BulletPointsummary of Principles of Cognitive Neuroscience by Purves a.o. - 2nd edition

What is Cognitive Neuroscience? - BulletPoints 1

• Cognitive functions include a number of processes through which humans and other animals perceive the outer world (external stimuli). Perceiving the outer world is done by focusing attention on important information and memorizing this, which ultimately leads to the creation of thoughts and actions. Some describe cognition as the processes influenced by the mind, but this concerns only subjective conscious experiences. However, cognitive functions can also work on a subconscious level. Therefore, most researchers do not prefer this description.
• In the mid-twentieth century, there were other developments. For example, many researchers used the workings of a computer as a metaphor for the workings of the mind. For example, Miller concluded that complex stimuli are, due to memory processes, encoded in the brain into smaller parts. Also, the behaviorist view on behavior was criticized. For example, Chomsky argued that behaviorism was not able to explain how children develop language. He argued that cognitive models should be used to explain how sensory input leads to behavioral output. Cognitive models do include psychological and internal processes. Thus, cognitive models look at psychological constructs for explaining certain phenomena. However, cognitive models do not search for causes in the brain.

Which methods and techniques are used within Cognitive Neuroscience? - BulletPoints 2

• Research methods within neuroscience can be divided into two categories:

1. Studying brain damage: this involves the effect of brain (a lesion, a stroke) damage on cognitive behavior.                                                          
2. Structural brain imaging: this method involves measuring brain activity while performing cognitive tasks. This is done by using electrophysiological and imaging techniques.

• With magnetoencephalography (MEG), electrophysiological activity can be measured by means of magnetic fields. With this technique, event-related magnetic field potentials (ERFs) can be measured. ERF signals arise from electrical currents in the dendrites that create a magnetic field. With MEG, the location and orientation of neuronal activity can be estimated, but here too, the inverse problem plays a role. MEG is sensitive to activation in sulci, but relatively insensitive to activation in gyri, this is due to the orientation of dendrites: in gyri they are upright and can therefore be measured less well. Voltage fluctuations are measured in EEG, and the orientation of the dendrites is less important. Localization is easier with MEG compared to EEG, because EEG signals are disturbed by the skull, which is not a problem with MEG. In addition, only signals from sulci are picked up by MEG, which makes localizing less complex.

How does visual perception take place? - BulletPoints 3

• Before vision is processed at the neuronal level, first light is processed by the cornea, pupil and lens. After this, the light reaches the rods and cones in the retina. Rods mainly handle low levels of light and are essential at night. Cones only process higher levels of light intensity and are important for the perception of detail and also for color perception. The speed with which the visual system has a maximum of a few hundred action potentials per second. Since this is much less compared to the amount of stimuli in the environment, the visual system makes use of sensory adaptation. This makes it possible to deal effectively with different levels of light intensity in the environment. Acuity is the sharpness, or degree of precision, with which stimuli can be perceived. Because cones, which we dominantly use during daylight, dominate the middle part of the retina (the fovea), this acuity is the sharpest in the middle of the visual field. For this reason, we also regularly move our head and eyes to focus. Our eye movements are called saccades. 
• People with synaesthesia mix different sensory experiences together. One form of synesthesia is color-graphemic synaesthesia, in wich certain numbers or letters are always seen in a certain color. It is not yet entirely clear how synesthesia arises, but the most plausible theory at the moment is that abnormal connections between brain parts developed at an early age.

How does auditory, mechanosensory and chemical sensory perception take place? - BulletPoints 4

• In humans and other mammals, energy generated by the movement of molecules in the air is converted into neural signals that ultimately lead to the perception of sound. Resonance is the continuous vibration of tense surfaces, such as a string or, for example, a bell, which is created by a thin specific structure. This can lead to the perception of a tone when these vibrations are periodic (systematic repetition of a complex wavelength), or to perception of noise when it is aperiodic. The ultimate compression of molecules generates a wavelength. Although periodic stimuli are almost non-existent in the natural environment, they are very important because vocal communication is periodic. Such stimuli are described in terms of the harmonic series that characterize these stimuli. The sound spectrum of a stimulus is determined on the basis of the so-called Fourier analysis. A mathematical formula is used to divide a sound stimulus into components. The fundamental frequency is the largest energetic component that a stimulus generates. Children are able to hear sounds between 20 and 20,000 hertz. Some animals can hear up to 200,000 hertz, probably because smaller objects also vibrate at higher frequencies.
• A cochlear implant consists of a digital signal processor that can transform a sound stimulus into individual frequency components. The auditory nerve can be electrically stimulated by means of this implant. The success of these implants shows that it is not the transformation of physical characteristics of a stimulus that is important, but that limited information is required to create the association between sound stimuli and their natural sources.

How is action organized in the motor systems? - BulletPoints 5

• All movements of the body are controlled through stimulation of muscle fibers by lower motor neurons which are located in the brain stem and in the spinal cord. These neurons can produce knee-jerk movements on their own. Complex sequential targeted movements require projections of the upper motor neurons in the cerebral cortex (primary motor cortex and other premotor regions) and the brain stem. These areas are in turn regulated by the cerebellum and basal ganglia. The cerebellum corrects errors that can arise in movements and is also important for learning new movements. The basal ganglia is mainly involved in facilitating simple forms of learning and controlling the commands for movement.
• Planning movements involves different parts of the brain such as the premotor, supplementary motor, dorsolateral premotor, dorsolateral prefrontal and parietal cortex. Planning-related activity in monkeys' premotor cortex persists even though the motion-related cue has been removed, suggesting that this part of the brain is involved in intention. In addition, planning-related neural activity takes place in the premotor cortex before the actual movement, after which activity in the primary motor cortex can be seen. The abstract planning thus appears to take place in the premotor cortex and the initiation of movements in the primary motor cortex. An EEG study in which subjects had to indicate when they wanted to perform a movement showed that before they indicated this, activity was already visible in the premotor cortex. This activity is called ‘the readiness potential’. Patients with anosognosia have damage to the premotor and primary motor cortex and are unaware of that they cannot move. This provides evidence for that the premotor cortex is important for planning movement and for awareness of intention.

What are the effects of attention on stimulus processing? - BulletPoints 6

• The cocktail party effect is the phenomenon that describes that you can selectively focus your attention on auditory input. For example, on a busy party, you can focus on your conversation and ignore the other conversations. This means that you remember most of your conversation and do not remember anything from the other conversations, because you did not direct your attention to these conversations. This has also been shown in an experiment in which subjects had to listen to two different stories in each ear. They had to ignore the story from one ear and repeat the story from the other ear. In this experiment, too, subjects could only remember the information that was provided to the ear that they focused their attention on. From this study it was concluded that stimuli that we do not focus our attention on are filtered out at an early stage. However, more recent research has shown that information that is personally relevant, such as your name, is remembered. So, when we hear our name, we remember this, even though we do not focus our attention on the story. 
• Endogenous attention refers to voluntarily focused attention on something, and it is is dependent on your goals, expectations and knowledge. Exogenous attention is reflexive attention. In a typical visual endogenous attention task, subjects have to focus on a cue that indicates where the target stimulus will appear. Sometimes, however, the cue will appear in a different location. These studies show that subjects are faster at detecting stimuli that appear at the cued location. When varying the interval between the cue and the stimulus, it has been found that between 300 milliseconds and a few seconds after, attention is strongest to the cue location. In exogenous tasks, a cue is also provided before the target stimulus appears. The difference with the endogenous tasks is that it is not explicitly mentioned here that the stimulus is presented at the location where the cue appears. Still, in these exogenous tasks, subjects respond faster when a cue is presented at the same location prior to the stimulus. With exogenous tasks, attention for the cued location occurs after just 75 milliseconds, but it also lasts shorter (a few hundred milliseconds), in addition, inhibition of return can occur. This is the phenomenon in which subjects react more slowly when the stimulus is presented at the cue location when the interval between the cue and the stimulus is approximately 300 to 800 milliseconds.

How is attention controlled? - BulletPoints 7

• Damage to the right inferior parietal lobe creates deficits in the spatial attention to the left side of the visual field. So, patients with hemispheric neglect ignore stimuli in the left visual field. The underlying problem appears to be a defect in attention and not a sensory defect. In the line cancellation test, patients have to cross out lines, but patients with hemispheric neglect only cross out the lines on the right side of the page (so also on the right side of their visual field). Another effect of neglect is that patients only shave their beard on one side of the face. As noted, neglect has to do with a deficit in attention: only one side enters the patients’ attention.
• In behavioral studies of visual search, participants have to look for target stimuli among other distracting stimuli. Pop-out stimuli are stimuli that differ in one characteristic from the other stimuli (for example in color). With pop-out stimuli, for the time it takes to find these, it does not matter how many distracting stimuli are present. This suggests that sequential shifts in attention are not necessary to find these stimuli. However, when a target stimulus differs from the distracting stimuli in several properties, the time it takes to find this stimulus is linearly related to the amount of distracting stimuli.

What variations and mechanisms are there in our memory? - BulletPoints 8

• Perception is the result of the interaction between sensory stimuli and information that is already stored in memory. Attention, emotional responses, and the way you look at yourself are all affected by your memory.
• Dissociating between memory systems is achieved by studying the effects of brain lesions, by using functional brain imaging techniques, or by using electrophysiological measurements.

What is the declarative memory? - BulletPoints 9

• Event-related memory is called episodic memory and fact-related memory is called semantic memory. Both are forms of the declarative memory and sometimes overlap. Autobiographical memory consists of this complex form of overlapping memory. Episodic memory can be divided into recollection, which refers to remembering an event with certain associations and contextual details, and familiarity, which refers to the feeling that we have experienced or experienced something similar, but without specific details and associations. However, there is a debate about the subdivision of familiarity under the episodic memory because it consists of conscious memories for events and the neural mechanisms are related to those of semantic memory and priming.
• It has already been discussed that it is assumed that the episodic memory is stored in different cortical areas that are specialized in the processing of certain information (visual cortex, auditory cortex, etc.). This assumption is also made with semantic memory, although the focus is more on different types of knowledge such as knowledge about animals or about tools. With semantic memory, the focus is on the organization, while with episodic memory this is on the reactivation.

What can be said about emotions from the perspective of the cognitive neuroscience? - BulletPoints 10

• A post-traumatic stress disorder (PTSD) is characterized by flashbacks of a traumatic experience, increased arousal, avoidance of memories of the traumatic event and often it is also accompanied by depression and substance abuse. The volume of the hippocampus and amygdala is often reduced in these patients. The degree of reduction in hippocampal volume is related to impaired declarative memory and the degree of PTSD symptoms. Amygdala dysfunction is related to increased arousal and exaggerated responses to threats. Studies using twins suggest that reduced hippocampal volume predisposes individuals to developing PTSD. Thus, whether these changes in brain volume are the cause or the result of PTSD is not known.
• According to James, experiencing changes in the body (physical response) sends feedback to the sensory and motor cortex, after which and through which an emotion is experienced. This theory has two assumptions: first, it assumes a deterministic relationship between physical reactions and emotions, and second, it assumes that emotions cannot be experienced without physical reactions because they are causally related. Around the same time of this theory, the Danish physiologist Carl Lange proposed a similar theory, arguing that heart function was most relevant to emotion and not the conscious experience of emotion. The nuclei in the brainstem that regulate heart function were important for experiencing an emotion, according to Lange. Lange and James agreed on the relationship between brain activity and physiological responses, which is how the James-Lange theory was born.

How does social cognition take place according to the cognitive neuroscience? - BulletPoints 11

• Social deficits such as difficulty in using non-verbal communication, difficulty in developing relationships, difficulty in spontaneously seeking shared joy, and reduced social or emotional reciprocity are core symptoms of autism. When looking at faces, autistic individuals show decreased activity in the fusiform gyrus, the inferior temporal sulcus, the superior temporal sulcus and the amygdala. Individuals with autism also experience difficulties with the theory-of-mind task. They also have a relatively large brain volume, which is probably due to an overgrowth of connections in early development. This growth of connections occurs in the hemispheres, but interhemispheric connections are less well developed. Some autistic individuals show a great talent in some particular area, this is sometimes referred to as the savant syndrome. At the same time, autistic individuals have more difficulty integrating different parts into a whole (central coherence) and have a tendency to systematize by applying rigid mechanical rules.
• Social categorization is useful because it makes it easier to create impressions about others. From an evolutionary point of view, social categorization is important because it increases the chances of survival when you have to defend your territory. However, it can also lead to social injustice when reactions to others are influenced by stereotypes.

What is the perspective of the cognitive neuroscience on language? - BulletPoints 12

• Phonemes are the basic sounds that make up speech. A syllable consists of one or more phonemes and words consist of several syllables. There are about 200 different phonemes worldwide and each language uses 50 to 100 phonemes. Because other languages ​​use different phonemes, learning a new language is so difficult: you also have to learn to produce new sounds. Phonemes can be divided into vowels and consonants. Vowels provide the most pronounced sounds. Consonants are phonemes that usually occur at the beginning or end of a syllable, the sounds are often shorter and are acoustically more complex. Consonants are also the most important for the transmission of information through speech.
• Homonyms are words with the same sound and spelling but with different meanings, such as the word ‘book’. This word can resemble a book that you can read, but it can also mean that you want to book a reservation. Homophones are words that sound the same but have different meanings and spellings, such cell and sell. To decide on which word to pick, the context is crucial. In a study examining the importance of context, words were divided into pieces and rearranged. This study showed that the correct understanding of a word or sound was strongly dependent on the context. The McGurk effect also shows this: what we hear is strongly influenced by what we see. This integration of different sensory modalities occurs in the superior temporal sulcus.

What can be said about executive functions from the perspective of cognitive neuroscience? - BulletPoints 13

• Executive functions have a supervisory and regulatory role. It seems that the prefrontal cortex is particularly important for executive functions. For example, studies on patients with damage to the prefrontal cortex have shown that they have difficulties in selecting the correct actions in certain contexts. However, many more parts of the brain, such as the parietal cortex and the basal ganglia.
• Patients with damage to lateral parts of the PFC show little spontaneity in thoughts and actions and also lose interest in social contacts. However, symptoms can be very different, for example, patients with the condition ‘abulia’, which also results from lateral damage to the PFC, often have motor defictis and can make movements when given command and answer questions, but are very slow in doing so. How are these rules for initiating and executing behaviors regulated in the brain? Populations of neurons carry information about different rules and the activity of these neurons depends on which rules are relevant to the context. An electrophysiological study in monkeys in which they had to create associations between pairs of stimuli showed that it was not the stimuli presented, but the rules that accompanied them that activated certain neurons. These rule selective neurons are found in the PFC. However, when a rule requires a complex sequence of behaviors, a neuron may only code for part of this rule. In addition to the PFC, the creation of new rules involves the basal ganglia which interacts with the PFC to exert cognitive control. fMRI studies have shown that the basal ganglia is mainly involved in the association between stimuli and rules and that the parietal cortex is activated when a participant creates and remembers different possible actions.

How are choices made? - BulletPoints 14

• Dopamine plays an important role in reward responses. The substantia nigra and the ventral tegmental area (VTA) contain dopamine neurons. Neurons in the substantia nigra contribute to the control of motor movement because of its connection to the basal ganglia. The VTA contributes to reward evaluations through its projections to the nucleus accumbens (sometimes referred to as the ventral striatum), the amygdala, the hippocampus, and the medial frontal lobe. When neurons in the brainstem of rats that project to the nucleus accumbens were stimulated when they displayed a particular behavior, they continued to do so, even at the expense of eating, drinking, or having sex. The simple idea that dopamine is fun is not correct. When dopamine-toxic chemicals were injected into the nucleus accumbens of rats, they would not even eat if they were starving. However, these rats still responded to pleasant and aversive flavors. From this and other studies, Berridge concluded that dopamine is not about preference (liking) but about wanting. More recent research has also shown that activation of the nucleus accumbens is associated with various motivational stimuli. In addition, an external reward actually reduces involvement in a task. For example, when participants played a simple game and were put into the fMRI scanner, the ventral striatum showed activation. In the group that received a reward after playing this game, this activation in the ventral striatum was no longer visible.
• In addition to goal-directed actions, behavior is often also formed through creating associations between values ​​and actions, such as is the case in habits. Habits are acquired very slowly, but once they are formed, they are difficult to unlearn. Being able to associate stimuli with rewards and choose the right motor actions for future outcomes are essential for reward learning. Actor-critic learning models assume that two brain systems exist, a “critic” who evaluates whether rewards are better or worse than expected, and an “actor” who evaluates the values ​​of certain behaviors to increase future rewards. The ventral striatum is associated with the “critic” system that evaluates reward signals through input from the VTA. Neurons in the dorsal striatum are associated with the creation of behavioral plans through the “actor” system. Fictional learning refers to changes in behavior in response to what could have been fictitious error signals associated with activation in the caudate nucleus.

How has the brain developed and evolved? - BulletPoints 15

• Darwin's generally accepted idea is that the morphological traits of each organism are a mixture of traits shared with many other animals because of their common ancestor. The process of adaptation remains the most dominant theme in understanding the forces that make up every biological property, such as the human brain. Darwin also showed that certain emotional expressions manifest the same in different species. Individual experiences and developments also contribute to who we ultimately are. Piaget was the first to conduct scientific research into children's cognition. He believed that children actively shape their understanding of the world through assimilation and accommodation. During assimilation, new experiences are added to previously formed schemas and knowledge, and in accommodation, these schemas and / or knowledge are adjusted when new information is not applicable to previous information. In addition, Piaget stated that children go through different stages, with each stage presenting different cognitive limitations and challenges. Although in contemporary times, not all ideas of Darwin and Piaget are supported, they have an important influence on ideas about the development and evolution of the brain and cognition. An important idea that both Piaget and Darwin held is that ontology repeats evolution. The stages that a child goes through in his development parallel changes in the course of evolution. Therefore, the finding that cognitive characteristics that humans share with other animals arise early in human development is important.
• After neurons are formed, axonal pathways are formed between neurons. These axons are directed to cells (neurons, muscle or gland cells) by molecular cues. When axons have reached these cells, synapses are formed, this is called synaptogenesis. This synaptogenesis occurs at different times, in different parts of the brain. The loss of synapses occurs throughout development and synaptic connections are changed and adapted throughout life. Studies conducted with rhesus monkeys have shown that synapses develop until adolescence and then decline after adolescence. The synaptic production varies per brain part, but parts of the brain that are important in early development develop for parts of the brain of which the functions are important after birth. Synaptogenesis is always accompanied by the loss of synapses and rearrangement. These synaptic changes are the basis for learning and memory. Another important point about neuronal connectivity is that neurons in one area seem to work just as well when they are located in another area. In experimental animals, the auditory cortex appears to process visual functions when connections to the thalamus are surgically altered. While the neurons are not the same, their functions seem to depend mainly on the areas in which they are located. In other words, the plasticity of neuronal function is greatest in early development.