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. 2020 Nov 16;23(12):101804. doi: 10.1016/j.isci.2020.101804

Figure 1.

Figure 1

Vocal Pattern Generator Hypotheses, Rat Vocalizations, Stimulation-Evoked Vocalizations, and Local Brainstem Cooling

(A) Competing hypotheses about the mammalian vocal pattern generator superimposed to a schematic mammalian (rat) brainstem. Red areas depict the assumed location of the vocal pattern generator. Left: nucleus retroambiguus as the VPG (adapted from Holstege 1989). Right: dedicated VPG across the ventrolateral pontine brainstem according to Jürgens and Hage (2007). 5N, motortrigeminal nucleus; 7n, facial nerve; Amb, nucleus ambiguus; FN, facial nucleus; NRA, nucleus retroambiguus; soc, superior olivary complex.

(B) Vocalizations of a rat. Top: high-frequency calls, e.g., >30 kHz. Bottom: low-frequency calls, e.g., <30 kHz. Black: species-specific calls of an awake, behaving animal. Teal: vocalizations triggered by electrical microstimulation of the PAG in an anesthetized rat. Red: vocalizations triggered by electrical microstimulation in the brainstem in an anesthetized rat. Note the unnatural shaped vocalizations evoked by direct brainstem stimulation, reflecting the stimulation pattern in the vocalization itself. High- and low-frequency calls evoked by PAG/brainstem stimulation stem from different stimulation sites in the respective areas. High- and low-frequency calls could be evoked at the same PAG location, as shown in example calls of Figure 4.

(C) Left: PAG stimulation and simultaneous, local cooling of the brainstem. Thermistors measuring the temperature on the contralateral side of the brainstem. Blue haze indicates cooling effect. Red crosses indicate the 36 positions arranged in a 1 × 1-mm grid above the brainstem. Scaling and orientation are identical with maps in Figures 2 and 4. Right: coronal section of the PAG with the red arrow indicating the site of stimulation and lesion.

(D) Left: direct stimulation of the brainstem using a tungsten electrode in the same locations as the cooling. Right: depth stimulation of the brainstem was done in 500-μm steps throughout the brainstem.