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Biomedical subjects

D H Ingvar

Publications and source records attributed to D H Ingvar.

At least 37 records · Page 2Linked to original sources
PubMed1990

Brain regions involved in voluntary movements as revealed by radioisotopic mapping of CBF or CMR-glucose changes.

Mapping of cortical and subcortical grey matter active during voluntary movements by means of measurements of local increases of CBF or CMR-Glucose is reviewed. Most of the studies concern observations in man during hand movements using the intracarotid Xenon-133 injection technique, an approach that only allows to image the cortex of the hemisphere on one side (the injected side) of the brain. The results show that simple static or repetitive movements mainly activate the contralateral primary hand area (MI and SI); complex preprogrammed or spontaneous purposeful movements the supplementary motor area SMA on both sides increase in CBF/CMR-glucose and even internally ("mentally") going through the trained movements, causes such changes; complex purposeful movements also activate the premotor cortex, a response that is bilateral with greatest response contralaterally. Studies in patients with movement disorders are scant, but with the ongoing improvements in technique activation studies in selected patients may become an important tool in clinical neurophysiology/neuropsychology.

Animals↗
PubMed1989

Cerebral blood flow and metabolism in sleep.

A review is presented of the electrical activity of the brain and its global and regional blood flow and metabolism in the different stages of sleep and in wakefulness in animals and humans. During slow-wave sleep (SWS), the blood flow and metabolism of the brain decrease slightly below the level of wakefulness. During rapid eye movement the activity of the brain increases above that of SWS and sometimes above that of wakefulness. Some studies suggest that both at sleep onset and at arousal the brain stem-cerebellar complex (BSC) may be activated before the cortex and the right hemisphere before the left. Variation of hemispheric dominance seems to be a phenomenon of both wakefulness and sleep.

Brain↗
PubMed1988

rCBF landscapes during motor performance and motor ideation of a graphic gesture.

The regional cerebral blood flow (rCBF) distribution was measured by 133xenon inhalation using a gamma camera in 18 right-handed volunteers, 6 subjects performing a graphic task (writing numbers in letters) with the right hand, 6 subjects imagining the same task, and 6 subjects were assessed during two rest periods to determine the reproducibility of the technique. The mean rCBF increased between 10% and 25% (P less than 0.01) during both motor performance and motor ideation. However, there were regional differences. While motor performance activated mainly the rolandic regions bilaterally, motor ideation gave prefrontal and premotor rCBF augmentations. In both situations there was significant bilateral increase in regions corresponding to the cerebellum.

Adult↗
PubMed1988

SPECT measurements with 99mTc-HM-PAO in focal epilepsy.

The ability of SPECT measurements with [99mTc]-HM-PAO (Ceretec) to find the location of the epileptic focus was studied in patients under consideration for neurosurgical treatment for therapy-resistant focal epilepsy. The location of low [99mTc]-HM-PAO uptake regions found at interictal measurements, and of high [99mTc]-HM-PAO uptake regions found at ictal measurements, was compared to the findings of extensive ictal and interictal EEG examinations, and to the results of CT and MRT. While EEG revealed focal epileptic activity in all of the 14 patients, SPECT showed regional abnormalities in 13 (93%). CT and MRT showed abnormal findings in 30%.

Adolescent↗
PubMed1988

Remote cerebral effects on EEG in high-energy missile trauma.

Preliminary observations show that under certain circumstances high-energy missile trauma to soft tissue causes a transient depression of the EEG. Similar effects on the central nervous system elicited by the pressure and shock waves might be the cause of the acute behavioural and mental blockage reported in man by nonfatal wounds from missiles of this type. The mechanism behind the effects observed is not yet known, nor can the absence of EEG effects in some animals be explained at present. Further studies of the remote cerebral effects of high-energy missile trauma should be carried out.

Animals↗
PubMed1987

Changes of regional cerebral blood flow measured simultaneously in the right and left hemisphere during automatic speech and humming.

Regional cerebral blood flow (rCBF) was measured simultaneously in both hemispheres during automatic speech and during humming. During automatic speech rCBF increased slightly but significantly more in the right hemisphere. No side difference was found during humming. At rest and in both test situations the rCBF was highest bifrontally. Regional analysis revealed multiple regions of significantly increased rCBF in both hemispheres during both speech and humming. Some of these regions coincided with known speech centres in the left hemisphere. Others, especially on the right, did not. It is concluded that vocal activation during both speech and humming requires a collaboration of the two hemispheres in various functional patterns.

Adult↗
PubMed1986

Carbon dioxide narcosis: influence of short-term high concentration carbon dioxide inhalation on EEG and cortical evoked responses in the rat.

The effects of 1 min exposure to 80% CO2 inhalation was studied in rats under light general anaesthesia with N2O. It was found that 80% CO2 gave a rapid slowing of the EEG as well as a rapid decrease of the amplitude of cortical somatosensory evoked potentials. Only minor influences upon the blood pressure and heart rate were seen. The changes were found to be transient and most of the EEG effects had disappeared about 2-3 min following the end of the CO2 exposure. The findings are related to current procedures for preslaughter anaesthesia in swine using 80% CO2. The present experiments show that 80% CO2 rapidly induces an interruption of afferent sensory transmission to the cortex as well as slowing of the EEG. Both findings indicate that 80% CO2 is an effective agent for inducing adequate anaesthesia for slaughter procedures. However, the transient nature of the CO2 effects upon the central nervous system revealed here has to be taken into account to optimize the slaughter house procedures.

Anesthesia, Inhalation↗
PubMed1985

"Memory of the future": an essay on the temporal organization of conscious awareness.

The classical tripartite concept of time divided into past/present/future components, has been applied to the analysis of the functional cerebral substrate of conscious awareness. Attempts have been made to localize and to separate the neuronal machineries which are responsible for the experience of a past, a present, and a future. One's experience of a past is obviously related to one's memories. Memory mechanisms (in the conventional sense) have a well known functional relation to superficial and deep parts of the temporal lobe. Some such mechanisms presumably have a more widespread distribution. The experience of a present or a "Now-situation" is mediated by the sensory input. This input also exerts a role for conscious awareness of an inner Now-situation, independent of current afferent impulses, as shown by numerous observations on sensory deprivation. The main discussion is devoted to the experience of a future. Evidence is summarized that the frontal/prefrontal cortex handles the temporal organization of behaviour and cognition, and that the same structures house the action programs or plans for future behaviour and cognition. As these programs can be retained and recalled, they might be termed "memories of the future". It is suggested that they form the basis for anticipation and expectation as well as for the short and long-term planning of a goal-directed behavioural and cognitive repertoire. This repertoire for future use is based upon experiences of past events and the awareness of a Now-situation, and it is continuously rehearsed and optimized. Lesions or dysfunctions of the frontal/prefrontal cortex give rise to states characterized by a "loss of future", with consequent indifference, inactivity, lack of ambition, and inability to foresee the consequences of one's future behaviour. It is concluded that the prefrontal cortex is responsible for the temporal organization of behaviour and cognition due to its seemingly specific capacity to handle serial information and to extract causal relations from such information. Possibly the serial action programs which are stored in the prefrontal cortex are also used by the brain as templates for extracting meaningful (serial) information from the enormous, mainly non-serial, random, sensory noise to which the brain is constantly exposed. Without a "memory of the future" such an extraction cannot take place.

Awareness↗
PubMed1984

Metabolic and behavioral consequences of lidocaine-kindled seizures.

Daily administration of lidocaine results in progressive increases in frequency and duration of convulsions in response to a dose of drug which was previously subconvulsive--a pharmacological kindling phenomenon. The effects of such lidocaine-kindling on local cerebral glucose utilization were determined by the 2-[14C]deoxyglucose method. Lidocaine-treated animals, in the absence of convulsions, exhibited decreased glucose utilization in most brain structures compared to saline-treated animals and showed no increase in aggressive behavior. In animals displaying lidocaine-kindled convulsions there were marked increases in glucose utilization in either the hippocampus and amygdala or in perirhinal cortical areas during the seizure administration; these animals also displayed long-lasting increases in irritable behavior. Seizure duration was positively correlated with the rate of glucose utilization in the hippocampus, amygdala and septum, but inversely correlated in several non-limbic areas. These data suggest that lidocaine-kindled seizures are highly localized to limbic and perirhinal structures and are associated with important behavioral consequences.

Aggression↗
PubMed1984

Epilepsy related to cerebral blood flow and metabolism.

In an epileptic focus there is a three-fold increase of the regional cerebral metabolism and blood flow. This has been shown with the 133 Xenon technique and with positron emission tomography. Such studies suggest that, in temporal lobe epilepsy, the pathways from the deep temporal structures to the frontal lobes do not function normally. The temporal 'gate' to the frontal lobes may be closed. This may explain symptoms of psychopathology in this common type of focal epilepsy.

Brain↗
PubMed1983

Serial aspects of language and speech related to prefrontal cortical activity. A selective review.

Language and speech depend basically upon complex serial (i.e., sequential or temporally structured) neuronal events (action programs) which enable a perception of symbols and a production of meaningful words and sentences with adequate syntax and semantic content. There is evidence that action programs for speech and language, like other serial programs of the CNS, are handled specifically by the prefrontal cortex. Measurements of regional cerebral blood flow (rCBF) and metabolic rate (rCMR) support this view. Word perception, speech, reading etc. activate circumscribed areas in different patterns both in postcentral (afferent) and in precentral/prefrontal (efferent) regions of the hemisphere cortices. Most of these patterns show important symmetrical features. The classical speech cortices of Wernicke and Broca are not unconditionally activated in rCBF measurements during speech reception and production, respectively. Upper prefrontal activations are recorded during e.g. serial word production and reading, and during word perception lower prefrontal activations are seen in addition to postcentral increases of rCBF. A selective activation of prefrontal regions only, takes place during serial information processing related to cognition and ideation, including inner silent speech. In patients with cerebrovascular disorders, organic dementia, Parkinson's disease, and schizophrenia, various types of prefrontal (and other) rCBF and rCMR abnormalities may be seen. In such states different forms of "aseriality" or "dysseriality" (i.e., a defective serial programming) of speech can be recognized, which include non-fluent forms of aphasia of the Broca type, the hesitant, reduced and sometimes aprosodic speech in organic dementia and Parkinson's disease, as well as the peculiar semantic and motor disturbances of speech in schizophrenia.

Adult↗
PubMed1982

Cerebral glucography with positron tomography. Use in normal subjects and in patients with schizophrenia.

Local cerebral uptake of deoxyglucose labeled with fluorine 18 was measured by positron-emission tomography in eight patients with schizophrenia who were not receiving medication and in six age-matched normal volunteers. Subjects sat in an acoustically treated, darkened room with eyes closed after injection of 3 to 5 mCi of deoxyglucose 18F. After uptake, seven to eight horizontal brain scans parallel to the canthomeatal line were done. Scans were treated digitally, with a 2.3-cm strip peeled off each slice and ratios to whole-slice activity computed. Patients with schizophrenia showed lower ratios in the frontal cortex, indicating relatively lower glucose use than normal control subjects; this was consistent with previously reported studies of regional cerebral blood flow. Patients also showed diminished ratios for a 2.3-cm square that was positioned over central gray-matter areas on the left but not on the right side. These findings are preliminary; issues of control of mental activity, brain structure identification, and biologic and anatomic heterogeneity of schizophrenia remain to be explored.

Adolescent↗
PubMed1982

Reduction of blood flow in cerebral white matter in alcoholics related to hepatic function.

Fifty alcoholics with mean age of 45 years were examined with the intra-arterial 133Xenon method for measurement of regional cerebral blood flow and with EEG. The results were related to liver function tests. Reduced white matter blood flow correlated strongly with abnormal liver function tests. The highest correlation was with S-ASAT. Only weak correlations were found between gray matter flow, EEG and the liver function tests. It is suggested that the relationship between white matter flow reduction and liver function may be caused by the intensity of drinking prior to admission and possibly mediated by some still unknown hepatic mechanism or a direct effect of alcohol.

Adult↗
PubMed1982

EEG abnormalities in chronic alcoholism related to age.

EEG was studied in 50 chronic alcoholics (age 45 +/- 10 years). All EEGs were classified visually. In addition, a manual analysis from a fronto-central (F3-C3 of F4-C4) lead and a temporo-occipital (T5-O1 or T6-O2) lead was done in 42 cases to obtain the mean frequency of the 6-12 Hz band. The visual classification correlated well with the frequency analysis in the anterior (rs = -0.57, P less than 0.001) and in the posterior (rs = 0.61, P less than 0.001) leads and there was a high positive correlation between the frontal and occipital lead (r = 0.88, P less than 0.001). Half of the records were abnormal. There was a significantly higher proportion of abnormal EEGs in the youngest and oldest patient groups compared with the remainder. EEG-abnormality was significantly related to early start of abuse (before 25 years, P less than 0.05). The findings suggest that alcohol abuse in the teens or early twenties is accompanied by a considerably greater risk of brain damage than alcoholism beginning after 25. However, an alternative explanation, i.e. that the EEG abnormality may represent cerebral dysfunction predisposing to alcoholism is not excluded.

Adult↗