Hunting Increases Phosphorylation of Calcium/Calmodulin-Dependent Protein Kinase Type II in Adult Barn Owls

Figure 1

Experimental design. (a) Left, diagram of horizontal section through the L midbrain. Auditory information ascends through the core to the lateral shell of the central nucleus of the inferior colliculus (ICCls) where neurons tuned to distinct values of interaural time difference (ITD) are arranged topographically to form a map. ICCls neurons project to the external nucleus of the inferior colliculus (ICX) which contains a complete map of auditory space. Major postsynaptic targets in ICX are CaMKII+ space-specific neurons. In turn, these project to the optic tectum (OT) where the auditory map aligns with a visual map derived from retinotopic input: i20 = ipsilateral 20 degrees; c20 = contralateral 20 degrees. In both ICX and OT, ipsilateral space is represented in the rostral pole and contralateral space progressively towards the caudal pole. V = ventricle. Middle, auditory (dark oval) and visual (light circle) spatial receptive fields of a neuron in OT before prism mounting (top), immediately after mounting (middle), and two months later after full adaptation (bottom). The auditory spatial receptive field has reorganized to align with the optically displaced visual field. The primary site of plasticity is the ICX. Right, hallmarks of instructive or permissive signals acting at the cellular level within ICX. Instructive signals are expected to produce bimodal effects distributed in patches across rostral ICX, depicted here as multicolor islands. Because prisms do not displace the peripheral visual field, no signal is expected in caudal ICX. In contrast, permissive signals are expected to act across the entire rostrocaudal extent, and with uniform effects at the cellular level, depicted here as constant shading. (b) Developmental timeline of physical features [28, 29] and hearing onset and maturation [30]. Plasticity in juveniles occurs readily with passive feeding on dead mice. After sexual maturity, plasticity in adults requires either active hunting or incremental training. (c) Four experimental groups used in this study: Ctrl (juveniles, no prisms, and active feeding), prism (juveniles, with prisms, and active feeding), passive (adults, with prisms, and passive feeding), and active (adults, with prisms, and active feeding). An example of successful hunting episode recorded with infrared videography is shown on the far right.

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