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PubMed2004

Can electrophysiological assessments of brain function be useful to the intensive care physician in daily clinical practice?

Changes in electroencephalogram parameters and auditory event-related potentials, induced by interruption to propofol sedation in intensive care patients, provide a number of electrophysiological measures that can be used to assess neurological function accurately. Studies of electroencephalogram parameters suggest that power spectral estimation, as root mean square power, is more useful and precise than spectral edge frequency 95% in evaluating the functional integrity of the brain. When such parameters are used to evaluate neurological function, in particular the N100 and mismatch negativity components, a precise assessment of a patient's readiness to awaken from a pharmacologically induced coma (such as sedation) can be obtained. In terms of ease of use, however, it is more difficult to establish whether N100 or mismatch negativity is superior.

Electroencephalography↗
PubMed2004

Dichotic listening tests of functional brain asymmetry predict response to fluoxetine in depressed women and men.

Patients having a depressive disorder vary widely in their therapeutic responsiveness to a selective serotonin reuptake inhibitor (SSRI), but there are no clinical predictors of treatment outcome. Studies using dichotic listening, electrophysiologic and neuroimaging measures suggest that pretreatment differences among depressed patients in functional brain asymmetry are related to responsiveness to antidepressants. Two new studies replicate differences in dichotic listening asymmetry between fluoxetine responders and nonresponders, and demonstrate the importance of gender in this context. Right-handed outpatients who met DSM-IV criteria for major depression, dysthymia, or depression not otherwise specified were tested on dichotic fused-words and complex tones tests before completing 12 weeks of fluoxetine treatment. Perceptual asymmetry (PA) scores were compared for 75 patients (38 women) who responded to treatment and 39 patients (14 women) who were nonresponders. Normative data were also obtained for 101 healthy adults (61 women). Patients who responded to fluoxetine differed from nonresponders and healthy adults in favoring left- over right-hemisphere processing of dichotic stimuli, and this difference was dependent on gender and test. Heightened left-hemisphere advantage for dichotic words in responders was present among women but not men, whereas reduced right-hemisphere advantage for dichotic tones in responders was present among men but not women. Pretreatment PA was also predictive of change in depression severity following treatment. Responder vs nonresponder differences for verbal dichotic listening in women and nonverbal dichotic listening in men are discussed in terms of differences in cognitive function, hemispheric organization, and neurotransmitter function.

Adolescent↗
PubMed1978

Selective attention, cortical evoked responses, and brain function in human subjects: a critical review and theory.

A theoretical framework is proposed to account for the facts of selective attention in terms of cortical redundancy and cortical-subcortical interactions as measured by the Average Evoked Response and the background EEG. The recent research concerning AER correlations of selective attention is reviewed and found to be lacking in methodological coherence. This lack is found to contaminate existing theory regarding selective attention and brain function. An alternative approach is explored and its findings are found to yield the present theory.

Arousal↗
PubMed1994

The effects of sex steroids, and the X chromosome, on female brain function: a study of the neuropsychology of adult Turner syndrome.

Sex steroids and the X chromosome can independently affect cognitive abilities. Because subjects with Turner syndrome (TS) have gonadal aplasia, and various alterations in X chromosome structure and number, they provide a model to study the effects of sex steroids and of the X chromosome on human brain function. We used neuropsychological tests to study the cognitive abilities of 18 TS adults and 19 age/sex matched healthy controls. Nine TS subjects were mosaic for the 45,X karyotype, and 9 were non-mosaic 45,X (full TS). The TS group as a whole, compared to controls, had (i) significantly lower scores in tests of language and visual-spatial function, attention and memory, and (ii) a significantly greater discrepancy between verbal and performance scores. Mosaic TS subjects were intermediate between full TS and controls in some tests of verbal ability, but did not differ significantly from controls in others. Visuospatial ability was significantly lower than controls in both mosaic and full TS. Within the mosaic TS group, there was a significant negative correlation between visuospatial ability and % lymphocytes having a 45,X karyotype. Memory test scores were reduced independently of "X chromosome dosage" in all TS subjects. We conclude that in humans, the X chromosome is involved in development of both cerebral hemispheres, but moreso of the association neocortices. Also, sex steroids may modulate this effect--particularly in hippocampus.

Adolescent↗
PubMed2000

Luigi Luciani and the localization of brain functions: Italian research within the context of European neurophysiology at the end of the nineteenth century.

Luigi Luciani, the Italian physiologist who lived during the second half of the nineteenth century and the early years of the twentieth, is generally remembered for his studies on the cerebellum, the physiology of the heart, the respiratory system and on fasting. Less well known is the experimental research he carried out in the field of cerebral localization. It should however be pointed out that, as a result of his work in experimental neurophysiology between the years 1875 and 1885, Luciani was perfectly familiar with the latest findings on the relationship between brain and behavioral functions, but above all he was led by this work to develop an interesting model for the description of brain functions. He refined this model in a close dialectic relationship, of comparison and contrast, with the theories of the leading European neurophysiologists of his time - either those who favored a localizationistic explanation of the brain's functions or those who opposed this view. This paper gives a quick presentation of Luciani's experimental work on the functions of the brain as well as what he thought of the question of cerebral localization. His localizationistic model is compared - both in its general characteristics and in its specific details - with other models which had been proposed during the same years by the outstanding European physiologists of the day like Goltz, Ferrier, and Munk. Luciani's epistemological foundations, as well as his experimental methodology, are analyzed within the context of his wider theoretical ideas about how nervous and psychic activity were linked, with his ideas on physiology, and more in general in relation to his view of man's biological place in the rest of the living world. On the basis of this analysis, the state of the experimental work being done in Italy by Luciani is placed within the European context of neurophysiology in which Luciani was an outstanding figure.

Brain↗
PubMed1996

Brain Mediation of Obsessive-Compulsive Disorder Symptoms: Evidence From Functional Brain Imaging Studies in the Human and Nonhuman Primate.

Obsessive-compulsive disorder (OCD) has a long history of speculations concerning its cause. This article reviews human functional neuroimaging studies of OCD, then presents data from a study in the nonhuman primate that concerns the localization of brain systems that may mediate the expression of OCD symptoms. We use these lines of evidence to argue that increased "neural tone" through a section of the behaviorally disinhibiting "direct" basal ganglia pathway, relative to tone in the behaviorally inhibiting or moderating "indirect" basal ganglia system, may mediate the expression of OCD symptoms. The limbic orbital prefrontal cortex, the involvement of which is highly implicated in OCD, may have a greater influence on neural tone in the direct pathway than in the indirect, whereas more dorsal neocortical prefrontal regions may have the opposite effects on these two basal ganglia subsystems. Effective OCD treatments may obtain their results by preferentially decreasing neural tone through the direct relative to the indirect basal ganglia system.

Journal Article↗
PubMed2004

Brain functional magnetic resonance imaging of rectal pain and activation of endogenous inhibitory mechanisms in irritable bowel syndrome patient subgroups and healthy controls.

BACKGROUND AND AIMS: Many patients with irritable bowel syndrome (IBS) show intestinal hypersensitivity to distension and sensitisation after repeated intestinal distensions. Abnormalities in endogenous pain inhibitory mechanisms, such as diffuse noxious inhibitory controls (DNIC), may be implicated and were investigated during brain functional magnetic resonance imaging (fMRI). PATIENTS AND METHODS: fMRI was performed in 10 female patients with IBS (five constipated (IBS-C) and five with diarrhoea (IBS-D)) and 10 female healthy controls during rectal balloon distension alone or during activation of DNIC by painful heterotopic stimulation of the foot with ice water. Rectal pain was scored with and without heterotopic stimulation (0 = none, 10 = maximal). RESULTS: Heterotopic stimulation decreased median rectal pain scores significantly in healthy controls (-1.5 (interquartile range -2 to -1); p = 0.001) but not in IBS-C (-0.7 (-1 to 0.5)), IBS-D (-0.5 (-1.5 to 0.5)), or in all IBS patients (0 (-1.5 to 1.3)). Brain activation changes during heterotopic stimulation differed highly significantly between IBS-C, IBS-D, and controls. The main centres affected were the amygdala, anterior cingulate cortex, hippocampus, insula, periaqueductal gray, and prefrontal cortex, which form part of the matrix controlling emotional, autonomic, and descending modulatory responses to pain. CONCLUSIONS: IBS-C and IBS-D appear to have differing abnormal endogenous pain inhibitory mechanisms, involving DNIC and other supraspinal modulatory pathways.

Adult↗
PubMed1992

Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging.

We report that visual stimulation produces an easily detectable (5-20%) transient increase in the intensity of water proton magnetic resonance signals in human primary visual cortex in gradient echo images at 4-T magnetic-field strength. The observed changes predominantly occur in areas containing gray matter and can be used to produce high-spatial-resolution functional brain maps in humans. Reducing the image-acquisition echo time from 40 msec to 8 msec reduces the amplitude of the fractional signal change, suggesting that it is produced by a change in apparent transverse relaxation time T*2. The amplitude, sign, and echo-time dependence of these intrinsic signal changes are consistent with the idea that neural activation increases regional cerebral blood flow and concomitantly increases venous-blood oxygenation.

Brain Chemistry↗
PubMed1998

Long-term effects of boxing and judo-choking techniques on brain function.

Regional cerebral blood flow (rCBF) was measured by 133-xenon inhalation in 24 amateur and 20 professional boxers, and in 10 judoka. Results were compared with those from age- and sex-matched healthy controls. Eighteen boxers (9 amateurs and 9 professionals) and all judoka also underwent electroencephalography (EEG). Mean rCBF values did not differ between either amateur boxers orjudoka and controls, whereas in professional boxers rCBF was significantly (p<.001) reduced in the whole brain, especially in the frontocentral regions. Healthy subjects, judoka, and amateur boxers showed a similar distribution of global CBF (gCBF, the mean of 32 probes) values, although 12.5% of amateurs had a significantly lower gCBF than controls. Among professional boxers, 25% showed a significantly low gCBF value; in the remaining 75%, gCBF was below the mean value of controls but did not reach statistical significance. Regional hypoperfusion, mainly in the frontocentral regions of both sides, was found in 35% of professional and in 29% of amateur boxers. A correlation between gCBF values and number of official matches was not found in boxers. EEG was normal in all judoka and amateur boxers, but it was abnormal in 3 professionals. This study shows the relevance of the neurophysiological assessment of athletes engaged in violent sports which can cause brain impairment. In fact, while professional boxers may show brain functional impairment in comparison to normal subjects, judoka do not. The lack of correlation between CBF values in boxers and the number of official matches points to the difficulty of taking into account variables, such as the number and the severity of matches during training.

Adult↗
PubMed2002

Functional brain imaging and pharmacotherapy in trichotillomania. Single photon emission computed tomography before and after treatment with the selective serotonin reuptake inhibitor citalopram.

The neurobiology and pharmacotherapy of trichotillomania has received increasing attention in recent years. Parallels have been drawn between findings in this disorder and those in obsessive-compulsive disorder (OCD). To date, however, there has been little work on the effect of a pharmacotherapeutic intervention on functional brain imaging in trichotillomania. Female patients (n = 10) with DMS-IV diagnostic criteria for trichotillomania were subjected to single photon emission computed tomography (SPECT) with technetium-99m hexamethylpropylene amine oxime (Tc-99m HMPAO) before and after 12 weeks of pharmacotherapy with the selective serotonin reuptake inhibitor (SSRI), citalopram. Pharmacotherapy led to significantly reduced activity in inferior-posterior and other frontal regions. Correlates of hair-pulling symptoms with regional brain activity differed before and after pharmacotherapy. These data are to some extent consistent with work suggesting that trichotillomania, like OCD, is mediated by corticostriatal circuits. Pharmacotherapeutic response to SSRIs in trichotillomania may not be as robust as in OCD. Further research is necessary to determine the neurobiological underpinnings of these differences.

Adult↗