Signal processing technique to extract neuronal activity from noise

A method of extracting extracellularly recorded action potentials from background electronic noise is described. Segments of traces containing stimulus-induced activity are Fourier transformed and the increase in the total power density over that of control noise segments is used as a measure of stimulus-induced neuronal activity. We show first, with observations from the amphibian visual system and mammalian auditory system, that our technique yields similar quantitative information to that obtained from the conventional spike counting method when the recording arrangement is optimal. Moreover, the size and centre of a visual receptive field can be determined even when the evoked action potentials are buried in the background noise. To investigate the potential of this technique further, we have used it to study the auditory responses in the amphibian midbrain. The power spectral density, we demonstrate here, is proportional to the stimulus intensity over a wide range, and varies systematically with stimulus frequency and the direction of sound source. Other possible applications of this technique, together with the theoretical basis for it, are discussed.     

A fluorescence confocal assay to assess neuronal viability in brain slices

Hippocampal slice models are used to study the mechanisms of ischemia-induced neurotoxicity and to assess the neuroprotective potential of novel therapeutic agents. A number of morphological and functional endpoints are available to assess neuronal viability. The slice model also allows the study of selectively vulnerable neuronal populations within the same preparation. The fluorescence procedure described here provides a method of assessing the viability of neurons in rat hippocampal slices exposed to hypoxic-hypoglycemic conditions. Control and/or treated slices that had been subjected to a 10 min oxygen-glucose deprivation insult are double stained with calcein-AM (4 μM), which stains live cells green, and ethidium homodimer (6 μM), which stains the nucleus of dead cells red. The stained slices are then imaged using confocal microscopy. Vulnerable neurons in the CA1 region of slices deprived of oxygen and glucose became increasingly permeant to ethidium homodimer over the 4 h reperfusion period. Exposure to low Ca²⁺ concentration (0.3 mM) or the N-, P- and Q-type Ca²⁺ channel antagonist MVIIC (100 nM), which have been shown to be neuroprotective in this model of ischemia using field evoked post-synaptic potential (EPSP) measures as an endpoint, were also shown to be protective using the fluorescence assay.     

Using dreams to assess clinical change during treatment

This article describes several studies that examine the relationship between the manifest content of selected dreams reported by patients and their clinical progress during psychoanalytic and psychodynamically oriented treatment. There are a number of elements that dreaming and psychotherapy have in common: affect regulation; conflict resolution; problem-solving; self-awareness; mastery and adaptation. Four different studies examined the relationship between the manifest content of selected dreams and clinical progress during treatment. In each study, the ratings of manifest content and clinical progress by independent observers were rank-ordered and compared. In three of the four studies there was a significant correlation between the rankings of manifest content and the rankings of clinical progress. This finding suggests that the manifest content of dreams can be used as an independent variable to assess clinical progress during psychoanalytic and psychodynamically oriented treatment.     

Using subdural electrodes to assess the safety of resections

Subdural electrodes are frequently used to aid in the neurophysiological assessment of patients with intractable seizures. We review their use for localizing cortical regions supporting movement, sensation, and language.     

Using reaction time to assess patients with unilateral neglect and extinction

Brain damage often results in visual defects and/or higher order visuo-spatial disorders including the syndromes of unilateral neglect and extinction. These syndromes and their associated behavioral sequelae are described along with several standard assessments and methods for behaviorally quantifying such deficits. In particular, the advantages of the reaction time measures commonly used by cognitive neuroscientists are surveyed. In order to illustrate how reaction time measures can be used to examine the subtleties of visuo-spatial deficits, several reaction time studies that have been conducted in patients with neglect and/or extinction are discussed. These studies stand as an example of how reaction time measures can contribute to both clinical and experimental neuropsychology.     

Using pictures to assess reinforcers in individuals with developmental disabilities

Tangible preference assessments were compared with pictorial preference assessments for 4 individuals with developmental disabilities. In the tangible assessment, on each trial two stimuli were selected and placed in front of the participant, who approached one. In the pictorial assessment, on each trial two line drawings were placed in front of the participant, who pointed to one. For both assessments, the percentage of opportunities each stimulus was approached or touched was calculated, and hierarchies of preferred items were developed. The two assessments yielded similar preference hierarchies for 3 of 4 participants. Reinforcer assessments using a simple free operant response confirmed that items identified as highly preferred on tangible and pictorial assessments functioned as reinforcers.     

Using different memory cutoffs to assess mild cognitive impairment.

OBJECTIVE: Although mild cognitive impairment (MCI) is characterized by performance on memory and other measures below expected normative values, neither a scientific rationale nor a consensus exists regarding which measures have the most use or the optimal cutoffs to use to establish impairment. METHODS: Different memory measures were administered to 80 normal community-dwelling subjects divided into two age groups. This provided conormed data on eight different memory indices by which to compare 23 nondemented clinically diagnosed patients with MCI who met all other criteria for Alzheimer disease (AD). RESULTS: On immediate memory for passages, delayed visual reproduction, object memory, and a measure sensitive to semantic interference, 70%-78% of patients with MCI were identified as impaired at 1.5 standard deviations or greater below expected levels. Conditional logistical regression for age-matched samples indicated that consideration of raw scores for these neuropsychologic tests in combination did not significantly change the odds of MCI diagnosis. When impairment relative to the total normal elderly sample was calculated based on one or more impairments at a 1.5 or greater cutoff, specificity fell below acceptable levels when more than three memory measures were considered. CONCLUSION: An array of widely used neuropsychologic measures demonstrated utility in distinguishing patients with MCI-AD from cognitively normal community-dwelling elders. The appropriateness of more or less stringent cutoffs was highly influenced by the number of measures considered. These findings have important implications regarding the choice of cut points for impairment used for the diagnosis of MCI in both research and clinical settings.     

Using neuropsychological and personality tests to assess the likelihood of patient employment

This study assessed the ability deficits and personality disturbances associated with three levels of employment in patients referred for neuropsychological testing. Highly significant group differences were found, with the unemployed group consistently showing greatest pathology on the tests, the full time employed group performing relatively normally, and the part time employed group earning intermediate scores. A discriminant function which used both neuropsychological and personality measures was found to discriminate unemployed from full time employed patients satisfactorily. Classification rates achieved by the function for validation and cross-validation samples support its clinical utility in identifying new patients who are at high risk for unemployment. It appears that psychological tests commonly used in neurological and psychiatric diagnosis can also help predict some aspects of patients' abilities to function in everyday life.     

Using partial directed coherence to describe neuronal ensemble interactions

This paper illustrates the use of the recently introduced method of partial directed coherence in approaching how interactions among neural structures change over short time spans that characterize well defined behavioral states. Central to the method is its use of multivariate time series modelling in conjunction with the concept of Granger causality. Simulated neural network models were used to illustrate the technique's power and limitations when dealing with neural spiking data. This was followed by the analysis of multi-unit activity data illustrating dynamical change in the interaction of thalamo-cortical structures in a behaving rat.     

Evaluation of measures used to assess quality of life after stroke

BACKGROUND AND PURPOSE: Assessment of quality of life (QOL) after stroke is becoming common with the recognition that evaluation of treatment should include quality as well as quantity of survival. This article will outline the main conceptual and methodological issues in QOL assessment, highlight advantages and disadvantages of measures used in stroke QOL research, and discuss some unresolved issues. SUMMARY OF REVIEW: We undertook a MEDLINE search using the keywords "stroke" and "quality of life" and reviewed 3 key texts on QOL measurement in stroke. Fifteen generic and 10 condition-specific measures used to assess QOL in stroke were identified and evaluated with the following criteria: reliability, validity, responsiveness, precision, acceptability, suitability for proxy respondents, mode of administration, and use of patient-centered approaches in development. Domains covered and level of comprehensiveness varied widely between generic and stroke-specific measures. No stroke-specific instruments used patient-centered approaches in their development. Four stroke-specific measures (Frenchay Activities Index, Niemi QOL scale, Ferrans and Powers QOL Index-Stroke Version, and Stroke-Adapted Sickness Impact Profile [SA-SIP30]) provided evidence of reliability and validity. CONCLUSIONS: The need remains for a patient-centered, psychometrically robust, stroke-specific QOL measure. Patients should be involved in each stage of instrument development. Caution is needed in the selection of an instrument to measure QOL after stroke. Although the Ferrans and Powers QOL Index-Stroke Version, Niemi QOL scale, SA-SIP30, and Sickness Impact Profile come closest to satisfying many of the criteria outlined in this article, the selection of any individual instrument depends on the specific goals and constraints of a particular study.     

Using conjoint analysis to assess depression treatment preferences among low-income Latinos

The authors examined the feasibility of conjoint analysis for measuring the depression treatment preferences of low-income, low-literacy Latino primary care patients. Forty-two patients with depression (58 percent of those eligible for the study) completed a survey about preferences for treatment and strategies to reduce barriers to care. They preferred combined counseling and medication to either approach alone and preferred individual over group treatment but did not show a significant preference for treatment setting. The odds of treatment acceptance were increased by the availability of telephone appointments, bus passes, and help with making appointments. Although further validation is required, conjoint analysis appears to be feasible for assessing preferences regarding depression treatment in this underserved population.     

New nomenclature and classification scheme for the neuronal ceroid lipofuscinoses

We provide a new classification for the neuronal ceroid lipofuscinoses (NCLs) that takes into account recent genetic and biochemical advances. This was originally developed by an international group with clinical, molecular genetic, biological, and morphologic interests, further revised by a panel of world experts in the NCLs, and is now updated in light of recent research findings. The aim is to provide young people, carers, and professionals with a diagnostic label that is informative, leads to effective clinical management of symptoms and in the future perhaps a cure, as well as aiding basic scientific and clinical research. We suggest that clinicians should aim to provide every child and family with detailed diagnostic information at clinical, biochemical, and genetic levels where possible, which the new classification allows in a gene-led hierarchical manner. The robustness and applicability of this updated new classification have been independently audited in the clinical setting using a series of patients previously diagnosed with NCL according to standard ultrastructural, biochemical, or genetic criteria.     

Using videos to assess preference for novel stimuli in children with autism

A primary effort of preference assessment research has been to develop strategies to identify potential reinforcers for educational, social, and behavioral programming for individuals with disabilities, including children with autism. However, little attention has been paid to the identification of preferred stimuli children with autism may not have previous experience with. The purpose of this study was to evaluate the extent to which a video-based preference assessment may accurately identify preference for novel stimuli. We compared the results of the video-based preference assessment with no access to novel stimuli to the results of a preference assessment conducted in a tangible format with access. We then conducted the same video-based preference assessment a second time to evaluate the extent to which exposure to stimuli affected assessment results. The results provide preliminary support that a video-based preference assessment may accurately identify preference for novel stimuli. Implications and future directions are discussed.     

Using analog baselines to assess the effects of naltrexone on self-injurious behavior

Naltrexone (NLTX), an opiate receptor antagonist, has been prescribed as a pharmacological intervention for the treatment of self-injurious behavior (SIB). Previous research has investigated NLTX’s effects in the absence of information about the role of environmental events related to SIB. This study extended previous analyses by administering NLTX on analog baselines using a double-blind, placebo-controlled reversal design. Pretreatment functional analysis results showed that the SIB of the two participants occurred in more that one assessment condition. For one participant NLTX produced slight reductions in SIB across baseline conditions. The second participant’s results showed that NLTX reduced head-slapping occurring during demand sessions, but had no apparent effect on head-banging occurring during alone and demand sessions. These outcomes suggest that NLTX may have function- and/or response-specific treatment effects. The potential utility of this model as a general method for assessing pharmacological interventions, as well as other implications and limitations, are discussed.     

How to assess the quality of psychotherapy outcome studies: A systematic review of quality assessment criteria

Objective: Although it is widely accepted that the quality of a study may affect its results, there is no agreed specific standard for assessing the quality of psychotherapy outcome studies. This study aims to review the existing variety of relevant quality assessment criteria. Method: We identified relevant quality measures based on a systematic literature search. To determine the specific relevance of the available quality criteria, we consulted experts in the field of psychotherapy outcome research. Results: Nineteen different measures providing 185 different quality criteria were included. Four measures specifically focused psychotherapy studies, none of these were designed for studies without a control group. Experts did judge 20% of the items as “absolutely indispensable.” Conclusions: Quality criteria that are exclusively related to the context of psychotherapy research are rare. Further research is required to examine the empirical relation between specific quality criteria and study results.     

The neuronal reactions of the frog midbrain to tones modulated in amplitude by pseudorandom noise

Impulse responses of single units located in the torus semicircularis of the immobilized lake frog (Rana ridibunda) to long-lasting characteristic frequency tones modulated by low-frequency pseudorandom noise were registered. Period histograms locked to the direct and inverted modulating waveform with duration of 512 ms were obtained for 32 units. The majority of the histograms revealed the rectification of the envelope waveform in the neural discharge patterns. So, the difference histograms were calculated which in some units represented the stimulus envelope waveform rather well. Other units strongly emphasized the envelope maxima in their responses. In many cases only a few maxima of the envelope were represented in the period histograms. There were neurons that retained peculiarities of their response in the wide range of the carrier intensities.     

Using neuronal extracellular vesicles and machine learning to predict cognitive deficits in HIV

Journal of NeuroVirology - Our objective was to predict HIV-associated neurocognitive disorder (HAND) in HIV-infected people using plasma neuronal extracellular vesicle (nEV) proteins, clinical...