![]() The first hypothesis explains the pattern by rhythmic drive to the HVC RA neurons from an afferent nucleus, based on studies suggesting temporal structuring originating from the Uva (nucleus uvaeformis) or NIf (nucleus interface of the nidopallium) (McCasland 1987 Williams and Vicario 1993 Vu et al. How the HVC RA neurons are able to generate the activity pattern with sub-millisecond precision can be explained by two different approaches. During singing the HVC neurons projecting to RA (HVC RA) show bursting activity that is time locked with sub-millisecond precision to the stereotyped song motif (Hahnloser et al. Temporal coding not only of the song elements but on all timescales (motif, syllable, note) is located in the HVC, whilst the RA serves to encode the HVC commands into firing rates suitable for the muscles needed to control the vocal output (Yu and Margoliash 1996 Fee et al. Recent results using moderate local cooling (Long and Fee 2008 Glaze and Troyer 2008) have changed our understanding of this motor pathway. These experimental findings suggest an auditory reafferent signal to be necessary for the generation of correct song syntax.Įarly experimental studies on the songbird suggested that HVC neurons projecting to the pre-motor nucleus RA (robust nucleus of the arcopallium) only encode for the temporal structure within the song and that a sequence of fixed motor commands is replayed within the RA (Yu and Margoliash 1996 Hahnloser et al. More recently, studies have demonstrated that the vocal motor control system of the Bengalese finch relies on real time auditory feedback (Sakata and Brainard 2006) and that the HVC activity (caudal nucleus of the ventral hyperpallium or high vocal center, nowadays used as proper name) is influenced instantaneously by feedback perturbance (Sakata and Brainard 2008). Yamada and Okanoya ( 2003) reported that the song syntax is also reversibly changed if the Bengalese finch is singing in a helium atmosphere. They argued that a template of the song exists independently of auditory input. In a subsequent experiment Woolley and Rubel ( 2002) reversibly deafened Bengalese finches and showed that normal vocal behavior can be restored when hearing is restored. the sequence becomes more random and unstable (Okanoya and Yamaguchi 1997, 1997 Woolley and Rubel 1999 Watanabe and Aoki 1998). The Bengalese finch typically produces a set of ordered sequences of syllables, but after deafening this song syntax is disrupted, i.e. Several experimental studies have shown that the song of the Bengalese finch relies on auditory feedback. This study illustrates how sequential compositionality following a defined syntax can be realized in networks of spiking neurons. The model also reproduces for the first time experimental findings on the influence of altered auditory feedback on the song syntax generation, and predicts song- and species-specific low frequency components in the LFP. Both imprinting of song syntax within HVC and the interaction of the reafferent signal with an efference copy of the motor command are sufficient to explain the gradual loss of syntax in the absence of auditory feedback. Propagating synfire activity in the HVC codes for individual syllables of the song and priming signals from the auditory network reduce the competition between syllables to allow only those transitions that are permitted by the syntax. We present a spiking neuronal network model of the song syntax generation and its loss, based on the assumption that the syntax is stored in reafferent connections from the auditory to the motor control area. The syntax is gradually lost over a period of days after deafening and is recovered when hearing is restored. ![]() Adult Bengalese finches generate a variable song that obeys a distinct and individual syntax.
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