Loading…

Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Like this presentation? Why not share!

Neuroscience

on

  • 481 views

 

Statistics

Views

Total Views
481
Views on SlideShare
481
Embed Views
0

Actions

Likes
0
Downloads
2
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • Brainstorm… during the latter part of the 20th century, the study of the brain moved from being just a branch of biology and psychology to an interdisciplinary field called "neuroscience" which is now at the heart of each discipline. Within this new framework, the scope of neuroscience ranges from genes to cognition, from molecules to mind. It is an incredibly complex field…even down to the structure of neuroscience university departments.
  • field began in 1970, when The Society for Neuroscience( professional association of neuroscientists) was founded, incorporating all the various branches. **Neuropsychology: branch of psychology that deals with the relationship between the nervous system, especially the brain, and mental functions such as language, memory, and perception. Cognitive neuroscience = understanding the nature of thought. How the brain enables the mind. 1994 –cognitive neuroscience society formed. "Cognitive Neuroscience--With its concern about perception, action, memory, language and selective attention---will increasingly come to represent the central focus of all Neurosciences in the 21st century."   -Eric R. Kandel, M.D. (Nobel Laureate) Neuro-pathology: neurological diseases and treatment – alzheimers, parkinsons, MS, etc. Neuro-Physiology: studies functions of Nerv. System Neuro-Endocrinology: studies glands and related disorders Neuropsychopharmacology: R&D of psychoactive drugs to treat neurological disorders – e.g. depression Neuroanatomy, neuroImagery: pretty obvious. **Molecular neurobiology : how parts of the nervous system work at the cellular level. I will be focusing on *** By implication, neuro scientists study the nervous system. who knows what the nervous system is?
  • 4 brain regions: Parietal lobes , temporal, occipital, Frontal Lobes = abstract reasoning, planning How exactly does memory occur? After years of study, we can say that “memory involves a persistent change in the relationship between neurons” the Structures believed to be important for various kinds of learning and memory include the cerebral cortex, amygdala, hippocampus, cerebellum, Areas of the left hemisphere are known to be active in speech and language.
  • Learning is the process which produces memory Classical: associative learning in which there is no contingency between response and reinforcer. This situation resembles most closely the archetypal experiment from I. Pavlov in the 1920s, where he trained dogs to associate a tone with a food-reward (see figure). Operant: type of associative learning in which there is a contingency (DEPENDENCE) between the response (LEVER PRESSING) and the presentation of the reinforcer (FOOD). //Technical explanation(skip): the subject is able to generate certain motor-output, (the behavior B, e.g. running around, cleaning, resting, pressing the lever). The experimenter chooses a suited output (e.g. pressing the lever) to pair it with an unconditioned stimulus (US, e.g. a food reward). Often a discriminative stimulus (SD, e.g. a light) is present, when the R-US contingency is true. After a training period, the subject will show the conditioned response (CR, e.g. touching the trigger) even in absence of the US, if the B-US association has been memorized. Such instrumental or operant conditioning is opposed to Pavlovian or "classical conditioning", where producing a response has no effect on US presentations.  ***According to Pavlov, skinner and other early learning theorists, the connections established by classical and Operant (instrumental) conditioning are arbitrary. Just about any conditioned stimulus can become associated with any Unconditioned stimulus , and just about any response can be strengthened by any reinforcer. (skinner was fond of showing people his masochist pigeon). Challenged by fact that animals are biologically prepared to learn certain relations more readily than others, and some forms of learning are species specific.
  • Again, learning produces memory, numerous studies have led neuropsychologists to categorize memories into several types: Dispositional = There is an effect of a past experience without the person being aware. Remembering without thinking about it at the time of remembering. Accounts for fact that familiarity increases credibility – i.e. illusion of truth. **Procedural = “knowing how” –to ride a bike. It is expressed in skilled behavior and learned habits. behavioral tasks are established where performance of them depends upon the brain being able to represent relevant cues to enable it to recall “how to ride a bike” Associative learning, as we saw before would be associated with Explicit Memory, of which there are two kinds: Generic = “knowing that” . memory for items of knowledge (e.g. the capital of France is Paris) independent of when they’re learned Episodic = associated with emotion, or other sense. e.g. flashbulb memories associated with a very strong emotion. - 9/11 Episodic memory is currently under significant study, particularly with it’s connection to the amygdala, which is connected to emotional aspects of memory. important factor influencing what is stored/learned and how strongly, is the type of reinforcement (reward or punishment) given to the behaviour I.e.. Reinforcement can determine what behaviors an organism will learn and remember. The amygdala appears to play an important role in these memory events, as evidenced by individuals with damage to the amygdala happening to be incapable of fear-conditioning. Evidence for such a categorization of Memory comes from studying patients with specific memory failures: e.g. Gene – head injury in motorcycle accident, damaging large areas of frontal lob, including left hippocampus, can remember no events from his life –only that he owned 2 motorcycles, a car, and his family had a summer cottage they went to on the weekends…i.e. He has massively disrupted episodic memory, but generic memory is intact. (1996) But other patients show the reverse pattern: due to encephalitis, one patient lost her memory of many common words, and traits of innanimate objects, but remembered her wedding day, her father’s death, and other specific past (episodic) memories. This supports the theory that there are different types of memories –no doubt produced by different learning circumstances, and that these different types of memories could be supported by distinct brain “systems” , like the hippocampus, amygdala, etc. but this does NOT mean that we can think of these brain sites as “memory Centres”. Remembering involves many steps, which in turn may involve many different brain regions working together. We can observe this complexity with several techniques:
  • These are some imaging techniques used to study brain-physiology: (Quick mention): Case Studies of amnesiacs, epileptilepsy, Agnosia, autism, lesions, etc. Gene Splicing: involves genetic engineering of animals (rats usually) with specific brain pathologies Positron Emission Tomography (PET) Scan -radioactive glucose is injected into the blood stream. The most active neurons absorb more of the radioactive glucose, so it is easy to take a picture of the brain's activity during different tasks. EEG: since brain = 10 billion interconnected nerve cells in ceaseless electrochemical activity, the brain generates brain waves that can be electronically detected and recorded by electroencephalography Magnetic Resonance Imaging (MRI) Scan With an MRI, high frequency alternating magnetic fields are generated that cause the nuclei of the neurons to line up, this is used more to study morphology, as magnetic sensors then detect the different resonance patterns of nuclei of specific tissues, which are then resolved by computer. Functional magnetic resonance imaging (fMRI), “ based on the fact that oxyhemoglobin, the oxygen-carrying form of hemoglobin, has a different magnetic resonance signal than deoxyhemoglobin. Activated brain areas utilize more oxygen, which decreases the levels of oxyhemoglobin and increases the levels of deoxyhemoglobin, and within seconds the brain microvasculature responds to the local change by increasing the flow of oxygen-rich blood into the active area. This leads to an increase in the oxyhemoglobin-deoxyhemoglobin ratio, which forms the basis for the fMRI signal in this technique. Because of its high spatial resolution (millimeters) and high temporal resolution (seconds) compared to other imaging techniques, fMRI is now the technology of choice for studies of the functional architecture of the human brain.” CAT: computerized axial tomography = X-ray brain area at different angles, use computer program to make composite. ****** ****** Now, Evidence From PET scans support the idea that there is no “seat of memory” in the Brain. E.g. When you are actively trying to remember something (strategic retrieval= actively searching for a memeory), greater activation is shown in the prefrontal cortex, but during assosiative (automatic) retrieval – e.g. Who is the current president of the U.S - greater activation occurs in the nearby temporal lobe (hippocampus). Two different brain regions are activated depending on what kind of memory you’re searching for. The same thing is confirmed by studying different types of amnesiacs. Damage to the right prefrontal results in memory loss + memory error (confabulations), suggesting a role for the pre-frontal area in memory-retrieval. damage to this area also impairs all processes relying on working memory. Damage to the occipital, temporal lobes impair person’s ability to retrieve specifically visual memories (e.g. what another person’s face looks like), still other forms of remembering seem to rely on still other areas. So it seems clear so far that no specific brain area handles the sole job of remembering, instead – like most cognitive operations, it requires the close cooperation of many sites, each performing it’s own function. But how does this communication happen?
  • Transduction: - Nerve cells, or neurons, in the brain communicate with one another by way of chemical substances called neurotransmitters. When the cell body receives an above threshold stimulus, the neuron fires by transmitting an electrical signal along its axon, triggering the release of neurotransmitters stored in synaptic vesicles at the axon terminal. The neurotransmitters cross the synaptic gap, and bind to receptor molecules. This will cause certain ion channels in the membrane of the second neuron to open or close. E.g. some neurotransmitters open channels to sodium (Na+), decreasing the voltage across the membrane as the ions flood to the other side of it. This makes the membrane less stable, and once the voltage is reduced enough, the excitation threshold is reached and the action potential in the second neuron is triggered, causing the impulse (electrical signal) to speed down the second neuron’s axon, etc. The opposite effect is also true. I.e. while a large concentration of positively-charged particles entering a receiving neuron tells it to pass on the message, a large concentration of negatively-charged particles entering the receiving neuron will inhibit it from passing on the message. Somehow, the brain keeps tight control of this message delivery system to avoid communication chaos. A single receiving neuron has thousands of receptor sites and may receive many different signals at once. Each neuron adds up the incoming signals and determines whether or not to pass the information along to other cells. Neuron communication is under intense investigation by researchers because when it goes out of balance ailments ranging from epilepsy to memory disorders can occur. Neural Plasticity Essential discovery to understand how memories can be formed as a result of transduction. It is now believed that learning depends on neural plasticity – the capacity for neurons to change the way they function as a result of experience. This was demonstrated by Eric Kandel in the 60s In a series of landmark studies on a sea slug, Aplysia. It has 20,000 central nervous system cells so big they can be seen without a microscope, yet the animal is capable of simple learning. In trials, the animal is first touched lighly and then shocked at the tail. At first, the touch is not enough to elicit a response, but after enough parings, it is. So the animal has developed, or learned a new conditioned response. What was observed was that the pairings caused the neurons to increase the amount of neurotransmitter each time they fired . So, at the end of the learning, these neurons are able to trigger the response of gill contraction (initially only done by the shock) all by themselves! Another kind of Plasticity is called Long Term potentiation – b/c the mechanism involves increase in neuron’s potential for firing, and long term b/c this potentiation lasts for days. Schematically, If neuron A fires over and over, neuron C becomes more responsive to it, but C is also attached to neuron B. If neuron B tends to fire at the same time as A, then C will become more sensitive to it too, spreading potentiation to both A and B, thus in effect we have an association at the molecular level. As you can guess this has many implications for memory drug design as well. LPT is regarded as the most plausible mechanism for the neural basis of memory. This is because it’s main effect is to increase the sensitivity of the post-synaptic neuron from repeated stimulation, in effect making it “remember” the incoming signal. This is simply summarized by: “the brain secures learned information by implementing a series of molecular interactions. ”  Now, to remember a list of facts to pass a test, for instance, or even recalling information like your phone number, relies on the formation of "long-term" memories. “How are these formed”? This has been an ongoing area of study, in which there was only recently a major breakthrough.
  • The “standard Model” from psychology defining the steps by which something learned can get into long term memory. Current research is focused on the molecular basis of each of these mechanisms. -1950s – “scientists got their first serious clue to how and where memories are formed. A 27-year-old patient, known H.M., had severe epilepsy. In an attempt to cure it, surgeons in 1953 removed his hippocampus , a small ridge in the center of the brain. His seizures went away and his reasoning capacity was intact , but he could no longer recall any new facts for longer than a few seconds. “ however, H.M. could still remember his childhood. That naturally implied that the hippocampus was crucial for converting immediate perceptions into memories, but the fact that he still had old memories meant that it wasn't the storage site for memory , although it could play a role in forming new memories. Working memory , enables you to retain what someone has said just long enough to reply. This activity occurs in the prefrontal area. Researchers recently discovered that certain neurons in the prefrontal cortex that are influenced by other neurons releasing dopamine and glutamate undergo potentiation, lasting for a few minutes. This signifies a memory in its “sensory" phase. But this “fresh information” is evicted and forgotten unless essential molecules and genes are activated. So, at the same time, neuron cells receive signals that induce reactions involving a molecule, protein kinase A, which in turn, sets off another molecule in the cell known as cyclic AMP-response element binding protein (CREB), That activates a gene in the cell that codes for the production of the proteins that ultimately change the structure and activity of nerve cells, thus forming a memory which fastens information for days, weeks or longer. That memory is now in Working memory. While at least some of the chemical reactions needed to convert a short-term memory into a long-term memory appear to be the same, the memory processing occurs in different brain areas. “ Explicit memories require the brain regions within the temporal lobe of the cerebral cortex including the hippocampus. “ “ Implicit memories are primed in the specific sensory and motor systems that are recruited for whatever the particular task is that’s being remembered.” But still we don’t understand how/where the really long term memories are formed or “kept”.
  • -University Of Toronto Date: 07 May 2004 : Journal: Science. Scientists Uncover How Brain Retrieves And Stores Older Memories "It was previously known that the hippocampus processes recent memory, but that the hippocampus did not store memories permanently. We were able to determine that it is the anterior cingulate cortex where older, or lifelong, memories are stored and recalled ," said Dr. Paul Frankland, the study's co-lead author, a scientist in the Sick Kids Research Institute, and assistant professor of physiology at the University of Toronto. The researchers used a series of strategies with mice, including a mouse model with an altered form of a gene called CaMkinase II, which eliminates the ability to recall old memories, to identify the role of the anterior cingulate cortex. Summary: The formation of new memories is involves the strengthening of synaptic connections between groups of neurons. Remembering involves the reactivation of the same group, or network, of neurons. As memories age, the networks change. Initially, memories for everyday life events appear to depend on networks in the region of the hippocampus. However, over time, these memories become increasingly dependent upon networks in the region of the brain called the cortex. "We believe there is active interaction between the hippocampus and cortex, and that the transfer process of memories between these two regions in the brain occurs over several weeks, and likely during sleep," added Dr. Frankland, holder of the Canada Research Chair in Cognitive Neurobiology. "Most people define memory as their collective lifetime experiences. These memories colour who we are, yet until now, we've been mystified by how the brain saves and retrieves them, Now that we know where to look, we're one step closer to developing drugs to target genes or processes of the brain that may be related to memory disorders." said Dr. Alcino Sliva, the study's principal investigator and professor of neurobiology, psychiatry and psychology at the David Geffen School of Medicine at UCLA.
  • The "Mozart Effect" Study At the University of California, Irvine, Shaw (a particle physicist and researcher at the Center for the Neurobiology of Learning and Memory) and his colleague, Rauscher (currently an assistant professor at the University of Wisconsin - Oshkosh in cognitive psychology), gave a group of college students three sets of standard IQ spatial reasoning tasks. Each of these tasks was preceded by one of three ten-minute-long 'listening' conditions. One involved listening to a Mozart sonata for two pianos; another entailed listening to a relaxation tape; and the last consisted of sitting through ten minutes of silence. The results demonstrated that listening to Mozart gave individuals a distinct advantage in terms of spatial task performance. As Shaw noted in a 1993 Nature article, students performed better "on the abstract/spatial reasoning tests after listening to Mozart than after listening to either the relaxation tape or to nothing...." Although the music condition significantly differed from the silence and the relaxation conditions, Shaw and his colleague were careful to qualify the study's results. Listening to Mozart's piano sonata in D major (K488) did, in fact, raise spatial reasoning test scores, but the effects were short-lived. Shaw made this temporary characteristic of the Mozart effect clear: "The enhancing effect of the music condition is temporal, and does not extend beyond the 10-15 minute period during which subjects were engaged in each spatial task.“
  • Left: ANY report of gender differences causes reporters to snap to attention!  “ they cover science of dubious value (not quite certain that the reported study tells us about ANYTHING since there are endless interpretations that could explain the finding as covered by the press); they report a finding out of context (this is hardly the first study looking at gender differences and aspects of language processing), and they extrapolate WILDLY from the findings (surely the researchers can not be saying that this study indicates that women listen better than men?). “ difficulty of interpreting fMRI results and why the media should avoid reporting on these kinds of findings. Brain-Based Learning dubious interpretations of neuroscience, and their educational application is wholly untested . Claim: educators need to throw out curriculum, textbooks, worksheets, and separate disciplines on the grounds that such curricular structure is inconsistent with our knowledge of how the brain works. Present no evidence as to what happens with student achievement when such changes are implemented. -claim: that neuroscience has demonstrated "brain plasticity" or an ability to adapt to new conditions throughout the life span. The notion of brain plasticity appeals to educators because it agrees with the popular educational concept of lifelong learning. Two problems: authors use the concept differently from its use in neuroscience, Second, neuroscientists have shown that true brain plasticity is greatest in young children, less in adolescence, and still less in adulthood (Pascual-Castroviejo, 1996), but they interpret and redefine neuroscience terms to suit their pedagogic purposes. A third example of neuroscience interpreted in service of educational theory is Edelman's (1987) concept of "neural Darwinism." Edelman's view is founded on two analogies: that the brain can be thought of as a multilayered jungle and that it grows, changes, and adapts in much the same way as the immune system. Although Edelman's theory is only now undergoing study by neuroscientists, educational implications of neural Darwinism have been given cover-story treatment in widely circulated education periodicals. For example, in a 1994 Educational Leadership article, Sylwester asserts "Edelman's model suggests that a jungle-like brain might thrive best in a jungle-like classroom that includes many sensory, cultural, and problem layers that are closely related to the real-world environment" (1994, p. 50). Such a view fits nicely with Sylwester's apparent preference for unstructured, discovery-oriented pedagogy. What Sylwester fails to mention is that his interpretation is unsupported and his recommendation for classroom practice is in disagreement with a substantial body of evidence supporting the educational value of a well-ordered classroom.
  • -(Forbes 2002) Inside a small lab in an anonymous office park off the Garden State Parkway in northern New Jersey, researchers probe the molecular intricacies of memory. Tiny metal electrodes zap minute jolts of electricity at precise intervals into slices of rat brain suspended in nutrient broth in plastic lab dishes. This simulates the electrochemical changes that occur in brain cells when a new memory is created. A robotic pump drips experimental drugs through plastic tubes onto the brain cells, while other electrodes measure how each drug alters their activity. Six such setups chart the mind-altering effects of dozens of compounds a month. Most have little effect, but a few drugs fit a cherished profile: helping the disembodied neurons form stronger, longer-lasting connections. Memory Pharmaceuticals, the closely held biotech firm doing this work(, is at the forefront of an intense scientific race to devise the first effective memory-enhancing drug. The idea has long been the stuff of science fiction, but now researchers are decoding the molecular details of how memories are formed and how they are lost. They have taken a crucial first step: identifying the genes and proteins inside brain cells that regulate memory formation. They are tantalizingly close to creating a kind of Viagra for the brain: -Curing Age-Related Diseases: an understanding of how the brain learn and remembers is crucial to finding treatment e.g. Except for extreme cases like advanced Alzheimer's, memory disorders do not generally disrupt procedural memory, the ability to perform basic tasks or motor skills like riding a bicycle or getting dressed. Far more vulnerable is episodic memory, the ability to recall specific information about people, dates and events. Many of the new compounds being scrutinized seek to improve the way recent memories are stored, transformed into long-term memories and brought back into consciousness when needed. question of how function can be restored after brain or spinal cord injury is the subject of intense research and great public interest. The key lies in understanding nerve cell "memory"-- the vital connections that are formed during nervous system development and modified by experience.

Neuroscience Neuroscience Presentation Transcript

  • Why would anyone want to be a neuroscientist?
  • The scientific study of the nervous system and its relationship to cognition and behaviour. Cognitive Neuroscience Neuro- pathology Neuro- physiology Neuro- endocrinology Neuro- psycho- pharmacology Neuroanatomy Neuroimagery Molecular neurobiology Neuro- psychology Neurosciences
  • Nervous System Central Peripheral + Cranial nerves Brain Somatic (intrinsic sensing) Spinal Cord Autonomic (extrinsic sensing)
  • Associative Learning Mechanisms
    • Classical Conditioning
        • Discovered by Ivan Pavlov (1920s)
        • Passive learning
    • Operant Conditioning
        • Discovered by B.F. Skinner (1960s)
        • Active learning
  • Types of Memory Explicit ( conscious) Implicit ( unconscious) Generic Episodic Procedural Dispositional
  • How is the Brain studied?
    • Case Studies
    • Gene Splicing
    • Imaging
      • PET
      • EEG ( electrical current detection )
    • Transcranial Magnetic Stimulation ( causes temporary disruption of a brain region )
      • MRI
      • fMRI
      • CAT
  • How is learning and memory enabled?
    • Signal Transduction:
      • Inter-Neuron communication occurs via Neurotransmitters at the synaptic gap
    • Neural Plasticity:
      • Through experience, Neurons can change the way they function
    • Long Term Potentiation:
      • Cellular mechanism through which associations can be detected and recorded in the brain
  • Sensory Memory Working Memory LTM Sensory Input Indefinite duration Retrieval Stage Theory of Memory Attention Encoding Maintenance Rehearsal
  • The Latest Breakthrough
    • 07 May 2004, Science
      • Scientists Uncover How Brain Retrieves and Stores Older Memories
  • The “Mozart Effect” and other tragedies in science reporting
    • Mozart Effect:
    • Actual Conclusion
      • “ "there are correlational, historical, and anecdotal relationships between music cognition and cognitions pertaining to abstract operations such as mathematical or spatial reasoning,"
      • Media’s Conclusion
      • - “listening to Mozart can make one smarter”
    • Estrogen Aides Brain Activity, Tests Find
      • Brain in the News, April 16, 1999 (vol. 6, No.7)
    • Deep in the story one finds this telling paragraph," Because of the way the imaging test was designed, the women did not show any noticeable difference in their conscious ability to recall the words, only at the more subtle level of cellular function. The researchers believe, however, that the brain activity does reflect improved memory." !!!!
  • “ If only we could scan the brains of science writers when they are writing this kind of nonsense and compare it to the brain scans of neuroscientists when they have to read it! Now that might make an interesting story!”
    • WOMEN USE MORE OF BRAIN WHEN LISTENING, STUDY SAYS (LA Times, November 29, 2000)
      • Study not published
      • Showed differing patterns of brain images acquired from men and women listening to a reading of a John Grisham novel
    • FADS:
      • Brain-Based Learning
        • Distorted neuroscience research to support a particular educational philosophy.
  • To what, or to whom, is actual neuroscience research on memory and learning applicable?