Chitta (Memory-Consciousness)
Chitta — the mind-field comprising memory, intellect, and ego — is the substrate of all experience, the medium through which consciousness engages with the world, and the field that yoga practice progressively purifies.
Chitta is a composite term in Patanjali's psychology encompassing three mental functions: Citta (consciousness-field or mind-stuff), Buddhi (discriminating intelligence), and Ahamkara (ego-sense). As the repository of all samskaras and vasanas, Chitta is the totality of the conditioned mental life that yoga is aimed at purifying. Sutra 1.2's famous definition of yoga — 'yogas chitta vritti nirodhah' — names Chitta as the field to be stilled. The vrittis (fluctuations) of Chitta are the fluctuations of this entire field: thoughts arising in the intellectual layer, impulses arising from the ego layer, memories arising from the memory layer. Yoga practice operates simultaneously on all three layers — the asanas working on physical and energetic correlates, pranayama working on the energy layer, meditation working directly on the mental and ego layers.
Yoga is the cessation of the modifications of the mind-field.
Cognitive scientist Francisco Varela's neurophenomenological approach — combining first-person contemplative investigation of mind with third-person neuroscientific analysis — is the closest modern parallel to Patanjali's rigorous phenomenology of the chitta.
Yoga Sutras of Patanjali