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Enduring forms of synaptic plasticity are thought to require ongoing regulation of adhesion molecules, such as N-cadherin, at synaptic junctions. Little is known about the activity-regulated trafficking of adhesion molecules. Here we demonstrate that surface N-cadherin undergoes a surprisingly high basal rate of internalization. Upon activation of NMDA(More)
Categorization is the process by which the brain segregates continuously variable stimuli into discrete groups. We report that patterns of neural population activity in the owl optic tectum (OT) categorize stimuli based on their relative strengths into "strongest" versus "other." The category boundary shifts adaptively to track changes in the absolute(More)
Stimulus selection for gaze and spatial attention involves competition among stimuli across sensory modalities and across all of space. We demonstrate that such cross-modal, global competition takes place in the intermediate and deep layers of the optic tectum, a structure known to be involved in gaze control and attention. A variety of either visual or(More)
Essential to the selection of the next target for gaze or attention is the ability to compare the strengths of multiple competing stimuli (bottom-up information) and to signal the strongest one. Although the optic tectum (OT) has been causally implicated in stimulus selection, how it computes the strongest stimulus is unknown. Here, we demonstrate that OT(More)
A midbrain network interacts with the well-known frontoparietal forebrain network to select stimuli for gaze and spatial attention. The midbrain network, containing the superior colliculus (SC; optic tectum, OT, in non-mammalian vertebrates) and the isthmic nuclei, helps evaluate the relative priorities of competing stimuli and encodes them in a topographic(More)
The mechanisms by which the brain selects a particular stimulus as the next target for gaze are poorly understood. A cholinergic nucleus in the owl's midbrain exhibits functional properties that suggest its role in bottom-up stimulus selection. Neurons in the nucleus isthmi pars parvocellularis (Ipc) responded to wide ranges of visual and auditory features,(More)
Reciprocal inhibition between inhibitory projection neurons has been proposed as the most efficient circuit motif to achieve the flexible selection of one stimulus among competing alternatives. However, whether such a motif exists in networks that mediate selection is unclear. Here, we study the connectivity within the nucleus isthmi pars magnocellularis(More)
Structural changes at synapses are thought to be a key mechanism for the encoding of memories in the brain. Recent studies have shown that changes in the dynamic behavior of dendritic spines accompany bidirectional changes in synaptic plasticity, and that the disruption of structural constraints at synapses may play a mechanistic role in spine plasticity.(More)
In a natural scene, multiple stimuli compete for the control of gaze direction and attention. The nucleus isthmi pars parvocellularis (Ipc) is a cholinergic, midbrain nucleus that is reciprocally interconnected to the optic tectum, a structure known to be involved in the control of gaze and attention. Previous research has shown that the responses of many(More)
Dendritic spines are one-half (the postsynaptic half) of most excitatory synapses. Ever since the direct observation over a decade ago that spines can continually change size and shape, spine dynamics has been of great research interest, especially as a mechanism for structural synaptic plasticity. In concert with this ongoing spine dynamics, the stability(More)