Asleep at the wheel? Or not…?!?!? – II

One questions that begs an answer is “how do you measure sleep”…? Can you really measure one’s fatigue and sleep level?

Sleep is generally analyzed using an ensemble of instruments called polysomnography(PSG). The ensemble consists of electro-encephalography (EEG) to measure the brain activity, electro-oculography (EOG) to measure and monitor eye movements and an electro-myography (EMG) to measure muscle tone of the subject under supervision to determine the sleep stage.

Sleep is broadly divided into REM (rapid eye movement) and NREM (non rapid eye movement). The NREM sleep is divided into four levels with level 1 starting with the onset of sleep to higher levels of sleepiness. The features appear in blocks.

The definition of sleep stages are made traditionally with respect to the EEG patterns and the important features found in the EEG signal of each sleep stage is given below. The stages of interest here are ‘Stage-W’ and ‘Stage-N1’ since this is the stage where the subject goes from wakefulness to sleep, meaning drowsy state. It must be observed that these classifications are for that of stages of sleep. The sleepiness or drowsiness is found between ‘Stage-W’ and ‘Stage-N1’.

Each of the stage of sleep is defined by features that might be found in EEG recording. For instance stage one is signaled by the rising of theta activity and the fading of alpha activity. Stage two is characterized by the theta activity and the presence of sleep spindles, which occur due to the interaction between cortex and the thalamus. Stages 3 and 4 contain slow waves and delta waves. The difference between stages is determined by the feature composition of an epoch.

The definitions of sleep stages are based upon the EEG data that is obtained. The data is visually scored by dividing the data into epochs of specific time duration. The visual scoring has some disadvantages. First of which is the accuracy of the score since small variations in frequency cannot be easily spotted along with the fact of it being tedious.

Sleep stage

Description

Observed EEG pattern

Stage W Wakefullness Alpha waves  (8-13 Hz)
Stage N1 NREM 1 sleep Theta waves (4-7 Hz)
Stage N2 NREM 2 sleep Sleep spindles (11 to 16 Hz) and K-complexes
Stage N3 NREM 3 sleep Slow wave sleep- delta waves (typically 0.5-2 Hz)
Stage R REM sleep Rapid eye movements and low level EEG voltages

Table – Sleep stages classification and observed features

The definitions of sleep stages have been clearly addressed. But in the context of the current studies the emphasis is on the transition from stage 0 to 1 where the subject moves from wakefulness to sleep. The general standard testing methodologies are multiple sleep latency test and maintenance of wakefulness test. In multiple sleep latency test (MSLT) the latency between the start of the sleeping period to the initial signs of sleep is measured and the latency is used as a diagnostic value.

The maintenance of wakefulness test is similar to MSLT except that here a subject’s ability to stay awake rather than a subject’s tendency to fall asleep. Here again, the test is conducted using the ensemble of instruments called a polysomnograph (PSG). The problem with the above tests is the discrete nature of the results.

There are other scales of analyzing PSG data to classify sleep stages such as Karolinska Drowsiness Scale(KDS). There are also subjective scales of analysis of sleep stages such as Stanford Sleepiness Scale (SSS), Visual-Analog Scale (VAS) that use a scale of explained parameters where the measurement is generally introspective.

There are also other ways to measure onset of sleep such as standard deviation of lateral position of the vehicle during driving and also an ensemble of data such as speed variability, steering position along with lateral position are used to estimate the sleep stage. This parameter can be easily measured in simulator tests but can be difficult to measure in case of roads due to limitations imposed by sensor capabilities.

One other credible indicator of sleepiness is blink characteristic, especially blink duration and blink velocity. The eye blink duration especially has shown to have a very good correlation with the sleepiness level. There is sufficient data that indicates that blink duration, especially, to be a good indicator of sleepiness and show a direction link between Karolinska Sleepiness Scale(KSS) and blink duration. Thus blink characteristics when studied in relation with other known indicators of sleep would lead to efficient markers for sleep stage classification.

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A search for consciousness II

Often referred to as a philosophical rather than scientific concepts are the concepts of qualia, self and consciousness although consciousness is being scientifically investigated. But the the underlying fact as explained in the previous post was that of the feeling of being rooted to a body.

But is there a way to go from consciousness as a philosophical  concept to a more scientific one? Meaning, can it be measured? This question leads to an interesting answer. Yes! But it is only if there can be a communication with the brain that is being inspected.

Ok. Think of this statement. “Thinking is doing!”. Would you believe it? I’m pretty sure most would even stop reading the post now (if at all anyone is reading… ).

That statement is a scientific fact. And has to be understood in the correct manner. For eg., sometimes we do put ourselves in pretty bad situations in our dreams. Let’s we dream of a situation like this. A pretty girl is being chased by villians…its dark….late night probably(yes like the typical Indian cinema ) … You jump in….there’s a fight….you suddenly know how to fight BTW…and when the fight is over….you wake up…(you were expecting some more haan….). The interesting thing is that you might be sweating, atleast your heart rate is up and it seems like your just out of the gym although it was just a dream. Ever wondered why?

The way in which the brain works is thus. When we see a tiger in our room, say, we get really pumped up….and its common knowledge that our “Flight or fight” response takes over. But what we fail to question the chronology of two events:

1. Conscious fright feeling                                                                                                                2. Systemic response -such as sweating, heart rate increase etc.

Which comes first? Nope. It’s not a chicken-egg dilemma. It’s simply first the second and second the first. Confused..?!?!?  First there is a systemic response and next the conscious fright.

Ok..?!?! But how does that correlate with the previous example? Since the brain already computes the data and gets the body ready for an action-either fight or flight, before we even know that we are ready. So, by the same yardstick, we you dream of the situation which I described above, it can be seen that part of brain takes action to prepare the body for any response, only to reminded by another part that it’s a dream.

A look at the video that I referred to in the last post will show a peculiar experiment. The host is made to lie in an MRI scanner and asked to think he’s playing tennis. What exactly happens here is that part of the brain takes this information or request and sends it to the pre-motor cortex which starts planning the motor activity. Remember, “planning”. Which means it’s crunching some numbers and is really active. And what does an active area in the brain need? Oxygen-rich blood.

It so happens that with some very precise settings and some more number crunching on the computer with some algorithms, we will be able to detect this part of the brain which is oxygen hungry. This type of an MRI scan is called fMRI or Functional Magnetic Resonance Imaging. This does not need a special type of a scanner, but the system will use a different way to scan your body to find these active areas in the brain.

This is an extremely useful system, which could potentially help take life-death decisions, especially in case of locked-in patients, who are not able to communicate, but are able to receive data and process it in their brain.

In the video, watching somewhere between 18:00 to 25:00. The host is made to undergo an fMRI experiment, he’s fed with anaesthesia slowly and the fMRI activity is observed. What do you expect? Does still keep “playing tennis” even after he’s almost unconsciousness?

The lighting up of a part of the brain goes lower and lower as the anaesthetic dosage is increased. A part of the brain called the thalamus and basal ganglia are said to be the center piece of anaesthetic action. And there is some sort of a loop formed between the cortex or the outer part of the brain and the thalamus that forms the basis for conscious action which is famously called the thalamo-cortical loop. “But where does the consciousness reside?”- is precisely what a neuro-scientist wouldn’t like to be asked yet.

So, now that we know what the brain does….how is the information processed in the brain? Does the brain communicate like any of the other communication devices and methods we know of? And how does all this lead to the search for consciousness?

A search for Consciousness – I

A few days back I saw an episode of the famous show BBC Horizon – The Secret You. It was one of those quests to find consciousness…what it is…where it is…and how it influences us….Not just that…the end of the episode was a shocking revelation on how we make decisions.

Consciousness can be minimally defined as the subjective experience of sensation. It is interesting to note that consciousness enables two distinct and important  things,

  • It enables you to KNOW that you are experiencing the sensation
  • It enables you to know that YOU are experiencing the sensation.

A curious point here is that both sentences are the same, but the stress on the words are important.  The concept of consciousness enables us to experience and know that we are experiencing the sensation. To understand the philosophical and scientific background more clearly you can hear to an excerpt from a talk of Prof. V S Ramachandran.

The episode in context has an interesting opening experiment- the mirror self-recognition test. Here the subject, generally children between the age of 18 to 24 months (the average time by which humans attain the ability of self-recognition) are allowed to look at themselves  in the mirror and after a short period of time a small mark is placed on their face. The test is to check if the subjects try to remove the mark which is a sign of recognition of a significant change in their features.

This is not a new experiment which has its roots with none other than the Father of evolution Charles Darwin. The idea was used and formulated by Prof. Gordon Gallup Jr. He funnily states that he got the idea one day, when he was shaving and he thought if a chimpanzee would recognize itself on it!  He is said to have gone to zoos and conducted experiments to study the behaviour of animals by holding a mirror against their faces.

The catch though is that self-awareness/ recognition is not common to all animals. In fact it was suggested only the Great Apes possessed this unique and interesting capability, which even monkeys don’t possess. This idea was contested recently when researchers published findings which seemed to suggest that even dolphins have a similar capability, opening up the pandora’s box.

There are also a lot of philosophical musings related to this field which is now very much a part of every single religious philosophy. So, how do we get this ability? Why are we not born with it? This is probably one of the biggest questions facing the field of neuroscience today!

Asleep at the wheel? Or not…?!?!?

About five months back, I was briefed upon one of the most common problems in traffic management, which costs human lives, not just of the person who maketh the mistake but a many more who are unfortunate to be around, accidents involving people who are asleep at the wheel.

This is a tremendously disparaging problem, which needs to be addressed from not just the law enforcement point of view but also from an technological angle. The immediate idea that comes to our mind is some kind of a warning system that can ‘find’ the alertness level of a driver then a corrective action can be taken.

But wait….has no one cared to think on these lines…???  Ah….yes…there are a lot of like-minded researchers who are working to build some kind of a system that can achieve this. There has been some success from firms like Mercedes which is some good news. But there is always a fervent need for an improvement of systems.

Nevertheless, the real problem has been in predicting the alertness level of the driver before the subject can fall asleep. The key fact being that the standard techniques such as EEG only tell you what state a subject is in right now and using the data to predict the alertness level might be a little hard. Also, the very state of being plugged to atleast 10 electrodes does not seem very pleasant.

On this interesting research arena, the work I was/am engaged in for sometime is to build a framework to do real-time analysis of Electro-oculography signals. A very nice outline to what EOG is can be found here. It is also interesting to note that careful investigation of the EOG signals could well be used to predict the alertness level and the transition to drowsy state.

The problem though has been the question of real-time analysis. This has been the elusive issue. Now as I try to target this issue, I shall blog my experiences and some interesting details I learnt.

The emergence of convergence

We are in an age where cell-phones are used as cameras…used as organizer…playing games…as a music player… and beyond all – A social identity…!!!

How many of us still remember it was to call other people and speak to them when you are on the move…??? In fact the consumer has grown so cynical he wants anything and everything in it. I was astounded when I saw an Indian cell phone ad where Akshay Kumar uses a cell-phone as a beard trimmer…!!! 

This I think is not just in the mind of a common man, but also happening everywhere. Considering the field of neuro-science which has been considered as the bastion of medicos is now seeing people with many other majors making their foray into it. Similarly, neuro-prosthetics has attracted control engineers, electronics engineers and mechanical engineers with the core of the group formed by neuro-scientists. This sort of blurring in the “boundaries” between science is heartening as more the convergence, more the output.

It was no strange co-incidence that Francis Crick said “The ultimate aim of the modern movement in biology is to explain all biology in terms of physics and chemistry“. Although some call this reductionism and proclaim biology to be an autonomous science, we have arrived at a critical juncture where we get a feeling that no science is autonomous. It is a really interesting prediction that Francis Crick made years ago.

So, is this phenomena just confined to science ? A few weeks back when the world leaders met at the World Economic Forum, I heard an interesting talk from the legendary investor, philanthropist, billionaire  George Soros. He drew an interesting connection between climate change, inflation, food shortage and micro-economics. This was really a huge insight for me into the field of international economics.

When I was thinking about the relationship he drew I was reminded about the words of our then President A P J Kalam at SASTRA. He spoke at length about the convergence of Nano, info and biotechnology and asked us students to brace ourselves to work in highly inter-disciplinary environments.

This convergence will definitely bring targeted research better results. It all burns down to the recipe…!!!