Week 11

Spatial and non-spatial working memory at different stages of Parkinson's disease

Parkinson’s disease (PD) is characterized through the deterioration of motor functions, produced through the decline of dopamine-generating cells. Owen et al. (1997) now suggests that parallel to this motor function degeneration, there is a deterioration of cognitive functions. In their study Owen et al. tested 21 patients with PD in different stages (mild and severe), being either medicated or non-medicated, on their abilities in three different kinds of working memory (spatial, verbal, visual). 


As they predicted, they found an increase of impairment parallel to an increase of severeness in the disease. Non-medicated patients with mild symptoms showed no impairment in all three working memories, medicated patients with mild symptoms showed an impaired spatial working memory but normal abilities for the visual and verbal task, and medicated patients with severe symptoms showed impairment in all 3 tests. It was concluded that first symptoms of PD occur in the frontal lobe (spatial) and then expanding to other brain areas. Compared to Patients with frontal lobe damage however, patients with PD show significantly less severe symptoms.

However, Owen et al. mentioned an extreme difference in task difficulty between the spatial task and the verbal and visual task. A slightly more difficult spatial task would be expected to show impairment even for the first condition. (210 words).

Nevertheless, this study failed to explicitly test any additional frontal lobe functions in PD, which makes it hard to evaluate the expansion of the impairment in these patients. Since frontal lobe patients show a complete destruction of the brain tissue, whereas PD only exhibits deterioration of single areas within the lobe, less severe symptoms might be expectable.

Week 10

Memory for Places learned long ago is intact after hippocampal damage

Many studies over the past decades suggested an important role of the hippocampus for navigation and orientation. A study by Maguire et al. (1997) found an enlarged hippocampus in London taxi drivers who through functional imaging, and Morris et al. (1982) even found impairments in navigation in rats with a damaged hippocampus.

A study by Teng and Squire (1999) however, examined a patient with virtually complete bilateral damage to the hippocampus. Patient E.P. (76 years) had amnesia in 1992 and moved to a new city in 1993. As expected, it was impossible for him to retrieve any information about the city he is currently living in. However, observing his virtually navigation skills for remote memories of the city he grew up in, showed no difference to controls. Teng and Squire concluded, that the hippocampus is necessary for the encoding of long-term declarative memories but seems to be spared in their retrieval.

It can be criticised however that E.P was asked 10 questions about navigating to different locations whereas controls were only asked a mean of 9.5 questions. More questions can improve an overall performance. Moreover, results of controls are given as rages, without stating a mean or SD. In the case of outliers, comparing E.P.’s performance with the controls can lead to misinterpretation (213 words).

Nevertheless, it is shown that navigation cannot be located in the hippocampus completely, since E.P was able to complete most of the given tasks without impairment.

Week 9

Executive Functions

Executive functions are generally explained as a set of abilities within the human frontal lobe that help us to guide our behaviour, particularly in unknown situations. These functions include processes like prioritizing and sequencing of behaviour, inhibiting impulsive behaviour, planning, mental flexibility, and decision-making. Due to the wide rage of processes involved, impairments are difficult to be diagnosed through the assesment of a single test. It is therefore suggested to use different tasks to examine different facets.

Most scientists share the assumption of executive functions to effortfully guide goal-directed behaviour. Psychological and neurobiological models however differ highly. Banich, 2011 proposes that different parts of the frontal lobe create a pathway of information to achieve the correct response. Explaining her model however, it can be criticized that alternative explanations have not been taken into account but just briefly overviewed. It is claimed that the posterior part of the dorsolateral prefrontal cortex (DLPFC) first gives notice on the top-down attention, deciding where to focus attention. The mid-DLPFC then decides which of the perceived representations is more relevant for the task. The posterior dorsal anterior cingulate cortex (ACC) determines which response to exhibit and passes the decision on to the dorsal ACC where the final evaluation takes place. If the dorsal ACC accepts the response it will be executed (216 words). If it gets disapproved, a signal gets send back to the Prefrontal cortex to start the process over again.

The intensity of each mechanism increases with the decrease of previous mechanisms in the pathway, and therefore can differ highly in each individual. Moreover the level or activation of certain mechanisms is highly associated with the age of the individual. 

Week 8

Laterality in humans

The human body seems symmetrical in external and internal anatomy, but looking closer, we can observe high levels of asymmetry. Even the brain exhibits a great level of asymmetry, anatomically as well as functionally. Several studies have reported for the left-hemisphere to be rather rational, verbal, linear and analytic, whereas the right-hemisphere seems to be emotional, spatial, holistic and intuitive. Arthur Wigan (1844) was one of the first scientists arguing for our hemispheres to be independent entities. Following, researchers examining split-brain patients supported that statement reporting patients acting as having two separate brains. Further research suggested the left-hemisphere to be mainly involved in language whereas the right-hemisphere showed more activation during visuospatial tasks.

Several single-word studies showed great involvement of the left-hemisphere, however, when expanding to sentences and discourse comprehension, the right hemisphere also seemed to show involvement. Therefore it has been speculated that the right-hemisphere is involved in the sentence's thematic sense. Bottini et al. (1994) found for the right-hemisphere to process metaphors and irony.

A study by De Renzi (1982) argued for the right-hemisphere to be involved in visuospatial abilities. Other scientists however argued for a less defined cut, since the right-hemisphere showed high activity during mental rotation processes, but the left-hemisphere seemed to be involved in other visual tasks. (212 words). Harris et al. (2000) then discovered the right posterior parietal lobe to process extreme rotations, with high levels of decision-making, whereas the left side might rather be involved in simple visual tasks.

In conclusion it can be said, that most cognitive functions are not processed in one hemisphere only. Moreover, their involvement in the task differs in gender and handedness. 

Week 7

The Iowa gambling task and the somatic marker hypothesis

The somatic marker hypothesis (SMH) describes a theory, suggesting that cognitive processes such as decision making can be highly influenced by emotions. One way this hypothesis can be tested has been explained in an article by Bechara et al. (1997) using the Iowa gambling task (IGT). The IGT is a relatively simple decision-making experiment, using rewarding and punishment as consequences for participants decisions. Here, participants have to choose several cards from 4 different decks of card, 2 of which are “good decks” and 2 of which are “bad decks”. Bechara et al. found a significant learning effect, showing that after few trials, healthy participants would choose the good deck rather than the bad one. Additionally, throughout the task, skin conductance response (SCR) was measured, showing a significant increase during more risky decisions.

Patients with lesions in the ventromedial prefrontal cortex (VMPC) failed to monitor such SCRs. Moreover, there was no evidence of a learning effect but a rather deficient way of playing was displayed. These findings supported the SMH, suggesting that patients with VMPC damage have impaired emotional progressing and therefore returned to decks with bad outcomes sooner as normal patients. Their decisions were found to be mainly based on the most recent outcome whereas normal participants managed to learn from their overall experience of all past trials. (200 words). When forming a decision, the brain receives emotional-related marker signals that can be unconscious or conscious, helping to form an adequate decision.

These findings have been supported by Maria and Mc Clelland (2004), who used a replication of the IGT, but did not monitor the SCRs of normal participants or patients. This has been highly criticised by Bechara er al. (2005), since the failure of VMPC damaged patients to display such SCRs stays to be an outstanding mystery. Bechara et al. (2005) argues that rather than not showing SCRs, VMPC damaged patients should rather show an even stronger one, since based on their decision through knowledge and their inner gut feeling seems to form distinct decisions. This would be an interesting area fro further research.

Week 5

Movement disorders
Previous research suggested that our central nervous system (CNS) contains internal models that make it possible for us to form a representation of our body within our environment. Within these internal models, we differentiate between the forward model and the inverse model. The forward model is used as a predictor of our behaviour, and its consequences. In other words, the forward model uses motor commands as “moving the arm” and predicts the arms new position. The inverse model on the other hand produces motor commands to achieve the desired body position. In this case for example, it would get the environmental input (“how far is the object?; how heavy is it?”) and uses this information to define accurate motor commands (more information by Wolpert et al.). Even though some research suggests that we are aware of our motor actions, it can be assumed, that not all processes of these two internal models are done consciously.

Impairments of these internal models can be used to explain several motor disorders, some of which I will explain in more detail.

Optic ataxia shows general difficulties in grasping an object, even though the visual abilities of the patient are intact. In other words, the brain seems to be unable to use information about its environment to define accurate motor movements. Blakemore et al. therefore, explains the phenomena with an impaired inverse model, which causes a lack of information about the object being grasped for an adjustment of the grasping movements. Another example is explained in a disorder called anarchic hand, where participants complain about their hand moving by itself.  Here, the inverse model seems to forms the representation and sends the information, but does it inappropriately and causes involuntarily motor actions.

Week 4

Spatial neglect

Spatial neglect describes a condition in which the attention to stimuli is withdrawn from one side of the visual field. Neglect arises after brain damage to the inferior parietal lobule (defines the location of stimuli) and always affects the contralateral side (opposite the brain damage) of the visual field. Even though, it can occur in either side of the brain, right hemispatial neglect is reported to be the more common one. This could be due to the fact that left hemispatial neglect is normally presented as less severe.

Spatial neglect can be further divided into two subtypes. The space around a person is described in two areas, the space within the reach of the person (peripersonal space) and the space within walking distance (extrapersonal space). Some patients might display neglect in only one of the two, while the other one is still normally functioning.

Neglect can be tested in several ways, using tests like cancelling out stimuli on a paper or copying images, which all show clear inattention to the contralateral side. The patient however, in most cases, is completely unaware of this disfunction (anosagnosia) and can only notice his deficit (missed stimuli on one side of the paper, copy of only one side of the image) when pointed out to him/her. The realization then, of having neglect, arises after several months and is part of it's recovery.

Extinction:

Extinction is seen as a milder version of neglect, since patients attend to the contralateral side when a stimulus is shown. However, when stimuli are presented on the contralateral side, as well as on the ipsilateral side (same side than the lesion), the patients will only be able to focus their attention on the stimui presented on the ipsilateral side and therefore show the symptoms of neglect in this situation.

Most people are shown to recover from spatial neglect in only few months. However, this does not apply to every patient. Recovery can last several years, or can not occur at all, depending on the patient.

Week 3

Moving the Mind's Eye Before the Head's Eye

Why do we have to move our eyes across a scene?

Our eyes have to move across scenes to capture our complete surrounding. Our environment reflects on out retina, which then sends the information of our visual input to the brain. However, not everything we have in our sight is actually focused, in colour and identifiable. Picture 1 presents our actual vision.

The focused centre is all the information taken in by the foveal, which takes up a small percentage of our retina. Without moving out eyes, this would be all the input we get. However, our eyes automatically do small saccades and take in a bigger picture of our environment.

How small the area of detailed information actually is, can be realized by focusing on one spot of this text and trying to continue reading without moving the eye. One can at most finish the next word, before the letters become too unfocused to recognize.

Would it not be easier if we could see the whole scene in front of us at once?

If our complete retina would take in detailed information of our vision as the foveal does, our brain would be flooded with useless information. Taking in our environment in every detail is not necessarily a good thing, since we would be overloaded with information about unimportant details. Moreover, receiving the complete scene in detail would need more receptors on our retina, which on the other hand would lead to more synapses within our brain. Not only would this then lead to an increase in size of eye and brain but it would also demand an imense need of energy (glucose) to keep the brain working.

What does FEF mean? And what is its role in vision?

The frontal eye field (FEF) describes a area of the frontal cortex of the human brain which plays an important role in directing your sight towards a stimulus of attention. Findings of a study by Moore and Armstrong (2003) suggest that the FEF helps us to direct spatial attention to stimuli and sends commands to the oculomotor system, moving our eyes and therefore our foveal towards the stimuli.

Week 2

How do we study our brain and its cognitive functions?

Nowdays, studying our brain can be done it lot more detail than we would have imagined it a few years ago. Several imaging techniques have helped to get an insight into the human brain before actually, physically looking into it. A few of these scans should be explained in

more detail. The Electroencephalography (EEG) basically tests electrical potentials, meaning the firing of neurons, in the brain, locating a brains activity. (picture)

Positron Emission Tomography (PET) detects activation in the brain though measuring the blood flow within the brain, since active areas have an increased blood supply. The Magnetic Resonance Imaging (MRI) is based on stimulating magnetic fields in our brain, observing the activity of atomic nuclei. And last but not least, the functioning Magnetic Resonance Imaging (fMRI). The fMRI is sensible to the brains metabolism and therefore similar to the PET scan, detects brain activity through the change of blood within the active brain areas. All neuroimaging techniques differ in their image quality, as well as their speed, and therefore have to be chosen depending on the matter observed.

These ways of scanning made it possible for us today, to receive a relatively clear image of how our brain looks from the inside, and where brain activities are located. Through stimulation or task execution, cognitive functions can then be allocated to certain brain areas, giving us an even greater insight of the psychological functioning of the brain. Ramachandran clearly explains in his Lecture the importance of combining cognitive abilities or behaviour to ones brain activity. In the end, many psychological syndromes and ways of behaviour can be explained through our brain activities observed through such scans.

Week 1

Is technology really relevant to the advance of our knowledge about brain, behaviour and cognition?

Through the ongoing restrictions of ethics, experimenting on humans and animals is becoming more and more limited. Especially in the areas of Neuropsychology, brain research is nearly impossible in a living organism without using technology. Furthermore, behaviour and cognition in relation to the brain must be tested in conscious open brain procedures. Leaving out technology in such procedure would be fairly impossible since without localizing certain areas within the brain, damage can be done easily producing inherent changes in the subject’s behaviour, abilities or quality of life.

Technology is providing evidence for something that only has been an idea or a theory in the past. These theories, drillings and brain surgeries over the past thousands of years have been important for our today understanding and it’s what has created an interest in the science. Today however, knowledge has come to a level where it is hard to evaluate further without technology.

Which event(s) in the history of neuropsychology do you consider more relevant? Why?

With a science such as Neuropsychology it is hard to define its start or just one important event in its history, since they normally evolve over several centuries. Events like Trephanations are extremely relevant in the history of neuropsychology since they already addressed the idea of brain surgeries in the case of head injuries. However, the idea behind the procedure was still spiritual rather than medical. Wholes were cut into the brain to release evil spirits that were causing head pain. Even hundreds of years later, Aristotle stated that the ”brain” was actually located in the heart, which shows a clear lack of medical knowledge at this time. The most important event in the history of neuropsychology therefore, would be the start of a general neurological understanding, which roughly started around 550 BC when scientists first discovered a relationship between our brain and our behaviour. Other important events then followed with the studies of Hippocrates, 150 years later when not only intelligence and emotions were found to be located in the human brain but scientists started to discover the human brain anatomy.