Transcranial Electrical Stimulation: Methodology and Applications

Low-intensity transcranial current stimulation is a rapidly growing field of research. Transcranial direct current stimulation (tDCS) is the dominant paradigm of this new field, with transcranial alternating current stimulation (tACS) just emerging. Anodal stimulation with tDCS has excitatory effects on the underlying cortex, whereas cathodal stimulation has inhibitory effects. Because both electrodes have significant brain effects when placed at cephalic areas, the term “reference” electrode should be avoided. Most studies have applied tDCS to the motor cortex, the prefrontal cortex, and the occipital cortex. Applications of tDCS include modulation of electrophysiological and hemodynamic brain activity, symptom reduction in neurological and psychiatric pathology, and cognitive improvement in healthy volunteers or clinical populations. There is evidence of motor improvement in patients with stroke, pain reduction in fibromyalgia, improved mood in patients with unipolar or bipolar depression, and reduced craving. Healthy volunteers are shown to improve their verbal fluency, working memory, and implicit learning. Moreover, there are interactions of tDCS with various pharmacological substances. There are no significant side effects, apart from minor skin lesions when tap water is used instead of saline solution in the sponge electrodes. Further research is required to reveal the potential of tACS.     

EEG neurofeedback: a brief overview and an example of peak alpha frequency training for cognitive enhancement in the elderly

Neurofeedback (NF) is an electroencephalographic (EEG) biofeedback technique for training individuals to alter their brain activity via operant conditioning. Research has shown that NF helps reduce symptoms of several neurological and psychiatric disorders, with ongoing research currently investigating applications to other disorders and to the enhancement of non-disordered cognition. The present article briefly reviews the fundamentals and current status of NF therapy and research and illustrates the basic approach with an interim report on a pilot study aimed at developing a new NF protocol for improving cognitive function in the elderly. EEG peak alpha frequency (PAF) has been shown to correlate positively with cognitive performance and to correlate negatively with age after childhood. The present pilot study used a double-blind controlled design to investigate whether training older individuals to increase PAF would result in improved cognitive performance. The results suggested that PAF NF improved cognitive processing speed and executive function, but that it had no clear effect on memory. In sum, the results suggest that the PAF NF protocol is a promising technique for improving selected cognitive functions.     

Investigation of heart rate and blood pressure variability, baroreflex sensitivity, and approximate entropy in acute brain injury patients

Purpose

The purpose of the study was to investigate longitudinally over time heart rate (HR) and blood pressure variability and baroreflex sensitivity in acute brain injury patients and relate them with the severity of neurologic dysfunction and outcome.

Methods

Data from 20 brain injured patients due to multiple causes and treated in the intensive care unit were used, with HR and blood pressure recorded from monitors and analyzed on a daily basis. We performed power spectral analysis estimating low frequencies (LF: 0.04-0.15 Hz), high frequencies (HF: 0.15-0.4 Hz), and their ratio and calculated the approximate entropy, which assesses periodicity within a signal and transfer function (TF), that estimates baroreflex sensitivity. Heart rate variance was considered as a measure of HR variability.

Results

Nonsurvivors (brain dead) had lower approximate entropy (0.65 ± 0.24 vs 0.84 ± 0.26, P < .05) and lower variance mean values (0.48 ± 0.54 vs 1.29 ± 0.42 ms²/Hz, P < .01), lower LF and HF minimum values (0.31 ± 0.88 vs 1.11 ± 0.46, P < .01; and 0.27 ± 0.42 vs 0.86 ± 0.30, P < .01, respectively), lower LF/HF (0.22 ± 0.29 vs 0.62 ± 0.28, P < .01), and lower TF mean values (0.43 ± 0.29 vs 1.11 ± 0.74, P < .05) during their whole stay in the intensive care unit in relation with survivors. The mean variance (P < .05), mean TF (P < .05), and mean LF/HF (P < .05) were significantly successful in separating survivors from nonsurvivors.

Conclusions

We conclude that in acute brain injury patients, low variability, low baroreflex sensitivity, and sustained decrease in LF/HF of HR signals are linked with a high mortality rate.     

Type III cartilage “shield” tympanoplasty: An effective procedure for hearing improvement

OBJECTIVE: To report the hearing results following type III cartilage "shield" tympanoplasty. STUDY DESIGN: Retrospective chart review at a tertiary referral center. METHODS: Conchal cartilage, shaped as a shield, was used to replace the entire tympanic membrane and reconstruct the ossicular chain in patients with an absent incus and diminished space between the stapes superstructure and malleolar manubrium. RESULTS: Between January 1998 and June 2005, 52 patients were treated. The mean age was 32.4 years (range, 7 to 72 years). The mean follow-up was 24 months (range, 12 to 36 months). Graft take was successful in all patients. The average hearing improvement was 11.22 dB (P<0.0001). An air-bone gap of 25 dB or less was achieved in 41 (78.8%) patients. Speech discrimination scores remained unchanged. No complications were identified. CONCLUSION: Type III cartilage "shield" tympanoplasty is an effective technique for hearing improvement in selected patients with chronic otitis media. The results of this procedure are similar to those obtained with partial ossicular replacement prosthesis.     

Mediterranean diet is associated with a lower probability of prodromal Parkinson's disease and risk for Parkinson's disease/dementia with Lewy bodies: A longitudinal study

Background and purpose

Lifestyle factors have been implicated in the long-lasting neurodegenerative process in prodromal Parkinson's disease (pPD). The aim was to investigate the associations between adherence to a Mediterranean diet (MeDi) and longitudinal changes of pPD probability and the development of Parkinson's disease (PD) or pPD in a Mediterranean older population.

Methods

Data from the Hellenic Longitudinal Investigation of Aging and Diet cohort (community-dwelling individuals, aged ≥ 65 years) were used. A detailed food frequency questionnaire was used to evaluate dietary intake and calculate MeDi adherence score, ranging from 0 to 55, with higher scores indicating higher adherence. The probability of pPD was calculated according to the updated Movement Disorder Society research criteria.

Results

In all, 1047 non-PD/dementia with Lewy bodies (DLB) participants were followed for 3 ± 1 years. MeDi adherence was associated with lower increase in pPD probability over time (b = −0.003, 95% confidence interval −0.006 to −0.001, p = 0.010). Forty-nine participants had incident possible/probable pPD (i.e., pPD probability ≥ 30%). Compared to the participants in the lowest quartile of MeDi adherence, those in the higher quartiles had an approximately 60%–70% lower risk for possible/probable pPD (p for trend 0.003). MeDi–pPD associations were driven by both motor and non-motor pPD markers and not from risk markers. Also, 21 participants were diagnosed with PD/DLB at follow-up. For each unit increase in the MeDi score, there was a 9%–10% lower risk for PD/DLB (hazard ratio 0.906 [95% confidence interval 0.823–0.997], p = 0.044).

Conclusions

Mediterranean diet adherence is associated with lower increase in pPD probability over time and lower possible/probable pPD and PD/DLB incidence in older Mediterranean people. More studies are needed to confirm our results in other populations.     

Associations between neuropsychiatric symptoms and incident Alzheimer’s dementia in men versus women

Journal of Neurology - To examine whether associations between individual neuropsychiatric symptoms (NPS) and incident Alzheimer’s dementia (AD) differ in men versus women. Data were acquired...