yt:channel:UCUgZq9PkDp1xaEivtcfJPSg UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2014-05-16T03:06:47+00:00 yt:video:bX0_AB9Sqt8 bX0_AB9Sqt8 UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-06-21T10:18:11+00:00 2017-07-29T19:47:01+00:00 2 Minute Neuroscience: Serotonin In this video, I discuss the neurotransmitter serotonin. I cover serotonin synthesis, the primary location of serotonin-producing neurons, serotonin receptors, and functions of serotonin. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss serotonin. Serotonin is a monoamine neurotransmitter, a term that refers to its chemical structure and the fact that it is derived from an amino acid. To synthesize serotonin, the amino acid tryptophan is converted to 5-hydroxytryptophan, or 5-HTP, and 5-HTP is converted to serotonin, or 5-HT. Serotonin neurons are primarily found in the brainstem in clusters of neurons called the raphe nuclei. Serotonin neurons from the raphe nuclei project throughout the brainstem and brain, and provide serotonin to the rest of the central nervous system. Researchers have identified 7 different families of serotonin receptors, which differ from one another in distribution, the substances that bind to them, and the effects they mediate. All but one of these families of receptors consists of G-protein coupled receptors, the other receptor family consists of ligand-gated ion channels. Within these 7 families of receptors, 14 receptor subtypes have been identified as well. Serotonin is removed from the synaptic cleft by a transport protein called the serotonin transporter, or SERT. In terms of function, serotonin is often linked to mood in part due to the understanding that many antidepressants cause serotonin levels to rise. However, an attempt to define any neurotransmitter by one function is inevitably an oversimplification. In truth, serotonin’s role in mood is very unclear and depression is not likely to be due to a simple serotonin deficiency. Additionally, serotonin is involved in a long list of functions other than mood. In most cases its actual role in those functions is still not completely understood. Reference: Nichols DE, Nichols CD. Serotonin Receptors. Chem Rev. 2008, 108: 1614-1641. yt:video:TXwp1rg3jck TXwp1rg3jck UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-05-22T09:26:30+00:00 2017-07-29T19:16:27+00:00 2-Minute Neuroscience: Neurotransmitter Release In this video, I describe the mechanisms underlying neurotransmitter release. I discuss how calcium influx is thought to play a role in mobilizing and preparing synaptic vesicles for neurotransmitter release, and I cover the hypothesized mechanism by which vesicles fuse with the cell membrane of the neuron to empty their contents into the synaptic cleft. TRANSCRIPT: Neurotransmitters are stored in the axon terminals of a neuron in small sac-like structures called synaptic vesicles. When an action potential travels down the neuron and reaches the axon terminal, it causes depolarization of the neuron. This change in membrane potential causes voltage-gated ion channels, which are ion channels that open in response to changes in membrane potential, to open and allow calcium to enter the cell. Calcium seems to be involved with mobilizing vesicles to prepare them for neurotransmitter release. One way this occurs is through an interaction between calcium and a protein called synapsin, which attaches vesicles to the cytoskeleton of the cell. Calcium activates an enzyme that causes synapsin to separate from the vesicles, mobilizing them for release. After mobilization, a family of proteins called SNARE proteins are involved with getting the vesicle ready to fuse with the cell membrane of the neuron. Synaptobrevin (also called VAMP) is a SNARE protein found in the membrane of vesicles, while syntaxin and SNAP-25 are two SNARE proteins found in the cell membrane. These three proteins are thought to form a complex, which helps to bring vesicles in contact with the cell membrane, allowing the two membranes to fuse together. This process is thought to be facilitated by another protein called munc18. The role of munc18 in vesicle fusion is not completely understood, but it seems to bind to syntaxin and be necessary for fusion to occur. Another protein found in synaptic vesicles known as synaptotagmin is thought to act as a calcium sensor, which aims to promote vesicle fusion only when calcium levels in the cell are high. When the vesicle fuses with the cell membrane, it empties its contents into the synaptic cleft. After neurotransmitter release, the SNARE complex is disassembled with the help of proteins called NSF and SNAP, and the vesicle is recycled so it can be used again. References: Südhof TC. A molecular machine for neurotransmitter release: synaptotagmin and beyond. Nat Med. 2013 Oct;19(10):1227-31. doi: 10.1038/nm.3338. Südhof TC, Rothman JE. Membrane fusion: grappling with SNARE and SM proteins. Science. 2009 Jan 23;323(5913):474-7. doi: 10.1126/science.1161748. yt:video:4d4zwhl3nO8 4d4zwhl3nO8 UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-04-11T10:20:01+00:00 2017-07-25T22:37:41+00:00 2-Minute Neuroscience: Long-Term Potentiation (LTP) Long-term potentiation, or LTP, is a process by which connections between neurons become stronger with frequent activation. LTP is thought to be a way in which the brain changes in response to experience, and thus may be an mechanism underlying learning and memory. In this video, I discuss one type of LTP: NMDA-receptor dependent LTP. I outline the mechanism underlying NMDA-receptor LTP and describe how it is thought to strengthen synaptic connections where it occurs. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss long-term potentiation, or LTP. LTP is a process by which synaptic connections between neurons become stronger with frequent activation. LTP is thought to be a way in which the brain changes in response to experience, and thus may be an mechanism underlying learning and memory. There are a number of ways in which LTP can occur. The best-known mechanism involves a glutamate receptor known as the NMDA receptor. In NMDA-receptor dependent LTP, glutamate release first activates a subtype of glutamate receptor known as the AMPA receptor. NMDA receptors are found nearby these AMPA receptors, but are not activated by low levels of glutamate release because the ion channel of an NMDA receptor is blocked by a magnesium ion. If frequent action potentials cause greater stimulation of AMPA receptors, however, this will cause the postsynaptic neuron to depolarize, which eventually causes the voltage-dependent magnesium blockage of the NMDA receptor to be removed, allowing calcium ions to flow in through the NMDA receptor. This influx of calcium initiates cellular mechanisms that cause more AMPA receptors to be inserted into the neuron’s membrane. The new AMPA receptors are also more responsive to glutamate, and allow more positively charged ions to enter the cell when activated. Now, the postsynaptic cell is more sensitive to glutamate because it has more receptors to respond to it. Additionally, there are thought to be signals that travel back across the synapse to stimulate greater levels of glutamate release. All of this makes the synapse stronger and more likely to be activated in the future. This process is also associated with changes in gene transcription in the neuron, which can lead to the production of new receptors or modifications to the structure of the cell. These changes seem to be important for making the increased responsiveness of LTP long-lasting. yt:video:kOnk9Hh20eg kOnk9Hh20eg UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-03-14T09:41:07+00:00 2017-07-21T11:01:29+00:00 2-Minute Neuroscience: Amyotrophic Lateral Sclerosis (ALS) Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative disorder characterized by a progressive loss of motor function. ALS affects upper motor neurons and lower motor neurons. As these motor neurons stop working, muscles also begin to atrophy; this can eventually lead to respiratory failure, which is often the cause of death in ALS patients. The pathophysiology of ALS is not completely understood, but similar to other neurodegenerative diseases like Alzheimer's disease it is characterized by clusters of dysfunctional proteins within neurons. In this video, I discuss ALS symptoms and pathophysiology. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss amyotrophic lateral sclerosis, or ALS. Also known as Lou Gehrig’s disease in the US and motor neuron disease in the UK, ALS is characterized both by muscle spasticity and a progressive weakening of the muscles. As the disease progresses, patients may lose hand and arm function, and experience difficulty walking, speaking, and even breathing. Respiratory failure is often the cause of death, and the average survival time from diagnosis is around 3-5 years. Although some cases of ALS are inherited, in the vast majority of cases the cause of ALS is unknown. ALS is a neurodegenerative disorder, meaning it is characterized by the degeneration and death of neurons. Specifically, the affected neurons in ALS are called upper and lower motor neurons. Upper motor neurons extend from the cerebral cortex or brainstem and carry motor information down to the spinal cord. Lower motor neurons extend from the spinal cord or brainstem to skeletal muscle to cause movement. Degeneration of upper motor neurons often is responsible for spasticity and modest weakness, but degeneration of lower motor neurons causes more disabling weakness. As the motor neurons stop working, muscles also begin to atrophy. Mutations in several genes have been linked to the development of ALS, but the effects of the mutations are not completely clear and the mechanism that causes neurodegeneration in ALS is still not understood. Similar to other neurodegenerative diseases like Alzheimer’s disease, ALS is characterized by the accumulation of dysfunctional proteins within neurons. Although the impact of these protein groups or aggregates is unclear, it is hypothesized that they could impair neuronal function. There also are a number of other mechanisms proposed to play a role in neurodegeneration in ALS and it is likely more than one is involved. References: Morgan S, Orrell RW. Pathogenesis of amyotrophic lateral sclerosis. Br Med Bull. 2016 Sep;119(1):87-98. doi: 10.1093/bmb/ldw026. Rothstein JD. Current hypotheses for the underlying biology of amyotrophic lateral sclerosis. Ann Neurol. 2009 Jan;65 Suppl 1:S3-9. doi: 10.1002/ana.21543. yt:video:QL51iPCovXo QL51iPCovXo UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-02-09T10:47:09+00:00 2017-07-29T19:46:51+00:00 2-Minute Neuroscience: Dopamine Dopamine is a monoamine and catecholamine neurotransmitter with many functions in the nervous system ranging from movement to lactation. In this video, I discuss dopamine synthesis, areas of the brain where dopamine neurons are concentrated, dopamine pathways, dopamine receptors, and dopamine functions. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss dopamine. Dopamine is a monoamine neurotransmitter, a term that refers to its chemical structure and the fact that it is derived from an amino acid. Dopamine is also a catecholamine, a term that also refers to its chemical structure and the fact that it contains a catechol nucleus. To synthesize dopamine, the amino acid tyrosine is converted to L-dopa. Then L-DOPA is decarboxylated to form dopamine. There are several areas of the brain where dopamine neurons are concentrated. The largest are the substantia nigra and ventral tegmental area in the midbrain. Other areas include the hypothalamus, olfactory bulb, and retina. There are several major dopamine pathways that carry dopamine from these areas of concentration to other parts of the brain. Some of the largest are the mesostriatal or nigrostriatal pathway, which stretches from the substantia nigra to the striatum, the mesolimbic pathway, which stretches from the ventral tegmental area to the nucleus accumbens and other limbic structures, and the mesocortical pathway, which stretches from the ventral tegmental area throughout the cerebral cortex. Dopamine acts at G-protein coupled receptors and there are at least 5 subtypes of the dopamine receptor. Dopamine is removed from the synaptic cleft by a transporter protein called the dopamine transporter. Like any neurotransmitter, the functions of dopamine are complex, and can’t be fully explained with just a short summary. Dopamine is linked to movement due to disorders like Parkinson’s disease that involve dopamine deficiencies. It is also often associated with the processing of rewarding experiences. However, dopamine also plays a role in many other functions. yt:video:R0VPDd0JwCE R0VPDd0JwCE UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2017-01-22T10:41:21+00:00 2017-07-30T00:56:58+00:00 2-Minute Neuroscience: Pineal Gland The pineal gland is a pine cone shaped structure located in the diencephalon whose main function is the secretion of melatonin, a hormone that is best known for its role in regulating circadian rhythms. The pineal gland secretes melatonin throughout the 24-hour cycle, with secretion being highest in the middle of the night and lowest during daylight hours. In this video, I discuss the pineal gland and melatonin secretion, including 24-hour patterns of melatonin secretion and how the pineal gland uses signals from the retina about how much light is in the environment to determine what the time of day is. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the pineal gland. The pineal gland was given its name because it has a pine-cone like shape. Unliked most brain structures, the pineal gland is unpaired, meaning there is only one. It sits directly on the midline of the brain. The function most linked to the pineal gland is the secretion of a hormone called melatonin, which is best known for its role in regulating circadian rhythms. The pineal gland is made up of secretory cells called pinealocytes, which secrete melatonin throughout the 24-hour cycle. Secretion is highest in the middle of the night. It begins to decrease as it gets closer to dawn and is lowest during daylight hours. This schedule of melatonin secretion is regulated by signals from the retina about light in the environment, which travel to a nucleus in the hypothalamus called the suprachiasmatic nucleus and then via an indirect route to the pineal gland. The main function of the suprachiasmatic nucleus is to control circadian rhythms, and in addition to sending information about ambient lighting to the pineal gland, the suprachiasmatic nucleus also uses levels of melatonin as a signal to provide information about the time of day. Because melatonin levels are highest during the hours of darkness, melatonin activity can be used as a signal that circadian rhythms should be in their nocturnal stage. If melatonin levels are high and someone is still wide awake, it is an indication circadian rhythms are not in sync. This might happen, for example, after flying across several time zones. In this case, melatonin is used by the suprachiasmatic nucleus as a signal to get circadian rhythms back on track. Due to its close association with nighttime and circadian rhythms, melatonin has also been investigated as playing a role in promoting sleep, but the true relationship between melatonin and sleep is still unclear. References: Dora Sapède,, & Elise Cau (2013). The Pineal Gland from Development to Function Current Topics in Developmental Biology DOI: 10.1016/B978-0-12-416021-7.00005-5 yt:video:8hDoO0wcq8Q 8hDoO0wcq8Q UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-11-29T10:54:47+00:00 2017-07-29T19:11:23+00:00 2-Minute Neuroscience: Primary Somatosensory Cortex In this video, I discuss the primary somatosensory cortex. The primary somatosensory cortex is responsible for processing somatic sensations, or sensations from the body that include touch, proprioception (i.e. the position of the body in space), nociception (i.e. pain), and temperature. The primary somatosensory cortex is generally divided into 4 areas: area 3a, 3b, 1, and 2. In the video, I discuss the relative functions of each of these areas. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the primary somatosensory cortex. The primary somatosensory cortex is located in a ridge of cortex called the postcentral gyrus. It is situated just posterior to the central sulcus, a prominent fissure that runs down the side of the cerebral cortex. The primary somatosensory cortex is responsible for processing somatic sensations, or sensations from the body that include touch, proprioception or the position of the body in space, nociception or pain, and temperature. When receptors detect one of these sensations, the information is sent to the thalamus and then to the primary somatosensory cortex. The primary somatosensory cortex is typically divided into 4 areas: area 3a, 3b, 1, and 2. Area 3 receives the majority of somatosensory input directly from the thalamus, and the initial processing of information occurs here. Area 3b is primarily concerned with basic processing of touch sensations, while area 3a responds to information from proprioceptors. Area 3b is densely connected to areas 1 and 2, and when area 3b receives touch information, that information is then sent to areas 1 and 2 for more complex processing. Area 2 is also involved with proprioception. Each of the four areas of the primary somatosensory cortex is arranged such that a particular location in that area receives information from a particular part of the body. This arrangement is referred to as somatotopic, and the full body is represented in this way in each of the four regions of the somatosensory cortex. More sensitive areas of the body take up a disproportionate amount of space in this somatotopic arrangement. References: Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, White LE. Neuroscience. 4th ed. Sunderland, MA. Sinauer Associates; 2008. yt:video:DHpCBmq_z60 DHpCBmq_z60 UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-11-05T10:37:20+00:00 2017-07-28T18:38:22+00:00 2-Minute Neuroscience: Suprachiasmatic Nucleus The suprachiasmatic nuclei (SCN) are thought to be involved with maintaining circadian rhythms, or biological patterns that follow a 24-hour cycle. To accomplish this, the cells of the SCN contain biological clocks. In this video, I discuss the molecular mechanism driving the biological clocks in the cells of the mammalian SCN, and how a cycle of gene expression allows the activity of these cells to follow a 24-hour pattern. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the suprachiasmatic nucleus. The suprachiasmatic nuclei, or SCN, are two small, paired nuclei found in the hypothalamus; they are involved in maintaining circadian rhythms, or biological patterns that follow a 24-hour cycle. To accomplish this, the cells of the SCN contain biological clocks. The following is a simplified description of the molecular mechanism of the biological clocks in the mammalian SCN. Cells in the SCN produce two proteins called Clock and BMAL1. Clock and BMAL1 bind together and promote the expression of genes called period, or per, and cryptochrome, or cry. The protein products of these genes, Per and Cry, then bind together and inhibit the actions of Clock and BMAL1, which in turn suppresses the production of Per and Cry. Gradually, however, the Per and Cry proteins break down. When Per and Cry degrade fully, Clock and BMAL1 are free to act again; they go back to promoting the expression of per and cry, starting the cycle anew. The process consistently takes around 24 hours to complete before it repeats. It is thought that this cycle of gene expression is what acts as the molecular clock in SCN cells, although the process is actually more complex as there are multiple period and cryptochrome genes as well as other proteins involved in the complete mechanism. The SCN can use information it receives from the retina about light in the environment to make adjustments to the circadian clock. Such information travels from the retina to the SCN along a path called the retinohypothalamic tract. References: Colwell, C. (2011). Linking neural activity and molecular oscillations in the SCN Nature Reviews Neuroscience, 12 (10), 553-569 DOI: 10.1038/nrn3086 Dibner, C., Schibler, U., Albrecht, U. (2010). The mammalian circadian timing system: organization and coordination of central and peripheral clocks Annual review of physiology, 72 (1), 517-549. yt:video:3_zgB19TE-M 3_zgB19TE-M UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-10-20T10:18:27+00:00 2017-07-28T03:18:44+00:00 2-Minute Neuroscience: Nucleus Accumbens In this video, I discuss the nucleus accumbens. The nucleus accumbens is located in the basal forebrain, and is the major component of the ventral striatum. Although it is best known as a key structure in the reward system, the role of the nucleus accumbens in reward is still not fully understood. This is due in part to the fact that the nucleus accumbens also seems to be activated in response to aversive stimuli, and thus some have suggested that it is involved in responses to all motivationally-relevant stimuli---whether positive or negative. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the nucleus accumbens. The nucleus accumbens is found in a part of the brain called the basal forebrain, which is located near the front and bottom of the brain. The nucleus accumbens is the major component of the ventral striatum, and is situated between the caudate and putamen. The nucleus accumbens is typically divided into two anatomical components: an outer shell and a central core. There are thought to be functional differences between these two regions, where the shell is more associated with the limbic system and the core is more strongly connected to the motor system. It should be noted, however, that while this distinction between shell and core is clearly seen in rodents, it is less evident in humans. Although the nucleus accumbens is best known as part of the reward system, its functions are much more complex than simple reward processing and are still not fully understood. The nucleus earned its reputation as a key part of the reward system in a large part due to its connections with the ventral tegmental area, or VTA. Dopamine neurons project from the VTA to the nucleus accumbens as part of the mesolimbic dopamine pathway and this pathway is activated in association with rewards. However, the exact role of the nucleus accumbens in processing rewards is not completely clear. It is thought that the nucleus accumbens likely plays a role in learning about rewards and the stimuli that are associated with them. It also seems to be important to stimulating the pursuit of rewards and the selection of actions that are most likely to result in the attainment of a reward, along with the suppression of actions that are less likely to be useful. The nucleus accumbens also appears to be important in processing aversive experiences, however, and in learning to move away from aversive stimuli. Thus, the nucleus accumbens appears to be involved in responses to all motivationally-relevant stimuli, whether rewarding or aversive. References: Floresco SB1. The nucleus accumbens: an interface between cognition, emotion, and action. Annu Rev Psychol. 2015 Jan 3;66:25-52. doi: 10.1146/annurev-psych-010213-115159. Epub 2014 Sep 17. Lucas-Neto L1, Neto D, Oliveira E, Martins H, Mourato B, Correia F, Rainha-Campos A, Gonçalves-Ferreira A. Three dimensional anatomy of the human nucleus accumbens. Acta Neurochir (Wien). 2013 Dec;155(12):2389-98. doi: 10.1007/s00701-013-1820-z. Epub 2013 Aug 3. yt:video:4t1EsfhPBTk 4t1EsfhPBTk UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-10-06T02:13:00+00:00 2017-07-28T03:16:28+00:00 2-Minute Neuroscience: Ventral Tegmental Area (VTA) In this video, I discuss the ventral tegmental area, or VTA. The VTA is one of the two largest dopaminergic regions of the brain (the other being the substantia nigra). Dopamine neurons leave the VTA in several different pathways and project throughout the brain. Two of the most prominent pathways are the mesocortical and mesolimbic pathways. The mesocortical pathway projects from the VTA to widespread areas of the cerebral cortex and has diverse functions including motivation, emotion, and executive functions. The mesolimbic pathway projects from the VTA to several limbic structures; the largest projection is to the nucleus accumbens. The mesolimbic pathway also has diverse functions but is best known for its role in processing rewarding stimuli. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the ventral tegmental area. The ventral tegmental area, or VTA, is found in the midbrain, situated next to the substantia nigra. Although the VTA contains several types of neurons, it is primarily characterized by its large population of dopamine neurons. It is one of the two major dopaminergic areas in the brain (the other being the substantia nigra). VTA dopamine neurons travel from the VTA to other areas of the brain in several major pathways. Two of the most prominent pathways are the mesocortical and the mesolimbic pathways. The mesocortical pathway projects from the VTA to widespread areas of the cerebral cortex, including the prefrontal, orbitofrontal, and cingulate cortices as well as sensory and motor cortices. The mesocortical projections are very diverse and the pathway is involved in a wide range of functions including motivation, emotion, and executive functions. The mesolimbic pathway projects from the VTA to several limbic structures. The largest projection of this pathway is to the nucleus accumbens, but other projections stretch to areas like the amygdala as well. The mesolimbic pathway also has diverse functions, but it is most frequently associated with the reward system, as dopamine signaling along the mesolimbic pathway is considered to be important to the processing of rewarding experiences. When someone uses an addictive drug, for example, dopamine neurons in the VTA are activated. These neurons project to the nucleus accumbens via the mesolimbic pathway, and their activation causes dopamine levels in the nucleus accumbens to rise. The effects of these increased dopamine levels are still not fully understood, but they may be involved with encoding memories about rewarding experiences and attributing importance to environmental stimuli that are associated with the reward. References: Oades RD, Halliday GM. Ventral tegmental (A10) system: neurobiology. 1. Anatomy and connectivity. Brain Res. 1987 May;434(2):117-65. Pierce RC, Kumaresan V. The mesolimbic dopamine system: the final common pathway for the reinforcing effect of drugs of abuse? Neurosci Biobehav Rev. 2006;30(2):215-38. Epub 2005 Aug 11. yt:video:R6XtJOeuhNg R6XtJOeuhNg UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-09-29T01:01:23+00:00 2017-07-30T07:57:21+00:00 2-Minute Neuroscience: Medulla Oblongata In this video, I discuss the medulla oblongata. The medulla is part of the brainstem and is responsible for a number of important functions. It is involved with regulating cardiovascular and respiratory functions as well as a variety of reflexive actions like swallowing, coughing, and vomiting. It is also home to an assortment of important nuclei and cranial nerve nuclei. Finally, a number of tracts like the corticospinal and corticobulbar tracts pass through the medulla on their way from the brainstem to the spinal cord and vice versa. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the medulla oblongata. The medulla oblongata, or the medulla, is the lowest part of the brainstem, found below the pons and above the spinal cord. There is no clear separation between the medulla and the spinal cord; instead the spinal cord gradually transitions into the medulla. Perhaps the most important action linked to the medulla is the regulation of cardiovascular and respiratory functions. The medulla gets information about changes in blood pressure from baroreceptors, which are found inside blood vessels. This information is sent the nucleus of the solitary tract in the medulla, which initiates reflexive actions to return blood pressure to a desired range. The medulla is also responsible for generating breathing movements and for regulating respiration to ensure there is enough oxygen in the blood. To accomplish this, chemoreceptors, which are found inside blood vessels, detect changes in oxygen and carbon dioxide levels in the blood. When oxygen levels fall, neurons in and around the nucleus of the solitary tract and the nucleus ambiguus respond by increasing respiration. The medulla also controls a number of other reflexive actions like swallowing, coughing, sneezing, and vomiting. It is home to the inferior olivary nuclei, which are connected to the cerebellum and involved in movement. It also contains the nucleus gracilis and nucleus cuneatus, important nuclei of the dorsal-columns medial lemniscus sensory pathway. A number of cranial nerve nuclei are also found in the medulla. The medulla contains a number of tracts that pass from the brainstem to the spinal cord and vice versa. The corticospinal tract and corticobulbar tracts, important tracts for movement, form triangular bundles of fibers in the medulla that create ridges on the outside of the brainstem. The bundles and ridges have been termed the medullary pyramids, and because of this the corticospinal and corticobulbar tracts are often referred to as the pyramidal tracts. yt:video:P3aYqxGesqs P3aYqxGesqs UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-09-02T01:10:58+00:00 2017-07-29T21:49:39+00:00 2-Minute Neuroscience: Vestibular System The vestibular system is a sensory system that is essential to normal movement and equilibrium. In this video, I discuss the vestibular labyrinth---the primary structure of the vestibular system, which consists of the semicircular canals, ampullae, and otolith organs. All of these are essential to the vestibular system's ability to provide the brain with information about things like motion, head position, and spatial orientation. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the vestibular system. The vestibular system is a sensory system responsible for providing our brain with information about motion, head position, and spatial orientation; it also is involved with motor functions that allow us to keep our balance, stabilize our head and body during movement, and maintain posture. The main components of the vestibular system are found in the inner ear in a system of compartments called the vestibular labyrinth, which is continuous with the cochlea. The vestibular labyrinth contains the semicircular canals which are three tubes that are each situated in a plane in which the head can rotate. Each of the canals can detect one of the following head movements: nodding up and down, shaking side to side, or tilting left and right. The semicircular canals are filled with a fluid called endolymph. When the head is rotated, it causes the movement of endolymph through the canal that corresponds to the plane of the movement. The endolymph flows into an expansion of the canal called the ampulla, within which there are hair cells, the sensory receptors of the vestibular system. At the top of each hair cell is a collection of small "hairs" called stereocilia. The movement of the endolymph causes movement of these stereocilia, which leads to the the release of neurotransmitters to send information about the plane of movement to the brain. The vestibular system uses two other organs, known as the otolith organs, to detect forward and backward movements and gravitational forces. There are two otolith organs in the vestibular labyrinth: the utricle, which detects movement in the horizontal plane, and the saccule, which detects movement in the vertical plane. Within the utricle and saccule, hair cells detect movement when crystals of calcium carbonate called otoconia shift in response to it, leading to movement in the layers below the otoconia and displacement of hair cells. yt:video:JVvMSwsOXPw JVvMSwsOXPw UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-07-08T15:56:52+00:00 2017-07-30T05:51:54+00:00 2-Minute Neuroscience: Amygdala In this video, I discuss the amygdala. The amygdala is a collection of nuclei found in the temporal lobe; it is best known for its role in fear and threat detection, but its full range of functions is much more diverse. I discuss some of the major nuclei of the amygdala, a common scheme for the anatomical organization of the amygdalar nuclei, and some of the functions that have been associated with the amygdala ranging from threat detection to the processing of positive stimuli. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the amygdala. The amygdala is a collection of nuclei found in the temporal lobe. There are two amygdalae, one in each cerebral hemisphere. The term amygdala means “almond,” referring to one of the most prominent nuclei of the amygdala that has an almond-like shape. The major nuclei of the amygdala include the lateral nucleus, basal nucleus, accessory basal nucleus, central nucleus, medial nucleus, and cortical nucleus. Each of these nuclei can also be partitioned into subnuclei. One common scheme for anatomically organizing the amygdala is to divide it into a basolateral region (made up of the lateral, basal, and accessory basal nuclei), and a cortico-medial region (made up of the cortical, medial, and central nuclei) . There are, however, other common ways of anatomically dividing the amygdala as well. The amygdala has traditionally been considered part of the limbic system, a group of structures linked to the processing of emotions. The amygdala has historically best been known for its role in processing fearful emotions. When a threatening stimulus is present in the environment, it is thought that the amygdala is also involved in identifying it as a threat and initiating a fight-or-flight response to it. More recent evidence, however, indicates that the amygdala is active during the processing of positive stimuli as well. Thus, it is now thought the amygdala’s role is more complex than that of a “threat detector.” It may be involved with assigning positive or negative value to stimuli and with the consolidation of memories that have a strong positive or negative emotional component. It is also still being explored in a variety of other behaviors ranging from addiction to social interaction. Thus, its functions are diverse and still not fully understood. yt:video:EEUxKFmIUiI EEUxKFmIUiI UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-06-25T02:41:07+00:00 2017-07-25T14:12:13+00:00 2-Minute Neuroscience: Striatum In this video, I discuss the striatum. The term striatum is used to refer collectively to the caudate nucleus, putamen, and nucleus accumbens. The striatum is one of the primary structures of the basal ganglia, a group of structures best known for their role in facilitating movement. The striatum is also thought to be important to the processing of rewarding experiences and seems to be involved in the development of addiction. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the striatum. Striatum is a term used to collectively refer to a small group of structures found below the cerebral cortex that consists of the caudate, putamen, and nucleus accumbens. The caudate and putamen are separated from one another by a white matter tract called the internal capsule, but there are many strands of grey matter that cross the internal capsule, giving the structure a striped appearance. This is why the term striatum, Latin for striped, is used to describe the region. The striatum is often conceptualized a being divided into dorsal and ventral sections; the dorsal striatum contains the caudate and putamen while the ventral striatum contains the nucleus accumbens. The striatum is one of the principal components of the basal ganglia, a group of structures best known for their role in facilitating movement. The dorsal striatum is one of the primary input areas for the basal ganglia, and fibers from the cerebral cortex, substantia nigra, and thalamus all enter the basal ganglia via the dorsal striatum. The incoming fibers from the substantia nigra, which make up a pathway called the nigrostriatal pathway, are thought to be especially important to movement and are severely affected by neurodegeneration in patients with Parkinson’s disease. The nucleus accumbens, part of the ventral striatum, has been extensively studied for its role in rewarding experiences. The nucleus accumbens seems to be involved in reinforcement, reward, and the progression from simply experiencing something pleasurable to seeking it out compulsively as part of an addiction. The ventral striatum is thus activated when we do something we find pleasurable. The nucleus accumbens receives fibers from a dopamine-rich structure in the midbrain called the ventral tegmental area. These fibers are part of a pathway called the mesolimbic dopamine pathway which is a primary component of the reward system. yt:video:OGFQhLPaaOQ OGFQhLPaaOQ UCUgZq9PkDp1xaEivtcfJPSg Neuroscientifically Challenged https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg 2016-05-23T01:50:04+00:00 2017-07-29T19:44:21+00:00 2-Minute Neuroscience: Epilepsy In this video, I discuss epilepsy. Epilepsy is a chronic condition characterized by recurrent seizures. Seizures are characterized by excessive neural activity, which is caused by both increased action potential firing rates and increased synchronous firing (i.e. many neurons fire action potentials at the same time). When seizures originate in one area of the brain, they are known as focal seizures. Alternatively, when seizure activity occurs in widespread areas of the brain all at once, it is referred to as a generalized seizure. In this video I discuss these types of seizures and the abnormal brain activity that is associated with them. TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss epilepsy. Epilepsy is a chronic condition that is characterized by recurrent seizures; seizures are temporary disruptions of normal brain activity caused by excessive neural activity. Epilepsy can have genetic and acquired causes, but in most cases the cause is not known. Seizures can look drastically different depending on the patient, ranging from a brief and subtle interruption in consciousness to violent convulsions. One characteristic seizures have in common, however, is excessive neural activity. In a healthy brain, different groups of neurons are all firing action potentials at different times. During a seizure, however, firing rates are increased and groups of neurons all fire at the same time, leading to large spikes in neural activity. In seizures called focal seizures, this excessive activity begins in one specific area of the brain called the seizure focus, but it can also propagate to other areas of the brain. Neurons that are in the seizure focus experience a large and long-lasting depolarization followed by the firing of a train of action potentials. This abnormal activity is referred to as a paroxysmal depolarizing shift. The unusual activity is normally confined to the area it originated in, but during a seizure it can spread due to the failure of inhibitory mechanisms, leading to widespread abnormalities in brain function. In seizures called generalized seizures, excessive activity seems to arise in widespread areas of the brain all at once. Although the mechanisms underlying this are not fully understood, generalized seizures may involve a pervasive hyperexcitability of neurons throughout the cortex along with abnormalities in neural networks that connect the thalamus to the cortex.