Pilfering ravens, Corvus corax, adjust their behaviour to social context and identity of competitors

Like other corvids, food-storing ravens protect their caches from being pilfered by conspecifics by means of aggression and by re-caching. In the wild and in captivity, potential pilferers rarely approach caches until the storers have left the cache vicinity. When storers are experimentally prevented from leaving, pilferers first search at places other than the cache sites. These behaviours raise the possibility that ravens are capable of withholding intentions and providing false information to avoid provoking the storers' aggression for cache protection. Alternatively, birds may refrain from pilfering to avoid conflicts with dominants. Here we examined whether ravens adjust their pilfer tactics according to social context and type of competitors. We allowed birds that had witnessed a conspecific making caches to pilfer those caches either in private, together with the storer, or together with a conspecific bystander that had not created the caches (non-storer) but had seen them being made. Compared to in-private trials, ravens delayed approaching the caches only in the presence of storers. Furthermore, they quickly engaged in searching away from the caches when together with dominant storers but directly approached the caches when together with dominant non-storers. These findings demonstrate that ravens selectively alter their pilfer behaviour with those individuals that are likely to defend the caches (storers) and support the interpretation that they are deceptively manipulating the others' behaviour.This contribution is part of the special issue “Animal Logics” (Watanabe and Huber 2006).     

Evidence that baroreflex feedback influences long-term incidental visual memory in men

Sympathetic nervous system (SNS) activity at the time of acquisition is associated with human memory. However, rather than SNS activity per se, it may be afferent baroreflex feedback that is responsible for this effect. A pharmacological design was employed to unload (SNP, sodium nitro-prusside) and load (norepinephrine) baroreceptors. In addition to two placebo periods, epinephrine and esmolol (a peripherally acting beta1-blocker) served as control conditions for altered cardiac perception. During drug infusion blood pressure, heart rate, and perception of heartbeat were tested. Twenty-four healthy men were participated. The participants viewed emotional slides while their electromyographic eye blink responses to random noise bursts were measured (affective startle modulation paradigm) to determine potential drug impact on emotional processing. Subjects were not informed that memory testing would take place after 4 weeks. Drugs did not impact startle, thus indicating unbiased emotional processing at the time of acquisition. Norepinephrine had no effect on heartbeat perception, but improved (p = .002) recognition memory. SNP (p = .0001) increased heartbeat perception but impaired (p = .038) recognition memory. Epinephrine, on the other hand, increased heartbeat perception (p = .0001) yet did not impair but partially improve memory (effect on high arousing pictures only: p = .05). Heartbeat perception in the placebo condition did not correlate with recognition memory (p's > .5). We suggest that baroreflex unloading, with subsequent feedback activation of the SNS, impairs long-term incidental visual recognition memory in humans while baroreflex loading enhances it. Further, we propose that these memory effects are neither secondary to cardiac sensations that accompany SNS activation nor to altered emotional picture processing at the time of acquisition.     

Dissociation between extension of the sensitive period for avian vocal learning and dendritic spine loss in the song nucleus lMAN

Several instances of early learning coincide with significant rearrangements of neural connections in regions contributing to these behaviors. In fact developmentally restricted learning may be constrained temporally by the opportunity for experience to selectively maintain appropriate synapses amidst the elimination of exuberant connections. Consistent with this notion, during the normal sensitive period for vocal learning in zebra finches (Taenopygia guttata), there is a decline in the density of dendritic spines within a region essential for song development, the lateral magnocellular nucleus of the anterior nidopallium (lMAN). Moreover, in birds isolated from conspecific song shortly after hatching, both the closure of the sensitive period for vocal learning and the pruning of spines from lMAN neurons is delayed. Here, we employed a more subtle form of deprivation to delay the close of the sensitive period for song learning, and found that late song learning occurred without obvious alterations in the pruning of dendritic spines on lMAN neurons. At posthatch day (PHD) 65 (beyond the end of the normal sensitive period for song memorization in zebra finches), birds isolated from song beginning on PHD30 did not differ from normally reared birds in measures of dendritic spine density on Golgi-Cox stained lMAN neurons. Moreover, tutor exposure from PHD65 to 90 did not increase spine elimination in these isolates (who memorized new song material) relative to controls (who did not). Thus, we conclude that the extent of normally occurring lMAN spine loss is not sufficient to account for the timing of the sensitive period for zebra finch song learning.     

Programming of expected and unexpected movements: effects on the onset of the lateralized readiness potential

When participants utilize prime information to prepare some or all aspects of the forthcoming movement, reaction time (RT) costs are obtained when the imperative response signal demands an unexpected rather than an expected movement. Longer RT in trials for which primes are invalid rather than valid, i.e., the response validity effect, are taken to reflect prolonged motoric processing time. The present study was designed to test this assumption by using the lateralized readiness potential (LRP) in order to reveal influences of response validity at motoric processes, pre-motoric processes, or both. In two response priming experiments LRP onset latency was examined when valid and invalid advance information about direction (Experiment 1) or about direction and hand (Experiment 2) was provided. RT revealed large response validity effects in both experiments. Analysis of LRP onsets provided strong evidence against the common assumption of a motoric locus of the RT increase in invalid trials. Rather, the present results suggest a pre-motoric locus of the response validity effect within information processing.     

View dependence in scene recognition after active learning

Human spatial encoding of three-dimensional navigable space was studied, using a virtual environment simulation. This allowed subjects to become familiar with a realistic scene by making simulated rotational and translational movements during training. Subsequent tests determined whether subjects could generalize their recognition ability by identifying novel-perspective views and topographic floor plans of the scene. Results from picture recognition tests showed that familiar direction views were most easily recognized, although significant generalization to novel views was observed. Topographic floor plans were also easily identified. In further experiments, novel-view performance diminished when active training was replaced by passive viewing of static images of the scene. However, the ability to make self-initiated movements, as opposed to watching dynamic movie sequences, had no effect on performance. These results suggest that representation of navigable space is view dependent and highlight the importance of spatial-temporal continuity during learning.     

Die Therapeutenrotation

For seven years, the so-called “rotation of therapists”, has been a central part of OLITA, the outpatient longterm intensive therapy for alcoholics. Thus far, the participation of several equally responsible therapists in the treatment of a patient has rarely been seen as a defined therapeutic approach. The present work discusses whether the “rotation of therapists” has any essential influence on the success of OLITA. It considers both, potential advantages and disadvantages for patients and therapists and tries to identify conditions under which this approach appears to promote therapeutic interactions. Following an overview of the present knowledge regarding the therapeutic interaction in addiction therapy, a method is described which may be seen as the precedent of the “rotation of therapists”, the multiple psychotherapy. Finally, the practical procedure in OLITA is outlined as well as its theoretical background. New areas of application for the “rotation of therapists” are discussed.     

Decomposing sources of response slowing in the PRP paradigm

The mechanism underlying the reaction time (RT2) slowing to the 2nd of 2 successively presented stimuli (S1 and S2) in the psychological refractory period paradigm was investigated. Stimulus onset synchrony (SOA) between S1 and S2, contrast of S2, and Task 2 set-level compatibility was manipulated. Specifically, the authors used a psychophysiological approach to examine RT2 slowing in trials in which the reaction time to S1 (RT1) was shorter than the SOA. For trials with RT1 < SOA, the clear decrease in RT2 with increasing SOA was underadditive with the S2 contrast effect, but additive with compatibility. Electrophysiological measures revealed an exclusively premotoric locus of RT2 slowing. These findings indicate that a central bottleneck stage is occupied for some period after response to S1 execution, consistent with an extended response selection bottleneck account.