NARSAD Scientist Advances Explanation for Disordered Thinking in Schizophrenia

[ italics in brackets are mine; DHY ] (Boston, MA - June 14, 2008) — According to NARSAD scientist Dean F. Salisbury, Ph.D., problems at two distinct stages of language processing may explain the disjointed thinking seen in schizophrenia. By tracing individuals’ brainwaves as they read words with multiple meanings, he and his colleagues found that people with schizophrenia made inappropriate associations with weakly related concepts, but memory deficits later made them default to the typical meaning of words even when the context pointed to an alternative meaning.

People with schizophrenia often veer off on tangents during conversations, confuse figurative with literal expressions, and lose their train of thought mid-sentence. Studying how they process language has occupied Dr. Salisbury, of Harvard Medical School and McLean Hospital, and his colleagues for years. “Thought disorder may be related to a singular cognitive abnormality, but it is not known where in the information processing stream the abnormality occurs or how it arises,

Ambiguity equals opportunity

To track that processing stream, scientists study responses to homographs, words that carry more than one meaning, like “palm”. Some experts think that deciphering meaning involves searching networks of nodes that dwell in memory, where each node represents a concept. Perceiving a word seems to spread activation among nodes representing related concepts along paths that are guided by contextual cues. In an article about California landscaping, people associate “palm” with a kind of tree and, more distantly, with plants; in the presence of a fortune-teller, they make different associations and comprehend a different meaning.

This process seems to break down in people with schizophrenia, causing misinterpretations that scientists can probe for hints to how the illness hobbles the brain. “Schizophrenic error patterns are likely not random,” Dr. Salisbury wrote. Although controversial, some theories suggest a “semantic bias” in people with schizophrenia that favors the dominant, or most common, [ or simplest ] interpretation of a word even
when its clashes with contextual cues, causing them to misconstrue “toast” as browned bread even in a conversation about a wedding reception.
This could stem from overactivation within the network.
Other theories blame faulty higher-order processes such as attention.

In a series of studies by Dr. Salisbury and colleagues, participants with and without schizophrenia read sentences, each of which contained a homograph as well as a related or unrelated word. Meanwhile, electrodes recorded a brainwave called the N400 event-related potential to see if priming had occurred. In priming, a conceptually related word that precedes a homograph speeds its processing; for instance, “lime” primes “lemon.”
As Dr. Salisbury explained, “The N400 is smaller when priming has occurred.”

[ preparing cp the crossword puzzle situation ]

In one study by Dr. Salisbury’s research team, participants read four-word sentences.
Each included a homograph and ended with a word that clarified its meaning, with a long interval between them. Compared to the control group, participants with schizophrenia showed greater N400s to sentences that conveyed less typical meanings. According to Dr. Salisbury, a semantic bias kept them from correctly gauging the meaning from the context.
People without schizophrenia tend to respond in a graded way to these kinds of tasks,
with N400s that range from large for unrelated words, to midsize for rare associated meanings, to small for strong associates.
In contrast, the study found that people with schizophrenia responded to all sentence endings with a larger N400.
That could reflect a failure to pay attention, but a follow-up study ruled out that explanation, leading the researchers to suspect poor processing of contextual information. [ ?They are stuck on the matter; still organising its priority?

Activation versus memory

Another study asked participants to decide whether two words were related. To detect where language processing breaks down, it varied the time between the homograph and cue word. Shorter intervals reveal the early spread of activation among concepts; longer ones offer a glimpse of verbal working memory.
At quick presentation rates, people with schizophrenia showed a reduced N400 to unrelated words, indicating inappropriate priming of homographs by distantly related contexts. At longer intervals, they showed larger N400s than controls regardless of how closely the words were related. Dr. Salisbury attributed this to problems with holding contextual information in verbal working memory.

Taken together, these findings point to double trouble in schizophrenia.

Early in language processing, excessive priming [ rehearsal; maybe it cannot be set aside ] spreads activation farther than normal through the network.
After that, item representations in working memory fade so fast that, after one second, Dr. Salisbury wrote, “only the most strongly associated concepts will remain in the buffer, creating a bias, that hampers the use of contextual cues.

These conclusions set the stage for further efforts to clarify the memory deficits that underlie thought disorder in people with schizophrenia.

[ Comment ... what decides the strength of will - what to attend to, and what to discard.
Where the 'sufferer' exercises purpose which comes from within - e.g behaving so that you are not sectioned nor admitted, prospective 'patients' can withhold illness behaviour.
Again, where there is clear and defined purpose - going in to Tesco to buy a bed sheet, patient has no difficulty in asking a staff for direction, choosing and paying.

It is likely that to re-introduce activities outside the domicile - to provide meaningful breaks and carer time - it is easier to choose those subjects and topics of interest, hope, and ambition that were there before the illness - because there will already be 'priming' and strong networking nodes ?? ]

A daily routine provides a structure to the day and to the memory bank by repetition. This structure reduces unresolved and building anxiety from not knowing what comes next - one thing that brings out active illness. The other arangement that similarly reduces the anxiety, arising from uncertainty, is to know what you are going to do in the week ahead, and have some idea what lies in store in the future, ahead of the need to make a decision.

Where there is an established external framework of activity involvement [ sheltered work. educational opportunity made accessible to the sufferer, interest pursuits .. etc ] , memory stores whatever these commitments entail, are continually rehearsed as a commitment. The context to what is needed, is then more easily 'woken up' to what will be an requird to engage back to schizophrenia basic ideas

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