Publications in peer-reviewed journals

Tong, M. T., Peace, S. T., & Cleland, T. A. (2014). Properties and mechanisms of olfactory learning and memory. Frontiers in behavioral neuroscience8.

Find the original at Frontiers in Behavioral Neuroscience or click here to download a pdf.

ABSTRACT: Memories are dynamic physical phenomena with psychometric forms as well as characteristic timescales. Most of our understanding of the cellular mechanisms underlying the neurophysiology of memory, however, derives from one-trial learning paradigms that, while powerful, do not fully embody the gradual, representational, and statistical aspects of cumulative learning. The early olfactory system—particularly olfactory bulb—comprises a reasonably well-understood and experimentally accessible neuronal network with intrinsic plasticity that underlies both one-trial (adult aversive, neonatal) and cumulative (adult appetitive) odor learning. These olfactory circuits employ many of the same molecular and structural mechanisms of memory as, for example, hippocampal circuits following inhibitory avoidance conditioning, but the temporal sequences of post-conditioning molecular events are likely to differ owing to the need to incorporate new information from ongoing learning events into the evolving memory trace. Moreover, the shapes of acquired odor representations, and their gradual transformation over the course of cumulative learning, also can be directly measured, adding an additional representational dimension to the traditional metrics of memory strength and persistence. In this review, we describe some established molecular and structural mechanisms of memory with a focus on the timecourses of post-conditioning molecular processes. We describe the properties of odor learning intrinsic to the olfactory bulb and review the utility of the olfactory system of adult rodents as a memory system in which to study the cellular mechanisms of cumulative learning.

Manuscripts in preparation

Tong, M. T., Kim, P. T-Y., & Cleland, T. A. (In prep). TrkB activity in the olfactory bulb is needed for consolidation of long-term, but not short-term memories. Targeted for submission to Journal of Physiology. 

Abstract: Understanding the molecular mechanisms underlying long-term memory (LTM) has been a long- standing goal in neuroscience. It is well established that, for one-trial fear conditioning, LTM requires protein synthesis whereas short-term memory (STM) does not. While specific proteins have been identified as crucial for LTM consolidation, what remains unclear is the differential involvement of these mechanisms in STM and LTM for multi-trial appetitive learning. In the present study, mice were trained over several trials to learn an odour-reward association and memory was probed 2 or 48 hours later. Mice were given olfactory bulb (OB)-specific infusions of BDNF receptor antagonist, K252a, immediately prior to training. We found that mice given k252a did not differ from control in learning rate, but showed impaired memory when tested 48 hours, but not 2 hours, after training. This finding suggests that early, post-learning activation of the BDNF-TrkB pathway in the OB is necessary for the consolidation of OB-dependent LTMs. Further, it is a first demonstration of a mechanistic dissociation between STM and LTM pathways for a multi-trial learning task.

Tong, M. T., Mandairon, N., Singh, R., Gibson, E.L., Martinez, C. R., Lee, F.S., & Cleland, T. A. (In prep). The role of the BDNF-TrkB pathway in odour representation specificity.

Abstract: Traditional studies in behavioral neuroscience have used test/pre-test comparisons of measures like latency, digging time, or percent correct as metrics of learning or memory retention. Decreases in performance on these metrics that result from some pharmacological or viral disruption of specific molecular mechanisms show that those mechanisms are necessary for learning. While these metrics are strong binary reporters of learning (whether something was acquired or not), they fail to provide insight into the shape or form of the learned representation. In fact, very little is known about the relationship between the activity of molecular mechanisms and the characteristics of the learned representations that they supposedly underlie. In the present study, we examined the relationship of brain-derived neurotrophic factor (BDNF) activity to the specificity of learned representations of reward-associated odors. We trained mice that bdnf heterozygote or had the Val66Met substitution on the bdnf gene on an olfactory generalization task that allowed us to measure the form of odor representations behaviorally. We found that only bdnf heterozygotes formed non-specific odor representations compared to wild-type mice. In another experiment, we found that olfactory-bulb infusions of a BDNF receptor antagonist, K252a, did not prevent the formation of specific representations. Together, the results suggest that whole-brain, developmental deficits, not acute deficits, in the amount of BDNF inhibits the ability to form specific odor representations.

Tong, M. T., Raghavan, M., Pleiss, J. A., & Cleland, T. A. (In prep). Timecourse of plasticity-related activity following associative learning.

Tong, M. T. (In prep). The goals and motivations of international students in engineering: implications for graduate mentorship practices. Targeted for submission to the Journal of Engineering Education.

Abstract: As the population of international students (IS) at North American universities grows rapidly, educators are faced with the task of figuring out how the academy will accommodate the changing student landscape. This is particularly true for engineering and other technology-related fields. At the graduate level, the student-advisor relationship is an important basis for research productivity. However, misalignments between the goals and expectations of IS and their advisors can lead to low productivity. In the present study, faculty and international PhD students from the Department of Engineering at a large research university were interviewed. IS were asked about their motivations for pursuing research in the U.S., major hindrances to current productivity, and concerns for post-graduation career goals. Faculty were asked about their understanding of the same issues for international students. Major differences exist between IS reports and faculty perceptions. Crucially, IS cited present and future visa status as a major hin- drance to current research productivity and career goals. Faculty advisors, however, do not appear to be aware of the influence of visa status and instead report that language proficiency is the major hindrance. The findings inform better mentorship practices for international students in research-driven doctoral programs.

Projects in progress

Tong, M. T., Singh, R., Martinez, C.R. & Cleland, T. A. (In progress). TrkB inhibition prevents OB-dependent odour habituation. 

Submitted abstracts and conference presentations

2014 Tong MT, Kim T-YP, Gibson EL, Singh R, Cleland TA. The role of BDNF- TrkB signaling in olfactory bulb-dependent olfactory memory. Society for Neuroscience. Washington DC, USA, November 15-19, 2014. 

2014 Tong MT, Cleland TA. TrkB receptor activity in the olfactory bulb is needed for long-term memory of odour-reward learning. Canadian Association for Neuroscience 2014. Montreal QB, Canada, May 25-28, 2014.

2014 Tong MT. Long-term goals of international students in the American Univeristy: Implications for faculty mentorship. Center for Teaching Excellence: Teaching as Research Conference. Ithaca, NY, USA, May 16, 2014.

2013 Tong MT, Cleland TA. Olfactory bulb as model system for the cellular and molecular dissection of memory. Society for Neuroscience. San Diego CA, USA, November 9-13, 2013.

2012 Tong MT, Cleland TA. Role of brain-derived neurotrophic factor (BDNF) in the olfactory long-term memory persistence. Frontiers in Life Science. Ithaca NY, USA, April 2-3, 2012.

2012 Cleland TA, Tong MT, Wie BJ, Zimering JH. Mechanisms of intrinsic learning within olfactory bulb. XVI International Sympolsium on Olfaction and Taste. Stockholm, Sweden, June 23-27, 2012.

2011 Tong MT, Cleland TA. Role of brain-derived neurotrophic factor (BDNF) secretion inneurogenesis-dependent olfactory consolidation. Society for Neu- roscience. Washington DC, USA, November 12-16, 2011.

2010 Tong MT. Cross-cultural examination of the use of affect as information in evaluative judgments. Inquiry@Queen’s Research Conference. Kingston, ON, Canada, March 7-9, 2010.

2009 Troje N, Tong MT, Mensinkai P. Dichotomy in biological motion perception: Pigeons use feet local motion to determine direction. Inquiry@Queen’s Research Conference. Kingston, ON, Canada, March 2-4, 2009.