An experimental design may be a thing of beauty.
In 1978, Edoardo Bisiach and Claudio Luzzatti1 published a study that was both simple and elegant. Their article also taught us something new about the relationship between a person’s perception of the external world and how that same person discerns the world mentally—conjured up in memory, as a “mental representation.”
For psychiatrists, the concept of “mental representation” has great significance because it is a crucial component of theories about empathy, learning, identification, internalization, creativity, self-reflection, and more. For example, the psychological theory of mentalization describes a relational process by which individuals may develop the capacity to form mental representations of the minds of others. According to this theory, mentalization also contributes to an individual’s concept of self. In attempting to grasp the myriad of interacting neurological systems that might underlie a complex, theorized process such as mentalization, it is revealing to look first at a much simpler aspect of mental representation.
In that context, we turn to Bisiach and Luzzatti’s study of mental representation in the visual realm. There were only 2 patients in this study.
I. G. was an 86-year-old woman, a retired manager. N. V. was a male lawyer, aged 72. Both had had right-sided strokes involving the right temporoparietal region. They presented with physical findings that were unremarkable for such a condition and, in addition, both patients had unilateral neglect.
Individuals with unilateral neglect do not respond to stimuli from one side of their environment—generally the left. Normally, we distribute attention to the world around us and locate the source of stimuli, creating a mental map of external space that is body-centric. In unilateral neglect, stimuli that come from the patient’s left side are neglected, whichever way the patient’s body happens to be oriented in space.
Think of a hospitalized patient who is served lunch on a tray. The patient with unilateral neglect, for example, might eat all of the potatoes and broccoli from the right side of his plate but leave the chicken untouched. This would not be because the patient does not like chicken. It would be because the chicken was on the left side of the plate. If a helpful visitor rotated the patient’s plate by 180 degrees, then the patient would eat the chicken because now he would know that it was there.
Unilateral neglect is not a simple sensory deficit. When individuals have a sensory deficit, such as a visual field cut, they naturally compensate by moving their heads to take in all of their surroundings. Unilateral neglect involves all of the sensory realms, although this study only set out to explore the visual modality.
The question that interested Bisiach and Luzzatti was about the mental life of I. G. and that of N. V. Both of these patients had unilateral neglect of the external world, but what of their interior world? To put this another way, even though individuals with unilateral neglect do not notice the left side of their plates in the external world, the question was whether, in their mental world, in the world of their memories, in their mental representations of the external world, they could still conjure up the whole plate? Were they simultaneously aware of potatoes, broccoli, and chicken? How could this question be answered? Here is where Bisiach and Luzzatti’s experimental design-genius is revealed.
Dr Schildkrout is Assistant Clinical Professor of Psychiatry, part-time, at Harvard Medical School, Beth Israel Deaconess Medical Center, in Boston. She is Chair of the Neuropsychiatry Committee of the Group for the Advancement of Psychiatry and author of two books, Unmasking Psychological Symptoms: How Therapists Can Learn to Recognize the Psychological Presentation of Medical Disorders and Masquerading Symptoms: Uncovering Physical Illnesses That Present as Psychological Problems. She reports no conflicts of interest concerning the subject matter of this article.
1. Bisiach E, Luzzatti C. Unilateral neglect of representational space. Cortex. 1978;14:129-133.
2. Sacks O. An Anthropologist on Mars: Seven Paradoxical Tales. New York: Alfred A. Knopf, Inc; 1995.
3. Rode G, Cotton F, Revol P, et al. Representation and disconnection in imaginal neglect. Neuropsychologia. 2010;48:2903-2911.
4. Marshall JC, Halligan PW. Whoever would have imagined it? Bisiach and Luzzatti (1978) on representational neglect in patients IG and NV. In: Code C, Joanette Y, Lecours AR, Wallesch CW, eds. Classic Cases in Neuropsychology. East Sussex, UK: Psychology Press; 2003:257-277.