How many times have you gone to the fridge or the closet looking for something specific, and even though you had what you were looking for right in front of you, you didn’t see it? If this ever happened to you, you were probably surprised to find it where you had not seen it before: “But it wasn’t there earlier…”, you thought to yourself.
A similar sensation is usually described by people who suffer from hemispatial neglect when, by changing position or perspective, they suddenly become aware of an object that, while remaining in the same place the whole time, had gone unnoticed .
Hemispatial neglect is a disturbance of attention following brain injuryin which people fail to respond or orient to stimuli or objects in one half of space (usually the side opposite their lesion) while being able to attend to stimuli in the other half [2,3].
Although unilateral spatial neglect or neglect syndrome can result from damage to the left hemisphere of the brain, it is more common and severe after right hemisphere damage[2,3]; therefore it has been suggested that hemispatial neglect is best described as an indifference to the left side of the world .
People with hemispatial neglect due to right hemisphere lesions do not look or turn their head towards the left side, nor do they attend to visual, auditory or tactile stimuli on their left and thus, it is common that they eat only the food on the right half of the plate, draw only the right half of the objects when copying, or read half of the sentences or words in the absence of sensory deficits [2,3].
In a study that exemplifies the nature of this disorder , patients were presented simultaneously with two line drawings of a house: one undamaged house and one burning with flames and smoke coming out from its left side window. When asked whether the houses were identical or different, patients reported no differences; yet, when asked which house they would prefer to live in, they chose the undamaged house without being able to explain why.
Therefore, this study demonstrated that in patients with hemispatial neglect after right hemisphere damage, the brain does perceive the left hemispace but, due to a disruption in the pathway of that information to areas of the brain which enable its integration into consciousness, the patient does not perceive it. In other words, it is a failure in conscious processing of one half of the visual field and not some form of blindness.
Hemineglect affects mental representations of space
Hemineglect does not only apply to information from the external environment but also affects mental representations of space. In another classic experiment , when patients were asked to imagine being in a well-known square (the Piazza del Duomo in Milan) and to describe it, they only referred to details on the right side of the square and omitted those on the left side. To rule out memory problems, they were then asked to imagine standing at the opposite end of the square and to describe it from there: patients then described in detail what they had not previously been able to identify, omitting the details of the left side which had been previously described.
Hemi-inattention can also affect the body schema,that is, one side of one’s own body: this disorder is named hemiasomatognosia . When this occurs, people may apply make-up to only one side of the face, shave only on one side of the face, or bump into objects on their neglected side [3,4]
The most striking thing about hemi-inattention is that, in the most severe cases, the affected individual seems to have lost the concept of the left side. While in some cases, when the patient’s attention is directed towards an object located on the neglected or contralesional side, the patient can see and identify it without any problems ; in other cases, not even when encouraged to “look to the left “, can the patient understand what is meant by the person saying it .
Rehabilitation of hemineglect
One frequent method commonly used in the rehabilitation of hemineglect is to bring the patient’s attention continuously toward the side that he/she ignoresby standing on the patient’s left side, speaking from that side, and even arranging furniture in such a way that the person is forced to orient him/herself toward that sideat all times (e.g.: placing the bed against the wall on his/her non-neglected side). Therefore, it is also important to keep these considerations in mind during specific neuropsychological rehabilitation when performing attention tasks.