Explain what it means that disorganized thoughts may result from a breakdown in selective attention

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Kraepelin said severe mental illness was due to 2 diseases subsequently characterized as disorders of thought vs disorders of mood, ie, the Kraepelinian dichotomy. Schizophrenia, traditionally considered the disorder of thought, has been defined by the presence of hallucinations, delusions, catatonia, and disorganization. Tangentiality, derailment, loose associations, and thought blocking are typically considered pathognomonic of schizophrenia. By contrast, the mood disorders have been characterized only as disorders of the emotions, though both depression and mania, when severe, are now recognized to include the same psychotic features traditionally considered diagnostic of schizophrenia. This article addresses disordered thinking in mania in order to clarify the relationship between schizophrenia and psychotic mood disorders. Normally, the brain's selective attention mechanism filters and prioritizes incoming stimuli by excluding from consciousness extraneous, low-priority stimuli and grading the importance of more relevant data. Because this "filter/prioritizer" becomes defective in mania, tangential stimuli are processed without appropriate prioritization. Observed as distractibility, this symptom is an index of the breakdown in selective attention and the severity of mania, accounting for the signs and symptoms of psychotic thinking. The zone of rarity between schizophrenia and psychotic mood disorders is blurred because severe disorders of mood are also disorders of thought. This relationship calls into question the tenet that schizophrenia is a disease separate from psychotic mood disorders. Patients whose case histories are discussed herein gave their written informed consent to participate in this institutional human subjects committee-approved protocol.

Fig. 1.

Selective Attention in Mood Disorders:…

Fig. 1.

Selective Attention in Mood Disorders: Mania. In mania, the subject of “mom” is…

Selective Attention in Mood Disorders: Mania. In mania, the subject of “mom” is inappropriately lost when stimulus 2, the “keys”, is passed through the filter and prioritized, possibly due to it being the most recent stimulus. The keys idea is not verbalized because of a flurry of sequential internal stimuli based initially on keys and then on subsequent internal stimuli (see text). This series of internal stimuli includes items 3–9. Stimulus 7 is shown as a dashed line of external input because the room may have been warm. Only 5 and 9 are verbalized. Although there are connections to each thought based on the patient's report, the failure to filter and prioritize causes stimuli to come so fast and demand attention (apparently based on most recent order) that there is not enough time to verbalize all of them. An observer hears only “mom,” “pyramids,” and wanting water, concluding there has been a “blockage of thought.” The present explanation is predicated on the core manic symptoms of distractibility, flight of ideas, and racing thoughts. Manic thought is indeed disordered. The potentially critical external stimulus of “smoke” (item 10) may pass the filter but may not be adequately prioritized in mania to receive action. “Smoke” may be quickly overridden by the next stimulus such as “cigarettes are expensive” or “Smokey the Bear is cute.” The first 9 stimuli are actual thoughts of the patient as discussed in the text; stimulus 10 is hypothesized. This exchange and series of thoughts might occur in as little as 1 minute. Three areas of central nervous system data processing are denoted by each set of 3 boxes, each set representing 1 of 3 states of mood. The examples of the stimuli used in the figure derive from an actual patient interview during a student case conference (see text). Represented by the first box in each of the 3 sets, external stimuli appear to meet a filter that eliminates trivial data in euthymia while most or all stimuli pass through the filter in mania. Excessive stimuli may be stopped at the filter in depression. Internal stimuli are shown but their filtration is not indicated in the figure. Represented by the middle boxes, a second data-processing mechanism is a prioritizing function that can rearrange the importance of stimuli, diminishing or exaggerating attention to incoming data. The third boxes in each set represent action or verbalization. The time elapsed during processing of the interview material differs among mood states. In euthymia, the 8 stimuli take 2–5 minutes; the 10 stimuli in mania, less than a minute and 5 steps in depression, 5–10 minutes.

Fig. 2.

Selective Attention in Mood Disorders:…

Fig. 2.

Selective Attention in Mood Disorders: Euthymia. In euthymia, the psychiatrist's questions about “mom”…

Selective Attention in Mood Disorders: Euthymia. In euthymia, the psychiatrist's questions about “mom” are prioritized and are not overridden by the “keys” (neither of the 2 keys stimuli 1 or 2) or by miscellaneous stimuli, 1 or 2. The first “keys (1)” stimulus is impactful enough to pass the filter but is shown as downgraded by the prioritizer function (second box), and there is no action or verbalization. A second “keys (2)” stimulus when the professor picked up his keys does not pass filtration. Internal stimulus 4 (mom 2) and external stimulus 6 (“mom 3” as in the form of another question from the interviewer) are appropriately prioritized and verbalized in continuing with the psychiatric interview. The dialogue about the topic of “mom” may last 5 minutes and is only overridden by a hypothetical stimulus, “smoke.” The sight or smell of smoke (stimulus 7) readily passes the filter and is highly prioritized. Note increase in line thickness and elevation to the top of the “action” box, receiving immediate attention above the “mom” topic.

Fig. 3.

Selective Attention in Mood Disorders:…

Fig. 3.

Selective Attention in Mood Disorders: Depression. In depression, all cognitive processes appear to…

Selective Attention in Mood Disorders: Depression. In depression, all cognitive processes appear to be slowed. A depressed patient may have difficulty maintaining focus on “mom” not because of subsequent interrupting stimuli but because of a defect in concentration associated with depression. Other stimuli may be inappropriately filtered out or receive an unwarranted reduction in prioritization. Stimulus 5, “smoke,” is shown as passing the filter but not receiving a high enough prioritization rank to produce an action. No internal stimuli are generated, in sharp contrast to the manic state where an excessive number of internal stimuli reach consciousness. In depression, only 5 stimuli may require 5–10 minutes with less comprehension than 8 stimuli in euthymia in the same time.

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