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Member-Initiated Symposia2012 Symposia Distinguishing perceptual shifts from response biases Human visual cortex: from receptive fields to maps to clusters to perception Neuromodulation of Visual Perception Part-whole relationships in visual cortex Pulvinar and Vision: New insights into circuitry and function What does fMRI tell us about brain homologies?
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Pulvinar and Vision: New insights into circuitry and functionFriday, May 11, 1:00 - 3:00 pm Organizer: Vivien A. Casagrande, PhD, Department of Cell & Developmental Biology, Vanderbilt Medical School Nashville, TN
Symposium DescriptionThe thalamus is considered the gateway to the cortex. Yet, even the
late Ted Jones who wrote two huge volumes on the organization of the thalamus
remarked that we know amazingly little about many of its components and their
role in cortical function. This is despite the fact that a major two-way
highway connects all areas of cortex with the thalamus. The pulvinar is the
largest thalamic nucleus in mammals; it progressively enlarged during primate
evolution, dwarfing the rest of the thalamus in humans. The pulvinar also
remains the most mysterious of thalamic nucleus in terms of its function. This
symposium brings together six speakers from quite different perspectives who,
using tools from anatomy, neurochemistry, physiology, neuroimaging and behavior
will highlight intriguing recent insights into the structure and function of
the pulvinar. The speakers will jointly touch on: 1) the complexity of
architecture, connections and neurochemistry of the pulvinar, 2) potential
species similarities and differences in pulvinar’s role in transmitting visual
information from subcortical visual areas to cortical areas, 3) the role of
pulvinar in eye movements and in saccadic suppression, 4) the role of pulvinar
in regulating cortico-cortical communication between visual cortical areas and
finally, 5) converging ideas on the mechanisms that might explain the
role of the pulvinar under the larger functional umbrella of visual salience
and attention. Specifically, the speakers will address the following
issues. Purushothaman and Casanova will outline contrasting roles for
pulvinar in influencing visual signals in early visual cortex in primates and
non- primates, respectively. Petry and Wurtz will describe the
organization and the potential role of retino-tectal inputs to the pulvinar,
and that of pulvinar projections to the middle temporal (MT/V5) visual area in
primate and its equivalent in non-primates. Wurtz also will consider the role
of pulvinar in saccadic suppression. Kastner will describe the role of
the pulvinar in regulating information transfer between cortical areas in
primates trained to perform an attention task. Whitney will examine the role of
pulvinar in human visual attention and perceptual discrimination.
This symposium should attract a wide audience from Visual Science Society (VSS)
participants as the function of the thalamus is key to understanding cortical
organization. Studies of the pulvinar and its role in vision have seen a
new renaissance given the new technologies available to reveal its function.
The goal of this session will be to provide the VSS audience with a new
appreciation of the role of the thalamus in vision. Presentations Gating of the Primary Visual Cortex by Pulvinar for Controlling Bottom-Up
Salience
Gopathy Purushothaman, PhD, Department of Cell &
Developmental Biology Vanderbilt, Roan Marion, Keji Li and Vivien A. Casagrande
Vanderbilt University The thalamic nucleus pulvinar has been implicated in the control of
visual attention. Its reciprocal connections with both frontal and
sensory cortices can coordinate top-down and bottom-up processes for selective
visual attention. However, pulvino-cortical neural interactions are
little understood. We recently found that the lateral pulvinar (PL)
powerfully controls stimulus-driven responses in the primary visual cortex
(V1). Reversibly inactivating PL abolished visual responses in
supra-granular layers of V1. Excitation of PL neurons responsive to one
region of visual space increased 4-fold V1 responses to this region and
decreased 3-fold V1 responses to the surrounding region. Glutamate agonist
injection in LGN increased V1 activity 8-fold and induced an excitotoxic lesion
of LGN; subsequently injecting the glutamate agonist into PL increased V1
activity 14-fold. Spontaneous activity in PL and V1 following visual
stimulation were strongly coupled and selectively entrained at the stimulation
frequency. These results suggest that PL-V1 interactions are well-suited
to control bottom-up salience within a competitive cortico-pulvino-cortical
network for selective attention. Is The Pulvinar Driving or Modulating Responses in the Visual Cortex?
Christian Casanova, PhD, Univ. Montreal, CP 6128 Succ
Centre-Ville, Sch Optometry, Montreal , Canada, Matthieu Vanni & Reza F. Abbas
& Sébastien Thomas. Visual Neuroscience Laboratory, School of Optometry,
Université de Montréal, Montreal, Canada Signals from lower cortical areas are not only transferred directly to
higher-order cortical areas via cortico-cortical connections but also
indirectly through cortico-thalamo-cortical projections. One step toward the
understanding of the role of transthalamic corticocortical pathways is to
determine the nature of the signals transmitted between the cortex and the
thalamus. Are they strictly modulatory, i.e. are they modifying the activity in
relation to the stimulus context and the analysis being done in the projecting
area, or are they used to establish basic functional characteristics of
cortical cells? While the presence of drivers and modulators has been
clearly demonstrated along the retino-geniculo-cortical pathway, it is not
known whether such distinction can be made functionally in pathways involving
the pulvinar. Since drivers and modulators can exhibit a different temporal
pattern of response, we measured the spatiotemporal dynamics of voltage
sensitive dyes activation in the visual cortex following pulvinar electrical
stimulation in cats and tree shrews. Stimulation of pulvinar induced fast and
local responses in extrastriate cortex. In contrast, the propagated waves in
the primary visual cortex (V1) were weak in amplitude and diffuse.
Co-stimulating pulvinar and LGN produced responses in V1 that were weaker than
the sum of the responses evoked by the independent stimulation of both nuclei.
These findings support the presence of drivers and modulators along pulvinar
pathways and suggest that the pulvinar can exert a modulatory influence in
cortical processing of LGN inputs in V1 while it mainly provides driver inputs
to extrastriate areas, reflecting the different connectivity patterns. What is the role of the pulvinar nucleus in visual motion processing?
Heywood M. Petry, Department of Psychological & Brain Sciences,
University of Louisville, Martha E. Bickford, Department of Anatomical Sciences
and Neurobiology, University of Louisville School of Medicine To effectively interact with our environment, body movements must be
coordinated with the perception of visual movement. We will present evidence
that regions of the pulvinar nucleus that receive input from the superior
colliculus (tectum) may be involved in this process. We have chosen the tree
shrew (Tupaia belangeri, a prototype of early primates), as our animal model
because tectopulvinar pathways are particularly enhanced in this species, and
our psychophysical experiments have revealed that tree shrews are capable of
accurately discriminating small differences in the speed and direction of
moving visual displays. Using in vivo electrophysiological recording techniques
to test receptive field properties, we found that pulvinar neurons are
responsive to moving visual stimuli, and most are direction selective. Using
anatomical techniques, we found that tectorecipient pulvinar neurons project to
the striatum, amygdala, and temporal cortical areas homologous to the primate
middle temporal area, MT/V5. Using in vitro recording techniques,
immunohistochemistry and stereology, we found that tectorecipient pulvinar
neurons express more calcium channels than other thalamic nuclei and thus
display a higher propensity to fire with bursts of action potentials,
potentially providing a mechanism to effectively coordinate the activity of
cortical and subcortical pulvinar targets. Collectively, these results suggest
that the pulvinar nucleus may relay visual movement signals from the superior
colliculus to subcortical brain regions to guide body movements, and
simultaneously to the temporal cortex to modify visual perception as we move
though our environment. One message the pulvinar sends to cortexRobert H. Wurtz, NIH-NEI, Lab of Sensorimotor Research, Rebecca
Berman, NIH-NEI, Lab of Sensorimotor Research The pulvinar has long been recognized as a way station on a second
visual pathway to the cerebral cortex. This identification has largely been
based on the pulvinar’s connections, which are appropriate for providing visual
information to multiple regions of visual cortex from subcortical areas. What
is little known is what information pulvinar actually conveys especially in the
intact functioning visual system. We have identified one pathway through
the pulvinar that extends from superior colliculus superficial visual layers
though inferior pulvinar (principally PIm) to cortical area MT by using the
techniques of combined anti- and orthodromic stimulation. We now have explored
what this pathway might convey to cortex and have first concentrated on a
modulation of visual processing first seen in SC, the suppression of visual
responses during saccades. We have been able to replicate the previous
observations of the suppression in SC and in MT and now show that PIm neurons
also are similarly suppressed. We have then inactivated SC and shown that
the suppression in MT is reduced. While we do not know all of the signals
conveyed through this pathway to cortex, we do have evidence for one: the
suppression of vision during saccades. This signal is neither a visual nor a
motor signal but conveys the action of an internal motor signal on visual
processing. Furthermore combining our results in the behaving monkey with
recent experiments in mouse brain slices (Phongphanphanee et al. 2011) provides
a complete circuit from brainstem to cortex for conveying this suppression. Role of the pulvinar in regulating information transmission between cortical areasSabine Kastner, MD, Department of Psychology, Center for
Study of Brain, Mind and Behavior, Green Hall, Princeton, Yuri B. Saalman,
Princeton Neuroscience Institute, Princeton University Recent studies suggest that the degree of neural synchrony between
cortical areas can modulate their information transfer according to attentional
needs. However, it is not clear how two cortical areas synchronize their
activities. Directly connected cortical areas are generally also indirectly
connected via the thalamic nucleus, the pulvinar. We hypothesized that the
pulvinar helps synchronize activity between cortical areas, and tested this by
simultaneously recording from the pulvinar, V4, TEO and LIP of macaque monkeys
performing a spatial attention task. Electrodes targeted interconnected sites
between these areas, as determined by probabilistic tractography on diffusion
tensor imaging data. Spatial attention increased synchrony between the cortical
areas in the beta frequency range, in line with increased causal influence of
the pulvinar on the cortex at the same frequencies. These results suggest that
the pulvinar co-ordinates activity between cortical areas, to increase the
efficacy of cortico-cortical transmission. Visual Attention Gates Spatial Coding in the Human PulvinarDavid Whitney, The University of California, Berkeley, Jason Fischer,
The University of California, Berkeley
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