Chaos theories and therapeutic commonalities among depression, Parkinson's disease, and cardiac arrhythmias

A unified pathogenic hypothesis for mental disorders based on schismogenesis

Major Depressive Disorder, Bipolar Disorder, and Schizophrenia, share significant genetic, epigenetic, and phenotypic overlap, manifesting as dimensional psychopathology and convergent neuroimaging findings. These shared features have led to various models exploring common underlying pathophysiological mechanisms, including excitatory-inhibitory imbalance, the triple network model, network analysis, and social disconnection. While these models offer valuable insights, a unifying framework remains elusive. Schismogenesis, a transdisciplinary construct, is proposed to reconcile divergent perspectives on mental health conditions. Characterized by positive feedback loops leading to functional dissociation due to insufficient inhibitory control, complementary schismogenesis results in rigid hyperactivation and hypoactivation within neural, cognitive, and social networks, compromising system flexibility. This pathological process underlies the core features of Major Depressive Disorder, Bipolar Disorder, and Schizophrenia, depending on its location within networks. The schismogenesis hypothesis suggests that when individuals are overwhelmed by excessive stress or tension, they may experience a breakdown or disconnection to prevent irreversible damage, reflecting evolutionary adaptations. Importantly, the potential reversibility of schismogenesis, particularly through interventions that facilitate system reintegration, suggests promising therapeutic avenues for further exploration.

Biopsychosocial model in Depression revisited

There are two fundamental etiological perspectives about mental disorders; biomedical and psychosocial. The biopsychosocial model has claimed to integrate these two perspectives in a scientific way, signalling their interconnection and interdependence. To that end, it used a systemic conceptual framework, taking advantage of the possibilities which it offers to establish general principles for diverse systems, independently of their physical, biological or sociological nature. In recent years, drawing on the theory of systems, theories have been developing of the dynamic non-linear systems, applicable to networks of a large quantity of densely interconnected elements (also called complex systems), like the mind or the brain. We believe that this revised systemic conceptual framework can bring integrative ideas to apply to Depression, such as the "binding dysfunction" concept we use in this article. According to this, vulnerability or predisposition to Depression would be associated with the imbalance between activating and inhibiting interactions (between some cognitions and emotions at a mental level, and between certain neuronal groups at a cerebral level). Precipitating factors would imply the increase of the activation level over this pattern of cognitions and emotions, or over those neuronal systems. When stress goes beyond the vulnerability threshold an excessive positive feedback between cognitions and emotions would appear (and between groups of neurons) with insufficient inhibitory control to mitigate it, which would imply a mental/cerebral dissociation in dominions of different level of activation. As a consequence, the generation and dissolution of patterns of cerebral and mental activation will no longer have the dynamism and flexibility that permits an optimal interaction with the environment ("binding dysfunction"). Therefore, our hypothesis is that the person with Depression will suffer at a cerebral level a functional dissociation in neural dominions (some rigidly hyperactive and others rigidly hypoactive) in determined locations, which would be a different combination from those found in other mental disorders. At a mental level, this would correlate with a functional dissociation in several cognitive-emotive dominions; some corresponds to over activated patterns of "depressive" cognitions and emotions that for that reason invade the consciousness frequently, intrusively and repetitively; meanwhile there are other alternative hypoactive emotions and cognitions that do not manage to become powerful enough to avoid the consequent distortion in the communication with the environment.

Moderate exercise and chronic stress produce counteractive effects on different areas of the brain by acting through various neurotransmitter receptor subtypes: a hypothesis

Background

Regular, "moderate", physical exercise is an established non-pharmacological form of treatment for depressive disorders. Brain lateralization has a significant role in the progress of depression. External stimuli such as various stressors or exercise influence the higher functions of the brain (cognition and affect). These effects often do not follow a linear course. Therefore, nonlinear dynamics seem best suited for modeling many of the phenomena, and putative global pathways in the brain, attributable to such external influences.

Hypothesis

The general hypothesis presented here considers only the nonlinear aspects of the effects produced by "moderate" exercise and "chronic" stressors, but does not preclude the possibility of linear responses. In reality, both linear and nonlinear mechanisms may be involved in the final outcomes. The well-known neurotransmitters serotonin (5-HT), dopamine (D) and norepinephrine (NE) all have various receptor subtypes. The article hypothesizes that 'Stress' increases the activity/concentration of some particular subtypes of receptors (designated nt_s) for each of the known (and unknown) neurotransmitters in the right anterior (RA) and left posterior (LP) regions (cortical and subcortical) of the brain, and has the converse effects on a different set of receptor subtypes (designated nt_h). In contrast, 'Exercise' increases nt_h activity/concentration and/or reduces nt_s activity/concentration in the LA and RP areas of the brain. These effects may be initiated by the activation of Brain Derived Neurotrophic Factor (BDNF) (among others) in exercise and its suppression in stress.

Conclusion

On the basis of this hypothesis, a better understanding of brain neurodynamics might be achieved by considering the oscillations caused by single neurotransmitters acting on their different receptor subtypes, and the temporal pattern of recruitment of these subtypes. Further, appropriately designed and planned experiments will not only corroborate such theoretical models, but also shed more light on the underlying brain dynamics.

Psychopathology and the binding problem

Normal cerebral activity is based on the rapid and flexible alternation of an enormous quantity of spatial-temporal patterns of neuronal firing. There is still much to learn about the mechanism that keeps neurons on functionally closed assemblies firing in synchronization. The explanation of this mechanism is the so called 'binding problem', one of the cornerstones of the generation of perceptions, cognitions, emotions and behaviours by the brain, and therefore of great interest to psychiatry. We explore the possibility that a 'binding dysfunction' could be a relevant aspect of the pathophysiology of mental disorders, and apply it to schizophrenia, in an attempt to integrate some neurobiological findings in this disorder, including a few preliminary data obtained with transcranial magnetic stimulation (TMS).

Functional cerebral asymmetry in affective disorders: new facts contributed by transcranial magnetic stimulation

A growing body of experimental data usually finds a slightly lower activation in the left hemisphere than in the right in depressive syndromes, whereas the opposite occurs in mania. Transcranial magnetic stimulation (TMS) seems to have a distinctive lateralized effect with manic or depressed patients. These clinical findings provide new elements for discussion of the significance of unbalanced hemispherical activation as a biological substrate in affective disorders. Based on these data and on the theories of chaos and complexity, a hypothesis for the physiopathology of affective disorders and the functional mechanism of TMS is proposed. This hypothesis is in agreement with valence theory.

Chaos in the brain: a short review alluding to epilepsy, depression, exercise and lateralization

Electroencephalograms (EEGs) reflect the electrical activity of the brain. Even when they are analyzed from healthy individuals, they manifest chaos in the nervous system. EEGs are likely to be produced by a nonlinear system, since a nonlinear system with at least 3 degrees of freedom (or state variables) may exhibit chaotic behavior. Furthermore, such systems can have multiple stable states governed by "chaotic" ("strange") attractors. A key feature of chaotic systems is the presence of an infinite number of unstable periodic fixed points, which are found in spontaneously active neuronal networks (e.g., epilepsy). The brain has chemicals called neurotransmitters that convey the information through the 10(16) synapses residing there. However, each of these neurotransmitters acts through various receptors and their numerous subtypes, thereby exhibiting complex interactions. Albeit in epilepsy the role of chaos and EEG findings are well proven, in another condition, i.e., depression, the role of chaos is slowly gaining ground. The multifarious roles of exercise, neurotransmitters and (cerebral) hemispheric lateralization, in the case of depression, are also being established. The common point of reference could be nonlinear dynamics. The purpose of this review is to study those nonlinear/chaotic interactions and point towards new theoretical models incorporating the oscillation caused by the same neurotransmitter acting on its different receptor subtypes. This may lead to a better understanding of brain neurodynamics in health and disease.

Modest adjunctive benefit with transcranial magnetic stimulation in medication-resistant depression

BACKGROUND

Controverted results have been obtained using high frequency transcranial magnetic stimulation (HF-rTMS) as an antidepressant treatment.

METHODS

Forty patients suffering from drug-resistant major depression received ten sessions of HF-rTMS at 90% of the motor threshold on the left prefrontal cortex or sham stimulation, added to their pharmacological treatment, in a randomized double-blind design. In a second open phase, patients still fulfilling criteria of inclusion received ten additional sessions of HF-rTMS at 90 or 110%.

RESULTS

Real, but not sham HF-rTMS, was associated with a significant decrease in the Hamilton Depression Rating Scale, but only twelve patients decreased more than 50%.

CONCLUSIONS

Left prefrontal HF-rTMS was effectively associated with antidepressant treatment, although the size effect was small.

LIMITATIONS

Shortage of the sample and control difficulties of the placebo effect.

CLINICAL RELEVANCE

Questionable in more than half of the patients studied.