report physiological responses and biometric signals

7/26/2019 Report Physiological Responses and Biometric Signals

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The Technical Science Behind ZENTA:

Physiological Responses and Biometric Signals

A Report by VINAYA Lab

Written by:

Tarek Akkawi - MRes Neuroscience

Edited by:

Sammi Rosenthal - MSc Digital Anthropology

Leah Palmer - BA Psychology

Fabio Pania - Msc Electronic Engineering

VINAYA is a London-based design studio and research lab. Along with creating new and

advanced technology, VINAYA prides itself on its comprehensive lab that works around the

clock to further evaluate the human mind. In preparation for ZENTA, the companys new

biometric sensing wearable, VINAYA performed extensive research on just how physiological

sensors reflect our present emotional state.

Emotions are a driving force in every persons life. Feelings such as anxiety or fear are on the

negative end of the spectrum while other feelings such as joy or affection are on the positive end.

The experience of these emotions leads to the actions performed by people everyday and thuscontributes towards our personal and overall development.

Similarly, were also regularly exposed to environmental stimuli. whether that is found in the

form of sights, sounds, or physical contact. These stimuli form the basis for specific behaviours

to emerge, and the subsequent actions performed determine whether the emotions initially felt

evolve positively or negatively. The contribution of emotions to the manifestation of specific

behaviors can be argued to be bilateral. Emotions may act as a driving force to the enactment of

behaviors and the consequences of ones behavior can result in the manifestation of emotions.

Therefore one of the greatest challenges in understanding human behavior is to understandhuman emotional experience. What emotions do we experience and under what circumstances?

How do emotions predict behavior? And how can ones emotional experience contribute towards

ones overall well-being?

All of the above questions have caused researchers to be interested in studying emotion and

determining a way to quantify it in order to expand our knowledge in this area. Emotion

Copyright 2016 Vinaya Technologies Ltd


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quantification aims to investigate the subjectivity of emotional experience and enhance the

validity and accuracy of mapping out emotional responses. From a methodological perspective,

this involves the use of non-invasive sensors that are capable of measuring specific physiological

responses originating from various organs such as the heart. The procurement of this objectiveinformation can inform us about the degree of arousal (physiological and psychological excited

state) and valence (aversiveness or attractiveness) of an event (Mauss 2009).

Before we attempt to understand how such organs contribute to our understanding of emotions,

we need to explore how such physiological responses emerge and the underlying technology

used to detect such responses. The autonomic nervous system (ANS) is responsible for

innervating different organs in the body such as the heart and the skin (sweat glands). The ANS

is divided into two branches, the sympathetic nervous system (SNS) and the parasympathetic

nervous system (PNS). The layout of the neural projections of SNS on the heart and sweat

glands enables the transmission of excitatory impulses as a result of a given stimulus. These

impulses will in turn adjust the activity of the heart and sweat glands depending on the nature of

the stimulus. Similarly, the neural projections of the PNS on the heart (but not the sweat glands)

enable the transmission of inhibitory impulses thus restoring the activity of the heart back to

normal (McCorry 2007)

Through sensors, data relating to heart and skin activity can be examined in the form of heart

rate, heart rate variability, electrodermal activity and skin temperature. Measuring the

physiological activity of these organs can provide insight into the activity of the ANS.

Traditionally, information regarding heart activity is retrieved using electrocardiogram sensors.

However advancements in technology have enabled alternative techniques such as

photoplethysmography (PPG). PPG uses light at different wavelengths that illuminates the

arteries. As the light reaches the arteries, the concentration of specific molecules, such as

oxygenated hemoglobin, will absorb a portion of the light at a specific wavelength, while

deoxygenated hemoglobin will absorb a portion of the light at the alternative wavelength. A

portion of the light reaches the detector and the device can estimate oxygen saturation levels

(SpO2) ( Mengelkoch, 1994). Additionally, information regarding pulsatile blood (blood volume

pulse) can be retrieved and provide insights into heart rate (HR) and heart rate variability

(HRV). Heart rate refers to the number of heartbeats within a given time frame while HRV

refers to the regularity of interbeat intervals across a given time frame (e.g. 1 minute).

To examine the reflection of emotion on the skin, the conductivity of the skin was tested through

electrodermal activity. Electrodermal activity refers to the variation of the electrical properties of

the skin as a result of sweat secretion. The sensors inject a small electric current and monitor the

voltage across the skin, thus measuring changes in the skin conductivity .When sweat is

produced as a result of sympathetic activity, the skin becomes more conductive. Skin

conductivity is characterized by tonic activity and phasic activity. Tonic activity marks the

background conductance level of the skin and varies between individuals. Phasic activity marks



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distinct fluctuation and is associated with event-related stimuli. Researchers focus on the

various characteristics of the phasic activity such as latency, amplitude, and recovery time and

relate each specific EDA response to a specific event.

Variation in skin temperature can also provide useful information for physiological responses.

Vessels carrying blood can either constrict or dilate. Vasodilation means that blood flow

increases and subsequently heat transfer is increased while vasoconstriction means that blood

flow is reduced and subsequently heat transfer is reduced.

Research has shown in more ways than one that emotions can not only be seen through

physiological observation, but can be studied as well. Over the years, researchers have been

attempting to determine the core dimensions involved in characterizing emotions. The main

dimensions used within research are valence, which is the attractiveness or aversiveness of a

stimulus, and arousal, which indicates the degree of physiological and psychological activation.

These two elements have been associated with the physiological parameters mentioned above.

For example, HRV has been associated with valence while EDA has been associated with

arousal. Although the above variables have been extensively used in research and are considered

to be the dominant variables in understanding emotions, they are not the only dimensions found

to underlie emotional experience. Other dimensions such as controllability and intensity have

also been used to a lesser degree, indicating the complexity of emotional responses.

As mentioned above, the physiology of different organs such as the heart or the skin can provide

us with useful information regarding ones emotional experience. For example research into

anger shows that a number of parameters in the HRV index decrease. This means that the

contribution of the parasympathetic branch decreases while at the same time the contribution of

the sympathetic branch increases. With regards to EDA, a similar outcome is observed -- an

increase in skin conductivity is reported during the experience of anger including both phasic

and tonic activity. This means that the contribution of the sympathetic branch towards sweat

glands is increased (Kreibig, 2010).

Anger is classified as a strong negative emotion accompanied by a high degree of arousal,

therefore, distinct physiological changes are noticeable compared to an individuals baseline. On

the other end of the spectrum, the emotional experience of affection, such as love or sympathy,

has been associated with a decrease in HR. This physiological response reflects an increase in

parasympathetic activity and a withdrawal of sympathetic activity. With regards to EDA, reports

indicate an increase in the tonic activity in skin conductance but no mention in the phasic

activity. This means that the emotional experience of affection is uneventful in the sense that the

activity of the sympathetic branch is relatively low. Affection is classified as a positive emotion,

and a direct comparison to anger illustrates the key differences in physiological responses.



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Quantifying emotions is not an easy task. Understanding and comprehending each emotion as

an entity under different circumstances is a challenge. However, using the means available at

this point, the physiological displays of emotion can still be clearly examined. As technology

progresses and advancements in the fields of sensors and machine learning take place, moreaccurate measurements and classifications are imminent.

References

- Braithwaite J.J., Watson G.D., Jones R. and Rowe .M., 2015. A guide for analysing

electrodermal activity (EDA) and skin conductance responses (SCRs) for psychological

experiments

- Kreibig, S.D. 2010. Autonomic nervous system activity in emotion: A review. Biological

Psychology. 84 . 394 - 421.

- Mauss I. B. and Robinson M.D. 2009. Measures of emotion: A review. Cogn. Emot.

23(2): 209-237

- McCorry, Laurie Kelly. 2007. Physiology of the Autonomic Nervous System. American

Journal of Pharmaceutical Education 71 (4). 78

- Mengelkoch L.J., Martin D. and Lawler J. 1994 A review of the principles of pulse

oximetry and accuracy of pulse oximeter estimates during exercise. Physical Therapy.

74(1). 40-49


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