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Biomedical subjects

D H Ingvar

Publications and source records attributed to D H Ingvar.

At least 19 recordsLinked to original sources
PubMed1992

[Surveying the brain-psyche connection. The frontal lobes control cerebral and mental "timing"].

Regional variations in the brain related to various forms of mental activity can be mapped with rapid isotope methods. Normal resting consciousness entails a high level of activity in large parts of the central nervous system (CNS)--particularly in the frontal lobes. Here the level of activity is reduced during loss of consciousness, intoxication, coma, and also during sleep. Specific functional landscapes can be recorded during perception of sensory stimuli, production of voluntary movements and speech, and in connexion with problem solving, mental imagery, thinking, etc. Effects of emotional stimuli can also be traced. These findings support the idea that a prerequisite for mental activity is a serial activity in multiple distributed networks. In this review, emphasis is laid upon the serial nature (the temporal organisation) of both neurophysiological and mental events. Much new evidence suggests that the serial nature of brain activity and of the cognition is governed by the frontal lobes.

Brain Mapping↗
PubMed1991

Aspects of stability of regional cerebral blood flow in chronic schizophrenia: an 18-year followup study.

Regional cerebral blood flow (rCBF) measurements and psychiatric ratings were performed on seven schizophrenic patients (mean age = 41.4 years) who had been examined 18 years previously in a study that used similar psychiatric ratings and a comparable rCBF technique. Neither the clinical symptomatology nor the rCBF level and distribution had changed appreciably between 1972 and 1990. The findings indicate that cerebral functional activity in chronic schizophrenia remains constant in spite of continuous neuroleptic medication.

Adult↗
PubMed1991

Disturbances of speech prosody following right hemisphere infarcts.

The ability to perceive and express emotional, as well as number of linguistic prosodic qualities of speech was tested in 20 Swedish-speaking patients with right-sided cortical, as well as purely subcortical brain infarcts, and in 18 normal controls. The infarcts were assessed by clinical neurological examination, and by CT, EEG, and measurements of regional cerebral blood flow (rCBF). In the patients the identification of emotional messages was disturbed, as well as the identification and production of several linguistic prosodic qualities. The study supports the claim that prosodic impairment could be linguistic in nature, and not secondary to affective disorder. The total degree of anatomical and functional disturbance of the right hemisphere played a role for both the ability to identify emotional messages and for identification of two of the linguistic prosodic qualities tested. However, it was not possible to find support for the hypothesis that the organization of prosody in the right hemisphere mirrors that of propositional speech on the left side.

Adult↗
PubMed1991

Volumes of chronic traumatic frontal brain lesions measured by MR imaging and CBF tomography.

The volumes (ml) of chronic traumatic frontal brain lesions were compared measured "morphologically" with MR imaging (T1 and T2 weighted images) and "functionally" with a tomographic rCBF technique (SPECT with 133Xe i.v.). The T1 volumes varied between 11 and 220 ml. The correlation between T1 and T2 volumes was 0.95, the T2 volumes being 33% larger than T1 volumes (p less than 0.001). The functional SPECT volumes were considerably larger (range 16-324 ml) than the MR volumes. The mean volume difference was 81% between T1 and SPECT images (p less than 0.001), and 35% between T2 and SPECT images (p less than 0.001). Correlations between the MR and SPECT volumes were also higher for T2 than T1 volumes. The volume difference is most likely explained by a functional decrease in regions around the lesion in which no morphologic change visible on MR images had taken place. MR and SPECT volume measurements were positively related to persistent lack of energy and personality changes, but only moderately related to duration of impaired consciousness and neuropsychologic outcome.

Adult↗
PubMed1990

The cerebellum participates in mental activity: tomographic measurements of regional cerebral blood flow.

Measurements in man of regional cerebral blood flow (rCBF) have demonstrated a number of cortical and subcortical events coupled to sensory stimulation or motor performance. It has also been shown that local activity changes take place in the cortex during 'pure' mental activity such as motor imagery (unaccompanied by sensory input or motor output). Thus, our group has previously shown that imagination of hand movements gives predominantly a frontal cortical rCBF activation while the corresponding hand movement activates the rolandic hand area mainly. In this paper we report tomographic rCBF measurements with a 133-Xenon SPECT technique during imagined tennis movements and silent counting. Both procedures gave rise to a significant cerebellar activation in addition to cortical rCBF changes. Apparently, the cerebellum may participate in pure mental activity. It possibly plays a role for the temporal organization of neuronal events related to cognition.

Adult↗
PubMed1990

Brain structures participating in mental simulation of motor behavior: a neuropsychological interpretation.

This paper reviews findings from cognitive and sport psychology, as well as from neurophysiology, concerning mental simulation of movement. A neuropsychological hypothesis is advanced to explain why mental practice can improve motor skill learning. Mental practice activates certain brain structures selectively as shown by measurements of regional cerebral blood flow. It appears likely that this activation improves the subsequent control of execution of movements. It is pointed out that the study of simulation of movements may not only be of value for sport training but also have importance for the rehabilitation of patients with motor disturbances following lesions of the central nervous system.

Brain↗
PubMed1990

Do single right hemisphere infarcts or transient ischaemic attacks result in aprosody?

The ability to perceive and express prosodic qualities of speech was tested in 21 patients with a single focal ischaemic disturbance of the right hemisphere, 14 patients having an infarct and 7 transient ischaemic attacks, and in 21 age-matched normal controls. All patients were predominantly right-handed. None showed signs of aphasia. Pure tone audiometry showed acceptable hearing for speech. The cerebral lesions were assessed by clinical neurologic examination, and by CT, EEG and measurement of regional cerebral blood flow (rCBF) using intravenous 133-xenon. The prosodia test included items testing: the ability to perceive accentual and emotional qualities of speech, and the ability to express and vary such qualities. The test did not discriminate between the patients and the controls, although some patients had large right-sided lesions. This negative finding indicates that aprosody in patients with brain lesions appears more difficult to detect than has previously been assumed. Highly sensitive tests are most likely required.

Adult↗
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↗
PubMed1979

EEG and cognitive impairment in presenile dementia.

EEG and psychometric findings were studied in a group of 57 patients consisting of 19 cases of Alzheimer's disease, 7 cases of Pick's disease, 24 cases of cerebrovascular dementia (CVD) and a group of 7 cases with dementia of various other etiology. The diagnoses have so far been confirmed by autopsy in 23 out of 57 cases. EEG was evaluated by means of visual inspection. Psychometric studies enabled a classification into 5 psychometric defect groups according to the degree of dementia. An overall good correlation was found between the degree of dementia and EEG abnormality. A significant correlation between the test socre and the EEG was found only for the vocabulary test and paired associates test. However, on the reaction time test, color word test, and Koh's block design test, large patient groups were untestable, and a highly significant correlation was found between non-testability and severely abnormal EEG. The Alzheimer and the CVD groups differed distinctly, most of the Alzheimer cases showing a severe or moderate degree of EEG abnormality and dementia, whereas in the CVD cases, the dementia was less pronounced and the EEG often normal or only slightly abnormal. Four out of seven cases of Pick's disease had a normal EEG, which distinguished them from the Alzheimer cases which had a comparable psychometric defect.

Adult↗