Atma means soul or self or conscious. The term also denotes other meanings like spirit, breath, individuality, peculiarity, character, nature etc.  Atma is the connection to knowledge depository (dnyanapratisandhata). (Chakrapani on Cha.Su.1/42) Atma is a fundamental element. (Cha.Su.1/48). It is the element of consciousness in holistic human being. (Cha.Su.1/46-47, 8/4, Sha.1/16)
Etymology and derivation
Paramatma, Jeeva, Indriyatma, Bhutatma, Antaratma, Jeevatma, Chetana dhatu, Dehi, Shariri, Prani, Puman, Purusha, Sattva, Kshetradnya, Beejadhatu, Beeja dharma, Garbhatma, Dnya, Nirvikar, Para, Nirguna, Avvaya, Akshara, Sarvadnya, Vibhu, Nirvishesha, Vashinam, Swatantra, Avyakta, Ishwar, Parameshavar, Vishvarupa, Vishvakarma, Nityayuka, Sanushaya, Pudgala, Ka, Ya, Sa, Asau. 
The term atma implies different meanings as per the usage in different contexts.
- The individual soul or life (the sign of life)
- The soul of the universe (brahma)
- The self, the abstract person or individual or being
- The nature or constitution
- The natural temperament or disposition
- The intellect or understanding
- The fundamental cause (karana)
Qualities of atma
The soul has following qualities:
- Eternal (shashvata)
- Free from diseases (aruja)
- Does not have any age (ajara)
- Immortal (amara)
- Does not undergo decay (akshaya)
- Impenetrable (abhedya)
- Unbreakable (achhedya)
- Unperturbable (alodya)
- Omnipresent (vishvarupa)
- Omnipotent (vishvakarma).
- It is invisible (avyakta), neither has a beginning nor an end (anadi-nidhana) and is imperishable (akshara). (Cha. Sha. 3/8)
- The soul is omnivagant / omnipresent (can move anywhere and everywhere), sustains all bodies, performs all actions, and takes all forms.
- It is the source of consciousness, transcending all senses, as it is always associated (with intellect etc.), it gets involved in feelings like attachment etc. (Cha. Sha. 2/32]
Location of atma
Atma or the soul is located in the heart with mind. This is the supreme site of consciousness. (Cha.Su.30/4, Cha. Ni.8/4). The consciousness is spread all over body through mind and senses. (Cha.Su.8/4, Sha.1/79-80)
Numerology of atma
Atma is only one and omnipresent. However, it follows personified patterns in individuals. 
Importance of knowledge of atma
Fundamental component of holistic human being and life
- Atma forms fundamental structure of holistic human being with sattva (mind) and sharira (body). (Cha. Su. 1/46).
- Atma is essential component of ayu (life) with combination of sharira (body), indriya (sense and locomotor organs) and sattva(mind). (Cha.Su.1/42).
Role of atma in embryogenesis
- Life begins with entry of consciousness during the process of conception or the union of sperm and ovum. The consciousness associated with embryo is also called as garbhatma or antaratma. (Cha. Sha. 3/8)
- Consciousness (chetana) constitutes sixth dhatu (structural component) of a living being with five mahabhuta. (Cha.Sha. 4/6)
Atmaja bhava (factors originating from soul)
The following factors originate from atma are called atmaja components.
- Taking birth in a species
- Ayu (life span)
- Atma jnana (self-realization)
- Manas (mind)
- Indriyani (sensory faculty)
- Prana-apana (inspiration-expiration)
- Prerana (motivation) and Dharana (sustenance)
- Characteristic Akruti (physique), Swara (voice) and Varna (complexion) of the individual
- Sukha (happiness) and Dukha (sorrow)
- Ichcha (Desire) and Dwesha (dislike)
- Chetana (consciousness)
- Dhriti (courage)
- Buddhi (intellect)
- Smriti (memory)
- Ahamkara (self-identity or ego)
- Prayatna (efforts).
All these aspects of the individual are derived from the soul. (Cha. Sha. 3/10) Atma controls all these functions. (Cha.Sha. 1/70-72)Absence of these functions are termed as ‘death’. (Cha.Sha.1/73)
Role of atma in the process of cognition
- Fundamental process of perception involves combination of Atma, indriya (sense organs), mind and sense objects. This association results in action, sensation and understanding. Manifestation of every effect can’t occur in absence of any of these components. (Cha. Sha. 1/57) The observational knowledge gained by this process is established as pratyaksha pramana (proof of direct observation or witness). (Cha.Vi.8/39)
- Mind is active, but devoid of consciousness. The soul is conscious, but not active. Soul is considered a doer, or an actor, or an agent of deeds. Hence all the actions are performed by combination of mind and soul. (Cha. Sha. 1/75)
Role of atma in self-control
- Atma is the supreme which controls all faculties like mind, intellect and sense organs. Hence the control over diet and lifestyle habits is directly related with atma.
- Atmavan word is used for a wise man who has self-control. (Cha.Su.5/35,49). This word is used in context of medicated smoking. It shows there are chances of losing self-control and it may result into excessive smoking. Hence medicated smoking shall always be done with total self-control.
- A person desiring to live the full span of life should remain in self-control and live with great caution assuming that he is constantly surrounded by the foes to his health. (Cha.Su.17/119)
- Atmavanta (having self-control) is a quality of good physician. (Cha.Su.10/4) The physician having self-control succeeds well in clinical practice.
- Atma is one of the components of adhyatma dravya samgraha (absolute elements). The other elements are mind, sense organs, their objects and intellect. These are responsible for all auspicious and inauspicious deeds. (Cha.Su.8/13) These deeds further derive daiva (destiny) of an individual. (Cha.Vi.3/30) The virtuous acts determine lifespan of an individual. (Cha.Sha.6/30)
Importance of self-realization
- Atmavijnana (knowledge or realization of self) is considered as one of the preventive measures of exogenous and endogenous disease. (Cha.Su.7/53) One should know his/her own capacity before doing any work or adventure. In other words, one shall always work or perform duties as per own capacity. Otherwise it may lead to ‘shosha’(tuberculosis). (Cha.Ni.6/4) This will preserve health and prevent diseases.
- Self-realization is an important process in attaining salvation.
- Atma rupa term is used to denote inherent properties. E.g. Vayoh atma rupa means inherent properties of vayu. (Cha.Su.20/12)
- Atmaja or atmaka term is used to denote origin. E.g. Nanatmaja (Cha.Su.20/10), Vatatmaka (Chakrapani on Cha.Su.19/05).
Importance in clinical practice
- Blissful state of atma (soul), indriya (senses) and mana (mind) is essential component of health. 
- During clinical examination, the physician shall know inner self of the patient in order to have complete knowledge of disease. (Cha. Vi. 8) It is important to reveal the fundamental cause of disease and its progression. Without this knowledge, treatment is incomplete.
- Antaratmani or the inner self is related to mind. The sensation of pain is diminished after langhana therapy. (Chakrapani on Cha.Su.22/35)
- Knowledge of self is important to decide satmya or suitability. (Cha.Vi.1/20)
- Self-deeds are responsible for all diseases. (Cha.Ni.7/21)
Knowledge of absolute truth
- Adhyatma means tattva or absolute truth. (Chakrapani on Cha.Su.25/27). In the conference on origin of purusha (holistic human being), Lord Punarvasu instructed all sages not to involve in disputes and seek the absolute truth.
Current views and researches
The above points make it clear that the atma is connected with cognition and memory. The will, belief and behavior depend upon atma. Atma always performs with mind. Life begins with entry of atma and ends with its exit. However, the exact psycho-neuro-biological connection is not known.
The following connections need to be studied more:
- Role of atma in process of cognition and memory
- Consciousness element and beginning of life
- Atmaja bhava (factors related to atma) in embryogenesis
World Health Organization Quality of Life Questionnaire
The world health organization has included spiritual dimension of health in assessing quality of life of an individual. The questions in the scale are related to personal beliefs, and meaningfulness in life. The two aspects are supposed to give strength to face difficult situations in life and sense of satisfaction. 
Spiritual dimension of health
The spiritual dimension of health is important for the attainment of an overall sense of health, well-being and quality of life. The patient’s spiritual perspective needs to be taken care during hospitalization. 
In a research on consciousness, a model is presented by Kotchoubey B. It conceives of human consciousness as a product of a phylogenetic interaction of three particular forms of animal behaviour: play, tool use, and communication. A positive loop is observed when the three components meet in humans, they strengthen and mutually reinforce each other. This structure permits to explain typical features of human conscious awareness: its recursive character, seriality, objectivity, close relation to semantic and episodic memory, etc. Other specific features of human consciousness (e.g., the emotion of anxiety) remain and require further reading. Again, the complex relationships of this model of consciousness with the multiple draft theory, the re-entrance theory, and the classical dualistic approach require further reading. 
References from Charak Samhita
The list of references for Atma in Charak Samhita can be seen here. Atma references Charak Samhita.pdf
- Available from http://spokensanskrit.org/index.php?tran_input=AtmA&direct=se&script=hk&link=yes&mode=3
- Atman, Oxford Dictionaries, Oxford University Press (2012)
- John Bowker (2000), The Concise Oxford Dictionary of World Religions, Oxford University Press, ISBN 978-0192800947
- WJ Johnson (2009), A Dictionary of Hinduism, Oxford University Press, ISBN 978-0198610250
- Karel Werner (1998). Yoga and Indian Philosophy. Motilal Banarsidass. pp. 57–58. ISBN 978-81-208-1609-1
- Chad Meister (2010), The Oxford Handbook of Religious Diversity, Oxford University Press, ISBN 978-0195340136, p.63
- Thakar V.J. Ayurvediya Maulika Siddhanta, Sanskrit book.1985. Gujarat Ayurved University, Jamnagar Atmatattva vivechanam.p.364
- Thakar V.J. Ayurvediya Maulika Siddhanta, Sanskrit book.1985. Gujarat Ayurved University, Jamnagar Atma Tattva vivechanam.p.367
- Sushruta Samhita Sutra Sthana 15/41
- WHO Quality of life scale available from https://www.who.int/healthinfo/survey/WHOQOL-100.pdf?ua=1 downloaded on February 28, 2020
- Ross L. The spiritual dimension: its importance to patients' health, well-being and quality of life and its implications for nursing practice. Int J Nurs Stud. 1995 Oct;32(5):457-68.
- Kotchoubey B (2018) Human Consciousness: Where Is It From and What Is It for. Front. Psychol. 9:567. doi: 10.3389/fpsyg.2018.00567