Ruge, O. | bioRxiv Science

bioRxiv2025

Norepinephrine acts through radial astrocytes in the developing optic tectum to enhance threat detection and escape behavior

The ability to switch behavioral states is essential for animals to adapt and survive. We investigated how norepinephrine (NE) activation of radial astrocytes alters visual processing in the optic tectum (OT) of developing Xenopus laevis. NE activates calcium transients in radial astrocytes through 1-adrenergic receptors. NE and radial astrocyte activation shifted OT response selectivity to preferentially respond to looming stimuli, associated with predation threat. NE-mediated astrocytic release of ATP/adenosine reduced excitatory transmission by retinal ganglion cell axons, without affecting inhibitory transmission in the OT. Blockade of adenosine receptors prevented both decreased neurotransmission and the selectivity shift. Chemogenetic activation of tectal radial astrocytes reproduced NEs effects and enhanced behavioral detection of looming stimuli in freely swimming animals. NE signaling via radial astrocytes enhances network signal-to-noise for detecting threatening stimuli, with important implications for sensory processing and behavior.

neuroscience↗

bioRxiv2024

Temporal variability enhances vocal learning

Species-typical behaviors are organized into species-typical patterns, and deviations away from these patterns often diminish the strength of behavioral and sensory responses to such stimuli. In songbirds like the zebra finch, species-typical songs consist of acoustic elements (syllables) arranged into stereotyped (i.e., highly predictable) sequences with stereotyped timing. However, the degree to which deviations away from these stereotyped temporal patterns modulate the strength of vocal learning (i.e., the fidelity of vocal imitation) remains unknown. Here we tutored 123 juvenile zebra finches with stimuli that varied in the stereotypy of syllable sequencing and timing. In contrast to the prediction that deviations away from species-typical stereotypy would diminish vocal learning, deviations from sequence or timing stereotypy did not decrease how well juveniles imitated the acoustic structure of syllables. Moreover, presenting syllables in species-atypical sequences (i.e., randomized syllable sequences) enhanced vocal imitation in birds that were tutored later in development. This unexpected enhancement of birdsong learning by sequence variability resembles the effects of contextual diversity on speech acquisition and indicates that such variability can benefit learning even for very stereotyped behaviors. SIGNIFICANCE STATEMENTLittle is known about the degree to which the temporal patterning of acoustic elements ("syllables") modulates vocal learning and imitation. We tested the contribution of temporal variability in syllable sequencing and timing, hypothesizing that deviations away from species-typical stereotypy (predictability) in syllable sequence and timing patterns would diminish the strength of vocal learning. In contrast to our predictions, deviations from sequence and timing stereotypy did not decrease vocal learning. Moreover, presenting syllables in random sequences enhanced vocal imitation in birds that were tutored later in development. This unexpected finding highlights that sequence complexity can potentiate vocal learning in individuals with more developed vocal control, resembling how complexity and ability interact to modulate various forms of learning in humans.

animal behavior and cognition↗