Only being able to pay attention to what happens on your right. It may sound like a diagnosis taken from a bad rom-com, but for some people it's a reality.
What causes hemispatial neglect syndrome is most likely damage to the right parietal lobe, and adjacent regions, in the brain, from for example a stroke. Interestingly, lesions in the corresponding left hemisphere, do not give rise to equally distinct complications. One theory for this is because lesions to right cause implications in both hemispheres whereas lesions to the left are mainly affecting the parietal area to the right.
The implications of hemineglect are that the patient have a difficulty turning their attention to objects in their left visual field. This does not necessarily mean that they are blind to whatever is on their left. Experiments have concluded that especially salient objects, such as food to a hungry individual, is reported to be seen. When the object in the left visual field are of less importance, however, or when patients with severe hemineglect are to take care of their own shaving or application of make up, the left side is often untouched.
Another phenomenon of hemineglect is that of extinction. This is when a stimulus in the left visual field that has previously been attended to gets neglected due to a similar stimulus occurring simultaneously in the right visual. In the lab, this has been tested by having an examiner standing in front of a hemineglect patient with their arms outstretched. A finger is then moved, on either the examiner's right or left hand. The patient can generally report a moving finger, probably due to the fact that this sort of moving stimulus is pertinent also for these people. Where this commodity changes, however, is when both fingers are moved at the same time. Patients then report solely the moving finger on the right, having neglected the one on the left.
Clinical tests have shown that no memory of how it should be is affected in patients with hemineglect. It is only their perception of reality that changes. There are various exams that can be made, a famous one being asking the patient to draw a clock from memory. Here the patient may draw a clock with all the numbers in correct order but fails to put any of them on the left of the circle.
Other tests include asking the patient to draw a house from memory and having them draw half a house, asking them to bisect a line and having the dividing line be to the right of the middle as the patient are unable to identify the whole line. Also asking patients to cross out a set of lines normally results in the crossing of the lines to the right while the ones on the left are left untouched.
Though there is still much that is unknown about hemispatial neglect syndrome, it is counted as the earliest described neurological disease related to attention control, being first detailed in the 1940s. Like with much of the field of neuroscience, we can't be entirely sure as to what is the physiological reasons to what happens, or what is the best way to care for it, but at least with hemineglect you can be sure to always be right.
The Book; Neuroscience Sixth Edition, Dales Purves, George J. Augustine