NPBR-115; No. of Pages 5
neurology, psychiatry and brain research xxx (2013) xxx–xxx
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/npbr
Short-term cued visual stimuli recall in relation to breathing
phase
Matevz Leskovsek a,*, Ajda Skarlovnik b, Gašper Derganc a,b,c, Nika Pušenjak c
a
BreathingLabs.com, Zdrav dih d.o.o., Mesarska cesta 26, 1000 Ljubljana, Slovenia
University Clinical Centre of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia
c
Interdisciplinary Research Group Larus Inventa d.o.o., Vojkova 63, 1000 Ljubljana, Slovenia
b
article info
abstract
Article history:
In this research, we observe volunteer's ability to recall visual stimuli in relation to their
Received 16 January 2013
breathing phase at the time of presentation of those stimuli. To assess the ability to recall
Received in revised form
visual stimuli, we have exposed volunteers to a short term cued visual recall task; a cued
27 May 2013
Brown–Peterson task. We observe that the ability to recall visual stimuli does not noticeably
Accepted 4 July 2013
relate to inspiration/expiration phasing (4.2% bias), but that it more noticeably relates to
volume of air in lungs measured as expansion of abdomen (10.2% bias). We propose that this
observation could potentially suggest that humans are more susceptible to memorizing new
stimuli when there is less air in their lungs; i.e. after they have sufficiently exhaled by
sighing, yawning, or vocally expressing what's on their mind. As soon as new inhalation
Keywords:
occurs, another fight or flight response is initiated, and their susceptibility to new information
Respiration
is reduced.
© 2013 Elsevier GmbH. All rights reserved.
Breathing
Visual recall
Visual memory
1.
Introduction
Magnetic resonance imaging studies have shown that respiration consistently affects brain activity [1–8]. It can thus be
assumed that communication in humans is prone to the
recipient's breathing phase; i.e. the relative position in their
breathing cycle. Communication is also heavily dependent on
the process of memory formation, which is a complex process
that involves mechanisms of ion exchange (presynaptic Ca2+
pump and synaptic K+/Na+ pump), mechanisms of classical
conditioning, and various potentiation mechanisms such as
repetition, synaptic augmentation, and post-tetanic potentiation [9–14]. We hypothesize that breathing interacts with this
process of memory formation, which is being most prominent in
panic and anxiety disorders, where breathing is rapid and
intense [15–18]. Furthermore oxygen administration has consistently shown an enhancement in memory performance [19–21],
which implies some causality between the process of respiration
and the process of memory formation. Brown–Peterson task is a
method of evaluating short-term memory [22–24]. Its name
refers to two studies published in the late 1950s that used similar
procedures; one in 1958 by Brown [25] and a second in 1959 by
Lloyd and Margaret Peterson [26]. The objective of this research
is to observe whether breathing noticeably affects short-term
visual stimuli memory formation in healthy adults.
2.
Materials and methods
Ten healthy volunteers (6 females, 4 males) in an active period
of life (students and employees) between 26 and 40 years of age
* Corresponding author. Tel.: +386 31380511.
E-mail addresses: [email protected], [email protected] (M. Leskovsek).
0941-9500/$ – see front matter © 2013 Elsevier GmbH. All rights reserved.
http://dx.doi.org/10.1016/j.npbr.2013.07.001
Please cite this article in press as: Leskovsek M, et al. Short-term cued visual stimuli recall in relation to breathing phase. Neurol Psychiatry Brain Res
(2013), http://dx.doi.org/10.1016/j.npbr.2013.07.001
NPBR-115; No. of Pages 5
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neurology, psychiatry and brain research xxx (2013) xxx–xxx
Fig. 1 – Screenshot of a trigram as shown on computer
display.
participated in a memory evaluation trial. Volunteers were
exposed to visual presentation of trigrams while their
breathing was recorded using a sensor measuring expansion
of abdomen (stomach). The duration of the presentation was
50 s with a frequency of one trigram per second. A trigram is
a set of three consonant letters (for example, TDW) that has
little or no meaning. Trigrams have no vowels, preventing
their easy pronunciation, which makes it more difficult for
volunteers to create vocal cues to help memorize them
better. As trigrams are equal in length, the experiment is
less biased in terms of the information it requires participants to remember. Trigrams were randomized for each
volunteer.
Trigrams were displayed on a computer display (Fig. 1) by a
simple jRuby script (Fig. 2). Jruby is a variation of the Ruby
programming language that runs on the Java Virtual Machine.
Approximately 30 s after being exposed to trigrams,
volunteers were asked to recall those 50 trigrams and were
offered 2 min to identify them amongst 150 trigrams.
3.
Results
The following 12 charts (Fig. 3) represent the raw data of
breathing activity and trigrams of the first volunteer. Trigrams
presentation started at time 0:00:20 (20 s). Correctly recalled
trigrams are marked with **.
In order to determine the segments of inspiration and
expiration, we fitted the raw data with a 6th order polynomial
curve. Segments of inspiration and expiration were then
identified by observing this polynomial's trend (Fig. 4).
The following chart is a data summary of all 10 volunteers
where recalled trigrams are plotted in relation to abdominal
expansion and in relation to their inspiratory/expiratory
phasing (Fig. 5).
Sixty-seven correctly recalled trigrams occurred during
expiration and seventy-three correctly recalled trigrams occurred during inspiration, resulting in a 4.2% bias. We therefore
do not report any significant differences related to cued recall of
trigrams being perceived during expiration or inspiration
respectively.
Fig. 2 – jRuby script used for trigram presentation.
The mean value of abdominal expansion of positively
recalled trigrams was 6146.38 mm, the mean value of minimum to maximum abdominal expansion in all ten volunteers
was 7648.21, resulting in a 10.2% bias toward lower abdominal
expansion. Therefore, those trigrams that were perceived at
lower abdominal expansion were recalled with greater
success.
4.
Discussion
Polynomial fitting eliminates high-frequency activity of raw
data recordings and preserves the rough dynamics of a curve.
This method thus seems like a viable approach for expiration/
inspiration phase assessment. However, polynomial fitting
introduces some deviation from raw data recordings (see
Fig. 4) and we believe it could potentially be better fitted with
splines.
Because some trigrams resembled some known acronyms
we hypothesize that volunteers were able to memorize them
better. This represents a potential drawback of using trigrams
in such a cued visual stimuli recall experiment; however, we
believe that it would be difficult to find visual stimuli that
Please cite this article in press as: Leskovsek M, et al. Short-term cued visual stimuli recall in relation to breathing phase. Neurol Psychiatry Brain Res
(2013), http://dx.doi.org/10.1016/j.npbr.2013.07.001
NPBR-115; No. of Pages 5
neurology, psychiatry and brain research xxx (2013) xxx–xxx
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Fig. 3 – Raw data of breathing activity and trigrams of first volunteer. Trigrams presentation started at time 0:00:20 (20 s).
Correctly recalled trigrams are marked with **.
would not trigger any associations simply because various
people have various associations.
In this research, the expansion of the abdomen was used as
a prediction of volume of inhaled air. It is important to
understand that any volunteer's shallow or chest breathing
would reduce the dynamic range of such predicted volume and
would therefore distort the ratio between visual stimuli recall
and subject's breathing. In this experiment, we did not observe
such shallow or chest breathing.
We suppose that in such a cued recall memory session it
would be appropriate to take into account the possibility that
volunteers' attention during stimuli presentation varies with
Fig. 4 – Polynomial fitting and breathing phase assessment (in = inspiration, ex = expiration) and success of trigram recall
(0 = no recall, 1 = correct recall).
Please cite this article in press as: Leskovsek M, et al. Short-term cued visual stimuli recall in relation to breathing phase. Neurol Psychiatry Brain Res
(2013), http://dx.doi.org/10.1016/j.npbr.2013.07.001
NPBR-115; No. of Pages 5
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neurology, psychiatry and brain research xxx (2013) xxx–xxx
references
Fig. 5 – Data summary of all 10 volunteers where recalled
trigrams are plotted in dependency of abdominal
expansion in micrometers (ordinate axis), time of trigrams
presentation (abscissa axis) and according to their
inspiratory/expiratory phasing (blue = inspiration,
red = expiration). (For interpretation of the references to
color in this figure legend, the reader is referred to the web
version of this article.)
time, such as attention being greater at the beginning, as
can also be observed in our data in Fig. 5. Such modulation of
attention should be treated accordingly, such as ignoring the
beginning of recording, where attention is presumably
higher.
Although memory formation has shown to be consistently
affected by administration of oxygen [19–21] we observe that
relative position in ones breathing cycle might also play some
role in this process. However, the sample in this research
includes only ten healthy adults ranging in age from 26 to 40.
Such a sample profile prevents the generalization of the
results and so is not yet suitable to provide safe conclusions
regarding correlation between cued short-term memory recall
and breathing phase in humans.
This research could potentially suggest that humans are
more receptive to processing new information when there is
less air in their lungs. Such dynamics can easily be observed
in human communication – a recipient is most receptive to
new information after they have sufficiently exhaled, for
example after sighing, yawning or having vocally expressed
what is on their mind. As soon as new inhalation occurs,
another fight or flight response is initiated, and their
susceptibility to new information is reduced. In this
research, we observed volunteer's ability to recall visual
stimuli in relation to their breathing phase at time of
presentation of those stimuli measured as expansion of
their abdomen.
Conflict of interest
Matevz Leskovsek is a partner at BreathingLabs.Com (Zdrav
dih d.o.o.), a company that produces human computer
interfaces for breathing exercises, breathing games, and
breathing entertainment. Other authors declare no competing
interests.
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Please cite this article in press as: Leskovsek M, et al. Short-term cued visual stimuli recall in relation to breathing phase. Neurol Psychiatry Brain Res
(2013), http://dx.doi.org/10.1016/j.npbr.2013.07.001
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