How is biology related to psychology, behavior, and cognition
Question 1 of 10 Cost 15.0 Points each answer Discuss the literature on split-brain and lateralization of function. What does the research tell us about each hemispheres ability to function independently (e.g., cognitively, creatively, etc.) and in unison? What are the implications for the cognitive neuroscientist in terms of research?
Question 2 of 10
15.0 Points Discuss one of the psychiatric disorders presented in chapter 11 of your text. Please be sure to address both the physiological and behavioral aspects of the disorder (signs and symptoms, biochemical or genetic theories, etc.), and pharmacological and behavioral treatments for the disorder. What is the role of the biopsychologist or neuroscientist in this type of research?
Question 3 of 10
15.0 Points Discuss sleep in terms of the normal sleep cycle. Please be sure to address the stages of sleep and physiological correlates associated with each stage. How does dreaming fit into our conception of a normal sleep cycle? Address theories of dreaming. What are the consequences of disruption of sleep? Question 4 of 10 15.0 Points Critically evaluate the means theories that have been used to explain e motion. Which do you think is the best theory and why?
Question 5 of 10
15.0 Points What brain regions and neurochemical systems are known to be involved in the regulation of sleep? What is known about the neurobiology and endocrinology of circadian rhythms?
Question 6 of 10
15.0 Points What brain structures and circuits are known to be particularly important for human memory? Please discuss the evidence linking the hippocampus with an involvement in cognitive mapping and spatial memory.
Question 7 of 10
15.0 Points Compare and contrast Broca’s aphasia with Wernicke’s aphasia. What cortical regions need to be damaged to produce these types of aphasia, and what do they tell us about the brain mechanisms underlying language?
Question 8 of 10
15.0 Points What are the differences and similarities in the action of cocaine and heroin on the brains reward systems? Do all addictive drugs work by causing the release of dopamine in the nucleus accumbens? In what ways have learning and conditioning been shown to be important determinants of drug tolerance?
Question 9 of 10
15.0 Points “Brain scanning technology is providing new insights into our understanding of the brain.” Explain how CAT, MRI, PET and fMRI scanning works, and some of the ways in which this technology has been used to justify the above statement. Please provide an example to support your answer.
Question 10 of 10
15.0 Points In what ways has the abnormal formation and deposition of amyloid been implicated in the pathogenesis of Alzheimer’s disease? How can cognitive reserve be built up? What evidence shows that this can have beneficial effects for maintaining mental functioning later in life?
Here are the answers of each Question Above (10 questions)
1. Answer The discovery of the brain having two hemispheres with different functions was first discovered in the 1960s from patients who underwent a surgical procedure called commissurotomy. The procedure involved completely severing the corpus callosum. Early studies performed by Roger Sperry and Michael Gazzaniga, soon found different functions were responsible in each hemisphere, and the ground breaking phenomena of the left and right brain was called lateralization. The left hemisphere was found to be responsible for forming language and speech. It is also responsible for sequential and analytical thought processes such as problem solving, analyzing data, and statistics. The right hemisphere helps with visuospatial tasks such as jigsaw puzzles and sorting blocks, focusing, as well as synthetic analysis and perceptions. The right side is more superior to the left in processing emotions and tones used in speech. The left side is more rational. It is because of these differences the left is often referred to as the analytical side with the right being coined the creative side. When they work together in unison, studies showed visual information was processed individually to each cortex with the left visual field going to the right hemisphere and the right visual field projecting to the left hemisphere. A second experiment was conducted with touch, and it was discovered like in the visual experiment, the somesthetic pathways worked by crossing from the right side of the body to the left hemisphere, and vice versa. The difference between the visual and touch was with the visual both hemispheres worked together simultaneously, while in touch if the right hand was holding something only the left hemisphere would show activity while the right remained inactive. Even though the right hemisphere is not responsible for speech and language, it is not completely ignorant to linguistic abilities. An example would be a person hearing a verbal description of an object could feel a number of objects with their left hand, and successfully pick out the correct one. The same was shown when a word describing an object was flashed to the right hemisphere the left hand could select the object behind a screen (Wickens, 2009, p. 387). The most significant difference for language was shown when people could think and process the information on the right side, but were unable to verbalize the information without the left side. The advantage of having what Gazzaniga and Sperry termed dual systems or dual consciousness, is how well the two systems balance each other, allowing for an individual to process information without losing veracity.
When working independently if a person is asked to perform a right sided brain function with the right hand, their left hand would constantly try to take over the task because the task would be very difficult to achieve with the right hand. If the left hand is holding a book while a person is trying to read, they will often find themselves placing the book down, because the right side of the brain does not process words that well, thus processing holding the book as pointless. This caused Sperry to theorize the brain had two separate minds. He proposed each hemisphere had its own awareness levels as well as conscious levels with its own memories, ideas, perceptions, and sensations. Gazzaniga believed the left hemisphere acts as an interpreter, rationalizing the totality of everything a person is encountering trying to bring order and understanding to our conscious lives. For example a person had an image of a winter landscape with snow placed in the right hemisphere, and a chicken claw in the left. When shown other pictures which could go with the first one’s shown, the patient pointed to the appropriate pictures with the left hand pointing to the shovel, and the right hand pointed to the chicken (Wickens, 2009, p. 387). This experiment showed even though the patients pointed to the correct pictures they did not fully know why they chose the picture. They would oftentimes create stories to attempt to rationalize their choice. It’s this latest finding from Gazzaniga which implies further research is needed, to see why the left brain works to try to find meaning even if there is no meaning there. A second implication of further research is the cerebral dominance of language or a mixed dominance. This is a rare instance where a person’s language is localized in the right hemisphere of the brain or equally spread across both sides, instead of on the left like majority of human beings. Also further research is implied in terms of consciousness. In a normal brain, the brain has a number of circuits that connect and activate certain parts of the brain which enable millions of conscious thoughts or moments. Researchers are attempting to find answers behind what makes a human being unique in their conscious states.
References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
2. Answer The psychiatric disorder I chose to discuss is bipolar disorder. Bipolar disorder is a psychological disorder which causes a person to alternate between feelings of extreme happiness with excessive energy (also known as mania), and low bouts of depression. A period of normalcy is reached somewhere in between, but the severity of the other two types of moods are disruptive for normal activities in a person who suffers from this disorder. The often mood changes between mania and depression is why it is sometimes called manic-depression. Manic or hypomanic phrases can cause the person to exhibit reckless behaviors engaging in high risk activities, having poor judgment, aggressive behavior, easily distracted, decreased need for sleep, exude inflated self-esteems, and disregarding any danger in terms of their life. They will often be sexually promiscuous, substance abusers, poor performers at work or at school, as well as making unwise financial choices such as going on spending sprees and gambling (Mayo Clinic, 2013, p. 2). When the mania is in full force the person will eventually begin to hallucinate and become delusional. Then the body slows down causing disinterest in things and the person becomes withdrawn. They may continue to feel they are normal, but eventually the low state ends with them becoming severely depressed. The depressive phase includes feelings of sadness, hopelessness, anxiety, fatigue, problems concentrating, chronic pain with no known cause, and poor performance at work or school. The depression often leads to people becoming suicidal if they suffer from this disorder. Other signs and symptoms include the rapid cycling (occurring four or more times a year), seasonal changes in mood called seasonal affective disorder (SAD) where the moods depend on the season, and psychosis, a detachment from reality (Mayo Clinic, 2013, p. 2). The length of time spent in each episode (mania and depression) is dependent upon each individual person. Some people suffer from the cycle of mania and depression only a couple of times a year or even in a lifetime, while others go through rapid cycling, and their whole life is disruptive. The severity of the cycles is how doctors separate people into different classes of bipolar disorder which are bipolar I, bipolar II, and cyclothymic disorder. Each subtype is different with its own symptoms and patterns. Bipolar I disorder is the most severe type which causes the most life disruption with the person experiencing difficulty in their job, school, or personal relationships. Bipolar II is less severe, and is characterized by people having hypomania (mania without the lapses in judgment) verses full-blown mania, and major depression. They tend to lead a normal daily routine, but when they get depressed at this stage it usually lasts longer than their hypomania stages. Cyclothymic disorder is what is considered a mild form of the disorder, with the high and low stages of hypomania and depression not being as severe as the other types.
The cause for this disorder is currently unknown with some people suffering more from problems with mania, while depression is the main concern for others with bipolar disorder. There are also people who have an equal amount of issues with both where they occur all together called mixed episodes. The signs and symptoms of bipolar disorder usually begin in adolescents with the child exhibiting reckless behavior, explosive tempers, aggression, and rapid mood changes (Mayo Clinic, 2013, p. 2). Even though the cause is unknown, many doctors believe the disorder is highly genetic, with evidence that people with the disorder have biological differences in their brains. The changes are not significant enough to be pinpointed in helping to find a cause. There are several factors which can trigger a bipolar episode which are stressors from the environment, hormone imbalance, or an imbalance with neurotransmitters in the brain.
Treatment for bipolar disorder includes psychotherapy, support groups, and medications, and is considered a lifelong ordeal. Even if the person feels better they should continue to take their medications because it is not something that will go away on its own. Medications such as anticonvulsants (Depakene, Stavzor, Depakote, and Lamictal), Symbyax, Benzodiazepines (Valium, Ativan, Klonopin, Librium, Niravam, and Xanax), antidepressants, antipsychotics (Abilify, Zyprexa, Risperdal, and Seroquel), and the most common Lithium. Researchers or neuroscientists believe if they can discover the biochemical processes on how lithium works in the brain, along with the physical differences in the brain, they could discover a cause for manic depression. The problem is lithium works on almost every neurochemical system in the brain, and the molecular changes or cellular changes in the systems which cause the different behaviors are still unknown.
References:
Mayo Clinic. (2013). Bipolar disorder. Retrieved on December 24, 2013, from http://www.mayoclinic.com/health/bipolar-disorder/DS00356
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
3. Answer
Sleep is a very important and necessary function in which we need in order to live a healthy life. We need to sleep for body restoration and evolutionary adaptation. In fact, one-third of our lives are spent sleeping. During our normal sleep cycle or slow wave sleep (SWS) our brain waves gets slower and become synchronized as we go through four different stages of sleep. The first stage of sleep is the when a person first begins to feel sleepy (the onset of sleep). It is often described as the transition between waking and sleeping. Most people say they are just feeling drowsy in this stage. Stage 2 is when a person is actually asleep. During this stage, brain waves called theta waves (waves ranging between 4-7 Hz) are interrupted for half a second with bursts of activity known as sleep spindles (waves between 12-15 Hz). In Stage 3 these spindles slow down and the brain waves move into the delta wave area (1-4 Hz). The last stage, Stage 4 is when we are in our deepest sleep state. It is difficult to wake a person who has reached this stage of sleeping. 50% of the brain is dominated by delta waves, making for very little brain activity. During the SWS cycle the brain and body undergoes a number of changes. Blood flow to the brain decreases to approximately 25% of the amount used when we are awake, to appear more restful. The body appears more relaxed as well, and our breathing, heart-rate, blood pressure, and body temperature all decrease. Following the four stages of sleep is the rapid eye movement sleep (REM). This is where dreaming occurs, and usually happens for the first time after 90 minutes of SWS. The brains electrical activity begins to pick up, and moves faster with the waves being smaller. The waves are very similar to beta waves which occur when we are awake. The body appears to be paralyzed due to a loss of muscle tone, but the brain activity causes twitching of the face and eyes as well as toe and finger movement. The different activity stages of the body and the brain is described as a form of sleep called paradoxical. Blood pressure, heart rate, respiration, as well as blood flow to the genital areas are all increase during REM sleep. So, even though it appears the body is resting, in fact the internal body is experiencing a lot of activity. The body will continue to go through a cycle of SWS and REM sleep four to five times a night, with the REM sleep occurring at 90 minute intervals. With each cycle REM sleep will increase going from 20 minutes the first time to 40 minutes the last time. Eventually stages three and four no longer occur, and the last sleep cycle is mostly considered stage 2 SWS.
As mentioned before dreaming occurs in REM sleep, and it is hypothesized the reason behind the body being paralyzed during this phase is to keep people from acting out what they are doing in their dreams. Nathaniel Kleitman and William Dement found sleep occurred in two forms and were associated with different kinds of dreams. They believed 80% of people dreamed during REM sleep while 20% dreamed during SWS. REM dreams they theorized followed a story line, and included intense and vivid situations which may seem illogical to the person when they are wakened. SWS dreams were just a repetition of ideas which had no point or real purpose behind them. It is believed every person dreams during their sleep cycle, most tend not to remember them, therefore they do not think they dream.
Sleep deprivation impairs a persons’ performance for difficult or complex mental/ physiological tasks because continuous concentration is required to accomplish those tasks, while simple tasks are not seriously affected at all. Some of the consequences of being sleep deprived are: slow reaction times, memory and sensory responsiveness as well as a decline in body temperature. Other effects are lapses of concentration, extreme irritation, and short periods of disorientation with hallucinations (Wickens, 2009, p. 260). Some researchers believe if a person experiences to much sleep deprivation, it can result in death, due to infections and a weakened immune system. A study conducted to examine what effects selective sleep deprivation could cause, concluded with results varying between some people exhibiting signs of sleep deprivation, while others experienced none at all. One interesting find from the study was how people will usually make up for any lost sleep they encountered.
References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
4. Answer Emotions are a very important part of our survival as a human race, and have sparked several different theories on what causes them. Emotion is a word which means to move or to disturb, causing one to prepare or prompt one into action signaling something important is happening (Wickens, 2009, p. 210). Emotions create every feeling we have from love to hate, and from joy to sadness. The physical changes we experience from our autonomic nervous system (ANS) such as increased heart rate and breathing, or having a sense of butterflies in the pit of the stomach are all signs of emotional arousal. The ANS is comprised of two parts the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). SNS is responsible for our fight or flight response preparing us for danger, while the PNS stimulates relaxation, signaling to the body to conserve its energy. The first is theory discussed was the James-Lange theory. Philosophers Williams James and Carl Lange proposed autonomic changes and the reaction resulting from an experience, comes before an emotion is attached to the experience. “Put another way, the conscious sensation of an emotion occurs only after we received feedback about the changes taking place in our body” (Wickens, 2009, p. 211). James and Lange believed a stimulus processed either visually or from the auditory cortex, would assess the emotional significance of the stimulus, passing it through the ANS. This would set our bodies into motion to respond with either a “fight or flight” response (produced by SNS). The bodies’ arousal levels will be detected by the conscious brain, which would in turn interpret the emotional nature of the physiological state (Wickens, 2009, p. 212). The emotion is only conscious after it is created first in the visual or auditory cortex, and then the reaction to the stimulus is associated with the experience. In essence, running away from a spider (frightening stimulus), causes the heart rate to increase, which will cause the person to feel afraid. One of the main problems with this theory is emotions such as love and hate ‘feel’ different (Wickens, 2009, p. 213). James and Lange believed each emotion had its own unique set of physiological responses to certain stimulus. These visceral and somatic changes tell the brain what emotion it is experiencing. To further support their theory the men argued it was not possible for a person to feel an emotion without the body’s response accompanying it. James and Lange tested their theory using paraplegic men. It was hypothesized reduced sensations of the body would decrease the emotion felt. The results proved the men who just had damage to their lumbar area experienced no changes in how they perceived emotions. On the other hand, people who suffered from severe spinal damage reported changes in how they perceived emotions. An example of this was how one man described anger as not having the “heat” that it used to, and that it was more mental than physical. A second theory for emotion is the Cannon-Bard theory of emotion. Physiologist, Walter Bradford Cannon, set out to prove The James-Lange theory wrong. Cannon found during an experiment emotions were experienced mentally before any physical signs began, unlike how James-Lange theory stated SNS had to be sent to the brain before the person experienced the emotion. Cannon concluded emotion was not dependent on the body’s physical response to stimulus; instead the stimulation of the ANS induces the arousal state preparing the body for a threat, while the emotion is perceived in the cerebral cortex. They both occur at the same time and independently. He believed the autonomic arousal and the interpreted cognitive response occurred at two different pathways with the routes connecting at the thalamus. The thalamus was believed to send the information to the cerebral cortex and the spinal cord to initiate visceral changes associated with the emotions. Cannon also disputed James and Lange’s stance on emotions having their own set of physical reactions; instead he believed the ANS responded the same way for all emotions. Philip Bard helped to further support and contributed to the Cannon-Bard theory when he discovered the hypothalamus (which receives input from the thalamus and the cerebral cortex sensory areas) controlled the ANS, and the physical states associated with emotions. In essence, Cannon and Bard believed emotional behavior depended on the hypothalamus, and no feedback was required from the PNS in order to produce an emotion. Using the spider example from before, if we see the spider, we will run because of the mental fear associated with the spider, which causes the body to respond with sensations of fear, both together and independently. Another alternative theory for emotion is Stanley Schachter and Jerome Singer’s, cognitive-arousal theory. This theory proposed once a person becomes aware of the changes in arousal levels the body is experiencing, the mind attempts to understand cognitively why it is happening. It was believed we associate our emotions to our environment. The placebo effect is an example of this theory. A person is told they would feel a certain way with pill, and because they were told they would experience certain psychological effects, they would exhibit the effect. This study further supported the notion that general states of arousal motivate different emotions, as Cannon and Bard proposed. But it also supported the James-Lange theory in that the autonomic arousal such as increased heartbeats sends an important signal to the individual to interpret the emotion. The separation of the latter piece of evidence was the evidence of one type of physiological arousal causing several different types of emotions instead of one being assigned its own unique set. Schachter and Singer believed the signaled emotion was left up to the individual person to decide which emotion they would believe they experienced. In my opinion the Cannon-Bard theory. Using my spider example, I believe increased heartbeats and breathing are associated with fear. Seeing a spider would cause me to run, because I am fearful of spiders. The running away along with the fear of the spider would cause the increased heart rate and heavy breathing. I believe a person has to have a certain amount of emotion for a situation already in order to comprehend what is happening. Like in my case, I already know I fear spiders, so seeing one would cause me to immediately feel fear while also running away. A person can be surprised by a spider and the surprise factor could give them the increased heart rate and breathing, but once they see it is something they do not fear, they can move on. In this case, the person did not run first, and respond with the body reaction and then process the information (like in the James-Lange theory). Neither did the individual see the spider, noticed the increased heart beat and increased breathing, then mentally processed this reaction is caused by fear, therefore I am afraid (cognitive-arousal theory). Instead everything happened all at once. References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
5. Answer The process behind what happens in the brain which causes us to sleep was first discovered by Frederic Bremer, a Belguim neurophysiologist. He discovered sleep was not a passive “winding down” process as previously thought; instead it was actively produced by a mechanism located between the cerveau and encephala isolé transections of the brainstem. Further research was conducted and lesions were placed along the inner core of the brainstem (which contains the medulla oblongata, pons, and midbrain) on the reticular formation (neurons and axons implanted between numerous functionally nuclei) severing the connection to the brainstem from the forebrain, but leaving the sensory connections intact. This caused a deep sleep pattern to form on an EEG, and revealed the importance of the reticular formation site for controlling sleep. The reticular formation controls sleep by controlling the levels of arousal in the brain including the cerebral cortex. Being able to control levels of arousal is how the reticular formation regulates when we sleep, when we awaken, as well as our consciousness. The reticular formation projects to the thalamus hypothalamus as well as the cerebral cortex forming the ascending reticular activation systems, and contains a number of neurotransmitters, including noradrenaline, serotonin and acetylcholine (Wickens, 2009, p. 264). This system regulates sleep and wakefulness. Michel Jouvet discovered another important part of the reticular formation in terms of REM sleep, and that was the pontine region. The pontine region can be found in the upper brainstem. Neurochemicals found in this pathway were noradrenaline and serotonin. The site of noradrenaline located in the pontine region is the locus coeruleus, which is the REM sleep executive, while the serotonin site is called the raphe nuclei, which promotes SWS. Another important region for REM sleep is called the gigantocellular tegmental field (GTF) which is another name for large neurons located in the medial pontine reticular formation. The GTF neurons are controlled by the laterodorsal tegmental nucleus (LTN) and pedunculopontine tegmental nucleus (PTN) (together they are called the peribrachial area), which release acetylcholine in the forebrain. GTF neurons are not very active in SWS or periods when a person is awake, but become very active just before a person reaches REM sleep. The LTN and PTN receive projections from the locus coeruleus, and the raphe nuclei, they in turn project to the GTF, forebrain, thalamus, hypothalamus, and basal forebrain (Wickens, 2009, p. 268). Circadian rhythms are like timing mechanisms (internal clocks) which control when a person sleeps or is awake. The clock is a cycle which operates on a 24- hour timetable with different biological and physiological processes which peak at certain times of the day, and drop really low at other times. Hormones like melatonin (the key factor in modulation of circadian rhythms), growth hormone, cortisol, adrenaline, and testosterone are used to regulate and orchestrate circadian rhythms. Melatonin is released in the evening (under the direct control of light), with the growth hormone peaking in the middle of the night. Cortisol and testosterone are at its highest levels in the morning, with adrenaline reaching its peak in the afternoon. The system itself consists of pacemakers, and pacemaker output to effector systems which are controlled by the circadian. The discovery of the circadian clock was found when two independent research groups discovered a small cluster of neurons located in the front of the hypothalamus. These neurons were called suprachiasmatic nucleus (SCN). SCNs output primarily to the hypothalamus, basil forebrain, and the midline thalamus, and if damaged, could affect or disrupt circadian rhythms as well as affecting the release of corticosterone. The SCN has a pathway to the retinohypothalamic tract, were it terminates in the circadian pacemakers. The retinohypothalamic tract branch off from the optic nerve close to the optic chiasm. Vision is not affected by damage to the retinohypothalamic tract, but “they nevertheless abolished the ability of the internal circadian clock to be synchronized to external light-dark cycles” (Wickens, 2009, p. 276). SNC also sends information to a pathway called the superior cervical ganglion. This pathway inhibits light on the pineal gland which is responsible for secreting melatonin. As mentioned before, melatonin is very important to circadian rhythms. It helps inhibit electrical activity in the SNC resetting its circadian clock. This is important not only in the regulation of the sleep-wake cycle, but also with the synchronization of the other hormones in the sleep-wake cycle. The SNC also extends to the subparaventricular zone of the hypothalamus (SPZ) which is responsible for generating sleep-wake and activity rhythms. Damage to the SPZ can result in the disruption of circadian rhythms, “including-sleep-waking, feeding, locomotor activity, cortisol secretion and neural activity in the locus coeruleus” (Wickens, 2009, p. 281). Two types of abnormal circadian rhythms are jet lag and shift work. References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
6. Answer
Memory is basically stored records of experiences in the brain, with memories being characterized as both short-term or long-term, unique or accrued knowledge, and whether they are expressed explicitly or implicitly. The parts of the brain structure which are important to memory are the prefrontal cortex (responsible for working memory), striatum (responsible for procedural memory), cerebral cortex (responsible for perceptual memory, semantic memory, and priming), the hippocampus (declarative memory), and amygdala (emotional memory). The hippocampus and amygdala are two parts of the limbic system located under the hypothalamus, and near the thalamus, with each being necessary in the memory processes, and both having primary functions which relate to reactions to emotions and memories. The hippocampus controls and regulates how the mind processes new or novel information, and is actively involved in how a person can form associations between newly introduced items, as well as encoding memories. The hippocampal system helps to make associations with the encoded memories which are essential for learning and understanding. “In addition to encoding new information, the hippocampus is also involved in the retrieval of old memories” (Wickens, 2009, p. 347), which in turn assists with successful recall of memory representations. The part of the hippocampus responsible for retrieving learned information is the anterior parts, while the posterior parts encode the information into memory. The amygdala and the hippocampus depend on each other for their individual functions. Reactions to stimuli are controlled by the amygdala, and those responses are used by the hippocampus to form short and long-term memories. “The amygdala and hippocampus co-modulate each other such that the amygdala can influence hippocampally-mediated memory formation and the hippocampus influences amygdala response when emotional stimuli are encountered” (Tottenham & Sheridan, 2010, p. 7). There are also two circuits associated with memory in the brain. The Papez circuit, which is associated with human amnesia, is connected to the hippocampus. Cingulate gyrus projects to the hippocampus, which projects to the mammillary bodies along the fornix pathway, up to the anterior thalamus, which completes the circuit by projecting to the cingulate cortex (Wickens, 2009, p. 352). The second circuit, the Yakovlev circuit is centered on the amygdala. The amygdala sends fibers to the dorsomedial thalamus which has also been associated with amnesia. The dorsomedial thalamus projects to the prefrontal cortex and back to the amygdala which completes the circuit (Wickens, 2009, p. 353).
The hippocampus has also been linked to spatial memory and cognitive mapping. Evidence of this was discovered by John O’Keefe during an experiment where he was recording electrical activity of individual cells in the hippocampus while his test subjects (rats) moved about in their environment. His main findings were identifying certain neurons firing when the rats when to a certain location. He noticed the neurons would remain inactive until the rats went to that certain location and then the cells would fire rapidly. The further away the rat went from that location the less the neurons fired until the firing stopped. When the rat returned the same thing would occur. These neurons became known as place cells. The hippocampal place cells were discovered to be dependent upon cues, and the cells would only fire once the rats reached the certain location they related to a specific cue. Spatial configuration of the cues was vitally important to whether the hippocampal place cells were shown to fire or not. This proved the hippocampus forms a cognitive map of its surroundings. “In other words, when an animal negotiates its environment, it is using a map, continuously formed and updated by the hippocampus, to guide direction and goal location (Wickens, 2009, p. 357).
Another experiment was conducted using a spatial memory task with rats as well. This experiment involved the rats being able to locate a platform in a circular tank of water made cloudy so they could not see in the water. The rats would swim around until they found the platform and climb out of the water. The rats were essentially forced to learn exactly where the platform was by determining its position to the spatial configuration of external cues around the water (Wickens, 2009, p. 358-359). Lesions were placed on the hippocampus of some of the rats and they proved to be unable to locate the platform even after months of testing. This test proved the rats had formed a spatial map of their environment in order to reach the platform, thus showing the importance of the hippocampus in spatial memory.
References:
Tottenham, N. & Sheridan, M. (2010). A Review of Adversity, The Amygdala and the Hippocampus: A Consideration of Developmental Timing. Retrieved on December 2, 2013, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2813726/
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
7. Answer
Language is one of the most unique characteristics human beings have. It is this capability to produce language which separates us from any other animal in the world. Our linguistic capabilities are found in the left hemisphere of the brain in the Broca’s area (found in the frontal lobe) and Wernicke’s area (found in the temporal lobe). Damage to either of these areas can cause aphasia which means to have a complete loss of speech or language, or a disturbance in the production or comprehension of speech following brain damage of specific areas (Wickens, 2009, p. 368). Broca’s aphasia, also known as motor aphasia, or non-fluent aphasia, is characterized by specific language disruption. The language is slow with long pauses in between the words lacking rhythm, intonation and inflection (also known as dysprosody), labored which could lead to frustration, and lacking in grammar (agrammatism) which makes them difficult to understand. Even if the person has an excellent vocabulary, they are reduced to using simple nouns, verbs, and adjectives. They will also find difficulty when searching for the ‘right word’ (anomia) to use in a sentence. The sound of their speech changes as well. Some motor functions affected by this disorder are the inability to stick out the tongue (oral apraxia) if asked to by command, although they are able to lick their lips if something is on them. They also have problems with correct motor movements of the mouth for articulation of speech. This is largely due to the Broca’s area being located adjacent to the motor cortex, close to the area responsible for mouth, tongue, and vocal cord movements. It is expected damage to the Broca’s area would cause destruction of neural circuits needed for movements required for speech production. Although Broca’s aphasics have their cognitive and mental functions unbroken, complex language is difficult for them to process. They are able to understand verbal speech just as long as it remains simple. Reading and writing are also affected with this condition.
Wernicke’s area is located adjacent to the auditory cortex, meaning the information being received from the ears is translated in this area. It translates sounds into codes the brain recognizes as language. It is because of this Wernicke’s aphasia is sometimes referred to as sensory aphasia or receptive aphasia. Wernicke’s aphasia unlike Broca’s aphasia does not inhibit or restrict rhythm and grammar of speech because they recognize speech sounds and have full mobility and function of their motor cortex; instead people who suffer from this condition will often babble or speak in a way in which the words have no meaning. They are able to speak words fluently and can articulate words quickly, and usually respond with words which sound normal and are grammatically correct, yet they are absent of sensible content. They will also use words in which they made up called neologisms, or they will substitute a word for another inappropriate word called paraphasias. The combination of verbal confusion with paraphasias produces a speech called jargon aphasia. One really big difference between Broca’s patients and Wernicke’s patients is the awareness levels of the disorder. Broca’s patients experience the frustration behind knowing what they want to say and not being capable of saying it, and Wernicke’s patients are completely oblivious to their condition. Both conditions are alike in how each of the patients has issues with comprehending complex language, reading and writing. Again simple forms of speech are understood.
The underlying mechanisms of language discovered from these two conditions have become known as the Wernicke-Geschwind model. This model explains first we have to be able to hear spoken language; secondly these words have to be processed by the auditory cortex, proceed to the Wernicke’s area where the information is decoded and comprehended and translated into words. The Wernicke’s area also turns verbal information and translates it into a thought or action. This is where it communicates with surrounding cortex where words are stored with their meanings. The Wernicke’s area then sends information along the arcuate fasciculus to the Broca’s area where movements for speech are located. This pathway was important in terms of language acquisition, particularly in association of words with its meanings and sounds (Wickens, 2009, p. 372).
References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
8. Answer
One of the things all drugs have in common is the direct affect they have on the reward circuit of the brain. The reward or pleasure circuit is activated when the cortex receives information and processes it as stimulus signaling a reward. The signal is sent to the ventral tegmental area (VTA) where the dopaminergic cell activity increases. The dopamine is released to the mesolimbic pathway which projects from the VTA into the nucleus accumbens, septum, amygdala and the prefrontal cortex. All of these components are part of what is known as the reward bundle located in the medial forebrain bundle (MFB). The circuit starts in the MFB influencing dopaminergic activity in the nucleus accumbens by descending pathways to the VTA (Wickens, 2009, p. 454). The nucleus accumbens is the site which holds the most important value for producing rewarding affects in the neural substrate for drugs, it may not be the only area responsible for producing these rewards. For example some opiates do not require dopamine for their rewarding affects, along with alcohol, nicotine, marijuana, and lysergic acid diethylamides. Studies have shown even if the pathways of the VTA are severed the nucleus accumbens the brain can still produce rewarding affects, and it is possible it is receiving information from other pathways. Continued research is being conducted.
Dopamine, which is a neurotransmitter responsible for the pleasure feeling one receives in the rewards system, is the most important neurotransmitter for reinforcement actions in both cocaine and heroin. Normal dopamine function begins in the neuron and vesicles and moves to the neural membrane where it is sent to the synaptic cleft. The dopamine binds to receptor sites on another neuron and begins its reuptake process. The dopamine travels back from the synaptic cleft and into the original neuron by reuptake pumps. When cocaine is taken, it blocks the reuptake pumps keeping dopamine and noradrenaline from re-entering the neuron. Instead cocaine removes the dopamine from the synapse, causing an increased amount of dopamine and noradrenaline to build up in the gap between the synapse and the neuron causing the pleasure people feel. After using cocaine for a certain amount of time, a person will become dependent on the drug to feel normal, because without it their brain does not produce enough dopamine in the synapse, causing the person to feel depressed, tired, or having periods of low mood swings.
Heroin is a class of drugs known as opiates. The main ingredient in these drugs is morphine. Heroin when entered into the body binds to opiate receptors. These opiate receptors are located on neurons which release gamma-aminobutyric acid (GABA – a neurotransmitter which inhibits dopamine), and the binding of the opiate to the opiate receptor blocks GABA from being transmitted. This causes the dopamine in the synaptic cleft to increase significantly causing an intense feeling of pleasure. Just like with the use of cocaine extended use of opiates can cause the brain to develop abnormalities which even after one discontinues using them, their brain will never function the way it did before the use of the drug. Withdrawal from opiates could have a person feeling anxious, irritable, and having low moods as well.
Learning and classical conditioning have been shown to be important in drug tolerance through a process called behavior tolerance. One of the most important factors which can enhance the experience of the drug abuser is the environment in which they take the substance. It was found majority of heroin overdoses occurred when the abuser uses the drug a new location. The environment in which a person is used to taking the drug along with the method in how the drug is taken such as a needle or cocaine carrying case, acts as a signal (conditioned stimulus). This stimulus elicits a conditioned response such as excitement and sweating, which predicts the consumption of the drug in the body. The body eventually gets to a point where the act of taking the drug triggers an anticipated response causing the secretion of the drugs antagonist, which helps to eliminate the drug from the body. This is called compensatory conditioned response. This prevents the person from over-dosing, because the environmental cues help to produce a form of tolerance.
References:
Moyers, B. (2013). Moyers On Addiction: How Drugs Work. Retrieved on December 11, 2013 from http://www.thirteen.org/closetohome/science/html/animations.html
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
9. Answer
Brain scanning technology has definitely changed how we view the brain and has enhanced the understanding of how the brain functions. Before brain scanning equipment was developed, researchers were forced to use dead patients in order to see what areas may have been damaged. Unfortunately in many cases the problem areas were recovering some of its function by the time the doctors were able to view the brain, making it extremely difficult for pathology to be determined. This problem was solved with the inventions of CAT, MRI, PET, and fMRI scans.
Computerized axial tomography (CAT) is a system developed where brain X-rays are mathematically resolved by computer algorithms (Wickens, 2009, p. 390). CAT scans work by using a ray gun to shoot narrow X-ray beams through the brain and around a person’s head. The radiation would be absorbed by the brain and picked up by detectors creating a three-dimensional picture of the brain. These scans are affective in identifying tumors and damaged areas of the brain as a result of a stroke. They can also give doctors a clear view of ventricles which are indicative of brain atrophy and degeneration. Limitations to this technology include limited detail and the inability to discriminate between objects which are less than 5 mm apart.
Magnetic resonance imaging (MRI) provides scientists the opportunity to observe detailed pictures of the brain without injecting the patients with any substances. This technology works using magnetic fields and radio waves which create a three-dimensional image of the brain. It is considered the most superior of the scans because it can distinguish between different types of soft tissues of the brain, is it non-invasive, spatial resolution allows for items to be detected even as small as 1 mm in diameter, it can allow for views of the brain at different angles, and by alternating between magnetic gradients and radio frequency pulse parameters, they can generate images with different atoms or contrast mechanisms (Wickens, 2009, p. 394). Lastly they allow for images to be taken every couple of seconds allowing for different areas of the brain to be viewed in sequential order.
Functional magnetic resonance imaging (fMRI) allows for researchers to see the how blood flows in the brain, as well as the oxygen removal process. This technology works using MRI equipment to scan for changes in the blood oxygenation and deoxygenation from the signals. The images show when the brain is active an increase of oxygen-rich blood goes to that area of the brain which was activated. This shows the activation of different areas of the brain helping researchers to produce mapped areas of the brain involved in mental processes.
Positron emission tomography (PET) allows for brain activity to be examined while it is engaged in a mental activity. Unlike CAT scans which use X-rays, PET scans use short-lasting radioactive substances that radiate positrons, called cyclotron. These substances are injected directly into the blood stream of the person being examined, and the positrons are picked up by a scanner which creates a three-dimensional image of the chemicals distributed into the brain or body. PET scans are able to observe blood flow and this allows for the brain to be examined because activity of the brain is directly proportionate to the level of blood flowing through its regions. Another advantage to this type of scan is colorful visual display from the image produced. This helps with receptor mapping and tracking the activity in the brain.
Fortunately, CAT, MRI, PET, and fMRI scans were created to see pictures of a living brain to examine physiology and site damages. One of the first advantages for neuropsychologist with this new technology is the ability to look at a live active brain in a non-invasive way. This allows for researchers to be in a controlled experimental environment where they can see specific or localized areas of the brain where different processes like recognition, speech, and memory take place. It enables the researchers to study and discover the relations between brain activity and a person’s behavior, without causing any harm to the patient. An example of how brain scanning technology is providing new insights is the creation of a new field of research called cognitive neuroscience. The non-invasive technology is considered an important factor in the experimental studies these scientists conducts. Their purpose is the find explanations behind the mental and cognitive functions which arise from activity in the brain. “Functional imaging allows the scientist to examine just about any mental process, and to record the activation of multiple brain structures during its activity” (Wickens, 2009, p. 395). Scientists are even able to use the observations of the brain activity to determine what cognitive operations a person is performing, giving them the ability to literally “read a person’s mind”.
References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
10. Answer
Abnormal formation and deposition of the amyloid is one of the main implications in the pathogenesis of Alzheimer disease (AD). Amyloid is a fragment of a protein, from a larger 695 amino acid protein called beta-amyloid precursor protein (B-APP), which builds up causing amyloid or senile plaque in the brain. The most defining characteristic of AD is the presence of senile plaque. These structures are shown to be in abundance throughout the cerebral cortex and hippocampus, and sometimes occurring at the striatum, basal ganglia, and thalamus. Accompanying this plaque is neurofibrillary tangles (NFTs), which then leads to neurodegeneration and eventually dementia (due to the dying of cells from the brain). This whole process is called the amyloid cascade theory. B-APP can be cut by enzymes called secretases, and forms two types of amyloids. The first is normal and not toxic, but the second forms insoluble and toxic sheets (senile plaque) which affect the neurons of the brain from its toxicity levels. This form of amyloid (created by faulty B-APP) is responsible for starting the process of events in the amyloid cascade theory. “Although there is evidence that faulty metabolism of the B-APP protein leads to amyloid deposition in the brain, the theory that this initiates neural degeneration in AD is more controversial” (Wickens, 2009, p. 489). For instance, the level of dementia is not directly correlated with the amount of amyloid buildup in the brain. Some forms of degenerative diseases have shown NFTs were present before the amyloid plaque emerged. This has led to two separate debates with one side supporting the NFT theory while the other supports the amyloid theory. In either case, most evidence still points toward amyloid being the most important part in the aetiology of AD, like the fact some individuals have been known to carry mutated B-APP in their DNA making AD a genetic disease (although it is extremely rare).
Mental exercise is proposed as protection from AD. Studies have shown people who were highly intelligent were able to maintain their intellect as the disease progressed. The results from the study showed the people with higher intellect usually had five times the amount of amyloid plaque and NFTs over less educated people, before they developed behavioral signs of AD. The theory behind this phenomenon is that mental exercise helps to build a cognitive reserve, which increases the brains resilience to neural degeneration (Wickens, 2009, p. 494). The implication behind this finding is the more knowledgeable a person is, the heavier and larger the brain becomes, due to an increase in the amount and strength of the brains neural connections. The larger the brain, the more capable it is in remaining functional, even if it lost a couple of neurons. Thus it would take a significant loss of neurons for the person to reach the point where a deficit would occur. People who have higher IQs also used very little effort in performing mental tasks, which was proven with functional imaging of their brain. The images showed less blood flow to the areas of the brain which were performing the task because they did so with ease. The greater the cognitive reserve was associated with the reduced amounts of blood flow, thus making the patients less likely to succumbing to AD. Not only is mental exercise important in providing protection from AD, but physical exercise as well, which implies both nature and nurture can have an effect on a person developing AD. References:
Wickens, A. (2009). Introduction to Biopsychology (3rd edition). Pearson Edition.
