Psychopathology

Critism of psychology

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Neuropsychology
From Wikipedia, the free encyclopedia

Neuropsychology is a branch of psychology that aims to understand how the structure and function of the brain relate to specific psychological processes.

It is scientific in its approach and shares an information processing view of the mind with cognitive psychology and cognitive science.
It is one of the more eclectic of the psychological disciplines, overlapping at times with areas such as neuroscience, philosophy (particularly philosophy of mind), neurology, psychiatry and computer science (particularly by making use of artificial neural networks).

In practice neuropsychologists tend to work in academia (involved in basic or clinical research), clinical settings (involved in assessing or treating patients with neuropsychological problems - see clinical neuropsychology), forensic settings (often assessing people for legal reasons or court cases or working with offenders, or appearing in court as expert witness) or industry (often as consultants where neuropsychological knowledge is applied to product design or in the management of pharmaceutical clinical-trials research for drugs that might have a potential impact on CNS functioning).

Approaches

Experimental neuropsychology is an approach which uses methods from experimental psychology to uncover the relationship between the nervous system and cognitive function. The majority of work involves studying healthy humans in a laboratory setting, although a minority of researchers may conduct animal experiments. Human work in this area often takes advantage of specific features of our nervous system (for example that visual information presented to a specific visual field is preferentially processed by the cortical hemisphere on the opposite side) to make links between neuroanatomy and psychological function.

Clinical neuropsychology is the application of neuropsychological knowledge to the assessment (see neuropsychological test and neuropsychological assessment), management and rehabilitation of people who have suffered illness or injury (particularly to the brain) which has caused neurocognitive problems. In particular they bring a psychological viewpoint to treatment, to understand how such illness and injury may affect and be affected by psychological factors. Clinical neuropsychologists typically work in hospital settings in an interdisciplinary medical team, although private practice work is not unknown.

Cognitive neuropsychology is a relatively new development and has emerged as a distillation of the complementary approaches of both experimental and clinical neuropsychology. It seeks to understand the mind and brain by studying people who have suffered brain injury or neurological illness. One model of neuropsycholgical functioning is known as localization. This is based on the principle that if a specific cognitive problem can be found after an injury to a specific area of the brain, it is possible that this part of the brain is in some way involved. However, this dated, simplistic model is usually rejected in the current literature. A model such as parallel processing has more explanatory power for the workings and dysfunction of the human brain. A more recent but related approach is cognitive neuropsychiatry which seeks to understand the normal function of mind and brain by studying psychiatric or mental illness.

Connectionism is the use of artificial neural networks to model specific cognitive processes using what are considered to be simplified but plausible models of how neurons operate. Once trained to perform a specific cognitive task these networks are often damaged or 'lesioned' to simulate brain injury or impairment in an attempt to understand and compare the results to the effects of brain injury in humans.

Functional neuroimaging uses specific neuroimaging technologies to take readings from the brain, usually when a person is doing a particular task, in an attempt to understand how the activation of particular brain areas is related to the task. In particular, the growth of methodologies to employ cognitive testing within established functional magnetic resonance imaging (fMRI) techniques to study brain-behavior relations is having a notable influence on neuropsychological research.

In practice these approaches are not mutually exclusive and most neuropsychologists select the best approach or approaches for the task to be completed.

Methods and tools

• The use of standardized neuropsychological tests. These tasks have been designed so the performance on the task can be linked to specific neurocognitive processes. These tests are generally standardized, meaning that they have been administered to a specific, target group of individuals before being used in the public sphere. The data resulting from standardization are known as normative data. After these data have been collected and analyzed, they are used as the comparative standard against which individual performances can be compared. Examples of Neuropsychological tests include, but are not limited to: the Halstead-Reitan Neuropsychological Battery, the Boston Naming Test, the Wisconsin Card Sorting Test, and the Woodcock-Dean.

• The use of brain scans to investigate the structure or function of the brain is common, either as simply a way of better assessing brain injury with high resolution pictures, or by examining the relative activations of different brain areas. Such technologies may include fMRI (functional Magnetic Resonance Imaging) and PET (Positron Emission Tomography), which yields data related to functioning, as well as MRI (Magnetic Resonance Imaging) and CAT (or CT) (Computed Axial Tomography), which yields structural data.

• The use of electrophysiological measures designed to measure the activation of the brain by measuring the electrical or magnetic field produced by the nervous system. This may include EEG (Electroencephalography) or MEG (Magneto-encephalography).
• The use of designed experimental tasks, often controlled by computer and typically measuring reaction time and accuracy on a particular tasks thought to be related to a specific neurocognitive process.
Methods and tools

Neuroimaging

From Wikipedia, the free encyclopedia

Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the brain. It is a relatively new discipline within medicine and neuroscience.

It falls into two broad categories: structural imaging and functional imaging. The former deals with the overall structure of the brain and the precise diagnosis of intracranial disease and injury. The latter is used for neurological and cognitive science research and building brain-computer interfaces. It enables, for example, the processing of sensory information coming to the brain and of commands going from the brain to the organism to be "lit up" or visualized directly instead of by simple clinical inference
Types of brain imaging

CAT

CT scan slice showing indicating damage cause by stroke (arrow).
Computed tomography (CT or CAT) scanning uses a series of x-rays of the head taken from many different directions. Typically used for quickly viewing brain injuries, CT scanning has a computer program that uses a set of algebraic equations to estimate how much x-ray is absorbed in a small area within a cross section of the brain (Jeeves 21). In the final analysis, the harder a material is, the whiter it will appear on the scan. CT scans are primarily used for evaluating swelling from tissue damage in the brain and in assessment of ventricle size. Modern CT scanning exposes the subject to about as much radiation as a single x-ray and can provide reasonably good images in a matter of minutes.

MRI

High-resolution sagittal MRI slice at the midline.
Magnetic Resonance Imaging (MRI) uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without injecting radioactive tracers. During an MRI, a large cylindrical magnet creates a magnetic field around the head of the patient through which radio waves are sent. When the magnetic field is imposed, each point in space has a unique radio frequency at which the signal is received and transmitted (Preuss). Sensors read the frequencies and a computer uses the information to construct an image. The detection mechanisms are so precise that changes in structures over time can be detected. Using MRI, scientists can create images of both surface and subsurface structures with a high degree of anatomical detail. MRI scans can produce cross sectional images in any direction from top to bottom, side to side, or front to back. The problem with original MRI technology was that while it provides a detailed assessment of the physical appearance of the brain, it fails to provide information about how well the brain is working at the time of imaging. The distinction is now made between MRI imaging and functional imaging since the brain's function rather than the brain's structure is of interest.

fMRI

Axial MRI slice at the level of the basal ganglia, showing fMRI BOLD signal changes overlayed in red (increase) and blue (decrease) tones.
Functional magnetic resonance imaging (fMRI) relies on the paramagnetic properties of oxygenated and deoxygenated hemoglobin to see images of changing blood flow in the brain associated with neural activity. This allows images to be generated that reflect which structures are activated (and how) during performance of different tasks. Most fMRI scanners allows subjects to be presented with different visual images, sounds and touch stimuli, and to make different actions such as pressing a button or moving a joystick. Consequently fMRI can be used to reveal brain structures and processes associated with perception, thought and action. The resolution of fMRI is about two or three millimeters at present, limited by the spatial spread of the hemodynamic response to neural activity. It has largely superseded PET for the study of brain activation patterns. PET, however, retains the significant advantage of being able to identify specific brain receptors associated with particular neurotransmitters through its ability to image radiolabelled receptor ligands.

PET

PET scan of normal 20 year old brain.
Positron Emission Tomography (PET) measures emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream and uses the data to produce two or three-dimensional images of the distribution of the chemicals throughout the brain (Nilsson 57). The positron emitting radioisotopes used are produced by a cyclotron and chemicals are labelled with these radioactive atoms. The labeled compound, called a radiotracer, is injected into the bloodstream and eventually makes its way to the brain. Sensors in the PET scanner detect the radioactivity as the compound accumulates in different regions of the brain. A computer uses the data gathered by the sensors to create multicolored two or three-dimensional images that show where the compound acts in the brain.

The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and glucose metabolism in the tissues of the working brain. These measurements reflect the amount of brain activity in the various regions of the brain and allow us to learn more about how the brain works. PET scans were superior in terms of resolution and speed of completion (as little as 30 seconds) when they first came online. The improved resolution permitted better judgments to be made as to the area of the brain activated by a particular task. The biggest drawback of PET scanning is that because the radioactivity decays rapidly, it is limited to monitoring short tasks (Nilsson 60). Before fMRI technology came online, PET scanning was the preferred method of brain imaging, and it still continues to make large contributions to neuroscience.

SPECT

SPECT is similar to PET. Single photon emission computed tomography (SPECT) uses gamma ray emitting radioisotopes and a gamma camera to record data that a computer uses to construct two- or three-dimensional images of active brain regions (Ball). SPECT relies on an injection of radioactive tracer, which is rapidly taken up by the brain but does not redistribute. Uptake of SPECT agent is nearly 100% complete within 30 – 60s, reflecting cerebral blood flow (CBF) at the time of injection. These properties of SPECT make it particularly well suited for epilepsy imaging, which is usually made difficult by problems with patient movement and variable seizure types. SPECT provides a "snapshot" of cerebral blood flow since scans can be acquired after seizure termination (so long as the radioactive tracer was injected at the time of the seizure). A significant limitation of SPECT is its poor resolution (about 1 cm) compared to that of MRI.

DOT
See diffuse optical imaging

Cognitive neuroscience

From Wikipedia, the free encyclopedia

The field of cognitive neuroscience concerns the study of the neural mechanisms underlying cognition and is a branch of biological psychology which, in turn, is part of the wider field of neuroscience, the most comprehensive interdisciplinary discipline studying the brain.

Cognitive neuroscience overlaps with cognitive psychology, and in fact has its roots largely in cognitive neuropsychology. But whereas cognitive psychologists seek to understand the mind, researchers in cognitive neuroscience are concerned with understanding how mental processes take place in the brain. Cognitive neuroscientists tend to have a background in experimental psychology, neurobiology, neurology, physics, and mathematics. Cognitive psychology and cognitive neuroscience influence each other on a continuous basis, since an understanding of mental structure can inform theories about brain functions and knowledge about neural mechanisms is useful in understanding mental structure.

Methods include psychophysical experiments, functional neuroimaging, neuropsychology and behavioral neuroscience. Cognitive neuroscience also makes contact with low-level data from electrophysiological studies of neural systems and, increasingly, cognitive genomics. The main theoretical approaches are computational neuroscience and the more "abstract" information processing approaches, inherited from cognitive psychology, psychometrics (mathematical psychology) and neuropsychology.

Neurological disorders are disorders that affect the central nervous system (brain, brainstem and cerebellum), the peripheral nervous system (peripheral nerves - cranial nerves included), or the autonomic nervous system (parts of which are located in both central and peripheral nervous system). Neurologists also diagnose and treat some conditions in the musculoskeletal system.

Major conditions include:
• headache disorders such as migraine, cluster headache and tension headache
• epilepsy and seizure disorders
• neurodegenerative disorders, the most common class being dementias, including Alzheimer's disease
• cerebrovascular disease, such as transient ischemic attacks, and strokes (ischemic or hemorrhagic)
• sleep disorders
• cerebral palsy
• infections of the central nervous system (encephalitis), brain envelopes (meningitis) and peripheral nerves (neuritis), such as brain abscess, herpetic meningoencephalitis, aspergilloma, cerebral hydatic cyst
• some infections of the peripheral nervous system, such as tetanus and botulism
• neoplasms - tumors of the brain and its envelopes (brain tumors), spinal cord tumors, tumors of the peripheral nerves (neuroma)
• movement disorders such as Parkinson's disease, chorea, hemiballismus, tic disorder, and Gilles de la Tourette syndrome
• demyelinating diseases of the central nervous system, such as multiple sclerosis, and of the peripheral nervous system, such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP)
• spinal cord disorders - tumors, infections, trauma, malformations (e.g., myelocele, meningomyelocele, tethered cord)
• disorders of peripheral nerves, muscle (myopathy) and neuromuscular junctions
• traumatic injuries to the brain, spinal cord and peripheral nerves
• altered mental status, encephalopathy, stupor and coma

General caseload

Neurologists are responsible for the diagnosis, treatment, and management of all the above conditions. When surgical intervention is required, the neurologist may refer the patient to a neurosurgeon, an interventional neuroradiologist, or a neurointerventionalist. In some countries, additional legal responsibilities of a neurologist may include making a finding of brain death when it is suspected that a patient is deceased. Neurologists frequently care for people with hereditary (genetic) diseases when the major manifestations are neurological, as is frequently the case. Lumbar punctures are frequently performed by neurologists. Other neurologists may develop an interest in particular subfields, such as movement disorders, headaches, epilepsy, sleep disorders, multiple sclerosis or neuromuscular diseases.
The core neurological diseases that are the primary domain of neurologists are:
• demyelinating diseases of the central nervous system.
• the epilepsies
• headache and migraine
• movement disorders
• polyneuropathies
• spinal cord disorders
• genetic diseases with a primarily neurologic manifestation

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