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Patterns of maternal care in lemurs. III. Lemur variegatus.
Lemur fulvus, L. catta, and L. variegatus differ markedly in the details of mother-infant relations. Do these differences account for those seen in adult life? We hope to determine this through interspecific cross-fostering. Here we describe the normal pattern of rearing of 5 infants among two groups of 2 and 5 adult L. variegatus, reared in the laboratory. The descriptions cover the first 7 months of life, and include the effects of maternal separation at 150 days of age, when estrus normally disrupts maternal care. The principal finding is that in the mother's absence young turn more to other adults than to their siblings, who are, apparently, not adequate social substitutes for adults.
[Temporary aspects of aging: a new approach to the problem].
Medical, psychologic and social problems are typical of the old age. Usually growing old means organic impair, loneliness and a lower social role; moreover, spatial behavior is completely reduced. The period could be lived and be considered in a different way, although aging is unavoidable. This work suggests that we should consider the passing of time a most comprehensive way. The cyclic, biological time can be replaced by a time which considers and gives expression to everybody's needs and activities. The first aim is to give the elderly a new social role, necessary to avoid a "ecosystemic destabilization". Therefore social workers should supply the aged with a new education at "lived time", as a new therapy form.
[Analysis of consanguinity in some populations of the V Region, Valparaiso, Chile, from 1880 to 1969].
The population structure of 10 populations ("comunas") in Valparaíso, V Region Chile, was studied through the frequency of consanguineous marriages (%CM) and the coefficient of consanguinity (alpha), in order to know their dynamics, and gather information for clinical and genetic epidemiological studies as well as for isonymy studies. The comunas were grouped according to density: Group I, high density, more than 100 inhabitants/km2; Group II, intermediate, between 25 and 99 inhabitants/km2; and Group III, low, less than 25 inhabitants/km2. Data were obtained from parochial archives and national census, from 1880 to 1969. CM's were divided in: uncle-aunt/nephew-niece (12), first cousins (22), first cousins one removed (23), second cousins (33) and multiple consanguinity (M), and the four subtypes of 12 and 22. Percentage of CM and alpha diminish in time. Groups I and II show similar values, but lower in I, and show a constant decrease. Group III has higher values and considerable fluactuations. Types 12 and 22 contribute mostly to %CM and alpha in the 3 groups. Subtypes of 12 and 22 do not occur at random. This temporary and spatial behavior can be explained because of sociocultural and socioeconomical factors in each group, being density an indicator of endogamy. This behavior is consistent with current coefficients of endogamy obtained by isonymy.
On the behavioral significance of head direction cells: neural and behavioral dynamics during spatial memory tasks.
Current theories assume that rats use the directional information reflected by head direction (HD) cells when performing spatial tasks. This assumption was assessed by monitoring anterior thalamic HD cell activity and relating it to the subject's behavioral response on 2 spatial memory tasks that tested either reference memory or working memory. In both tasks, there was a significant number of trials where there was not a tight coupling between the preferred firing direction of HD cells and the direction of the behavioral response. In addition, it was possible to intentionally change the preferred direction of HD cells without affecting performance accuracy. An additional experiment showed that manipulations that affected internal, but not external, cues impaired performance on the reference memory task. These findings suggest that HD cell activity was not consistently guiding the subjects' behavior on these 2 spatial tasks.
The spatial distribution of behavior under varying frequencies of temporally scheduled water delivery.
Two studies evaluated the effects of response-independent water deliveries on the location (on the floor of the experimental chamber) and position (height) of rats' behavior. In both experiments, fixed-time schedules delivered water in two dispensers that were located at opposite ends of the chamber. In Experiment 1, the two schedules provided complementary frequencies of water deliveries while the overall number of deliveries stayed constant. In Experiment 2, one of the schedules delivered water twice as frequently as the other; this proportion was kept constant while the overall density of water deliveries changed systematically. In both experiments, a single position (height) of behavior was dominant. Also, the percentage of time allocated to each dispenser was roughly proportional to the percentage of water deliveries associated with the dispensers. These data and additional considerations support the importance of examining the spatial properties and patterning of behavior.
Sex differences in the behavioral response to spatial and object novelty in adult C57BL/6 mice.
The present studies examined sex differences in object localization and recognition in C57BL/6 mice. Experiment 1 measured responses to spatial novelty (object displacement) and object novelty (object substitution). Males strongly preferred displaced and substituted objects over unchanged objects, whereas females showed a preference in only 1 measure of object novelty. Experiment 2 further examined object recognition by presenting mice with 2 identical objects, followed 24 hr or 7 days later by testing with a familiar and a novel object. After 24 hr, males preferentially explored the novel object, whereas females exhibited no such preference. Neither sex displayed a preference for the novel object after 7 days. The data suggest that male mice are superior to females at localizing and recognizing objects.
Effects of concurrent random-time schedules on the spatial distribution of behavior in rats.
We evaluated the effects of concurrent random temporal contingencies of water delivery on the location of rats' behavior. In this experiment, two concurrent random-time schedules delivered water in two dispensers that were located at opposite ends of the chamber, and provided complementary frequencies of water deliveries while the overall number of deliveries stayed constant. Time allocation in the areas adjacent to each water dispenser covaried with water deliveries, although no proportional relation was found. Rats showed a preference for the area where water was initially presented. The results point to the importance of examining spatial properties and patterning of behavior.
Effects of combined chronic nimodipine and acute metrifonate treatment on spatial and avoidance behavior.
The present experiment was designed to elucidate whether chronic dietary treatment with nimodipine (3 months, 1000 ppm) enhances water maze spatial navigation, passive avoidance behavior and locomotor activity, and whether such a treatment with nimodipine would interact with the therapeutic effect of acute metrifonate treatment. In young medial septum-lesioned rats, nimodipine had no effect by its own on cognitive or motor behavior, and did not enhance the water maze and passive avoidance behavior improving action of metrifonate (3 and 10 mg/kg. p.o.). Nimodipine treatment of aged rats did not markedly affect the deficit in motor performance. Single and combined nimodipine and metrifonate (3 and 10 mg/kg, p.o.) treatment of aged rats resulted in shorter escape distance values to the hidden water maze escape platform compared to those of control aged rats. The passive avoidance performance of aged rats was more effectively facilitated by a combined nimodipine and metrifonate treatment than by either of the drugs on their own. Following a washout period of 2.5 months the rats that were treated previously with nimodipine no longer performed better than aged controls in the water maze test. Furthermore, after the washout period metrifonate 10 mg/kg was no longer effective in improving the water maze behavior of the now 26-month-old rats irrespective of their chronic pretreatment. Taken together, these findings indicate that chronic nimodipine and acute metrifonate treatment may more effectively stimulate cognitive functioning than either of the treatments on their own.
Brain and behavioral asymmetries for spatial preference in rats.
Rats were handled daily for 3 min between birth and weaning, or were nonhandled controls. When adult, 4 males from each litter received a right neocortical ablation, a left ablation, a sham operation, or no surgery. A month later all animals were tested in the open field for 4 days, and their initial direction of movement from the starting square (whether right or left) was recorded. Non-handled rats with intact brains (sham-operated and no-surgery groups pooled) had a mean directionality score near zero, thus indicating no right-left spatial preference. However, non-handled animals without a left hemisphere were significantly more biased in going to the ipsilateral side than were their siblings with right-brain ablations. Thus, in non-handled animals behavioral symmetry in making spatial choices is due to balanced brain asymmetry, in which the right hemisphere biases the animal to move leftward while the left hemisphere acts to inhibit this response. In contrast, intact handled rats had a significant preference to go to the left, thus suggesting that in handled animals the right hemisphere controls spatial preference.
Aspects of spatial memory and behavioral disinhibition in Tg2576 transgenic mice as a model of Alzheimer's disease.
Transgenic mouse models of Alzheimer's disease (AD) have been recently advanced. Tg2576 mice have been shown to develop progressive beta-amyloid (Abeta) neuritic plaques and exhibit impairment of cognitive function. The aim of this study was a better characterization of different aspects of spatial memory performance of transgenic mice, observed at a time when levels of soluble Abeta are elevated and Abeta neuritc plaques start to appear. A general elevation of basal locomotory activity in the home cage was found in Tg2576 mice, which also exhibited an impairment of spontaneous alternation in the Y-maze test. Tg2576 mice were not flexible upon changes in the schedule and failed to codify spatially the testing environment. Consistently, a deficit of spatial memory was also observed when mice were assessed for levels of reactivity to spatial change in the modified open-field test with objects. Compared to controls, Tg2576 mice also exhibited an increased number of explorative approaches to the different objects, and failed to discriminate the displacement of the object. Consistently with the hypothesis of increased disinhibition, a differential behavioural response to the plus-maze paradigm was exhibited by Tg2576 mice. Results clearly indicate that Tg2576 mice are characterized by a number of specific behavioral cognitive alterations, compatible with Alzheimer's disease (AD), which make them a suitable animal model for testing of novel anti-AD drugs.
Spatial learning/memory and social and nonsocial behaviors in the spontaneously hypertensive, Wistar-Kyoto and Sprague-Dawley rat strains.
The Spontaneously Hypertensive rat (SHR) is often described as less behaviorally reactive than its normotensive strain, the Wistar-Kyoto (WKY), although results are somewhat inconsistent across studies. In part, this may be due to the lack of a definitive characterization of "reactivity." Still, results from identical behavioral tests of SHR and WKY across studies are sometimes conflicting. Further, few comparisons with other rodent strains are available and these might provide guidance in outlining the meaning of reactivity. Here, social and nonsocial behaviors and spatial learning and memory were measured in male and female SHR, WKY, and Sprague-Dawley (SD) rats. Systolic blood pressure measurements at adulthood confirmed hypertension in the SHR. Juvenile play behavior indicated that SHRs were more sensitive to the strain of their play partner than were the WKY or SD, playing less with different strain partners than with same strain partners. However, adult dominance behavior (restricted access in a water competition test) indicated no strain differences. The SHR appeared to exhibit attenuated acoustic startle relative to the WKY and SD and their prepulse inhibition was substantially less at higher prepulse decibel intensities; however, this decreased prepulse inhibition was not the result of decreased startle during the test. Anxiety-related behavior in the elevated plus maze was most prominent in the SD strain, possibly as a result of poorer motor coordination as measured by rotarod performance. Elevated plus maze behavior as well as motor coordination did not differ between the SHR and WKY strains. Performance in the NCTR complex maze and the Morris water maze was significantly better in the SHR. These results do not support hypotheses of decreased behavioral reactivity in the SHR strain. Rather, they suggest complex interactions between social and nonsocial environments and the behavioral capabilities and requirements of the rat strain.
Long-term monitoring of hippocampus-dependent behavior in naturalistic settings: mutant mice lacking neurotrophin receptor TrkB in the forebrain show spatial learning but impaired behavioral flexibility.
Previous behavioral studies (Minichiello et al., Neuron 1999;24:401-414) showed that mice deficient for the TrkB receptor in the forebrain were unable to learn a swimming navigation task with an invisible platform and were severely impaired in finding a visible platform in the same setup. Likewise, additional behavioral deficits suggested a malfunction of the hippocampus and proximally connected forebrain structures. In order to discriminate whether the behavioral impairment was caused either by deficits in spatial memory and learning, or alternatively by loss of behavioral flexibility, 8 trkB mutant, 13 wild-type, and 22 heterozygous mice were implanted with transponders and released for 21 days into a large outdoor pen (10 x 10 m). The enclosure contained 2 shelters and 8 computer-controlled feeder boxes, delivering food portions for every mouse only during their first visit. Every third day, mice received food ad libitum inside the shelters. All mice learned to patrol the boxes correctly within a few days. However, significant differences emerged during those days with free food available. Wild-type mice remained inside the shelters, while all homozygous mutants continued to patrol the boxes in their habitual way, the heterozygous mutants showing intermediate scores. These and previous data suggest that one of the natural functions of the mouse hippocampus is to comediate behavioral flexibility, and that TrkB receptors might play an essential role in maintaining the neuronal short-term plasticity necessary for this capacity.
Pre-target activity in visual cortex predicts behavioral performance on spatial and feature attention tasks.
Physiological studies in humans and monkeys have revealed that, in response to an instruction to attend, areas of sensory cortex that code the attributes of the expected stimulus exhibit increases in neural activity prior to the arrival of the stimulus. Models of selective visual attention posit that these increases in activity give attended stimuli a processing advantage over distracting stimuli. Here, we test two key predictions of this view by using functional magnetic resonance imaging to record human brain activity during a cued voluntary orienting task. First, we tested whether pre-stimulus modulations are observed during both cued spatial and cued feature attention. Secondly, we tested whether the magnitude of pre-stimulus modulations predicts behavioral performance. Our results indicate that cue-triggered expectation of targets with particular spatial or nonspatial features activates areas of the visual cortex selective for these features. Furthermore, the magnitude of the cue-triggered modulations correlated with behavioral measures, such that those subjects who exhibited relatively large pre-stimulus modulations of activity performed better on the behavioral task. These findings support the view that top-down control systems bias activity in sensory cortices to favor the processing of expected target features and that this bias is related to behavior.
Changes in spatial selectivity of pattern-ERG components with stimulus contrast.
Electrical mass responses of the visual system to stripe patterns of varying fineness (spatial frequency) can show either an amplitude maximum at a medium spatial frequency, a behavior termed "spatial selectivity," or a monotonic decrease in amplitude with increasing spatial frequency. The former behavior is probably mediated by neurons having a center-surround receptive field structure and the latter by neurons lacking this antagonism. The pattern-evoked human electroretinogram was studied in this report using different spatial frequencies and pattern contrasts. The positive component of the response showed a spatial selectivity only at low contrast but was not spatially selective at the highest contrast. The negative component showed a spatial selectivity at all contrast levels. The data indicate that if pattern-related responses activated by antagonistic receptive fields are to be studied, low contrast values should be employed and attention should be paid to the negative component of the response.
Scale-invariant behavior in a spatial game of prisoners' dilemma.
A spatially extended version of the game of prisoner's dilemma, originally proposed by Nowak and May, is modified to include stochastic updating and found to exhibit scale-invariant behavior. Two critical regimes with different scaling behaviors are found; the corresponding exponents have been determined numerically. Spatially, the critical states are characterized by the existence of delicately balanced networks of defectors separating domains of cooperators; temporally, the evolution of the critical states following local perturbations is characterized by avalanches of various magnitudes, which cause restructuring of the networks of defectors on all scales.
Behavioral insensitivity to restraint stress, absent fear suppression of behavior and impaired spatial learning in transgenic rats with hippocampal neuropeptide Y overexpression.
Exogenous neuropeptide Y (NPY) reduces experimental anxiety in a wide range of animal models. The generation of an NPY-transgenic rat has provided a unique model to examine the role of endogenous NPY in control of stress and anxiety-related behaviors using paradigms previously used by pharmacological studies. Locomotor activity and baseline behavior on the elevated plus maze were normal in transgenic subjects. Two robust phenotypic traits were observed. (i) Transgenic subjects showed a markedly attenuated sensitivity to behavioral consequences of stress, in that they were insensitive to the normal anxiogenic-like effect of restraint stress on the elevated plus maze and displayed absent fear suppression of behavior in a punished drinking test. (ii) A selective impairment of spatial memory acquisition was found in the Morris water maze. Control experiments suggest these traits to be independent. These phenotypic traits were accompanied by an overexpression of prepro-NPY mRNA and NPY peptide and decreased NPY-Y1 binding within the hippocampus, a brain structure implicated both in memory processing and stress responses. Data obtained using this unique model support and extend a previously postulated anti-stress action of NPY and provide novel evidence for a role of NPY in learning and memory.
Dynamic circuitry for updating spatial representations. I. Behavioral evidence for interhemispheric transfer in the split-brain macaque.
Internal representations of the sensory world must be constantly adjusted to take movements into account. In the visual system, spatial updating provides a mechanism for maintaining a coherent map of salient locations as the eyes move. Little is known, however, about the pathways that produce updated spatial representations. In the present study, we asked whether direct cortico-cortical links are required for spatial updating. We addressed this question by investigating whether the forebrain commissures-the direct path between the two cortical hemispheres-are necessary for updating visual representations from one hemifield to the other. We assessed spatial updating in two split-brain monkeys using the double-step task, which involves saccades to two sequentially appearing targets. Accurate performance requires that the representation of the second target be updated to take the first saccade into account. We made two central discoveries regarding the pathways that underlie spatial updating. First, we found that split-brain monkeys exhibited a selective initial impairment on double-step sequences that required updating across visual hemifields. Second, and most surprisingly, these impairments were neither universal nor permanent: the monkeys were ultimately able to perform the across-hemifield sequences and, in some cases, this ability emerged rapidly. These findings indicate that direct cortical links provide the main substrate for updating visual representations, but they are not the sole substrate. Rather, a unified and stable representation of visual space is supported by a redundant cortico-subcortical network with a striking capacity for reorganization.