Dynamic regulation of the siphon withdrawal reflex of Aplysia californica in response to changes in the ambient tactile environment.

The state of an animal's environment can be viewed as a source of information that can be used to regulate both ongoing and future behavior. The present work examined how the ambient environment can regulate the Aplysia siphon withdrawal reflex (SWR) by changing the environment between calm and turbulent. Results indicate that the SWR is dynamically regulated on the basis of variations in external conditions, so that responsiveness (measured as both reflex duration and threshold) is matched to the state of the environment. Prior exposure to a noxious stimulus (tailshock) has selective effects on this regulation, suggesting the existence of multiple regulatory mechanisms. Further, neurophysiological correlates to behavioral observations were measured in sensory and motor neurons. This will allow for a detailed cellular analysis of environmental information-processing in this system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative analysis of the relation between gill amplitude and siphon duration in the defensive withdrawal reflex of Aplysia..

The defensive withdrawal reflex of the mantle organs (gill, siphon, and mantle shelf) of the marine mollusc Aplysia californica has been the subject of numerous studies investigating the cellular and molecular mechanisms of learning. In behavioral experiments, the reflex has been monitored by means of two different response measures, either siphon duration (in unrestrained, freely moving animals) or gill amplitude (in restrained preparations). It has generally been assumed that one component of the reflex provides a reliable index of the other. In the present study, we directly tested this assumption by simultaneously measuring both response parameters in the same experiment. Reflex response magnitude was varied in two ways: (a) by systematically varying stimulus intensity, and (b) by holding the stimulus intensity constant, but delivering stimuli at a rate that produced significant habituation. Using both measures we found that gill amplitude and siphon duration were highly correlated (average correlation?=?.90). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The control of food-caching behavior by Western scrub-jays (Aphelocoma californica).

Western scrub-jays (Aphelocoma californica) did not show extinction when caching behavior was never rewarded and they had no choice of where to cache the food. However, when the jays had the choice of caching items in 2 different locations or during 2 successive episodes, and only 1 of each was always rewarded at recovery, they rapidly learned to cache in the rewarded location or episode. When the jays had learned during training trials that their caches were always moved to 1 of 2 locations they did not cache in, then on the test trial they cached in the location that had been previously rewarded. To test whether these jays avoided the location in which their caches had been pilfered or chose the rewarded location, the procedure was repeated to include a 3rd location that was never rewarded. The jays avoided the pilfered location but cached equally in the rewarded and nonrewarded locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroethological studies of reflex plasticity in intact Aplysia..

Multi-unit recording of siphon nerve activity in intact Aplysia californica (a marine gastropod) with chronically implanted cuff electrodes provided a monitor of activity in a central pattern generator, the Interneuron II (Int II) network, which produces large siphon and gill contractions both spontaneously and after tactile stimulation of the siphon. The phase–response curve of the Int II oscillator for single stimuli at different phases of the cycle showed a "refractory" period early in the cycle, after which most stimuli phase advanced the oscillator and caused a short-latency Int II burst and a large contraction. The amplitude of gill withdrawal and the duration of siphon withdrawal in response to different stimulus intensities depended on whether an Int II burst was triggered. Activation of the Int II oscillator transformed the reflex from one that was graded smoothly with stimulus intensity to one in which nearly maximal responses were elicited even by weak stimuli. Entrainment and habituation training both involved monotonous repetition of a stimulus at specific intervals. With repeated siphon stimuli, nearly maximal reflex responses were maintained in intact Ss as long as the Int II oscillator was entrained, whereas habituation was associated primarily with failure to entrain the oscillator. Sensitized Ss showed significantly more triggered Int II burst than did controls. Digital spike-train analysis indicated that individual siphon motoneurons showed significantly increased background activity that often persisted for several minutes. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reexamination of spectral mechanisms in the rat (Rattus norvegicus).

Studied the spectral mechanisms of Long-Evans and Zucker rats in electrophysiological and behavioral experiments. The photopic electroretinogram was recorded (a) to rapidly flickering lights, (b) during the cone phase of dark adaptation, and (c) with a flicker photometric procedure. The consistent conclusion from both experiments is that the rat retina contains only a single photopic spectral mechanism. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence that hemolymph glucose in Aplysia californica is regulated but does not affect feeding behavior.

Hemolymph glucose increased following a meal of a commercially available dried seaweed (laver) in Aplysia californica. Glucose injected into the hemocoel did not affect meal size, bite latencies, swallowing rate, or 24-hr food intake. The authors found that injection of a homogenate of nerves containing a putative Aplysia insulin-like substance decreased hemolymph glucose. The nerve homogenate, however, did not affect feeding behavior. Injection of 2-deoxy-{D}-glucose was found to increase hemolymph glucose, an indication of gluco-privation, but instead of increasing feeding it either had no effect or, at high doses, debilitated animals and interfered with feeding. These studies suggest that glucose may be physiologically regulated in Aplysia, but it does not appear to play a role in the control of feeding behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship between dishabituation, sensitization, and inhibition of the gill- and siphon-withdrawal reflex in Aplysia californica: Effects of response measure, test time, and training stimulus.

Previous studies have raised questions about the relationships between habituation, dishabituation, sensitization, and inhibition of reflex responses. To explore this issue further, a systematic study of these simple forms of learning was carried out in unrestrained Aplysia in which the amplitude as well as the duration of both the gill- and siphon-withdrawal reflexes were measured after either tailshock or mantle shock. The results suggest that transient reflex inhibition is not an invariant effect of noxious stimulation but depends instead on the response measure, test time, and type of noxious stimulus. Furthermore, the results suggest that dishabituation and sensitization may not involve different processes at the behavioral level; rather the observed differences between them may be due largely to an interaction between habituation and inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interacting cache memories: Evidence for flexible memory use by Western scrub-jays (Aphelocoma californica).

When Western Scrub-Jays (Aphelocoma californica) cached and recovered perishable crickets, N. S. Clayton, K. S. Yu, and A. Dickinson (2001) reported that the jays rapidly learned to search for fresh crickets after a 1-day retention interval (RI) between caching and recovery but to avoid searching for perished crickets after a 4-day RI. In the present experiments, the jays generalized their search preference for crickets to intermediate Rls and used novel information about the rate of decay of crickets presented during the RI to reverse these search preferences at recovery. The authors interpret this reversal as evidence that the birds can integrate information about the catching episode with new information presented during the RI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motor neuronal function in old Aplysia is improved by long-term stimulation of the siphon/gill reflex.

As Aplysia age, motor neuronal (L?) elicited gill-pinnule contractions (PCs) are significantly decreased as is transmission at pinnule junctions (PJT). To determine whether this reduced function of L? with increased age could be altered, the siphon/gill reflex was stimulated regularly in unrestrained old animals. Aplysia were assigned randomly into trained and untrained groups. For more than 3 wks, a 1-s, 25-g water jet stimulus was administered to the siphon of the trained animals 10 times per day at 20-min intervals. The duration of siphon withdrawal increased significantly during training. In semi-intact preparations, PCs and PJT were then measured during 3-s depolarized pulses to L? (frequency range?=?1–44 per 3-s interval). The trained animals had (a) significantly higher PCs, (b) a significantly greater increase in PCs elicited by increasing L? spike rates, (c) significantly higher double-spike facilitation, and (d) significantly higher facilitation per spike across the 4 spike trains below or at PC threshold. The significant training-induced increases in both PC and PJT indicate that a considerable level of plasticity still exists in an aging nervous system. Whether this long-term training of Aplysia retards the same processes responsible for the age-related decline in neuromuscular transmission or produces a compensatory change in other neuronal processes is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation and dishabituation of the proleg withdrawal reflex in larvae of the sphinx hawk, Manduca sexta.

The neural circuit for the proleg withdrawal reflex (PWR) of Manduca sexta larvae exhibits activity-dependent plasticity. This study demonstrates habituation and dishabituation of PWR behavior. Repeated deflection of 1 or 5 mechanosensory hairs on a proleg at a 60-sec interstimulus interval (ISI) for 20 trials produced a significant decrease in evoked force of proleg withdrawal. Habituation was similar with 30-sec and 60-sec ISls and nonsignificant with a 5-min ISI or without repeated stimulation. Habituated responses recovered after cessation of stimulation or pinch of the body wall (dishabituation). The role of intersegmental influences was tested by severing connectives to leave different numbers of ganglia connected to the test segment. Habituation was robust even in test segments that were disconnected from the rest of the central nervous system. The PWR of Manduca is appropriate for further analysis of cellular mechanisms underlying learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial reversal learning and the evolution of behavioral flexibility in three species of North American corvids (Gymnorhinus cyanocephalus, Nucifraga columbiana, Aphelocoma californica).

In serial reversal learning, subjects learn to respond differentially to 2 stimuli. When the task is fully acquired, reward contingencies are reversed, requiring the subject to relearn the altered associations. This alternation of acquisition and reversal can be repeated many times, and the ability of a species to adapt to this regimen has been considered as an indication of behavioral flexibility. Serial reversal learning of 2-choice discriminations was contrasted in 3 related species of North American corvids: pinyon jays (Gymnorhinus cyanocephalus), which are highly social; Clark's nutcrackers (Nucifraga columbiana), which are relatively solitary but specialized for spatial memory; and western scrub jays (Aphelocoma californica), which are ecological generalists. Pinyon jays displayed significantly lower error rates than did nutcrackers or scrub jays after reversal of reward contingencies for both spatial and color stimuli. The effect was most apparent in the 1st session following each reversal and did not reflect species differences in the rate of initial discrimination learning. All 3 species improved their performance over successive reversals and showed significant transfer between color and spatial tasks, suggesting a generalized learning strategy. The results are consistent with an evolutionary association between behavioral flexibility and social complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Addendum to "Summation in the chimpanzee (Pan troglodytes)."

Rumbaugh, Savage-Rumbaugh, and Hegel (1987) reported that two chimpanzees (Pan troglodytes) could select, with better than 90% accuracy, the greater of two paired quantities of chocolate chips. In that study, no one quantity of chocolates (from 0 through 5) was used in both pairs on a given trial. We investigated the effect of having one quantity in common (CQ) in both pairs. Whether the other quantities (OQs) of chocolates were both less than or greater than the CQ, summation still occurred. Accuracy was primarily a function of the ratios of sums to be differentiated. This finding substantiated the earlier conclusion that summation was based on both quantities of each pair and not on some simpler process such as the avoidance of the tray with the smallest single amount or selection of the tray with the single largest amount. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Avoidance learning and "personality" in the guppy (Poecilia reticulata).

The authors examined the relationships between 2 "personality" dimensions (Approach and Fear Avoidance) and 2-way active avoidance learning performance in the guppy (Poecilia reticulata). Contrary to expectations (based on prior rodent studies), higher fearfulness facilitated both earlier appearance and acquisition of the shuttlebox avoidance responses, especially in the less exploratory and active fish. However, the overall maximum level of performance was not much affected by the 2 personality dimensions studied. Thus, the results emphasized the species-specific and interactional effect of fearfulness on the 2-way avoidance learning performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Summation in the chimpanzee (Pan troglodytes).

In this research, we asked whether 2 chimpanzee (Pan troglodytes) subjects could reliably sum across pairs of quantities to select the greater total. Subjects were allowed to choose between two trays of chocolates. Each tray contained two food wells. To select the tray containing the greater number of chocolates, it was necessary to sum the contents of the food wells on each tray. In experiments where food wells contained from zero to four chocolates, the chimpanzees chose the greater value of the summed wells on more than 90% of the trials. In the final experiment, the maximum number of chocolates assigned to a food well was increased to five. Choice of the tray containing the greater sum still remained above 90%. In all experiments, subjects reliably chose the greater sum, even though on many trials a food well on the "incorrect" tray held more chocolates than either single well on the "correct" tray. It was concluded that without any known ability to count, these chimpanzees used some process of summation to combine spatially separated quantities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personalities of octopuses (Octopus rubescens).

Large individual differences are commonly found in the behavior of octopuses, even in standardized situation. 44 Octopus rubescens were tested in 3 situations (alerting, threat, and feeding) to quantify this variation. A factor analysis of resulting behaviors isolated 3 orthogonal dimensions of their variability, Activity, Reactivity, and Avoidance, which accounted for 45% of the variance. The similarity of these factors to dimensions of personality in humans and individual differences in animals suggests there may be commonalities in such variation across phyla. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food Caching by Western Scrub-Jays (Aphelocoma californica) Is Sensitive to the Conditions at Recovery.

Western scrub-jays (Aphelocoma californica) cached perishable and nonperishable food items, which they could recover after both short and long retention intervals. When perishable items were always degraded at recovery, jays decreased the number of perishable items cached and increased their caching of nonperishable items, relative to a control group whose caches were always fresh at recovery. Jays reduced the number of nonperishable items cached, however, when highly preferred food items were degraded only after the long retention intervals. The findings are discussed in terms of the role of retrospective and prospective processes in the control of caching. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response-specific inhibition during general facilitation of defensive responses in Aplysia..

Siphon responses of Aplysia have been used to examine the neural basis of nociceptive behavioral inhibition. The authors tested the response specificity and functional significance of this inhibition. Video analysis showed that strong tail-nerve shock decreased the duration of siphon constriction evoked by weak siphon shock. Tail-nerve shock also caused the appearance of a novel flaring response to the test stimulus, which resembled the siphon response to tail-nerve shock. Novel flaring responses were expressed to both mechanical and electrical siphon stimuli. Tailshock facilitated another defensive response, inking, during the period of inhibited siphon constriction. Tailshock also facilitated tail contractions evoked by weak contralateral tail stimulation during this period. These results indicate that inhibition is not generalized across defensive responses and is specific to siphon responses that interfere with directed ink ejection toward an injured site. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Audiogram of the fox squirrel (Sciurus niger).

The behavioral audiograms of 2 fox squirrels (Sciurus niger) were determined with a conditioned avoidance procedure. The squirrels were able to hear tones ranging from 113 Hz to 49 kHz at a level of 60 dB sound-pressure level or less, with their best sensitivity of 1 dB occurring at 8 kHz. Their ability to hear frequencies below 150 Hz indicates that they have good low-frequency hearing, as do the 2 other members of the squirrel family (black-tailed and white-tailed prairie dogs) for which audiograms are available. This suggests that the ancestral sciurid may also have had good low-frequency hearing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Presence of conspecifics facilitates learning that food is inedible in Aplysia fasciata..

Absence of a conspecific, but not of food, interfered with learning and memory of a feeding task in Aplysia fasciata. Interference was shown by a shortened training session and by lack of savings on retraining. The shortened training was not responsible for the lack of savings because brief training in the presence of a conspecific led to savings on retraining. Animals trained in the absence of a conspecific and then tested in its presence did not show signs of having learned, which indicates that the absence of a conspecific interfered with the ability to learn, rather than with the expression of memory. Absence of a conspecific also inhibited other aspects of feeding behavior, such as the latency to respond to food and the length of time that animals respond to food, which indicate that interference with learning was apparently caused by inhibition of feeding behavior, rather than by block of the mechanisms underlying learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence in orangutans (Pongo pygmaeus), chimpanzees (Pan troglodytes), and children (Homo sapiens).

Juvenile and adult orangutans (n?=?5; Pongo pygmaeus), chimpanzees (n?=?7; Pan troglodytes), and 19- and 26-month-old children (n?=?24; Homo sapiens) received visible and invisible displacements. Three containers were presented forming a straight line, and a small box was used to displace a reward under them. Subjects received 3 types of displacement: single (the box visited 1 container), double adjacent (the box visited 2 contiguous containers), and double nonadjacent (the box visited 2 noncontiguous containers). All species performed at comparable levels, solving all problems except the invisible nonadjacent displacements. Visible displacements were easier than invisible, and single were easier than double displacements. In a 2nd experiment, subjects saw the baiting of either 2 adjacent or 2 nonadjacent containers with no displacements. All species selected the empty container more often when the baited containers were nonadjacent than when they were adjacent. It is hypothesized that a response bias and inhibition problem were responsible for the poor performance in nonadjacent displacements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)