Clinical studies suggest the therapeutic potential of psychedelics, including ayahuasca, DMT, psilocybin, and LSD, in stress-related disorders. These substances induce cognitive, antidepressant, ...anxiolytic, and antiaddictive effects suggested to arise from biological changes similar to conventional antidepressants or the rapid-acting substance ketamine. The proposed route is by inducing brain neuroplasticity. This review attempts to summarize the evidence that psychedelics induce neuroplasticity by focusing on psychedelics' cellular and molecular neuroplasticity effects after single and repeated administration. When behavioral parameters are encountered in the selected studies, the biological pathways will be linked to the behavioral effects. Additionally, knowledge gaps in the underlying biology of clinical outcomes of psychedelics are highlighted. The literature searched yielded 344 results. Title and abstract screening reduced the sample to 35; eight were included from other sources, and full-text screening resulted in the final selection of 16 preclinical and four clinical studies. Studies (
n
= 20) show that a single administration of a psychedelic produces rapid changes in plasticity mechanisms on a molecular, neuronal, synaptic, and dendritic level. The expression of plasticity-related genes and proteins, including Brain-Derived Neurotrophic Factor (BDNF), is changed after a single administration of psychedelics, resulting in changed neuroplasticity. The latter included more dendritic complexity, which outlasted the acute effects of the psychedelic. Repeated administration of a psychedelic directly stimulated neurogenesis and increased BDNF mRNA levels up to a month after treatment. Findings from the current review demonstrate that psychedelics induce molecular and cellular adaptations related to neuroplasticity and suggest those run parallel to the clinical effects of psychedelics, potentially underlying them. Future (pre)clinical research might focus on deciphering the specific cellular mechanism activated by different psychedelics and related to long-term clinical and biological effects to increase our understanding of the therapeutic potential of these compounds.
•TDCS boosts neuroplastic mechanisms associated with procedural learning.•Targeting M1 seems promising for implicit motor learning.•Targeting prefrontal areas improves acquisition and retention of ...implicit association and memory.•The cerebellum is emerging as a promising target area of stimulation for both motor and non-motor procedural learning.•tDCS for procedural rehabilitation is at early stages and establishing standardised tDCS protocols is needed to propose effective clinical protocols.
Procedural learning is the acquisition of motor and non-motor skills through a gradual process that increases with practice. Impairments in procedural learning have been consistently demonstrated in neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. Considering that noninvasive brain stimulation modulates brain activity and boosts neuroplastic mechanisms, we reviewed the effects of coupling transcranial direct current stimulation (tDCS) with training methods for motor and non-motor procedural learning to explore tDCS potential use as a tool for enhancing implicit learning in healthy and clinical populations. The review covers tDCS effects over i. motor procedural learning, from basic to complex activities; ii. non-motor procedural learning; iii. procedural rehabilitation in several clinical populations. We conclude that targeting the primary motor cortex and prefrontal areas seems the most promising for motor and non-motor procedural learning, respectively. For procedural rehabilitation, the use of tDCS is yet at an early stage but some effectiveness has been reported for implicit motor and memory learning. Still, systematic comparisons of stimulation parameters and target areas are recommended for maximising the effectiveness of tDCS and its robustness for procedural rehabilitation.
Tinnitus is a symptom with a significant incidence in the general population, usually of unclear etiology, that can cause serious difficulties in people's daily functioning, significantly impair the ...quality of life, and have a negative impact on mental health. The paper aims to present a brief overview of current knowledge about this frequent and unpleasant phenomenon, including epidemiology, etiology, clinical presentation, diagnosis, and treatment. The paper highlights contemporary theories of tinnitus that link damage to the peripheral organ of hearing and the consequent neuronal changes involved in the subjective experience, which are the target sites for treating psychological disorders associated with tinnitus. The psychiatric approach to tinnitus is aimed not so much at reducing the sound intensity as at reducing the negative experience of this phenomenon and preventing the development or worsening of existing psychological disorders. The results of previous researches indicate numerous therapeutic options for treating tinnitus, including drugs, cognitive-behavioral therapy, and neuromodulation techniques with promising results.
Tinitus je simptom sa značajnom pojavnošću u općoj populaciji, najčešće nejasne etiologije, koji može izazvati ozbiljne poteškoće u svakodnevnom funkcioniranju, značajno narušiti kvalitetu života i dovesti do negativnog utjecaja na psihičko zdravlje. Cilj rada je prikazati kratki pregled dosadašnjih spoznaja o ovome, često neugodnom fenomenu, uključujući epidemiologiju, etiologiju, kliničku sliku, dijagnostiku i liječenje. U radu su istaknute suvremene teorije tinitusa koje povezuju oštećenje perifernog organa sluha i posljedične neuronske promjene uključene u subjektivni doživljaj, koje su ciljno mjesto liječenja psihičkih smetnji udruženih s tinitusom. Psihijatrijski pristup tinitusu usmjeren je, ne toliko na smanjenje zvučnog intenziteta, koliko na smanjenje negativnog doživljaja ovoga fenomena i sprječavanje razvoja ili pogoršanja postojećih psihičkih poremećaja. Rezultati dosadašnjih istraživanja ukazuju na brojne terapijske mogućnosti liječenja tinitusa, uključujući lijekove, kognitivno-bihevioralnu terapiju, te neuromodulacijske tehnike s obećavajućim rezultatima.
Executive function (EF) skills are neurocognitive skills that support the reflective, top-down coordination and control of other brain functions, and there is neural and behavioral evidence for a ...continuum from more "cool" EF skills activated in emotionally neutral contexts to more "hot" EF skills needed for the reversal of motivationally significant tendencies. Difficulties in EF are transdiagnostic indicators of atypical development. A neurodevelopmental model traces the pathway from adverse childhood experiences and stress to disruption of the development of neural systems supporting reflection and EF skills to an increased risk for general features of psychopathology. Research indicates that EF skills can be cultivated through scaffolded training and are a promising target for therapeutic and preventive intervention. Intervention efficacy can be enhanced by mitigating disruptive bottom-up influences such as stress, training both hot and cool EF skills, and adding a reflective, metacognitive component to promote far transfer of trained skills.
Neuroplasticity is defined as the property of the brain to adapt to environmental pressures, experiences, and challenges including brain damage. It is a lifelong capacity of the brain to change and ...rewire itself in response to the stimulation of learning and experience. Based upon this input, several conclusions were recently appearing on the surface. First, there appears to be tremendous latent plasticity even in the adult brain. Second, the brain should be thought of, not as a hierarchy of organized autonomous modules, each of which delivers its output to the next level, but as a set of complex interacting networks that are in a state of dynamic equilibrium with the brain’s environment. Both principles can be potentially exploited in a clinical context to facilitate recovery of function. Promoting neuroplasticity in an enriched environment will eventually result in dendritic branching, synapses, glial processes, brain weight, and cortical thickness. Currently, it is believed that activity drives reorganization of cerebral networks, which is paralleled by functional improvements in cases of acquired brain injuries that are usually in need of intense rehabilitation programs. Numeral studies have demonstrated reorganization of brain activity pattern in response to intense training of motor and cognitive tasks and imagination of movements. For instance, promising results were shown using feedback techniques, like mirror visual feedback (MVF) improving chronic regional pain syndrome and hemiparesis following stroke. Evidence based therapeutic interventions using neuroplasticity as its base include aerobic exercise, bilateral arm training, constraint induced movement therapy,body weight supported treadmill training, mirror therapy, action observation, motor imagery/mental practice, functional electrical stimulation and music therapy.Promising therapies that may enhance training-induced cognitive and motor learning, such as brain stimulation and neuropharmacological interventions, were also identified, along with arousing questions involving more updated ways to use neuroplasticity in improving quality of life in cases of human disability.
•Executive function (EF) skills are essential for goal-directed problem solving.•The Iterative Reprocessing (IR) model describes the development of EF at multiple levels of analysis.•Reflection, or ...the reprocessing of information, provides a foundation for EF.•Training reflection and rule use improves EF and theory of mind, and changes neural function.
Key executive function (EF) skills (cognitive flexibility, working memory, inhibitory control) are essential for goal-directed problem solving and reflective learning. This article describes executive function (EF) and its development from the perspective of the Iterative Reprocessing (IR) model. According to this model, reflection, or the reflective reprocessing of information prior to responding, provides a foundation for the control of attention – flexibly, over time, and selectively (i.e., cognitive flexibility, working memory, and inhibitory control). This goal-directed modulation of attention is typically verbally mediated and involves the formulation and maintenance in working memory of explicit action-oriented rules. The development of EF is made possible, in part, by increases in the efficiency of reflective reprocessing which allow for increases in the hierarchical complexity of the rules that can be used to characterize problems and select context-appropriate rules for responding. Research designed to test the model indicates that a brief intervention targeting reflection and rule use leads to improved EF and theory of mind, and produces corresponding changes in neural function.
•First study to use complexity measures to investigate ECT-effects.•Significant increase of Higuchi's fractal dimension (HFD) following ECT.•Right anterior hippocampal HFD was associated with ...reduction in depression severity.•Predictive value of temporal pole fractal dimension of cortical morphology (FD-CM).•Complexity measures provide a novel complementary measure to investigate ECT.
Numerous studies show that electroconvulsive therapy (ECT) induces hippocampal neuroplasticity, but findings are inconsistent regarding its clinical relevance. This study aims to investigate ECT-induced plasticity of anterior and posterior hippocampi using mathematical complexity measures in neuroimaging, namely Higuchi's fractal dimension (HFD) for fMRI time series and the fractal dimension of cortical morphology (FD-CM). Furthermore, we explore the potential of these complexity measures to predict ECT treatment response.
Twenty patients with a current depressive episode (16 with major depressive disorder and 4 with bipolar disorder) underwent MRI-scans before and after an ECT-series. Twenty healthy controls matched for age and sex were also scanned twice for comparison purposes. Resting-state fMRI data were processed, and HFD was computed for anterior and posterior hippocampi. Group-by-time effects for HFD in anterior and posterior hippocampi were calculated and correlations between HFD changes and improvement in depression severity were examined. For FD-CM analyses, we preprocessed structural MRI with CAT12′s surface-based methods. We explored group-by-time effects for FD-CM and the predictive value of baseline HFD and FD-CM for treatment outcome.
Patients exhibited a significant increase in bilateral hippocampal HFD from baseline to follow-up scans. Right anterior hippocampal HFD increase was associated with reductions in depression severity. We found no group differences and group-by-time effects in FD-CM. After applying a whole-brain regression analysis, we found that baseline FD-CM in the left temporal pole predicted reduction of overall depression severity after ECT. Baseline hippocampal HFD did not predict treatment outcome.
This study suggests that HFD and FD-CM are promising imaging markers to investigate ECT-induced neuroplasticity associated with treatment response.
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