Why all the confusion? Experimental task explains discrepant semantic priming effects in schizophrenia under “automatic” conditions: Evidence from Event-Related Potentials

Abstract

The schizophrenia research literature contains many differing accounts of semantic memory function in schizophrenia as assessed through the semantic priming paradigm. Most recently, Event-Related Potentials (ERPs) have been used to demonstrate both increased and decreased semantic priming at a neural level in schizophrenia patients, relative to healthy controls. The present study used ERPs to investigate the role of behavioral task in determining neural semantic priming effects in schizophrenia. The same schizophrenia patients and healthy controls completed two experiments in which word stimuli were identical, and the time between the onset of prime and target remained constant at 350msec: in the first, participants monitored for words within a particular semantic category that appeared only in filler items (implicit task); in the second, participants explicitly rated the relatedness of word-pairs (explicit task). In the explicit task, schizophrenia patients showed reduced direct and indirect semantic priming in comparison with healthy controls. In contrast, in the implicit task, schizophrenia patients showed normal or, in positively thought-disordered patients, increased direct and indirect N400 priming effects compared with healthy controls. These data confirm that, although schizophrenia patients with positive thought disorder may show an abnormally increased automatic spreading activation, the introduction of semantic decision-making can result in abnormally reduced semantic priming in schizophrenia, even when other experimental conditions bias toward automatic processing.

Association of abnormal semantic processing with delusion-like ideation in frequent cannabis users: an electrophysiological study

“…In contrast, a few other schizophrenia studies have found smaller than normal N400 amplitudes to contextually related targets and increased N400 relatedness priming effects (Kreher et al 2009;Kreher et al 2008;Mathalon et al 2002;Salisbury 2008). However, these latter data appear to be specific to short primetarget stimulus-onset asynchronies (SOAs; i.e., the time interval between the onsets of the two stimuli) of <300 ms, weakly related targets, and patients with disorganized speech and are thus suggestive of rapid automatic priming of weakly associated concepts in this subset of patients (Ditman and Kuperberg 2007;Kreher et al 2009;Salisbury 2008). On balance, however, N400 studies of schizophrenia patients provide evidence of a general reduction in semantic priming, at least at SOAs of approximately 300 ms or greater, during which more controlled or strategic cognitive processing is normally thought to occur.…”

“…Numerous studies have found evidence for larger (more negative) than normal N400 amplitudes in response to contextually related items, and smaller than normal N400 semantic priming effects, in schizophrenia (Condray et al 2003;Condray et al 2010;Ditman and Kuperberg 2007;Kiang et al 2011;Kiang et al 2008;Kostova et al 2005;Kostova et al 2003;Laurent et al 2010;Mathalon et al 2010;Ohta et al 1999;Salisbury 2010;Salisbury 2008;Strandburg et al 1997). In contrast, a few other schizophrenia studies have found smaller than normal N400 amplitudes to contextually related targets and increased N400 relatedness priming effects (Kreher et al 2009;Kreher et al 2008;Mathalon et al 2002;Salisbury 2008). However, these latter data appear to be specific to short primetarget stimulus-onset asynchronies (SOAs; i.e., the time interval between the onsets of the two stimuli) of <300 ms, weakly related targets, and patients with disorganized speech and are thus suggestive of rapid automatic priming of weakly associated concepts in this subset of patients (Ditman and Kuperberg 2007;Kreher et al 2009;Salisbury 2008).…”

Test–retest reliability of N400 event-related brain potential measures in a word-pair semantic priming paradigm in patients with schizophrenia

“…In contrast, some other studies of schizophrenia patients have found smaller than normal N400 amplitudes to target stimuli related to preceding prime stimuli, and increased N400 semantic priming effects (Mathalon et al, 2002;Kreher et al, 2008;Salisbury, 2008;Kreher et al, 2009). Importantly, this pattern appears specific to short prime-target stimulus-onset asynchronies (SOAs) of less than approximately 300 ms, and patients with disorganized speech; and is thus thought to reflect an excess of rapid spread of activation in the semantic network of disorganized patients in particular (Ditman and Kuperberg, 2007;Salisbury, 2008;Kreher et al, 2009).…”

“…Importantly, this pattern appears specific to short prime-target stimulus-onset asynchronies (SOAs) of less than approximately 300 ms, and patients with disorganized speech; and is thus thought to reflect an excess of rapid spread of activation in the semantic network of disorganized patients in particular (Ditman and Kuperberg, 2007;Salisbury, 2008;Kreher et al, 2009). Thus, this "hyperpriming" is not necessarily mutually exclusive with the presence of semantic priming deficits over longer time intervals in schizophrenia patients more generally.…”

Electrophysiological correlates of automatic spreading of activation in patients with psychotic disorder and first-degree relatives

“…Increased N400 semantic priming effects have been reported in patients with psychotic disorder, with abnormally small N400 amplitudes to directly associated words (compared to the unrelated condition) in patients with non-FTD (Mathalon et al, 2002(Mathalon et al, , 2010, and indirectly related words in patients with FTD (Kreher et al, 2010(Kreher et al, , 2008) at short SOA, indicative of a broader spreading of activation in the semantic network. In contrast, abnormally reduced N400 semantic priming effects have also been found in patients with psychotic disorder, with larger N400 amplitudes for the direct and indirect associative conditions (indicating no difference between the associatively/indirectly related and the unrelated N400 amplitude) at short and long SOA (Condray et al, 2003;Kiang et al, 2008).…”