How Our Brains Define Our Sense of Self
Whether we are aware of it or not, we all spend each day traveling through time. Every day, we take a step forward – embarking on a new journey as we experience new things. As this happens, your neurons are acting like something of a dashboard – calibrating to make way for all the new sensations we’ve brought in – our thoughts, memories, hopes and feelings. You might say that we’re constantly in the process of reinventing ourselves – a process we carry out every day with just a mental construct of who we are as a blueprint for putting each piece together. The glue to hold all of what constitutes our identity together is our memory.
Our journey through time goes beyond the physical realm. We also experience and revisit the past as we shuffle through our memories and then use them to imagine and create the future – dreaming of what tomorrow will look like or where we see ourselves in five years. Whenever you do these simple thought experiments, you are imagining yourself and where you are right now, bringing in thoughts of who you once were and think of how you will shape yourself in just a short period of time from now.
A new study, published by the journal Social Cognitive and Affective Neuroscience (SCAN), explores this process a bit further. It considers the way in which a certain region of the brain aids in weaving together episodic memories of both our present and future self. Injury to this region – the ventral medial prefrontal cortex (vmPFC) results in a fractured sense of identity. The vmPFC has recently caught the attention of neuroscientists because it could be the region that produces the fundamental model of our self and places it within a mental context of time. It is therefore likely that this region could be where our “sense of self” arises from.
For nearly as long as their profession has existed, psychologists have noticed that our minds tend to process information about the self in a different way than they do with other details. Try it yourself. It’s probably a lot easier to remember your first day of school or your first break-up than it is to remember where you parked today – let alone yesterday. Memories that reference the self are easier to recall than other forms of memory. That’s because they have the advantage of what researchers like to call the self-reference effect (SRE), in which all information related to the self takes precedent and is featured more prominently in our thoughts. Self-related memories have their own distinction from episodic memory, the category of recollections that hold our own life events and experiences, or semantic memory, which connects to our storage of more general knowledge, where we store details like the color of the trees or the association of snow with winter.
Therefore, SREs, are a means for investigating the way our own sense of self arises from the brain’s inner workings — an area that multiple research groups have pored over heavily. In a prior experiment, for example, researchers used functional magnetic resonance imaging (fMRI) technology, a method that looks at blood flow as a way to measure the brain’s activity, in order to identify the regions of the brain that were stimulated from self-reference. The studies highlighted the medial prefrontal cortex (mPFC) as a particular brain region involved in self-thought – one that showed the highest activity when the brain was at rest and thought to play a role in slow-wave sleep. The mPFC is further split into both upper and lower regions (known respectively as the dorsal and ventral). These both make their own particular contributions to self-related thought. The dorsal section has been found to play a part in distinguishing the self apart from other people, which researchers believe is task related, while the ventral section, the vmPFC, is believed to contribute more significantly to emotional processing.
For this recent SCAN study, the researchers applied the self-reference effect in order to appraise the memories of present and future selves in patients who suffered brain lesions to the vmPFC. The scientists looked at seven different people who had lesions in this area and compared their results to a control group composed of eight individuals who had sustained injuries to other parts of their brain, and another 23 healthy individuals who had not suffered any brain injuries. All the test subjects in the study were vetted with an in-depth neuropsychological evaluation, that confirmed they were within the normal range for a host of cognitive tests, with an emphasis on things like verbal fluency and spatial short-term memory. Afterward, the researchers interviewed the participants – having them make a list of adjectives to describe both themselves and those of a well-known celebrity, both features that existed in the present and would likely be there one decade into the future. After they had made their list, the participants were then asked to recall the same traits they ascribed.
The researchers learned that the people within their control group were able recall many more adjectives that they attributed to themselves in both the present and future than any of the adjectives that were commonly linked to the given celebrity. Put a different way, they learned that this self-reference effect can extend to both the future as well as the present self. Although there was some variation in this group—people suffering various brain injuries had a bit more difficulty recalling attributes of their future self when they were compared with healthy participants, the self-reference effect still held up in each trial.
The results were recognizably different in the test subjects who exhibited lesions in the vmPFC. These patients revealed a limited or total lack of the ability to recall any references to themselves, even without any context of a timeframe. Their ability to identify adjectives to describe celebrities from either the present or the future was also markedly impaired next to the other participants in the study. Those with vmPFC lesions also showed less confidence in an individual’s own ability to have traits that set them apart from the other participants. All of these circumstances are evidence that the vmPFC has a crucial role in both the formation and the maintenance of our own identities.
These new findings are interesting in several different ways. Lesions on the brain, as severe as they may be, help researchers to understand what the affected brain region is responsible for when functioning normally. Lesions affecting the vmPFC tend to be associated with an altered personality, stifled emotions as well as notable changes in both emotional and the executive function. Trauma to this area has been associated with what is known as a confabulation – a false memory that the patient is nonetheless able to recall with a great deal of confidence. In many cases, it could be easy to dismiss confabulations as deliberate falsehoods, but those who engage in them are unaware that their memories are based on things that never actually happened, and it is likely that this confusion could be the result of faulty memory retrieval or monitoring mechanisms.
On a broader scale, the SCAN study further clarifies how our self-related memories essential for the maintenance of our core sense of self in the present rely on a properly functioning vmPFC. What then about our past selves? Interestingly enough, in prior studies that required people to reflect on their past selves, activity in vmPFC activation of the mPFC was no different than when the test subjects were considering aspects of a different person entirely. Our past selves seem foreign to ourselves, as if they were another individual. Neuroscientists suspect that this could be due to our tendency to judge our past selves in a negative light while we use our pasts to create a positive self-image for the present – trying to distance ourselves from our past mistakes and who we used to be.
