| Niznikiewi-cz et al., 200425
|
17 right-handed women diagnosed with schizotypal personality disorder according to DSM-III-R (mean age: 40.7 years; mean IQ: 110), and 16 healthy women (35.8 years; mean IQ: 117.7). All native speakers of English. |
To study the role of context in semantic processing in women with schizotypy using the paradigm of N400 potential. |
200 sentences of 5 to 8 words were presented visually and auditorily to the participants, who were monitored using EEG. Half of the sentences ended with a word that fit the context and the other half ended with a word that did not fit the context. Participants should decide on the meaning of each sentence. |
N400 amplitudes were more negative in women with schizotypy, a difference limited to sentences with congruent ends presented auditorily. |
| Folley & Park, 200531
|
17 outpatients with schizophrenia (29% female, mean age: 39.5 years), 17 healthy controls (47% female, mean age: 35.2 years) and 17 individuals with schizotypy (47% female, mean age: 22.8 years), recruited from the community, 10 from each group were evaluated with spectroscopy. |
To assess whether schizotypy is associated with increased creativity and to elucidate the neural correlates of divergent thinking using infrared spectroscopy. |
After psychopathology, schizotypy and intelligence assessments, participants performed creativity tasks. |
High schizotypy was associated with higher divergent thinking, which was additionally related to the disorganization dimension of schizotypy, as well as bilateral activity in the PFC. When compared with the other groups, individuals with schizotypy recruited PFC preferentially. |
| Kiang & Kutas, 200516
|
24 students, native English speakers (17 female, aged 18 to 35 years). |
To study the association between schizotypy and the activation of semantic networks using the SP paradigm and N400 potential. |
While monitored by EEG, participants viewed terms that defined a semantic category followed by high-typicality exemplars (e.g., fruit/ apple), low-typicality exemplars (e.g., fruit/ cherry) or unrelated words (e.g., fruit/clamp) and were asked whether the word was or was not an exemplar of a given category. |
Among all participants N400 amplitude was more negative for unrelated terms and less negative for high-typicality and low-typicality exemplars. The higher the schizotypy score, the lower the N400 amplitude to non-exemplars, and the higher the N400 amplitude both to high- and low-typicality exemplars. |
| Mohr et al., 200527
|
40 healthy right-handed men, recruited from the general population, with a mean age of 25 years and mean education of 16.93.2 years. |
To test the effects of dopamine on the hemispheric processing of language using a simple lexical decision test. |
Double-blind study; participants received levodopa or placebo 30 minutes before undergoing a lexical decision test. This test consisted of the presentation of pairs of 4-letter sequences alternately to their visual fields. The sequences were: word/non-word; non-word/word, non-word/non-word). Participants had to indicate whether a meaningful word was presented. |
The authors suggest that in healthy brains dopaminergic agonists restore LH dominance for language, by reducing RH activity with respect to positive schizotypal traits. |
| Tsakanikos & Reed, 200530
|
80 students (48 women, mean age: 20.2 years). |
To study event detection bias using a word detection paradigm in short animations. |
Each participant received 64 trials of a continuous sequence of brief animated images, half of which contained a word hidden between non-words, whereas the other half contained only non-words. They were asked to ignore the non-words and read aloud any words they could see. |
Positive schizotypal traits were associated with a trend to report words that did not appear in the trials. |
| Kiang & Kutas, 200614
|
60 students, native English speakers (34 women, aged 18 to 35 years). |
To study the anomalous production of language in schizotypy by examining the typicality of responses to the Category Fluency Test (CFT), as well as the correlation between schizotypy and the total number of responses on the CFT. |
Participants were asked to generate as many names of fruits, four-footed animals, articles of clothing and vehicles as they could within 1 minute. Correlations were analyzed between schizotypy and the probability of a typical first response, the typicality of responses and the number of responses on the CFT. |
High scores in the SPQ (total and subscales) were significantly correlated with a lower chance of a first typical response, but only for the fruit category. High SPQ global scores and in the interpersonal and disorganization subscales were significantly correlated with more atypical responses, but also only in the fruit category. There was no significant association between schizotypy and the total number of responses on the CFT. |
| Morgan et al., 200618
|
251 students, native English speakers; selection of 26 with high scores for schizotypy (20 women; mean age: 21 years), and 32 with low scores for schizotypy (13 women; mean age: 21 years). |
To investigate alterations in SP in schizotypy and whether they may result from problems in automatic or controlled semantic processing, or in semantic storage. The authors also examined the association between different factors of schizotypy and deficits in SP. |
Related and non-related target-prime pairs along with pseudo-prime-target pairs of variable frequency were presented at a short (200ms) and a long SOA (750ms). Participants had to indicate whether a word was a real word or a non-word. |
The group with high schizotypy showed higher scores on the PDI. Moreover, this group showed less priming at a short SOA. Individuals with low schizotypy had higher priming at long SOA. Priming effects in individuals with high schizotypy correlated positively to unusual experiences, but only at a long SOA. |
| Johnston et al., 200819
|
54 students, native English speakers (41 women; mean age: 22.5 years). |
To study semantic processing in schizotypy using direct and indirect SP and different SOA durations. |
Performance on SP was measured by reaction times to prime-target pairs. |
There was a significant correlation between the cognitive disorganization subscale of the O-Life and indirect priming with total and shorter SOA durations. In the group of women, there were no significant correlations between cognitive disorganization and priming effect, whereas a robust correlation between cognitive disorganization and indirect priming with shorter SOA was found in the group of men. |
| Hori et al., 200826
|
32 healthy volunteers (22 women, aged 22 to 59 years). |
To investigate possible associations between schizotypy, lateralization, and typicality of responses on a verbal fluency test, using infrared spectroscopy. |
Participants initially grouped as high and low schizotypy were evaluated using infrared spectroscopy while performing tasks of word generation out of certain syllables (phonological verbal fluency) and semantic categories (semantic verbal fluency). |
Subjects with high scores on schizotypy showed greater activation of RH during phonological verbal fluency. The same association was not found for the semantic verbal fluency test. There was no association between schizotypy, laterality and typicality of responses in the semantic task. |
| Hori et al., 200829
|
27 right-handed female volunteers (aged between 20 and 59 years), recruited from the general population were grouped into high (n = 14) and low schizotypy (n = 13). |
To study the association between schizotypal traits and patterns of activation of the PFC during a verbal fluency test using infrared spectroscopy. |
Participants had to generate and verbalize words out of syllables provided by researchers. |
Schizotypal traits in healthy women were associated with abnormal patterns of PFC activation during verbal fluency, but the number of words generated was not different in the 2 groups. Most strikingly, the group of women with high schizotypy had larger right PFC activation. The SPQ subscale of unusual perceptual experiences was associated with PFC activation during verbal fluency test. |
| Morgan et al., 200920 |
251 students, native English speakers; 26 with high scores for schizotypy (20 women; mean age: 21 years), and 32 with low scores for schizotypy (13 women; mean age: 21 years) were selected for the study. |
To study explicit semantic processing in individuals with high scores on schizotypy using an extensive battery of semantic tasks. |
The authors evaluated the performance of individuals with high scores on a schizotypy dimension robustly associated with positive symptoms in 7 different measures of explicit semantic processing. |
Only one of the semantic processing measures, the semantic categorization, was significantly impaired in high schizotypy, particularly for low-frequency words. Such deficits are most consistently associated with the cognitive disorganization subscale of the O-Life. |
| Asai et al., 200922
|
46 students (33 women, aged 18 to 21 years). |
To study the association between schizotypy and brain lateralization in 2 separate experiments, one assessing motor performance and cerebral asymmetry, and the other, included in this review, assessing cerebral asymmetry and language through a go/no-go paradigm. |
Participants received spoken stimuli, which consisted of real or ungrammatical words and were asked to press a button as quickly as possible only after hearing meaningful words. |
Positive schizotypal traits were associated with non-lateralization of semantic processing. Participants with high schizotypy also responded to semantic auditory stimuli with both hands and showed a strong ipsilateral effect. |
| Kiang et al., 201015
|
28 students (15 women; mean age: 19.7 years), native speakers of English. |
To study SP in schizotypy. |
The authors studied N400 amplitude elicited from individuals reading word pairs that were strongly or weakly associated, as well as not associated, at varying SOA durations (between 300 and 700 ms). |
Among all participants, N400 amplitudes to target words were higher for non-associated words and lower for strongly and weakly associated words. Higher SPQ total scores correlated significantly with lower indirect N400 priming effect at both SOA. Higher scores for cognitive-perceptual factors also correlated significantly with lower direct N400 priming effects at both SOA, as well as lower indirect N400 priming effect at a 300ms SOA. |
| Grimshaw et al., 201023
|
60 students selected from group of 300: 30 with high schizotypy (7 men; mean age: 18.6) and 30 with low schizotypy (10 men; mean age: 20 years), all native English speakers. |
To study the resolution of semantic ambiguity in individuals with high and low schizotypy considering inter-hemispheric differences in semantic processing. |
Individuals performed a test of semantic ambiguity, in which they had to indicate whether pairs of words were related or not. The first word (prime) was ambiguous (e.g., ball) and the second could be either related to the dominant sense of the prime (i.e., round) or to a subordinate meaning (e.g., dance). Response time was used as a measure of performance in the test. SOA was 750 ms because the authors believe that this interval may lead to major inter-hemispheric differences in SP. |
The group with low scores on the SPQ showed priming for dominant meanings and negative priming for subordinate meanings. The group with high schizotypy demonstrated priming for dominant meanings, but neither priming, nor negative priming for subordinate meanings. The authors suggest that the patterns of semantic ambiguity resolution found in the 2 groups reflect differences in inter-hemispheric participation in semantic processing, as the individuals in the high schizotypy group seem to activate the RH preferentially, whereas in the low schizotypy group, the LH. Or, alternatively, that there are deficits in inhibiting the RH in individuals in the high schizotypy group. |
| Prévost et al., 201028
|
49 right-handed individuals, native speakers of French or English (35 women, aged 18 to 51 years). |
To study the associations between N400 potential and schizotypy disorganization, proneness to delusions and interpersonal deficits using a semantic task. |
First, participants were shown the words animal or inaction; after a SOA of 2 s, distinct stimuli were presented. After that, individuals were asked to decide whether such targets corresponded or not to the animal category. |
Potential N400 correlated significantly only with interpersonal and disorganization traits. The lack of correlation between N400 and positive traits suggests that the mechanisms of delusion-like belief formation on healthy individuals scoring high on SPQ might differ from those observed in schizophrenia. |
| Kostova et al., 201121
|
50 right-handed students, native speakers of French, aged 18 to 45 years (35 women). |
To individualize RH and LH styles of semantic processing in a task of understanding pairs of auditory sentences presented binaurally. |
Sentences were presented binaurally to individuals with high and low schizotypy. The last word of each sentence (the semantic target) was presented monaurally. Participants had to identify the semantic compatibility of the targets. |
Low schizotypy subjects exhibited a classic semantic compatibility effect in both hemispheres. High schizotypy subjects did not show right ear-LH semantic compatibility effect or right ear-LH activation of semantic memory, although their RH response was similar to that of individuals with low schizotypy. |
| Debruille et al., 201317
|
47 right-handed volunteers from the general population, native speakers of English or French (34 women, aged 18 to 49 years). |
To investigate whether decreases in psychotic symptoms may be associated with a direct effect of an atypical anti-psychotic on anomalous semantic activations, by observing the effects of olanzapine on N400 potential during a semantic categorization task. |
Double-blind study in which 2 groups of participants received 2.5 mg of olanzapine or placebo, alternately, on 2 occasions, before performing semantic categorization tasks while N400 potential was recorded. SOA duration was 2 s. |
In the placebo group, N400 had larger amplitude in high schizotypy. Olanzapine reduced N400 amplitude only in individuals with high schizotypy, an effect that did not depend on anxiety, mood, energy, or side effects of olanzapine. |
| Wang et al., 201324
|
49 individuals: 17 with stable schizotypy (10 women; mean age: 21to 24 years), 15 with unstable schizotypy (8 women; mean age: 20 years) and 17 with no schizotypal traits (11 women; age: 20 to 47 years). |
To study the neural components of semantic processing in individuals with schizotypy using N400 potential and differences between implicit and explicit semantic processing, and to examine whether such processing is stable or may vary according to schizotypy. |
SP tasks differed only in the duration of the SOA: 300 ms in the implicit task; 700 ms in the explicit task. |
Individuals with schizotypal traits had normal implicit semantic processing and impairment on explicit semantic processing. Such impairments remained stable despite variations on schizotypy over time. |
