Burger_083107 - Biosciences in the 21st century Lecture 2 Innovations and Challenges Dr Michael Burger Outline Review of last time Organization of

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Unformatted text preview: Biosciences in the 21st century Lecture 2: Innovations and Challenges Dr. Michael Burger Outline: Review of last time Organization of the nervous system (in brief) The mapping concept Bionic implants and our cyborg future Auditory function and cochlear implants Restoring paralysis: promising technology Nervous system is segmented in invertebrates Each segment is controlled by its "own" bit of brain and in vertebrates........ Human stage 11 embryo Each segment has repeatable structures http://embryology.med.unsw.edu.au/wwwhuman/Stages/Stage10L.htm Each segment has its own inputs and outputs Afferents (inputs; i.e. sensory neurons) Efferents (outputs; i.e. motor neurons) Let's consider the somatosensory system.... each vertebral segment is connected to a particular patch of skin The area of skin innervated by one segment is called a "dermatome" You will see that this organization is preserved at every level of processing The brain (also segmented) has its own afferent and efferent nerves The neocortex is an elaboration of the foremost segment, and it has a highly organized structure The cortex has functionally distinct regions http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif The cortex has functionally distinct regions a closer look at the somatosensory cortex... http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif The somatosensory and motor cortex contain orderly maps of the body surface somatosensory Motor The representation is distorted because more brain tissue is devoted to the most sensitive areas This distorted representation gave rise to the concept of the homunculus or "little man in the brain" This distorted representation gave rise to the concept of the homunculus or "little man in the brain" The point is: the brain is organized into maps of important features and functions The point is: the brain contains maps of features and functions The more that we understand about the structure and function of each region of the nervous system, the more likely we are to be able to develop an intervention when things go wrong..... Neurological Medicine: Today: mainly concerned with limiting damage as it happens, or slowing degenerative processes. Sometimes medication can correct deficiencies in neurotransmitter systems etc. Neurological Medicine: Today: mainly concerned with limiting damage as it happens, or slowing degenerative processes. Sometimes medication can correct deficiencies in neurotransmitter systems etc. Long term: stem cells, tissue engineering, gene therapies will correct the mechanisms of disease, not just the symptoms Neurological Medicine: Today: mainly concerned with limiting damage as it happens, or slowing degenerative processes. Sometimes medication can correct deficiencies in neurotransmitter systems etc. Long term: stem cells, tissue engineering, gene therapies will correct the mechanisms of disease, not just the symptoms The intermediate term: current research in nanoscale engineering, computer science, and neuroscience will lead to technological interventions that provide solutions to neurological disease The dawn of the brain machine interface... welcome to your cyborg future.... Sound is defined by frequency The most successful machine/neuron interface thus far is the cochlear implant Outer ear Middle ear inner ear (neural) The cochlea Organ of Corti -hair cells -support cells -basilar membrane -Primary Auditory Afferents!! Organ of Corti -hair cells -support cells -basilar membrane -Primary Auditory Afferents!! The inner ear translates stimulus frequency to a topographic place This "tonotopic" organization is the primary mapping feature in the auditory brain The most common cause of hearing loss is hair cell damage and death; in mammals they do not regenerate normal inner hair cells damaged outer hair cells The cochlear implant is an electrode array positioned to stimulate the auditory afferents directly, in the abscence of hair cell function Cochlear Implant Two elements External Internal A microphone A speech processor A transmitter and receiver/stimulator An electrode array Bypasses damaged part of the ear Directly stimulates auditory nerve Age Matters Vocabulary Normal ears < 2.5 years 2.5-3.5 yrs 3.6-7 yrs 7.1-10 yrs The point here: deaf children can recover near normal language ability if (Connor et al. 2006) they are implanted early enough The limit of implantation, is frequency resolution because todays best electrode has a max of 23 inputs to the ear Normal Hearing The limit of implantation, is frequency resolution 6 channel hearing The limit of implantation, is frequency resolution 4 channel hearing Cochlear implants compress sound into bandpass filter channels, but only a few are needed to make sense of the world.... Frequency 32 16 8 4 2 1 Time Frequency Cochlear implants compress sound into bandpass filter channels, but only a few are needed to make sense of the world.... Frequency 32 16 8 4 2 1 # of band filters Time Frequency Cochlear implants compress sound into bandpass filter channels, but only a few are needed to make sense of the world.... Time Frequency 1 2 4 8 16 32 music appreciation requires many more channels Frequency 4 8 16 32 Time These audio demos available at... http://www.hei.org/research/aip/audiodemos.htm music appreciation requires many more channels Frequency Johnny Cash 4 8 16 32 Time These audio demos available at... http://www.hei.org/research/aip/audiodemos.htm New technology is allowing researchers and their patients to control machines with only the power of thought, and the help of computers The cortex has functionally distinct regions a closer look at the Motor cortex... 1.Motor neurons fire predictable patterns before movement http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif The cortex has functionally distinct regions 2. computer programmers are getting sophisticated enough to have algorithms that interpret the output of 100's of neurons http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif The cortex has functionally distinct regions 3. computers can then send complex commands to robots http://www.emc.maricopa.edu/faculty/farabee/BIOBK/cerebrum_1.gif New tiny electrode arrays can sample the activity of many neurons at once, and cause minimal tissue damage In 1999, researchers succeeded in demonstrating that a rat could control a single arm robot with signals from motor cortex neurons Chapin et al. Nature 2:664 By 2002, researchers demonstrated that monkeys could control robot arms in 3D and computer cursors on a monitor with brain activity alone Lebedev and Nicolelis 2006 Trends in Neurosciences 29:536 Human brain implants are just around the corner with some devices already in clinical trials.... Lebedev and Nicolelis 2006 Trends in Neurosciences 29:536 For videos of human brain/computer interface technologies.... http://bci.tugraz.at/downloads.html For video of monkey brain/computer interface technologies.... http://www.metacafe.com/watch/774732/ monkey_control_robot_with_brain/ Summary: The brain is highly organized into functional maps (somatotopic, tonotopic, etc.) where neighboring neurons process similar information One function of the ear is to transmit sound frequency information to the brain Auditory transduction is achieved by hair cells that translate mechanical energy into electrical energy Cochlear implants bypass hair cells by stimulating auditory nerve fibers directly Summary: Small electrode arrays and computers can bypass motor systems to operate prosthetic devices etc. This strategy is highly likely to help patients with neurological disease. ...
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This note was uploaded on 03/09/2008 for the course BIOS 95 taught by Professor Varies during the Spring '08 term at Lehigh University .

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