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Article

Brain Basis of Blindsight  

Holly Bridge

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

Capacity Assessment Across Functional Domains in Later Life  

Benjamin T. Mast and Diana DiGasbarro

Clinicians conduct capacity evaluations to determine an older adult’s ability to make and execute a decision within key domains of functioning. Questions of capacity often arise when an older adult experiences a decline in cognitive functioning due to Alzheimer’s disease, stroke, or severe psychiatric illness, for example. Capacity is related to legal competency, and a lack of capacity may be proved by providing evidence that an older adult is unable to understand the act or decision in question; appreciate the context and consequences of the decision or act; reason about the potential harms and benefits; or express a choice. Capacity is domain-specific, time-specific, and decision-specific. Domains include financial capacity, medical treatment and research consent capacity, driving capacity, sexual consent capacity, and voting capacity. Each capacity domain encompasses activities that may vary in complexity or risk, and thus require different levels of capacity. For example, within the medical treatment consent capacity domain, an older adult may lack the capacity to consent to a complicated and risky surgical procedure while retaining the capacity to consent to a routine blood draw. Clinicians determine capacity by using a combination of tools including capacity assessment instruments, task-specific functional evaluations, interviews with the patient and family members, measures of cognitive functioning, and consideration of social, physical, and mental health factors. Extensive research has been conducted to determine the reliability and validity of a variety of capacity assessment instruments for many domains. These instruments generally assess the patient’s responses to vignettes pertaining to the domain in question, information gleaned from structured and semi-structured interviews, functional ability, or a combination of these methods. Although there is still need for more research, especially in emerging domains, capacity assessments help to protect vulnerable older adults from harm while allowing them to retain the highest possible level of autonomy.

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

Progressive Neurological Conditions and Their Impact on Psychological Well-Being in Later Life  

Nadeeka N. Dissanayaka

Progressive neurological disorders are incurable disorders with gradual deterioration and impacting patients for life. Two common progressive neurological disorders found in late life are Parkinson’s disease (PD) and motor neuron disease (MND). Psychological complications such as depression and anxiety are prevalent in people living with PD and MND, yet they are underdiagnosed and poorly treated. PD is classified a Movement Disorder and predominantly characterized by motor symptoms such as tremor, bradykinesia, gait problems and postural instability; however, neuropsychiatric complications such as anxiety and depression are common and contribute poorly to quality of life, even more so than motor disability. The average prevalence of depression in PD suggest 35% and anxiety in PD reports 31%. Depression and anxiety often coexist. Symptoms of depression and anxiety overlap with symptoms of PD, making it difficult to recognize. In PD, daily fluctuations in anxiety and mood disturbances are observed with clear synchronized relationships to wearing off of PD medication in some individuals. Such unique characteristics must be addressed when treating PD depression and anxiety. There is an increase in the evidence base for psychotherapeutic approaches such as cognitive behavior therapy to treat depression and anxiety in PD. Motor neuron disease (MND) is classified a neuromuscular disease and is characterized by progressive degeneration of upper and lower motor neurons is the primary characteristic of MND. The most common form of MND is Amyotrophic lateral sclerosis (ALS) and the terms ALS and MND are simultaneously used in the literature. Given the short life expectancy (average 4 years), rapid deterioration, paralysis, nonmotor dysfunctions, and resulting incapacity, psychological factors clearly play a major role in MND. Depression and suicide are common psychological concerns in persons with MND. While there is an ALS-specific instrument to assess depression, evaluation of anxiety is poorly studied; although emerging studies suggesting that anxiety is highly prevalent in MND. Unfortunately, there is no substantial evidence-base for the treatment of anxiety and depression in MND. Caregivers play a major role in the management of progressive neurological diseases. Therefore, evaluating caregiver burden and caregiver psychological health are essential to improve quality of care provided to the patient, as well as to improve quality of life for carers. In progressive neurological diseases, caregiving is often provided by family members and spouses, with professional care at advanced disease. Psychological interventions for PD carers addressing unique characteristics of PD and care needs is required. Heterogeneous clinical features, rapid functional decline, and short trajectory of MND suggest a multidisciplinary framework of carer services including psychological interventions to mitigate MND. A Supportive Care Needs Framework has been recently proposed encompassing practical, informational, social, psychological, physical, emotional, and spiritual needs of both MND patients and carers.