week. 11

When studying neurospychology there are different methods used when testing. One study which is widely quoted is the article on Spatial and no spatial working memory at different stages of Parkinson's disease (A.M. Owen et al). It is one of the first studies to show a difference between spatial and non spatial working memory and this particular article is based on a working memory task. It focuses on patients with Parkinsons disease and evidently, this type of movement disorder affects patients spatial memory before verbal memory.
The article looks at medicated patients against non-medicated patients. Previous studies has shown that dopamine has complex affects on spatial working memory and does actually improve it. Results from the article discussed earlier, suggest that there is no significant difference when testing non-medicated patients, however, patients with mild or severe clinical symptoms, showed a difference. The staging criteria for Parkinson's disease is now assessed using the unified Parkinson's disease rating scale. The difference found from the study, is unclear as to whether the results are because of the particular stages of the disease or if it is in fact because of the affect of the medicine, as dopamine changes the balance of receptors.
The study looks at the CANTAB test which can also be used to measure strategy, It looks at spatial, verbal and visual memory and it has been made so complicated so that the visual presentation is as similar as possible.

Memory

There are several processes involved when storing information. Memory is a process and not unitary and involves encoding, retrieval, recall and recognition.
A lot of research has been conducted in the past to discuss and evaluate the existence of the several types of memory proposed from scientists and theorists.
James (1890) was one of the earliest to suggest that we have a primary memory and secondary memory. This was later researched further, to find that infact the primary memory is short term memory and the secondary memory is long term memory (Braudbent 1958).
there are of course several divisions of those dichotomies. The long term memory can be fractioned in to declarative memory ( explicit memory) and nondeclarative memory (implicit memory). Declarative memory refers to the recall and recogntion of facts which can be accessed to conscious recollection. Non declarative refers to the recall of material that is not deliberately encoded or retrieved.
Squire (1994) suggests that declarative memory 'refers to a biologically meanginful category or memory depending on specific brain systems.' Schacter (1987) refers to non declarative memory as the memory that involves no explicit or conscious intention to lear or memorise and that 'it embraces several kinds of memory and depends on multiple brain systems.' Declarative memory can be subdivided to semantic memory and episodic memory.
Another type of memory is working memory and is in association with what we do with materials in the short term memory and many have criticised it has may be isomorphic.
There are evidence supporting the existence of short term memory and long term memory. This is proven in studies on patients with impairments and lesions. Short term memory is a distributed organisation and is associated with the left parietal lobe in the brain. Many parts of the brain are involved in long term memory.
Theres are several types of impairments, one of the most well known, major impairment is amnesia. This type of impairment refers to partial or complete loss of memory. There are two types of Amnesia, first being retrograde amnesia and is related to things that have happened in the past. Anterograde amnesia is when they can remember the past but can not create new memories.

8. Hemispheric lateralisation

By lateralization, we understand that there is a preferential use or superior function of one side of the brain. The brain exhibits elements of asymmetry itself, although it appears symmetrical. For example, the right hemisphere is thought to be larger and heavier than the left (Heschl, 1878, Schwartz et al 1985), however, Cunningham (1892) proposed that the left occipital lobe was found to be larger than the right. The left hemisphere is rational, verbal, linear and analytiic, whereas the right hemisphere is emotional, spatial and holistic and intuitive ( Bradshaw and Nettleton 1981; Van Lancker 1997). The relationship, however, between anatomical assymetry and functional significance is far from clear ( Beaton 1997).
Myths and Folklore put forward the idea that there are two sides of the brain and that there are differences. The duality of mind model (Wigan 1844) suggests that parts of the brain are more dominant on one side but hemispheres must work together to function properly.
A study on chimeric faces found that the left visual field is processed by the right hemisphere. it occurs not just with the visual stimuli with auditory stimuli too.
Paul Broca (1861) was a physician who performed brain surgeries. Broca found that lesions in the left hemisphere affects language function. Hughlings Jackson (1864) suggests the human brain does not duplicate functions in both hemispheres, however, this is not totally correct.

The two hemispheres have subtle qualitative and quantitative differences. For example, in relation to sound, the left hemisphere is more predominant.
A split brain surgery has no connection between hemispheres in terms of language and speech, a patient with a normal brain, suggest that the right hemisphere has some linguistic abilities. A patient with partial separation found that the right hemisphere match printed words and pictures, but can not match words that rhyme. This suggests that the right hemisphere lacks ability to do phonological decoding. A patient with complete separation suggests that the right hemispheres grammatical abilities match that of a five year old. In relevance to attention, asymettry is not so strong. Depending on the type of the attention, some parts of the brain are more active.
There are also individual differences such as gender. It has been said that males are better at navigating by looking at maps, whereas, women are better at navigating based on landmarks. Women are also better at verbal, memory and language. There is a small difference in object location too.
Research shows that lesions affect lateralisation of function. Split brain surgery is a form of medical procedure which gives the ability to understand hemispheres and its associative functions.

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?