Ethoneuro Lab

We are interested in diverse research questions at the intersection of neuroendocrinology; parasitology and behavioral ecology. We take pride in braiding mechanistic view of biology with its mooring in the evolution and ecological conditions.
Ajai VyasLEAD PI
Ajai Vyas
Associate Professor, School of Biological Sciences
Assistant Dean (Academic), College of Science

Email: [email protected]
Phone: (65) 6513 7365
Office: SBS-02N-08
Lab webpage


Behavioral Manipulation of the Host by the Parasites
Toxoplasma is a common parasite of birds, rodents, and humans during the asexual phase of its life cycle. But, having sex for Toxoplasma is limited to cat intestines. It enters cat when an infected rat or bird is eaten up. This creates an interesting problem because rats do not prefer to be eaten up. Toxoplasma blocks the fear of cats from infected rats. This is often taken to mean that infected rats will approach cat without fear and be eaten up at higher rates. Toxoplasma is also sexually transmitted through the male ejaculate in rats. Apropos infected male rats make more testosterone; produce more sexual pheromones; and, become more attractive to uninfected females. These observations suggest a second parasitic manipulation of the host behavior, whereby being infected creates greater avenues for sexual transmission of the parasite itself.
We are interested in understanding proximate mechanisms of two parasitic behavioral manipulations described above.
More about this system can be found here

Current questions include:
  1. What are the necessary and sufficient neuroendocrine changes within the host that sustain the behavioral manipulation?
  2. Are effects of Toxoplasma on host behavior dimorphic between sexes?
  3. How does Toxoplasma breech blood-testes barrier?
  4. Is Toxoplasma a sexually transmitted infection in humans?
  5. Does Toxoplasma increase predation rates of infected rodents under field conditions?

Non-consumptive Effects of Predation
In John Gardner’s wonderful fiction ‘Grendel’, a wise protagonist sums up the nature of life with two terse axioms. “Everything fades; and, alternatives exclude”. These axioms poignantly capture the essence of animal life histories (i.e. schedule and duration of key events in an organism’s lifespan like reproduction and death). For each morsel of food regurgitated by parents for the brood, there is one less morsel available to the parents for their survival. For each decision to create bright plumage there is risk that predators also will be attracted by this sexual advertisement. In short, current fitness cannot be maximized without forgoing future fitness and survival. Alternatives of “me-now” and “me-later” exclude each other. Animals typically negotiate these trade-offs using conditional behaviors, or ‘if-then-else’ clauses. How animals execute these conditional programs? Reproduction requires presence of opportunities (e.g. presence of sexually receptive females). It also requires metabolic wherewithal, so that cost and competition during partaking of these opportunities can be sustained. How do animals integrate these factors? How do biological substrates mediate the shift of behavior from survival to reproduction or vice versa (i.e. trade-off between “me-now” and “me-later”)? Broadly, we aim to answer these questions in our research. We do this in the broader context of ecological interactions between predators, prey and parasites.
Current questions include:
  1. Does increased predation rate in the field change reproductive investment by the prey?
  2. What are the neuroendocrine substrates that calibrate defense against predators and reproductive investment across changing ecological conditions?
  3. How does a parasite balance inherent trade-offs between trophic and sexual transmission?
  4. Does cognitive impulsivity co-elute with reproductive investment in laboratory and field rodents?
  5. Can cognitive aging be prevented using gonadal hormones?

Cognitive Dissonance in Higher Education
Subject competency involves crossing thresholds of troublesome knowledge unique to each discipline. I propose that cognitive dissonance can serve as a powerful motivator to cross such thresholds. Cognitive dissonance occurs when a person holds two mutually opposing cognitive constructs simultaneously, creating a state of the negative drive. This drive initiates efforts to reduce dissonance by cognitive accommodation and/or systematic avoidance. Cognitive accommodation is the process of negotiating opposing constructs until a tolerable congruence is obtained. Alternatively, the discomfort of the dissonance leads to systematic avoidance of a situation where the cognitive conflict is likely to become explicit again. Therein lays both the potential and pitfall of using cognitive dissonance in education. Cognitive dissonance unites cognition with motivation. This is fundamental to its formulation as a drive (motivation) to change dissonance through accommodation (cognition). Thus it can be harnessed towards conceptual change. This is important because threshold knowledge is often troublesome. Moreover, such knowledge requires multiple forays through the liminal space between previous cognitive constructs and their later modifications. Students require strong motivation to cross these thresholds. Teachers often use backwash effect created by careful alignment between assessment and intended outcomes to maintain the motivation. That source of motivation is reactive in nature (‘I need to learn this because it is going to be in assessment’). In contrast, motivation produced by cognitive dissonance results in a proactive change (‘this is uncomfortable, this needs to change’). Thus the use of this approach in pedagogy is valuable for intentional and meaningful learning.
Full list of publications can be found here
  • Tong, W.H., S. Abdulai-Saiku, and A. Vyas, Testosterone Reduces Fear and Causes Drastic Hypomethylation of Arginine Vasopressin Promoter in Medial Extended Amygdala of Male Mice. Frontiers in Behavioral Neuroscience, 2019. 13: p. 33.
  • Abdulai-Saiku, S. and A. Vyas, ALoss of predator aversion in female rats after Toxoplasma gondii infection is not dependent on ovarian steroids. Brain, behavior, and immunity, 2017. 65: p. 95-98.
  • Tan, D. and A. Vyas, Infection of male rats with Toxoplasma gondii induces effort-aversion in a T-maze decision-making task. Brain, behavior, and immunity, 2016. 53: p. 273-277.
  • Tan, D. and A. Vyas, Toxoplasma gondii infection and testosterone congruently increase tolerance of male rats for risk of reward forfeiture. Hormones and behavior, 2016. 79: p. 37-44.
  • Vyas, A., Mechanisms of host behavioral change in Toxoplasma gondii rodent association. PLoS pathogens, 2015. 11(7): p. e1004935.
  • Vasudevan, A., et al., α2u-globulins mediate manipulation of host attractiveness in Toxoplasma gondii–Rattus novergicus association. The ISME journal, 2015. 9(9): p. 2112.
  • Tan, D., et al., Infection of male rats with Toxoplasma gondii results in enhanced delay aversion and neural changes in the nucleus accumbens core. Proceedings of the Royal Society of London B: Biological Sciences, 2015. 282(1808): p. 20150042.
  • Liu, A., et al., Ventromedial prefrontal cortex stimulation enhances memory and hippocampal neurogenesis in the middle-aged rats. Elife, 2015. 4: p. e04803.
  • Kumar, V., et al., Sexual attractiveness in male rats is associated with greater concentration of major urinary proteins. Biology of reproduction, 2014. 91(6): p. 150, 1-7.
  • Hari Dass, S.A. and A. Vyas, Toxoplasma gondii infection reduces predator aversion in rats through epigenetic modulation in the host medial amygdala. Molecular ecology, 2014. 23(24): p. 6114-6122.