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Identifying the neuronal basis of self-concept in the human medial prefrontal and medial temporal brain regions

Periodic Reporting for period 1 - SELFIEv2.0 (Identifying the neuronal basis of self-concept in the human medial prefrontal and medial temporal brain regions)

Reporting period: 2018-03-01 to 2020-02-29

Self-concept is our mental representation of who we are (identity) and what we are like as a person (personality). This representation plays a central role in our life – it allows us to synthesize past personal experiences, predict future situations, and generate complex behaviors. However, the neuronal and computational mechanisms of how we represent ourselves remain largely unknown.

Apart from its general relevance to all of us as thinking individuals, self-concept is important from a clinical perspective. For example, depression is characterized by increased self-focus and negative self-evaluations, whereas people with autism have problems inferring about their own as well as other people’s mental states. Other maladies of the self-concept include depersonalization, dissociative identity, and borderline personality. Current treatments of these disorders are not always effective, which poses serious personal and socioeconomic challenges. Formulating a neuroscientific model of self-concept is a necessary step toward designing new, brain-stimulation-based therapies of self-representation disorders.

The aim of this EU project funded by the Marie Skłodowska-Curie Action is to use the state-of-the-art method of intracranial electrophysiology to identify and characterize single neurons in the human brain that represent conceptual information about the self. We record electrical brain activity from awake human subjects, who have been implanted with depth electrodes for the treatment of pharmacoresistant epilepsy. Our cognitive experiments are conducted during the clinical monitoring period, with no added risk to the patients. The current project is a collaboration between the Karolinska Institute (KI) and the University of California, Los Angeles (UCLA).

The main three objectives of SELFIEv2.0 are:

• to characterize individual neurons in the human brain that respond selectively and invariably during the processing of self-related information;

• to reveal neuronal mechanisms involved in memory encoding of self-related information; and

• to identify functional interactions between the medial prefrontal cortex (MPFC) and the medial temporal lobe (MTL) brain regions during the processing of self-related information.
During the reporting period, the fellow has:

• obtained all necessary ethical approvals and prepared experimental procedures for all experiments proposed in this project.

• gained theoretical and practical expertise in human single-neuron recordings, by attending various safety courses, practical training, and seminars at UCLA. He has also participated in the Human Single Neuron workshop at Caltech, USA.

• collected data from a total of 21 patients (30 recording sessions), created a “pipeline” for data analysis, and processed all sessions recorded so far.

• presented preliminary results during lab meetings at UCLA, prepared a project website, and attended two scientific conferences – the Society for Neuroscience Meeting in San Diego, where he presented a poster, and the Open Self conference in Berlin, where he gave a talk.

• established a new network of collaborators at UCLA, including neurosurgeons, neuroscientists, engineers, and computer scientists.

Our preliminary results indicate that:

• There are individual neurons in the MTL and MPFC brain areas that respond similarly strongly when the patient is seeing a picture of himself/herself and his/her name in a written form. Importantly, these neurons remain silent when the patient is looking at pictures of his/her family members, friends, various celebrities, animals, landscapes, etc. We call such neurons “self-concept cells” because the information they encode is self-specific and abstract (i.e. stimulus-independent).

• In the above-mentioned brain regions, we also find neurons that respond as vigorously to pictures of the patient as to pictures of his/her family or friends, which indicates that the neuronal representation of the self and close-others is partly overlapping.

• We identified yet another group of neurons that respond preferentially to only some pictures of the patient or only to his/her name, as well as to some other stimuli that do not have a clear association with the self. Such neurons are located mainly in the lower-level brain regions, such as the visual areas. This finding suggests that the neuronal representation of the self has different levels that vary in terms of the degrees of selectivity and abstraction of the information being stored.
We are in the process of decoding the multidimensional structure of self-concept (i.e. multiple beliefs about own personality) directly from the activity of single-neurons and local field potentials. To this end, we are using principles from spatial neuroscience, Bayesian decoders, and artificial neural networks. We have also designed an experimental framework to investigate how the two main aspects of the human self – the representation of the body and the self-concept – are functionally linked.

Until the end of the project, we expect to demonstrate that memory encoding of self-relevant information engages distinct neuronal mechanisms than the encoding of information about other people. We will investigate this question both at the level of local neuronal populations, as well as at the level of global connectivity patterns between the MPFC and MTL.

Taken together, we expect that the current project will provide unprecedented insights into the neuronal basis of the human self that are relevant to a broad range of disciplines, including neuroscience, psychology, artificial intelligence, neurology, psychiatry, as well as to the general public.