Tuesday, May 28, 2013

Hacking the brain: The salience map

The world around us is a landscape of emotions. It's an assemblage of entities and systems that evoke body-level feelings within us. Everything from the terror of rounding a corner and coming face to face with an oncoming car to the aesthetic pleasure of a peach-and-gold sunset over a rolling landscape of twilight hills. The parts and pieces and even the sum of the whole that is each situation all compete for our attention through the tug of emotions.

Of course emotions aren't actually a part of the physical world. They are qualities embedded in our perception by the pre-conscious valuation functions of our brains. That salience-map landscape of emotion that the brain generates is something I'd love to be able to tweak, hack, or even swap around as templates of perspective and personality.

As the term suggests, our salience maps are representations of relevance. We assess what's important among the entities and events of the present in terms of immediate emotional arousal or lack of the same. The curve of a hip and the swell of breasts are much more provocative as far as social and reproductive opportunities than a drab brick wall in the background. Or maybe it's a broad pair of shoulders and the swaggering confidence in a man's walk, depending on your gender or orientation. Such varying valuation of parts within a setting helps to differentiate us as individuals on many levels.

Our emotive response to the whole also makes us who we are as people. The bold and the frightened often see the same situation through very different emotional lenses, as do the young and the old. Whether a dark forest evokes an atmosphere of adventure or an air of trepidation depends a lot on who you are.

So what if we could swap those emotional masks? Simply pull a USB thumb drive out of a socket on the side of one person's head and slot it into another's, transferring a whole map of emotional valuations? What if we could do the same with the emotive templates of different trades and professions. There are likely some interesting degrees of difference between how a passionate artist, dedicated geologist, veteran Marine, and a writer all respond to the same situations on a gut level.

Or maybe not. It would be interesting to compare how each salience map highlights or suppresses certain aspects of the world, and see if there are significant contrasts or similarities.

How different are we really at the level of the heart? Or, well, the limbic system as the case may be.

At same time, salience maps would probably be one of the most difficult elements to swap between brains - their construction being so very individualized. These maps of feelings-based relevancy are built during the act of encoding experience into memory. A process that the amygdala and basolateral nuclei of the brain carryout based on the strength of emotions. The stronger an associated feeling, the more likely a situation will be transcribed into the long-term storage of autobiographical memory. That, and the more likely it will be recalled and produce an emotional reaction - a self-reinforcing mechanism which contributes to the flashbacks and anxiety attacks associated with Post-Traumatic Stress Disorder syndrome.

There are two other highly individualized mechanisms that may well play important roles in constructing a person's salience map. The neuromodulatory systems involving dopamine, serotonin, and other hormones associated with pleasure, satiation, and other positive and negative feedback feelings almost certainly have a profound impact on assigning emotional valuations. Then there is the matter of perspective. The associative reasoning area of the frontal lobes generates models of the world. Those models are the viewpoints that we call perspective - a mode of perception well known for it's ability to dampen some emotions and heighten other.

The role of concepts in emotion brings up another fascinating aspect of salience maps. There are times when it feels like we have two such maps. A visceral, primal one for the external reality of the physical world, and another, more rarefied internal map. An array of emotional responses to an inner landscape of ideas and concepts. One colored by feelings that are sometimes as abstract as the notions themselves. Intellectual fascination, dawning comprehension, a sense of completeness and making sense, a feeling that an idea is elegant or even beautiful, and at times the vague, unfocused unease of cognitive dissonance - that nagging feeling that something is flawed with our understanding of events.

I suspect that there is a second map, based on the fact that within our declarative memory - the memories that we can consciously recall - we have two physical subsystems. One is the autobiographical remembrance of situations we have lived through, and the other is the semantic memory, which holds words as well as concepts that are independent of the occasions in which they were learned.

We'd be terrible philosophers, mathematicians, and scientists if we had to recall when and how we learned each abstract concept in our reasoning toolkit every time we tried think through a problem or workout a cause-and-effect relationship. We should be grateful that that our semantic memory apparently managed to evolve out of a declarative memory subsystem that was organized on the basis of space rather than time, and that may have held spatial recollections of positive and negative stimuli.

The difference between these two maps raises yet another interesting possibility. What if it were possible to transfer one map a time. What would the world look like if you had Stephen Hawking's conceptual salience map? What would happen if you transferred it to a painter? Would mathematical concepts normally as dull as ditch water suddenly shine with all the emotional intensity and urgency that the artist normally associated with hues and textures? Would it radically alter his or her art, or even the very ability to paint?

How much of an impact would a conceptual salience map have on the more gut-level external one associated with personal experience?

Again, our landscapes of emotion are so very individualized and tied up in so many interwoven valuation, conceptualization, and memory systems that actually transferring one to the wetware wiring of another brain would be extraordinarily difficult if not impossible. In cybernetic terms, creating an emulation of another's mode of operation would be a much more likely solution than an actual transmission.

Of course having the control required to make an emulation would likely mean having the capability to edit one's salience maps.

That raises still more possibilities. Could a person make himself a better mathematician or physicist by artificially boosting his fascination with a set of abstract concepts? Could a terminally bored child in school create a better future for himself by plugging in the emotional focus of a peer who finds school fun? What if the elegance of a simple but explanatory idea evoked the same persistent sense of engagement that we normally associate with the desire for sex or the craving for sweet foods?

How about this: Is it possible to have the salience maps of a scientist and a skilled artist? Or are they mutually exclusive to some degree? Can we have it all, or are there underlying physiological reasons that we never will. Has evolution just not had the necessary time to go down certain paths of expanded capability, or are the different, almost stereotyped modes of emotional perception the result of neurologic engineering compromises?

I wouldn't be surprised if it's the latter to some degree. In many ways our brains are hyper-engineered for efficiency in both energy consumption and heat output. Where the CPU of the laptop or tower that you're probably reading this on is hot enough to burn your finger, your vastly more powerful brain is only warm to the touch. Which is a good thing. Not only would you light your hair on fire while thinking hard if your gray matter were as inefficient, but your ancestors would have had a nearly impossible time finding enough calories to stay alive in a world where food scarcity and spring famines were common lifetime experiences.

So having the emotional outlooks of an Einstein and a Picasso might not be worthwhile from a hunter-gather evolutionary niche perspective. Then again, given the problem of obesity in industrialized nations these days, maybe brains that are more calorically demanding might be better suited to our current surplus and sedentary lives.

Just a thought.

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