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Spatial neglect describes a condition in which the attention to stimuli is withdrawn from one side of the visual field.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.