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To ascertain the critical thresholds of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) for cerebral circulation and brain function, the extra- and intracranial haemodynamics and electrical brain responses were evaluated noninvasively with Doppler ultrasonography and multimodality evoked potentials (MEP's) in 50 patients with severe head injury. Both extra- and intracranial blood flow velocities changed monotonically depending on the changes in ICP and CPP. They were decreased when ICP increased to 20-30 mmHg and when CPP decreased to 40-50 mmHg. The changes in elasticity index of the pulse wave of the common carotid artery was proportional to those of blood flow velocities. The frequency and degree of abnormalities of MEP's were proportionally increased with the rise of ICP and reduction of CPP. When ICP increased to higher than 31 mmHg, MEP's were classified as moderately or severely abnormal in more than 76% of the recordings. These results indicate that noninvasive study by use of Doppler ultrasonography and MEP's can provide valuable information on critical brain ischaemia and brain dysfunction in patients with acute intracranial hypertension.
Computer analysis of the electroencephalogram (CEEG) in psychotic children before and after pharmacotherapy, normal children of schizophrenic mothers, and matched normal children of normal parents indicated significant intergroup differences. The psychotic children had more slow, as well as very fast, EEG waves. With drug therapy the EEG showed a partial "normalization," as fast EEG activity decreased. The EEG and auditory evoked potential of children of schizophrenic mothers were strikingly similar to those of psychotic children and schizophrenic adults, with significant decreases of the average EEG amplitude and the evoked potential latencies. Psychotic children were distinctly differentiated from the normal children by discriminant function analysis of the EEG and EP. Quantitative analysis of brain functions in the mentally ill can help determine the neurophysiological correlates of behavior, a more scientific diagnostic classification, prognosis, and selection of therapy.
Neural organization of linguistic competence in the light of brain functional asymmetry was studied in patients after unilateral electroconvulsive therapy. We have gathered further evidence that the cerebral hemispheres play essentially different roles: the right hemisphere operates largely with extralinguistic reality and is responsible for the ideational (intentional) level, initiating the process of speech production. It relates sign to its referent; its syntax is the word order. The left hemisphere interrelates signs; it refines and ultimately completes the process of speech production. The right hemispheric linguistic competence demonstrates the most universal linguistic abilities, whereas left hemispheric competence probably reveals the features of national languages.
Hydranencephaly is a severe condition of brain characterized by the almost complete absence of the cerebral hemispheres with the thalamus, cerebellum and brainstem being preserved. This paper reports hydranencephaly in a 3-month-old boy. Cranial magnetic resonance imaging (MRI) revealed the condition and an auditory evoked potential study which was performed in order to investigate residual brain function. They showed normal auditory brainstem function but no appearance of other auditory evoked potentials originating from the higher brain.
OBJECTIVE: To observe effect of electroacupuncture at Shenmen (HT 7) and Neiguan (PC 6) on brain functional imaging. METHODS: The technique of functional magnetic resonance imaging was used to observe the activated state in different brain regions caused by electroacupuncture. RESULTS: The frontal lobe was activated by electroacupuncture at Neiguan (PC 6) and the temporal lobe by Shenmen (HT 7). CONCLUSION: Electroacupuncture at different acupoints can activate different brain regions, which provides objective basis for treatment of intellectual impairment by electroacupuncture at Neiguan (PC 6) and Shenmen (HT 7).
Variation and selection within neural populations play key roles in the development and function of the brain. In this article, I review a population theory of the nervous system aimed at understanding the significance of these processes. Since its original formulation in 1978, considerable evidence has accumulated to support this theory of neuronal group selection. Extensive neural modeling based on the theory has provided useful insights into several outstanding neurobiological problems including those concerned with integration of cortical function, sensorimotor control, and perceptually based behavior.
Sleep deprivation can affect the waking electroencephalogram (EEG) that may reflect functional organization of the brain. We examined the effect of total sleep deprivation (TSD) on functional organization between different cortical areas from the waking EEG. Waking EEG data were recorded from 18 healthy male volunteers with eyes closed after 8-h night's sleep and after 24 h of TSD. The averaged cross mutual information (A-CMI) after 24 h of TSD were compared to before TSD. 24 h of TSD yielded the decreased A-CMIs in the inter-hemispheric C3-F4, C3-F8, and C3-C4 pairs: therefore, the electrodes that contribute to pairs with significant decrease of A-CMI were C3, F4, F8, and C4. The decreased A-CMIs between C3 and right frontal and central brain areas after 24 h of TSD may reflect the changes of cortico-cortical functional organization by homeostatic process during TSD. Our results of the frontal-area-related A-CMI decreases may support that the frontal brain regions are related to the homeostatic deterioration of brain function due to TSD.
In this work we use a computer simulation to estimate the magnitude of improvement in the signal-to-noise ratio of PET functional brain mapping studies as a function of partition coefficient and permeability surface product for O-14, F-17, and O-15 labeled flow tracers. A model for signal-to-noise ratio is derived from the Kety model for inert diffusible blood flow tracers. The results of the simulation suggest that moderate increases in partition coefficient and permeability surface product compared with water would lead to an increase in signal-to-noise ratio of a factor of about 3.
BACKGROUND AND PURPOSE: Independent component analysis (ICA), unlike other methods for processing functional MR (fMR) imaging data, requires no a priori assumptions about the hemodynamic response to the task. The purpose of this study was to analyze the temporal characteristics and the spatial mapping of the independent components identified by ICA when the subject performs a finger-tapping task. METHODS: Ten healthy subjects performed variations of the finger-tapping task conventionally used to map the sensorimotor cortex. The scan data were processed with ICA, and the temporal configuration of the components and their spatial localizations were studied. The locations with activation were tabulated and compared with locations known to be involved in the organization of motor functions in the brain. RESULTS: Components were identified that correlated to varying degrees with the conventional boxcar reference function. One or more of these components mapped to the sensorimotor cortex, supplementary motor area (SMA), putamen, and thalamus. By means of ICA components, sensorimotor cortex, supplementary motor area, and superior cerebellar activation were identified bilaterally in 100% of the subjects; thalamus activation was contralateral to the active hand in 80%; and putamen activation was contralateral to the active hand in 60%. CONCLUSION: ICA processing of multislice fMR imaging data acquired during finger tapping identifies the sensorimotor cortex, SMA, cerebellar, putamen, and thalamic activation. ICA appears to be a method that provides information on both the temporal and spatial characteristics of activation. Multiple task-related components can be identified by ICA, and specific activation maps can be derived from each separate component.
One of the problems in carotid surgery is the intra-operative detection of brain ischemia. None of the methods applied so far have been successful. Experience has shown that the results were unsatisfactory. Experimental studies have detected a strong correlation between regional cerebral blood flow and somatosensory evoked potentials. At the Surgical Clinic of the University of Cologne, 60 patients had continuous intraoperative monitoring of somatosensory evoked responses during carotid endarterectomy. Our previous experiences suggest that monitoring of somatosensory evoked responses during carotid endarterectomy provides a suitable method for the registration of brain function. Furthermore it is possible to pinpoint the causes of ischemia and to immediately begin treatment based on the causes of ischemia.
One future direction for cognitive development research involves a closer integration with our knowledge about the developing brain. I present a framework for analyzing and interpreting postnatal functional brain development in human infants. Three specific hypotheses contribute to this framework, within which a variety of phenomena associated with the neural basis of perception and cognition in normal and abnormal development can be characterized.
The effects of acute intravenous (i.v.) cocaine (COC) on several complex brain functions were studied in rhesus monkeys at 1.5, 3 and 10-11 years of age. Subjects performed several operant tasks (for food) that were used to model learning, short-term memory, color and position discrimination, and motivation, and disruption of performance of these tasks was used to quantitate drug effect. Drug effects were age dependent: The youngest subjects were 3 to 10 times less sensitive than the oldest. Presuming the observed behavioral effects of cocaine were caused primarily via its interaction with dopamine (DA) systems, changes in sensitivity to its effects with age are likely a reflection of the functional status of the DA system. These data, along with preliminary data on levels of DA transporters, suggest that the age-related differences in sensitivity to cocaine lie in, 'downstream' from, the dopamine receptor.
Presently, there is no intervention that can be used that preserves brain function in hypoxic-ischemic encephalopathy. This review covers the interventional strategies that are available to the health care worker at present and suggests a different approach to this frustrating problem. The proposal is to use clinically available interventions and combine them into an effective intervention strategy. The merits of each intervention is discussed.
This paper presents an overview of a new method for the non-invasive measurement of brain function, the event-related optical signal (EROS). This technique is based on measures of the optical properties of cortical brain tissue, which change while the tissue is active. These changes are likely to be due to changes in light scattering, and are very rapid and localized, being related to phenomena occurring within or around the neuronal membrane. EROS, therefore yields images of cortical activity that combine spatial specificity (i.e. they can be related to patches of tissue less than a cubic centimeter in size) with temporal resolution (i.e. they depict the time course of the neural activity in the cortical areas under measurement). A limitation of this technique is its reduced penetration into the head (less than 3-5 cm). EROS appears to be a suitable technique for studying the time course of activity in selected cortical areas, and for providing a bridge between hemodynamic and electrophysiological imaging methods.
Progestins, estrogens, androgens, and corticosteroids are capable of modifying brain functions and behaviors by mechanisms that involve the classic genomic model for steroid action. However, experimental evidence indicates that some responses to steroid hormones use non-classical, non-genomic mechanisms. This paper reviews the evidence that steroids can bind to receptors in the plasma membrane, activate cell signaling pathways, and regulate responses on a time scale of seconds or a few minutes. The existence of these alternative regulatory pathways for steroid hormones should make endocrinologists and neurobiologists change how they think about steroid hormones. It is no longer valid to assume that minute-to-minute changes in steroid concentrations are not regulating biologically important, short-term responses, or that the only steroids with biological functions are the ones that bind with high affinity to intracellular steroid receptors.
MRI has advanced to being one of the major tools for the assessment of brain function. This review article examines the basic principles that underpin these measurements. The main emphasis is on the characteristics and detection of blood oxygen level dependent (BOLD) contrast. In the first part of the article the relationship between BOLD, blood flow, blood oxygen, and the rate of metabolic consumption of oxygen is described. The four contrast mechanisms that contribute to the BOLD signal change, namely extravascular static and dynamic dephasing, intravascular T2-like changes, and the intravascular frequency offset effect are described in terms of their spatial localization and relative contributions to the BOLD signal. The current model of changes in blood flow being an indirect consequence of synaptic input to a region is presented. The second section of the article deals with the imaging characteristics of BOLD in terms of the attainable spatial resolution and linear system characteristics. In the third section, practical BOLD imaging is examined for choice of pulse sequence, resolution, echo time (TE), repetition time (TR), and flip angle. The final section touches on other MRI approaches that are relevant to cognitive neuroimaging, in particular the measurement of blood flow, blood volume, resting state fluctuations in the BOLD signal, and measures of connectivity using diffusion tensor imaging and fiber-tracking.