Contributions of dysfunctional plasticity mechanisms to the development of atypical perceptual processing

Experimental studies of sensory plasticity during development in birds and mammals have highlighted the importance of sensory experiences for the construction and refinement of functional neural circuits. We discuss how dysregulation of experience-dependent brain plasticity can lead to abnormal perceptual representations that may contribute to heterogeneous deficits symptomatic of several neurodevelopmental disorders. We focus on alterations of somatosensory processing and the dynamic reorganization of cortical synaptic networks that occurs during early perceptual development. We also discuss the idea that the heterogeneity of strengths and weaknesses observed in children with neurodevelopmental disorders may be a direct consequence of altered plasticity mechanisms during early development. Treating the heterogeneity of perceptual developmental trajectories as a phenomenon worthy of study rather than as an experimental confound that should be overcome may be key to developing interventions that better account for the complex developmental trajectories experienced by modern humans.

Increased parietal circuit-breaker activity in delta frequency band and abnormal delta/theta band connectivity in salience network in hyperacusis subjects

Recent studies have suggested that hyperacusis, an abnormal hypersensitivity to ordinary environmental sounds, may be characterized by certain resting-state cortical oscillatory patterns, even with no sound stimulus. However, previous studies are limited in that most studied subjects with other comorbidities that may have affected cortical activity. In this regard, to assess ongoing cortical oscillatory activity in idiopathic hyperacusis patients with no comorbidities, we compared differences in resting-state cortical oscillatory patterns between five idiopathic hyperacusis subjects and five normal controls. The hyperacusis group demonstrated significantly higher electrical activity in the right auditory-related cortex for the gamma frequency band and left superior parietal lobule (SPL) for the delta frequency band versus the control group. The hyperacusis group also showed significantly decreased functional connectivity between the left auditory cortex (AC) and left orbitofrontal cortex (OFC), between the left AC and left subgenual anterior cingulate cortex (sgACC) for the gamma band, and between the right insula and bilateral dorsal anterior cingulate cortex (dACC) and between the left AC and left sgACC for the theta band versus the control group. The higher electrical activity in the SPL may indicate a readiness of “circuit-breaker” activity to shift attention to forthcoming sound stimuli. Also, because of the disrupted salience network, consisting of the dACC and insula, abnormally increased salience to all sound stimuli may emerge, as a consequence of decreased top-down control of the AC by the dACC and dysfunctional emotional weight attached to auditory stimuli by the OFC. Taken together, abnormally enhanced attention and salience to forthcoming sound stimuli may render hyperacusis subjects hyperresponsive to non-noxious auditory stimuli.

Neural plasticity and network remodeling: From concepts to pathology

Neuroplasticity has been subject to a great deal of research in the last century. Recently, significant emphasis has been placed on the global effect of localized plastic changes throughout the central nervous system, and on how these changes integrate in a pathological context. Specifically, alterations of network functionality have been described in various pathological contexts to which corresponding structural alterations have been proposed. However, considering the amount of literature and the different pathological contexts, an integration of this information is still lacking. In this paper we will review the concepts of neural plasticity as well as their repercussions on network remodeling and provide a possible explanation to how these two concepts relate to each other. We will further examine how alterations in different pathological contexts may relate to each other and will discuss the concept of plasticity diseases, its models and implications.

Dysfunctional noise cancelling of the rostral anterior cingulate cortex in tinnitus patients

Background

Peripheral auditory deafferentation and central compensation have been regarded as the main culprits of tinnitus generation. However, patient-to-patient discrepancy in the range of the percentage of daytime in which tinnitus is perceived (tinnitus awareness percentage, 0 – 100%), is not fully explicable only by peripheral deafferentation, considering that the deafferentation is a stable persisting phenomenon but tinnitus is intermittently perceived in most patients. Consequently, the involvement of a dysfunctional noise cancellation mechanism has recently been suggested with regard to the individual differences in reported tinnitus awareness. By correlating the tinnitus awareness percentage with resting-state source-localized electroencephalography findings, we may be able to retrieve the cortical area that is negatively correlated with tinnitus awareness percentage, and then the area may be regarded as the core of the noise cancelling system that is defective in patients with tinnitus.

Methods and Findings

Using resting-state cortical oscillation, we investigated 80 tinnitus patients by correlating the tinnitus awareness percentage with their source-localized cortical oscillatory activity and functional connectivity. The activity of bilateral rostral anterior cingulate cortices (ACCs), left dorsal- and pregenual ACCs for the delta band, bilateral rostral/pregenual/subgenual ACCs for the theta band, and left rostral/pregenual ACC for the beta 1 band displayed significantly negative correlations with tinnitus awareness percentage. Also, the connectivity between the left primary auditory cortex (A1) and the rostral ACC, as well as between the left A1 and the subgenual ACC for the beta 1 band, were negatively correlated with tinnitus awareness percentage.

Conclusions

These results may designate the role of the rostral ACC as the core of the descending noise cancellation system, and thus dysfunction of the rostral ACC may result in perception of tinnitus. The present study also opens a possibility of tinnitus modulation by neuromodulatory approaches targeting the rostral ACC.

Matrix metalloproteinases in autism spectrum disorders

Autism Spectrum Disorders (ASD) are group of developmental disabilities with a complex neurobiological basis including putative changes in the immune system. They are characterized by pervasive qualitative abnormalities in social interactions, communication, and stereotyped behaviour. Matrix metalloproteinases (MMPs) represent a group of proteases which play an important role in neuroinflammation and neurodevelopment. Therefore, they possibly have a crucial function in the etiopathology of ASD. In this review, we summarize the plausibility of the hypothesis that MMPs are involved in the neuropathology of ASD. Possible pathways through which MMPs can contribute to the pathogenesis of ASD are discussed including neuroinflammatory mechanisms inclusive of mediating neuropathological effects of infections, the associations between MMPs and other biomarkers such as cytokines, chemokines and neurotrophic factors. Despite sufficient evidence for such an involvement of MMPs in the neuropathology of ASD, they have not yet been extensively studied in this context. Thus, further research in this field is not only urgently needed but also very promising and may also lead to new therapeutic approaches.

Neonatal levels of neurotrophic factors and risk of autism spectrum disorders

OBJECTIVE

To examine levels of 3 neurotrophic factors (NTFs): Brain derived neurotrophic factor (BDNF), Neurotrophin-4 (NT-4), and transforming growth factor-β (TGF-β) in dried blood spot samples of neonates diagnosed with autism spectrum disorders (ASD) later in life and frequency-matched controls.

METHOD

Biologic samples were retrieved from the Danish Newborn Screening Biobank. NTFs for 414 ASD cases and 820 controls were measured using Luminex technology. Associations were analyzed with continuous measures (Tobit regression) as well as dichotomized at the lower and upper 10th percentiles cutoff points derived from the controls' distributions (logistic regression).

RESULTS

ASD cases were more likely to have BDNF levels falling in the lower 10th percentile (odds ratios [OR], 1.53 [95% confidence intervals (CI), 1.04-2.24], P-value = 0.03). Similar pattern was seen for TGF-β in females with ASD (OR, 2.36 [95% CI, 1.05-5.33], P-value = 0.04). For NT-4, however, ASD cases diagnosed with ICD-10 only were less likely to have levels in upper 10th percentile compared with controls (OR, 0.22 [95% CI, 0.05-0.98], P-value = 0.05).

CONCLUSION

Results cautiously indicate decreased NTFs levels during neonatal period in ASD. This may contribute to the pathophysiology of ASD through impairments of neuroplasticity. Further research is required to confirm our results and to examine the potential therapeutic effects of NTFs in ASD.

Non-invasive physiological monitoring of exercise and fitness

OBJECTIVE

To review the current research of new emerging diagnostic technology for non-invasive physiological monitoring of exercise and fitness. As a personal trainer, I believe that exercise can improve the conditions of several diseases and/or events such as stroke, post-traumatic head injury, spinal cord injury, and a multitude of other diseases. This compilation of information will allow health care providers tools of a non-invasive manner to promote healing and health that go beyond the initial event. Allowing patients continued managed care beyond what is believed to be their plateau.

MATERIAL AND METHOD

Review science-based research involving non-invasive technology, including cardiovascular evaluations: heart rate monitors, near-infrared spectroscopy, blood pressure, and electrocardiography; motor capabilities: surface electromyography and manual testers, i.e. dynamometer, and digital and video photography; radiological monitoring: magnetic resonance imaging, three-dimensional computer tomography, and laser Doppler.

RESULTS

This investigation has found that a new approach should be implemented for non-invasive physiological monitoring of exercise and fitness through development and utilization across a wide variety of equipment, and monitoring technology. This non-invasive methodology will not only motivate but encourage individuals to begin and remain compliant with an exercise program allowing a variety of health care providers to assist in patient care.

DISCUSSION

We need to shift the paradigm from taking care of the sick to maintaining the health of our patients. This can be accomplished with non-invasive evaluation, tracking, and monitoring tools. Many of the suggestions for monitoring are used in a clinical setting rather than a general fitness environment. These monitoring tests need to be economical as well as available for continual re-evaluation.