Figure 5. Brain structures involved in the production of 22-kHz ultrasonic vocalizations (USV). Brain areas where electrical or chemical stimulation (indicated by a flash symbol) induced or where lesions (indicated by an X) decreased or abolished 22-kHz calls in rats. FC = frontal cortex (ventromedial); Nacc = nucleus accumbens; Ls = lateral septum; Pa = preoptic area; Amy = amygdala; HI = hypothalamus (posterior, perifornical); Hc = hippocampus (dorsal); Th = thalamus (midline thalamic nuclei); PAG = periaqueductal gray; LDT = laterodorsal tegmental nucleus; Me = medulla oblongata (lateral reticular and facial nucleus). Furthermore, the fornix, lesions of which can also reduce calling, is indicated by the dashed line.