Optimal perceived timing: integrating sensory information with dynamically updated expectations

The environment has a temporal structure, and knowing when a stimulus will appear translates into increased perceptual performance. Here we investigated how the human brain exploits temporal regularity in stimulus sequences for perception. We find that the timing of stimuli that occasionally deviate from a regularly paced sequence is perceptually distorted. Stimuli presented earlier than expected are perceptually delayed, whereas stimuli presented on time and later than expected are perceptually accelerated. This result suggests that the brain regularizes slightly deviant stimuli with an asymmetry that leads to the perceptual acceleration of expected stimuli. We present a Bayesian model for the combination of dynamically-updated expectations, in the form of a priori probability of encountering future stimuli, with incoming sensory information. The asymmetries in the results are accounted for by the asymmetries in the distributions involved in the computational process

Restoration of contact inhibition in human glioblastoma cell lines after MIF knockdown

<p>Abstract</p> <p>Background</p> <p>Studies of the role of the cytokine macrophage-migration-inhibitory-factor (MIF) in malignant tumors have revealed its stimulating influence on cell-cycle progression, angiogenesis and anti-apoptosis.</p> <p>Results</p> <p>Here we show that <it>in vitro </it>targeting MIF in cultures of human malignant glioblastoma cells by either antisense plasmid introduction or anti-MIF antibody treatment reduced the growth rates of tumor cells. Of note is the marked decrease of proliferation under confluent and over-confluent conditions, implying a role of MIF in overcoming contact inhibition. Several proteins involved in contact inhibition including p27, p21, p53 and CEBPalpha are upregulated in the MIF antisense clones indicating a restoration of contact inhibition in the tumor cells. Correspondingly, we observed a marked increase in MIF mRNA and protein content under higher cell densities in LN18 cells. Furthermore, we showed the relevance of the enzymatic active site of MIF for the proliferation of glioblastoma cells by using the MIF-tautomerase inhibitor ISO-1.</p> <p>Conclusion</p> <p>Our study adds another puzzle stone to the role of MIF in tumor growth and progression by showing the importance of MIF for overcoming contact inhibition.</p

Self-prioritization and perceptual matching: The effects of temporal construal.

Recent research has revealed that self-referential processing enhances perceptual judgments - the so-called self-prioritization effect. The extent and origin of this effect remains unknown, however. Noting the multifaceted nature of the self, here we hypothesized that temporal influences on self-construal (i.e., past/future-self continuity) may serve as an important determinant of stimulus prioritization. Specifically, as representations of the self increase in abstraction as a function of temporal distance (i.e., distance from now), self-prioritization may only emerge when stimuli are associated with the current self. The results of three experiments supported this prediction. Self-relevance only enhanced performance in a standard perceptual-matching task when stimuli (i.e., geometric shapes) were connected with the current self; representations of the self in the future (Expts. 1 & 2) and past (Expt. 3) failed to facilitate decision making. To identify the processes underlying task performance, data were interrogated using a hierarchical drift diffusion model (HDDM) approach. Results of these analyses revealed that self-prioritization was underpinned by a stimulus bias (i.e., rate of information uptake). Collectively, these findings elucidate when and how self-relevance influences decisional processing

The effects of initial interval size on the efficacy of DRO schedules of reinforcement

The differential reinforcement of other behavior (DRO) is a behavior-reduction procedure that has been popular for several years. In classroom settings, it provides reinforcement when a student does not display inappropriate responding for a particular interval of time. Unfortunately, relatively little is known about how to use DRO effectively in applied settings. Most research has been conducted in laboratory settings; the purpose of the present study was to provide a replication of one of those studies. This study examined the effect of the size of the initial DRO interval on the disruptive behavior of students with moderate disabilities. In the first experiment, a group of six students was observed during baseline in two classes. Two different DRO values were then used. In one classroom, it was equal to the mean number of 10-second intervals between disruptions during baseline. In the other classroom, it was twice the mean number during baseline. In the final phase, behavior in both classrooms was put under the same DRO program. In the second experiment, the disruptive behavior of three students was studied in a different design in which both methods of determining the initial DRO value were compared. The results of both experiments showed that an initial DRO value equal to the mean number of intervals between responses in baseline was much more effective than a value twice that size in reducing disruptions

Individual differences in motor timing and its relation to cognitive and fine motor skills

The present study investigated the relationship between individual differences in timing movements at the level of milliseconds and performance on selected cognitive and fine motor skills. For this purpose, young adult participants (N = 100) performed a repetitive movement task paced by an auditory metronome at different rates. Psychometric measures included the digit-span and symbol search subtasks from the Wechsler battery as well as the Raven SPM. Fine motor skills were assessed with the Purdue Pegboard test. Motor timing performance was significantly related (mean r =. 3) to cognitive measures, and explained both unique and shared variance with information-processing speed of Raven's scores. No significant relations were found between motor timing measures and fine motor skills. These results show that individual differences in cognitive and motor timing performance is to some extent dependent upon shared processing not associated with individual differences in manual dexterity