G. Campbell Teskey
The kindling phenomenon is a form of sensitization where, with repetition, epileptiform discharges become progressively longer and behavioral seizures eventually appear and then become more severe. The classic or exogenous kindling technique involves the repeated application of a convulsant stimulus. This technique also lowers seizure thresholds, the minimum intensity of a stimulus required to evoke an electrographic seizure, a process known as epileptogenesis. Endogenous kindling typically occurs following a brain-damaging event which lowers seizure thresholds to the point where self-generated epileptiform discharges recur, lengthen, propagate, and drive progressively more severe behavioral seizures. While exogenous kindling results in alterations in neuronal molecular, cellular/synaptic, and network function that give rise to altered behavior, there is a paucity of evidence for loss of neurons. In contrast, brain-damaging events, with neuronal loss, typically give rise to endogenous kindling. Kindling is a pan-species phenomenon and all mammals that have been examined, including humans, manifest exogenous kindling when seizure-genic (forebrain) structures have been targeted. Since humans display both exogenous and endogenous kindling phenomena this serves as a sober warning to clinicians to prevent seizures. Kindling serves as a robust and reliable model for epileptogenesis, focal as well as secondarily generalized seizures, and certain epileptic disorders.
The sensation of vision arises from the detection of photons of light at the eye, but in order to produce the percept of the world, extensive regions of the brain are required to process the visual information. The majority of information entering the brain via the optic nerve from the eye projects via the lateral geniculate nucleus (LGN) of the thalamus to the primary visual cortex, the largest visual area, having been reorganized such that one side of the brain represents one side of the world.
Damage to the primary visual cortex in one hemisphere therefore leads to a loss of conscious vision on the opposite side of the world, known as hemianopia. Despite this cortical blindness, many patients are still able to detect visual stimuli that are presented in the blind region if forced to guess whether a stimulus is present or absent. This is known as “blindsight.” For patients to gain any information (conscious or unconscious) about the visual world, the input from the eye must be processed by the brain. Indeed, there is considerable evidence from functional brain imaging that several visual areas continue to respond to visual stimuli presented within the blind region, even when the patient is unaware of the stimulus. Furthermore, the use of diffusion imaging allows the microstructure of white matter pathways within the visual system to be examined to see whether they are damaged or intact. By comparing patients who have hemianopia with and without blindsight it is possible to determine the pathways that are linked to blindsight function. Through understanding the brain areas and pathways that underlie blindsight in humans and non-human primates, the aim is to use modern neuroscience to guide rehabilitation programs for use after stroke.
Neil E. Rowland
Thirst is a specific and compelling sensation, often arising from internal signals of dehydration but modulated by many environmental variables. There are several historical landmarks in the study of thirst and drinking behavior. The basic physiology of body fluid balance is important, in particular the mechanisms that conserve fluid loss. The transduction of fluid deficits can be discussed in relation to osmotic pressure (osmoreceptors) and volume (baroreceptors). Other relevant issues include the neurobiological mechanisms by which these signals are transformed to intracellular and extracellular dehydration thirsts, respectively, including the prominent role of structures along the lamina terminalis. Other considerations are the integration of signals from natural dehydration conditions, including water deprivation, thermoregulatory fluid loss, and thirst associated with eating dry food. These mechanisms should also be considered within a broader theoretical framework of organization of motivated behavior based on incentive salience.
There is intense contemporary public as well as professional psychological interest in bodily movement, gesture, and the subjective experience of movement. This has a background in knowledge that movements and the sensing of movements alike express the life of the whole person, whether in the arts, sports, and the pursuit of well-being, or in physiotherapies and psychotherapies of many kinds. The background of the numerous and varied areas of scientific research that contribute to this area has a long history in philosophy and cultural practices as well as in relations between different psychological and physiological topics. The significance of the sense of self-movement, kinesthesia, as opposed to the perception of moving objects, has not until recently been a central focus for research. To explain rising contemporary interest it is necessary to elucidate the usage of current terms—kinesthesia, proprioception, and haptic sense. This in turn leads to discussion of the historical background to modern research on kinesthesia and motor imagery, on phenomenology and sensed movement, on practice centered on kinesthetic appreciation, and on agency. All this is part of the field of inquiry into the psychology of performing and of appreciating dance.
Vanessa L. Burrows
Stress has not always been accepted as a legitimate medical condition. The biomedical concept stress grew from tangled roots of varied psychosomatic theories of health that examined (a) the relationship between the mind and the body, (b) the relationship between an individual and his or her environment, (c) the capacity for human adaptation, and (d) biochemical mechanisms of self-preservation, and how these functions are altered during acute shock or chronic exposure to harmful agents. From disparate 19th-century origins in the fields of neurology, psychiatry, and evolutionary biology, a biological disease model of stress was originally conceived in the mid-1930s by Canadian endocrinologist Hans Selye, who correlated adrenocortical functions with the regulation of chronic disease.
At the same time, the mid-20th-century epidemiological transition signaled the emergence of a pluricausal perspective of degenerative, chronic diseases such as cancer, heart disease, and arthritis that were not produced not by a specific etiological agent, but by a complex combination of multiple factors which contributed to a process of maladaptation that occurred over time due to the conditioning influence of multiple risk factors. The mass awareness of the therapeutic impact of adrenocortical hormones in the treatment of these prevalent diseases offered greater cultural currency to the biological disease model of stress.
By the end of the Second World War, military neuropsychiatric research on combat fatigue promoted cultural acceptance of a dynamic and universal concept of mental illness that normalized the phenomenon of mental stress. This cultural shift encouraged the medicalization of anxiety which stimulated the emergence of a market for anxiolytic drugs in the 1950s and helped to link psychological and physiological health. By the 1960s, a growing psychosomatic paradigm of stress focused on behavioral interventions and encouraged the belief that individuals could control their own health through responsible decision-making. The implication that mental power can affect one’s physical health reinforced the psycho-socio-biological ambiguity that has been an enduring legacy of stress ever since.
This article examines the medicalization of stress—that is, the historical process by which stress became medically defined. It spans from the mid-19th century to the mid-20th century, focusing on these nine distinct phases:
1. 19th-century psychosomatic antecedent disease concepts
2. The emergence of shell-shock as a medical diagnosis during World War I
3. Hans Selye’s theorization of the General Adapation Syndrome in the 1930s
4. neuropsychiatric research on combat stress during World War II
5. contemporaneous military research on stress hormones during World War II
6. the emergence of a risk factor model of disease in the post-World War II era
7. the development of a professional cadre of stress researchers in the 1940s and 50s
8. the medicalization of anxiety in the early post–World War II era
9. The popularization of stress in the 1950s and pharmaceutical treatments for stress, marked by the cultural assimilation of paradigmatic stress behaviors and deterrence strategies, as well pharmaceutical treatments for stress.
The role of experience in brain organization and function can be studied by systematically manipulating developmental experiences. The most common protocols use extremes in experiential manipulation, such as environmental deprivation and/or enrichment. Studies of the effects of deprivation range from laboratory studies in which animals are raised in the absence of sensory or social experiences from infancy to children raised in orphanages with limited caregiver interaction. In both cases there are chronic perceptual, cognitive, and social dsyfunctions that are associated with chronic changes in neuronal structure and connectivity. Deprivation can be more subtle too, such as being raised in a low socioeconomic environment, which is often associated with poverty. Such experience is especially detrimental to language development, which in turn, limits educational opportunities. Unfortunately, the effects of some forms of socioemotional deprivation are often difficult, if not impossible, to ameliorate.
In contrast, adding sensory or social experiences can enhance behavioral functions. For example, placing animals in environments that are cognitively, motorically, and/or socially more complex than standard laboratory housing is associated with neuronal changes that are correlated with superior functions. Enhanced sensory experiences can be relatively subtle, however. For example, tactile stimulation with a soft brush for 15 minutes, three times daily for just two weeks in infant rats leads to permanent improvement in a wide range of psychological functions, including motoric, mnemonic, and other cognitive functions. Both complex environments and sensory stimulation can also reverse the negative effects of many other experiences. Thus, tactile stimulation accelerates discharge from hospital for premature human infants and stimulates recovery from stroke in both infant and adult rats. In sum, brain and behavioral functions are exquisitely influenced by manipulation of sensory experiences, especially in development.
Neil E. Rowland
Hunger is a specific and compelling sensation, sometimes arising from internal signals of nutrient depletion but more often modulated by numerous environmental variables including taste or palatability and ease or cost of procurement. Hunger motivates appetitive or foraging behaviors to find food followed by appropriate proximate or consummatory behaviors to eat it. A critical concept underlying food intake is the flux of chemical energy through an organism. This starts with inputs of food with particular energy content, storage of excess energy as adipose tissue or glycogen, and finally energy expenditure as resting metabolic rate (RMR) or as metabolic rate is modified by physical activity. These concepts are relevant within the context of adequate theoretical accounts based in energy homeostasis; historically, these are mainly static models, although it is now clear that these do not address practical issues such as weight gain through life. Eating is essentially an episodic behavior, often clustered as meals, and this has led to the idea that the meal is a central theoretical concept, but demonstrations that meal patterns are greatly influenced by the environment present a challenge to this tenet. Patterns of eating acquired during infancy and early life may also play a role in establishing adult norms. Direct controls of feeding are those that emphasize food itself as generating internal signals to modify or terminate an ongoing bout of eating, and include a variety of enteroendocrine hormones and brainstem mechanisms. Additionally, many studies point to the essential rewarding or hedonic aspects of food intake, including palatability, and this may involve integrative mechanisms in the forebrain and cerebral cortex.
Trevor A. Harley
Research in the psychology of language has been dogged by some enduring controversies, many of which continue to divide researchers. Furthermore, language research has been riven by too many dichotomies and too many people taking too extreme a position, and progress is only likely to be made when researchers recognize that language is a complex system where simple dichotomies may not be relevant. The enduring controversies cover the width of psycholinguistics, including the work of Chomsky and the nature of language, to what extent language is innately determined and the origin of language and how it evolved. Chomsky’s work has also influenced our conceptions of the modularity of the structure of the mind and the nature of psychological processing. Advances in the sophistication of brain imaging techniques have led to debate about exactly what these techniques can tell us about the psychological processing of language. There has also been much debate about whether psychological processing occurs through explicit rules or statistical mapping, a debate driven by connectionist modeling, deep learning, and techniques for the analysis of “big data.” Another debate concerns the role of prediction in language and cognition and the related issues of the relationship between language comprehension and language production. To what extent is language processing embodied, and how does it relate to controversies about “embedded cognition”? Finally, there has been debate about the purpose and use of language.
Ananiev’s approach shares the Activity Theory (AT) paradigm, dominant in Soviet psychology. Ananiev builds on the main fundamentals of the AT paradigm, considering psyche as a special procreation of the matter, engendered by the active interaction of the individual with the environment. The unique feature of his approach to AT is that he turned it “toward the inside,” focusing on the relation of the human individual to his own physicality, to his own bodily substrate. Ananiev sought by his intention to keep a holistic vision of a human being, considering the latter in the context of his real life, that is, the bodily substrate in its biological specificity in context of the concrete sociohistorical life course of the personality. Like no other psychologist, Ananiev did not limit his research to the sphere of narrowly defined mental phenomena. He conducted a special kind of research, labeled as “complex,” in the course of which characteristics of the same subjects: sociological, socio-psychological, mental, physiological, and psychophysiological indicators—life events of the subjects—were monitored for many years. He focused on ontogenetic development in adulthood, which he, ahead of his time, considered as a period of dynamic changes and differentiated development of functions. The focus of his attention was on individual differences in the ontogenetic development of mental and psycho-physiological functions, especially those deviations from general regularities that resulted from the impact of the life course of the individual. Individualization, the increase of individual singularity, is the main effect of human development and its measure for Ananiev.
Ananiev developed a number of theoretical models and concepts. The best-known of Ananiev’s heritage is his theoretical model of human development, often named the “individuality concept.” According to this model, humans do not have any preassigned “structure of personality” or “initial harmony.” The starting point of human development is a combination of potentials—resources and reserves, biological and social. The human creates himself in the process of interaction with the world. Specialization, individually specific development of functions, appears here not as a distortion of the pre-set harmony of the whole but as the way of self-determining progressive human development. The most important practical task of psychology he viewed as psychological support and provision in the process of developing a harmonious individuality, based on the individual potentials.
Imprinting is a form of rapid, supposedly irreversible learning that results from exposure to an object during a specific period (a critical or sensitive period) during early life and produces a preference for the imprinted object. The word “imprinting” is an English translation of the German Prägung (“stamping in”), coined by Konrad Lorenz in 1935 to refer to the process that he studied in geese. Two types of imprinting have traditionally been distinguished: filial imprinting, involving the formation of an immediate social attachment to the mother or a mother-substitute, and sexual imprinting, involving the formation of a sexual preference that is manifested later in life. Both types of imprinting were subject to extensive experimental study beginning around 1950. Originally described in precocial birds (ducks, geese, and domestic chickens), imprinting has also been used to explain the formation of early social attachments in other species, including human infants. Imprinting has served as a useful model for studying the neural processes involved in learning and behavioral development and has provided a framework for thinking about other developmental processes.