Single 5HTR2A-1438 A/G nucleotide polymorphism affects performance in a metacontrast masking task: Implications for vulnerability testing and neuromodulation of pyramidal cells

Context-Sensitive Conscious Interpretation and Layer-5 Pyramidal Neurons in Multistable Perception

INTRODUCTION

There appears to be a fundamental difference between the two ways of how an object becomes perceptually experienced. One occurs when preconscious object-specifying sensory data processing crosses a certain threshold so that sensory constituents of object depiction become consciously experienced. The other occurs when the already consciously experienced sensory features of the object become interpreted as belonging to a certain visual object category. Surprisingly, experimental facts about neural markers of conscious access gathered so far do not allow us to distinguish mechanisms responsible for these two varieties.

METHODS

A cortical multicompartment layer-5 pyramidal neuron-based generic processing model is presented in order to conceptualize a possible mechanistic solution for the explanatory cul-de-sac. To support the argument, a review of pertinent research is compiled as associated with data from studies where physically invariant perceptual stimuli have underwent alternative interpretation(s) by the brain.

RESULTS

Recent developments in the newly emerging field of cellular psycho(physio)logy are introduced, offering a hypothetical solution for distinguishing the mechanisms subserving sensory content experience and conscious interpretation.

CONCLUSION

The multicompartment single cell-based mechanistic approach to brain process correlates of conscious perception appears to have an added value beyond the traditional inter-areal connectivity-based theoretical stances.

The factorial structure of individual differences in visual perception

Although at first glance the way we perceive the world is similar for most individuals and resembles a veridical interpretation of the environment, the persistent individual differences found in many perceptual processes continue to inspire and confuse researchers. Despite numerous attempts to map out the reliable factors and correlates of individual variance in perception, the factorial structure of vision has remained elusive. The current article reviews recent developments in the study of individual differences in perception with a focus on work that has applied latent variable techniques for analysing performance across multiple visual paradigms. As this overview reveals, studies that have attempted to answer the question whether one general or several specific factors best describe vision tend to reject the monolithic view. Some general notes are also provided regarding pitfalls that should be taken into account when designing such research in the future.

Excess of individual variability of priors prevents successful development of general models

Perceptual judgments are influenced by a multitude of factors in addition to the perceptual input. Particularly, the widely varying individual neurobiological endophenotypes and individual differences in the propensity for expectation-based illusory percepts make it unlikely that optimality is possible to define and defend by the type of abstract modeling approach criticized by Rahnev & Denison (R&D).

Expectation creates something out of nothing: The role of attention in iconic memory reconsidered

Conscious experience is modulated by attention and expectation, yet is believed to be independent of attention. The experiments on iconic memory (IM) are usually taken as support for this claim. However, a recent experiment demonstrated that when attention is diverted away from the IM letter display subjects fail to see the absence of IM letters. Here we contribute to the ongoing debate by overcoming experimental shortcomings of this previous experiment, by measuring subjective visibility and by testing the effect of the post-cue. We were able to replicate these earlier findings and extend them by demonstrating that subjects who do not realize the absence of letters perceive illusory letters. This result means that there is still phenomenal consciousness, even when attention is diverted. Expectation creates illusory content that overwrites valid IM content. Taken together these findings suggest that the present experimental paradigm is not appropriate to make claims about IM content.

Effect of a human serotonin 5-HT2A receptor gene polymorphism on impulsivity: Dependence on cholesterol levels

BACKGROUND

Impulsivity is multidimensional: Low impulse control may result in behavioural disorders, but acting on the spur of moment may also be advantageous. Previous studies have shown negative associations between different facets of impulsivity and serotonergic function. Other investigations have found negative correlations between serum lipid levels and impulsivity.

METHODS

We have investigated whether the functional polymorphism -1438A/G in the serotonin 5-HT_2A receptor gene (HTR2A) is associated with impulsivity levels and whether there is any interaction with serum lipid levels. This analysis was based on data of the population-representative Estonian Children Personality Behaviour and Health Study at age 25. Impulsivity was self-reported with the Adaptive and Maladaptive Impulsivity Scale.

RESULTS

Subjects with the A/A genotype of the HTR2A -1438A/G polymorphism had higher scores of Maladaptive impulsivity, but not Adaptive impulsivity. In females, high LDL and total cholesterol levels increased the genotype effect. In males, in the highest quartile of total or LDL cholesterol the genotype effect was altered, with G/G homozygotes having the highest Maladaptive impulsivity levels.

LIMITATIONS

Only one cohort of the European Youth Heart Study (EYHS) was used in the current study and impulsivity measures were self-reported.

CONCLUSIONS

Our results do not support the notion that low cholesterol levels universally lead to higher impulsivity, but it was found that high total and LDL cholesterol levels moderate the effect of the HTR2A gene promoter polymorphism. This suggests that future studies on impulsivity need to consider the interaction of serotonergic measures with the whole range of cholesterol levels.

How a (sub)Cellular Coincidence Detection Mechanism Featuring Layer-5 Pyramidal Cells May Help Produce Various Visual Phenomena

Perceptual phenomena such as spatio-temporal illusions and masking are typically explained by psychological (cognitive) processing theories or large-scale neural theories involving inter-areal connectivity and neural circuits comprising of hundreds or more interconnected single cells. Subcellular mechanisms are hardly used for such purpose. Here, a mechanistic theoretical view is presented on how a subcellular brain mechanism of integration of presynaptic signals that arrive at different compartments of layer-5 pyramidal neurons could explain a couple of spatiotemporal visual-phenomenal effects unfolding along very brief time intervals within the range of the sub-second temporal scale.