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NATS 1860 Final Exam Note.docx

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York University
Natural Science
NATS 1860
Keith Schneider

NATS 1860 Winter Term (2013) Final Exam Questions The exam will consist of four questions, one drawn from each of the following four sets (A through D). You will write your answers in exam booklets that will be provided to you without using any information stored outside your own neurons during the exam. Set A 1.Draw a diagram that compares the temporal and spatial resolution limits of the functional MRI technique to the EEG technique. Make sure to label the axes of the graph. Describe in words the different brain structures and types of information that can be measured by each technique. The difference between fMRI and EEG is as follows: EEG monitors the neurons that fire action potential through an electrochemical activity. EEG specifically monitors the brain activity on the top of the brain due to the electrodes being laid over a person’s head. EEG allows the collection of specific action potentials in the form of electrochemical activity data. It has a poor spatial resolution because it only offers the top-of-the-brain activity, however has very good temporal awareness allowing for the millisecond and second observation of change in the brain. The fMRI practice, on the other hand, allows for the examination of more specific spatial resolution such as region maps and neuron columns of neuron layers. It specifically reflects the flow of oxygen-rich blood traveling to hot spots that are doing greater work. However, despite its spatial advantage, fMRI has a slower temporal resolution ranging from seconds to hours. 2.Briefly explain each of the following imaging techniques, including which signals are being measured from the brain, and describe one strength and one weakness for each. a. fMRI – this is the head-gear that monitors specific flow of oxygen-rich blood flowing around in the brain. This monitoring allows for the measurement of blood in response to the amount of required activity for a specific task. An advantage of fMRI is that it is a good combination of temporal and spatial resolution, as well as a non- invasive method of gathering data on brain activity. One disadvantage would be that it is an indirect inference of neural activity through secondary blood flow, as well as there being a potential for better spatial and temporal resolutions in comparison to other forms of neuroimaging. b. PET – This is the process of injecting an individual with a radioactive substance and then monitoring how that substance is attached and spread through molecules. PET works by using gamma rays emitted by the radioactive tracer isotope that is attached to the molecules (such as glucose in blood). PET is used to specifically detect which regions (maps and columns) are activated over a long period of time (can be from hours to days). For example, if you’re seeing words your visual cortex is active, when you’re hearing words your auditory cortex is active, etc. An advantage of PET is that it can trace different substances and see which sections of the brain are activated based on the specific function. A disadvantage is that the radioactive substance is incredibly invasive and can only be injected once a year to prevent poisoning. It also has worse spatial and temporal resolution than MRI and requires a PET scanner to be nearby in order to proceed with the examination. c. EEG – This is the procedure of attaching electrodes to people’s scalps in order to measure a small, but detectable electric field. This form of neuroimaging specifically monitors the electrochemical activity in the brain (disturbances in the electrical field). This electrochemical activity is the way that the brain communicates with itself (through electrical waves). It specifically targets the ions present in the electrochemical activity. Its advantages include the fact that it has very good temporal resolution, however has very limited spatial resolution, causing it to be difficult to accurately localize the source of the measured signal. d. MEG – This is very similar to EEG, except instead of using electrodes attached to the scalp, this uses a big machine that uses a magnetic field. MEG also targets specific electrochemical activity and tracks ionic movement in the brain. An advantage of MEG includes its very good temporal resolution, as well as an improved setup time and subject comfort compared to EEG, as well as less degradation of the signal due to the magnet going past the scalp. A disadvantage of MEG is the limited spatial resolution e. Single unit electrophysiology – this is the procedure in which a machine is used to directly record action potentials and other electrical activity from specific areas in the brain. It’s specifically used to measure parts of our brain that can be affected by seizures, and allows neurosurgeons to cut out the parts where the epilepsy has influences on the brain. An advantage of this includes the fact that it has very high spatial and temporal resolution, allowing scientists to directly measure action potentials and local electrical fields. It also allows the recording of activity of multiple individual neurons that can be directly compared. A set of disadvantages includes the fact that the records are only from a relatively small number of neurons, as opposed to a greater amount, as well as the fact that electrophysiology is very invasive because it requires cutting out certain parts of the brain. f. Optical imaging – this is the procedure in which the top of the skull is cut open, and it allows the optical observation of the brain surface. This method can either measure intrinsic activity such as blood flow, or electrical activity by injecting a voltage-sensitive dye. One advantage of this method is that it has very precise temporal and spatial resolution. A disadvantage, however, is the fact that it is incredibly intrusive (where you have to physically open the skull), as well as confining the observations only to the surface of the brain. Also making it difficult to analyze a subject’s cortex since it is hidden. g. NIRS (Near Infrared Spectroscopy) – This is a procedure in which you shine an infrared light through the persons skull. It allows scientists to measure the specific changes in the absorption of information due to blood flow. One example of what it specifically measures is the In NIRS you have a transmitter and a detector. One advantage of NIRS is that it offers good temporal resolution, as well as it being non- invasive, safe (in the sense that it doesn’t require any extremely radioactive waves), and is good for usage on infants. The disadvantage of NIRS is that it has very limited spatial awareness and does not work on every subject – for example, darker skin and hair prevents light from being transmitted. h. TMS – This is the process of using a strong magnetic pulse over a specific surface area on the head to determine the functions of those areas. It induces an electrical current flow on the surface of the brain by briefly introducing noise and disrupting brain activity in a localized area. Advantages of this method include the fact that it has very good temporal resolution, as well as the fact that it allows for the manipulation of neuronal activity and allows for causal inference. Disadvantages include the poor spatial resolution due to it being limited to the surface of the brain; it’s lack of comfort, and the fact that repetitive TMS procedures can cause seizures in patients if applied improperly. Set B 3.Compare and contrast the human brain and a digital computer, including memory capacity, processing speed, and the capabilities of understanding, and being intelligent or conscious. Describe one ability that a digital computer excels at but the brain does not, and vice versa. Humans have roughly 100 Terabytes of memory in terms of computational power v. memory capacity. Humans are able to perceive, understand, and be conscious of events and information about them due to the complexity of their brains. According to Moore’s law, computers keep evolving and duplicating their memory capacity and processing speed every two years, meaning that after a certain point in time, the computers processing speed and memory storage will be much more significant than that of the human brain. However, computers act like data-output machines in the sense that they are only intelligence insofar as they are programmed with the information. Therefore, since computers are unable to create or write their own code and information it can be said that computers are not actually conscious beings, and are thus inferior to the human brain. One advantage, therefore that computers have over the human brain is that they will eventually obtain greater processing speech and memory storage than us. However, due to their inability to have “free will” in the sense that they cannot write their own instructions, they will never be more superior to the human brain. Therefore, the specific human brain ability that excels over computers is the ability to create own information. 4.During your travels, you encounter an alien species. Describe in detail how you would determine if this species were a) conscious and b) intelligent. This is an opinion-based question. There are many different ways approaching the question of consciousness and intelligence such as its processing speed, learning capacity, reflex, and instinct. One specific method that neuroscience defines consciousness is the ability to discriminate, categorize, and react to environmental stimuli. At the same time, that ability does not necessarily mean that the being is conscious. Nevertheless, I would approach this species with a young toddler. If this species is conscious, it will recognize the fact that the toddler is a living being, and would not harm it but would react to the toddler’s babbling and lack of directed motion as non- threatening. However, if the species were to inflict any physical harm to the baby or throw it on the ground, it can be assumed that this species lacks the ability to recognize and discriminate the fact that this is a living, non- threatening being. At the same time, however, in the event that this species choses to eat the baby, then it would be quite hard to determine whether or not it is conscious because on one side of the field the species is incapable of discriminating that eating babies is immoral and is not able to categorize what can be eaten and what can not. At the same time, you can say that by recognizing the baby as an inferior creature who is made up of flesh (and assuming that this species would not be accustomed to our sense of morality), it would be quite logical and conscious of the species to consider the baby as a “snack” or appetizer. Intelligence, on the other hand, is easier to determine for this species. Intelligence, being the ability to make inferences based on previously submitted information, can be measured by providing the alien species with the basic block-and-hole toy. If the aliens can successfully discriminate against three forms of shapes (circles, triangles, and squares for example), and correctly categorize the proper shapes into the proper wholes, then you could say that this species has the bare minimum level of intelligence. 5.Provide a definition for consciousness. What sorts of objects and animals are or could be conscious? Why do you think so? Defend your answer. One definition of consciousness is the awareness of environmental and cognitive events such as the sights and sounds of the world as well as of one’s memories, thoughts and bodily sensations. Another definition encompasses the ability to discriminate, categorize, and react to environmental stimuli. Theoretically, animal
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