Dear Students!
Welcome to our seminar "Neurodiversity - Scientific Inquiry Into The Persistence of Autism, Schizophrenia, Bipolar Disorder and ADHD".
Our first speaker will be D. Kim Oller, and he will give you an introduction into the topic, our speakers, and some basic aspects of consciousness with respect to these disorders.
You should read the first 3 chapters of "Consciousness and the Brain" by Stanislas DeHaene!
We are looking forward to meeting you at our first seminar!!
cheers
Uli
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ReplyDeleteworks...
DeleteHello! Here are my summaries for the Dehaene readings and the Power et al. paper.
ReplyDeletePower et al. (2013) Summary
Power et al. identify several reasons why these mental disorders might persist in the population despite being under negative selection pressure. The first reason, known as the Common Disorder-Common Variants Hypothesis ,posits that mental disorders are partially caused by the interaction of many different genes that are not necessarily deleterious to fitness on their own. The combined effect of these genes may cause traits that reduce fitness, but individual genes continue in the gene-pool because they are wide-spread across the population and only lead to negative selection pressure when they converge in relatively small numbers of individuals. Another reason why some mental disorders persist is because the genes that are associated with them arise in "de novo" mutations (e.g. reduced sperm quality and potential mutations associated with older fathers—a risk factor for autism). These genes may be under negative selection and disappear when they are not passed on, but they persist because they keep getting introduced into the gene pool through de novo mutations. Another intriguing possibility, is that certain genes may lower the chance of reproductive success in some individuals but increase the chance in others. An example of this can be found in sexual antagonism, where certain traits benefit one sex while they harm or remain neutral in another sex. A non sex-specific mechanism could also be explained by the fact that many mental disorders exist on a continuum, where an extreme manifestation of a trait is deleterious but a more moderate manifestation may be beneficial (e.g. creativity and schizophrenia, risk-taking and substance abuse, etc.).
The authors’s results show that most disorders negatively affect the fecundity of men to a greater degree than females. They posit that this could be explained by methodological weaknesses in the study and the fact that in general, females can afford to be choosier than males when looking for a mate. The authors interpret sex-differences in between disorders like schizophrenia and autism are likely explained by these factors, but persist due to de novo mutations. Their results indicate a slightly greater fecundity rate in siblings of people with disorders like depression and substance abuse. The genes implicated in these conditions may be beneficial in some environments but harmful in others—a plausible explanation for why these genes persist.
Questions/Comments:
* Birth rates vs sexual activity? Until more recent times, increased sexual activity almost always implied increased fecundity. However, given modern birth control and more conscious family planning, it may be possible that traits that make a partner more sexually desirable (as selected through many generations) don’t necessarily imply reproductive success?
* I’m personally inclined towards to believe that disorders persist due to a combination of reasons that include de novo mutations and heterogeneous genetic pathways that interact with the environment to create negative, positive, or neutral selection pressure. The notion of unbalanced selection pressures and sexual antagonism is certainly plausible and interesting, but I am not convinced by the data that this is the case.
Dehaene Summaries
ReplyDeleteChapter 4: Signatures of a Conscious Thought
Dehaene argues that reliable neural signatures of consciousness can be identified by pairing neuroimaging techniques with paradigms that elicit reliable differences between subjective reports of conscious awareness. He reports that functional imaging has identified areas in the prefrontal and parietal cortices as important to conscious awareness. Dehaene posits that activation in these areas reflects long distance connections that make a conscious percept or thought globally available for conscious processing. For Dehaene, conscious awareness is the result of a cumulative process of network activations that reach a critical trigger point and activate a global web of neurons that fires at a slow and steady rate—creating a stabilized, long lasting representation that is perceived consciously and available to working memory. Dehaene notes that the key difference between conscious and non-conscious network activations is time and intensity. If subliminal networks are stimulated for only a short period of time or low intensity, their spreading activation will fizzle out before reaching conscious awareness. However, if the activations are intense or long enough, they can trigger activation of the “neural web” and sustain prolonged activation through long-distance neural feedback loops. A key electrophysiological correlates of this phenomenon is found in the P3 wave. Experimental data confirms that stimuli in unconscious trials fizzles out before it is able to trigger a P3 wave, whereas conscious trials always trigger the wave. Furthermore, the amplitude and length of the P3 wave is correlated to the intensity and duration of the stimuli that triggered it.
Chapter 5: Theorizing Consciousness
In this chapter Dehaene presents the Global Workspace Theory of Consciousness and offers evidence from computational modeling as an explanatory mechanism for how conscious awareness can account for neural correlates from experimental studies.
In the Global Workspace Theory a conscious state is a stable activation of neural feedback loops that encode a particular thought or object of awareness. These representations gain stability (and longevity in the global workspace) through a process of excitatory and inhibitory feedback loops that amplifies the neuronal networks that encode the salient features in the object of awareness and inhibits all irrelevant features. Conscious awareness is not limited to to the bottom-up processing of external inputs. Spontaneous and random activity in higher order networks can trigger conscious awareness of representations and memories without external stimuli. This randomness and noise in the neural workspace, can explain the autonomous and exploratory nature of animals. It also allows for unique problem solving algorithms that require random noise.
Chapter 6: The Ultimate Test
ReplyDeleteIn this chapter Dehaene argues that neural signatures of consciousness coupled with “global workspace theory” have clinical applications that can improve the lives of people with neurological injuries. Specifically, neuroimaging techniques and clever experimental paradigms can be used to reliably distinguish between patients who are in an unconscious state and those that are suffering from locked-in syndrome. Electroencephalography is particular useful as it is portable and not cost-prohibitive when compared to other techniques like fMRI or PET. Dehaene reports on a study that has shows that conscious awareness can be be identified by comparing mismatch-negativity and P3 waves in an odd-ball paradigm with pattern recognition. Individuals who are conscious exhibit a P3 wave when long sequences of tones differ from sequence to sequence, whereas the MNN response is triggered for tone differences within a sequence. Dehaene argues that these findings make sense in the context of “global workspace theory”. Conscious awareness requires individuals to analyze an entire sequences of tones as a discrete mental object, whereas pre-conscious processing of stimuli is limited to shorter stimuli. Dehaene further claims that “global workspace theory” can be used to aid in the recovery of unconscious patients. He presents clinical evidence that shows that stimulating brain networks in ways that are consistent with “global workspace theory” is able to improve recovery and in some cases temporarily elicit semi-conscious or conscious states.
Chapter 7: The Future of Consciousness
Dehaene concludes his book by addressing practical and philosophical implications of the global workspace theory of consciousness. He presents evidence supporting the claim human infants already exhibit key signatures of conscious awareness. However, these signatures are slow and delayed when compared to adults—he attributes this to immaturity and incomplete myelination of key neural pathways. He further argues that most animals exhibit signatures of conscious awareness that are similar to human’s. Dehaene claims that a key difference between animal consciousness and human consciousness is that human’s appear to be unique in the ability to package objects of conscious awareness into symbolic representations that can be reflected upon abstractly. Furthermore, humans have disproportionately larger and more connected pre-frontal cortices when compared to our primate cousins and other mammals who have markedly less dense dendritic branching in these areas.
Dehaene shows how the global workspace theory can help explain symptoms in psychiatric disorders such as schizophrenia and neurological conditions like multiple sclerosis. Dehaene also speculates that it may soon be possible to create computers that are consciously aware.
He concludes by addressing critics that insist that the global workspace theory still can’t account for notions such as qualia, free will, and autonomy. For Dehaene these problems are definitional and result from ill-defined notions of consciousness. He claims that randomness and self-sustaining thought continuity in pursuit of goals as accounted for in global workspace theory adequately refutes the claims of nay-sayers.
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ReplyDeletePower et al. (2013)
DeleteThe results of this article suggest that patients with psychiatric disorders have significantly fewer children than those without. I did not find these results particularly surprising, even the reduced fitness differences between the groups. However, the findings amongst the siblings was surprising. This got me thinking about natural selection in the scope of the course. Could it be that natural selection accounts for neurodiversity by creating a reduction in fecundity? I really think that this article does a good job of touching on this idea. If those affected do not pass on their genetic information to offspring, the disorders cannot be propagated within the species. At the core of our existence, we are still animals with a drive to reproduce. Moreover, we want reproduction of the fittest. Power et al. (2013) suggests that there are many factors within our evolutionary system that may provide some understanding of psychiatric disorders, why they still exist, and the strong negative selection pressures to weed them out. Why do some disorders have a stronger negative selection pressure than others? Does the severity of the disorder or functionality of the affected have anything to do with the level of the selection pressure? For example, the results of this study showed that bipolar disorder did not have as strong of a negative selection pressure as the others when the disorder presented without other illnesses.
Dehaene (2014)
I found some of the reading for this week out of Dehaene overwhelming at times. It is very interesting but also a lot to consider when thinking about the topic. In Chapter 4, it is difficult to imagine the late onset of events in our conscious compared to the actual time they happen. Though only slightly after a stimulus, consciousness appears to lag behind “real-time.” There is this level of processing that occurs so quickly in our unconscious that we often do not even notice it. I liked the example Dehaene (2014) gives for an instance we might become aware of this phenomenon such as if we were to drop a glass of milk. We see it falling almost as if in slow motion but we do not have time to react. In that instance, our consciousness “gropes hopelessly behind the event.” However, the brain does have mechanisms in place to compensate for delays in conscious access. Dehaene lists these mechanisms as the unconscious “auto-pilot” and anticipation. Until reading this chapter, I really did not think about what role these mechanisms play in thinking. The unconscious can tap into sensory and motor reflexes while anticipation uses predictable sequences of events to perceive onsets.
What does young consciousness look like? Is it hard wired or does it take time to sharpen the skill of conscious access? What kicks it on and when? Could it be that vocal and gestural exploration are simply fact storing activities for the child? The infant is becoming aware not only what they are capable of producing, but also storing information on what is being produced by others. In Chapter 5, the concept of the global workspace made me think of how infants use it which Dehaene touches on in the final chapter of the book. If a person needs consciousness to store information long after the information is presented, it seems plausible that infants do this with everything in the environment, especially language and even gesture. This would imply that all of the noises being made by an infant are anything but arbitrary even in the very beginning. Dehaene suggests that conscious awareness is present during infancy but simply immature. I think his explanation suggests that consciousness is both hard wired and a skill that has to sharpened over time. The young brain is still developing and fine tuning its neural pathways as a global workspace is being built.
Other Dehaene Questions:
What does this all mean for mental health? Will pinpointing the neural causes of psychiatric/psychological disorders provide new treatments? How do these disorders present in the conscious and unconscious mind?
Summary for Power et al. (2013)
ReplyDeleteThe authors in this article examine fecundity of patients with psychiatric disorders against their unaffected siblings. Various hypotheses are discussed to identify as to why there persists genetic variations which lowers the reproductive ability of an individual. One of the widely used hypothesis ‘common disorder-common variants’ speculates occurrence of psychiatric disorders to be directly proportional to the frequency of the low-risk allele. Although, only schizophrenia falls in CD-CV hypothesis as a psychiatric disorder, it helps in explaining the influence and the consequential effect of each variant on the disease phenotype. Another hypothesis states that increased paternal age is directly related to the psychiatric disorders which is caused by the de novo mutation. Also, among all the proposed hypotheses, de novo mutation causes greatest decrease in the fecundity among affected individuals as it directly affects the sperm quality. Another hypothesis on the flipside states different mechanisms are introduced for maintaining the equilibrium in selection procedure. Same hypothesis also implies that while existence of deleterious genes results in negative selection, they also provide some beneficial trade offs in areas such as creativity, attention to detail etc. The test was conducted on cohort of individuals diagnosed with one or more psychiatric disorder from a total of six. Outcome of the test indicated that men are affected more with lower fertility ratio as compared to women. Another point to note is that the results of the test were also greatly affected by socioeconomic factors, paternal and maternal education levels. With the inclusion of comorbidity, there were differences in the fecundity in siblings, more notability on women. Although type of comorbidity was not specified but patients suffering from depression and substance abuse displayed higher fecundity among all other disorders. Results of this test cannot be taken as an absolute measure for fertility rates among patients with psychiatric disorders because there were several other factors which could have led to a decrease in the fecundity of an individual such as medications, sterilization etc. as mentioned in the article.
Chapter 5
In chapter 5, John Selfridge visualizes brain as a system which runs daemons on a hierarchical basis. Daemon in computing means a process which is running in the background and the user has no control over it. It essentially manages the applications it is related to without the need for intervention from the user. Also, according to the Selfridge’s proposed model, each daemon ‘yells’ their own interpretation of an incoming image. So, can it ever happen that one of the supposed daemon stops responding? What do we perceive in that situation? Is there another daemon for backup in case the existing one fails?
Chapter 6
Chapter 6 discusses about the presence of consciousness while in coma. Studies have shown people are able to exhibit minimal level of consciousness while being in an unresponsive state. Although there is no clear indication as to how the consciousness is triggered in person who is in coma or ‘vegetative state’. Workspace theory if proven correct could lead to a major breakthrough in helping blind people. We can directly auto simulate and render the image to be and send it to visual cortex for further enhancement.
Power et al (2013)
ReplyDeleteThis study examined the fecundity (i.e., reproductive fitness) of patients with one (or more) of several specified disorders as well as their unaffected siblings to evaluate the degree of selection pressures on these genetic variants. For nearly all of the disorders examined in this study, affected patients had significantly fewer children compared to the general population after correcting for year, disorder comorbidity, and SES. This effect was more common among men than women. Siblings analyses revealed that siblings of patients with depression and substance abuse had significantly increased fecundity. Fecundity in sisters of patients with schizophrenia and bipolar disorder was increased, though not to the degree of counteracting decreased fecundity in their affected siblings, while brothers of patients of schizophrenia and autism showed reduced fecundity relative to the general population. To the credit of these researchers, the database used in this study contained information on >2,000,000 individuals, including between 2,947-81,295 people for each disorder population. This provided a large sample for analyses and lends great support for the conclusions reached in the article. However, it is not clear in this article whether corrections were made for premature deaths in patient populations (e.g. suicide, accidental deaths) that may be higher in these populations (e.g. higher risk of suicide in people with depression) and would result in lower birth rates. Additionally, it is unclear from this study how the use of contraceptives may have influenced the fecundity measure—condoms were widely available at this time, and oral birth control was rising in popularity through the 60’s, during the time window of the database used here.
Ch. 4
Dehaene describes four primary signatures of consciousness based on scientific evidence in this chapter. (1) Neural activity is amplified after a threshold of awareness is crossed, producing a “sudden ignition” of parietal and prefrontal circuits. This “avalanche” of activity is a non-linear response to stimulus changes (i.e., all-or-none response), appears to pick up strength as it progresses forward into the cortex, and becomes self-reinforcing, a term he calls “global ignition.” This increase in neural synchrony of distant brain regions for conscious targets is an important factor for consciousness. (2) EEG experiments show conscious awareness to be strongly correlated with P3 activation. The attentional blink phenomenon described in Ch. 1 is correlated with timing of first P3 wave relative to second presentation of a target (concentrating on first prevents from seeing the second). Consciousness therefore lags behind current time by ~1/3 sec. (3) Invasive techniques show late, sudden bursts of neural oscillations (gamma band) that are associated with conscious awareness. Additionally, individual neurons can track conscious percepts almost to the point where a number of neural spikes can predict conscious awareness of an object associated with that neuron. However, individual cells do not suffice to induce a conscious thought. (4) Consciousness requires synchronization of information exchanges across distant brain regions via neural networks. This synchronization appears to be bidirectional in nature across the cortex, forming a “global web”. Ultimately, our conscious experiences result from the activity of massive cerebral circuits with reproducible neuronal signatures.
Ch. 5
DeleteThis chapter sets up Dehaene’s theory of consciousness through what he calls the “global neuronal workspace” hypothesis. He describes how the global workspace processes and integrates information from several systems including attentional, perceptual, evaluative, and long-term memory systems that can produce a motor system output. In order to be consciously accessible, information must be encoded as an organized pattern of neural activity that, in turn, sparks activity of the global workspace—this “global ignition” observed in the parietal and prefrontal cortices. He attributes this global workspace to a dense network of interconnected brain regions (not simply one region of the brain), possibly engineered by pyramidal neurons in cortical layers II and III that possess long axons interconnecting distant regions. Neural network modeling approaches of cortical columns appear to show the four characteristics of consciousness described in the previous chapter, and they reveal how spontaneous neuronal activity is not only essential for global ignition of near-threshold stimuli, but also for Darwinian processes of brain development and evolution of the species.
Ch. 6
This chapter summarized investigations of consciousness in patients of comatose, vegetative, minimally conscious, anesthetic, and sleep states. The spectrum of apparent conscious states is matched, to some degree, by levels of neural activity as measured by EEG or fMRI that reflects these states. However, as in the case of locked-in syndrome, EEG signatures of some patients mirrored those of conscious individuals, and brain measures revealed traces of consciousness undetected by some clinicians. These findings have important implications in clinical identification of consciousness and possible interventions for bringing a patient out of a vegetative state into a more conscious one.
Ch. 7
The final chapter of Dehaene’s book explores signatures of consciousness found in babies, macaques, dolphins, rats, and other mammals. He states that conscious access exists in babies but in a dramatically slower form than adults, attributed to the reduced myelination and maturation of cortical neurons. Additionally, experiments with animals such as dolphins and rats indicate some decree of self-knowledge (e.g. calculating which combination of lever presses produces the greatest reward) which Dehaene argues cannot exist without a conscious neuronal workspace. Consciousness, he writes, initially evolved as a communication device, but in humans alone, this power of communication evolved to a “language of thought” that allows us “to formulate sophisticated believes and to share them with others.” Consciousness can also characterize disorders such as schizophrenia in which patients demonstrate a deficit of conscious perception and a range of symptoms that may be due to a reduction of top-down messages from impaired long-distance connections or dysfunctional NMDA receptors.
Dehaene questions: The NMDA receptor has also been a target for treatment in disorders such as major depressive disorder and bipolar disorder, yet these individuals do not show schizophrenic symptoms of hallucinations, paranoia, etc. If the NMDA receptor is integral for a functional global workspace, would these disorders also show differences of neural activity according to Dehaene’s measures of consciousness? If so, could these patterns of consciousness be used to track progression of treatment in some of these disorders?
Jessica Yoo
ReplyDeleteIn chapter 4, Dehaene discusses how brain-imaging techniques such as fMRI, EEG, and MEG, have helped with studies in consciousness. He states that the activations in regions in the parietal and frontal lobes were strongly connected to consciousness. Looking at the amplification can distinguish consciousness from unconsciousness, in which P3 wave will show for consciousness, but remain absent for unconsciousness. Also, contrary to previous studies, Dehaene argues that Gamma waves at 40 Hz appears for both consciousness and unconsciousness stages, but intensity is higher for consciousness. Dehaene also talks about our consciousness lagging behind unexpected events with the example of hitting the car brakes slower when our mind is distracted when driving. Most of the times it goes unnoticed, but our awareness falls behind the real time. Consciousness takes time for processing.
In chapter 5, he explains his hypothesis of “global neuronal workspace” to answer the question of why consciousness occurs. He proposes that when the stimulus/information is conscious, it can ‘spread’ to other area of the brain that is related to our purpose for that moment. Brain shares information to make use of consciousness and this was explained through the example of pyramidal neurons that makes long-distance communication possible.. We are able to hold the information in our minds after it becomes conscious and use it however we please to, such as storing in our long-term memory. Dehaene also proposes 5 labels for ways in which neural information can remain unconscious (unconscious representation): preconscious state, subliminal state, disconnected patterns, diluted state, dormant state.
In chapter 6, Dehaene discusses how the theory of consciousness translates into clinical applications, such as patients in coma. With various technology such as fMRI, EEG, and brain-computer interfaces, we are able to gain insight into the conscious state of mind of the patient. Patients in coma still has active brain and generates EEG, but are unable to “wake up” from unconsciousness. With less costly EEG methods and brain-computer interfaces, Dehaene states that this way may be the most practical research method. He developed a simple consciousness test that uses an oddball paradigm producing a pure P3 waves without the presence of earlier unconscious responses, and from this we are able to determine that the patient’s awareness present. He also suggests developing a complete battery of tests that determines the conscious state of a clinical patient is much needed.
In the final chapter 7, Dehaene addresses challenges associated with consciousness in babies and animals. When do they become conscious? With more findings, are we able to give consciousness to artificial intelligence? He explains that the reason the signatures of consciousness are slower in infants may be due to incomplete establishment of their myelin. Babies can score high on a test of consciousness, but will still show much slower brain-response latency compared to adults. Compared to animals, what makes human unique is that we have the “recursive function of human language” that we can use to express our thoughts. He also continues to elaborate on the possibilities of algorithm of consciousness which can be translated from our biological machinery to artificial machinery to create artificial consciousness. For this, wider communication network of machinery processes are required.
--I realized that the previous reply showed to be in a disorganized format without the spaces between each paragraphs, so I am uploading a new comment including the Power (2013) article.
Delete[Dehaene]
In chapter 4, Dehaene discusses how brain-imaging techniques such as fMRI, EEG, and MEG, have helped with studies in consciousness. He states that the activations in regions in the parietal and frontal lobes were strongly connected to consciousness. Looking at the amplification can distinguish consciousness from unconsciousness, in which P3 wave will show for consciousness, but remain absent for unconsciousness. Also, contrary to previous studies, Dehaene argues that Gamma waves at 40 Hz appears for both consciousness and unconsciousness stages, but intensity is higher for consciousness. Dehaene also talks about our consciousness lagging behind unexpected events with the example of hitting the car brakes slower when our mind is distracted when driving. Most of the times it goes unnoticed, but our awareness falls behind the real time. Consciousness takes time for processing.
In chapter 5, he explains his hypothesis of “global neuronal workspace” to answer the question of why consciousness occurs. He proposes that when the stimulus/information is conscious, it can ‘spread’ to other area of the brain that is related to our purpose for that moment. Brain shares information to make use of consciousness and this was explained through the example of pyramidal neurons that makes long-distance communication possible.. We are able to hold the information in our minds after it becomes conscious and use it however we please to, such as storing in our long-term memory. Dehaene also proposes 5 labels for ways in which neural information can remain unconscious (unconscious representation): preconscious state, subliminal state, disconnected patterns, diluted state, dormant state.
This comment has been removed by the author.
DeleteIn chapter 6, Dehaene discusses how the theory of consciousness translates into clinical applications, such as patients in coma. With various technology such as fMRI, EEG, and brain-computer interfaces, we are able to gain insight into the conscious state of mind of the patient. Patients in coma still has active brain and generates EEG, but are unable to “wake up” from unconsciousness. With less costly EEG methods and brain-computer interfaces, Dehaene states that this way may be the most practical research method. He developed a simple consciousness test that uses an oddball paradigm producing a pure P3 waves without the presence of earlier unconscious responses, and from this we are able to determine that the patient’s awareness present. He also suggests developing a complete battery of tests that determines the conscious state of a clinical patient is much needed.
DeleteIn the final chapter 7, Dehaene addresses challenges associated with consciousness in babies and animals. When do they become conscious? With more findings, are we able to give consciousness to artificial intelligence? He explains that the reason the signatures of consciousness are slower in infants may be due to incomplete establishment of their myelin. Babies can score high on a test of consciousness, but will still show much slower brain-response latency compared to adults. Compared to animals, what makes human unique is that we have the “recursive function of human language” that we can use to express our thoughts. He also continues to elaborate on the possibilities of algorithm of consciousness which can be translated from our biological machinery to artificial machinery to create artificial consciousness. For this, wider communication network of machinery processes is required.
[Power et al. (2013)]
The article explores the reproductive aptness for patients with schizophrenia, autism, bipolar disorder, etc, and their siblings. It seems that psychiatric disorders have gone against the evolutionary view that supposedly filter out genetic variants. It has been researched that at least for psychosis, fecundity in siblings of schizophrenic patients did not increase. Through the measurement of the fecundity, the results showed that except women with depression, patients with these disorders displayed to have significant effect of lower fecundity, in which the effect was stronger for men. The gender difference outcome was consistent with siblings. Power indicated several possible reasons for changes in fecundity compared to previous generation’s fitness. Biological and physiological difference such as reduced sperm count and ‘inability’ in psychiatric disorder patients to attract a partner. He further compares the ‘the investment’ in men and women through the example of the cost of sperm production versus 9 months of pregnancy, which enables women to be much more selective of men that creates more burden for men. Out of all disorders in the article, autism had the highest fecundity reduction and the pattern was similar to schizophrenic patients, which may be due to sexual conflict. Bipolar disorder’s fecundity showed to be higher, as well as among siblings. The article states that this may be a result of lithium treatment that improves functioning. The reason for depression being the oddball and not showing difference in fecundity is that depression may be highly dependent on environmental influences compared to any other disorders. Anorexia nervosa showed fecundity decrease but no effect in siblings, while substance abuse also showed a decrease in fecundity but increase in siblings. However, there still remains unaddressed possible factors that affected the results of fecundity rate, such degree of each disorders, social status, and interaction factors (example: some may have both bipolar disorder and anorexia nervosa).
Ch. 4 - The Signatures of a Conscious Thought
ReplyDeleteDehaene describes in detail the works of numerous investigators who have collectively illuminated many questions related to unconscious and conscious processes within humans and other animals. His thoroughness in providing studies that utilize a variety of methodologies and stimulus paradigms allows for a significant reduction in potential alternative explanations for the observed and reported findings. Based on the outcomes of these studies, Dehaene suggests that there are 4 signatures of conscious thought including: widespread activation within parietal and prefrontal regions, a positive deflection approximately 300 ms following the presentation of a stimulus (P3), high-frequency gamma oscillations sustained at higher amplitudes for greater durations (at least 300 ms following stimulus presentation), and synchronous activation between brain regions distant from primary sensory cortices forming "brain webs" allowing for the creation of a loop for the passing of information. Dehaene describes this synchronous activation as "global ignition."
Ch. 5 - Theorizing Consciousness
Dehaene describes his hypothesis of "global neuronal workspace" in order to link subjective conscious experiences to obtained results from neuroimaging and other objective measurements. This global workspace was likened to a broadcasting system in which information is transferred between modules, or groups of specialized neurons, to fulfill a particular purpose. It is this transfer between modules which enables the brain to selectively send information to regions for specialized processing depending on our intended purposes for that information. This theory appears to successfully capture the complexities of conscious access as well as provide possible explanations for why some information remained inaccessible to conscious awareness.
Ch. 6 - The Ultimate Test
DeleteIn this chapter, Dehaene applies his previously established signatures of consciousness as well as his theory of global neuronal workspace to evaluate the consciousness of patients in a coma and vegetative states. Using creative methods, it is revealed that the degree of consciousness in these patients may be revealed using the signatures of consciousness. Interestingly, the majority of those who demonstrated some level of consciousness experienced better clinical outcomes. Further investigation revealed that some degree of consciousness may be recovered in individuals with limited activation between the thalamic and cortical regions and intact prefrontal regions utilizing deep brain stimulation.
Ch. 7 - The Future of Consciousness
Dehaene discusses the possible future directions of research in consciousness in this final chapter. He specifically addresses the topics of consciousness in development in human infants and animals. He further posits that given the significant advances in objective measurement of consciousness the creation of "conscious" machines utilizing a global workspace is not as far-fetched as some might believe. It seems that while significant advances have been made in the study of consciousness a great deal is yet to be discovered.
Power et al.
Based on evolutionary theory, one would believe that psychiatric disorders would demonstrate a sort of negative selection process in reproduction. Despite this theoretical standpoint, these disorders widely persist in the population, and few studies have investigated the reproductive ability of these individuals to evaluate the selection of these seemingly less desired traits. The researchers' findings suggest that there is a stronger negative selection for particular disorders over others specifically for schizophrenia, autism, and anorexia nervosa. However, fertility ratios did not differ from the general population as greatly for individuals affected by depression, bipolar disorder, or substance abuse. Additionally, sex differences were observed which suggest that males' reproductive fitness may be more negatively influenced than females. These findings lead to the conclusion that there are innately different underlying mechanisms influencing the persistence of these disorders.
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ReplyDeletePower et al.
DeleteThe research focuses on determining the individual’s ability to reproduction of patients with psychiatric disorders vs. their unaffected siblings. The experiments occurred in 2.3 million participants in Sweden. The research results showed that there is a strong selection against schizophrenia, autism, and anorexia nervosa based on genetic variants which seem to be removed from the population. Among disorders, affected female had a consistently greater increase in fecundity than affected male e.g. sisters of individuals with psychiatric disorders had more children than their brothers. Also, sex-specific effect suggests that finding results maybe favored by psychiatric morbidity impairs interest or ability to find suitable mating partners or inhibits biological fertility to a greater extent in men. Due to the greater variability in male fitness and the pressure on females to be selective, a genetic or environmental burden can have an exaggerated effect on a male’s ability to find a mate. However, at this stage the research could not bring up any evidence why siblings of individuals with depression or substance abuse would have increased fitness, and the observation could result from shared environmental factors uncorrected for in this analysis.
Chapter 4:
ReplyDeleteFour reliable signatures of consciousness —physiological markers that index whether the participant experienced a conscious percept. (1) A conscious stimulus causes an intense neuronal activation that leads to a sudden ignition of parietal and prefrontal circuits. (2) In the EEG, conscious access is accompanied by a slow wave called the P3 wave, which emerges as late as one-third of a second after the stimulus. (3) Conscious ignition also triggers a late and sudden burst of high-frequency oscillations. (4) Many regions exchange bidirectional and synchronized messages over long distances in the cortex, thus forming a global brain web.
Chapter 5:
A global neuronal workspace explains observations about consciousness and brain mechanisms. It also explains why we become aware of only a scrawny portion of the knowledge stored in our brains. In order to be accessible, information must be encoded as an organized pattern of neuronal activity in higher cortical regions, and this pattern must, in turn, ignite an inner circle of tightly interconnected areas forming a global workspace. Such complex computations can be performed by a neutral network model. With specialized neurons, elementary perceptual decisions arise through the accumulation of the noisy evidence. However, the current simulations could not completely depict how brain states cause our conscious experience.
Chapter 6:
Theory of consciousness have been tested in the clinic with patients in coma and other brain states. The test objectives is trying to answer whether the science of consciousness can help thousands of individuals every year falling into a coma, many of them remain in a vegetative state. Based on analysis of brain signals, the research starts categorizing patients to whether they retain a conscious life or not. Some results showed that with brain-computer interfaces can restore some forms of communication on fully paralyzed patients.
Chapter 7:
The future directions of emerging science of consciousness have been discussed. Several questioning challenges have been addressed: whether an existence of consciousness in babies, or animals? The author showed different approaches not only on studying human fetus or animal anatomy but also on behavior or combined with visual illusion. He also envisioned a computer with the conception of free will, an artificial device capable of willfully deciding on its course of action.