on 4/1/09 10:41 PM, adinda van 't klooster at [log in to unmask] wrote:
> I am interested however, in how far you in your work make an assessment of the
> person's emotions or mental state and what exactly are you looking at and how
> does this change over time? Which bit of information do you get when someone
> stays wired up for 10 minutes, and why does it take that long to get it? What
> are the certainties that can be obtained from the heart rate data and which
> bits remain vague?
Hi Adinda (and all the other makers of physiologically responsive works out
there!)
This is going to be a very technical 'think aloud' reflection around
biofeedback signal analysis and what it can mean - so curators beware!
--
The present direction Iım heading in, is towards an approach in which
participants explore their ability to influence the work with whichever
emotions or breathing rhythms they want to try out. I suppose its very
proscriptive of me (maybe its just a phase I need to move through, and then
onto some alternate approach) - but Iım looking for that A-HAı moment that
happens in clinical biofeedback, when participants think "wow, I just
shifted the patterning of my heart rhythms by thinking (feeling) about
something melancholy/joyous", and then conversely "mmm, Iıve just spent 20
minutes focused on my heart and breathing Iıd like to have more moments in
my life when I can feel this settled and present to my self" I know fully
that you cant really design a persons response, but a goal like this can
help prioritise certain design/copywriting and evaluational goals.
So the interpretive materials would need to communicate the varieties of
emotional/attentive orientation that can be used to influence autonomic
nervous balance, and convey the time fames in which these transformations
unfold from.
Using spectrum analysis of Heart Rate Variability to explore
psychophysiological interactions:
The slowest band of frequencies in a short-term HRV (heart rate variability)
spectrum analysis is between 0.005 Hz and 0.05 Hz (around one wave-cycle
every three minutes).
In order to obtain reliable results from an FFT analysis, you need at least
double that period (nyquist rate) - so that's why it takes so long before
you can obtain a reading, unless we can time travel!. If you want to compare
relative amplitudes of the three key fq bins (VLF, LF and HF) then you need
to wait till you have recorded the slowest fq.
There is a general agreement around the delineation of three key frequency
bands within short term HRV spectrograms
HF (between 0.15 Hz and 0.4 Hz)
LF (between 0.05 and 0.15Hz) and
VLF (less than 0.015 Hz)
ULF is connected to circadian rhythms, but can only be measured over 24 hour
continuous recordings.
Where it gets hard is in the interpretation of the relative amplitudes of
these bins in relation to each other, and what these ratios mean (i.e.
HF:LF, VLF:LF etc.).
Standard texts correlate increased HF to increased respiratory sinus
arrhythmia (influence of breathing movements on vagus nerve) and by
extension increased parasympathetic arousal (rest-digest, calm, peaceful
etc.). Increased LF is then correlated to increased Sympathetic arousal -
and there's not much about VLF except that it may be connected with body
temperature regulation.
But this is where it gets tricky - because if you slow your breathing down
to 6 cycles per minute (like many forms of breath meditation) - then your
breathing will cause your HRV to resonate at around 0.01 Hz - and its clear
to the person doing this that they are feeling very restful and not involved
in a typical sympathetic nervous system response.
Biofeedback researchers Paul Lehrer and Evgeny & Vaschillo have referred to
this 0.01 Hz resonance as (not surprisingly) the HRV 'resonant peak
frequency', and it is the result of resonances between breathing, heart rate
and blood pressure. They have done some excellent research into how this
correlates to certain breath-based meditation techniques, and consider the
range of health benefits these practices may provide, in relation to how
they may be exercising certain HRV reflexes (please excuse the over
simplifications here).
Checkout Paul Lehrer's paper with Yuji Sasaki and Yoshihiro Saito:
"Zazen and Cardiac Variability" (1999)
http://www.psychosomaticmedicine.org/cgi/content/abstract/61/6/812
this paper gives a good introduction and explores HRV spectral data in
relation to zazen meditation practices.
During HRV resonance, energy is concentrated into a single peak frequency,
so typically you'll have a peak around 0.01 hz - in the LF band (but lower
if breathing is slower?), while the VLF and HF bands are very low. In THIS
context - some biofeedback practitioners have suggested the presence of
increased VLF as indicative of rumination. I'm inclined to agree, based on
my own observations in a clinical biofeedback session, but I've not yet
found any published test results to support this claim.
On reflection, I think I'll probably end up designing my new works around
this resonant phenomenon - which could simplify the interpretive
requirements a bit too.
The idea of creating interactions that can facilitate physiological
conditions similar to those obtained during breath based meditation is very
appealing to me (again, I'm cautious not to reduce meditative practice to
physiological states!).
In this case, I'd be tracking increased 'resonance' i.e. Simplicity of
spectral profile and resonant frequency vs. complexity and distribution of
spectral profile.
This would suggest various 'conical/funnel-shaped' interaction spaces/axes,
all directed towards or away from HRV resonance, and then responsive to the
specific frequency of that resonance (I'm not talking here about a physical
space in a gallery, but a mathematical space describing the range of
possible positions one occupy within a set of sensor data coordinates).
How would one then describe to audiences some approaches to interacting with
such a work without sounding too prescriptive and new agey? A game like
challenge to see if you can focus your heart rate pattern into a single fq,
though a combination of slow breathing, and calmness could be one approach -
but the idea of 'gaming' as its understood by the wider general public,
seems at odds with the intensely meditative states I'm encouraging people to
explore during their interaction with the work.
Maybe a visual map of the above mentioned conical /funnel space, would be a
good start - but visitors would still need to understand what HRV spectral
analysis is/means - and if this post is anything to go by - you can see If
still got a long way to go!!
Using a map-like visual representation of the interaction space as an
interpretive design, also opens the way for a less goal-oriented engagement
(I can still remember being collected from the beautiful virtual wilderness,
by attendants in BLAST THEORY'S 'Dessert Rain' show, after all the other
players had collected their tokens - I was too busy smelling the flowers!)
The map delineates the boundaries of the interaction space, and leaves the
participant free to explore the space at will. Participants can also compare
their experiences with each other by way of talking about the different
journeys they made through this 'interaction space' during their engagement
with the work.
Cheers
Dr. George Poonkhin Khut
Mobile 0417 566 425 (International 61 417 566 425)
E-mail [log in to unmask]
URL http://www.georgekhut.com/
73 Edward Street
Darlington, NSW 2008
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