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Resume Des rats recoivent 30 min avant l'acquisition d'un conditionnement d'evitement dans un labyrinthe en Y, soit une injection sous-cutanee de cycloheximide (2,5 mg/kg), soit une injection de serum physiologique. Les criteres d'acquisition sont de 4 ou 8 reponses d'evitement consecutives. L'epreuve de retention a lieu 2 hr, 24 hr ou 6 jours apres l'acquisition. Nos resultats montrent que: (1) l'acquisition est normale sous inhibition profonde de la synthese proteique; (2) un deficit de la memoire s'observe 2 hr apres l'acquisition, uniquement pour le groupe entraine avec un critere faible; (3) un jour apres l'apprentissage, et quel que soit le niveau d'acquisition de la tâche, tous les sujets experimentaux presentent une importante perturbation mnesique; (4) dans tous les cas, une recuperation spontanee de la memoire se manifeste 6 jours apres l'acquisition. Nous avons controle que le deficit mnesique n'est pas imputable a une alteration des capacites de restitution de l'information acquise. L'amnesie temporaire est interpretee en termes de ralentissement du developpement de la memoire a long terme consecutif a une diminution du taux de synthese des neurotransmetteurs.

Two series of psychoacoustic tests were conducted to determine the applicability of the psychophysical theory of signal detectability (TSD) to prediction of the aural detectability of noise signatures in differing noise backgrounds. The first series of tests produced data supporting development of a simplified graphical prediction method based on TSD. A second series validated the precision and accuracy of the prediction method under quasi-realistic conditions. Predicted levels of performance were typically within one or two dB of the data.

Pigeons pecked a key and rats pressed a lever for food reinforcement under large values of the differential-reinforcement-of-low-rate schedule. Each subject was tested under 10 different schedule values ranging from 1 to 45 min and was exposed to each schedule value at least twice. The mean interresponse time and mean interreinforcement time increased with the schedule value according to power functions. Response-probability functions were computed for schedule values below 20 min and showed an increase in response probability as a function of time since the last response in most cases. Mean responses per reinforcer increased as a function of schedule value for the rats, but decreased as a function of schedule value for the pigeons. The proportion of responses with interresponse times shorter than 1 sec were an increasing function of schedule value for the pigeons, but did not vary as a function of schedule value for the rats.

Hamsters maintained in isolation boxes for 4–7 weeks were allowed to select their own lighting regimens by pressing levers, and to be active in running wheels. Three hamsters expressed circadian rhythms of light preference and of wheel-running activity (Figs. 1–3). Light tended to be selected during the inactive phase, and darkness was selected during wheel-running activity. By such a circadian rhythm of self-selected lighting, these hamsters are behaving in a way which may maintain those metabolic cycles that depend upon a 24-hour oscillation of light and darkness.

Warrington and Weiskrantz reported a significant interaction between method of testing and subject group when amnesics' and controls' memory was tested after a 1 min retention interval. An attempt was made to duplicate this finding without using any amnesic subjects but substituting for them a group of normal subjects with a presumably weak memory trace and comparing them with a group of normal subjects with a presumably strong memory trace. The attempt succeeded. Each subject learned a list of 100 words and was then tested on half the words after 1 min and on the other half after one week. A separate group of six subjects was used for each of the following methods of testing: yes-no recognition; cueing with initial letters; cueing with a fragmented form of the words. The statistic corresponding to the interaction between method of testing and retention interval was significant. Also normal performance on yes-no recognition at one week was (like amnesic performance significantly inferior to normal performance at 1 min; and normal performance on each of the methods of partial information at one week (like amnesic performance) did not differ significantly from normal performance at 1 min. Certain reservations and implications are discussed but it is concluded that Warrington and Weiskrantz's experiment can no longer be regarded as providing support for the theory that the amnesic syndrome is limited to a defect of retrieval.

Male mice castrated before Day 6 of postnatal life differ from adult castrates in that they do not exhibit normal patterns of intermale aggression following replacement therapy as adults. Two experiments sought to determine the effect castration after Day 6, but before puberty, would have on this response to adult replacement therapy. It was found that adult castrates showed some increases in fighting as early as six hr after a subcutaneous (s.c.) injection of 2 mg testosterone propionate (TP). At 30 hr after treatment 14/15 mice fought, while at 72 hr 15/15 fought and the number of fights in 10 min was significantly higher than at 30 hr. In the second experiment, the response to adult treatment with 2 mg TP (s.c.) in mice castrated in Day 10 or Day 50 was compared. Different groups were tested at 16, 40, 64, and 88 hr after TP treatment. The latency to respond to TP was significantly less and the level of fighting obtained was significantly greater in Day 50 castrates than in Day 10 castrates at each time of testing. The proportion of Day 10 (14/15) and Day 50 (15/15) castrates fighting was equal by 88 hr, while the mean fighting frequency was significantly lower in Day 10 castrates (M = 4.93 ± 4.78) than in Day 50 castrates (M = 8.06 ± 1.63). Day 50 castrates fought significantly more often than controls at 40 hr, whereas the level of fighting attained by Day 10 castrates was not significant until 64 hr. These results suggest that even after the organizational period for aggression, testosterone is necessary for maintenance and/or preparation of the substrate essential to the elicitation of aggression.

The purpose of this study was to determine if the changes in operant responding observed after shifts in reinforcement magnitude are due to antecedent reinforcement conditions, or the absolute reinforcement magnitude in effect at any given time. All animals in both experiments were responding on a multiple VI 20 second-extinction schedule of reinforcement. In one experiment, the animals were trained on 0.04 ml dippers, and were subsequently switched to both large and smaller dipper sizes. In the second experiment, three groups of rats were trained on 0.01, 0.04 and 0.10 ml dippers; each group was run exclusively on its designated dipper size. Data from both experiments were computer processed to yield a detailed description of response pattern. Rate of response, during both schedule components, depended on reinforcement magnitude only in the first experiment. Pausing behavior, both after reinforcement and during response runs, was inversely correlated with reinforcement magnitude in both experiments. It was concluded that pausing is a function of absolute dipper size, but response rate is a function of prior reinforcement conditions.

72 young and old pigeons habituated to wearing either magnets or brass bars, half having had their bars changed, were released under an overcast sky. 1. No significant differences appear between birds habituated to magnet and those habituated to brass. 2. No significant differences appear between birds released with magnet and those released with brass. 3. Though youngs home worse than yearlings and old pigeons, no significant differences concerning the age of pigeons appears within, nor between experimental groups.

Short-term memory (repetition of sequences) was studied in three patients with conduction aphasia. Even though these patients could reproduce the items presented they could not recall the correct order of the items. It was tentatively concluded that the disorder underlying the repetition defect in these three patients was an impairment of their memory for sequences.

The relationship between sebum production of the perineal glands of male guinea pigs and social dominance was examined. Experiment 1 indicated that, while sebum production before social grouping did not predict subsequent position in a dominance hierarchy, sebum production after 6 weeks of group living did reflect relative dominance status with more dominant animals producing larger quantities. Further, social grouping resulted in increased sebum production in all animals. Finally, the frequency of the perineal drag, a scent-marking behavior, was positively related to social status and hence sebum production. In Experiment 2 it was found that changes in dominance status were usually followed by changes in the same direction in sebum production.

Forty-eight college students performed a task in which they had to request updated enemy position reports from three information sources to determine which of eight locations was the target of a gradual enemy advance. Eight different problems, presented twice each, were arranged into two factorial designs. In Design FP, the effects of pacing rate, pacing variability, and the number of decision modification opportunities were evaluated. In Design SP, information requests were self-paced rather than forced-paced; the effects of the number of decision modification opportunities and basis of payoff were studied. Results indicated that (a) self pacing and fast forced pacing resulted in more information seeking and greater accuracy than did slow forced pacing, and (b) increased opportunities for decision modification generally decreased the accuracy of, and confidence in, first decisions. The rate at which information was presented was more important than whether it was provided automatically or upon request.

Link trainers and similar synthetic flight-training devices have been used with varying effectiveness since before World War II. Currently available ground-based flight trainers differ widely in their degree and fidelity of simulation and in their associated costs. To provide a rational basis for trainer procurement, a method of assessing their cost effectiveness is needed. An experiment was conducted to establish the incremental transfer effectiveness of a representative ground-based general aviation trainer to serve as a basis for the evaluation of its incremental cost effectiveness. Four groups of student pilots were given, respectively, 0, 3, 7, and 11 hours of instruction in the Link GAT-1 concurrently with flight instruction in the Piper Cherokee airplane. Average flight times for the four groups to reach the private pilot criterion reflected the postulated negatively decelerated nature of the incremental transfer effectiveness function.

Es wird das Ortungssystem der Fledermause unter der Voraussetzung diskutiert, das es die von der statistischen Signaltheorie geforderten Eigenschaften eines in allen Parametern optimierten Systems besitzt. Diese theoretischen Forderungen an die Signal- und Empfangerstruktur werden anschliesend den in der Literatur angegebenen experimentell gewonnenen Erkenntnissen gegenubergestellt. Es wird u.a. in folgender Hinsicht Ubereinstimmung gefunden

Studies have been conducted which indicate that redundant coding is effective in facilitating the locating of a target among other objects. This study examines that hypothesis for a range of the shape and color variables. All possible combinations of four shapes and four colors were used as targets in the experiment. The times to locate six each of the targets among 36 background objects for 16 displays in each of three coding conditions of the experiment were determined for 24 subjects. The targets could be differentiated from the background objects on the basis of color only, shape only, and redundant color/shape. The results indicate a difference among the coding conditions, the colors, and the shapes, and in the code-by-shape and code-by-color interactions. An important finding is that the redundant code and the color code conditions did not differ. The data are examined for possible explanations of this result and some implications are suggested.

1. The hermit crabPagurus pollicarus maintains an internal pressure of from 4 to 10 g/cm2 in its abdomen; this increases by two to 3 g/cm2 during lift of the shell and walking. 2. Characteristic pressure changes during flexion and extension are described; in addition, the response of pressure and motoneuron firing frequency is correlated during these movements. 3. The motoneurons of the ventral superficial muscles reponds to pressure changes in the abdomen with a long latency high threshold rapidly adapting response; it is concluded that this is due to stimulation of touch receptors in the skin. 4. There is no relationship between abdominal load and internal pressure. In addition, the slopes and intercepts of load-abdominal extension curves were not significantly different from each other over a range of imposed internal pressures ranging from zero to 24 g/cm2. It is concluded that pressure does not generate lift in the absence of changes in muscle tension.

Septal-lesioned rats, when approached from below (Anterior-Ventral capture) rather than from above, displayed a remarkably reduced emotionality-score as measured by standard scales. Vocalization and biting were almost completely absent, resistance to capture and handling were considerably reduced; head jerk and vibrissae stiffening were only slightly affected. It is suggested that the septum might be involved in higher order processing of information and that the increased emotionality observed after septal lesioning results from a distorted evaluation of the threat value of sensory input.

Verbal instructions for a perceptual-motor task were presented via left or right ear to male and female right handed five-year-olds. No main effects were observed for the modes of presentation or sex. However, an interaction effect was observed indicating that females presented instructions via the left ear tended to reverse instructions; and therefore, scored significantly lower than the other sex by treatment groups.

Pigeons' pecks at two white response keys (initial-link situation) occasionally turned both keys red (terminal-link situation). When the two keys were red, pecks occasionally produced food, after which the keys were again white. In both situations, a changeover delay prevented the response-produced outcome from immediately following a change of responding from either key to the other. In the initial-link situation, the ratio of pecks at the keys closely paralleled the ratio of transitions into the terminal-link situation produced by the pecks, conforming to the well-known matching relation. In the terminal-link situation, the peck ratios deviated from the matching relation toward indifference. Overall response rate and rate of changeover were generally higher in the terminal-link situation than in the initial-link situation. The finding of matching in the initial-link situation supports a definition of reinforcement as situation transition. The differences in performance between the two situations, viewed in the light of other recent findings, suggest that the effects of a changeover delay depend on the overall reinforcing value of the choice alternatives.

Infantile handled (Days 1-20) and nonhandled, male and female Long Evans hooded rats were tested at maturity (90-100 days) over 10 daily sessions for aggressive response to footshock. Individual jump and flinch thresholds for reactivity to shock, as well as paired aggressive responding to shock, were not significantly influenced by the handling procedure, although handled females ultimately adopted higher levels of fighting than nonhandled females. Handled rats were heavier than nonhandled rats of the same sex before and after testing for social aggression. Males fought significantly more than females; the discrepancy increased with additional sessions of paired exposure to shock. Male and female fight trends over sessions were linear and positive with a greater acceleration for males. The results were interpreted as indicative of a social learning variable occurring with repeated aggressive contact and primarily affecting males.

1. Mechanosensitive receptors in the ganglionic sheath of the leech nerve cord have been found to activate the large fiber in the medial connective, Favre's nerve. 2. Application of tactile stimuli simulating pressure and noxious stimulation to the skin of an intact segment evokes large fiber discharge. 3. Stimulation of the T, P and N skin mechanoreceptor cells by tactile stimulation or by intracellular current pulses does not evoke large fiber discharge. 4. Sequential dissection experiments demonstrate that excitation of the large fiber during tactile stimulation of an intact segment is mediated by mechanoreceptors in the ganglionic sheath.

Rats were exposed to a procedure in which auditory stimuli signaled which of two levers was associated with a variable-interval 60-sec schedule of food presentation. Presses on the lever that was not associated with the variable-interval schedule (“errors”) postponed availability of reinforcement on the other lever by either a fixed number of responses or a fixed amount of time. Increasing the number of responses by which “errors” postponed food availability enhanced the level of stimulus control, and. alter a relatively high degree of control had been achieved, reduction of the requirement had no effect. Control experiments ruled out extended exposure to the discrimination procedure as a factor in the increase in stimulus control and suggested that the time of introduction of a changeover contingent is an important determinant of its effect.

Chasmodes bosquianus is a bottom-dwelling, blenniid fish. The males of this species utilize and defend enclosed nest sites during the breeding season. This species was selected as an appropriate subject for a study of habitat selection and shelter choice among hole-nesting animals. Two experimental pools were prepared containing different arrangements of two types of objects. These objects were enclosures and open shelters. The former were designed to represent an idealized shelter of the type used for nesting purposes in the field. The latter, which were arranged in rows, were vertical rectangles representing topographical irregularities of the bottom. Placement of the objects resulted in four general types of space in the experimental pools: that adjacent to open shelters, that within enclosures, open space, and that next to the walls of the pool. The blennies utilized the space next to open shelters significantly more and open space significantly less than would be expected on the basis of randomly-oriented movement. In addition, the fish followed routes that passed near the objects, as opposed to crossing open space, as they moved about in the pools. There was a tendency to use enclosures more than could be accounted for by an explanation based on random movement. When the four general regions were compared to one another with respect to use by the fish, somewhat similar results were seen. Space adjacent to open shelters was used significantly more than was open space. Edges were also more heavily utilized than was open space. During short-term (one hour) observations, the fish were found to approach the enclosure (E2) at the junction of two paths more frequently than they did the enclosure (E1) located on a single path. According to one measure, they demonstrated a greater interest in E2 also. However, an explanation for this greater interest based solely on the number of times that the fish approached E2 seems reasonable. During long-term (three-day) observations, the fish were found to utilize enclosures on various paths more than they did an enclosure in open space. No preference among the enclosures on paths of differing complexity was seen.

Factors affecting the tension on the external tympaniform membranes of the syrinx during respiration and vocalization were studied in 35 adult chickens. These membranes are controlled by the interacti

Visual discrimination of several types of stimuli were trained to each hemisphere of split-brain monkeys. Stimuli that differed only in orientation and that were spatially redundant were learned in fewer trials by the left hemisphere than by the right. Other stimuli, such as bilaterally symmetrical patterns, up-down mirror images, or photographs of monkeys' faces were learned, on the average, equally easily by either hemisphere. These preliminary results suggest that monkeys may exhibit some degree of cerebral dominance.

The behaviour of an adult Stump-tailed Macaque (Macaca arctoides) while in three different experimental situations, is compared. The experimental situations were the following: (I) the female is alone, (II) the female is in the presence of a male while allogrooming is prevented by a plexiglas partition, or (III) the male is present and allogrooming is allowed through a slit in the partition. Comparison of the situations (I) and (II) shows the presence of male induces in the female a tendency to stay close to the male, a slight reduction of locomotion and an increase in the duration of autogrooming. When the female has the opportunity to allogroom, comparing II and III, she prefers to allogroom over walking away from the male as well as over autogrooming.

Key pecking of pigeons was maintained under conjunctive schedules of food presentation in which both a fixed-interval and a fixed-ratio schedule had to be completed before a peck produced food. For two pigeons, pecks on a single key completed both schedule requirements (fixed-interval 3-min, fixed-ratio 50 for one bird, fixed-interval 5-min, fixed-ratio 50 for the second). For two other pigeons, each requirement was scheduled on a separate key. On the two-key schedule, a peck after 5 min on the key scheduling the fixed-interval requirement produced food if at least 10 pecks had occurred on the ratio key (conjunctive fixed-interval 5-min, fixed-ratio 10). When each requirement was scheduled on a separate key, response rates on the fixed-ratio key were generally higher in the early portion of the interval and declined as the interval progressed; responding on the fixed-interval key, once initiated, typically remained at a constant rate throughout the interval. Responding under the single-key schedule was characterized by a high rate early in the interval; this then changed to a lower rate that continued until a peck produced food. For all pigeons, increases in response rates with pentobarbital and d-amphetamine were inversely related to the control rate of responding. When equivalent rates on each key of the two-key schedule were compared, both drugs increased rates on the fixed-ratio key less. Although the effects of both drugs were rate dependent, each drug differentially modified the pattern of responding under the single-key schedule.

Attraction of male and female Beagles to conspecific urine, vaginal and anal sac secretion odors was examined in four experiments. Males spent more relative time investigating female urine odors than odors of vaginal or anal sac secretions. Sexually experienced males, but not sexually inexperienced ones, spent more time investigating estrous than diestrous female urine and vaginal odors. Anal sac secretions from estrous bitches were not more attractive to males than those from diestrous bitches. Estrous females spent no more time than diestrous ones in the investigation of male anal sac secretion and urine odors. Male urine and anal sac secretions elicited little investigation from male conspecifics. Females spent more time investigating female urine odors than female anal sac or vaginal secretion odors, and exhibited a slight general preference for diestrous over estrous stimuli. A positive correlation between the odor investigation times of this study and investigation times of comparable animals to conspecifics in a social situation suggests odor preferences are relatively good indicators of social preferences, and vice versa, in this breed.

Three groups of four pigeons, trained to press a treadle on a free-operant avoidance schedule, were given auditory discrimination training. Alternating 2-min components of avoidance and no shock were paired with either a tone or white noise. The pigeons were subsequently given two types of generalization tests, with and without avoidable shocks scheduled. Two of the groups, trained interdimensionally, produced excitatory and inhibitory generalization gradients along the tone frequency dimension. A predicted post-discrimination gradient was computed from the algebraic summation of these gradients of excitation and inhibition. The predicted gradient was compared with the actual post-discrimination gradient obtained from the third group of pigeons that had been given intradimensional discrimination training on the tone frequency dimension. The predicted postdiscrimination gradient agreed in shape with the empirical postdiscrimination gradient. The results in general support Spence's (1937) gradient interaction theory.

Some of the difficulties associated with the problem of determining drug effects on the visual sensory system are outlined. Specific consideration is given to the selection of human and animal subjects for study, the use of electrophysiological techniques, and a variety of experimental procedures which may be employed. Problems associated with the attention and motivation of subjects, the use of anesthesia, and the need for investigation of a wide range of drug dosages are discussed. Some experiments which reveal fairly specific effects on visual function are described.

Electrolytic lesions were made in the vestibular nuclear complex (VNC) in 25 adult bullfrogs. Following postoperative survival times of 4–35 days, the frogs were perfused with 10% formol-saline. The brains were embedded in egg yolk and frozen sections cut at 33 µm. Sections were processed according to various modifications of Nauta and Fink-Heimer techniques and the degenerating fibers traced to their termination.The VNC distributes to (1) some of the cranial nerve nuclei, (2) the cerebellum, (3) the contralateral VNC, and (4) the spinal cord. Fibers from the VNC pass ventromedially to enter the medial longitudinal fasciculus (MLF), and eventually reach the nuclei of the extraocular muscles. Fibers to the cerebellum pass rostrally from the VNC to terminate within the molecular and granular layers. The projection to the contralateral VNC passes toward the midline, and then turns sharply toward the ventral surface, where it continues its course to the contralateral VNC. The fibers destined for the spinal cord appear to terminate in the medial parts of the ventral horn.

Microscopic observations clearly illustrate a common structural plan which is visible in the whole endbrain of the dog and other species. Two cellular strata are seen in the endbrain and a third appea

Analytic methods of signal detection theory were employed to assess the utility of reinforcers. Four pigeons were trained to detect the presence or absence of a stimulus by pecking one of two side keys in a trial-by-trial choice paradigm. The relative rate of positive reinforcement for correct choices was varied to offset the biasing effects of electric shock for incorrect right side-key choices. The effects of relative rate of reinforcement on bias were similar at all shock intensities even though the subjects' sensitivity changed during the course of the experiment. The relative rate of reinforcement required to produce equal bias was calculated and plotted against shock intensity to generate utility functions. The relative rate of reinforcement necessary to offset the bias induced by shock was an increasing function of shock intensity.

Effects of various cholinergic agents on the free operant responding and single alternation behavior of rats were examined following two regimens of chronic treatment with diisopropylfluorophosphate (DFP), an irreversible anticholinesterase, which lowered brain cholinesterase to 45% and 30% of normal, respectively. Reduction to 45% produced no observable changes in behavior; reduction to 30% gave rise to a decrease in the number of reinforced responses and an increase in the number of nonreinforced responses. Tolerance for the former measure developed within 10 days, whereas tolerance for the latter was not observed. Subsequent challenges were carried out using anticholinesterase agents, and muscarinic and nicotinic agonists and antagonists. The results suggest that the sensitivity og both muscarinic and nicotinic receptors to acetylcholine may be reduced during chronic treatment with DFP, but that muscarinic receptors may be more labile than nicotinic receptors. It is hypothesized that this reduction in sensitivity is one mechanism underlying the development of behavioral tolerance to DFP.

1. A circadian rhythm in the frequency and amplitude of compound action potential (CAP) from the isolated eye ofAplysia persists for a week or morein vitro in constant darkness. This rhythm has a period of about 26 hours (Figs. 1,2) in a specific culture medium and may express several periodic amplitude components (Fig. 3). 2. Constant light (LL) of low intensity shortens the period (Pig. 4) and reduces the range of oscillations. Higher intensity LL results in a further reduction in range, a greater variability of CAP frequency from hour to hour, alterations in the period, and possibly rhythm splits (Fig. 5). 3. Pulses of light given at specific points in the circadian cycle shift the phase of the rhythm (Fig. 7). The resulting phase response curve (Fig. 8) is similar to response curves for the activity of diurnal animals and potassium pulses on the eye rhythm.

The effects of noun-class on recognition accuracy in the two visual half-fields are examined. It is found that agentive nouns are more easily recognized than either simple nouns or category-ambiguous (noun/verb) items with RVF presentation, and that both agentive and category-ambiguous nouns are more easily recognized than simple nouns with LVF presentation. This result, which contradicts an earlier hypothesis on the subject, is discussed for the implications it has for a theory of hemispheric specialization.

Visual average evoked responses were studied in situations where subjects expected after training that a different stimulus intensity would occur, or misperceived the actual intensity of the stimulus. In the first experiment, subjects were taught a simple temporal pattern of light intensities. After repeated presentation of a simple pattern of lights, subjects tended to view more complex patterns as if they were a continuation of the preceding simpler pattern. In a second experiment, when subjects erred in an absolute intensity judgment task, their AER to the misperceived stimulus had an amplitude either larger or smaller depending on the direction of the subject's error. This tendency to produce AER consistent with what the subject expected was reflected significantly in the early but not late components of the subject's average evoked response (AER). Termed the “congruence illusion”, the effect was hypothesized to be a means of protection against stimulus overload. The congruence illusion was eliminated by providing subjects with sufficient details of a complex pattern. Further, stimulus meaning effects were reflected principally in early components, while information value and contrast effects were confined to later components.

Behavioral measurements of visual capacities were made on fox squirrels (Sciurus niger). Spectral sensitivity functions measured in the context of an increment-threshold task reveal

Male rats in which the glans penis was removed at 20 days of age showed all of the sexual behavior patterns of normal rats, including ejaculation, when tested as adults. However, the distribution of the behaviors within the patterns was statistically different from normal: the experimental males required a greater number of mounts and a longer time for ejaculation than did control males.

The Stomatogastric ganglion ofPanulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach. When experimentally isolated, the ganglion continues to generate complex rhythmic patterns of activity in its motor neurons which are similar to those seen in intact animals.

Infant squirrel monkeys were reared with surrogates and tested at 4, 8, and 12 weeks of age on their preferences for odors and colors of the surrogates. Surrogates in the rearing color that contained an infant's own odor were preferred to clean ones of the same color. Surrogates in the rearing color that did not contain an animal's scent were generally not preferred to different colored surrogates that were also clean. The results suggest that olfaction plays an important role in the development of social attachment in the young squirrel monkey and is more effective than at least one source of visual information.

1. Motoneurons to muscles of the branchial basket were identified by physiological critera in isolated brain-gill preparations of small adult lampreys,Petromyzon marinus andIchthyomyzon castaneus. Intracellular stimulation of motoneurons produced one-to-one contractions in ipsilateral motor units; one-to-one electromyographic potentials were also observed (Fig. 2). Motoneurons were confirmed as such by antidromic stimulation (Fig. 3). 2. Identified respiratory motoneurons were located in the IX and X cranial motor nuclei, through which they were distributed somatotopically (Fig. 1). Cells innervating the branchial constrictor, diagonal, gill pouch, and valve muscles were intermixed. Motoneurons marked by intracellular dye injection (Fig. 4) had the same morphology as other cells of the rostral motor nucleus of the vagus. 3. During respiratory movements branchial motoneurons were driven by a periodic and powerful burst of excitatory postsynaptic potentials (EPSP's) (Fig. 5). Several observations indicated that these EPSP's were not due to electrical coupling of motoneurons, but rather were produced by unidentified pacemakers in the brain.

Toutes les séquences décrites chez les larves âgées sont observées chez les larves du premier stade. Un comportement exploratoire intense caractérise ces dernières, chaque séquence se déroulant assez lentement; de plus, seule la séquence de déplacement est facultative. Au fur et à mesure de la croissance, et à partir du stade 6, on constate que: - la mobilité antennaire augmente, - l'enchaînement des séquences se perfectionne (diminution de la durée du cycle de capture, suppression de séquences comme l'exploration). En outre, ou peut définir, en ce qui concerne la réactivité des larves vis-à-vis des leurres, un diamètre liminaire inférieur, en dessous duquel le leurre laisse les larves plus ou moins indifférentes et au-dessus duquel le leurre devient attractif, et un diamètre liminaire supérieur dont l'effet provoque des réactions de fuite. Au cours de l'ontogenèse, la distance maximale de détection antennaire ou tarsale augmente régulièrement en fonction du diamètre du leurre. Pour chaque antenne, le volume de perception a la forme d'un ellipsoïde dont le grand axe coïncide avec l'axe de l'antenne. Au stade 7, se situe l'achèvement d'un phénomène mis en évidence lors de la stimulation à distance des différents tarses: cette stimulation est suivie, chez les jeunes larves, du décrochement de la patte correspondante, avant que les extrémités antennaires entrent en contact avec le leurre. Progressivement, la fréquence des décrochements diminue. Finalement le tarse reste à la même place au cours de sa stimulation, et sert de pivot lors de la rotation. L'ajustement de la capture s'effectue rapidement dans la mesure où les mouvements d'orientation de l'animal sont exacts et précis. Comme les réactions des larves deviennent plus rapides au cours de l'ontogenèse, que la séquence d'exploration peut être supprimée, et que la précision des mouvements d'orientation augmente, on suppose la mise en œuvre, au cours de la vie larvaire, de processus de maturation du système nerveux et du système musculaire.

Three experiments were conducted to assess the aversive properties of a visual stimulus in the presence of which one group of birds received response-contingent shock (discriminated punishment) while a yoked group of birds received non-contingent shocks (conditioned suppression). In Experiment 1, presentation of the visual stimulus contingent on key pecking reduced the response rate (conditioned punishment effect) for birds under the conditioned suppression procedure but did not reduce the response rate of birds under the discriminative punishment procedure. Non-contingent shocks also produced greater suppression of responding maintained by positive reinforcement in the presence of a visual stimulus than did response-contingent shocks. In Experiment 2, a greater shock intensity (2 mA) was used. All the differences between the two groups found in Experiment 1 were also found in Experiment 2. Experiment 3 demonstrated that response-contingent shock did not result in a conditioned punishment effect even when positive reinforcers were unavailable during the discriminative punishment schedule. The exteroceptive stimulus that was paired with shock in the conditioned suppression procedure acquired the ability to punish behavior. The exteroceptive stimulus in the discriminative punishment schedule did not acquire this ability.