Here I intend to document the work done by me as a part of my Masters Project at Indian Institute of Science , Bangalore . The project is titled 'Brain in a Box' . The aim of this project to exploit the computational power of a neural network to do a task . We intend to culture neurons in a dish with a micro electrode array and then use this system for our studies . It is hoped that it would further our understanding about the behavior of an ensemble of neurons .
The project kicks off with literature survey . Here is a summery of what I could gather going through various papers on the topic .
Here is a link to the presentation that I made on this topic .
The Brain . How it works ? This is a question that continues to fascinate a number of researchers working in a number of fields . The answer is sought out for a number of purposes . To understand why we are the way we are . To help people suffering from various disorders . To improve our capacity . To engineer systems that can mimic arguably the best of them all .
Where does 'I' come from ? How do we see , hear , feel , think ? We would like to help people with disabilities . To make the blind see , the deaf hear , give the power to speak , provide limbs to those who don't have, cure epilepsy . We would like to play God . We demand a better way to communicate with our salves - the computers . We want our systems to have some of our capacities . To learn , to adapt , to be resilient , to execute complex tasks without detailed instructions,to comprehend.
We have been able to map various paths of action in the brain . We understand some mechanisms that help us see and hear , to send commands to our limbs . Yet this is at a basic level . We have made devices that connect to brain , artificial limbs that move at our command . We have been able to train monkeys to move levers by thought . These are still nowhere near human abilities . We have made very powerful computers. Yet these are not a millionth of our capacities and nowhere near our efficiency in doing so.
These are some of the things that motivate people to look for the answer to question . The Brain . How it works ?
We know(/think?) that the 'computational' part of the brain is made of cells called neurons . They are interconnected and play an orchestra that results in everything . The neuron (cell) has mainly three parts morphologically . The cell body or soma , the dendrites with synapses to which other neurons connect to and the axon which helps the neuron to connect to others. They work by moving a number of chemical ions / molecules / complex compounds in and out of the cell . Observing these movements give us some idea regarding what is happening . We have devised many ways to do this . Since we are very good with electricity , it is the major source of our information . Movement of ions cause electric currents . These currents can be detected and recorded using electrodes and appropriate electronics . We try to infer things based on these recordings .
For electrical recordings , we have chiefly two methods intracellular and extracellular . Intracellular recordings allow us to record the activities of a single neuron in detail . Such recordings have helped in understanding the mechanisms of operation of single neurons in great detail . Extracellular recordings are done by inserting the electrodes into a medium containing the neurons . For example , inserting an electrode into the brain (of cats , monkeys , insects ) . These electrodes then pick up activities from number a of neurons . We also do recordings by placing electrodes on the scalp which pick up some of the underlying electrical activity . We also have multiple electrodes inserted into a region / over an area . This helps us pick up activity from a number of different sites and thus gain more information about the working of an ensemble of neurons .
Recordings from a single neurons have helped us to understand the functioning of these basic units . However , we still lack ways to understand the properties that emerge when these from a networks . We hypothesize that it is these emergent properties that give us all our power . Computational models have helped in this regard . Several models have been tried out to explain various properties . Directly recording and analysing activities from the brain is a very challenging task .
Towards this end , one approach has been to culture neurons in a dish and allow them to form networks . The dish has an array of electrodes .Properties of these networks are then studied by giving stimuli and recording responses. It has been argued that giving a body to this brain would help us understand more . A number of interesting projects have been done towards this end . People have connected these neurons to a robot with sensors . The neurons drive the robot and get signals from the sensor. The network is trained to move the robot in such a way to avoid obstacles detected by sensors . There has been efforts to study the capability of these networks to learn a task (plasticity) and to retain .
For the culture to exhibit a 'behaviour' it must be able to sense the environment around . Hence the information from the outside world must be given as stimuli to network . This would be based of the changed in environment as a result of the action of network . For example , obstacle is nearing / going away .
The next post adds some details to the above mentioned outline of steps .
(Note : None of the images are mine, they have been picked up from various sources in the Internet Thank you all . I have made some block diagrams)
Here is a link to the presentation that I made on this topic .
Motivation
The Brain . How it works ? This is a question that continues to fascinate a number of researchers working in a number of fields . The answer is sought out for a number of purposes . To understand why we are the way we are . To help people suffering from various disorders . To improve our capacity . To engineer systems that can mimic arguably the best of them all .
Where does 'I' come from ? How do we see , hear , feel , think ? We would like to help people with disabilities . To make the blind see , the deaf hear , give the power to speak , provide limbs to those who don't have, cure epilepsy . We would like to play God . We demand a better way to communicate with our salves - the computers . We want our systems to have some of our capacities . To learn , to adapt , to be resilient , to execute complex tasks without detailed instructions,to comprehend.
We have been able to map various paths of action in the brain . We understand some mechanisms that help us see and hear , to send commands to our limbs . Yet this is at a basic level . We have made devices that connect to brain , artificial limbs that move at our command . We have been able to train monkeys to move levers by thought . These are still nowhere near human abilities . We have made very powerful computers. Yet these are not a millionth of our capacities and nowhere near our efficiency in doing so.
These are some of the things that motivate people to look for the answer to question . The Brain . How it works ?
What we do
We know(/think?) that the 'computational' part of the brain is made of cells called neurons . They are interconnected and play an orchestra that results in everything . The neuron (cell) has mainly three parts morphologically . The cell body or soma , the dendrites with synapses to which other neurons connect to and the axon which helps the neuron to connect to others. They work by moving a number of chemical ions / molecules / complex compounds in and out of the cell . Observing these movements give us some idea regarding what is happening . We have devised many ways to do this . Since we are very good with electricity , it is the major source of our information . Movement of ions cause electric currents . These currents can be detected and recorded using electrodes and appropriate electronics . We try to infer things based on these recordings .
Recording
For electrical recordings , we have chiefly two methods intracellular and extracellular . Intracellular recordings allow us to record the activities of a single neuron in detail . Such recordings have helped in understanding the mechanisms of operation of single neurons in great detail . Extracellular recordings are done by inserting the electrodes into a medium containing the neurons . For example , inserting an electrode into the brain (of cats , monkeys , insects ) . These electrodes then pick up activities from number a of neurons . We also do recordings by placing electrodes on the scalp which pick up some of the underlying electrical activity . We also have multiple electrodes inserted into a region / over an area . This helps us pick up activity from a number of different sites and thus gain more information about the working of an ensemble of neurons .
Recordings from a single neurons have helped us to understand the functioning of these basic units . However , we still lack ways to understand the properties that emerge when these from a networks . We hypothesize that it is these emergent properties that give us all our power . Computational models have helped in this regard . Several models have been tried out to explain various properties . Directly recording and analysing activities from the brain is a very challenging task .
General Steps in experiments using multi-electrode-arrays
Here I briefly mention the techniques that are used . I hope to detail them as and when we use these techniques in our project
Record
We record the activity from the culture to make some inferencesProcess
We need to identify spikes in the recorded data since we believe this contains the information about neural processing . Hence the next stage involves processing the data to identify spike from the neurons and time it occurred .Analyse
Next stage involves analysing the timing of spikes from various neurons to infer something about the activity of the networkAct
This involves generating an output corresponding to the task we intend the network to perform . This involves a mapping from the inferred activity of the network. For example the task may be to drive the motors of a robot to avoid obstacles . Then the mapping would be from the activity to motor speeds .
Feedback
For the culture to exhibit a 'behaviour' it must be able to sense the environment around . Hence the information from the outside world must be given as stimuli to network . This would be based of the changed in environment as a result of the action of network . For example , obstacle is nearing / going away .Train
This involves training the network towards a goal if the exhibited behaviour is not in agreement with the desired behaviour . We would like to train the network to move away from obstacle if it moves towards it .The next post adds some details to the above mentioned outline of steps .
(Note : None of the images are mine, they have been picked up from various sources in the Internet Thank you all . I have made some block diagrams)
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