"The central idea of shamanism is to establish means of contact with the supernatural world by the ecstatic experience of a professional and inspired intermediary, the Shaman. There are thus four important constituents of shamanism: the ideological premise, or the supernatural world and the contacts with it; the shaman as the actor on behalf of a human group; the inspiration granted him by his helping spirits; and the extraordinary, ecstatic experiences of the Shaman." (Hultkrantz I978: 11)
In the practice of shamanism, the spirit world or supernatural world is explicitly and implicitly presupposed. Often entering these spiritual realms and being in contact with different levels of the spirit dimension, is how they acquire their knowledge, power and wisdom and where they meet their guides and teacher spirits which will assist them during their present and future practice. As to the human group on behalf of whom they contact the spirit world, the shaman plays a vital role in community protection, health and wellbeing. The fourth element, the "ecstatic experience of the shaman", is largely achieved by the use of psychotropic plants, which are ingested during the initiation and special ceremonies, hence being an all important and central element in their practice.
The use of the term shaman, when referring to a medicine man, is justified in its general context. Nevertheless in this region of the Peruvian Amazon, the term that is largely used for a shaman is vegetalista or in some cases curandero (healer), which is what the maestros I’ve worked with, like to identify with. Vegetalista explicitly refers to an "expert in the use of plants" (vegetales). This term indicates, however, not so much the fact that they know and frequently use plants in their practice, but to the origin of their spiritual knowledge which derives directly from the spirit of certain plants they have dieted and with whom they now possess an intimate connection to, in turn these assist them in their practice as their guides and tutors.
The term vegetalista should not be confused with that of herbalist, which denotes a person knowledgeable in the use of medicinal plants and/or phytotherapy. All vegetalistas are also herbalists by default, in that they know a great deal about medicinal plants in all their dimensional domains and frequently use them in rituals and in healing sessions. On the other hand, not all herbalists may be referred to as vegetalistas.
Because Ayahuasca works in harmony with other teacher plants, often vegetalistas will include one or a few teacher plants in the concoction. This is usually done during apprenticeships in dieta. The added plants are known as “doctores'', it is believed that these plants are directly connected to spirits that will teach the vegetalista magic chants known as Ikaros and also gift them with a magic phlegm (Yachai, Yausa or Mariri). This substance is usually deeply installed in their throat from which they harness and draw the power to heal and where they also keep spiritual objects acquired during their training and dietas.
Vegetalistas also use Ayahuasca as a medium to discover the properties of other teacher plants. In order to do so, some leaves of a given plant are mixed in with the main Ayahuasca ingredients during the making of the concoction. The variations in visions during the experience of the mareación, including the dreams following the ceremony, will render important information to the practitioner on that given plant. In this context it is often the case where Ayahuasca alone will suggest in a vision, which teacher plant a practitioner should work with in a future dieta. This discourse between the maestro vegetalista and his collection of teacher plants (doctores) is what gradually develops into a powerful inner garden of great healing potential. Ikaros are used to summon and disclose the healing properties and energy of teacher plants, this sacred chanting acts like a bridge to facilitate the flow of healing power that is being conveyed from the maestro to the patient.
Source: VEGETALISMO - Shamanism Among The Mestizo Population Of The Peruvian Amazon by Luis Eduardo Luna, published by (ACTA Universitatis Stockholmiensis) Stockholm Studies in Comparative Religions.