Biology subjects

Vasilev, D.

Publications and source records attributed to Vasilev, D..

3 recordsLinked to original sources

bioRxiv2022

Brightness illusions evoke pupil constriction and a visual cortex response in rats

The mind affects the body via central nervous system (CNS) control of the autonomic nervous system (ANS). In humans, one striking illustration of the mind-body connection is that illusions, subjectively perceived as bright, drive constriction of the eyes pupil by activating the sympathetic arm of the ANS. How the CNS is involved in this pupil response is unknown and requires an animal model for intracerebral investigation of potential regions, cell types, and neuronal projections. However, the physiological response to this illusion has long been thought to occur only in humans. Here, we report that the same brightness illusion that evokes pupil constriction in humans also does so in rats. Cortex-wide EEG recordings revealed that, compared to a luminance-matched control stimulus, the illusion (which appears subjectively brighter to humans) evoked a larger response only in primary visual cortex (V1). This cortical response preceded pupil constriction by ~335 msec suggesting a potential causal role for V1 on the pupil. Our results establish a new animal model of importance for studying how the CNS response involved in sensing a brightness illusion drives a physiological reaction in the body. We provide objective evidence that complex mind-body connections are not confined to humans and that V1 may be part of a shared, mammalian, neural network for bodily reactions to illusions.

neuroscience↗

bioRxiv2022

Focusing perceptual attention in one modality constrains subsequent learning in another modality

Contemporary neuroscience and psychiatry suggest that attention to decision outcomes guides rule learning by adjusting stimulus-outcome associations. Separately, sensory neurophysiology conceptualizes attention as a filter that improves perception. Here, we show that the contemporary view is incomplete by demonstrating an unconventional and novel effect of perceptual attention on subsequent outcome-based rule learning. Moreover, we show for the first time in rodents that, like in primates, this attentional process involves tuning of modality specific cortico-cortical interactions. We designed a novel head-fixed rat-on-a-treadmill apparatus and used it to train rats to discriminate auditory-visual stimuli using one modality and then reduced stimulus discriminability in that modality. We observed perceptual learning suggesting engagement of perceptual attention. Moreover, engaging visual perceptual attention resulted in more saccades and increased frontal-visual cortex EEG Granger causality relative to engaging auditory perceptual attention. We then presented novel and easily discriminable stimuli in both modalities and measured outcome-driven learning in the other modality. Learning was slower after engaging perceptual attention. Our work suggests that a more complete description of learning requires integrating these previously siloed concepts of attention. Moreover, treating impaired set-shifting as a trans-diagnostic symptom may require targeting different neural circuits for perceptual attention or outcome-based attention depending on which type of attention is impaired in each neuro-psychiatric disorder.

neuroscience↗

bioRxiv2021

Three water restriction schedules used in rodent behavioral tasks transiently impair growth and differentially evoke a stress hormone response without causing dehydration

Water restriction is commonly used to motivate rodents to perform behavioral tasks; however, its on hydration and stress hormone levels are unknown. Here, we report daily body weight and bi-weekly packed red blood cell volume and corticosterone in adult male rats across 80 days for three commonly used water restriction schedules. We also assessed renal adaptation to water restriction using post-mortem histological evaluation of renal medulla. A control group received ad libitum water. After one week of water restriction, rats on all restriction schedules resumed similar levels of growth relative to the control group. Nominal hydration was observed, and water restriction did not drive renal adaptation. An intermittent restriction schedule was associated with an increase in corticosterone relative to the control group. Our results suggest that the water restriction schedules used here will maintain welfare in rats. However, intermittent restriction evokes a stress response which could affect behavioral and neurobiological results. Our results also suggest that stable motivation in behavioral tasks may only be achieved after one week of restriction.

neuroscience↗