The role of neurocritical care: a brief report on the survey results of neurosciences and critical care specialists.

Background: Neurocritical care is a new subspecialty field in medicine that intersects with many of the neuroscience and critical care specialties, and continues to evolve in its scope of practice and practitioners. The objective of this study was to assess the perceived need for and roles of neurocritical care intensivists and neurointensive care units among physicians involved with intensive care and the neurosciences.

Methods: An online survey of physicians practicing critical care medicine, and neurology was performed during the 2008 Leapfrog initiative to formally recognize neurocritical care training.

Use of 64-channel electroencephalography to study neural otolith-evoked responses.

Background: The vestibular evoked myogenic potential (VEMP) is a myogenic response that can be used clinically to evaluate the function of the saccule. However, to date, little is known about the thalamo-cortical representation of saccular activation. It is important to understand all aspects of the VEMP, as this test is currently used clinically in the evaluation of saccular function.

Multi-site phasic neural activity mediates the execution of an auditory continuous performance task: a PET and electrophysiological study.

Background And Purpose: We studied an auditory continuous performance task with positron emission tomography(PET) and EEG-derived current density reconstructions (CDRs) to define the spatial and temporal aspects of auditory attention.

Methods: The CDRs were employed to segregate responses to targets and non-targets at sites identified by PET. We then studied the time course of brain activity using statistical parametric mapping (SPM) of the CDR data.

Multi-site phasic neural activity mediates the execution of an auditory continuous performance task: a PET and electrophysiological study.

Background And Purpose: We studied an auditory continuous performance task with positron emission tomography (PET) and EEG-derived current density reconstructions (CDRs) to define the spatial and temporal aspects of auditory attention.

Methods: The CDRs were employed to segregate responses to targets and non-targets at sites identified by PET. We then studied the time course of brain activity using statistical parametric mapping (SPM) of the CDR data.

Neurodegenerative diseases: an overview of environmental risk factors.

The population of the United States is aging, and an ever-increasing number of Americans are afflicted with neurodegenerative diseases. Because the pathogenesis of many of these diseases remains unknown, we must consider that environmental factors may play a causal role. This review provides an overview of the epidemiologic evidence for environmental etiologies for neurodegenerative diseases such as Alzheimer disease, Parkinson disease, parkinsonian syndromes (multiple system atrophy and progressive supranuclear palsy), and amyotrophic lateral sclerosis.

Cognitive therapy for irritable bowel syndrome is associated with reduced limbic activity, GI symptoms, and anxiety.

This study sought to identify brain regions that underlie symptom changes in severely affected IBS patients undergoing cognitive therapy (CT). Five healthy controls and 6 Rome II diagnosed IBS patients underwent psychological testing followed by rectal balloon distention while brain neural activity was measured with O-15 water positron emission tomography (PET) before and after a brief regimen of CT. Pre-treatment resting state scans, without distention, were compared to post-treatment scans using statistical parametric mapping (SPM).

Mapping the 40-Hz auditory steady-state response using current density reconstructions.

We mapped the 40-Hz aSSR from nine normal subjects using PET-independent low-resolution electroencephalographic tomography (LORETA) as well as PET-weighted LORETA and minimum norm (MinNorm) current density reconstructions. In grand mean data, PET-independent LORETA identified seven sites with peaks in current density in right temporal lobe, right brainstem/cerebellum, right parietal lobe, left cerebellum/temporal lobe, and right frontal lobe. PET-weighted LORETA found six of the same sites as the PET-independent LORETA: the right brainstem source was eliminated and two right-frontal sources were added.

Blood ammonia levels and hepatic encephalopathy.

The importance of measurements of the blood ammonia concentration in the evaluation of patients with known or suspected hepatic encephalopathy (HE) is still disputed in spite of a general acknowledgment that ammonia is important in the pathogenesis of the disorder. Several recent studies have suggested that it is not necessary to utilize arterial blood when measuring ammonia in the blood. Venous blood or a computation of the partial pressure of ammonia gas in blood samples may suffice.

Human testing of pesticides: ethical and scientific considerations.

I reviewed ethical and scientific aspects of 6 human pesticide-dosing studies submitted to the Environmental Protection Agency (EPA) for consideration during the pesticide reregistration process. All had serious ethical or scientific deficiencies-or both-including unacceptable informed consent procedures, unmanaged financial conflicts of interest, inadequate statistical power, inappropriate test methods and endpoints, and distorted results. Given today's knowledge of the effects of pesticides, there is no assurance that any such study can be completely free of short-term risks, long-term risks, or both.

PET imaging of the 40 Hz auditory steady state response.

The auditory steady state response (aSSR) is an oscillatory electrical potential recorded from the scalp induced by amplitude-modulated (AM) or click/tone burst stimuli. Its clinical utility has been limited by uncertainty regarding the specific areas of the brain involved in its generation. To identify the generators of the aSSR, 15O-water PET imaging was used to locate the regions of the brain activated by a steady 1 kHz pure tone, the same tone amplitude modulated (AM) at 40 Hz and the specific regions of the brain responsive to the AM component of the stimulus relative to the continuous tone.

Functional imaging during covert auditory attention in multiple sclerosis.

Recent literature suggests that the brain in multiple sclerosis (MS) undergoes reorganization that subserves the performance of visual and motor tasks. We identified sites of cerebral activity in 16 MS patients while performing a covert attention (CA) task, presented in the auditory modality. Positron emission tomography (PET) revealed activation of rostral/dorsal anterior cingulate cortex (ACC) in normal subjects studied previously.

Mapping the neural systems that mediate the Paced Auditory Serial Addition Task (PASAT).

The paced auditory serial addition task (PASAT), in which subjects hear a number-string and add the two most-recently heard numbers, is a neuropsychological test sensitive to cerebral dysfunction. We mapped the brain regions activated by the PASAT using positron emission tomography (PET) and 15O-water to measure cerebral blood flow. We parsed the PASAT by mapping sites activated by immediate repetition of numbers and by repetition of the prior number after the presentation of the next number in the series.

Positron emission tomography in the study of hepatic encephalopathy.

Positron emission tomography (PET) is a powerful and versatile tool for the investigation of hepatic encephalopathy (HE). This nuclear medicine imaging technique produces quantitative images of the distribution of a radiopharmaceutical at one or more times after its administration. Thus, PET images can be used as data in mathematical models of physiologically important processes, including cerebral blood flow, an index of neural activity, or glucose and ammonia metabolism.