Sleep function and synaptic homeostasis

Tononi, G., & Cirelli, C. (2006). Sleep function and synaptic homeostasis. Sleep medicine reviews10(1), 49-62.


This paper reviews a novel hypothesis about the functions of slow wave sleep—the synaptic homeostasis hypothesis. According to the hypothesis, plastic processes occurring during wakefulness result in a net increase in synaptic strength in many brain circuits. The role of sleep is to downscale synaptic strength to a baseline level that is energetically sustainable, makes efficient use of gray matter space, and is beneficial for learning and memory. Thus, sleep is the price we have to pay for plasticity, and its goal is the homeostatic regulation of the total synaptic weight impinging on neurons. The hypothesis accounts for a large number of experimental facts, makes several specific predictions, and has implications for both sleep and mood disorders

Consciousness without a cerebral cortex

Merker, B. (2007). Consciousness without a cerebral cortex: A challenge for neuroscience and medicine. Behavioral and brain sciences30(1), 63-81.


A broad range of evidence regarding the functional organization of the vertebrate brain – spanning from comparative neurology to experimental psychology and neurophysiology to clinical data – is reviewed for its bearing on conceptions of the neural organization of consciousness. A novel principle relating target selection, action selection, and motivation to one another, as a means to optimize integration for action in real time, is introduced. With its help, the principal macrosystems of the vertebrate brain can be seen to form a centralized functional design in which an upper brain stem system organized for conscious function performs a penultimate step in action control. This upper brain stem system retained a key role throughout the evolutionary process by which an expanding forebrain – culminating in the cerebral cortex of mammals – came to serve as a medium for the elaboration of conscious contents. This highly conserved upper brainstem system, which extends from the roof of the midbrain to the basal diencephalon, integrates the massively parallel and distributed information capacity of the cerebral hemispheres into the limited-capacity, sequential mode of operation required for coherent behavior. It maintains special connective relations with cortical territories implicated in attentional and conscious functions, but is not rendered nonfunctional in the absence of cortical input. This helps explain the purposive, goal-directed behavior exhibited by mammals after experimental decortication, as well as the evidence that children born without a cortex are conscious. Taken together these circumstances suggest that brainstem mechanisms are integral to the constitution of the conscious state, and that an adequate account of neural mechanisms of conscious function cannot be confined to the thalamocortical complex alone.

Keywords: action selection; anencephaly; central decision making; consciousness; control architectures; hydranencephaly; macrosystems; motivation; target selection; zona incerta

The conscious id

Solms, M. (2013). The conscious id. Neuropsychoanalysis15(1), 5-19.


Two aspects of the body are represented in the brain, and they are represented differently. The most important difference is that the brain regions for the two aspects of the body are associated with different aspects of consciousness. Very broadly speaking, the brainstem mechanisms derived from the autonomic body are associated with affective consciousness, and the cortical mechanisms derived from the sensorimotor body are associated with cognitive consciousness. Moreover, the upper brainstem is intrinsically conscious whereas the cortex is not; it derives its consciousness from the brainstem. These facts have substantial implications for psychoanalytic metapsychology because the upper brainstem (and associated limbic structures) performs the functions that Freud attributed to the id, while the cortex (and associated forebrain structures) performs the functions he attributed to the ego. This means that the id is the fount of consciousness and the ego is unconscious in itself. The basis for these conclusions, and some of their implications, are discussed here in a preliminary fashion. Keywords: affect; cognition; conscious; ego; id; unconscious

Mentalizing homeostasis: The social origins of interoceptive inference

Fotopoulou, A., & Tsakiris, M. (2017). Mentalizing homeostasis: The social origins of interoceptive inference. Neuropsychoanalysis19(1), 3-28.
Is the self already relational in its very bodily foundations? The question of whether our mental life is initially and primarily shaped by embodied dimensions of the individual or by interpersonal relations is debated in many fields, including psychology, philosophy, psychoanalysis, and more recently, cognitive neuroscience. In this interdisciplinary target article, we put forward the radical claim that even some of the most minimal aspects of selfhood, namely the feeling qualities associated with being an embodied subject, are fundamentally shaped by embodied interactions with other people in early infancy and beyond. Such embodied interactions allow the developing organism to mentalize its homeostatic regulation. In other words, embodied interactions contribute directly to the building of mental models of the infant’s physiological states, given the need to maintain such states within a given dynamic range despite internal or external perturbations. Specifically, our position rests on the following three propositions: (1) the progressive integration and organization of sensory and motor signals constitutes the foundations of the minimal self, a process which we have linked to contemporary, computational models of brain function and named “embodied mentalization”; (2) interactions with other people are motivated and constrained by the same principles that govern the “mentalization” of sensorimotor signals in the individual – and hence the mentalization of one’s body can include signals from other bodies in physical proximity and interaction, especially in interaction with particular bodies. (3) Crucially, given the dependency of humans in early infancy, there is a “homeostatically necessary” plethora of such embodied “proximal” interactions, especially as regards interoception. Collectively, such experiences of proximal intercorporeality “sculpt” the mentalization process and hence the constitution of the minimal self, including the progressive sophistication of mental distinctions between “subject-object,” “self-other” and even “pleasure-pain.” Finally, we explore notions of cardiac and more broadly interoceptive awareness as later, cognitive acquisitions that allow us to progressively solidify such distinctions, as well as understand and empathise with other people.
self; affect; emotion; awareness; social cognition; touch; interoception; intersubjectivity; embodiment; skin ego; minimal self

Instincts and homeostasis

Kubie, L. S. (1948). Instincts and homeostasis. Psychosomatic Medicine, 10, 15–30.


In an objective re-evaluation of the concept of instinct, the author supports two of Freud’s largely neglected contributions that instincts must be classified on a physiological rather than on a psychological basis and that they represent a demand made by the body on the mental apparatus. No absolute distinctions can be made between instincts and drives; differences are rather quantitative than qualitative. Instincts can be arranged in a hierarchy “from a preponderance of biochemical influences on the neuronal pattern to a preponderance of psychologic influence.”

Homeostasis as an explanatory principle in psychology

Fletcher, J. M. (1942). Homeostasis as an explanatory principle in psychology. Psychological Review, 49(1), 80–87.


Cannon originated the term homeostasis to describe the tendency of organisms to maintain stability or uniformity in their body states. By an extension of the principle, it might be used to describe the already demonstrated tendency to maintain status at the mental level of behavior, even in anticipation of the disturbing conditions. Instances of the usefulness of the term are drawn from such fields as perception (constancy), habit formation, learning, reasoning, work level (level of aspiration), and personality adjustment, to explain such mechanisms as rationalization and compensation.


Homeostasis, discrepancy, dissonance. A theory of motives and motivation

Stagner, R. (1977). Homeostasis, discrepancy, dissonance. Motivatíon and emotion1(2), 103-138.


The argument is presented that motivation is equated to energy mobilization, and that the mechanism involved in all such instances of arousal is a discrepancy-detecting and -reducing mechanism. Motives are specific categories of discrepancy but they operate through a common arousal system. This system, further, may be coopted into (integrated into) processes involving social comparison, relative deprivation, discrepancies with respect to ego-involved persons and objects, and industrial, social, and political motives. While biological homeostasis provides the basic CNS system, other forms of discrepancy-triggered energy arousal must be recognized as important. Hedonism and theories of curiosity, as well as other similar factors, can be subsumed under discrepancy theory.