Psychology, Neuroscience & Behaviour
MCMASTER UNIVERSITY
Friday Talks, spring/summer 2011
WHERE: PC 204
WHEN: Every Friday at 3pm throughout
the summer
Things that I will need from you in preparation for your talk:
- The date on which you wish to present
- The duration of your talk (e.g., 15, 20, 30, 45, 50, 60 min)
- Title of your talk
- Equipment requirements (PC 204 has a ceiling projector hooked up)
GREEN = Confirmed
CYAN = Tentative
YELLOW = Completed
Abstracts
Amanda M. Beer’s Abstract:
Two experiments evaluated the ability of older and younger adults to perceive the three-dimensional (3D) shape of object
surfaces from active touch (haptics). The ages of the older adults ranged from 64 to 84 years, while those of the younger
adults ranged from 18 to 27 years. In Experiment 1, the participants haptically judged the shape of large (20 cm
diameter) surfaces with an entire hand. In contrast, in Experiment 2, the participants explored the shape of small (5 cm
diameter) surfaces with a single finger. The haptic surfaces varied in shape index (Koenderink, Solid shape, 1990;
Koenderink, Image and Vision Computing, 10, 557–564, 1992) from -1.0 to +1.0 in steps of 0.25. For
both types of surfaces (large and small), the participants were able to judge surface shape reliably. The
older participants judgments of surface shape were just as accurate and precise as those of the younger
participants. The results of the current study demonstrate that while older adults do possess reductions in tactile
sensitivity and acuity, they nevertheless can effectively perceive 3D surface shape from haptic exploration.
Alan Cooper’s Abstract:
The inhibitory projection from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO) in
the auditory brainstem is a model system for studying the refinement of inhibitory synapses. During the period of
refinement, immature MNTB-LSO terminals co-release the inhibitory neurotransmitters GABA/glycine and the
excitatory neurotransmitter glutamate. This co-release phenomenon raises questions about how these three
neurotransmitters are packaged and released at immature MNTB terminals.
Recent findings suggest that GABA and glycine are contained in one population of synaptic vesicles and that glutamate
is contained in another, and that these two populations release neurotransmitter differently. The presence of different
calcium sensors on the each population could underlie the differences in release. Here, we looked to see if different
isoforms of the calcium sensor synaptotagmin are present at different synapse types in the developing auditory brainstem.
More specifically, we asked whether there was more than one synaptotagmin isoform at MNTB terminals, which release
GABA/glycine and glutamate differently.
We used immunohistochemistry to study the expression of synaptotagmins 1 and 2 at excitatory and inhibitory terminals
in early postnatal rat auditory brainstem. The tissue was imaged using confocal microscopy.
Synaptotagmin 2 is expressed throughout development and is present at both excitatory and inhibitory terminals,
whereas Synaptotagmin 1 is only seen at inhibitory terminals. Moreover, Synaptotagmin 1 is expressed at inhibitory
terminals at the same ages when glutamate is coreleased with GABA/glycine.
Synaptotagmin 2 is likely the calcium sensor at excitatory synapses and at inhibitory synapses that release
GABA/glycine. Synaptotagmin 1 is likely the calcium sensor on vesicles at inhibitory MNTB terminals which transiently
release glutamate during early postnatal life.
Dr. Javier Alamilla’s Abstract:
We know that the nervous system is complex, made up of a very large number of neurons each of which may
communicate with large numbers of other neurons through discrete elements called synapses. But what would happen
if synapses were not discrete? What if there were a population of promiscuous receptors that could be
activated by neurotransmitter released from multiple presynaptic terminals? I will present some of my slice
patch electrophysiology data showing that during a period of circuit refinement in the auditory brainstem,
glutamate ”spills over” to receptors outside the synapse. I will talk about how glutamate spillover onto
promiscuous NMDA receptors might allow excitatory and inhibitory synapses to talk to each other and I will
discuss our current thinking about possible functions of glutamate spillover in developmental plasticity.
Cara Tigue’s Abstract:
Across species, fluctuating asymmetry reflects an individuals ability to resist stressors during development, advertising
underlying mate quality. Previous studies found that symmetric human faces are more attractive and sex-typical than are
less symmetric faces. Female facial masculinity is positively correlated with vocal masculinity and both are cues to
underlying testosterone levels. Generally, higher-pitched womens voices are more attractive than lower-pitched womens
voices. Two previous studies demonstrated that women with more symmetrical bodies have more attractive voices, but it
is unknown if fluctuating asymmetry relates to voice pitch. The purpose of this study was to determine if voice
pitch is related to facial fluctuating asymmetry. We measured facial fluctuating asymmetry in 3D and
measured voice pitch from three different speech types. As predicted, women with more symmetrical faces had
higher-pitched voices. This result helps explain why prior work shows that more symmetrical women have
more attractive voices. Our results are the first evidence that facial symmetry is related to voice pitch,
demonstrating that different cues to mate quality work together to advertise an individuals overall fitness.
Tom Rzeszutek’s Abstract:
Human cultural traits, such as languages, musics, rituals, and material objects, vary widely across cultures. However, the
majority of comparative analyses of human cultural diversity focus on between-culture variation without consideration
for within-culture variation. In contrast, biological approaches to genetic diversity, such as the Analysis of Molecular
Variance (AMOVA) framework, partition genetic diversity into both within- and between-population components. We
attempt here for the first time to quantify both components of cultural diversity by applying the AMOVA model to
music. By applying this approach to 421 traditional songs from 16 Austronesian-speaking populations, we show that the
vast majority of musical variability is due to differences within populations rather than differences between. This
demonstrates a striking parallel between the structures of cultural and genetic diversity in humans. A
Neighbor-Net analysis of pairwise population musical divergence shows a large amount of reticulation,
indicating the pervasive occurrence of borrowing and/or convergence of musical features across populations.
Pat Savage’s Abstract:
The cross-cultural study of music is essential for a better understanding of the evolution of human biological and cultural
diversity. Early comparative musicologists failed to develop rigorous scientific methods for studying this, and the
modern-day fields of music cognition and ethnomusicology still lack such methods. I will describe our attempts to design
new methods for classifying and quantifying cross-cultural musical diversity and to apply these methods to the study of
musical evolution and migration. Using a new and more reliable method of classifying songs, we analyzed 421 songs
from 16 indigenous tribes in Taiwan and the Philippines. We found striking parallels between musical
and genetic diversity, both in the relative amounts of within- and between-culture diversity and in the
patterns of similarities among the tribes. These findings suggest that music may be subject to similar
processes of evolution and migration as are genes. A new, multidisciplinary, and scientifically-grounded
comparative musicology may thus provide a new line of evidence to complement and integrate research in music
cognition, ethnomusicology, and other fields into the complex relationship between music, biology, and
culture
Adam R. Reddon’s Abstract:
In social animals, group-joining decisions can have important fitness consequences especially when individuals exist in a
dominance hierarchy that relates to reproductive success. Choosing to join a large group may maximize safety but a
small group can minimize the delay to dominant status. We explored this trade-off using Neolamprologus pulcher,
a cooperatively breeding cichlid fish in which individuals conform to a rigid dominance hierarchy and
females are philopatric. We predicted that because females have less opportunity to switch groups, they
would place higher value on social rank than safety. We found that males prefer larger groups regardless
of the rank they must assume when they join while females preferred larger groups only when joining
did not compromise social rank. Our results help to elucidate factors underlying social decision-making
and suggest that females value both rank and safety while males are primarily concerned with safety.
Chris Taylor’s Abstract:
Blur is a fundamental image property; it is important for image quality assessment and in the clinic it is critical for
satisfaction with optical correction. Letter acuity tests and simulations with blurred step edges provide poor measures of
blur because image quality is ultimately evaluated in real scenes. Previous methods for assessing blur do
not address the most common natural causes of image blur outside the laboratory: optical defocus, pupil
diameter, and depth variation. Using an approach that combines improved image metrics, displays that
systematically manipulate accommodation, highly controllable naturalistic stimuli, tools for measuring
depth in natural scenes, and efficient psychophysical testing, we demonstrate how blur sensitivity can be
efficiently quantified in a manner that corresponds to the natural conditions faced by observers in the real
world.
