God Soul Mind Brain

even when it was directly in front of her and she was looking at it. But when asked to reach out and pick up the object, her hand correctly shaped to grasp the object. Her action stream “knew” about the object’s shape, and used that knowledge to put her fingers in the right positions as her hand approached the object, but that information was not available for conscious report.

    The pattern of results found by Goodale suggests that the action stream can function independently of consciousness. Any consciousness circuitry, if such a thing exists, receives signals flowing out of the lower streams but evidently not as much out of the action stream. This finding could be said to be the first clue, the initial hint that the social regions of the brain may be important in conscious awareness. Area STP is unique in the lower streams in that it receives and combines signals from all of them. It stands at an apex in the processing of object location, object motion, and object shape, receiving the types of visual signals that normally reach our consciousness.

Spatial Neglect

    One of the strangest syndromes that occurs with brain damage in humans is called spatial neglect. Neglect usually occurs with damage to the right side of the brain, often caused by a stroke. For weeks after the stroke, sometimes much longer, the patient has no awareness of the left side of space. The loss of awareness is profound and complete. A patient will deny the existence of anything to his left. He will even deny the presence of empty space to his left. He can see objects on his left in a mechanical sense - he might flinch when an object is about to hit him from that direction - but he will deny any conscious awareness of it. He may draw a clock with the numbers crushed into the right side of the dial. He may eat everything on the right side of his plate and leave the rest untouched. He might even shave the right side of his face and think he’s done. The patient typically does not acknowledge any peculiarity in his behavior. This lack of insight is not surprising, given the symptoms. Awareness of his mistake is impossible because all awareness of the left side of space is gone.

    Although neglect has been studied for more than half a century, the exact location of the damage in the brain that causes neglect is not yet absolutely certain. One reason for the uncertainty is that strokes tend to damage large, messy areas of the brain. Even if a patient with spatial neglect is scanned in an MRI, and the damaged area is mapped precisely, it is never clear where in that large dead region lies the critical tissue related to neglect. A second reason why neglect is difficult to pinpoint is that the syndrome itself may come in several varieties tied to different brain areas.

    Yet careful, modern studies of neglect (the work of neuroscientist Vallar and his colleagues comes to mind), comparing the damaged brain areas in many people and attempting to find the smallest region of overlap, have honed in on a region of the brain that may be an epicenter of neglect: Area TPJ on the right side of the brain. (In Figure 6-3 of the monkey brain, the corresponding area may lie roughly in the angle between 7A and STP. Area TPJ has not been extensively studied in monkeys.) In the human brain, according to the scientists Saxe and Kanwisher, TPJ especially on the right side of the brain is consistently active when people engage in social cognition—in reconstructing the contents of other people’s minds.

    Is TPJ involved in an awareness of space and of the objects arrayed around the body, as suggested by the experiments on spatial neglect? Or is TPJ involved in perceiving the mind-states of other people, as suggested by the experiments on social perception and cognition? For that matter, recalling Blanke’s experiments that I mentioned in Chapter 4, why does electrical stimulation of TPJ disrupt your self-model, sometimes resulting in the misperception that your own conscious mind is hovering in a place outside your body? The bizarre disconnect between these seemingly unrelated symptoms and functions has led to a certain amount of controversy. Scientists love a good fight. One possible resolution to the fight is that the functions are deeply connected. The same machine in your brain that constructs a perceptual model of other people’s minds, of the contents of other people’s awareness, may be necessary to compute a perceptual model of your own mind