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Unlocking the BrainVolume 2: Consciousness$

Georg Northoff

Print publication date: 2013

Print ISBN-13: 9780199826995

Published to Oxford Scholarship Online: April 2014

DOI: 10.1093/acprof:oso/9780199826995.001.0001

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(p.579) Appendix 4: Brain and Self

(p.579) Appendix 4: Brain and Self

Source:
Unlocking the Brain
Publisher:
Oxford University Press

What is the self? So far, I have considered empirical results while neglecting more or less the concept of self. In this appendix, I want to give a brief account of the here presupposed concept of self. I contrast “content- and region/network-based concepts of self” with a more “process- and code-based concept of the self.” This leads me finally to argue that what is often called “self-relatedness” within the phenomenal context corresponds well to what can be described as “brain-relatedness” within the neuronal context.

Neurotheoretical Remark IA: Definition of the Self by Sensorimotor and Bodily Contents

The current neuroscientific and philosophical discussion about the concept of self is rather complex and cannot be recounted in full detail. I therefore focus only on some crucial concepts of the self that are relevant in the present context while leaving conceptual subtleties for subsequent philosophical discussion.

The question of the self has been one of the most salient problems throughout the history of philosophy and more recently also in psychology and neuroscience (H. L. Gallagher & Frith, 2003; I. I. Gallagher, 2000; Metzinger & Gallese, 2003; Northoff, 2004). For example, William James distinguished between a physical self, a mental self, and a spiritual self. These distinct selves are now related to distinct brain regions (Churchland, 2002; Dalgleish, 2004; Damasio, 1999a and b, 2003a, 2003b; H. L. Gallagher & Frith, 2003; I. I. Gallagher, 2000; Keenan, Wheeler, Platek, Lardi, & Lassonde, 2003; Kelley et al., 2002; Kircher & David, 2003; Lambie & Marcel, 2002; LeDoux, 2002; Marcel & Lambie, 2004; Northoff & Bermpohl, 2004b; J. Panksepp, 1998a, 2003a and b; Stuss, Gallup, & Alexander, 2001; Turk et al., 2002; Turk, Heatherton, Macrae, Kelley, & Gazzaniga, 2003; Vogeley & Fink, 2003). Damasio (1999) and Panksepp (1998b, 2003) suggest a “protoself” that corresponds more or less to James’s physical self. The protoself is supposed to outline one’s body in affective and sensory-motor terms and is associated with subcortical regions like the periaqueductal gray, the colliculi, and the tectum (J. Panksepp, 2007a and b). Such bodily self-related sensorimotor contents strongly resemble William James’s description of the physical self.

A variant of such sensorimotor-based self has recently been suggested by Legrand and Ruby (2009) (see Cristoff et al. 2011). Based on the phenomenological distinction between reflexive (e.g., cognitive) and prereflexive (e.g., precognitive self-awareness), they associate the latter with sensorimotor rather than cognitive contents. This emphasis on sensorimotor functions as the basis of the self goes well with their assumption of embodiment as being crucial for reflexive and thus cognitive functions (see Thompson 2007; Legrand 2007a and b). Following such a sensorimotor-based concept of self, they (p.580) propose the neural structures underlying sensorimotor functions, including sensorimotor feedback loops, to be crucially involved in generating a sense of self (e.g., prereflexive self-awareness). However, this hypothesis remains to be tested experimentally.

Neurotheoretical Remark IB: Definition of the Self by Mental Contents

Besides sensorimotor and bodily contents, mental contents are also regarded as specific for the self. What recently has been described as “minimal self”(H. L. Gallagher & Frith, 2003; I. I. Gallagher, 2000) or “core or mental self” with mental contents (Damasio, 1999a and b, 2010) might correspond more or less to James’s concept of mental self. The core or mental self builds upon the protoself in mental terms and is associated with regions like the thalamus and the ventromedial prefrontal cortex (see, for instance, Damasio, 1999a and b, 2003a). Instead of the sensorimotor and bodily contents that signify the protoself, the mental self is defined by mental content (e.g., the contents of our mental states) and their associated cognitive contents. For instance, one’s own name may be considered such mental content that is specifically related to the self as mental self (see Chapters 23 and 24 for details).

Already this makes it clear that the mental self neither concerns parts of one’s own body nor their underlying neural mechanisms. Instead, the mental self may concern stimuli from the outside of one’s own body and person; the central feature is here thus not ownership as in the case of the body but rather the designation of certain stimuli either being self- or non-self-specific. Since the judgement of stimuli as either self- or non-self-specific is the guiding experimental paradigm in most current imaging studies, they seem to presuppose at least in part the concept of the mental self (see Chapters 23 and 24 as well as below for details).

Neurotheoretical Remark IC: Definition of the Self by Autobiographical Contents

Finally, a more extended concept of the self may be distinguished. This concept of self is no longer based on either sensorimotor or mental contents as the “proto- and the mental self” but rather on autobiographical contents. Autobiographical contents concern those events and objects in the environment that were experienced as autobiographical in the history of that particular person.

The inclusion of autobiographical memories brings in the concept of time, more specifically the experience of time with its extension into past, present, and future. The concept of the autobiographical self strongly overlaps with the concept of personal identity that raises the question for temporal continuity. This is reflected in, for instance, Damasio’s (1999a and b) concept of “autobiographical self” and Gallagher’s (H. L. Gallagher & Frith, 2003; I. I. Gallagher, 2000) concept of “narrative self” that both strongly rely on linking past, present, and future events, thereby resembling James’s concept of a spiritual self.

The “autobiographical or extended self” that allows one to reflect upon one’s protoself and core or mental self is associated with cortical regions like the hippocampus and the cingulate cortex. Since the autobiographical dimension strongly impacts the ability to judge specific stimuli as either self- or non-self-specific, the current paradigms in brain imaging do also seem to presuppose the “autobiographical self.” The concept of self presupposed in imaging studies thus seems to amount to a mixture of mental and autobiographical self (see Chapters 23 and 24).

Taken together, the self is often defined on the basis of different contents. The protoself presupposes bodily contents, the ones of one’s own body. The mental self is determined by specific mental contents, one’s own mental states as distinguished from the ones of other persons. Finally, the autobiographical self presupposes autobiographical contents and distinguishes them from heterobiographical contents. What does such content-based determination of the self imply in neuronal regard? Despite the recent multiplication of contents, the concept of self remains essentially determined by contents. These different contents provide the very basis for current neuroscience to “neuronalize” the self, and its aim to associate the different contents with different functions and regions/networks. The content-based approach to the self thus goes (p.581) here hand in hand with what may be described as “region- or network-based approach.”

Neurotheoretical Remark IIA: Self-Awareness in Imaging Studies of the Self

What remains unclear, however, is what unites the different content-based concepts of self, allowing us to speak of a self in all cases. One common denominator is that the stimuli are characterized often as self-referential, entailing self-referential processing that is considered common to the distinct concepts of self and its different contents. This has also been described as “self-related” or “self-relevant” processing. Let me go back briefly to the experimental paradigms used in the neuroscience of the self because they tell us a lot about the often rather implicit presupposition about the concept of the self.

Many of the subjects for these studies were presented with stimuli, that is, pictures, faces, words, or tones, and had to evaluate whether they were related to them. Faces, for instance, were presented from one’s own person, relatives, family members, and other nonrelated famous and nonfamous persons. Subjects then had to decide upon the degree of the stimuli’s closeness to one’s own person and decide whether they have something to do with the subjects.

Another example is the way we perceive pictures of ourselves or close friends versus pictures of completely unknown people or pictures of our childhood houses versus pictures of unknown houses. Such comparisons are possible in different sensory modalities. Self-relatedness is here understood and presupposed in a rather cognitive sense. This implies self-awareness, meaning that one becomes aware of one’s self once one sees the stimulus that is related to one’s own self as distinguished from the stimuli that are not related to the self.

Neurotheoretical Remark IIB: Self-Referential Processing as Cognitive Process

The experimental designs in current imaging studies focus most often on the judgement of specific contents, whether they are sensorimotor/bodily, mental, or autobiographical. Such judgement task implicates self-awareness or self-consciousness, the ability to become aware of that stimulus as high- or low self-specific. Imaging studies thus combine a content-based view of the self, e.g., bodily, mental, or autobiographical contents, with the recruitment of higher order cognitive functions required for self-awareness and reflection.

Legrand and Ruby (2009) criticized the latter, the requirement of a “general evaluation function” as they call it. They argue that the imaging results may be confounded by such general unspecific evaluation function and thus by the judgement task required in these imaging studies. At the same time they pertain to a content-based view of the self when characterizing it by sensorimotor rather than cognitive contents.

The strong focus on the judgement in the imaging studies entails that most of the aforementioned imaging studies implicitly presuppose a concept of self as self-consciousness or self-awareness. This is so because the various tasks applied in these studies require subjects to make explicit reference to some aspects of themselves and to consciously access and monitor representational content about one’s self. Since subjects must reference to themselves relying on their self-consciousness or self-awareness in order to fulfil the task, one may speak of “self-referential processing” (see also Northoff 2007). Due to the fact that it requires self-consciousness or self-awareness, self-referential processing is supposed to involve higher order cognitive function, the “highest” and most advanced forms of cognitive processing, out of which the self emerges at the pinnacle of the psychological and neural hierarchy.

On the philosophical level, such a higher order view of self-referential processing may propose correspond to predominantly cognitive accounts of the self in, for instance, higher-order representational accounts suggested by current philosophers like Peter Carruthers and David Rosenthal, as well as some interpretations of Kant’s concept of the self by mental unity and apperception (see for instance, Kitcher 1992, (p.582) 2010; and Brooks 1994; see, though, Northoff 2011, 2012, and 2013, as well as Appendix 3 in this volume for a different reading of Kant).

Neurotheoretical Remark IIC: Process-Based Concept of Self-Specificity

What are the conceptual alternatives in the case of the definition of the self? We have to seek alternatives on both sides experimental and conceptual. Experimentally, we may need to replace the judgement by a less cognitive task, such as mere perception (without any judgement) of self-specific and non-self-specific stimuli. This strategy has been pursued by studies from our group (Qin et al. 2010; Schneider et al. 2008; Northoff et al. 2010, Qin and Northoff 2011). Subjects were instructed to either perceive emotional pictures (see Schneider et al. 2008; Northoff et al. 2009) or their own name (Qin et al. 2010) while not making any judgement.

This kind of experimental design no longer presupposes a judgement or general evaluation function. Interestingly, in these studies focusing on the perception rather than the judgement of self-specific stimuli, various cortical midline structures as well as subcortical midline regions were found to be active during the self-specific stimuli (see Chapters 23 and 24, as well as Northoff et al. 2009; Schneider et al. 2008; and Qin et al. 2010, 2011, for details). This indicates that the neural activity in these regions may not be related to the general evaluation function or judgement itself as suggested by Legrand and Ruby (2009). That was confirmed in a recent meta-analysis of ours where we again showed that the activity in the anterior midline regions is really to the degree of self-specificity of the stimuli rather than task-related effects (see Qin and Northoff 2011; see chapters 23 and 24 herein for details).

Another issue arising here is whether neural activity in the midline structures is necessary for phenomenal consciousness. Alternatively, neural activity in the cortical midline structure (CMS) may also remain independent of the consciousness of the self (e.g., self-consciousness). Qin et al. (2010) demonstrated neural activity in various cortical midline regions during perception of the subject’s own name in vegetative patients who by definition are nonconscious (though this has been debated recently; see Chapters 28 and 29 for more details, as well as Huang et al. 2013, for confirmation and extension of such finding). These results indicate first that the self may be processed independent of consciousness, and second that the neural activity in the CMS may not be related to consciousness independently of whether such consciousness concerns one’s own self or some other content.

Let us briefly rewind. Imaging results demonstrated that the neural activity in the CMS is not specific for self-specific stimuli (see also Chapters 23 and 24). Hence, distinction between self- and non-self-specific contents could not be mapped onto a corresponding anatomical distinction in the cortex. At the same time, however, neural activity in the CMS may not be associated with judgement/general evaluation function or consciousness either. This means that the neural activity in the CMS cannot be accounted for by a specific function, whether it is judgement/general evaluation or consciousness.

What though is the neural activity in the CMS specific for if neither for self-specific contents nor for a general evaluation function or consciousness? Rather than being specific for a specific content (bodily, mental, autobiographical) or a specific function (judgement/general evaluation, consciousness), neural activity in the CMS may be proposed to be specific for a specific process. Conceptually, this entails a shift from a content-based concept of self to a process-based view of the self. Neural activity in the CMS may then be determined by a specific process that is instantiated when being confronted with any kind of stimuli that by the nature of that very process are then determined as self-specific or not (see Fig. A4-1) (see also Chapters 22–24 for details).

Neurotheoretical Remark IIIA: Self-Related Processing as Non-Cognitive Sibling of the More Cognitive Self-Referential Processing

What could this specific process be? Let us briefly recall what exactly one needs to perceive (p.583)

Appendix 4: Brain and Self

Figure A4-1 Content- versus process-based concept of the self. The figure shows idealized versions of different concepts of self as they are discussed and presupposed (often implicitly) in current neuroscience. (Left) This concerns the process-based self that is supposed to be based on various processes like rest–stimulus, stimulus–rest, and rest–rest interaction going on in the brain in its interaction with the environment. I propose that such interactions imply a specific way of neural coding of changes in neural activity. Rather than coding each stimulus by itself at its discrete point in time and space, the brain seems to code spatial and temporal differences between stimuli, resulting in difference-based coding as distinguished from stimulus-based coding. (Right) Here the alternative model of the self is shown that is more based on contents (taking them as a given) and associates them with different functions and regions in the brain. This presupposes ultimately stimulus-based coding rather than difference-based coding. DLPFC, dorsolateral prefrontal cortex.

or judge specific contents as either self- or non-self-specific. Before perceiving and judging them, these contents must be somehow related to the organism. If there is no relation at all of the contents to one’s own organism, one is not able to subsequently perceive or judge them as such and hence as contents that are either self- or non-self-specific. This means that any stimuli, be they bodily, mental, or autobiographical, must first be related to the organism in order for the latter to be able to access the former as a specific content, be it self- or non-self-specific in subsequent perception or judgement. The constitution of any kind of content may thus be traced back to a specific relation between stimulus and organism, which by itself must be mediated by a specific process in order to yield content, whether it is bodily, mental, or autobiographical.

This process that establishes a relation between organism and stimulus may be called self-related processing. Self-related processing describes the relation between stimulus and organism that enables the constitution of any kind of content, be it bodily, mental, or autobiographical, including its associated continuum of different degrees of self-specificity. This distinguishes self-related processing from its cognitive counterpart, self-referential processing, which takes the contents, be they bodily, mental, or autobiographical, as given (and preexisting) and refers them to the self of the organism.

One may now want to argue that if self-related processing does not refer to specific contents, it refers to nothing, thus remaining empty. If, however, self-related processing does not refer to some specific content, we remain unable to (p.584) investigate and reveal any corresponding neural contents. One may consequently criticize the concept of self-related processing as a mere conceptual figment that (refers to nothing and) does therefore not translate into any empirical and better neuronal relevance.

Neurotheoretical Remark IIIB: Difference-Based Coding Mediates Self-Related Processing

To counter this argument of the empirical and neuronal irrelevance of self-related processing, we need to address the issue of the possible neural realization of self-related processing. The neural mechanisms underlying the specific contents themselves, bodily, mental, or autobiographical, may not be viable candidates because they presuppose exactly that, e.g., the contents, which is supposed to be constituted by self-related processing.

How are the contents we perceive and judge as bodily, mental, or autobiographical constituted on the basis of our brain’s neural processes? One may propose a specific form of neural coding by means of which the brain enables the various stimuli to be related to the organism and are thereby transformed into contents. Rather than presupposing the contents as a given and ready-made, that is, objects, events, and persons we perceive, we here focus on those neuronal mechanisms that are necessary and predispose the transformation of any stimuli into objects, events, persons; that is, contents.

The focus on those processes that transform stimuli into contents raises the question for the neural coding of the stimuli in the neural activity of the brain. Therefore, I focused in Volume I on the brain’s neural code, which I supposed to be difference-based coding (rather than stimulus-based coding). This was complemented here in Volume II by showing how such neural code, difference-based coding, can account for the association of the contents and their respective stimulus-induced activity with phenomenal consciousness. Therefore, I hypothesized that difference-based coding is a necessary neuronal condition or predisposition for the possible constitution of contents out of stimuli in general; this must be distinguished from the actual realization of specific contents and their underlying neural correlates (see Chapters 18 and 19). Most important, I propose such difference-based coding to go along with the characterization of the stimuli along a continuum of different degrees of self-specificity (see Chapters 23 and 24).

Self-related processing is thus supposed to be based on a particular way of neural coding, difference-based coding. This makes it impossible to associate it with a content- and region/network-based approach to the self. Instead, it is may be better compatible with what may be described as “process- and code-based approach” to the self. However, we have to be careful. The association of self-related processing with difference-based coding may strongly impact the definition of the former; this will be the focus of the next section here.

Neurotheoretical Remark IIIC: Phenomenal Determination of Self-Relatedness

I here defined “self-related processing” in a purely operational sense, by the relationship between stimulus and organism. Such an operational definition must be distinguished from a more phenomenal definition of self-related processing, which I want to briefly describe as follows.

Presupposing a phenomenal context, self- related processing concerns stimuli that are experienced as strongly related to one’s own person. Without going deeply into abstract philosophical considerations, I would like to give a brief theoretical description of what we mean by the terms “experience,” “strongly related,” and “to one’s person.” The concept of “experience” refers to phenomenal experience, such as, for example, the feeling of love, the smell of a rose, or the feeling of disgust. Thus, we focus on the subjective aspect of experience that is described as the “phenomenal aspect.” The subjective aspect of experience as prereflective is often distinguished from its reflective or cognitive aspects.

Our definition of self-related processing by experience implies a focus on the implicit, subjective, and phenomenal aspects (to feel (p.585) or experience self-referential stimuli)—what Kircher and David (2003) describe as “self-qualia” and Zahavi (2005) and others (Legrand 2007a and b; Legrand and Ruby 2009; see also Dainton 2008 for a phenomenal variant and Strawson 2011 for a metaphysical variant) as “prereflective,.” In contrast, our focus is less on associated cognitive and reflective functions, allowing to make it explicit (to know about or to be aware of stimuli as self-related). As such, I distinguish self-related processing also from what is commonly called “insight,” which presupposes cognitive and reflective functions rather than being simply purely subjective and phenomenal.

Neurotheoretical Remark IIID: Operational Determination of Self-Relatedness

The term “strongly related” points out the process of associating and linking interoceptive and exteroceptive stimuli with a particular person. The main feature here is not the distinction between diverse sensory modalities but rather the linkage of the different stimuli to the individual person, that is, to its self. What unifies and categorizes stimuli in this regard is no longer their sensory origin but the strength of their relation to the self (this is what Kircher and David, 2003, call “ipseity”; see Chapter 30 for details about ipseity).

The more the respective stimulus is associated with the person’s sense of belongingness, the more strongly it can be related to the self, and the stronger the degree of ipseity. The self-stimulus relationship results in the subjective experience of what has been called “mineness”; Lambie and Marcel (2002) speak of an “addition of the ‘for me’” by means of which that particular stimulus becomes “mine,” resulting in “mineness.”

This definition of self-related processing is clearly phenomenal since it involves the explicit reference to experience, that is, consciousness when describing it by phenomenal features like ipseity and mineness. Finally, the phenomenal account of self-related processing presupposes some kind of self or specific person as a given since otherwise self-relatedness, including the phenomenal consciousness and experience of that self-relatedness, would remain impossible.

Such a phenomenal approach is clearly different from my definition of self-relatedness. Though presupposing the same term, self- relatedness, the contexts are different in both cases, that is, phenomenal and nonphenomenal/operational, which leads to the difference in definition. Most important, my starting point is the relation between organism and stimulus, while in the phenomenal definition the starting point is the self itself and its experience independently of whether this “self” refers to a subjective self or objective self as, for instance, Legrand proposes (Legrand 2007a and b, 589).

The phenomenal approach takes the existence of a self as given, ready-made and granted; such a self is presupposed and serves then as starting point to explain how we can experience it, thus becoming phenomenally conscious of it. This is different from my starting point. My starting point is how what the phenomenal approach is taken as a given, ready-made and granted; that is, the self, is constituted on the basis of our brain and its neural coding and resting-state activity. My approach is thus code- and neuronally-based rather than phenomenally-based. As such, my approach must also be distinguished from Metzinger (2003), who takes a more functionalistic-representational approach and declares the self ultimately is an illusion.

Coda: “Self-Relatedness” Versus “Brain Relatedness”

Why do I presuppose such an operational approach to the definition of self-related processing? This looks especially bizarre given my emphasis on prephenomenal features like self-specific organization. I do this in order to not confound the neuronal mechanisms by any phenomenal mechanisms or phenomenal projection. Hence, my first move is purely neuronal in order to avoid any confusion; my motivation is therefore primarily a methodological one. I want to avoid by all means that we project our own phenomenal features onto the brain and its neuronal features.

This is why I refrain from any (metaphysical or otherwise) concept of self for mainly (p.586) methodological reasons. That does not prevent me, however, from using more operational terms in that context like “self-specific organization” as prephenomenal structure to characterize the resting state. And to use the concept of “self-specificity” to characterize larger activity changes as often observed during stimulus-induced activity (see Chapters 23 and 24).

One may nevertheless be confused about the term “self-related processing.” If I do not presuppose any self, why then does the term self still appear in the concept of self-related processing? And why do I need the term “self” at all, for example, methodologically, if I aim to describe neuronal processes like stimulus–rest interaction, rest–rest, and rest–stimulus interaction. Stimulus–rest interaction is supposed to constitute the environment–brain unity (see Chapters 20 and 21), which is a neural predisposition for the constitution of self-specific organization during rest–rest interaction (see Chapter 23). That, in turn, is a neural predisposition for the possible assignment of a high degree of self-specificity to stimuli (or larger neural activity changes in the resting state; see Chapter 24 and Fig. A4-2).

Why then do I still use the term “self” at all? Wouldn’t it be better to replace it by the term “brain”? The terms “self-related processing” and “self-relatedness” would then be replaced by “brain-related processing” and “brain-relatedness” (see also Northoff 2011). Due to its active nature, as manifest in its neural code and its intrinsic activity, the brain can then relate the stimuli to itself along a continuum of different degrees; this may be called “brain-relatedness” and “brain-related processing.” This is, for instance, well manifest when the resting state’s low-frequency fluctuations and their phase onsets align themselves and thus relate to the stimuli in the environment (see Chapter 20).

Appendix 4: Brain and Self

Figure A4-2 Self-relatedness and brain-relatedness. The figure shows the different kinds of processes that are proposed to be relevant in constituting a sense of self. Stimulus–rest, rest–rest, and rest–stimulus interaction and their associated prephenomenal features, environment–brain unity, and self-specific organization. If the interplay is right, they can all lead to the sense of self, the experience of a subject in phenomenal consciousness when associated with a stimulus that shows a high degree of self-specificity (see Chapters 23 and 24 for details).

(p.587)

Do we really still need the concept of self? Methodologically, probably not. While phenomenally the very concept, that is, brain relatedness, that replaces self-relatedness, makes possible the experience of a self, a sense of self in phenomenal consciousness. Such an experience of self is proposed to occur during specific constellations between intrinsic and extrinsic features, such as when the resting state shows a high degree of self-specific organization and encounters stimuli with high degrees of self-specificity (like one’s own name).

Can we thus abandon the concept of self? No! Even if the researcher thinks that she does not need the concept of self anymore and declares it to be an illusion, it will nevertheless come back to her when she goes home and becomes phenomenally conscious and experiences a sense of self, i.e., of her own self. Most importantly, all that is possible only on the basis of her brain’s very neuronal processes, resting-state activity and difference-based coding, which initially, in her working life, inclined her to reject the concept of self.