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R B Malmo

Publications and source records attributed to R B Malmo.

17 recordsLinked to original sources
PubMed2000

On electromyographic (EMG) gradients and movement-related brain activity: significance for motor control, cognitive functions, and certain psychopathologies.

Electromyographic (EMG) voltage that rises continuously during motor performance or mental activity and falls precipitately at the end is known as an EMG gradient. Our review is based on 55 studies of EMG gradients, which were published during the period 1937-1994. The extremely wide diversity of situations yielding EMG gradients suggests the possibility that these gradients may be universal accompaniments of organized goal-directed behavioral sequences, overt and covert. Motor tasks and cognitive tasks (without any requirements for motor output) were found to have this in common: they both produced EMG gradients. EMG gradients were not observed during simple, repetitive exercises. On the efferent side, we propose a dual model for the production of EMG gradients, which is based on empirical findings. This model is discussed in relation to current views on central and peripheral neural control of muscle contractions, and on the electrical properties of extrafusal and intrafusal muscle fibers, with particular reference to surface electromyography. The complex relations between EMG gradient steepness and mental effort seemed well represented by the dual model, which was also useful in the interpretation of certain EMG gradients that were found in patients with anxiety disorders, tension-type headaches, and auditory hallucinations, respectively. On the afferent side, drawing on data from human and animal studies, we consider the evidence for movement-related brain activity generated by proprioceptive input, in relation to different types of feedback to the central nervous system during tasks that produce EMG gradients. On electromyographic (EMG) gradients and movement-related brain activity: significance for motor control, cognitive functions, and certain psychopathologies.

Brain↗
PubMed1988

Effects of intracerebroventricular angiotensin II and olfactory stimuli on multiple unit activity in preoptic and anterior hypothalamic areas: medial-lateral comparison.

Under urethane anesthesia multiple unit activity (MUA) recordings were taken from medial and lateral preoptic and anterior hypothalamic sites in 21 rats during multiple dose intracerebroventricular (i.vt.) injections of angiotensin II (AII), using artificial CSF as control. Olfactory stimuli were also presented. Whilst lateral sites on average were significantly less responsive to AII than were medial sites, some of the former were very responsive. None of the 14 lateral sites that yielded an MUA response to AII failed to yield an MUA response to olfactory stimulation. On the other hand, 11 of 12 medial sites that yielded an MUA response to AII failed to yield an MUA response to olfactory stimulation. On the basis of these data it is suggested that the medial and lateral regions of the basal forebrain serve different functions, the former more related to internal sensing and the latter more related to integration of internal and external sensing. The findings are discussed in relation to the dual olfactory system and to theories of motivation.

Angiotensin II↗
PubMed1986

Individual consistency and modifiability of lapping rates in rats: a new look at the variance--invariance question.

Lapping rates were recorded from water-deprived rats over 3-week periods when they were young adults and again, 9.4 months later, when they were middle-aged. Test-retest correlation coefficients of 0.95, that were obtained for lapping rates recorded as long as a week apart, reflect extremely consistent frequency control, which is in line with the proposal by Wiesenfeld et al. (1977) that licking/lapping is under control of a hypoglossal oscillator. These high test-retest correlations were obtained both in young adulthood and again, later in middle-aged rats. However, correlations across the 9.4 months were close to zero, although mean water lapping rate did not change. Our data indicate that the effects of aging on lap rate were of two kinds. (1) Producing randomized shifts in the lapping rate of individual rats over long periods, with conservation of the stable mean rate, and (2) accentuating the tendency for reduction in the lapping rate for the last 50 laps compared with that of the first 50. It also appeared that the relevance of the fluid being lapped, in relation to water deprivation, was another important variable in determining the lapping rate. These and other data are considered in relation to the variance-invariance issue.

Aging↗
PubMed1983

Experiments on the neuropsychology of thirst.

We report the results of a series of experiments whose main objectives are: (a) the identification of neural receptors for thirst; and (b) other neural structures of critical importance for thirst and drinking behavior. We have used results from hypertonic challenges during acute unit and multiple-unit recording experiments to identify responsive brain areas for behavioral study in chronic experiments. Results include the following. Single cells in the lateral preoptic area (LPOA) responded to injections of hypertonic saline into the carotid artery in a dose-related manner. Multiple unit activity (MUA) reactions were invariably facilitatory to challenge, and were much greater in the LPOA than in the medial preoptic area (MPOA). In unit and MUA recording we found extremely osmosensitive sites in the dorsal midbrain. Comparing the effects of NaCl vs sucrose as challenges via the intracarotid artery we found that LPOA MUA responses to sucrose were at least as strong and latencies as short as those to NaCl. These results support osmoreceptor theory, as revised by Epstein and his co-workers, and they are opposed to Andersson's sodium receptor theory. Hypertonic NaCl and sucrose solutions (but not artificial CSF controls) injected into the lateral ventricle were effective in producing strong MUA reactions, which typically were inhibition followed by facilitation. These and other findings support the following conclusions. (a) The LPOA appears to be a vital part of the neural mechanism for thirst and it is a probable site of osmoreceptors. (b) In addition, the LPOA seems to be a receiving area connected with putative periventricular neural receptors. (c) Intraventricular (i.v.t.) angiotensin II seems to be a much stronger dipsogen than hypertonic NaCl i.v.t., which in higher concentrations elicited stereotyped running.

Angiotensin II↗
PubMed1983

Cardiovascular and respiratory responses to electrical stimulation of the midbrain in the rat.

In descending through the midbrains of rats with stimulation electrodes, we have observed some remarkable reversals of pressor and depressor autonomic effects as the electrode was moved from one locus to another. Autonomic effects of stimulating in the midbrain areas that we studied are of special interest because stimulations in some of these midbrain loci have pain-relieving effects (Hosobuchi et al., 1977, 1979; Mayer et al., 1971; Soper, 1976). Our observations of cardiac arrest are of particular concern because of the use that is being made of midbrain electrical stimulation to relieve pain in human patients.

Animals↗
PubMed1982

On movement-related forebrain and midbrain multiple unit activity in rats. II. Some constraints on movement.

In 18 rats multiple unit activity was recorded simultaneously from ventral forebrain, dorsal midbrain, and other areas, with continuous monitoring by sensitive head movement and body movement recorders, along with careful observations or ongoing behaviors. In the preceding article of this series, we reported significant covariations between neural activity and motoric activity in forebrain and midbrain areas in the rat. In the present article, we pointed out exceptions to this general finding. The data that we have presented in this paper refute the principle of invariably tight coupling between motoric and midbrain reticular activity as stated by Schwartzbaum (1975). Our data are clearly opposed to his view that movement patterns set the range within which midbrain neural activity varies, and opposed to his conclusion that midbrain activity conforms to the immediate properties of behavior apart from conditions giving rise to the behavior. In reviewing our data, the probable role of midbrain mechanisms in preparatory phases of movement was discussed.

Acoustic Stimulation↗
PubMed1982

Multiple unit activity recorded longitudinally in rats from pubescence to old age.

Longitudinal multiple unit activity (MUA) recordings of excellent quality over time periods as long as 26 months are described. The validity of the method was demonstrated by showing persistence of specific and idiosyncratic MUA responses to controlled sensory stimulation over these long time periods. This longitudinal MUA method was used to study level of localization neuronal activity as a function of aging. In agreement with deoxyglucose data from Sokoloff's laboratory, we found significant age-related declines in inferior and superior colliculi. In addition, our results showed the advantage of a longitudinal method over a cross-sectional one in following progressive changes into old age. The further declines in midbrain MUA level (though not in forebrain level) from middle age to old age that we observed were highly significant. The deoxyglucose method, on the other hand, had failed to show this kind of progression in those midbrain sites, probably because of a survival effect, a common sampling artifact in cross-sectional studies of aging.

Acoustic Stimulation↗
PubMed1981

Responses of lateral preoptic neurons and behavioral reactions to angiotensin II and hypertonic NaCl and sucrose administered into the rat cerebral ventricle.

In 18 acutely prepared rats and in 3 chronically implanted rats, multiple-unit responses of lateral preoptic area (LPOA) neurons to angiotensin II (A II) and hypertonic NaCl and sucrose injected into the lateral ventricle were recorded. In addition, behavioral reactions were observed in the chronically prepared rats. Results showed that i.vt. injections of hypertonic solutions or A II affect neural activity in the LPOA, indicating that the LPOA has connections with periventricular structures that are sensitive to these substances. Experiments with chronically implanted animals demonstrated the relevance of i.vt. injections for drinking. Some of the same solutions that produced changes in LPOA MUA in the acute series (or in anesthetized chronically implanted rats) also elicited drinking. A II was a more effective dipsogen than hypertonic NaCl, and in the strongest concentration used, NaCl produced stereotyped running, reduced head movement during quiescence, and caused a progressive fall in baseline MUA. Drinking was elicited by intermediate concentrations of i.vt. NaCl. Implications for the neuropsychology of thirst are discussed.

Angiotensin II↗
PubMed1979

Responses of lateral preoptic neurons in the rat to hypertonic sucrose and NaCl.

Multiple-unit recordings were taken from the lateral preoptic region during a series of hypertonic and isotonic NaCl and sucrose intracarotid injections. Subjects were 11 hooded rats (8 males and 3 ovariectomized females) under urethane anesthesia. The data showed that under favorable cannulation conditions there were strong multiple-unit responses to hypertonic sucrose injections, and that under these conditions NaCl injections were not significantly more effective than sucrose injections. The possible bearing of these findings on hypotheses concerning central receptors for thirst is discussed.

Animals↗
PubMed1977

Movement-related forebrain and midbrain multiple unit activity in rats.

In 16 rats multiple unit activity was recorded simultaneously from ventral forebrain and dorsal midbrain areas, with continuous monitoring by sensitive head movement and body movement recorders, along with careful observations of ongoing behaviors. Both forebrain and midbrain multiple unit activity were significantly correlated with head and body movements: recordings from both brain areas showed significant declines corresponding to decline in recordings head and body movement. The declines in midbrain multiple unit activity were significantly greater than those in forebrain multiple unit activity. The significant correlation of forebrain multiple unit activity with continuous recordings of bodily activity is, to the best of our knowledge, a new finding. The correlations between brain activity and bodily activity found in these experiments indicate the importance of monitoring brain recordings of awake animals with sensitive recordings of head and body movement. In addition, these findings represent a further demonstration of the need to analyze the operation of the brain in terms of its motor output.

Action Potentials↗
PubMed1976

Osmosensitive neurons in the rat's dorsal midbrain.

In experiment 1, multiple unit recordings were taken simultaneously from lateral preoptic and dorsal midbrain areas during a series of intracarotid hypertonic and isotonic NaCl injections. Subjects were 15 hooded rats (11 males and 4 ovariectomized females) under urethane anesthesia. Results showed that the neuronal reactions to a series of hypertonic NaCl injections (0.30 M, 0.45 M, 0.60 M and 0.75 M) were at least as strong in the dorsal midbrain as in the lateral preoptic area. Strength of neuronal reaction correlated with osmolarity of the NaCl solution injected. Control isotonic NaCl injections were ineffective, and the (monitored) force of injection was found not to affect the results. In experiment 2 with 15 hooded rats (9 males and 6 ovariectomized females), and two male Wistar rats under urethane anesthesia, recording from dorsal midbrain units were made during intracarotid injections of hypertonic and isotonic NaCl solutions. In addition, other sensory stimulations, including tail pinches, were presented. Of the 52 units studied, 39 cells (75%) reacted to injections of hypertonic NaCl, but not the isotonic (control) solution (Normosol-R). Again, strength of neuronal reaction correlated with osmolarity of the NaCl solution injected, and force of injections was found not to influence results. Eleven cells reacted to hypertonic NaCl injections but not to tail pinch. This and other evidence indicated that certain dorsal midbrain cells were specifically osmosensitive, and not merely showing general 'arousal' reactions to the injections. These results indicate that, for the rat, the osmosensitive zone extends into the midbrain. The functional significance of these findings is discussed.

Animals↗
PubMed1975

Rod and cone sensitivity in destriate monkeys.

Photopic and scotopic spectral sensitivity of rhesus monkeys was determined before and after complete removal of the striate cortex. The monkeys were required to choose between a white and a series of monochromatic stimuli distributed throughout the visible spectrum. A modified method of limits was used to determine the psychophysical point of subjective equality at which the colored and white lights were perceived as being equally bright. The preoperative results indicated that the method of testing was appropriate to determine spectral sensitivity since the curves obtained compared favorably to the theoretical sensitivity curves. Postoperatively, the scotopic sensitivity curve was normal whereas the photopic curve was completely displaced towards the scotopic curve. The results as indicating that cone information is processed by the geniculo-striate visual system whereas the extra-striate structures receive their input mainly from the rod receptors of the retina.

Adult↗
PubMed1975

Osmosensitive neurons in the rat's preoptic area: medial-lateral comparison.

For the first time, brain-recording data were brought to bear directly on the question of a critical osmosensitive zone in the lateral preoptic area as specifically delimited in the rat by Blass and Epstein, and in the rabbit by Peck and Novin. Our data clearly showed that this critical zone in the lateral preoptic area of the rat contains cells that are osmosensitive. Simultaneous recording from cell populations (a) inside the critical zone and (b) in a zone medial to it showed that the net acceleratory response to challenge for the former was much greater than it was for the latter. These findings constitute new evidence for the critical importance of the lateral preoptic area in cellular dehydration thirst.

Animals↗