Cellular Basis of Animal Behavior - Exam 2
State the basic reasons why invertebrates have been used as model organisms for neuroscience.
- They have relatively simple nervous systems compared to vertebrates. - The activity of individual neurons can be related to the behavior of the animal. - Their cells are also very robust meaning that they can withstand many experimental conditions without needing advanced technology. The nervous system can also be easily removed
Describe the experiments demonstrating color and pattern learning in bees, including the experiment demonstrating when bees pay attention to the color
Bees are able to learn color, shape and odor when recognizing good food sources. In a bee color study by Karl von Frisch a dish of sugar water is placed over a colored cardboard. this builds an association between the color and food source. Then the bees are given an unrewarded choice meaning that there is no sugar in any water. The bees chose the plate over colored paper meaning bees do perceive colors and can learn colors mean rewards. In another experiment bees were introduced to a disc of food that had a color selected through LED lights. When bees are then introduced to separate discs and given an unrecorded choice. One disc was colorless and the second disc was a disc of the same color as before. If bees could not tell color apart then the bees would be split 50/50 between the two discs. Bees begin to pay attention to color 3 seconds before feeding and stop after 2 seconds.
Outline the experiments demonstrating that bees are capable of conceptual learning
Bees are able to learn concepts and solve tasks based on the concept learned. An example of this is symmetry and asymmetry. The symmetrical group of bees were given rewards for identifying the symmetrical objects meanwhile bees in the asymmetrical group were given rewards for recognizing asymmetry. In tests were the bees were given objects to choose from bees that were rewarded for symmetry were able to discern symmetrical object and choose them and vice versa. With the concept of sameness bees were rewarded with food if they were able to fly to patterns similar to the pattern on the entrance of the box. Over time, bees were able to learn to associate food with the same pattern these bees were given a box with colors and bees were able to apply the same concept to receive food.
State the potential role for caffeine in bee learning and a potential mechanism for this
Caffeine is not toxic to bees unlike most insects and instead it actually helps them learn better to think of that plant as a food source. When sucrose is paired with caffeine and odor to test the PER response, 10 minutes after the experiment the results are the same as without caffeine meaning that the learning is the same. However as time goes on normal pairings are remembered much less compared to the caffeinated pairing which means that caffeine improves memory of the association. This is due to caffeine increasing the resting action potential of kenyon cells that keeps it close to threshold. Memory is based on activity and the more likely a neuron is to respond the more likely it is to become part of memory.
Outline the principles of classical conditioning and operant conditioning, and provide an example that applies to bee
Classical conditioning starts with natural relationships. There is an unconditioned stimulus and an unconditioned response and this changes through classical conditioning to elicit a specific response labeled the conditioned response. Classical conditioning in bees includes concepts like the plant color, its shape, time of day and odor. In operant conditioning experiments with bees there were disks with wells in the middle placed under a plastic material. This well contained sugar water and the bee was required to pull the well out from under the material using a string to receive a reward.This was done in stages where the bees were first given the disk with the well. Second, they moved the disk slightly under the table. Over time they move the well further under the table and the bee begins to understand how to pull the rope to get to the well. This is an example of positive reinforcement.
Contrast open with closed learners, then outline the 3 phases of song learning including key components of each. State when the critical period occurs with respect to these phases.
Closed learners are songbirds that learn one song and keep that one song for life. Open learners are songbirds that learn a new song every spring. Sparrows take a long time to learn their song (a whole year) meanwhile zebra finches learn their song fast (in 90 days). Canaries are open learning and learn a new song every spring. The three phases in song learning include the sensory phase, the sensorimotor phase and the crystallized phase. The sensory phase is when the animal is listening and learning its dads song. This is the sensitive/critical period. The production phase is when the bird is practicing the song and testing out syllables and phrases. The bird here is comparing the noise it makes to the noise it remembers from dad and adjusting based on memory. The crystallized phase is when the final song is produced.
Define command-driven inhibition and detail how it shapes the temporal properties of the tail-flip reflex.
Command driven inhibition is inhibition that is caused by the LGI circuit. This inhibition is very widespread and affects more than just the LGI circuit. The LGI behavior starts with a sudden sensory stimulus that activates sensory neurons in a coincidence which initiates behavior. Extension follows the flip movement and is delayed because the MRO responsible for extension is not activated until the flex is over with. Swimming is also inhibited by both the LGI and MRO circuit until after the flexing/extension occurs. This is to stop swimming from interfering with behavior so that they're not competing with one another. Right after a command is given via the LGI, inhibition acts almost immediately with one goal which is to keep the response short and effective with nothing interfering.
Outline the experiments that demonstrate that CS and US information converge in the mushroom bodies and how learning-related changes are represented
Convergence between the CS and US happens in a couple different places but it most importantly converges in the mushroom body. This was tested by using the neurotransmitter as a proxy for VUM activation which allowed researchers to control particular sites. This allowed researchers to activate "vum" by putting octopamine in calyx and pairing this with odor in a forward pairing. In this experiment when the two are paired it produces the desired response but when the octopamine is alone there is no effect. This shows that there is an important sight of convergence for memory in the calyx of the mushroom bodies. Fura-2 is a dye that when bonded with calcium glows. This is the basis of calcium imaging and it was used to measure the activity of neurons. The dendrites of kenyon cells were focused on and they found that there was gain and loss of connections because of learning. In this case all change, loss and again are important and demonstrate the bee learning association.
Define descending inhibition.
Descending inhibition is where the brain inhibits lower systems. This can present as restraint inhibition which occurs when the animal is being held down. The crayfish, aware that it is held down will inhibit the tail flip reflex because in this situation it is the least helpful circuit and may interfere with other behavior that can potentially help instead. The threshold for the LGI rises significantly and the behavior subsides.
Describe why giant neurons and electrical synapses are adaptations for speed
Everything within the LGI circuit is electrical which is why it's so fast. Invertebrates do not have a Myelin sheath, which is used in vertebrates to increase the speed of a electrical signal. Electrical speed relies on resistance to electrical flow. Myelin sheath is responsible for keeping internal resistance low and membrane resistance high. In invertebrates, where this does not exist to lower internal resistance, the diameter must increase to compensate and lower internal resistance. Membrane resistance is increased in invertebrates by decreasing internal resistance. This makes the cells very big. The end result is a fast electrical signal propped up by low internal resistance and high membrane resistance. Electrical synapses (gap junctions) which are formed by protein channels allows ions to flow through from cell to cell. This is done at the speed of electricity. There is no delay as a result of chemical communication which is synchronous
Describe what is meant by feed-forward and provide examples on how each acts to regulate the crayfish reflex
Feed forward inhibit goes from the sensory neurons to the motor neurons. This is inhibition that is acting forward in the circuit to inhibit something later. In command driven inhibition this is the LGI inhibiting motor neurons for muscles. A characteristic of feed-forward inhibition is rapid inhibition of the LGI and MoG. In feed-forward inhibition the motor neuron is excited very quickly before it is inhibited making the response very short and fast. Feed-back inhibition is the opposite of this.
Describe what is meant by feedback and provide examples on how each acts to regulate the crayfish reflex
Feedback inhibition is the process by which the LGI either inhibiting itself or inhibiting something that comes before it in the circuit. When inhibiting other the LGI activates inhibitory sites that act at the chemical synapses in the circuit. This produces something called pre-synaptic inhibition that decreasing the amount of chemical transmission to the interneurons effectively turning down sensory input. Recurrent inhibition is the LGI producing feedback that inhibits itself. In the process of the LGI activating motor giants it also inhibits itself. This is accomplished through the activation of interneurons that completely shut off the LGI after being stimulated by it. This inhibition is very strong and the LGI can not be reactivated so long as it is present.
Define habituation and describe the behavioral examples in the context of the tail flip reflexes.
Habituation is the process of learning to ignore something that has no real meaning. In the context of the tail flip reflexes this is when researchers began by touching the tail of crayfish repeatedly, triggering the ballistic movement and over time the crayfish beginning to ignore the touching when it realizes it doesn't mean anything. This is labeled as 'learning' and not adaptation because the effects of the experiment lasted up to 2 days in some crayfish. Learning in this context is a long lasting change in behavior due to experience. Habituation can also be influenced by environmental circumstances such as living in a crowded area vs a low density area.
Describe the social structure of the honeybee colony, and the foragers and scouts.
Honeybees have a caste system that starts with the queen on top. The queen lays the eggs and is typically surrounded by drones. Drones are males who are only responsible for fertilizing eggs and subsequently kicked out during the fall after mating season. Workers bees are sterile female bees that begin as house bees and evolve into foragers. Scouts are bees look for food sources then communicate with other bees about that food source. Forgers listen to the scouts then leave to collect the food. They then continue to visit the source of the food until the source dries up.
Describe the role of testosterone in the organization of song areas and in song crystallization
Hormones influence bird brain development and the majority of brain song areas contain androgen receptors. When bird sex hormones are altered through experiments bird reproductive behavior changes as they are important fro organization and activation of the song system. Organization is the development into either the male phenotype or the female phenotype. Activation is the generation of behavior, which can be the overall reproductive behavior of which songs play a critical part. In the RA, as juveniles there is no dimorphism in either female or male birds. As birds mature, the female RA area shrinks while the male RA area increases in size. Testosterone is what drives dimorphism. Testosterone also makes a big impact on song crystallization and this was demonstrated in experiments where male swamp sparrows were castrated and the songs began to degrade back into the plastic song. Meanwhile, high levels of testosterone correlate with the crystallized phase of song.
Define Immediate Early Genes (IEGs) and how they were used in these experiments
Immunocytochemistry was used to measure the expression of immediate early genes. These genes are activated very quickly under conditions related to learning a memory. In this experiments the tutors' song is played to the birds and then the brain is processed for the IEG. C-Fos is a protein that is a proxy for cell activity, as c-fos increases cell activity increases. The more similar the BOS and tutors were, the more c-fos there was. The last experiment used zenk as zenk and c-fos are similar in that they both can be used to measure cell activity. In birds that did not hear the tutors song there were lower numbers of zenk. Lastly, blocking pathway responsible for molecular mechanisms of memory during the sensory phase (learning) results in the song sounding similar to an isolates. This means that there is a decrease in syllables copied from dad and little similarity between the songs.
Describe the behavioral experiments that illustrate the importance of auditory feedback in song development and maintenance.
In a bird song template there is a song that is produced, and the auditory feedback that compares if what it hears matches what it remembers. Then based on that evaluation if there is something wrong with what the bird is producing, the song areas produces an instructive signal. This has the job of modifying motor symptoms to produce the appropriate song. To test if this is what occurs researchers conducted an experiment with two types of birds: deafened birds (who cannot hear their own song) and isolated birds who have never been exposed to the species song. The isolated birds start with a crude template followed by no learning. In the sensorimotor phase it matches what its producing to a crude template and this causes some impairment in song. In birds that were deafened, after learning the song of it's dad what the bird cannot do is match what it's producing to dad. Deafened birds showed very severe impairment in song.
Are these new neurons functional? Describe the experiment that proved this
In an experiment conducted to determine if the cells born do anything by connecting to song circuits experimenters injecting something into RA that tags cells that project to it. This means that experimenters were looking for cells that were double labeled. One label that represents a new neuron a second that determines if the cell is projected to the RA. In normal bird about 80% of bird in the HVc were double labeled and projected to RA. When experimenters castrated animals were was a drop in the amount of neurogenesis which suggests that neurogenesis is driven by testosterone. Still in this groups about 45% of new cells projected to the RA. This concludes that the new neurons seem to be functional and that these processes are largely driven by testosterone.
Describe how social status regulates the LGI's response to 5-HT (serotonin), including the concept of excitability (explain using Ohm's law).
In an experiment serotonin was injected into crayfish and the effects on the crayfish greatly depending on it's social status. In dominant or naive crayfish serotonin facilitated the LGI but in subordinate crayfish serotonin inhibited the LGI. Excitability of a neuron is determined by the neurons response to a stimulus. An increase in excitability means the cell responses greatly to the same stimulus. In terms of Ohm's law this means that when the current (stimulus) is kept the same, the voltage (excitability) will increase in response to an increase in resistance as the effectiveness of electrical synapses increases. Resistance increases in both naive and dominant, closing ion channels and lowering conductance. Input current was also measured in naive crayfish through an electrode that was placed in crayfish to measure voltage and resistance. This determined that when current was held constant that in the SIZ the resistance went up along with voltage.
Outline the basic circuit to the LGI, including the sources of the α and β components of the EPSP and the proportion of electrical to chemical synapses.
In the crayfish there are α and β pathways. The α pathway is an electrical pathway that carries signals straight to the LGI. The β pathway goes through an inter neuron where the first connection is chemical and the second is electrical. This process is delayed slightly because part of it is chemical. When a stimulus is introduced the β component appears after a delay. LGI's are also electrically connected to other LGI's. This means that all three motor giants act as a single LGI. There are about 1,000 sensory neurons that signal to 50 sensory interneurons that signal to one LGI.
Describe action-based learning by outlining how sparrows refine syllable production.
In the experiment, swamp sparrows were tutored with 5 different songs during the sensory phase. Sparrows, unlike finches face a time gap between the sensory phase and the sensorimotor phase. During the sensorimotor phase, the sparrows were found to have been practicing random syllables from the different songs that they heard including some syllables that did not come from any song. From the sensorimotor phase to the crystallized phase there is a big reduction in syllables types produced. About 32% of the syllables during the plastic phase were identical to the tutor and 18% were modifications. 50% of syllables created carry no relationship to anyone nevertheless, the crystallized song contained syllables that represents what they've heard from dad. This process is called action based learning which is the refining of song based on what the bird learns from dad and what is best for the environment they live in.
Outline the behavioral experiments that suggest the existence of the song template.
In this study white-crowned sparrows are played the white-crowned sparrow song and a song sparrow song. These birds are isolate were not exposed to a tutor, only the recordings of either song. As the bird moves from the plastic song to the crystallized song they crystallized only the song of the white-crowned sparrow. Innately they knew which one was their song. Some birds, in special cases, can learn the song of another sparrow if it comes from a live tutor. This is a social factor overriding the preference for its natural song. This demonstrates that innately birds know which songs belong to their species but social interactions also matter. In another experiment conducted, different types of sparrow songs were taped and cut up into individual syllables. These syllables were arranged randomly, with incorrect syntax and were then played for the swamp sparrows. Yet, as the bird began to develop it's song it chose to use syllables from its own species with correct syntax.
Describe how scouts communicate food sources via the waggle dance and how distance and quality are communicated
Karl Von Frische discovered that bee dancing is a repetitive movement that bees make and happens to be the basis of honeybee communication. There are two types of bee dancing. One movement called the round dance is done when bees have found food that is up to 75 meters from the hive. This dance does not communicate anything apart from distance. There is then the 'waggle' dance which is done when the food source is farther than 75 feet from the hive. Different aspects about this dance can communicate the direction and quality of the food source. The straight run part of the dance communicates the direction of the food and the speed conveys how far the food is. The faster the dance is, the closer the food is. How long the dance lasts indicates the food quality. If the quality is good the dance lasts longer to recruit more bees. Buzzing during this dance also indicates that the food is good.
Detail the experiments that examined whether area LMAN is the template, and from this draw a conclusion of its probable role in song maintenance
LMAN is important for song learning and not song production so the question was, is this the site of the template (representation of 'dad's song). In this experiment they played the BOS, the reversed version of the BOS and a con-specific song. The neurons responded positively to the BOS but not the other two controls. The hypothesis was that because LMAN, which is critical for song learning, has output to the RA that it instructs the RA on how to produce syllables based on memory. The alternative hypothesis is that LMAN is responsible only for encoding the BOS. At the end of the sensory phase LMAN neurons respond equally to the tutor, reversed and con-specific songs. At 60 days, during the plastic song phase cells respond equally only to the tutor and the BOS. To test if the neuronal response was to the tutors song or due to similarities, a third test altered the birds vocal cords to make the BOS sound different and here the neurons no longer responded to the tutor = not template
Describe the basic structure of the bee brain by taking the "bottom-up" approach to studying mechanisms of CC
Mushroom bodies make up about 1/3 of the entire brains neurons. This is important for learning, social behavior and spatial navigation. Kenyon cells are neurons that play a role in inputs and outputs in the mushroom bodies. They are found in the calyces and receive inputs at their dendrites from the antenna, known as the lip and the optic lobe known as the collar. The Kenyon cells then send outputs through the alpha and beta lobes. The CS pathway begins with odors reaching the antennas, which project to the antennal lobe. This lobe then projects elsewhere in the brain, including to the lip. The US pathway begins with taste that reaches the subesophogeal ganglion. Then the VUM neurons project to the lip and collar. These all then reach kenyon cells.
Evidence that this simple model of neurogenesis is likely not correct
Overall the simple model suggest that song learning is connected to neurogenesis and new neuronal connections and that losing song is caused by losing neurons.This model is not correct meaning that it has simplified to an extent that it does not take into account certain circumstances. For example, in some open learners their HVc and RA do not expand and shrink with the seasons alongside their songs which suggest these changes aren't absolutely necessary for seasonal learning. On the other hand some birds show seasonal variation in these brain areas with no degradation of song. These birds demonstrate area dimorphism with no loss of song. Lastly there are some closed learners that show seasonal variation despite only knowing one song for life.
Describe the experiments on cell PE1 as the output of mushroom body processing
PE1 cells are the output of the mushroom bodies and these receive input from kenyon cells and project out to different parts. The activity for these cells correlate with training history. These cells respond to anything the kenyon cells respond to including sight, touch and odors. PE1 cells frequency change that reflects learning when the CS and US are presented in a forward pairing. To sum up, when there is association training the PE1 neurons respond differently to the CS+ than under normal conditions and these changes in these neurons only last for about 30 minutes. This means that they may play a role in learning but are not where the memory is stored because the changes don't last.
State how the placement of inhibitory synapses can provide for relative or absolute control of neuron activity
Relative inhibition refers to an LGI that can be activated with a lot of stimulation because its threshold has increased. An example of this is food & restraint inhibition or habituation. Absolute inhibition prevents the behavior in a way that cannot be overcome. This is recurrent inhibition of the LGI where interneurons inhibit the LGI and the LGI cannot be activated until it stops. Recurrent inhibition stops action potentials from occurring and the threshold from being met, stopping behavior. Relative inhibition on the other hand, comes onto the dendrites which influences the behavior of the cell but not as strongly as absolute inhibition as it has to travel down to the SIZ making it weaker. Overall absolute inhibition activates the site of action potential formation and relative inhibition targets something more distal where it can be added or subtracted.
Define second order conditioning, and outline the potential role of VUM in this form of learning
Second order conditioning is the idea that the second conditioned stimulus has reward value. The conditioned stimulus means that something rewarding is coming and the stimulus has value. This idea takes a second stimulus that the animal does not care for (CS2) and pairing it to the CS will produce the conditioned response. This is because the CS has achieved reward value and now it can serve as the unconditioned stimulus. When applied to bees, this asks can a new odor that has not yet been used act as the new CS if the original odor acts as the unconditioned stimulus? The VUM activity acts as the US and odor one produces this activity. The question is: can sucrose be replaced as the US by odor one and can this produce new associations. Yes, it begins to signal the reward value and an association is formed. It may not be as strong as first order conditioning but it does work.
Differentiate between sensory (auditory) memory and sensorimotor memory. Provide experimental evidence that suggests auditory memory is in the HVC, then state evidence why this is likely wrong
Sensory (auditory) memory is the memory of dads song and sensorimotor memory is production during the plastic song where the bird learns how to produces specific sounds. It was found that with sparrows when the bird's own song or tutors song is played the neuron responds. However when a novel song is played (a song from the same species but not from the bird itself) the bird's neurons do not respond. The HVc however can not be the template for auditory memory because it does not fully develop until after the sensory period is over. This means that when the neurons are responding to the tutors song it's likely because the BOS contains elements from the dad's song and not because the bird recognizes the song as 'dad'. Overall this is likely not the template.
Describe how social hierarchies are formed in crayfish and how status modifies the escape reflexes. State the reasons why these modifications are important for the animal's survival
Social hierarchies are formed in crayfish by dominance. Dominance can be established by whichever crayfish is bigger than the others. If two crayfish are similar in size they engage in something called ritualized aggression. This is where two crayfish size each other up to determine which crayfish is the strongest. Behavior changes once this social hierarchy is established, in more dominant crayfish their posture is bigger and in terms of behavior they are much more likely to attack than to retreat. Crayfish who are subordinate are less likely to attack and more likely to retreat or not approach at all. Reflexes of the crayfish also change depending on where it is in a social hierarchy. Subordinate crayfish will want to swim away when in danger and the LGI reflex is inhibited, meanwhile dominant crayfish have facilitated LGI and are not likely to retreat. Swimming is important for subordinate crayfish because the LGI either push it towards its attacker or expose its underbelly.
Outline how song learning is studied and the general principles of learning obtained from these studies.
Song learning was studied by placing birds in isolation without a tutor (the papa bird) to teach them songs at a young age. In these cases birds can produce noise known as an isolate song. this is a song that has some semblance to the species song but it is incredibly abnormal in terms of syllables and syntax. This proves the bird songs are somewhat nature but nurture is absolutely necessary to produce a normal song. Exposure to the tutor must be experienced during the 'critical period' of the bird. This us a period early in development when the bird is young.
What is the hierarchy of song production?
Song production works in a top-down manner. In terms of activity, the hierarchy of song production begins with the HVc which activates the RA and then the RA controls motor output. In terms of function, first nXII is motor control. RA is responsible for song production and the HVc is responsible for phrase structure.
Describe the CS processing pathway, and how inactivation experiments demonstrated the progression of memory representation in this pathway
The CS pathway includes projection neurons that receive information from the antenna and project it to the antennal lobe and these then project to the kenyon cells in the MB lip. In the experiment researchers temporarily disabled the CS by chilling the brain part responsible for odor. What was found is that if the area is cooled before conditioning then learning is effectively blocked which means that this area is essential for association to occur. In the antennal lobes, if the brain is frozen immediately after conditioning, the memory is knocked out. However when researchers wait a minute or two the memory is present meaning that this area is critical for memory and association early on but becomes progressively less involved with time suggesting that the memory is transferred.
Define what is meant by a command neuron, state the required criteria of necessity and sufficiency, and outline why both criteria must be shown. Describe how this was done for LGI reflexes.
The LGI acts as a command neuron meaning that a reflex is enacted in an all or nothing fashion once the LGI is active. For something to be a command neuron a neuron must exhibit activity that is both necessary AND sufficient to produce a behavior. Sufficiency is the activity being sufficient enough to produce the behavior and necessity is tested by inactivating the neuron and tested if neuronal inactivation inhibits the behavior. Both of these combined means that if the neuron is active, the behavior is produce. And if the neuron is inactive the behavior is not displayed. This was studied in LGI reflexes when they removed the nervous system from the crayfish and placed it in a dish. Electrodes were attached to the sensory nerves and a motor nerve was used to record the behavior of the sensory neurons as they were hyper-polarized. When the LGI was hyper-polarized the action potential never fired and there was no behavior proving its necessity. When depolarized the opposite happened.
What is the LGI escape reflex? What about the MGI
The LGI escape reflex, also known as the lateral giant interneuron escape, because this is the central point of the circuit that underlies the behavior. This behavior occurs when the back part of the crayfish is touched and it triggers the ballistic movement. This behavior only requires what's in part of the abdomen of the animal (not the whole body) and which makes the neuronal circuit easy to collect and study. This shoots the animal straight backwards. The MGI on the other hand is the circuit that controls what propels the animal backwards when it's head is touched. This requires more of the animal which makes it harder to study. Both of these are ballistic movements
Outline the experimental evidence for the NCM as the potential site of the template.
The NCM is an area in the higher auditory system that emerged as a candidate for the template. This is found in Wernicke's area, the auditory association cortex. When lesioned, it impairs the recognition of the tutors song and it's neuronal activity reflects the memory of the tutors song. Finally if the HVc is prevented from acquiring a memory from this are, the memory of the tutors song components are eliminated. In a test with zebra finch, birds were placed in a cage with two songs playing: one of the tutor and one of another bird. Typically birds show a preference for the tutors song however, after lesioning the NCM, zebra finch no longer showed a preference for the tutors song. This reaffirms that the NCM may be responsible for holding memory of the tutor.
Describe how US information is processed, and outline the experiments confirming the role of VUM as the signal for reward value
The US pathway contains VUM cells and they are associated with the sense of taste. The VUM cells respond to sugar and project to the MB and antennas. VUM cells act as the US signal meaning their cellular activity is equal to the US itself. When these cells were activated with no sugar researchers were able to classically condition the bee but only when the odor and sugar were paired correctly with odor first. In backwards pairing when the sucrose came first and then the odor there was no activity in M17 cells during the test. VUM responds to both the US and the CS meaning it carries the reward status of the stimulus. This neuron carries reward and it predicts reward (odor associated with sucrose). This means that the odor alone is rewarding in VUM cells.
Provide a general overview of the organization of the song system, including evidence that the system is lateralized
The bird song system is a specialized system and exists largely independent from the auditory system. The bird song system can also be broken down in areas that are responsible for song learning during the sensory phase and song production during the sensorimotor phase. In studies conducted if HVc or RA are lesioned song production is impaired and if LMAN or Area X are lesioned song acquisition are impaired. If the song is already crystallized, when LMAN and Area X are lesioned there is little effect on the song. In male birds, the HVc and RA are larger and considered dimorphic. LMAN is not dimorphic but Area X is. These areas may also change with season by shrinking and growing. Bird brains also exhibit laterality with the left side of the brain being used for song function. When the HVc (left side) is lesioned there are significant deficits in producing syllables in meaningful way.
Outline the basic circuit underlying the LGI reflex from muscles to motor neurons to the LGI
The fast phasic muscles are found in the abdominal area of the crayfish. They are designed to contract and stop contracting fast. These are organized in antagonistic flexor and extensor pairs. They inhibit one another mutually in order to control movement. These make up the tail flip reflex. The motor giant controls this reflex. If the back of a crayfish is touched only the font abdomen contracts meanwhile if the front is touched the whole abdomen contracts. The LGI connects to the motor giants in the first three segments of the abdomen but the MGI connects to all seven segments of the motor giants. The LGI controls the motor giants which controls muscle.
State the three reasons why some birds sing
The first reason bird sing is territorial reasons. Birds sing to defend their territory from male birds and advertise it to female birds. The second reason includes regional dialects. Birds have regional dialects in their songs and can be driven out of an area if it does not match the area. Last reason is to attract a mate. Songbirds contain brain areas in the forebrain that are responsible for singing that are absent in birds who do not sing. The three most researched songbirds are sparrows, canaries and the zebra finch.
Describe the basic organization of the crayfish nervous system and an invertebrate ganglion
The ganglion is a collection of nerve cells. In crayfish there is the brain, the thoracic ganglia and abdominal ganglia. The abdominal region is responsible for key reflex mechanisms and tail movement and contains 6 ganglion's ((technically 7) which are all each responsible for a specific section. Connectives connect ganglia to each other and are useful for allowing the crayfish to share information between ganglion's to coordinate behavior more broadly. In an invertebrate ganglion, neurons lay on the outside. The connectives between ganglion's run through the neuropil located in the middle of the ganglion. This is the area of the ganglia where neurons interact and form synapse with each other.
Define neurogenesis and provide evidence and a general model of how this might be involved in seasonal changes in song production.
The general model of seasonal song production starts with a plastic song around April which moves to a stable song in June. Throughout these months there is an increase in HVc and RA volume and an increase in testosterone. In the months July to march there is a decrease in HVc and RA volume and a decrease in testosterone. This model suggests that the growth and shrinkage of these areas support the gain and loss of the memory of a song. This proposes that change in volume is to accommodate new neurons. In an experiment done dying neurons were tagged specifically and so were newly born neurons. What was seen was that neurogenesis increased during song crystallization which implies that the new neurons are responsible for holding song memory. Cell death occurs at high rates near the ending of the mating period as the bird lets go of the previous song to accommodate learning another
Describe the basic structure of bird song and relate this to the structure of human language
The hierarchy of birdsong language begins with notes. This is one continuous sound and combining multiple notes makes a syllable (human equivalent of words). A syllable is a unique combination of notes and next is a phrase. A phrase is a combination of syllables (a sentence). Lastly syntax is the combination of phrases added together to make the song according to the 'rules' of a species language. A full sparrow song contains three phrases the first phrase begins as a whistle and moves to a trill in phrase b. Lastly in phrase C there is the last buzz.
Describe the properties of electrical synapses that underlie the coincidence detection which determines whether or not sensory input will activate the LGI
The nature of sensory input determines the decision to flip or swim. Sensory input being sudden or gradual also makes a difference on what behavior occurs. Coincidence detection describes the population of sensory input that hit the LGI and their timing. This is mediated by the electrical synapses that hit the LGI. Electrical synapses pass better from pre-synaptic cells (sensory neurons) to post-synaptic cells (the LGI) in this direction. When the inputs are coincident the current reaching the LGI is large but if the inputs are delayed the current isn't as strong. The greater the voltage (V) difference between the pre and the post, the greater the current is. The current (I) is equal to conductance (G) * voltage (Vpre-Vpost). So current is conductance times the driving force.
Describe the procedure for classical conditioning (CC) of the PER, and state the CS, US, CR, and UR in these experiments
The procedure for classical conditioning of the proboscis (tongue) extension response begins with the unconditioned response that the bee exhibits in the presence of sucrose. The bee reflexively sticks out its tongue when there is sucrose in front of it. Because the bees' antennas stick out in front of it, the most common conditioned stimulus is odor. The sucrose is placed on a toothpick and at the same time there is an odor system that will puff a scent onto the bees antenna at the same time it feeds. Then the PER is measured in relation to the odor that is hitting the bees antennas. The closer in time the conditioned stimulus and the unconditioned stimulus are the better the connections are formed and the faster learning is. The unconditioned response is the bee sticking out its tongue, and the unconditioned stimulus is the sucrose. The conditioned stimulus is the odor and the conditioned response is the PER.
Describe the basic circuit for re-extension and how is is a form of chain reflex.
The re-extension circuit is activated by the muscle receptor organ, which is a circuit separate from the LGI. This circuit is activated by the behavior of flexing itself and controls extension. A chain reflex is a sequence of reflexes where one is activated by the other: the extension is activated as a consequence of the flex. When the MRO is active is can directly activate the extension motor neurons and also activates flexor inhibitors. Likewise, the activation of the flexor circuit (LGI) inhibits the MRO as they are mutually inhibitory. They cannot exist at the same time but the behaviors follow one another.
Describe the evidence for the role of the HVC in song production using measures of HVC size, impacts of lesions, and effect of electrical disruption of activity
The size of the left HVc matters in terms of the complexity of the song. As the volume of the HVc increases the number of syllables in the song increases. When females are injected with testosterone this correlation was also noted. Singing is positively correlated with the volume of HVc and in bird species where there is no difference between male and female HVc size, both genders report the same amount of song production. In lesion experiments as the HVc is lesioned syllable production remains fine but phrase production is hindered. The syllables are no longer arranged in a way that makes sense. With electrical stimulation of HVc activity, the jolt causes a 'phase-shift'. This disruption causes the HVc to jump syllables ruining the song sequence, highlighting the importance of HVc in temporal patterning.
Describe the escape behaviors of the crayfish (tail flips and swimming), and how they differ in terms of activation and basic movement
The tail flip reflex is a very quick movement made by the crayfish in response to a specific stimulus. This is known as a ballistic movement because once the crayfish starts it, it is always carried out the same way, at the same speed every time. This is used to get away/put distance between the crayfish and its predators and inhibits any other behavior the crayfish was exhibiting prior. Non-giant swimming is used by crayfish to move around. Because of its purpose, this is not a ballistic movement but rather an adaptive, flexible behavior. This means that this behavior takes longer to begin and can last for much longer than a ballistic movement. Swimming does not use rapid escape neural circuits.
Outline the model of how the song template is used to both learn and produce a song.
The takeaway from the previous experiment with swamp sparrows is that birds seem to have an innate song template that acts as a filter that allows the bird to recognize species specific syllables during the sensory phase. Learning during the sensory phase then adds to this innate template to make the song more specific. Then during the sensorimotor phase auditory feedback is matched to correct the birds song before it can be crystallized. If there is a mismatch between thee song that is developing and the template then a signal is send to the motor nuclei to adjust the song.
Outline the 3 components of the development of song production including key components of each.
The three components of song production include the subsong, plastic song and crystallized song. In birds the subsong is the equivalent to babbling. This is a meaningless repetition of sounds. The plastic song phase is where syllables and phrases begin to appear to try and mimic dad. This is where song elements are produced during the sensorimotor phase. Lastly, the crystallized song is the final song. This is species typical with correct syntax.
Outline the evidence and state the model on how different kinds of 5-HT receptors may underlie the differences in LGI's response to 5-HT depending on status
There are two types of serotonin receptors that crayfish contain named 5-HT1 and 5-HT2. 5-HT1 receptors required more serotonin to activate meaning that this receptor increases the threshold necessary for LGI response, even in dominant crayfish. When 5-HT2 receptors were activated, irrespective of status, the threshold decreased. This means that the type of serotonin receptors and the proportion of them in a crayfish is what drives the LGI response. For instance subordinate crayfish have a higher proportion of inhibitory 5-HT1 receptors and vice versa.
How is the waggle dance adjusted for time of day,
To communicate direction bees communicate with respect to the sun. This means that on a flat surface the direction of the source is communicated at an angle with respect to the sun. But on a vertical source such as a hive orientation is with respect to gravity. The bees also adjust how they dance to compensate when the sun moves. Bees also have a sense of time which allows them to adjust their angle of the dance to compensate for time passing to help find the food source accurately. A bee's internal clock is related to their metabolic rate so in experiments where bees are chilled they tend to arrive late to their destinations.
Describe the experiments that demonstrate the accuracy of bee communication
To determine how accurate the waggle dance is a food source is placed outside of the hive. The bees will learn where the source is and when it goes back to the hive, extra food sources are placed around the hive and this gives opportunities to the bees to choose another source of food. When this is done, the communicated source is where the most bees go to regardless of other sources being at their disposal. This illustrates that bees are very accurate in their communication regarding direction. In terms of distance, a similar experiment is conducted and food is placed at different locations from 75 to 2500m away. Most bees in this experiment went to the communicated distance proving that they are fairly accurate with distance as well. Some bees stopped at food sources that were shorter than the communicated food sources distance because it makes sense for bees to get good food at a source that is not so far but most bees overall headed to the food source that was communicated.
Describe the experiments that illustrated the importance of this for restraint and feeding inhibition, as well as for habituation
To test descending inhibition in one experiment the nerve cord from the brain to the abdomen, that is responsible for LGI, was severed. Then when the crayfish was then restrained, descending inhibition no longer appeared. In another experiment the nerve was blocked using sucrose and likewise the action potential was blocked and failed. Another example of descending inhibition is feeding inhibition. When the crayfish eats the threshold for an LGI reflex has increases and the crayfish responds less to stimulation. With habituation, as the crayfish is repeatedly stimulated over a period of time, more stimulation is needed for an action to occur. The threshold for the LGI increases and the response decreases because the stimulus is no longer perceived as a threat. The interneurons do not change in responses but the LGI does, meaning that descending inhibition runs from the brain to the LGI. This makes sense as the LGI is the command neuron.
Outline the process of foraging behavior, and discuss evidence that the bees use landmarks in navigating an environment
When foragers first leave the hive they leave to scout landmarks near the hive that will help them find the hive when they return. Bees have some innate memory that help them determine what is a good source based on shape and color and this can also be learned. On the flight back to the hive, bees take direct flights back using landmark cues and the position of the sun. An experimenter trained bees to forage on a simple path. As the bees were coming back he would capture them and release them at different points south of the hive. He found that bees could travel in circles for a minute before going straight back to the hive. This determined that the bees don't travel south to get home but rather use landmarks around them to find their way back home. There are likely other ways the bees use their surroundings and nature to locate home but it's definitely not as simple as the myth of them heading south.
Describe the relationship between social status and the behavioral effect of serotonin. Include the time course of these effects.
When serotonin was injected into naive crayfish it was found that the LGI reflex was facilitated and they began showing traits of dominant crayfish. In dominant crayfish it did just the same by increasing the reflex itself and lowering the threshold. However in subordinate crayfish what serotonin did was increase the LGI threshold inhibiting the reflex, therefore making them more subordinate. The differential effect takes about 12 days after establishing hierarchy. This means that when two isolates fight the subordinate won't experience inhibition by serotonin until 12 days after. When dominant crayfish battle, the new subordinate crayfish takes 38 days for serotonin to inhibit the LGI.