Changing viewpoints during dynamic events

The connection of various viewpoints of a visual dynamic scene can be realised in different ways. We examined if various presentation modes influence scene recognition and cognitive representation type. In the learning phase, participants saw clips of basketball scenes from (a) a single, unvaried viewpoint, or with a change of viewpoint during the scene, whereby the connection was realised (b) by an abrupt cut, or (c) by a continuous camera move. In the test phase, participants had to recognise video stills presenting basketball scenes from the same or differing viewpoints. As expected, cuts led to lower recognition accuracy than a fixed unvaried viewpoint, whereas this was not the case for moves. However, the kind of connection between two viewpoints had no influence on the viewpoint dependence of the cognitive representation. Additionally, it was found that the amount of viewpoint deviation seemed to influence the overall conservativeness of participants' reactions.     

The effect of brief auditory stimuli on visual apparent motion

When two discrete stimuli are presented in rapid succession, observers typically report a movement of the lead stimulus toward the lag stimulus. The object of this study was to investigate crossmodal effects of irrelevant sounds on this illusion of visual apparent motion. Observers were presented with two visual stimuli that were temporally separated by interstimulus onset intervals from 0 to 350 ms. After each trial, observers classified their impression of the stimuli using a categorisation system. The presentation of short sounds intervening between the visual stimuli facilitated the impression of apparent motion relative to baseline (visual stimuli without sounds), whereas sounds presented before the first and after the second visual stimulus as well as simultaneously presented sounds reduced the motion impression. The results demonstrate an effect of the temporal structure of irrelevant sounds on visual apparent motion that is discussed in light of a related multisensory phenomenon, 'temporal ventriloquism', on the assumption that sounds can attract lights in the temporal dimension.     

What is in a view? The role of featural information in the recognition of unfamiliar faces across viewpoint transformation

In recognising a face the visual system shows a remarkable ability in overcoming changes in viewpoint. However, the mechanisms involved in solving this complex computational problem, particularly in terms of information processing, have not been clearly defined. Considerable evidence indicates that face recognition involves both featural and configural processing. In this study we examined the contribution of featural information across viewpoint change. Participants were familiarised with unknown faces and were later tested for recognition in complete or part-face format, across changes in view. A striking effect of viewpoint resulting in a reduction in profile recognition compared with the three-quarter and frontal views was found. However, a complete-face over part-face advantage independent of transformation was demonstrated across all views. A hierarchy of feature salience was also demonstrated. Findings are discussed in terms of the problem of object constancy as it applies to faces.     

The genetic versus pharmacological invalidation of the cannabinoid CB(1) receptor results in differential effects on 'non-associative' memory and forebrain monoamine concentrations in mice

The endocannabinoid CB(1) receptor has been implicated in the inhibitory control of learning and memory. In the present experiment, we compared the behavioral response of CB(1) receptor knockout mice (CB(1)R(-/-)) with animals administered CB(1) receptor antagonist/inverse agonist SR141716A (rimonabant; 3 mg/kg IP, 30 min pre-trial) in terms of acquisition and retention of a habituation task and changes in cerebral monoamines. The results can be summarized as follows: (i) the acute and chronic invalidation of the CB(1) receptor resulted in an increase of behavioral habituation during the first exposure to an open field, indicative of enhanced acquisition of the task; (ii) CB(1)R(-/-) mice, but not rimonabant-treated animals, showed enhanced retention of the habituation task when re-tested 48 h and 1 week subsequent to the first exposure to the open field, respectively; (iii) the facilitation of retention of the habituation task in CB(1)R(-/-) mice was accompanied by a selective and site-specific increase in serotonin activity in hippocampus; and (iv) rimonabant-treated animals displayed 'antidepressant-like' neurochemical alterations of cerebral monoamines, that is, most parameters of monoaminergic activity were increased especially in dorsal striatum and hippocampus. Taken together, the present findings demonstrate that the genetic disruption of the CB(1) receptor gene can cause an improvement of behavioral habituation, which is considered to represent a form of 'non-associative' learning. Furthermore, our data support the assumption of a rimonabant-sensitive cannabinoid receptive site that is different from the 'classical' CB(1) receptor and which, under physiological conditions, might be involved in the inhibitory control of the acquisition but not retention of non-associative learning tasks.     

At your own peril: An ERP study of voluntary task set selection processes in the medial frontal cortex

A tool that is commonly used to investigate selection among different alternatives in a changing environment is the task-switching paradigm. Functional neuroimaging has pointed out a role for the posterior medial frontal cortex and the posterior parietal cortex in the voluntary selection of task sets. In the present study, we set out to investigate the temporal dynamics of these agency-related processes (in task choice vs. no-choice conditions) using event-related brain potentials (ERPs). The results revealed agency-related modulations of a series of ERP components, including (1) an early parieto-occipital activation, taken to reflect the evaluation of choice versus no choice; (2) a subsequent medial frontal expression of the voluntary selection between task sets; (3) a CNV-like sustained negativity in preparation for the target; (4) a target-induced N210—P210 complex, taken to reflect early sensory-perceptual processing; and (5) a target-induced P3, associated with the evaluation of the stimulus and its designated response vis-à-vis the chosen versus competing task sets. Together, these results indicate that the opportunity to choose between tasks invokes activity originating from the medial frontal cortex, associated with voluntary task set selection, but also activation at different time points in a number of other brain areas, not necessarily captured by functional neuroimaging.     

Olfactory discrimination of estrous condition by the male golden hamster (Mesocricetus auratus)

After repeated exposure to receptive and nonreceptive females, male golden hamsters were tested for olfactory preferences in a four-choice olfactometer. Males discriminated between the odor of anesthetized females in different stages of their estrous cycle when the airstreams carrying the stimulus odors were diluted. Previous failures to demonstrate such an ability were probably due to ceiling effects resulting from laboratory testing. Males preferred the odor of females on the day before receptivity (a day coincident with maximal scent marking by the female) and least preferred the odor of females on diestrus-1 (the day on which females attacked and chased males during pretesting encounters). Detection and quick response to an impending estrus would be especially important for males of a solitary and promiscuous species in which there is a first male mating advantage.     

The fundamental: Ungrounded or all-grounding?

Philosophical Studies - Fundamentality plays a pivotal role in discussions of ontology, supervenience, and possibility, and other key topics in metaphysics. However, there are two...     

Pop-out for illusory rather than veridical trajectories with double-drift stimuli

Attention, Perception, & Psychophysics - If a patch of texture drifts in one direction while its internal texture drifts in the orthogonal direction, the perceived direction of this...     

Behavioral and physiological correlates of aggressive dominance in male brown lemmings (Lemmus sibiricus)

Naive male brown lemmings were paired with the same opponent for 10 min/day for 11 consecutive days. Males of a control group were placed in an empty arena for the same period. There was no decrement in the incidence of attack and chase by dominant males in pairs showing stable dominant-subordinate relations. Subsequently, seminal vesicles of dominant animals were heavier than those of subordinate, control and “no rank” (pairs in which no clear-cut dominance relations were established) animals. Dominant animals also had greater mean testis weights and higher plasma testosterone levels than subordinates. Adrenal weights did not differ significantly between the various groups. Among dominant males there were significant positive correlations between plasma testosterone levels, testis and seminal vesicle weights, and attack and chase scores. These results suggest that many of the physiological correlates of dominance status reported in previous studies in which subjects were group housed are also observed when contact between naive individuals is limited to brief encounters.