Posts tagged default network

I came across this study article today by Farb et al, that talks about two distinct neural networks in the brain that are involved in self-reference. To be fair, the networks are somewhat blurred and overlap in naive people, while in people who practice mindfulness meditation, the networks are more distinct and non-overlapping. My interest was piqued as I am a keen follower of default-brain network , which has been implicated in self-referential thinking and this article seems to at one point argue that the narrative self viz ‘me’ is grounded in default brain network, while the experiencer ‘I” has some other nearby related areas as the neural substrates.

But first let us clarify what we mean by ‘me’ and ‘I’. For this I would like to quote form a Gallagher article:

Ever since William James (1890) provided a catalogue of different senses of the self, philosophers and psychologists have been hard at work refining and expanding the possible variations of this concept. Supplementing James’ inventory of physical self, mental self, spiritual self, and the ego, Neisser (1988), for example, suggested important distinctions between ecological, interpersonal, extended, private, and conceptual aspects of self. More recently, reviewing a contentious collection of essays from various disciplines, Strawson (1999) found an overabundance of delineations between cognitive, embodied, fictional, and narrative selves, among others. It would be impossible to review all of these diverse notions of self in this short paper, so I have focused on several recently developed approaches that promise the best exchange between philosophy of mind and the other cognitive sciences. Because these approaches move in divergent theoretical directions they should help to convey the breadth of philosophical analysis on this topic. They can be divided into two groups that are focused, respectively, on two important aspects of self.

A first approach involves various attempts to account for a ‘minimal’ sense of self. If we strip away all of the unessential features of self, the intuition is that there is a basic, immediate, or primitive something that we are still willing to call a self. This approach leaves aside questions about the degree to which the self is extended beyond the short-term or ’specious’ present to include past thoughts and actions. Although identity over time is a major issue in the philosophical definition of personal identity, the concept of the minimal self is limited to that which is accessible to immediate and present self-consciousness. Non-philosophers have found that certain aspects of the minimal self are relevant to current research in robotics. Furthermore, aspects of the minimal self that involve senses of ownership and agency in the context of both motor action and cognition can be clarified by neurocognitive models (developed to explain pathologies such as schizophrenia) that suggest the involvement of specific brain systems (including prefrontal cortex, SMA, and cerebellum).

A second approach involves conceiving of the self in terms of narrative, a concept imported into the cognitive-science context by Dennett (1991) , but one which may have a more complex significance than indicated in Dennett’s account. The narrative self is extended in time to include memories of the past and intentions toward the future. It is what Neisser refers to as the extended self, and what Dennett calls a ‘nonminimal selfy’ self. Neuropsychological accounts of episodic memory or loss of memory can help to circumscribe the neurological underpinnings of the narrative self.

If you haven’t guessed by now, the minimal self is ‘I’: the doer , experiencer experiencing the immediate present; the narrative self is ‘me’ -an entity stretched in time and living as much in past and future as in the present. The study authors delineate the same as follows (note that they too start with William James reference):(* references removed)

Since William James’ early conceptualization, the ‘self ’ has been characterised as a source of permanence beneath the constantly shifting set of experiences that constitute conscious life. This permanence is often related to the construction of narratives that weave together the threads of temporally disparate experiences into a cohesive fabric. To account for this continuity, William James posited an explanatory ‘me’ to make sense of the ‘I’ acting in the present moment . Recently, progress has been made in characterizing the neural bases of the processes supporting William James’ ‘me’ in the form of ‘narrative’ self-reference , highlighting the role of the medial prefrontal cortices (mPFC) in supporting self awareness by linking subjective experiences across time . The mPFC has been shown to support an array of self-related capacities, including memory for self-traits , traits of similar others , reflected self-knowledge , and aspirations for the future . As such, cortical midline processes may be characterised as supporting narrative self-reference that maintains continuity of identity across time .

Narrative self-reference stands in stark contrast to the immediate, agentic ‘I’ supporting the notion of momentary experience as an expression of selfhood. Most examinations of self-reference ignore mechanisms of momentary consciousness, which may represent core aspects of self-experience achieved earlier in development and may have evolved in earlier animal species. Indeed, little is known about whether the neural substrates underlying momentary self-reference are one and the same, or distinct from, cortical midline structures supporting narrative experience. One hypothesis suggests that awareness of momentary self-reference is neurally distinct from narrative self-reference and is derived from neural markers of transient body states, in particular, right lateralised exteroceptive somatic and interoceptive insular cortices. In the present study, we examined this thesis.

In short using fMRI, they tried to find the different hypothesized neural networks underlying the two senses of self and did find evidence for clear segregation in those practicing mindfulness meditation. Their methodology however, is not fool proof and this they themselves note in their conclusions. Here are their findings:

Consistent with a theory of self-reference as mentalising, linguistically mediated and of higher order executive origin , participants engaged midline prefrontal cortices and a left lateralised linguistic-semantic network (inferior lateral PFC, middle temporal and angular gyri) during NF (narrative focus: ‘me’ condition). Demonstrating a default bias towards NF as previously revealed in ‘resting’ mind wandering states , relatively restricted reductions in the cortical midline network were found when attention was explicitly directed towards a moment-to-moment EF (experiential focus: ‘I’ condition) in novice participants with little training in this form of self-reflection. These individuals revealed increased left lateralised prefrontal-parietal activations during EF likely reflecting greater task-related linguistic processing that has been shown to be associated with decreased medial prefrontal recruitment .

So what they found was that a part of default network was engaged in ‘me’ condition; while task-related areas were recruited in “I” condition and appropriate task-related suppression of some part of default network observed. This effect was with naive subjects, but with those trained in mindfulness meditation, they observed a sort of double dissociation:

Following an intensive 8 week course in mindfulness meditation, during which individuals learn to develop the capacity to monitor moment-to-moment experience, EF resulted in a pronounced shift away from midline cortices towards a right lateralised network comprised of the ventral and dorsolateral PFC, as well as right insula, SII and inferior parietal lobule. Consistent with a dual-mode hypothesis of self-awareness, these results suggest a fundamental neural dissociation in modes of self-representation that support distinct, but habitually integrated, aspects of self-reference: (i) higher order self-reference characterised by neural processes supporting awareness of a self that extends across time and (ii) more basic momentary self-reference characterised by neural changes supporting awareness of the psychological present. The latter, represented by evolutionary older neural regions, may represent a return to the neural origins of identity, in which self-awareness in each moment arises from the integration of basic interoceptive and exteroceptive bodily sensory processes. In contrast, the narrative mode of self-reference may represent an overlearned mode of information processing that has become automatic through practice, consistent with established findings on training-induced automaticity.

To me this sounds interesting: If I had to stretch my neck and relate this to autism and schizophrenia , I would say that based on earlier coverage on this blog: Schizophrenics have a higher default brain activity and perhaps try to spin too much of a narrative. Perhaps they are the ones that would best benefit with mindfulness meditation trainings to calm their default ‘me’ and activate the ‘I’ also at relevant times. On the opposite side, one is all too aware of the here-and-now feeling of self that many autistics have- a direct and immediate perceptual relation with world. Perhaps, they too can benefit from some for of mindfulness meditation by learning to use the default brain network too at times – letting teh mind wander and spinning a tale (however fictional) about themselves.

Farb, N., Segal, Z., Mayberg, H., Bean, J., McKeon, D., Fatima, Z., & Anderson, A. (2007). Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference Social Cognitive and Affective Neuroscience, 2 (4), 313-322 DOI: 10.1093/scan/nsm030 Gallagher, S. (2000). Philosophical conceptions of the self: implications for cognitive science Trends in Cognitive Sciences, 4 (1), 14-21 DOI: 10.1016/S1364-6613(99)01417-5

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