CATS PERCEIVE BIOLOGICAL MOTION

Abstract— With behavioral techniques, cats were trained to discriminate a point-light animation sequence depicting biological motion (i.e., a cat walking) from an animation sequence consisting of equivalent local motion vectors lacking the global synchrony present in the biological-motion sequence (i.e., "foil" displays). Successful discrimination was evidenced for even the most difficult foil display and for different versions of the biological-motion sequence, indicating that cats are able to extract the higher order kinematic invariants embodied in these novel motion displays.     

A neural theory of binocular rivalry

When the two eyes view discrepant monocular stimuli, stable single vision gives way to alternating periods of monocular dominance; this is the well-known but little understood phenomenon of binocular rivalry. This article develops a neural theory of binocular rivalry that treats the phenomenon as the default outcome when binocular correspondence cannot be established. The theory posits the existence of monocular and binocular neurons arrayed within a functional processing module, with monocular neurons playing a crucial role in signaling the stimulus conditions instigating rivalry and generating inhibitory signals to implement suppression. Suppression is conceived as a local process happening in parallel over the entire cortical representation of the binocular visual field. The strength of inhibition causing suppression is related to the size of the pool of monocular neurons innervated by the suppressed eye, and the duration of a suppression phase is attributed to the strength of excitation generated by the suppressed stimulus. The theory is compared with three other contemporary theories of binocular rivalry. The article closes with a discussion of some of the unresolved problems related to the theory.     

The search for meaning in (new) work: Task significance and newcomer plasticity

Using temporally-lagged data from 146 business and engineering newcomers, we found evidence for a “positive side” of plasticity theory (Brockner, 1988, p. 547) in fostering newcomer adjustment. Specifically, as predicted, we found that higher newcomer generalized self-efficacy positively moderates the association between job design (i.e., task significance of the newcomer's job) and newcomer attitudes (in our study, organizational identification, job satisfaction, intentions to quit). Our findings promote plasticity theory as readily applicable to both newcomer adjustment and positive organizational scholarship.     

Rapid acquisition of bias in signal detection: dynamics of effective reinforcement allocation

We investigated changes in bias (preference for one response alternative) in signal detection when relative reinforcer frequency for correct responses varied across sessions. In Experiment 1, 4 rats responded in a two-stimulus, two-response identification procedure employing temporal stimuli (short vs. long houselight presentations). Relative reinforcer frequency varied according to a 31-step pseudorandom binary sequence and stimulus duration difference varied over two values across conditions. In Experiment 2, 3 rats responded in a five-stimulus, two-response classification procedure employing temporal stimuli. Relative reinforcer frequency was varied according to a 36-step pseudorandom ternary sequence. Results of both experiments were analyzed according to a behavioral model of detection. The model was extended to incorporate the effects of current and previous session reinforcer frequency ratios on current-session performance. Similar to findings with concurrent schedules, effects on bias of relative reinforcer frequency were highest for the current session. However, carryover from reinforcer ratios of previous sessions was evident. Generally, the results indicate that bias can come under control of frequent changes in relative reinforcer frequency in both identification and classification procedures.     

Reduced activation of left orbitofrontal cortex precedes blocked vocalization: A magnetoencephalographic study

While stuttering is known to be characterized by anomalous brain activations during speech, very little data is available describing brain activations during stuttering. To our knowledge there are no reports describing brain activations that precede blocking. In this case report we present magnetoencephalographic data from a person who stutters who had significant instances of blocking whilst performing a vowel production task. This unique data set has allowed us to compare the brain activations leading up to a block with those leading up to successful production. Surprisingly, the results are very consistent with data comparing fluent production in stutterers to controls. We show here that preceding a block there is significantly less activation of the left orbitofrontal and inferiorfrontal cortices. Furthermore, there is significant extra activation in the right orbitofrontal and inferiorfrontal cortices, and the sensorimotor and auditory areas bilaterally. This data adds weight to the argument forwarded by Kell et al. (2009) that the best functional sign of optimal repair in stutterering is activation of the left BA 47/12 in the orbitofrontal cortex.Educational objectives: At the end of this activity the reader will be able to (a) identify brain regions associated with blocked vocalization, (b) discuss the functions of the orbitofrontal and inferior frontal cortices in regard to speech production and (c) describe the usefulness and limitations of magnetoencephalography (MEG) in stuttering research.     

Choline reverses scopolamine-induced memory impairment by improving memory reconsolidation

It is widely known that pre-training systemic administration of the muscarinic antagonist scopolamine (SCP) (0.5mg/kg, i.p.) leads to anterograde memory impairment in retention tests. The administration of the α(7)-nicotinic receptor agonist choline (Ch) in the dorsal hippocampus (0.8μg/hippocampus) immediately after memory reactivation allowed recovery from scopolamine-induced memory impairment. This effect of Ch was time-dependent, and retention performance was not affected in drug-treated mice that were not subjected to memory reactivation, suggesting that the performance effects are not due to non-specific effects of the drug. The effects of Ch also depended on the age of the reactivated memory. Altogether, our results suggest that Ch exerts its effects by modulating memory reconsolidation, and that the memory impairment induced by low doses of SCP is a memory expression failure and not a storage deficit. Therefore, reconsolidation, among other functions, might serve to change memory expression in later tests. Summarizing, our results open new avenues about the behavioral significance and the physiological functions of memory reconsolidation, providing new strategies for recovering memories from some types of amnesia.