Events held in Sunburst Room unless otherwise noted.

Friday, November 2

Saturday, November 3

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Abstracts

Julie Fiez, Ph.D.

Title: Reading Faces: Using Artificial Orthographies to Study the Neural Basis of Reading
Abstract: Does the neural network for reading have the flexibility to accommodate an alphabet consisting of faces as letters? We investigated the functional role of the visual word form area (VWFA), a left-lateralized brain region that processes written words, by training participants to read a “FaceFont” alphabet in which faces are paired with English sounds. Using functional imaging, we showed that the VWFA responded to FaceFont words in trained participants while areas typically associated with face processing did not show a response that varied with training. The response magnitude in the VWFA correlated with behavioral reading performance, providing strong evidence that the neural tissue recruited by training supported the newly acquired reading skill. These results indicate that involvement of the VWFA is not restricted to stimuli with particular visual-perceptual features. Instead, its recruitment may be governed by the need to connect visual processing with components of the speech system, to permit the construction of a phonological representation that allows access to stored word knowledge.

Aryn Gittis, Ph.D.

Title: Cellular Mechanisms of Synchrony in the Basal Ganglia
Abstract: Synchrony plays an important role in information processing and neural computations in the brain. However, in some neurological disorders such as Parkinson’s disease, the development of excessive synchrony becomes destructive to neural circuit function. Our work studies cellular mechanisms of plasticity that contribute to pathological synchrony in a mouse model of Parkinson’s disease. Dopamine depletion causes a rapid reorganization of local inhibitory circuits in the striatum, the primary input nucleus of the basal ganglia. Fast-spiking interneurons (FSIs) sprout new axons which selectively target projection neurons in the motor-suppressing ‘indirect pathway’, and this plasticity is sufficient to produce aberrant synchrony of indirect-pathway neurons in a computer model of the striatal circuit. In addition, striatal FSIs receive strong inhibitory inputs from neurons in the globus pallidus, called the pallido-striatal pathway. We hypothesize that this understudied pallido-striatal pathways is critical for the amplification and propagation of pathological oscillations following dopamine depletion.

Julie Kauer, Ph.D.

Title: Stress, drugs and the VTA
Abstract: Exposure to stress facilitates the reinstatement of addictive drug-seeking in animals and promotes relapse in humans. Acute stress has marked effects on plasticity at both inhibitory and excitatory synapses on dopamine neurons in the ventral tegmental area (VTA), a key region necessary for drug reinforcement. Stress blocks long-term potentiation at GABAergic synapses on dopamine neurons in the VTA (LTP_GABA), potentially removing a normal brake on activity. We have now found that blocking kappa opioid receptors (KORs) prior to a stressful experience rescues LTP_GABA.  In contrast, blocking KORs does not prevent stress-induced potentiation of excitatory synapses or the morphine-induced block of LTP_GABA.  We used a kappa receptor antagonist as a selective tool to test the role of LTP_GABAin vivo, and find that blocking KORs within the VTA prior to acute stress prevents reinstatement to cocaine-seeking in rats.  These results suggest that KORs may represent a useful therapeutic target for treatment of stress-triggered relapse in substance abuse.

Sandra Kuhlman, Ph.D.

Title: A disinhibitory microcircuit initiates critical period plasticity in visual cortex
Abstract: Sensory experience in early life profoundly changes the maturation of neural circuit structure and function in cortex. However, the specific changes that initiate functional plasticity remain obscure. We find that, in alert mice, visually evoked responses of pyramidal neurons in layer 2/3 (L2/3) of primary visual cortex drop by half immediately following unilateral lid suture, but are restored within the first 24 hours thereafter. These increased excitatory responses result from a profound loss of inhibition normally provided by fast-spiking, parvalbumin-positive (PV) inhibitory neurons in the upper layers of visual cortex. The data that I will present identify the initial experience-dependent changes in cortical microcircuitry unique to the critical period, and show that the rapid restoration of evoked firing rates of L2/3 pyramidal neurons is a key first step in the progression of competitive ocular dominance plasticity.

Anne-Marie Oswald-Doiron, Ph.D.

Title: Excitatory and inhibitory synaptic contributions to responses in the piriform cortex  
Abstract: Understanding how neural and behavioral timescales interact to influence cortical activity and stimulus coding is an important issue in sensory neuroscience.  In air-breathing animals, voluntary changes in respiratory frequency alter the temporal patterning olfactory input.  In the olfactory bulb, these behavioral timescales are reflected in the temporal properties of mitral/tufted (M/T) cell spike trains. As the odor information contained in these spike trains is relayed from the bulb to the cortex, the recruitment of synaptic excitation and inhibition influences how stimuli are represented by cortical activity.  Here we demonstrate how the timescales associated with respiratory frequency, spike timing and short-term plasticity at excitatory synapses interact to shape cortical spike train responses.  We also show the contributions of feed forward and recurrent excitatory synapses to cortical population activity in response to inputs delivered at respiratory frequencies. Finally, we will present new data from investigations of the recruitment of inhibitory synaptic inputs onto pyramidal cells and interneurons in the piriform cortex.

Charles Perfetti, Ph.D.

Title: Saving Faces: The accommodation of reading procedures to writing systems and orthographies (and languages)
Abstract: Reading adapts to the variety of written languages through a universal constraint on writing systems and through the accommodation of reading procedures (and thus the brain’s reading network) to the specific features of a writing system and its orthography. Both cross-linguistic studies of reading development and studies of second language learning suggest that reading experience in a given language and its writing system leads to increased specialization of the brain’s reading network. I illustrate an implication of these general conclusions with recent studies of second language learning of Chinese. These studies show that acquiring orthographic components of a new system can be accelerated through writing while learning to read, which produces writing-system specific effects on sensory-motor and visual-spatial components of the brain’s reading network.

David Plaut, Ph.D.

Title: The interdependence of face and word processing: Behavioral, neural, and computational considerations
Abstract: Face and word recognition are commonly thought to be subserved by two functionally independent modules located in the fusiform face area (FFA) in the right hemisphere and the visual word form area (VWFA) in the left hemisphere, respectively. The current research proposes instead that visual recognition is supported, not by dedicated modules, but by highly distributed and interactive cortical networks whose organization reflects a set of general principles and constraints on neural computation. The consequences of these principles go beyond explaining why the functional specialization of the FFA and VWFA is graded rather than absolute. They also lead to otherwise unexpected predictions---tested in the current work with a combination of computational, behavioral, and neuroimaging studies---concerning the partial co-mingling of face and word processing.

Linda Rinaman, Ph.D.

Title: Systems-level analysis of neural circuit development using transsynaptic viral tracing
Abstract: The development of neuronal projections to a target and the establishment of synaptic connections can be temporally distinct events. To characterize the postnatal development of limbic forebrain synaptic inputs to hindbrain and spinal autonomic neurons, we used pseudorabies virus (PRV), a neurotropic alpha herpesvirus that moves across synapses in the retrograde direction. Transneuronal labeling of central pre-autonomic neurons was achieved by inoculating the ventral stomach wall with PRV in rat pups on postnatal day 1 (P1), P4, or P8, and sacrificing the rats 2.5 days later. In each age group, PRV-positive neurons were present in autonomic and pre-autonomic regions of the thoracic spinal cord and caudal brainstem. Transneuronal forebrain labeling in rats injected on P8 was similar to labeling achieved in adult rats, and included neurons in the medial and lateral hypothalamus, central amygdala, anterior bed nucleus of the stria terminalis, insular cortex, and medial prefrontal cortex. However, no cortex labeling and only modest amygdala and bed nucleus labeling were observed in rats injected with PRV on P4, and only medial hypothalamic labeling was observed in rats injected on P1. A subsequent experiment demonstrated that the development of forebrain pre-autonomic circuits was delayed in rat pups exposed from P1-10 to daily maternal separation, evidence that early life experience can impact the formation of neural circuits that provide limbic and cortical control over autonomic emotional motor output.

Rob Turner, Ph.D.

Title: The Basal Ganglia and Motor Skill
Abstract: What does the basal ganglia contribute to normal motor function? Current hypotheses range from a preferential involvement of the basal ganglia in initial learning of motor skills to being the locus for long-term storage and recall of well-learned motor "habits." In a series of studies of sequence learning in non-human primates, we have found support for the idea that the skeletomotor-related circuit of the basal ganglia plays a key role in the execution of recently-learned skills, but no evidence that this circuit is critical for the retention or recall of well-learned skills. Our results fit well with the general theory that basal ganglia circuits facilitate the acquisition of adaptive behaviors in novel contexts, but that other brain regions take over the control of well-learned skills and procedures.

Timothy Verstynen, Ph.D.

Title: Medial orbitostriatal modulations of inhibitory control: Check yourself before you rectus yourself
Abstract: The lateral and middle orbitofrontal gyri are generally associated with affect regulation, reward processing and inhibitory control. Yet we know very little about the role of the most medial aspects of the orbitofrontal cortex, particularly the rectus gyrus, in cognition.  Applying a structural equation modeling analysis of the trial-by-trial BOLD dynamics during the color-word Stroop task, I show how the rectus gyrus influences the speed of single-trial responses indirectly by modulating responses in a network of lateral frontal and striatal regions.  Using resting state fMRI, I also show that a circuit connecting the rectus gyrus with the head of the caudate is altered in overweight and obese individuals, a segment of the population that also exhibits exaggerated interference during incongruent Stroop trials. In fact, individual differences in the degree of orbitostratial connectivity at rest predicted obesity-linked changes in task-evoked responses during incongruent Stroop trials.  Put together these results suggest that, rather than directly control inhibitory or reward signals, the medial orbitofrontal cortex may act as a modulator of executive control signals through striatal pathways.