Biomedical subjects

Ian Law

Publications and source records attributed to Ian Law.

22 records · Page 2Linked to original sources

PubMed2002

[The working brain--how does it look like?].

Numerous brain functions, such as awareness of surroundings, control of movements, thoughts, and memory have always been a kind of mystery, which has provoked human curiosity and thus inspired research in many areas. The present paper gives an overview on imaging research of the human brain's functions. The historical progress is briefly reviewed with the emphasis on major Danish contributions. The major methods of mapping brain functions and their biological basis are mentioned. These methods are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). They are highly technological and generate enormous amounts of data. Thus, data analysis will per se be a research area in brain imaging. Finally, several examples of the authors' results on functional activation are dealt with. These examples aim to illustrate the research area and its contribution to our increased knowledge of the working brain.

Acoustic Stimulation↗

PubMed2002

Cortical deactivation induced by visual stimulation in human slow-wave sleep.

It has previously been demonstrated that sleeping and sedated young children respond with a paradoxical decrease in the blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal in the rostro-medial occipital visual cortex during visual stimulation. It is unresolved whether this negative BOLD response pattern is of developmental neurobiological origin particular to a given age or to a general effect of sleep or sedative drugs. To further elucidate this issue, we used fMRI and positron emission tomography (PET) to study the brain activation pattern during visual stimulation in spontaneously sleeping adult volunteers. In five sleeping volunteers fMRI studies confirmed a robust signal decrease during stimulation in the rostro-medial occipital cortex. A similar relative decrease at the same location was found during visual stimulation and polysomnographically verified slow-wave sleep in a separate group of six subjects using H(2)(15)O PET measures of the regional cerebral blood flow (rCBF). This decrease was more rostro-dorsal compared to the relative rCBF increase along the calcarine sulcus found during visual stimulation in the awake state. This study reconfirms the previously described paradoxical stimulation-correlated negative BOLD signal change in the rostro-medial occipital cortex, expanding this response mode to an age spectrum ranging from the newborn to the adult. Further, the use of complementary brain mapping techniques suggests that this decrease was secondary to a relative rCBF decrease. Possible mechanisms for the paradoxical response pattern during sleep include an active inhibition of the visual cortex or a disruption of an energy-consuming process.

Adult↗

PubMed2002

The caudate nucleus in obsessive-compulsive disorder. Reduced metabolism following treatment with paroxetine: a PET study.

Several neuroimaging studies of patients with OCD have pointed to basal ganglia and the frontal cortical regions being relevant for an understanding of the pathophysiology and therapy of OCD. In a search for the neural substrate underlying the therapeutic action of paroxetine in the therapy of OCD we measured regional glucose metabolism in a PET study of 20 OCD patients before and after at least 3 months of treatment. We used 18-fluoro-deoxyglucose PET-scanning to measure regional cerebral glucose metabolic rate (rCMRglc) in 20 non-depressed patients fulfilling DSM-IV criteria for OCD. Patients were studied before and after 12-20 wk of treatment with the serotonin re-uptake inhibitor paroxetine. Clinical assessment rating with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) was performed before the first and after the second study. The PET data was analysed regionally using statistical parametric mapping (SPM-96). A clinical improvement was indicated by a mean decrease of 55% in the Y-BOCS score. There was no difference in global cerebral metabolism before and after treatment whereas a post-treatment reduction in normalized rCMRglc was found in the right caudate nucleus. This finding also showed a significant positive correlation with symptom severity. Our results support hypotheses regarding a malfunction of the cortico-striato-thalamic system in the pathophysiology of OCD and particularly point to the caudate nucleus playing an important role for the therapeutic action of paroxetine in the treatment of OCD.

Adult↗

PubMed2002

Regional cerebral blood flow during light sleep--a H(2)(15)O-PET study.

This is the first report on the distribution of regional cerebral blood flow (rCBF) changes during stage-1 sleep or somnolence. Two hypotheses were tested: (A) that rCBF differed between the awake relaxed state and stage-1 sleep, (B) that hypnagogic hallucinations frequently experienced at sleep onset would be accompanied by measurable changes in rCBF using positron emission tomography (PET). Eight subjects were PET-scanned with (15)O-labeled water injection in three conditions: awake, stage-1 sleep with reportable experiences and stage-1 sleep without reportable experiences. Electroencephalography (EEG) was performed continuously during the experiment. Sleep interviews were performed after each scan. The EEG was scored blindly to determine sleep stage. The sleep interviews revealed a substantial increase in how unrealistic and how leaping the thoughts were during stage-1 sleep. During sleep there was a relative flow increase in the occipital lobes and a relative flow decrease in the bilateral cerebellum, the bilateral posterior parietal cortex, the right premotor cortex and the left thalamus. Hypnagogic experiences seemed not to be associated with any relative flow changes. The topography of the occipital activation during stage-1 sleep supports a hypothesis of this state being a state of imagery. The rCBF decreases in premotor cortex, thalamus and cerebellum could be indicative of a general decline in preparedness for goal directed action during stage-1 sleep. Stage-1 sleep seems more similar to other forms of altered awareness, for example, relaxation meditation than to deeper sleep stages. We are of the opinion that stage-1 sleep represents the dreaming state of wakefulness, while rapid eye movement (REM) sleep reflects the dreaming state of the unaware, sleeping brain.

Adult↗