The postnatal development of thalamocortical projections from the pulvinar in the cat

Summary The postnatal development of thalamocortical projections from the pulvinar to an association cortex of the cat, the crown of the middle suprasylvian gyrus, was studied by using both HRP and evoked field potentials. From birth onward, the pulvinar sends dense fibres to this cortical area, but the cortical laminar distribution of the afferents was found to change markedly with aging. An orthograde HRP study showed that at birth and up to 2 weeks of age, the terminals are distributed mainly in layer I, whereas in adult cats and kittens older than 1 month, the terminals are found largely in and around layer IV and only sparsely in layer I. After HRP injections exclusively into layer I of the crown, numerous thalamic neurones were retrogradely labelled in both the ventroanterior-ventrolateral complex (VA-VL) and the pulvinar in 5-day-old kittens, but in the VAVL alone in 2-month-old kittens. In agreement with these anatomical findings, stimulation of the pulvinar elicited a surface-negative, depth-positive potential in 1-week-old kittens, indicating the existence of a large current sink in layer I; however, it induced a surface-positive, depth-negative potential in 1month-old kittens, reflecting the presence of a strong current sink in the deep cortical layers.     

Response properties of neurons in the visual cortex of the rat

Summary Response properties of neurons in the visual cortex, area 17, of Long Evans pigmented rats were investigated quantitatively with computer-controlled stimuli. Ninety percent of the cells recorded (296/327) were responsive to visual stimulation. The majority (95%, 281/296) responded to moving images and were classified as complex (44%), simple (27%), hypercomplex (13%) and non-oriented (16%) according to criteria previously established for cortical cells in the cat and monkey. The remaining 5% of the neurons responded only to stationary stimuli flashed on-off in their receptive field. Results of this study indicate that neurons of the rat visual cortex have properties similar to those of cells in the striate cortex of more visual mammals.Supported by grant EY02964, the Biological Humanics Foundation and the Bendix Corporation     

High-resolution analysis of locomotor activity rhythms indisconnected,a visual-system mutant ofDrosophila melanogaster

Free-running locomotor activity and eclosion rhythms ofDrosophila melanogaster, mutant at thedisconnected (disco) locus, are substantially different from the wild-type phenotype. Initial periodogram analysis revealed little or no rhythmicity (Dushayet al., 1989). We have reanalyzed the locomotor activity data using high-resolution signal analysis (maximum-entropy spectral analysis, or MESA). These analyses, corroborated by autocorrelograms, uncovered significant residual circadian rhythmicity and strong ultradian rhythms in most of the animals tested. In this regard thedisco mutants are much like flies expressing mutant alleles of theperiod gene, as well as wild-type flies reared throughout life in constant darkness. We hypothesize that light normally triggers the coupling of multiple ultradian oscillators into a functional circadian clock and that this process is disrupted indisco flies as a result of the neural lesion.This work was supported in part by NIH Grant FM-33205.     

Compensation of labyrinthine lesions: effects of trigeminal neurotomy on vestibular field potentials

The aim of the research was to analyse the vestibular nuclear activity before and after the section of the 5th cranial nerve in chronically hemilabyrinthectomized guinea pigs during the stage of compensation. The animals were hemilabyrinthectomized (chloroform and vaselin oil into the right middle ear) and upon compensation (24–45 days), field potentials were recorded from the vestibular nuclei of the intact side following electrical stimulation of the ipsilateral labyrinthine receptors. Then the left trigeminal trunk was sectioned ventrally through the foramen lacerum and ovale which are fused in the guinea pig and the vestibular field potentials were again recorded for a period of 120 min. Trigeminal neurotomy modified the vestibular field potentials determining an increment in amplitude of 30–50% of N₁ and N₂ waves, configuration and latency remained unaltered. The dependence of vestibular compensation on trigeminal afferents is discussed on the light of reported results.     

Cross-orientation inhibition in cat is GABA mediated

Summary Visual evoked potentials (VEPs) were recorded from cat cortex (area 17) before, during and after application of the GABA blocker bicuculline (iontophoretic or topical). The stimuli comprised a test sinusoidal grating, and a mask grating oriented either parallel or orthogonal to the test. Both test and mask alternated in contrast at different temporal frequencies. VEPs were averaged in synchrony with the test contrast reversal, so the mask did not contribute directly to the averaged VEP response. Before application of bicuculline, both parallel and orthogonal masks attenuated the amplitude of VEPs and changed the phase response, but in different ways. Orthogonal masks lowered the slope of the contrast response curve without affecting extrapolated threshold, while parallel masks caused the curve to shift to the right. Orthogonal masks increased the phase advance, while parallel masks eliminated it. During application of bicuculline, neither parallel nor the orthogonal masks attenuated VEP amplitudes. The results suggest that although the mechanisms for the action of parallel and orthogonal masks are clearly distinct, both are mediated by the GABA-ergic inhibitory system. Given this evidence, measurement of VEP contrast response curves may provide a simple non-invasive technique for monitoring visual inhibition in humans.     

Double-opponent-process mechanism underlying RF-structure of directionally specific cells of cat lateral suprasylvian visual area

Summary For the experiments reported in this study, recordings were obtained from 246 single units in the middle lateral suprasylvian visual area (LS) of 13 cats. 49 of these cells were subjected to detailed quantitative analysis. The receptive field (RF) organization was examined for directionally specific cells by presenting moving single spots on large moving random dot backgrounds. A cell's response to an optimal spot (in terms of size, direction, velocity) moving on a stationary background inside the excitatory RF (ERF) was compared to in-phase (same direction, same velocity) and anti-phase (opposite direction, same velocity) movement of spot and background. In-phase movement resulted in inhibition of the cell's response (3–100%) in 94% of the cells, while anti-phase movement led to reduced inhibition in 52% of the cells or to facilitation (0.5–327%) in 39% of the cells. By changing the direction of background motion with respect to that of the spot, the directional tuning of the in-phase inhibition and anti-phase facilitation effects was determined.We were able to manipulate the size of the background effects by masking out the background for various proportions of the ERF, and maximizing them by restricting background stimulation to the large inhibitory RF (IRF) surrounding the ERF. These results could be best accounted for by a double-opponent-process mechanism with both RF center and RF surround being directionally selective, but with opposite polarity. It is suggested that this type of mechanism could be involved in the processing of object motion.Partially supported by an NSERC University Research Fellowship (U 0057) and an ARC equipment grant to M. von Grünau and by an NSERC Grant to B. J. Frost (A 0353)     

Behavior in chimeric mice combining differently behaving strains

A/J and C57BL/6J mice behave differently in tests for alcohol preference, open-field activity, defecation in the open field, cricket attacking, and rope climbing. Chimeric mice, i.e., mice containing both A/J cells and C57BL/6J cells, were constructed and tested for these behaviors. Patterns of behavior among A/JC57BL/6J chimeras are such as to suggest that none of these behavior differences is controlled by a single cell or clone and that the same cell population that gives rise to the strain difference in alcohol preference also gives rise to the differences in open-field activity and defecation, while separate cell populations control cricket killing and rope climbing.This research was supported by Research Grants AA 00388 and HD 03015 to M. N. N. and MH 18996 to K. B. Computing assistance was obtained from the Health Sciences Computing Facility, UCLA, supported by NIH Special Research Resources Grant RR-3.     

Generation of the eosinophil chemotactic factor (ECF) from various cell types by melittin

The peptide melittin, the main constituent of bee venom is a potent stimulus for the generation of an eosinophil chemotactic factor (ECF) from human polymorphonuclear neutrophils, rat mast cells and rat peritoneal cells depleted in mast cells. Optimal EFC induction required a sublytic activation of the cells. With each cell type the kinetics of ECF generation were similar in that after an early rise in activity a steep fall off occurred at later times of incubation suggesting a mechanism of inactivation. The induction of ECF by melittin is increased in the presence of calcium. The polar portion of the melittin molecule (aminoacids 20–26) is responsible for the generation of the chemotactic activity. Other peptides of honey bee venom such as the mast cell degranulating peptide (MCD) or apamine do not initiate ECF release. It appears that melittin leads to ECF induction via the phospholipase A₂-arachidonic acid dependent pathway of cell activation. Our data suggests that the lipid mediator ECF can be obtained from phagocytes and mast cells thus indicating the interdependence of inflammatory reactions.     

Influence of perinatal malnutrition on adult physiological and behavioral reactivity in rats

A series of experiments examined the behavioral and pituitary-adrenal response to novelty of perinatally malnourished rats tested as adults after nutritional rehabilitation begun at weaning. Neither the behavioral measures of ambulation, rearing and defecation, nor the plasma corticosterone response to a brief exposure to an open field differentiated the previously malnourished subjects from controls. Similar to controls, previously malnourished subjects were also capable of displaying a graded corticoid elevation to environments increasingly different from the home cage. However, exploratory behavior, as measured by head-dip frequency and duration in the hole-board, was reduced in the previously malnourished rats. Although latency and amount of fluid consumed in a novel environment did not differ, previously malnourished rats were unable to use the cues associated with a consummatory behavior to modulate the pituitary-adrenal response to novelty. Thus, perinatal malnutrition does not influence either the behavioral or physiological activational response to novel stimulation but appears to alter the ability of the animal to use a consummatory behavior to modulate this response.     

Electrical activity in the prefrontal cortex specific to no-go reaction of conditioned hand movement with colour discrimination in the monkey

Summary Monkeys were trained to perform hand movements in a reaction time task with discrimination between positive (go) and negative (no-go) light signals, and field potentials in various cortical areas were recorded and analysed with chronically implanted cortical electrodes. As previously reported, areas such as the prefrontal, premotor and motor cortices were active in association with simple visually-initiated, reaction-time hand movements. The caudal part of the dorsal bank of the principal sulcus was found to be activated specifically on no-go trials during discrimination, and revealed a relatively sharp surface-negative, depth-positive potential. The potential appeared at a latency of 110–150 ms, which was 150–210 ms earlier than the movement onset on go trials. With reversal of the go and no-go signals, this potential was found to be recorded only on no-go trials, irrespective of the colour used for the stimulus. It is suggested that the activity in the dorsal bank of the principal sulcus is related to the judgement not to execute the movement and/or the suppression of motor execution.