Wednesday, March 24, 2010

Re: [Yasmin_discussions] Multisensory Perception

Hi Yasminers,

Thankyou Antonio for your contribution and links, adding to many
threads in the discussion---Richard and I have had a few ideas as

'Feeling' has been discussed by many. Once we start talking about
feeling in the context of sensing, we wondered whether we can draw a
line neatly between them. Certainly we can't within an individual
where these are inextricably connected, feeding back on each other.
For instance we know very well that environment can impact enjoyment
of a multisensory experience. A meal from a three star Michelin chef
won't taste great when the people sitting next to you in the
restaurant are arguing (Hervé This, [2010] Nature 464: 355). At the
nuts and bolts level too there is evidence for the influence of the
whole on the sensing machinery at the periphery. Based on context and
previous sensory input the brain can trigger the release of hormones
that influence the process of odour perception right near the
periphery, the sensory neurons where their axons first converge in the
sensory bulb. This process has been observed in insect and mammalian
systems where a range of different hormones can be released in the
antennal lobe (insect) or olfactory bulb (mammal) to modulate sensory
signals. This modulation by hormones on sensory input is typically
associated with learning behaviour where experience guides future
sensory events.

In a test of whether feeling and sensing can be teased apart, Raewyn
turned to some of our experimental systems where we use cells to
investigate the nature of olfactory receptors. We work with both
insect and human cell lines that can be engineered to express
olfactory receptors. With these we can investigate what odours a
particular receptor can smell and how the receptors work. The
question that Raewyn asked is whether these cells, now empower with
the gift of smell, have feelings through there new found ability to
sense. While they don't have a mind, the cells are able to respond to
stimuli to physically expression a reaction or state. And certainly
single-celled organisms such as amoeba respond to stimuli with
different behaviours and across a number of amoeba they will respond
in multitude of ways, perhaps an indication of individual states or
possibly feelings. But what if the olfactory receptors are now taken
into a device or cybernose, outside the context of any format we would
be comfortable to describe as living like a cell. While our device
might be able to smell it seems beyond what could be considered able
to feel. And if our device can't feel … will it then be able to smell?

Another area that we have been discussing within the topic of
multisensory perception is just whether we understand what makes up
the 'multi'. Certainly while we may seem fairly sure we understand
our basic senses, new senses are being discovered all the time. Some
of the contributors have alluded to these, sensing gravity, magnetism
and sensing internally. In the area of taste perception the
mechanisms involved in the perception of acids, calcium and fats have
only been uncovered in the last few years and the ability to perceive
such attributes as astringency and texture are still to be uncovered,
never mind senses we haven't even imagined we might possess. This is
perhaps fruitful ground in which scientists and artists can collaborate.

Others have talked about sensing internally or interoception,
certainly an area where science is only just beginning to understand
how we sense inside ourselves. A statue in the heart or a boat in the
liver. From a science perspective recent work on chemosensory
perception has uncovered a number of receptors that are expressed in
our gut or gastrointestinal tract. While we do not consciously
perceive tastes in our guts through these, they are thought to be
involved in perceiving compounds that trigger satiety, telling our
brain when we are full and to please stop eating. It is all in the
wiring, rather than being wired to a chemosensory integration centre
in the brain, the orbitofrontal cortex, then onto the hedonic centres
such as the amygdala, the taste receptors in the gut are wired through
the vagus nerve into a centre in the brain involved in controlling
feeding, the hypothalmus. And while we are talking of guts and brains
we should mention the enteric brain or second brain. The
gastrointestinal tract is surrounded by a dense network of neurons
collectively known as the enteric brain. Perhaps this is where the
expression 'gut feeling' comes from? the knowledge that arises into
consciousness and is felt sometimes as a pang, a churn, movements like
butterflies wings beating, a sound, a chord, a colour...

Raewyn, Richard
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