Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 1
I don’t think the Jivatma is concentrated anywhere,– except in this sense that in the waking state it is the mental Purusha that leads and the seat of the mental Purusha is in the head, behind the centre between the eyebrows. In the dream state what 
remains active in the body is the externalising consciousness (or something of it) and the centre of that is in the neck (throat). In the suṣupti, if it is real suṣupti, not merely unconscious of dreams, but absence of dreams, the consciousness is deep within in the heart centre or behind it – for that is the veiled centre of the innermost being.