigated the neural mechanisms of self- and other-referential processing in adolescents, the development of these mechanisms remain largely unaddressed. Here, we report a three-year longitudinal study with annual measurements, and investigate the developmental trajectories of activity and connectivity underlying self- and other-referential processes in 34 participants from early to mid-adolescence (mean age timepoints 1, 2, 3 = 12.9, 13.9, 15.0 years). Moreover, we probe whether these correlates continue to develop from mid-adolescence to young adulthood by comparing neural correlates of the adolescents at the last measurement to an independent group of 42 young adults (mean age 22 years). Participants underwent functional MRI while performing a trait judgement task in which they indicated whether an adjective described themselves, a similar or a dissimilar peer. Brain activity within the dorsal medial prefrontal cortex (dMPFC) and right temporal parietal junction (TPJ) showed a quadratic change from early to mid-adolescence, with a peak in activity at the second measurement when evaluating the self, the similar and dissimilar peer. No differential activity was observed when comparing the adolescents to young adults. Functional connectivity did not change from early to mid-adolescence, however, connectivity of the dMPFC with a posterior midline region during self- and other-referential processing relative to the control condition reduced from mid-adolescence to young adulthood. Together, these findings provide insight in the developmental trajectories of brain activity and connectivity underlying the development of the self-concept and representations of peers in adolescence.

In this paper I argue that radiological attempts to elucidate the properties of self -- an endeavor currently popular in the social neurosciences -- are fraught with conceptual difficulties. I first discuss several philosophical criteria that increase the chances we are posing the “right” questions to nature. I then discuss whether these criteria are met when empirical efforts are directed at one of the central constructs in the social sciences – the human self. In particular, I consider whether recent attempts to map the neural correlates of self and its assumed properties using brain scanning technology satisfy the conceptual conditions minimally required to ask well-formed, theoretically satisfying questions of nature. I conclude that much theoretical work remains to be done.

Distortions of self-experience are critical symptoms of psychiatric disorders and have detrimental effects on social interactions. In light of the immense need for improved and targeted interventions for social impairments, it is important to better understand the neurochemical substrates of social interaction abilities. We therefore investigated the pharmacological and neural correlates of self- and other-initiated social interaction. In a double-blind, randomized, counterbalanced, crossover study 24 healthy human participants (18 males and 6 females) received either (1) placebo + placebo, (2) placebo + lysergic acid diethylamide (LSD; 100 μg, p.o.), or (3) ketanserin (40 mg, p.o.) + LSD (100 μg, p.o.) on three different occasions. Participants took part in an interactive task using eye-tracking and functional magnetic resonance imaging completing trials of self- and other-initiated joint and non-joint attention. Results demonstrate first, that LSD reduced activity in brain areas important for self-processing, but also social cognition; second, that change in brain activity was linked to subjective experience; and third, that LSD decreased the efficiency of establishing joint attention. Furthermore, LSD-induced effects were blocked by the serotonin 2A receptor (5-HT2AR) antagonist ketanserin, indicating that effects of LSD are attributable to 5-HT2AR stimulation. The current results demonstrate that activity in areas of the "social brain" can be modulated via the 5-HT2AR thereby pointing toward this system as a potential target for the treatment of social impairments associated with psychiatric disorders.SIGNIFICANCE STATEMENT Distortions of self-representation and, potentially related to this, dysfunctional social cognition are central hallmarks of various psychiatric disorders and critically impact disease development, progression, treatment, as well as real-world functioning. However, these deficits are insufficiently targeted by current treatment approaches. The administration of lysergic acid diethylamide (LSD) in combination with functional magnetic resonance imaging and real-time eye-tracking offers the unique opportunity to study alterations in self-experience, their relation to social cognition, and the underlying neuropharmacology. Results demonstrate that LSD alters self-experience as well as basic social cognition processing in areas of the "social brain". Furthermore, these alterations are attributable to 5-HT2A receptor stimulation, thereby pinpointing toward this receptor system in the development of pharmacotherapies for sociocognitive deficits in psychiatric disorders.

During adolescence, self-concept develops profoundly, accompanied by major changes in hormone levels. Self-evaluations become more complex, and peers and their opinions increasingly salient. Neuroimaging studies have investigated self- and other-related processing in adolescents, however, the influence of similarity of peers on these processes is still unclear, as well as functional connectivity underlying such processes. We investigated the effect of peer similarity on neural activity and connectivity underlying self- and other-referential processing, by distinguishing between a similar and dissimilar peer when making other-evaluations. Moreover, we explored the association between testosterone and brain activity during self-evaluations. Sixty-six young adolescents underwent functional MRI while performing a trait judgement task in which they indicated whether an adjective described themselves, a similar or a dissimilar classmate. The ventral medial prefrontal cortex (MPFC) showed increased engagement in self-referential processing, and the posterior cingulate cortex and right temporal parietal junction during other-evaluations. However, activity did not differ between the similar and dissimilar other conditions. Functional connectivity of the ventral MPFC included the striatum when evaluating the similar peer and frontoparietal regions when evaluating the dissimilar peer. Furthermore, inter-individual differences in testosterone levels were positively associated with dorsal MPFC activity in males. This study provides insight into the influence of peer similarity on activity and connectivity underlying other-referential processing in young adolescents, and suggests that testosterone affects neural correlates of self-referential processing.

Humans show enhanced (neural) responses to self-related stimuli, such as their own face or name. These enhanced responses are thought to be crucial for social functioning, and have been found to be diminished in individuals with autism. However, neural responses to self-related stimuli have rarely been investigated across different stimulus types. Further, it is still being debated precisely which aspects of self-related processing are altered in autism. Therefore, across two studies, we investigated the neural processes underlying own and other face and name processing, and how these may differ between adults with and without autism. In Study 1, 35 neurotypical adults in a 3T MRI scanner passively viewed six runs of face images, and six of visually presented first names, across three categories (Self, Close Other, Stranger). As an attention check, participants were asked to press a button when a fixation cross changed color. In Study 2, the paradigm was the same, but was this time tested in 25 adults with autism, and 24 without autism. For both studies, whole-brain analyses as well as searchlight decoding analyses were employed. Whole-brain analyses revealed stronger activation for familiar faces and names than for a stranger’s face/name (but no self-specific enhancement) in several visual areas and in the ACC and precuneus. Searchlight decoding additionally revealed self-specific activation patterns in visual areas for both faces and names, and in the intraparietal sulcus and right STS for faces specifically. This pattern of results was replicated in Study 2. No group differences were found. The patterns of neural activation indicate involvement of modality-specific (i.e., visual) areas, but also areas of the social network, in processing familiar information. Self-specific responses are more subtle and appear stronger for one’s own face than name. Finally, results show no differences in this basic form of self-related information processing in autism.

Cultivating social connection has long been a goal of psychology, philosophy, religion, and public policy. Yet the psychological and neural responses that accompany a feeling of connection to others remain unclear. In the present study, we used functional neuroimaging to shed light on the neural correlates of self- and other-focused processes during the successful self-generation of feelings of social connection. To do this, we used a trait judgment task to localize functional activation related to self-focused thought. We then examined brain responses during guided exercises designed both to encourage feeling love and connection from others (i.e., self-focused) and to generate feelings of love and connection toward others (i.e., other-focused). Our results indicated that generating feelings of social connection recruited a portion of the medial prefrontal cortex (MPFC) implicated in thinking about both the self and others. Within this larger area, we observed distinct profiles of activation within different subregions. Although rostral anterior cingulate cortex was more strongly activated by other-focused components of the task, a more dorsal portion of MPFC was comparatively more active during primarily self-focused components of the task. Somewhat surprisingly, stronger feelings of social connection were not associated with greater activation in the anterior cingulate, but rather with less activation in the dorsal region of the MPFC related to self-focused thought. These results are consistent with the possibility that reducing certain kinds of self-focused thought might yield a greater sense of social connection to and care for others.

While statistical learning is often studied individually, its collective representation through self-other integration remains unclear. This study examines dynamic self-other integration and its multi-brain mechanism using simultaneous recordings from dyads. Participants (N = 112) each repeatedly responded to half of a fixed stimulus sequence with either an active partner (joint context) or a passive observer (baseline context). Significant individual statistical learning was evident in the joint context, characterized by decreased reaction time (RT) and intra-brain neural responses, followed by a quadratic trend (i.e., first increasing and then decreasing) upon insertion of an interference sequence. More importantly, Brain-to-Brain Coupling (BtBC) in the theta band also showed learning and modulation-related trends, with its slope negatively and positively correlating with the slopes of RT and intra-brain functional connectivity, respectively. These results highlight the dynamic nature of self-other integration in joint statistical learning, with statistical regularities implicitly and spontaneously modulating this process. Notably, the BtBC serves as a key neural correlate underlying the dynamics of self-other integration.

Am I seeing myself, my friend or a stranger? The role of personal familiarity in visual distinction of body identities in the human brain

There is an intimate relationship between consciousness and the notion of self. By studying patients with disorders of consciousness, we are offered with a unique lesion approach to tackle the neural correlates of self in the absence of subjective reports. Studies employing neuroimaging techniques point to the critical involvement of midline anterior and posterior cortices in response to the passive presentation of self-referential stimuli, such as the patient’s own name and own face. Also, resting state studies show that these midline regions are severely impaired as a function of the level of consciousness. Theoretical frameworks combining all this progress surpass the functional localization of self-related cognition and suggest a dynamic system-level approach to the phenomenological complexity of subjectivity. Importantly for non-communicating patients suffering from disorders of consciousness, the clinical translation of these technologies will allow medical professionals and families to better comprehend these disorders and plan efficient medical management for these patients.

The self is a critical component of consciousness. The neural correlates of self have proven elusive, but it is reasonable to suggest that, in its simplest form, the self process requires a composite representation of the ongoing state of the organism as reflected in subcortical and cortical somatic maps within the central nervous system. The basis for these maps is a wealth of signals originating in different sectors of the body-proper. Some of these signals portray the actual state of the body as modified by emotions in response to interactions with the environment; but other signals are the result of internal simulations controlled from other regions of the central nervous system.

In everyday life causal attribution is important in order to structure the complex world, provide explanations for events and to understand why our environment interacts with us in a particular way. This study used functional magnetic resonance imaging (fMRI) in 30 healthy subjects to separate the neural correlates of self vs. external responsibility for social events and explore the neural basis of self-serving attributions (internal attributions of positive events and external attributions of negative events). We presented short sentences describing positive and negative social events and asked participants to imagine the event, to decide the main cause and assign it to one of the categories (internal vs. external). FMRI data were analyzed using a 2 × 2 factorial design with the factors emotional valence and attribution. Internal compared to external attribution revealed activations along the right temporoparietal junction (TPJ). The reverse contrast showed a left lateralized network mainly involving the TPJ, the precuneus and the superior/medial frontal gyrus. These results confirmed the involvement of a fronto-temporoparietal network in differentiating self and external responsibility. Analysis of the self-serving bias yielded activation in the dorsal anterior cingulate and in the dorsal striatum, suggesting a rewarding value of these attributions.

Auditory verbal hallucinations (AVH) are a typical feature of schizophrenia, a psychiatric disorder characterised by impaired ties with reality. Two major theories that attempt to explain the neurobiology of hallucinations involve the bottom-up theory (relating to impairment in auditory processing) and the top-down theory (relating to an impairment in internal monitoring). Self-agency, a sense of ownership of one’s actions, is hypothesised to be impaired in schizophrenia in accordance with the “top-down” perspective. Using advanced neuroimaging methods like functional magnetic resonance imaging (fMRI), one can probe the underlying mechanism of self-agency and its possible failure in patients experiencing AVH. This will not only shed light on the neurobiology of schizophrenia and AVH, but also generate insight into the neural correlates of self. In this chapter, we discuss self-agency and its possible failure in patients with schizophrenia experiencing AVH. We review various fMRI studies that have been employed to study AVH and discuss methodological considerations which one needs to keep in mind when devising such experiments. Finally, we introduce a novel fMRI paradigm—hallucination attention modulation task (HAMT) to study the neural correlates of AVH and discuss some preliminary results from our pilot study which link AVH to an underlying disorder of self-agency.

Towards a functional neuroanatomy of self processing: effects of faces and words

Self-disturbances as a possible premorbid indicator of schizophrenia risk: A neurodevelopmental perspective

Self