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.
Article
Brain Basis of Blindsight
Holly Bridge
Article
Influence of Anxiety on Cognitive Control Processes
DeMond M. Grant and Evan J. White
Cognitive control is the ability to direct attention and cognitive resources toward achieving one’s goals. However, research indicates that anxiety biases multiple cognitive processes, including cognitive control. This occurs in part because anxiety leads to excessive processing of threatening stimuli at the expense of ongoing activities. This enhanced processing of threat interferes with several cognitive processes, which includes how individuals view and respond to their environment. Specifically, research indicates that anxious individuals devote their attention toward threat when considering both early, automatic processes and later, sustained attention. In addition, anxiety has negative effects on working memory, which involves the ability to hold and manipulate information in one’s consciousness. Anxiety has been found to decrease the resources necessary for effective working memory performance, as well as increase the likelihood of negative information entering working memory. Finally, anxiety is characterized by focusing excessive attention on mistakes, and there is also a reduction in the cognitive control resources necessary to correct behavior. Enhancing our knowledge of how anxiety affects cognitive control has broad implications for understanding the development of anxiety disorders, as well as emerging treatments for these conditions.
Article
Insomnia and Clinical Sleep Disturbance in Later Life
Simon Smith
Sleep health is understood as a key factor in lifelong health and for social participation, function, and satisfaction. In later life, insomnia and other sleep disturbances are common. Insomnia is experienced as poor, disrupted, or insufficient sleep associated with significant daytime impairments including increased fatigue or reduced energy, impaired cognitive function, and increased mood disturbance. Poor sleep is associated with negative outcomes across a range of dimensions that impair quality of life, increases risk for other diseases, and may interact negatively with the progression and treatment of other disorders. Evidence for effective psychological interventions to improve sleep in later life, specifically cognitive behavioral therapy for insomnia, is robust and well described. Good sleep should be understood as a substrate for psychological health and a reasonable expectation in later life.
Article
Memory Rehabilitation in Healthy Aging
Nicole D. Anderson
Healthy aging is accompanied by decrements in episodic memory and working memory. Significant efforts have therefore been made to augment episodic and working memory in healthy older adults. Two principal approaches toward memory rehabilitation adults are restorative approaches and compensatory approaches. Restorative approaches aim to repair the affected memory processes by repeated, adaptive practice (i.e., the trained task becomes more difficult as participants improve), and have focused on recollection training, associative memory training, object-location memory training, and working memory training. The majority of these restorative approaches have been proved to be efficacious, that is, participants improve on the trained task, and there is considerable evidence for maintenance of training effects weeks or months after the intervention is discontinued. Transfer of restorative training approaches has been more elusive and appears limited to other tasks relying on the same domains or processes. Compensatory approaches to memory strive to bypass the impairment by teaching people mnemonic and lifestyle strategies to bolster memory performance. Specific mnemonic strategy training approaches as well as multimodal compensatory approaches that combine strategy training with counseling about other factors that affect memory (e.g., memory self-efficacy, relaxation, exercise, and cognitive and social engagement) have demonstrated that older adults can learn new mnemonics and implement them to the benefit of memory performance, and can adjust their views and expectations about their memory to better cope with the changes that occur during healthy aging. Future work should focus on identifying the personal characteristics that predict who will benefit from training and on developing objective measures of the impact of memory rehabilitation on older adults’ everyday functioning.
Article
Neuroimaging
Chelsea Ekstrand
The growing field of neuroimaging has offered exciting insights into the inner workings of the human brain in health and disease. Structural neuroimaging techniques provide detailed information about the physical properties and anatomy of the brain and nervous system, including cerebrospinal fluid, blood vessels, and different types of tissue. The most commonly used structural neuroimaging techniques are computed tomography (CT) and structural magnetic resonance imaging (MRI). CT uses X-rays to create a two-dimensional representation of neural tissue, whereas MRI quantifies differences in tissue density by manipulating molecules using magnetic fields, magnetic field gradients, and radio waves. Functional neuroimaging techniques provide a measure of when and where activity is occurring in the brain by quantifying underlying physiological processes. Functional neuroimaging techniques fall into two broad categories: measures of direct brain activity, including electroencephalography (EEG) and magnetoencephalography (MEG), and measures of indirect brain activity, such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and functional near-infrared spectroscopy (fNIRS). Different functional neuroimaging techniques can be used to examine different physiological changes, including electrical activity, magnetic field changes, metabolic and neurotransmitter activity, and indirect measures of blood flow to offer insight into cognitive processing. Structural and functional neuroimaging have made a profound impact on understanding the brain both during normal functioning and in clinical pathology. Overall, neuroimaging is a powerful tool for both research and clinical practice and offers a noninvasive window into the central nervous system of humans in both health and disease.
Article
Prospective Memory and Cognitive Aging
Simon J. Haines, Jill Talley Shelton, Julie D. Henry, Gill Terrett, Thomas Vorwerk, and Peter G. Rendell
Tasks that involve remembering to carry out future intentions (such as remembering to attend an appointment), and the cognitive processes that enable the completion of such tasks (such as planning), are referred to as prospective memory (PM). PM is important for promoting quality of life across many domains. For instance, failures in remembering to meet social commitments are linked to social isolation, whereas failures in remembering to fulfill occupational goals are linked to poorer vocational outcomes. Declines in PM functioning are of particular concern for older adults because of the strong links between PM and functional capacity. The relationship between age and PM appears to be complex, dependent on many factors. While some aspects of PM appear to hold up relatively well in late adulthood, others appear to show consistent age-related decline. Variability in age differences appears to partially reflect the fact that there are diverse types of PM tasks, which impose demands on a range of cognitive processes that are differentially affected by aging. Specifically, the level and type of environmental support associated with different PM task types appears to be a meaningful determinant of age-related effects. Given the worldwide changing age demographics, the interest in age-related effects on PM will likely intensify, and a primary focus will be how to optimize and maintain PM capacity for this population. This is already reflected in the increasing research on interventions focused on enhancing PM capacity in late adulthood, and points to important future directions in this area of study.
Article
Worry and Rumination
Ed Watkins
Worry and rumination are both forms of repetitive negative thought (RNT) characterized by repetitive and often uncontrollable thinking about negative content. Rumination is typically defined as repetitive thinking about the symptoms, causes, circumstances, meanings, and consequences of negative mood, personal concerns, and upsetting experiences, often with a focus on depressive experience. Worry is typically defined as repetitive thinking about future potential threat, imagined catastrophes, uncertainties, and risks and is conceptualized as an attempt to avoid negative events, prepare for the worst, and problem-solve. Worry and rumination are implicated in the exacerbation of negative mood and negative thinking, reduced central executive resources, impaired problem- solving, and prolonged sympathetic activation and emotional responses to stress and, as such, transdiagnostically contribute to the onset and maintenance of multiple emotional disorders, including major depression, anxiety disorders, insomnia, eating disorders, substance and alcohol abuse, and psychosis. Both worry and rumination are implicated in poor response to psychological interventions—greater reduction in RNT is associated with greater symptom improvement, whereas no change in RNT is associated with no improvement or worsening of symptoms. Rumination and worry appear to be moderately genetically heritable and predicted by environmental factors such as early adversity, stressful life events, and unhelpful parental styles. RNT is a common pathway between multiple risk factors, including neglect, abuse, bullying, and chronic stress, and later psychopathology. Pathological worry and rumination share an abstract processing style, negative biases in attention and interpretation, and impaired executive control and are mental habits. Both worry and rumination have been hypothesized to serve an avoidant function. Interventions that target these mechanisms appear to be effective at tackling RNT, particularly rumination-focused cognitive-behavioral therapy and mindfulness-based interventions. More efficient interventions for anxiety and depression may result from interventions that target multiple of these proximal mechanisms.
