Showing papers by "University of Fribourg published in 1982"

Structural and functional definition of the motor cortex in the monkey (Macaca fascicularis)

Abstract: 1. The details of the organization of the motor cortex and its anterior and posterior border were investigated in three monkeys by a combination of techniques including intracortical microstimulation (i.c.m.s.), electrophysiological recording of cutaneous and muscle afferent inputs to single cortical neurones, and electrophysiological and anatomical identification of corticospinal neurones; in addition, data from these methods were related to cortical cytoarchitecture. 2. Almost 5000 individual cortical loci were tested with i.c.m.s. in the unanaesthetized monkeys. In this paper, we particularly consider the organization of the forelimb motor representation, and its relation to the representation of other parts of the body. I.c.m.s. thresholds of about 5 μA were common for evoking twitch movements and e.m.g. responses in distal forelimb and face, jaw and tongue muscles, but proximal forelimb, trunk and hind-limb movements also sometimes had such low thresholds. 3. The fingers were found to be represented nearest the central sulcus, with horseshoe-shaped bands of cortical tissue representing progressively more proximal muscles situated around this central `finger core'. 4. Cytoarchitectonically, the cortex having these low-threshold motor effects was characteristic of area 4. There was also a close fit between the extent of this `excitable cortex' and the extent of densely spaced corticospinal neurones identified electro-physiologically or with horseradish peroxidase labelling. In subsequent mapping of forelimb afferents to the cortex when the animal was deeply anaesthetized, low-threshold and short-latency responses to muscle nerve stimulation were rarely found in this `excitable cortex'. 5. The anterior border could be clearly established by i.c.m.s. and by the sharp boundary of corticospinal neurones. It was noted that the motor cortex extends rostrally beyond area 4 and its anterior border appears to reside in the posterior part of area 6aα (Vogt & Vogt, 1919) although it is difficult to establish the precise transition from area 4 to area 6. 6. Posteriorly, the `micro-excitable cortex' was found to be limited to regions cytoarchitectonically delineated as area 4 and did not include area 3a. On the other hand, low-threshold forelimb proprioceptive afferent inputs appeared restricted to area 3a neurones in the deeply anaesthetized animal. Corticospinal neurones were very dense in area 4, and there was a clear decrease in their occurrence in more caudal areas. However, scattered nests of corticospinal neurones were noted in areas 3a, 3b, 2, 1 and 5. It remains to be seen whether these scattered nests could be directly involved in motor control or whether they may modulate ascending somatosensory transmission, and whether they rely on sensory feed-back or inputs from other central areas for their spinal effects.

Microstimulation of the supplementary motor area (SMA) in the awake monkey

Abstract: The supplementary motor area of threeMacaca fascicularis was mapped using intracortical microstimulation (ICMS). Both forelimb and hindlimb movements were evoked using currents of 30 μA or less. However, thresholds for evoking movements were higher than those in the primary motor cortex. Proximal motor effects predominated, but distal joint movements were also elicited. Forelimb points were clustered in mesial cortex of area 6, anterior to the precentral hindlimb and tail region. Distal joint effects were located deep in the cortex, intermingled with proximal effects. Hindlimb responses which were less spatially localized, were found both ventral to the forelimb area, in the dorsal bank of the cingulate sulcus, and in mesial cortex, well anterior to area 4. No movements of facial muscles were elicited. Injections of HRP were made into the spinal cord at the cervical level in two animals and the lumbar level in the third one. An area of labelled cells was seen in mesial area 6 which corresponded closely to the region from which ICMS effects were elicited. No movements were evoked from the anterior portions of the fundal region of the cingulate sulcus which were also labelled.

The corticopontine system in the rat. II. The projection pattern.

Abstract: The projection from various cortical areas to the pontine nuclei (PN) of rats was investigated with anterograde tracing methods. As a general topological rule, a medial to lateral succession of the PN projection fields from the motor, somatosensory, and visual cortices was observed. Apart from the main "private" projections, each cortical area was found to send fibers also to disjunctive "extra-projection" territories which receive convergent inputs from two or more cortical areas. The sensorimotor and visual cortices provide the bulk of corticofugal fibers, but contributions from the following association areas were noted: frontal cortex, (dependent of the thalamic mediodorsal nucleus), rhinal sulcus region, and cingulate cortex.

The corticopontine system in the rat. I. Mapping of corticopontine neurons

Abstract: The expanse of cerebral cortex containing corticopontine neurons was explored in rats. The retrograde tracer horseradish peroxidase (HRP) was iontophoresed into subdivisions of the pontine nuclei (PN). The densest projection was seen to originate from somatosensory and motor areas. Visual areas also provide a major contigent of corticopontine neurons, whereas auditory areas appear to have only a minor projection. Consistent labeling of cells was also seen in the granular cingulate cortex, especially in the junction region of anterior and posterior cingulate cortex. This and a sparse projection from dorsal and posterior "insular" cortex (rhinal sulcus) have not been described in detail in previous studies.

Corticospinal neurones of the supplementary motor area of monkeys. A single unit study.

Abstract: The direct projection from the supplementary motor area (SMA) to the spinal cord was investigated in six monkeys by means of antidromic identification of single SMA neurones. The exploration concentrated on that portion of medial area 6 from which movements were found to be elicited by stimulation at intensities of less than 30 μA in an earlier study, but also included some of medial area 4. Of 315 identified corticofugal projection neurones, 234 were found to be localized within medial area 6; of these only one third (76 cells) were corticospinal cells and the remaining two thirds were neurones which projected to the brainstem. The conduction velocities of the descending projection neurones of the SMA were slow (modal value: 10 m/s). Corticospinal cells of the SMA were found up to 6 mm rostral to the boundary between areas 4 and 6. Corticospinal neurones activated antidromically from the cervical but not from the lumbar cord (‘cervicothoracic’ neurones) were concentrated in the mesial cortex; ‘lumbo-sacral’ neurones were found both in the dorsal cortex and the dorsal bank of the cingulate sulcus. However, there was considerable intermingling between the two types of projection neurones and there was no separation in the rostro-caudal direction. Similarly, projection neurones receiving orthodromic inputs from the somatotopical subdivisions of the precentral cortex were not segregated, but were intermingled in the entire rostro-caudal extent of the SMA. It is concluded that there is a clustering of corticospinal neurones in the SMA according to their most caudal segmental projection. However, no rostro-caudal differentiation into face, arm and leg areas was established. This observation is consistent with the results of a previous study in which corticospinal neurones in the SMA were labelled with anatomical tracers and efferent zones were investigated with intra-cortical microstimulation (Macpherson et al. 1982).

π-Orbital Interactions in Möbius-Type Molecules as Studied by Photoelectron Spectroscopy

Abstract: Some benzobarrelenes were studied by photoelectron (PE.) spectroscopy. The results can be interpreted by considering dominant through-space interaction of the π-molecular fragments in a Mobius-fashion, Some chemical features of the substrates are rationalized on the basis of these findings.

Changes in the non-structural carbohydrate content of cotton (Gossypium spp.) fibres at different stages of development

Abstract: The neutral sugars (glucose, fructose, and sucrose) and the sugar phosphates (glucose 6-phosphate, glucose 1-phosphate and fructose 6-phosphate) soluble in hot aqueous 80% methanol from the fibres of cotton — Gossypium arboreum L., G. barbadense L., and G. hirsutum L. — were determined at various stages of fibre development. In addition, the (1→3)-β-D-glucan content was measured and in the case of G. arboreum the rate of (1→3)-β-D-glucan and cellulose synthesis was determined with [14C]sucrose as the precursor. For each of the species a similar chronology was obtained for the changes in content of the various non-structural carbohydrates. At the early stages of secondary wall formation, glucose and fructose exhibited a maximum which was closely followed by a maximum in the (1→3)-β-D-glucan content and in the sugar phosphates. On the other hand, the sucrose content increased regularly until fibre maturity. The rates of synthesis of (1→3)-β-D-glucan and of cellulose were highest following the maximum in the (1→3)-β-D-glucan content, when the latter was being depleted.

New Photosensitizers of the Ruthenium‐Polypyridine Family for the Water Splitting Reaction

Abstract: The photophysical and electron transfer properties of the following Ru(II) complexes have been characterized: Ru(bpy)3-n (biq)2+n, Ru(bpy)2(Cl2-bpy)2+, Ru(Cl2-bpy)2+3, Ru(bpy)2(NO2-bpy)2+, Ru(NO2-bpy)2+3, Ru(bpy)2(opdi)2+, Ru(bpy)2(phedi)2+, where n = 1 to 3, bpy = 2,2′-bipyridine, biq = 2,2′-biquinoline, and opdi and phedi are o-quinodiimine ligands. The properties of these and other Ru-polypyridine type photosensitizers are discussed on the basis of the requirements needed to split water with solar energy in an efficient way. It is shown that the Ru(bpy)2(LL)2+ complexes, where LL is a polypyridine-type ligand which is easier to reduce than bpy, are expected to be more efficient photosensitizers than Ru(bpy)2+3.

A transcortical loop demonstrated by stimulation of low‐threshold muscle afferents in the awake monkey

Abstract: 1 The hypothesis that a transcortical loop can be activated by electrical stimulation of low-threshold muscle afferents was tested The effect of these afferents on the excitability of motoneurones was measured with the monosynaptic spinal reflex (H-reflex) 2 Four monkeys were trained to maintain a constant tonic activity in the soleus muscle so that the amplitude of evoked H-reflexes was constant The intensity of conditioning stimuli was just subthreshold for direct or reflex electromyographic responses The intensity of the test stimuli was adjusted to evoke an H-reflex of maximal amplitude The amplitude of the H-reflex was recorded for different intervals between conditioning and test stimuli (10-1000 msec) 3 The excitability curve obtained showed three components: (1) an early excitatory process, F1, at intervals of 10-20 msec, (2) a late excitatory process, F2, at intervals of 40-80 msec and (3) a short latency depression of about 400 msec duration, on which F1 and F2 were superimposed 4 F2 was selectively abolished during cooling of the contralateral motor cortex, after an irreversible lesion of the motor cortex, and after pyramidotomy; however, F1 and the inhibition remained unchanged 5 The conduction time from the tibial nerve to the somatosensory cortex (SI), the cortical delay between SI and motor cortex, and the conduction time from motor cortex to the soleus muscle were measured in an anaesthetized animal The sum of these values as an estimate of the transcortical loop time was 5 msec shorter than the latency of F2 6 It is concluded that a transcortical loop can be activated by electrical stimulation of low-threshold muscle afferents and, by analogy, also by mechanical perturbations applied during a motor task

High-Precision Muonic X-Ray-Measurement of the Rms Charge Radius of C-12 with a Crystal Spectrometer

Abstract: A precision measurement with the SIN bent-crystal spectrometer of the wavelength of the $2{p}_{\frac{3}{2}}\ensuremath{-}1{s}_{\frac{1}{2}}$ transition in muonic $^{12}\mathrm{C}$ yields $\ensuremath{\lambda}=16.473766(89)$ pm, the accuracy being an order of magnitude higher than that of earlier investigations. The rms charge radius of $^{12}\mathrm{C}$ is deduced as ${〈{\mathcal{r}}^{2}〉}^{\frac{1}{2}}=2.4832(18)$ fm, differing by 2.4 standard deviations from the most accurate electron-scattering results. Consequences of attributing this discrepancy to a $\ensuremath{\mu}\ensuremath{-}N$ interaction beyond QED are discussed.

A direct enzymatic lactose assay using cellobiose-(lactose-)dehydrogenase from sporotrichum thermophile

Abstract: Advantage was taken of the high specificity of the cellobiose dehydrogenase (EC 1.1. 99), produced by the fungusSporotrichum (Chrysosporium) thermophile during growth on cellulose, for cellobiose and lactose to devise a direct enzymatic procedure for the determination of lactose in milk and milk products. The assay is based on the colorimetric measurement of the reduction of dichlorophenol indophenol concomitant with the oxidation of lactose to lactobionic acid.

Photon‐Triggered Complex Formation: Radical Complexes of o‐Benzosemiquinone, Dopa, Dopamine and Adrenaline Formed by Electron‐Transfer Reaction from Excited Tris (2,2′‐bipyridyl)ruthenium (II)

Abstract: The pyrocatechol derivatives, dopamine (2), adrenaline (3) and L-dopa (4) form in their semiquinoid oxidation states complexes with several closed-shell metal ions like Zn2+, Cd2+ and Y3+. This complex formation can be triggered by visible light via a one-electron transfer reaction from the pyrocatechol derivative to (3CT)Ru(bpy), which is thereby reduced (Schemes 1 and 2), The quenching of the triplet charge-transfer state, (3CT)Ru(bpy) cannot be measured by conventional methods (Stern-Volmer plot), because the bimolecular electron-transfer rate is too slow (kq < 10−7 M−1 s−1). ESR. spectroscopy shows, however, clearly the paramagnetic reaction products. The concentration of these paramagnetic species is strongly enhanced by complex formation. The hindered rotation of the side chain in L-dopa and in its Y3+-complex is described within a two-jump model, which gives best agreement between calculated and measured spectra assuming an energy of 37 kJmol−1 for the rotational barrier.

Changing the Reader's Perspective1

Abstract: College students read a 748 word text either from the perspective of a potential homebuyer or from the perspective of a potential burglar. The text was an enlarged version of the one used in the Anderson and Pichert (1978) experiment. A free recall test was given either immediately or after a 20 minute delay, either from the original reading perspective or from the later introduced alternative perspective Recall from the shifted perspective was significantly lower than from the reading perspective. Yet, contrary to the hypothesis, which was based on the assumption of differential forgetting, this recall difference was not bigger in the delay condition than in the immediate condition. In comparing several interpretations most additional evidence was found in favor of the interpretation that suggests that the texťs own perspective overrode the special perspectives as instructed.

Linear solid state array detectors in Raman spectroscopy

Abstract: We demonstrate the rapid recording of liquid phase anti-Stokes vibrational and gas phase rotational spectra with an unintensified solid state detector. The ratio of the Stokes and anti-Stokes intensities of the 522 cm−1 vibration of toluene (Wilson 6a) does not appear to agree with theoretical predictions, in contrast to nearby lines. This possibility of a direct comparison accentuates the advantage of the simultaneous multichannel recording without drift. We also discuss the signal-to-noise performance of unintensified detectors and point out the limits where intensification is preferable.