visual-perception.ga

Visual perception is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment. This is different from visual acuity which refers to how clearly a person sees (for example “20/20 vision”). A person can have problem with visual perceptual processing even if he/she has 20/20 vision.

The resulting perception is also known as visual perception, eyesight, sight, or vision (adjectival form: visual, optical, or ocular). The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in linguistics, psychology, cognitive science, neuroscience, and molecular biology, collectively referred to as vision science.

auditory-perception.ga

The primary auditory cortex is the part of the temporal lobe that processes auditory information in humans and other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to language switching.[1][2]

It is located bilaterally, roughly at the upper sides of the temporal lobes – in humans on the superior temporal plane, within the lateral fissure and comprising parts of Heschl’s gyrus and the superior temporal gyrus, including planum polare and planum temporale (roughly Brodmann areas 41, 42, and partially 22).[3][4] Unilateral destruction, in a region of the auditory pathway above the cochlear nucleus, results in slight hearing loss, whereas bilateral destruction results in cortical deafness.

bistable.tk

In a dynamical system, bistability means the system has two stable equilibrium states.[1] Something that is bistable can be resting in either of two states. These rest states need not be symmetric with respect to stored energy. An example of a mechanical device which is bistable is a light switch. The switch lever is designed to rest in the “on” or “off” position, but not between the two. Bistable behavior can occur in mechanical linkages, electronic circuits, nonlinear optical systems, chemical reactions, and physiological and biological systems.

In a conservative force field, bistability stems from the fact that the potential energy has two local minima, which are the stable equilibrium points.[2] By mathematical arguments, a local maximum, an unstable equilibrium point, must lie between the two minima. At rest, a particle will be in one of the minimum equilibrium positions, because that corresponds to the state of lowest energy. The maximum can be visualized as a barrier between them.

A system can transition from one state of minimal energy to the other if it is given enough activation energy to penetrate the barrier (compare activation energy and Arrhenius equation for the chemical case). After the barrier has been reached, the system will relax into the other minimum state in a time called the relaxation time.

Bistability is widely used in digital electronics devices to store binary data. It is the essential characteristic of the flip-flop, a circuit widely used in latches and some types of semiconductor memory. A bistable device can store one bit of binary data, with one state representing a “0” and the other state a “1”. It is also used in relaxation oscillators, multivibrators, and the Schmitt trigger. Optical bistability is an attribute of certain optical devices where two resonant transmissions states are possible and stable, dependent on the input. Bistability can also arise in biochemical systems, where it creates digital, switch-like outputs from the constituent chemical concentrations and activities. It is often associated with hysteresis in such systems.

perceptual-illusions.ga

An optical illusion (also called a visual illusion[2]) is an illusion caused by the visual system and characterized by a visual percept that (loosely said) appears to differ from reality. Illusions come in a wide variety; their categorization is difficult because the underlying cause is often not clear[3] but a classification[1][4] proposed by Richard Gregory is useful as an orientation. According to that, there are three main classes: physical, physiological, and cognitive illusions, and in each class there are four kinds: Ambiguities, distortions, paradoxes, and fictions. A classical example for a physical distortion would be the apparent bending of a stick half immerged in water; an example for a physiological paradox is the motion aftereffect (where despite movement position remains unchanged). An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion. Physical illusions are caused by the physical environment, e.g. by the optical properties of water. Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type. Cognitive visual illusions are the result of unconscious inferences and are perhaps those most widely known.

Pathological visual illusions arise from pathological changes in the physiological visual perception mechanisms causing the aforementioned types of illusions; they are discussed e.g. under visual hallucinations.

cognitive-illusions.ga

An illusion is a distortion of the senses, which can reveal how the human brain normally organizes and interprets sensory stimulation. Though illusions distort our perception of reality, they are generally shared by most people.[1]

Illusions may occur with any of the human senses, but visual illusions (optical illusions) are the best-known and understood. The emphasis on visual illusions occurs because vision often dominates the other senses. For example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words.[2]

Some illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles (e.g., Gestalt theory), an individual’s capacity for depth perception and motion perception, and perceptual constancy. Other illusions occur because of biological sensory structures within the human body or conditions outside the body within one’s physical environment.

The term illusion refers to a specific form of sensory distortion. Unlike a hallucination, which is a distortion in the absence of a stimulus, an illusion describes a misinterpretation of a true sensation. For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water (or other auditory source) would be an illusion.

statistical-illusions.ga

Statistics are supposed to make something easier to understand but when used in a misleading fashion can trick the casual observer into believing something other than what the data shows. That is, a misuse of statistics occurs when a statistical argument asserts a falsehood. In some cases, the misuse may be accidental. In others, it is purposeful and for the gain of the perpetrator. When the statistical reason involved is false or misapplied, this constitutes a statistical fallacy.

The false statistics trap can be quite damaging for the quest for knowledge. For example, in medical science, correcting a falsehood may take decades and cost lives.

Misuses can be easy to fall into. Professional scientists, even mathematicians and professional statisticians, can be fooled by even some simple methods, even if they are careful to check everything. Scientists have been known to fool themselves with statistics due to lack of knowledge of probability theory and lack of standardization of their tests.

prefrontal-cortex.ga

In mammalian brain anatomy, the prefrontal cortex (PFC) is the cerebral cortex which covers the front part of the frontal lobe. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46, and BA47.[1]

Many authors have indicated an integral link between a person’s will to live, personality, and the functions of the prefrontal cortex.[2] This brain region has been implicated in planning complex cognitive behavior, personality expression, decision making, and moderating social behavior.[3] The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals.[4]

The most typical psychological term for functions carried out by the prefrontal cortex area is executive function. Executive function relates to abilities to differentiate among conflicting thoughts, determine good and bad, better and best, same and different, future consequences of current activities, working toward a defined goal, prediction of outcomes, expectation based on actions, and social “control” (the ability to suppress urges that, if not suppressed, could lead to socially unacceptable outcomes).

The frontal cortex supports concrete rule learning. More anterior regions along the rostro-caudal axis of frontal cortex support rule learning at higher levels of abstraction.[5]

amygdala-fear.ml

The phylogenetically ancient Amygdala: The neuroanatomical correlate of Fear, Anxiety, and Aggression

 

The amygdala (also corpus amygdaloideum; Greek, ἀμυγδαλή, amygdalē, ‘Almond’, ‘tonsil’) is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing of memory, decision-making and emotional responses (including fear, anxiety, and aggression), the amygdalae are considered part of the limbic system.

Each side holds a specific function in how we perceive and process emotion. The right and left portions of the amygdala have independent memory systems, but work together to store, encode, and interpret emotion.

The right hemisphere is associated with negative emotion. t plays a role in the expression of fear and in the processing of fear-inducing stimuli. Fear conditioning, which occurs when a neutral stimulus acquires aversive properties, occurs within the right hemisphere. When an individual is presented with a conditioned, aversive stimulus, it is processed within the right amygdala, producing an unpleasant or fearful response. This emotional response conditions the individual to avoid fear-inducing stimuli and more importantly, to assess threats in the environment.

www.brainfacts.org/3d-brain#intro=false&focus=Brain-limbic_system-amygdala

Structure

Subdivisions of the mouse amygdala

The regions described as amygdala nuclei encompass several structures with distinct connectional and functional characteristics in humans and other animals. Among these nuclei are the basolateral complex, the cortical nucleus, the medial nucleus, the central nucleus, and the intercalated cell clusters. The basolateral complex can be further subdivided into the lateral, the basal, and the accessory basal nuclei.

MRI coronal view of the amygdala

MRI coronal view of the right amygdala

Anatomically, the amygdala, and more particularly its central and medial nuclei have sometimes been classified as a part of the basal ganglia.

Hemispheric specializations

There are functional differences between the right and left amygdala. In one study, electrical stimulations of the right amygdala induced negative emotions, especially fear and sadness. In contrast, stimulation of the left amygdala was able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions. Other evidence suggests that the left amygdala plays a role in the brain’s reward system.


Further References

Baxter, M. G., & Murray, E. A.. (2002). The amygdala and reward. Nature Reviews Neuroscience

Plain numerical DOI: 10.1038/nrn875
DOI URL
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Li, H., Penzo, M. A., Taniguchi, H., Kopec, C. D., Huang, Z. J., & Li, B.. (2013). Experience-dependent modification of a central amygdala fear circuit. Nature Neuroscience, 16(3), 332–339.

Plain numerical DOI: 10.1038/nn.3322
DOI URL
directSciHub download

Morris, J. S., Ohman, A., & Dolan, R. J.. (1999). A subcortical pathway to the right amygdala mediating “unseen” fear. Proceedings of the National Academy of Sciences, 96(4), 1680–1685.

Plain numerical DOI: 10.1073/pnas.96.4.1680
DOI URL
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Phillips, R. G., & LeDoux, J. E.. (1992). Differential Contribution of Amygdala and Hippocampus to Cued and Contextual Fear Conditioning. Behavioral Neuroscience, 106(2), 274–285.

Plain numerical DOI: 10.1037/0735-7044.106.2.274
DOI URL
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Phelps, E. A., Delgado, M. R., Nearing, K. I., & Ledoux, J. E.. (2004). Extinction learning in humans: Role of the amygdala and vmPFC. Neuron, 43(6), 897–905.

Plain numerical DOI: 10.1016/j.neuron.2004.08.042
DOI URL
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Duvarci, S., & Pare, D.. (2014). Amygdala microcircuits controlling learned fear. Neuron

Plain numerical DOI: 10.1016/j.neuron.2014.04.042
DOI URL
directSciHub download

Ehrlich, I., Humeau, Y., Grenier, F., Ciocchi, S., Herry, C., & Lüthi, A.. (2009). Amygdala Inhibitory Circuits and the Control of Fear Memory. Neuron

Plain numerical DOI: 10.1016/j.neuron.2009.05.026
DOI URL
directSciHub download

LeDoux, J. E.. (2009). Emotion Circuits in the Brain. Focus, 7(2), 274–274.

Plain numerical DOI: 10.1176/foc.7.2.foc274
DOI URL
directSciHub download

Maren, S., & Quirk, G. J.. (2004). Neuronal signalling of fear memory. Nature Reviews Neuroscience

Plain numerical DOI: 10.1038/nrn1535
DOI URL
directSciHub download

Gross, C. T., & Canteras, N. S.. (2012). The many paths to fear. Nature Reviews Neuroscience

Plain numerical DOI: 10.1038/nrn3301
DOI URL
directSciHub download

Karalis, N., Dejean, C., Chaudun, F., Khoder, S., R Rozeske, R., Wurtz, H., … Herry, C.. (2016). 4-Hz oscillations synchronize prefrontal-amygdala circuits during fear behavior. Nature Neuroscience, 19(4), 605–612.

Plain numerical DOI: 10.1038/nn.4251
DOI URL
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Haubensak, W., Kunwar, P. S., Cai, H., Ciocchi, S., Wall, N. R., Ponnusamy, R., … Anderson, D. J.. (2010). Genetic dissection of an amygdala microcircuit that gates conditioned fear. Nature, 468(7321), 270–276.

Plain numerical DOI: 10.1038/nature09553
DOI URL
directSciHub download

Adolphs, R.. (2008). Fear, faces, and the human amygdala. Current Opinion in Neurobiology

Plain numerical DOI: 10.1016/j.conb.2008.06.006
DOI URL
directSciHub download

Kirsch, P.. (2005). Oxytocin Modulates Neural Circuitry for Social Cognition and Fear in Humans. Journal of Neuroscience, 25(49), 11489–11493.

Plain numerical DOI: 10.1523/JNEUROSCI.3984-05.2005
DOI URL
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Davis, M., Walker, D. L., Miles, L., & Grillon, C.. (2010). Phasic vs sustained fear in rats and humans: Role of the extended amygdala in fear vs anxiety. Neuropsychopharmacology

Plain numerical DOI: 10.1038/npp.2009.109
DOI URL
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SAH, P., FABER, E. S. L., LOPEZ DE ARMENTIA, M., & POWER, J.. (2003). The Amygdaloid Complex: Anatomy and Physiology. Physiological Reviews, 83(3), 803–834.

Plain numerical DOI: 10.1152/physrev.00002.2003
DOI URL
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Davis, M., & Whalen, P. J.. (2001). The amygdala: Vigilance and emotion. Molecular Psychiatry

Plain numerical DOI: 10.1038/sj.mp.4000812
DOI URL
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LeDoux, J.. (2003). The emotional brain, fear, and the amygdala. Cellular and Molecular Neurobiology

Plain numerical DOI: 10.1023/A:1025048802629
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Senn, V., Wolff, S. B. E., Herry, C., Grenier, F., Ehrlich, I., Gründemann, J., … Lüthi, A.. (2014). Long-range connectivity defines behavioral specificity of amygdala neurons. Neuron, 81(2), 428–437.

Plain numerical DOI: 10.1016/j.neuron.2013.11.006
DOI URL
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Ciocchi, S., Herry, C., Grenier, F., Wolff, S. B. E., Letzkus, J. J., Vlachos, I., … Lüthi, A.. (2010). Encoding of conditioned fear in central amygdala inhibitory circuits. Nature, 468(7321), 277–282.

Plain numerical DOI: 10.1038/nature09559
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Wolff, S. B. E., Gründemann, J., Tovote, P., Krabbe, S., Jacobson, G. A., Müller, C., … Lüthi, A.. (2014). Amygdala interneuron subtypes control fear learning through disinhibition. Nature, 509(7501), 453–458.

Plain numerical DOI: 10.1038/nature13258
DOI URL
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Feinstein, J. S., Adolphs, R., Damasio, A., & Tranel, D.. (2011). The human amygdala and the induction and experience of fear. Current Biology, 21(1), 34–38.

Plain numerical DOI: 10.1016/j.cub.2010.11.042
DOI URL
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Phelps, E. A., & LeDoux, J. E.. (2005). Contributions of the amygdala to emotion processing: From animal models to human behavior. Neuron

Plain numerical DOI: 10.1016/j.neuron.2005.09.025
DOI URL
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Olsson, A., & Phelps, E. A.. (2007). Social learning of fear. Nature Neuroscience

Plain numerical DOI: 10.1038/nn1968
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Adolphs, R.. (1997). Fear and the human amygdala. Neurocase, 3(4), 267–274.

Plain numerical DOI: 10.1093/neucas/3.4.267
DOI URL
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5-meo-dmt.tk

5-MeO-DMT (5-methoxy-N,N-dimethyltryptamine) is a psychedelic of the tryptamine class. It is found in a wide variety of plant species, and at least one toad species, the Sonora Desert toad. Like its close relatives DMT and bufotenin (5-HO-DMT), it has been used as an entheogen in South America.[1]

nn-dimethyltryptamine.tk

N,N-Dimethyltryptamine (DMT or N,N-DMT) is a tryptamine molecule which occurs in many plants and animals.[3] It can be consumed as a psychedelic drug and has historically been prepared by various cultures for ritual purposes as an entheogen.[4] Rick Strassman labeled it “the spirit molecule”.[5] In most countries, DMT is illegal.

DMT has a rapid onset, intense effects and a relatively short duration of action. For those reasons, DMT was known as the “businessman’s trip” during the 1960s in the United States, as a user could access the full depth of a psychedelic experience in considerably less time than with other substances such as LSD or magic mushrooms.[6] DMT can be inhaled, injected, vaporized or ingested, and its effects depend on the dose. When inhaled or injected, the effects last a short period of time: about 5 to 15 minutes. Effects can last 3 hours or more when orally ingested along with an MAOI, such as the ayahuasca brew of many native Amazonian tribes.[7] DMT can produce vivid “projections” of mystical experiences involving euphoria and dynamic hallucinations of geometric forms.[8]

DMT is a structural analog of serotonin and melatonin and a functional analog of other psychedelic tryptamines such as 4-AcO-DMT, 5-MeO-DMT, 5-HO-DMT, psilocybin (4-PO-DMT), and psilocin (4-HO-DMT).