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At least 55 records · Page 3Linked to original sources
PubMed1992

Magnetic resonance imaging mapping of brain function. Human visual cortex.

Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology of MRI brain mapping and results from the investigation of the functional organization and frequency response of human primary visual cortex (V1) are presented.

Brain Mapping↗
PubMed1976

Two biological rhythms of perception distinguishing between intact and relatively damaged brain function in man.

A simple test of perception, the Critical Flicker Fusion threshold (CFF) was given successively for 20 mins. to 69 healthy subjects aged 7-63 and to 53 comparable neuropsychiatric patients. The latter could be divided into a functionally sick group and a group with brain damage. Auto-correlation analysis revealed significant sine-wave cycles of amplitude and ultradian frequency for the CFF mean scores and the CFF "Scatter* scores. Both cycles of recurrence showed frequencies which distinguished significantly between the total healthy subjects and the patients. Further analysis showed no difference between controls and emotionally sick patients (i.e. those with sociopathy, schizophrenia and manic depressive psychosis) but there was a highly significant difference between these three groups and patients with relatively damaged C.N.S. (i.e. those with mental deficiency, organic brain syndrome and organic dementia). Even among the control group a progressive increase in frequency of these perceptual cycles occurred with advancing age. These CFF results point to the existence of a cycle of perceptual acuity and another of vigilance in the organism. Both appear to relate to the neural integrity of the C.N.S.

Adolescent↗
PubMed1992

Changes in brain functional connectivity in Alzheimer-type and multi-infarct dementia.

Clinical and neuropathological evaluation of elderly subjects with dementia has traditionally concentrated upon the focal distribution of brain disease, ignoring changes in the complex connections that link brain areas and that are crucial for cognition. We examined subjects with the two most common forms of dementia in the elderly (dementia of the Alzheimer type or DAT, and multi-infarct dementia or MID); and used electroencephalographic (EEG) coherence to examine the effects of these illnesses on the functional connections between brain areas. We studied coherence between brain areas known to be linked by two different types of connections: (i) dense narrow bands of long corticocortical fibres; (ii) broad complex networks of corticocortical and corticosubcortical fibres. Areas that were linked by dense narrow bands of long corticocortical fibres showed greatly diminished coherence in subjects with DAT; among MID subjects, this coherence was not significantly affected. Areas that were linked by broad connective networks showed the largest decreases in coherence among MID subjects. These findings are consistent with neuropathological evidence that Alzheimer's disease is a neocortical 'disconnection syndrome' in which there is a loss of structural and functional integrity of long corticocortical tracts. The findings further suggest that the vascular disease of MID most prominently affects broad fibre networks that may be more vulnerable to diffuse subcortical vascular damage. A ratio of coherence from complex corticocortical-corticosubcortical networks divided by coherence from long corticocortical tracts correctly classified 76% of subjects into DAT and MID categories. Overall, these results indicate that EEG coherence detects basic pathophysiological differences between subjects with DAT and MID, and that these differences may be clinically useful.

Aged↗
PubMed1976

Brain function in epilepsy: midbrain, medullary, and cerebellar interaction with the rostral forebrain.

Against the background previous findings in epileptic patients, in whom electroencephalographic recordings were obtained from numerous deep and surface brain sites during seizures, rhesus monkeys with electrodes implanted into specific brain sites were used to demonstrate anatomical connections by evoked potential techniques and to serve as models of experimental epilepsy. In the animals, many monosynaptic connections were revealed between forebrain sites consistently involved in seizures in patients and more caudal brain sites subserving functions of sensory perception, eye movement, synaptic chemical transmission, and motor coordination. Further, the participation of these interrelated sites during seizures was demonstrated. The findings provide an anatomical-physiological explanation for many of the clinical phenomena observed in epileptic patients and a rationale for the use of cerebellar stimulation as a treatment.

Animals↗