Making Sense of the Senses!

If you are trying to understand the world beyond your body, it’s probably a good idea to also understand just how your observations are being made and then interpreted. Our brains process a lot of sensory information, but interpreting it is a lot more fluid and fallible than you might believe!

First of all, there is no ‘person’ inside your head looking through a TV screen into the outside world through your eyes.

Sensory information is received in small bits of impulses traveling along neurons. A visual scene dissolves into clusters of rod and cone cells in the retina that sense edges, colors, and other elemental features of what you are looking at. These qualities are not stored in the visual cortex adjacent to each other like pixels in a picture, but grouped together by thematic features. It is only at the next level of neural connections (called synapses) that associations between areas in the visual cortex are made in order to identify archetypical objects such as cars, houses and, yes, grandmothers! These neurons also make many different synaptic connections along the way to help process the information flow long before you perceive it as an integrated whole. This figure shows, for example, a few of the neural pathways that connect the visual cortex regions ( V1, V2, V3) all the way to the prefrontal cortex (PF).

What you see is sometimes not always what you get. Your neural networks may actually remove information from your conscious perception of the world. A frog’s retinas only pass information to its brain when something is moving in the visual field. Its brain doesn’t even GET the basic information that things like perfectly edible flies are standing still on a nearby leaf! Only when they move does the retina communicate to the frog’s brain that there is a fly ‘out there’ to go after and eat. You know that ‘blind spot’ in your eye? The brain fills it in with fabricated information so that you do not see a black spot the size of a quarter at arms-length. Our brain is actually lying to our conscious perception of the world!

Second of all, many of the neurons at the lowest level make connections to the limbic system and are ‘tagged’ with many different emotional states .

The most important of these taggings being the self-preservation, fight-or-flight response. For example, there is very high survival value to quickly tagging a distant shadow as either a predator or a non-predator. Not all shadows will be a lion, but in the grand scheme of evolution even a rule-of-thumb that works only 10% of the time can mean the difference between vital genes being passed on to the next generation or not. This identification has to be made very quickly before you have time to logically consider all the non-threatening possibilities for what the shadow might actually be.

This tendency towards making snap decisions that over-ride time-consuming reasoning has high survival value and is hard-wired into our brains, but it also screws things up as we apply the same data to rationally understanding the world around us. The best case of this is in the eyewitness reporting of crimes. Eyewitnesses are almost always in a highly-emotional state, and great care has to be taken in the courtroom to compare accounts and distill from them the actual facts. Sometimes eyewitness accounts have to be thrown out entirely.

Another big problem with the brain is that it has a nasty habit of using the same neural circuits to handle different tasks. This leads to some extremely crazy situations.

We all like to visually imagine ourselves in different situations as we day dream, read a good novel, or are fast asleep in bed. These visual images and other imagined relationships often use the same circuitry needed for carefully examining the outside world and making sense of it. What this means is that there is actually a neural connection between our imagined world and the hard-rock world we live in. Most people can easily distinguish the difference, but sometimes our imagination, dosed with the limbic system’s associations, can confuse what we are actually seeing or experiencing, not based on an actual experience, but based instead on an imagined one. You can actually improve some elements of sports performance by internally visualizing in detail the actions you want to perform. It seems that imagined activity can train the cerebellum almost as well as the actual act!

Our brain and sensorium have to work together to identify patterns that help us survive, or at least not get injured too badly. There can be some sloppiness in this process that allows a few people to misunderstand gravity and walk out a 35th floor window, but we have evolved so that this is a very rare occurrence. But still, there are many ways in which human perceptions can be misinterpreted or even distorted by the brain as it tries to process billions of bits of information every second against a wash of emotions and other states-of-mind.

In the next blog, I will describe how strokes have helped neuroscientists understand how human brains create consistent models of the world, and how this process can break down with some rather unbelievable results!

Check back here on Sunday, November 27 for the next installment!

Making Sense of the World

Ask just about anyone how many senses a normal human has and the immediate answer will be five: sight, hearing, taste, smell and touch. By the way, I always manage to forget that last one for some reason!


The oldest mention of this particular list goes all the way back to the Hindu Katha Upanashad written in the 6th century BCE. Even Shakespeare mentions them as the ‘five wits’ in King Lear! But a lot has happened since way back when. The entire idea of ‘scientific research’ came into its own, and now there are a whole lot of other human senses that have been added to the classical mix we learn in grade school.

Sense Number Six: You can detect heat and the temperature of any object you touch or are placed close to. Your skin has thousands of little ‘receptors’ that individually detect the attributes of cold and warm.

Sense Number Seven: You can detect whether you are standing upright or lying down through the balance receptors in your inner ear, which are hollow loops filled with liquid. The movement of this liquid in each loop is sensed by neurons and tells the brain your head’s position in 3-dimensions.

Sense Number Eight: Pain is a sense that is not just the overloading of touch or pressure receptors in the skin. In fact we have three different groups of pain receptors that signal internal organ damage, external skin damage, or damage to our bones and joints.

Sense Number Nine: Another overlooked sense is proprioception: the ability for you to sense the orientation of your body and limbs in 3-dimensional space. Without this very important sense, you would not be able to walk, jump, dance, type at your keyboard, or a thousand other activities that make up your life.

Sense Number Ten: Chemoreception is the ability of your body to detect changes in the foods you eat, and signal the body to reject that food if it fails to pass certain internal tests. This sense can cause your stomach to contract, cause you to vomit, and cause changes in your vascular system,: ‘OMG I just ate rotten fish!’

Sense Number Eleven: Although not a specific cellular feature of the nervous system, every normal human has a perception of their place in time. Part of this is our 24-hour circadian rhythm, but through brain activity, we have a timing sense that allows us to sing, dance and play a musical instrument correctly. It also helps us locate ourselves in the present moment within our accumulated memories.

Sense Number Twelve: Outside versus inside. We have a unique sense of where our body ends and where the outside world begins. Without this, we would identify every sensory stimulus as originating within our body, and that our body has grown to encompass the entire physical world ‘outside’. More on this later!

Sense Number Thirteen: Friend versus Foe. Our cells have proteins on their surfaces that identify to our immune systems whether a cell is part of our own body, or is a foreign interloper.

If you think this range of senses covers all of the biological possibilities, there are many more senses that some animals have, and perhaps we also do at some very, very low level.

Sharks and some other fish can detect electrical fields with specialized receptors in their skin. Many animals can detect earth’s magnetic field and use this to navigate. Bees can detect polarized light, which they also use for navigation. The vomeronasal sense allows animals to detect the pheromones of other members of their species and use this to identify a mate in estrus, or members of their own clan. Plants can directly sense gravity and use this to help them grow upwards. Both animals and plants can detect slight changes in air moisture to precisely identify where a source of water is located.

The earliest known senses were developed by single cells to detect changes in various chemical concentrations in water – a potential food source. But by far the oldest sense among complicated organisms is vision. This particular sensory skill has been re-invented literally hundreds of times by evolution across millions of different organisms.

So there you have it. Senses are a brain’s way of detecting an organism’s place and situation in the physical world. Amazingly enough, human brains do not take-in all of the information generated by our senses. If it did, we would be in a near-constant state of epilepsy! So what our brains do is to actively suppress most of the sensory information our receptors generate before it even reaches our consciousness. In fact, if you were to look at the neural activity of the brain, far more neurons are devoted to the brain talking to itself, than checking on what’s happening in the outside world!

So what does the brain do with all of this information?

That will be the topic of my next blog!

Check back here on Friday, November 25 for the next installment!

The Universe and Etc!

Hi there!

It’s exciting to start a fresh new blog project. It’s kind of like your first day in class with a new pencil and a binder with blank sheets of paper. Even as late as graduate school at Harvard I always found that first day of class exciting and filled with such promise.

You have probably GOOGLEd me by now and discovered I am a professional astronomer and educator. No I am obviously not one of those famous ones you may know by name. There are thousands of astronomers and physicists in this country, many of them far more famous than I am, but chances are you have never actually met one. Even fewer people have astronomers as members of their families!


So here I am, one of those back-roads professional astronomers who has also spent a lifetime studying space and delving deeply into the nuances of the physical world. If you decide to make it a habit of reading my blogs, you may be pleasantly surprised how a slightly different perspective might help you see the world around you a bit more clearly. I hope you will at least appreciate the connections that I see, and why they have been such a source of joy and wonderment to me all my life. As they say, it is not the destination that matters but the journey!

I have always been interested in science: the exploration of the physical world. My mother used to tell me that when she would take me out into the fragrant spruce forests surrounding my hometown Karlskoga in Sweden, she would always have to empty out the rocks in my stroller that I collected along the way. This evolved into a progression of interests leading to a passion for astronomy by 5th Grade.

But as I was exploring the hard facts and theories of astronomy and physics, it was hard for me to give up my interests in ESP and UFOs. For you see, well into middle school I used to plot the positions of UFO sightings on a map of the USA on my bedroom wall, and marvel at the descriptions of the many sightings reported in newspapers and magazines. By high school,  I was reading Carl Sagan’s ‘Intelligent Life in the Universe’, but I was also reading von Daniken’s  ‘Chariots of the Gods’ and Frank Edwards ‘Stranger than Science’. As a Junior in college, I had my own experience of sighting a UFO in the twilight sky.    I also developed an interest in ESP because my Swedish mother beguiled me with many family stories of spirit sightings and telepathic incidents during my early childhood. In high school, my friends and I conducted séances…which [fortunately?] failed, and I had my own experiences with family ghosts and inexplicable events.

Then something peculiar happened around age 23 when I was beginning my Senior Year at UC Berkeley working on my degree in astronomy.  By then, these interests in ESP and UFOs had subsided and simply vanished from the palette of issues I wanted to keep up with.  What had happened?

As I became more steeped in science, its history, its many spectacular successes, and endless rounds of homework to learn  physics from the inside out, I spent less and less time with ideas that entertained, but had far less substance and productivity to them. At some point, the hard data and objective mathematical rigor of science became a far more compelling story than the endless presentations of subjective evidence from ESP and UFO enthusiasts. It seemed to me  that there was not one shred of hard evidence about ESP and UFOs that could not be dismissed as wishful thinking, unsubstantiated anecdotes, statistical variation, or out-right fakery.


In science, advances are made when data is obtained under controlled, repeatable conditions by parties whose only goal is to collectively create an accurate model of how the world works. I decided in college that this was drastically different from ‘ghost chasers’ and UFO hoaxers, who often flooded these subjects for fame and personal gain. But there was one subject area that I immediately gravitated to, that replaced all of these entertaining ideas: Brain research.

I am going to try to explain advances in our understanding of both the physical world and our mental world in a series of blogs that my non-scientist mother would have enjoyed reading. If you want more extensive details, you are free to GOOGLE the words and topics and look to other professionals for explanations who are also popularizers. I will recommend their insights and explanations as my blogs develop.

So where do we start?

Well, for my next few blogs, let’s begin with the brain and how we perceive and make sense of the world around us. That, after all, seems to be the biggest ingredient in creating a rational picture of the world around us.

It is also the biggest impediment!

Return here on November 21 for my next blog in this series!