Crossroads Newsletter May 2006

The latent state-trait structure of resting EEG asymmetry: replication and extension
Psychophysiology. 2005 Nov;42(6):740-52.

Since the first published report on a relation between frontal EEG asymmetry and emotional experience about 100 empirical papers have studied the association between frontal EEG asymmetry and affective states, motivational tendencies, affective dispositions, and psychopathology In the majority of this work, the EEG was recorded in a resting state, and the resulting measure of frontal EEG asymmetry was considered as an individual differences variable, that is, a biological trait. However, obtaining stable trait measures from EEG recordings in resting situations may pose a delicate methodological problem Several studies could consistently demonstrate that resting asymmetry measures of healthy subjects show retest correlations in the .50s or .60s for time intervals between 2 and 6 weeks for a variety of EEG reference schemes.

Recent research on brain asymmetry suggested that resting electroencephalographic (EEG) asymmetry represents a superimposition of a trait-like asymmetry with state-dependent fluctuations.

The present study tested this hypothesis and additionally examined individual differences in state changes. A 61-channel EEG was collected from 59 participants in a resting state on three occasions of measurement.

An analysis of latent state-trait models suggested that between 40% and 50% of the variance of anterior asymmetry measures was due to individual differences on a latent trait and approximately the same portion of the variance was due to occasion-specific fluctuations.

A further analysis of true intraindividual change models indicated that there were large individual differences in intraindividual change over time. These data replicate previous findings and substantiate that resting asymmetry has trait and state properties.
(full study)

Memory Dysfunction
New England Journal of Medicine 2005

Memory function is vulnerable to a variety of pathologic processes including neurodegenerative diseases, strokes, tumors, head trauma, hypoxia, cardiac surgery, malnutrition, attention-deficit disorder, depression, anxiety, the side effects of medication, and normal aging.

Memory loss is often the most disabling feature of many disorders, impairing the normal daily activities of the patients and profoundly affecting their families. Some perceptions about memory, such as the concepts of “short-term” and “longterm,” have given way to a more refined understanding and improved classification systems.

These changes result from neuropsychological studies of patients with focal brain lesions, neuroanatomical studies in humans and animals, experiments in animals, positron-emission tomography, functional magnetic resonance imaging, and eventrelated potentials.

Memory is now understood to be a collection of mental abilities that depend on several systems within the brain. In this article, we will discuss the following four memory systems that are of clinical relevance: episodic memory, semantic memory, procedural memory, and working memory.

We will summarize the current understanding of memory from the point of view of functional neuroimaging and studies of patients with brain insults, which should aid clinicians in the diagnosis and treatment of the memory disorders of their patients. As therapeutic interventions for memory disorders become available, clinicians will increasingly need to be aware of the various memory systems in the brain.
(complete article)

Fast Food and Asthma

Randall Neustaedter O.M.D.

A New Zealand study examined the association between fast food and asthma in children. Researchers discovered that the more fast-food consumed (hamburgers and deep-fried foods) the higher the incidence of asthmatic signs and symptoms.

Those researchers found that the amount of fast-foods consumed corresponded to the degree of asthma as determined by the change in peak flow measurements before and after exercise. The correlation between asthma and foods was true for hamburgers, fried foods (fish and chips), and fizzy drinks (soda). The higher the dose of these foods, the more asthma symptoms occurred.

The authors note that several other studies have noted similar associations. For example, fast food was also a risk factor for wheezing among children in Saudi Arabia, and deep-fried food consumption doubled the risk of asthma among teenagers in Taiwan.
(more on the story)

Frontal electroencephalogram activation asymmetry, emotional intelligence, and externalizing behaviors in 10-year-old children

Child Psychiatry Hum Dev. 2006 Spring;36(3):311-28.

The purpose of the present study was to examine the relations among resting frontal brain electrical activity (EEG) (hypothesized to reflect a predisposition to positive versusnegative affect and ability to regulate emotions), emotional intelligence, and externalizing behaviors in a sample of non-clinical 10-year-old children.

We found that boys had significantly lower emotional intelligence than girls, and low emotional intelligence was associated with significantly more externalizing behaviors (i.e., aggression and delinquency), replicating previous work.

We also found that children with higher reported externalizing behaviors exhibited significantly greater relative right frontal EEG activity at rest compared with children with little to no externalizing behavioral problems.

There was, however, no relation between emotional intelligence and the pattern of resting frontal EEG activity.

Thus, emotional intelligence and the pattern of frontal EEG activation at rest are independent predictors of externalizing behaviors in children.

Findings also suggest that individual differences in emotional intelligence may not be based on differences in levels of emotional regulation or the generation of positive affect as reflected in frontal EEG asymmetries, but rather other social and cognitive competencies required for adaptive behavior.
(source)

Gaze fixation and the neural circuitry of face processing in autism
Nature Neuroscience 8, 519 - 526 (2005)

Diminished gaze fixation is one of the core features of autism and has been proposed to be associated with abnormalities in the neural circuitry of affect.

We tested this hypothesis in two separate studies using eye tracking while measuring functional brain activity during facial discrimination tasks in individuals with autism and in typically developing individuals.

Activation in the fusiform gyrus and amygdala was strongly and positively correlated with the time spent fixating the eyes in the autistic group in both studies, suggesting that diminished gaze fixation may account for the fusiform hypoactivation to faces commonly reported in autism.

In addition, variation in eye fixation within autistic individuals was strongly and positively associated with amygdala activation across both studies, suggesting a heightened emotional response associated with gaze fixation in autism.
(source)

Electrophysiological correlates of cortico-subcortical interaction: a cross-frequency spectral EEG analysis.

Clin Neurophysiol. 2006 Feb;117(2):381-7. Epub 2005 Dec 20.
Related Articles, Links

Schutter DJ, Leitner C, Kenemans JL, van Honk J.

Department of Psychonomics, Affective Neuroscience Section, Helmholtz Research Institute, Utrecht University, Heidelberglaan 2, 3584CS Utrecht, The Netherlands. d.schutter@fss.uu.nl

OBJECTIVE: Several studies have provided evidence for the notion that the coupling between slow and fast frequency in the EEG spectrum indicates cortico-subcortical cross-talk (CSC-ct).

In addition, findings for increased limbic activation due to reduced cortical inhibition have recently been acquired. To get further insights into these mechanisms, the current study investigated whether CSC-ct would decrease as a function of increased slow (SW) or fast wave (FW) activity.

METHODS: Resting state EEG recordings were obtained from 46 healthy, right-handed participants. CSC-ct was quantified by computing cross-frequency correlations between the power in the slow and fast frequency range. CSC-ct was compared between groups with relatively low and high SW activity and groups with relatively low and high FW activity.

RESULTS: Relatively reduced SW, but not FW activity was associated with a significant coupling between slow and fast frequency EEG. Furthermore, relatively enhanced resting state SW activity was paralleled by slow and fast frequency EEG decoupling.

CONCLUSIONS: These findings are in line with the notion that increased subcortical drive can go accompanied by reduced CSC-ct.

SIGNIFICANCE: Cross-frequency EEG analyses might provide a unique approach to obtain novel insights into cortico-subcortical interactions in relation to affective and cognitive behavior.

(source)

Neurofeedback treatment of epilepsy:from basic ratinale to practical application

Egner, T. , Sterman, B.

The treatment of epilepsy through operant conditioning of the sensorimotor rhythm electroencephalogram has a 35-year history. Neurophysiological studies have shown that this phasic oscillation reflects an inhibitory state of the sensorimotor system. Operant learning of sensory motor rhythm production results in an up regulation of excitation thresholds with in the thalamocortical sensory and motor circuitry, which in turn is associated with reduced susceptibility to seizures. The clinical benefits derived from the neurofeedback training protocol, particularly inn patients that are not responsive to pharmacotherapy, have been documented in many independent laboratories. Recent advances in computer technology have resulted in the availability of relatively inexpensive high-quality equipment for the application of neurofeedback therapy, thus presenting a viable and promising treatment alternative.
(complete article)

Newer Antidepressants Linked to Serious Lung Disorder in Newborns
Health Canada

OTTAWA, CANADA -- March 10, 2006 -- Health Canada is advising women who are taking antidepressants known as Selective Serotonin Re-uptake Inhibitors (SSRI) and who are pregnant or intend to become pregnant to discuss the situation with their doctor due to potential risks to the baby.

SSRIs and other newer antidepressants prescribed for the treatment of depression include the following drugs: Wellbutrin (bupropion), Celexa (citalopram), Cipralex (escitalopram), Prozac (fluoxetine), Luvox (fluvoxamine), Remeron (mirtazapine), Paxil (paroxetine), Zoloft (sertraline) and Effexor (venlafaxine), and Zyban (bupropion) for smoking cessation.

A study published recently in the New England Journal of Medicine suggests that use of SSRIs during the second half of pregnancy may be associated with a condition called persistent pulmonary hypertension of the newborn. Newborns with this rare but life-threatening condition do not receive enough oxygen in the blood and require intensive-care treatment to survive. According to the study, babies born with this condition were six times more likely than healthy babies to have been exposed to SSRIs.
(more on the story)