The thalamus is a paired structure joined at the midline and sitting very near the centre of the brain. In humans, each half is roughly the size and shape of a walnut. Essentially, all information reaching the brain, and thus consciousness is relayed through the thalamus.
All the objective information that is generated from the sense organs is essentially coupled or tagged, with a subjective coordinate by the thalamus.This tagged data is then stored appropriately for future reference.
A computer stores data too, but impersonally. This data storage is totally a function of operating system, common to all the machines using it. There is no preferential, or biased data storage, that is unique to each computer.
The same visual image viewed by two different individuals is perceived, interpreted and stored differently. This ‘emotional indexing’ is mediated by the complex interconnections of the thalamus with different centres of the brain.
On reaching the thalamus, the signal percolates like a drop of ink on blotting paper (thalamo-cortical radiation) to adjacent processing areas such as-
The hippocampus: This has a crucial function in the creation of memory. It has specialized adjustable synaptic receptors called NMDA receptors that can assign a constellation of properties linking an object and its context.
The amygdala: The amygdala is largely responsible for generating and regulating major emotions such as anger, happiness, joy, sadness, and mainly fright.
Orbitofrontal cortex: If, driving to work on a Monday morning, you have had a narrow escape at a particular intersection on the road, it is very likely that for a long time thereafter, there will be a knot in the stomach when approaching that intersection, specifically on Mondays around the same time. The orbitofrontal cortex has stored the spatio temporal coordinates, and the amygdala has stored the fear.
The anterior cingulate cortex: The anterior cingulate cortex monitors the direction of activity, and progress toward a set goal. It has the ability to rework the strategy if the existing one does not seem to work.
The above mentioned centres are part of the ‘limbic' system, which is an important constituent of even the very primitive reptilian brain.
These emotional coordinates weave a pleasure - pain, attachment -avoidance grid. Our identity is pure Consciousness trapped in this matrix of likes, dislikes , preferences and aversions,
an identity that we generate of ourselves for ourselves, by ourselves.
Based on this matrix of emotional coordinates, the various synaptic connections respond to subsequent inputs by an effulgence of neurotransmitters that generate a myriad of motor responses.
The human brain has an evolutionary upgrade. An intelligence that can discern, discriminate and transcend this program of emotional tagging. This intelligence is called 'vivek'.
This program could be transcended by inhibiting the spread of thalamo-cortical radiations. Practices such as meditation or chanting may facilitate this inhibition to a point of 'Vairaagya' or a state of detachment.
This is a state or a discipline that results in control of the spread of the sensory inputs from the thalamus and subsequent emotional tagging.
Using ‘vivek’, the potent power of discrimination, ‘vairagya’ is effected, more as a consequence. Renunciation as a beginning of all spiritual endeavour, might be putting the cart before the horse- the effect preceding the cause.
Vairagya is the ability to restrict all data to the ‘objective’ domain, eliminating the ‘subject’ totally. In neurological terms, it would be described as an elimination of neuronal segregation,reducing the hierarchy of neurotransmssion to a monarchal singularity ;
an ability that progresses to sharp focus and localise perception to mere awareness . Transcending personal consciousness to a state of total objective impersonal awareness, a point of cognitive bliss that expands to become the manifest universe, a state of Samadhi.
Dr Deepak Ranade