<p>Investigating how cortical neurons respond to interoceptive cues remains a challenging task that is crucial for understanding self-awareness in advanced mammals, including humans. A fundamental aspect that has received intense attention from researchers is whether neural or not networks in an animal’s cerebral cortex can accurately reflect the internal states of the organism, especially cardiac activity. To address this, we studied neurons in the temporal cortex of awake and sleeping cats using a unique experimental arrangement providing continuous recording of local potentials and single-neuron activity in specific cortical areas and monitoring of a variety of the animal’s physiological parameters, including the electrocardiogram. The results showed that heart rate-synchronized activity in the primary auditory cortex (AI) was either absent or very weak. At the same time, the secondary auditory areas of the temporal cortex, located in the anterior ectosylvian sulcus and posterior ectosylvian gyrus, showed synchronization with the heart rate. This synchronization was particularly evident in local potentials, though some single neurons responding to sound signals also showed rhythmic activity synchronous with heart contractions. The shape of the phase histograms constructed on the basis of the cardiogram period suggests that this synchronization ensures that the cortex receives information about the state of the internal environment of the body. These data encourage consideration of the hypothesis that primary self-awareness arises as a result of the dynamic interaction of neural ensembles representing external sensory information and information from the internal organs, primarily the heart. This type of interaction may underlie the sense of self in highly developed organisms.</p>