Biomedical subjects

Daniel Margoliash

Publications and source records attributed to Daniel Margoliash.

4 recordsLinked to original sources

PubMed2003

Neuronal populations and single cells representing learned auditory objects.

The neural representations associated with learned auditory behaviours, such as recognizing individuals based on their vocalizations, are not well described. Higher vertebrates learn to recognize complex conspecific vocalizations that comprise sequences of easily identified, naturally occurring auditory objects, which should facilitate the analysis of higher auditory pathways. Here we describe the first example of neurons selective for learned conspecific vocalizations in adult animals--in starlings that have been trained operantly to recognize conspecific songs. The neuronal population is found in a non-primary forebrain auditory region, exhibits increased responses to the set of learned songs compared with novel songs, and shows differential responses to categories of learned songs based on recognition training contingencies. Within the population, many cells respond highly selectively to a subset of specific motifs (acoustic objects) present only in the learned songs. Such neuronal selectivity may contribute to song-recognition behaviour, which in starlings is sensitive to motif identity. In this system, both top-down and bottom-up processes may modify the tuning properties of neurons during recognition learning, giving rise to plastic representations of behaviourally meaningful auditory objects.

Acoustic Stimulation↗

PubMed2003

State and neuronal class-dependent reconfiguration in the avian song system.

Sensory systems may adapt to behavioral requirements through state-dependent changes. In the forebrain song-system nucleus HVc of zebra finches, state-dependent auditory responses have been described in multiunit recordings. Here we report on behavioral state-dependent changes in the activity of distinct HVc neuronal classes. HVc projection neurons were identified by electrically stimulating HVc's target nuclei, the robust nucleus of the archistriatum and Area X, in anesthetized zebra finches. Projection neurons and two classes of putative interneurons could be distinguished on the basis of extracellular spike waveforms, with the first two factors of a principal components analysis accounting for 81% of the variance in spike morphometric values. Spike width was the best single variable for distinguishing among the neuronal classes. Putative interneurons had much higher firing rates spontaneously and in response to song than did projection neurons, which had extremely low spontaneous rates and phasic responses to song. Recordings from HVc in behaving animals were dominated by the two classes of putative interneurons. Both classes showed strong, selective, and temporally similar auditory responses during sleep, but only one class of interneurons reliably maintained auditory responses on waking. These responses were weaker and less selective than those seen during sleep. The observation that HVc auditory responsiveness in awake zebra finches is restricted to some classes of neurons may help explain prior multiunit results that suggested nearly complete suppression of HVc auditory responses in awake birds. We propose that the heterogeneous effects of behavioral state on distinct subpopulations of HVc neurons allow HVc to participate in multiple roles during song production, conspecific song recognition, and possibly memory consolidation during sleep.

Action Potentials↗

PubMed2002

Metabolic and neural activity in the song system nucleus robustus archistriatalis: effect of age and gender.

The sexually dimorphic robust archistriatal nucleus (RA) represents the telencephalic output of the bird song system. Here, we document sex-dependent changes in both the metabolic and neuronal activity of RA during the sensory and sensorimotor phases of song learning. From posthatching day (PHD) 20-63 in males but not females, RA and its input nucleus HVc showed sharp increases in cytochrome oxidase (CO) activity relative to surrounding archistriatum and the underlying shelf, respectively. In urethane-anesthetized birds, during the same period, the spontaneous activity of male RA neurons underwent dramatic changes in firing rate, distribution of interspike intervals, and bursting frequency, compared with other archistriatal cells. At PHD 20-21, RA neurons had extremely slow, irregular firing rates in birds of both sexes. In males, from PHD 30-36, RA neurons increased their firing rates and spiking activity became more regular, and at approximately PHD 38, strong bursts followed by inhibition (which in awake animals is associated with singing) began to be observed. Dual recordings from RA and HVc revealed synchronous bursting, with RA spikes lagging approximately 10 msec behind HVc. We conclude that changes in relative CO activity correlate with changes in spontaneous firing rates within RA and that patterns of RA spontaneous activity exhibit gradual change as birds enter early song and then again for plastic song. The emergence of strong burst patterns in RA occurs later in life than does input from HVc as established by tracer studies or based on observed HVc bursting in young animals.

Action Potentials↗

PubMed2002

Motor control of birdsong.

One of the challenges when considering the motor control of birdsong is to understand how such a wide variety of temporally and spectrally diverse vocalizations are learned and produced. A better understanding of central neural processing, together with direct endoscopic observations and physiological studies of peripheral motor function during singing, has resulted in the formation of new theoretical models of song production. Recent work suggests that it may be more profitable to focus on the temporal relationship between control parameters than to attempt to directly correlate neural processing with details of the acoustic output.

Animals↗