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Dan Lloyd

Brain Fiction: Self-Deception and the Riddle of Confabulation. William Hirstein. xii + 289 pp. MIT Press, 2005. $35.

"Know thyself," urged the inscription over the entrance to the temple of Apollo at Delphi, setting a goal for Western philosophy and many of the sciences it would ultimately spawn. Although nobody claims that self-knowledge is easy, certain basic facts about oneself seem direct and immediate: For example, I know whether I am now seeing properly, whether I am moving my arm, which of my thoughts are memories and which fantasies, and whether I am recognizing a familiar face. We are so intimate with these basic perceptual and cognitive capacities that it is difficult to imagine being wrong about such matters. Nonetheless, following brain injury even these simple insights can miscarry.

A patient with Korsakoff's syndrome, for example, reports that he spent the weekend at the beach, when in fact he was in the hospital. His memory is impaired, but he has replaced his lost history with a confabulation. However, he neither notices his amnesia nor questions his own story; concerning his own past, he doesn't know that he doesn't know. For another example, take the stroke patient who is paralyzed on her left side yet claims that she is not impaired, asserting that she is moving her immobile arm despite obvious evidence to the contrary. Even stranger, a patient with Anton's syndrome denies his own blindness, attributing his complete visual disability to "dim lighting" or poor glasses. A sufferer from Capgras's syndrome claims that her immediate family members have been replaced by impostors. And someone with Cotard's syndrome reports that he is dead and that everyone around him is dead too. These sincere claims are almost impervious to correction, even when the people making them are baldly confronted with the facts. Having someone point out the contradictions just generates more confabulations or, at best, temporary concessions.

Individually, paradoxical syndromes like these provoke case studies: The Man Who Mistook His Wife for a Hat and its successors popularized a venerable neurological tradition of rich description of particular individuals. A more difficult exercise is to seek commonalities among these bizarre syndromes and from there attempt to discern the underlying explanations in terms of brain function. In Brain Fiction, neurophilosopher William Hirstein has made this attempt.

Confabulation is a common expression of a variety of brain injuries, but of course not all lead to this symptom. Providing a general analysis of what confabulation is—its definition—is a fit task for a philosopher. Sorting through a huge literature on the causes of the confabulation syndromes, none of them simple, requires neurological experience and great effort, which Hirstein also brings to the task.

The confabulation syndromes, Hirstein suggests, reflect "knowledge deficits." Confabulators suffer from a derailment of processes by which we ascertain our beliefs about the world. Their brains produce fast and loose hypotheses but, crucially, fail to check them for accuracy. Instead, confabulators experience a "pathological certainty" that whatever springs to mind is simply true, despite overwhelming evidence to the contrary. Their inability to cross-check their beliefs blocks them from acknowledging how deeply flawed their claims are; accordingly, they can't perceive or even conceive their own deficits.

This plausible characterization of confabulation frames Hirstein's thorough review of the functional neuroanatomy of the syndromes. This is the real riddle, and generations of study by neuroscientists have produced a bewildering array of clues and suggestions, which Hirstein bravely reviews. A prime suspect is the orbitofrontal cortex, just over our eyes, which is impaired in Korsakoff's syndrome and by aneurysms of the anterior communicating artery, two routes to confabulation. Perhaps this is where the cerebral cross-check normally occurs?

There are two immediate problems with locating this basic epistemic function just here, behind the forehead. First, like every other area of the brain, the orbitofrontal region is mutually innervated by many other parts of the brain, so its disruption will also interfere with a number of circuits and perhaps compromise the normal function of several brain areas. Second, what is this operation of "checking"? Hirstein vaguely characterizes checking at different points in the book but notes that certain kinds of representations are often in play: Frequently confabulators misrepresent the minds of other people. At one extreme, loved ones are replaced by impostors—that is, perceptual identity is trumped by a dislocated representation of the mind of the other. Or, in Cotard's syndrome, the very idea of mind seems blotted out—oneself and others are "dead," "empty."

Dramatic mental failures of this sort shade into failures of empathy, a deficit found in many sociopaths, who also show reduced function of the frontal cortices. They and others with such neurological damage are socially disinhibited. For Hirstein this kind of inappropriate behavior is on the same spectrum as the epistemically inappropriate statements made by Korsakoff's patients. Finally, at the anticonfabulatory extreme is a mirror syndrome, obsessive compulsive disorder. If confabulators suffer from pathological certainty, then OCD patients suffer from pathological doubt; accordingly, their frontal lobes are abnormally overactive.

As an aside, I might note that "hypofrontality" is also frequently observed in schizophrenia (although Hirstein does not develop this connection). Schizophrenic delusions seem more fixed in content than typical confabulations, which are jury-rigged on the fly. This difference may point to disruption in ongoing learning processes in schizophrenia, arising through the abnormal function of otherwise normal, intact circuits. Perhaps these same circuits are offline in the confabulation syndromes, and as a result patients can't really learn or remember their confabulated claims.

Insult to the frontal lobes is not the only cause of confabulation, and two other conditions stretch the orbitofrontal hypothesis. Parietal lobe damage, especially to the right side, produces hemi-neglect, the puzzling disappearance of the left half of the patient's world. The lost left includes the left side of the body, which is paralyzed following these lesions. Yet patients often deny this paralysis and confabulate in response to the request to move the affected arm. Sometimes they even deny ownership of the arm. This occurs in spite of an intact frontal lobe, leading Hirstein to implicate parietal areas in a circuit that includes the frontal cortex. The parietal insult knocks this network offline, disabling the frontal fact-checker in exactly the domain of body and spatial representation that would normally be served by the lost region.

Severing the connections between the hemispheres also occasions confabulation. In an appropriate experimental context, stimuli can be channeled just to the isolated right hemisphere, and it can respond solo (with a movement, rather than words, because this hemisphere is generally mute). When the split-brain subject is asked why she did what she did, the talky left hemisphere confabulates a motive rather than admit ignorance. This observation leads Hirstein to conjecture that the left orbitofrontal cortex by itself is insufficient to curtail confabulation. Bilateral function is somehow required.

Although Hirstein strives to account for confabulation with a single mechanism, the maze of clinical and anatomical data he reviews strongly suggests that at the neural level there are different derailments, depending on the type of brain injury. Confabulators, after all, remain rational in domains outside of the foci of their various syndromes, in contrast with more global breakdowns found in schizophrenia or dementia. Thus perceptual cross-checking may be domain-specific and not localizable in a single region, circuit or system in the brain, in which case the explanations of confabulation would vary accordingly.

The book concludes with a chapter on self-deception, which Hirstein says is analogous to confabulation. In many familiar ways we can divert our attention from the checks and censors that might interfere with our most cherished beliefs; in effect we're interfering with our own frontal functioning. And so we should, he says:

The truth is depressing. We are going to die, most likely after illness; all our friends will likewise die; we are tiny insignificant dots on a tiny planet. Perhaps with the advent of broad intelligence and foresight comes the need for confabulation and self-deception to keep depression and its consequent lethargy at bay. There needs to be a basic denial of our finitude and insignificance in the larger scene. It takes a certain amount of chutzpah just to get out of bed in the morning.

Like many books, Brain Fiction is ultimately an illustration of its own thesis. Faced with diverse and inconclusive evidence, its author makes some optimistic selections and conjectures. Readers may find their orbitofrontal cortices saying "Whoa" to some of Hirstein's more general claims. But it is only when all the confabulation syndromes are scrutinized together that their tantalizing inconsistencies emerge. Hirstein's synoptic review gathers many of the clues, making it an excellent starting point for thinking about the biological mechanisms that help us make sense of the world. Personally, I welcome an author ready to go out on some interesting limbs more than one who hugs the trunk of proof. Or maybe I'm kidding myself.

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