5. Movement disorders

Movement disorder usually arises from damage to the central nervous system. It is commonly a result from degeneration of neurons in deep, subcortical structures, others from lesions to the cortex itself.
The subcortical structures most involved in motor dysfunction are the basal ganglia, which is a collection of structures in the forebrain.
Excessive or restricted motor activity are common symptoms of basal ganglia disporders which can also be known as extrapyramidal disoders.
The sensory motor transformation is the need to invoke a spatial reference frame that contains both information about the position of the body in space and the position of the object in space, in order to act towards an object. Complex behaviours, however, involve several motor and sensory areas.

The prefrontal cortex is part of the frontal lobe and lies in front of the premotor regions. It is involved in higher cognitive functions rather than action, whereas, the premotor cortex is involved in preparation for actions to internal and external events. The premotor cortex can be divided in to the lateral premotor cortex and the supplementary motor area.

NOTES

• Milner and Goodale suggest that there are two vision systems : visual perception and visuomotor control.
• as visual information exists two the occipital lobe, it follows two main neural streams : the ventral stream (associated with object recognition and form representation) and the dorsal stream, also known as the parietal stream (associated with where objects are in space).
• The dorsal stream ends in the posterior parietal cortex, and is the evolutionary older of the two cortical pathways.
• The Ventral stream ends in the inferotemporal cortex,and is the evolutionary newer of the two cortical pathways.
• There are two main subcortical loops involved in movement generation: The cerebellar loop and the Basil Ganglia loop.
• The cerebellar loop cooridnates timing of movement using sensory and motor information.
• The basil ganglia loop regulates the excitability of frontal motor structures.
• There are several extrapyrimidal disorders: Parkinson's disease, Huntington's disease, Sydenham's chorea, Dyskinesia, Gilles de la Tourette, Wilson's disease, Myoclonus, Ataxia and Apraxia.
• Parkinson's disease is a motor disorder characterized by a loss of movement (akinesia), resisiting passive movement (rigidity) and tremor at rest.
• Huntington's disease is an inherited motor disorder characterized by involuntary movements.
• Gilles de la Tourette syndrome describes motor and phonic tics that occur despite otherwise nomal motor behaviour.
• Apraxia is a motor disorder involving an inability to make voluntary actions to verbal commands. There are several types of Apraxia.

4. visual perception - disorders (2)

The two types of disorders discussed of visual perception are Hemispatial neglect and blindsight.
Neglect is a spatial mechanism and commonly a result of stroke and is associated with damage to the right parietal lobe. It is also caused from damage to the frontal cortex.
Those with damage to the left side can recover in as little as a few hours, however, damage to the right side can lead to long term neglect and there are no established treatments for neglect.
Object neglect is very rare and occurs when patients can see both parts of their surroundings but only have the ability to copy the image of what is presented on their right hand side.
Many experiments have been conducted to investigate this specific type of disorder. Many of the common ones used were the copying and painting task, reporting items in a room task and the cancellation task.
The cancellation task involved patients who were asked to cross out every line they see. (see left)

The video above demonstrates the concequences of visual difficulty caused by a stroke leading to neglect.
Gordon Holmes was a British Psychologist who found whilst studying bilateral lesions of parietal cortex following gun shot injuries, damage to the parietal cortex (which is involved in spatial representation) leads to visual disorientation.
Extinction is when patients are aware of objects in both areas of field but when there is visual information on both sides of the field, the patient will only see what is on the right hand side.
Neglect is modulated depending on a number of factors. If more stimuli compete in the visual field, the patient becomes distracted. The severity of neglect depends on the number of competing stimuli.
Kaplan et al constructed the group study task which suggested that neglect is not a lack of awareness of one half of space, it is a directional bias modulated by competing stimuli. patients with right parietal lesions also have impaired detection on their supposedly good right side.


Many neglect patients revisit locations on the right failing to keep track of where they have looked before.
Studies also suggest that neglect patients show deficits on non spatial tasks and it has also been found that spatial deficits interact with non spatial deficits. Research indicates that damage to the intraparietal sulcus affects memory.

3. visual perception - disorders

There are several disorders of perception. One of which is commonly known as Agnosia, a condition in which a patient is unable to recognize stimuli belonging to a particular sensory modality.
Bauer (1993) defined Agnosia as 'a failure of recognition that cannot be attributed to elementary sensory effects, mental deterioration, attentional disturbances, aphasic misnaming, or unfamiliarity with sensorially presented stimuli.'
This type of condition can be broken down in to several principal agnosias and their different neural basis. The most commonly studied are visual agnosia, auditory agnosia and tactile agnosia.
When looking in to Visual Agnosia, it can be understood that Lissauer (1890) suggested two distinct forms of agnosia known as apperceptive agnosia and associative agnosia.Apperceptive agnosia is a severe type of agnosia and describes an inability to recognize visual objects that can only be seen. Associative agnosia is a less severe form of agnosia and it describes the difficulty to recognize objects percepts with its meaning.
Here is a video in relation to associative agnosia. 

Another type of agnosia is prosopagnosia  also known as faceblindness and facial agnosia: Patients cannot consciously recognize familiar faces, sometimes even including their own. This is often misunderstood as an inability to remember names.
a useful link, as mentioned in the video below, is https://www.faceblind.org/research/index.html. which can be used to provide more knowledge on the topics as well as a test that can be carried out to investigate you're own recognition of faces. 

The FEF (frontal eye field) plays an important role in terms of attention and eye movement. It is an area in the frontal cortex involved in the generation of motor commands for pointing the eyes, and therefore the foveas, toward desired target locations.
Moore and Armstrong conducted a study where they placed a visual stimulus in the receptive field of a given V4 which is in the extrastriate visual cortical area.
Findings suggest that the FEF plays a central role in directing spatial attention and that this process is directly linked to the generation of eye movement commands, however questions still remain. 

2. Methods used to study our brain and it's cognitive function

120 years ago the brain was too complex to work on over those years operating on the brain was proven to be difficult having very little knowledge and understanding of the brain. 
Many studies/research have been conducted in measuring the brain function and structure. 
Somatosensory homunculus also known as “the little man inside the brain”, puts forward an understanding of a distorted model of a human to reflect the human body parts occupying on the somatosensory cortex and the motor cortex. Body parts such as lips, hand, feet and sex organs are very sensitive therefore have more sensory neurons so the cortex has correspondingly large lips, hands, feet and genitals. 
Single case studies have enabled researchers to study specific damaged brain areas and the resulting behaviour, however it did have its advantages and disadvantages. Although it allowed us to understand the role of a brain region, single case studies cannot conside unknown previous levels of functioning and it is subject to individual differences. 
There are several types of methods used in terms of brain surgery. From the times of labotamy, things have certainly changed and surgeons and scientists have more knowledge in terms of localization. There are four different types of methods used: 1) Behavioural Studies 2) Lesion Studies 3) Haemodynamic Studies (PET+FMRI), 4) Electromagnetic  (MEG and EEG). 
1) Electroencephalography (EEG) is the recording of electrical activity along the scalp. Although it is non-ivasive and has a high a high temporal resolution it has a significantly lower spatial resolution and it is unclear what EEG changes signifies.
2) Event-related potentials (ERP) is a measure of brain responses that is directly the result of a thought or perception and it is critcised for being a poorly understood underlying mechanism.
3) Position Emission Tomography (PET) provide a measure of brain function through the measuring oxygen consumption, blood flow and glucose metabolism. Blood flow vbeing the most reliable of the measurements. It is performed by using a gamma ray detector and provides a 3D representation  of local activity. It is however very expensive and has a poor temporal resolution. 
4) Magnetic Resonance Imaging (MRI) provides a detailed internal structures. Although it is non ivasive and non toxic  the radio frequencies must be shielded. 
5) FMRI measures blood oxygen levels, again it is non ivasive and non toxic and has an excellent spatial resolution, however the analysis is complex and it is very expensive to use. 
6) Transcranial Magnetic Stimulation (TMS) allows the modulation of cortical activity by passing alternating magnetic fields across the scalp. It induces electrical currents in the cortex increasing or decreasing its excitability. 

There are many pros and cons to these methodologies and over the last 150 years surgeons have progressed tremendous amounts at a human cost which raises the question does the end justify the means?

1. History of cognitive neuropsychology

Psychology is the study of the description, explanation, modification and prediction of human and animal behavior. Neuropsychology is the study of how the complex properties of the brain allow for the behaviour to occur. It is the observation of changes in thoughts and behaviors that relate to the structural or cognitive integrity of the brain.
Trephanation is a surgical procedure on the human skull which was used during the ancient times. it was discovered by archaeologists and involved scraping, chiseling or cutting bone from the skull.
Verona and Williams measured trephaned skulls by examining 750 skulls from Peru. They found that most of this type of surgical procedure had taken place in the frontal and upper parietal regions of the skull following injury from the pre-Colombian era. Results had also suggested that scraping and circular grooving were more successful in comparison to straight cutting and drilling. The techniques used are not so different from techniques used today.
One piece of evidence showed the drilling method. This was initiated with a ring of small holes, followed by a cut to the bone between each hole to pry off the bone piece in the center. The trephination was not completed as the patient probably had died. Various other findings of trephaned skulls show evidence of the different methods used.
The Edwin Smith Papyrus from the Ancient Egyptian era represents the earliest written record of medical treatment. Descriptions of the head and brain injury suggest that brain functions are found in specific parts of the brain.
Unfortunately during the period of the Ancient Greeks, information of brain functions were limited by the strong aversion to dissecting the brain. They had many mistaken belief, one of which was Aristotle's 'localization of mental functions in the heart'. Aristotle believed that the heart was a three chambered organ and was the center of vitality in the body and that the other organs surrounding it simply existed to cool the heart.
Pythagoras was one of the first to propose that thought processes and the soul were located in the brain, which was known as the 'brain or cephalocentric hypothesis'.
Hippocrates was an important figure in the history of medicine and believed that the brain was related to intelligence and it controlled our senses, emotions and movements. Hippocrates was the first to recognize that paralysis occurred on the opposite side of the injury.
Nemesius and Saint Augustine were influenced by the studies of Galen and they proposed 'the cell doctrine' which suggested that mental and spiritual processes/functions were localized in the brains ventricles.
Cognitive functions were arrayed from the front of the ventricles to the back. this doctrine was proved false as now we know that the ventricles are the site through which cerebrospinal fluid passes.
Galen hypothesized that pneuma (fluids) were stored in the ventricles and travelled through nerves from the brain to the muscle. Galen suggested that the physical functioning was dictated by the balance of blood, mucus, yellow bile and black bile.
Vesalius was the first to make careful observations and empirical science began to triumph over ideas proposed by Galen and Aristotle.
Descartles subscribed to some of Galens theories and introduced the idea of seperate mind and body also known as mind-body dualism.
Gall suggested that the brain was made up of seperate organs. These traits controlled complex mental faculties and phrenology correlated these with the development of specific brain areas. the development of these areas were called cerebral organs. These bumps could be analysed by a phrenology practioner and the subjects personality and intelligence can be determined.
Research has suggested that there are many faults with Gall's proposals, however, although he was almost completely incorrect, Gall's phrenology represents the beginning of the strong modern day localizationist doctrine.
During the 19th century, Broca, described the most famous case Tan. Broca used this case and others to show that the expression of language was localized to the left frontal lobe. The third convulution of the inferior posterior frontal lobe has since become known as 'Broca's area'.
Wennicke presented cases in which patients had lesions of the superior posterior part of the left hemisphere and had trouble comprehending langauge. This suggested that component processes of language were localized.
There have been many responses to localization, put forward by Freud, Flourens, Munk, Babinski and Lashley.
Freud and Flourens suggest similar anti-localization concepts and Munk and Babinski described an unawareness of deficit. Lashley supported Flourens and offered the theories of 'mass action' and 'multipotentiality' ; the amount of damaged brain tissue influences subsequent behaviour and each part of the brain participates in multiple functions.